civil engineering bridge engineering - bridge design manual.pdf

Washington State Department of Transportation

BridgeDesignManual M 23-50

Washington State Department of Transportation

BridgeDesignManualM 23-50

Chapters 1-7

Program Development DivisionBridge and Structures

Engineering Publications Washington State Department of Transportation PO Box 47408 Olympia, WA 98504-7408 E-mail: [email protected] Phone: (360) 705-7430 Fax: (360) 705-6861 http://www.wsdot.wa.gov/fasc/EngineeringPublications/

Persons with disabilities may request this information be prepared and supplied in alternate forms by calling the WSDOT ADA Accommodation Hotline collect

(206) 389-2839. Persons with hearing impairments may access WA State Telecommunications Relay Service at TT 1-800-833-6388, Tele-Braille 1-800-833-6385,

or Voice 1-800-833-6384, and ask to be connected to (360) 705-7097.

Foreword

This manual has been prepared to provide Washington State Department of Transportation (WSDOT) bridgedesign engineers with a guide to the design criteria, analysis methods, and detailing procedures for the preparationof highway bridge and structure construction plans, specifications, and estimates.

It is not intended to be a textbook on structural engineering. It is a guide to acceptable WSDOT practice. Thismanual does not cover all conceivable problems that may arise, but is intended to be sufficiently comprehensive to,along with sound engineering judgment, provide a safe guide for bridge engineering.

A thorough knowledge of the contents of this manual is essential for a high degree of efficiency in the engineeringof WSDOT highway structures.

This loose leaf form of this manual facilitates modifications and additions. New provisions and revisions will beissued from time to time to keep this guide current. Suggestions for improvement and updating the manual arealways welcome.

All manual modifications must be approved by the Bridge Design Engineer.

__________________________________________M. MYINT LWINBridge and Structures EngineerWashington State Department of Transportation

V:BDM1

September 1993

BRIDGE DESIGN MANUALCriteria

General Information Contents

Page

1.1 Manual Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

1.1.1 Purpose . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

1.1.2 Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

1.1.3 Format . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1A. General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1B. Chapters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2C. Numbering System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

1.1.4 Revisions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3A. Manual Updates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3B. Bridge Design Instruction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3C. Record of Manual Revisions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

1.2 Bridge and Structures Office Organization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.2-1

1.2.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

1.2.2 Organizational Elements of the Office . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1A. Bridge and Structures Engineer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1B. Bridge Design Engineer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1C. Bridge Preservation Engineer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2D. Bridge Management Engineer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3E. Computer Applications Engineer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3F. Consultant Coordinator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3G. Architect . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3H. Staff Support Unit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3I. Office Administrator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

1.3 Design Procedures and Processes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.3-1

1.3.1 Design/Check Procedures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1A. WSDOT PS&E . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1B. Consultant PS&E — Projects on WSDOT Right of Way . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5C. Consultant PS&E — On County and City Right of Way Projects . . . . . . . . . . . . . . . . . . . . . . 6

1.3.2 Design/Check Calculation File . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7A. File of Calculations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7B. Procedures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7C. To Be Included . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7D. Not to Be Included . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8E. Upon Completion of the Design Work, Fill Out a Design Completion Checklist . . . . . . . . . . 8

1.3.3 Office Copy Review . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

1.3.4 Addenda . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

1.3.5 Shop Plans . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9A. Bridge Shop Plans . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9B. Sign Structure, Signal, and Illumination Shop Plans . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

1.3.6 Contract Plan Changes (Change Orders and As-Builts) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11A. Request for Changes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11B. Processing Contract Revisions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

1.4 Coordination With Other Divisions and Agencies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.4-1

1.4.1 Preliminary Planning Phase . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

August 1998 1.0-i


General Information Contents

1.4.2 Final Design Phase . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1A. Coordination With Region . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1B. Technical Design Matters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

1.5 Bridge Design Scheduling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.5-1

1.5.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

1.5.2 Preliminary Design Schedule . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

1.5.3 Final Design Schedule . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1A. Breakdown of Project Man-Hours Required . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1B. Estimate Design Time Required . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2C. Monthly Project Progress Report . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

1.6 Guidelines for Bridge Site Visits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.6-1

1.6.1 Bridge Rehabilitation Projects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

1.6.2 Bridge Widenings and Seismic Retrofits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

1.6.3 Rail and Minor Expansion Joint Retrofits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

1.6.4 New Bridges . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

1.6.5 Bridge Demolition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

1.99 Bibliography . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.99-1

Appendix A — Design Aids

1.3-A1 Standard Design Criteria Form1.3-A2 Exceptions to the Standard Design Criteria Form

1.3-A3 Design Completed Checklist

1.3-A4 Job File Table of Contents1.3-A5 Office Time Report

1.3-A6 Not Included in Bridge Quantities List

1.3-A7 Special Provisions Checklist1.5-A1 Breakdown of Project Manhours Required Form

1.5-A2 Monthly Project Progress Report Form

P:DP/BDM19807-0802

1.0-ii August 1998


Structural Steel Manual Description

1.1 Manual Description

1.1.1 Purpose

This manual is intended to be a guide for Bridge Designers and others involved with bridge design forthe Washington State Department of Transportation (WSDOT). It contains design details and methodsthat have been standardized and it interprets the intent of specifications. It is not intended to govern designin unusual situations nor to unduly inhibit the designer in the exercise of engineering judgment. There isno substitute for good judgment. The following axioms are given as a reminder that simple things makea big difference.

1. Gravity always works — if something is not supported, it will fall.

2. A chain reaction will cause small failures to become big failures, unless alternate load paths areavailable in the structure (i.e., progressive collapse).

3. Small errors, such as a drafting error or a misplaced decimal, can cause large failures.

4. Vigilance is needed to avoid small errors. This applies to construction inspection as well as in thedesign phase.

5. A construction job should be run by one person with authority, not a committee. It has been said thata camel is a horse designed and built by a committee.

6. High quality craftsmanship must be provided by everyone.

7. An unbuildable design is not buildable. An obvious fact often overlooked by the architect orstructural designer. Think about how forms will be built, then removed if necessary.

8. There is no foolproof design.

9. The best way to ensure a failure is to disregard or ignore lessons from past failures.

10. Many problems can be avoided by using a little loving care.

1.1.2 Specifications

The AASHTO publications Standard Specifications for Highway Bridges and LRFD Bridge DesignSpecifications are the basic documents guiding the design of highway bridges and structures. ThisWSDOT Bridge Design Manual is intended to supplement AASHTO and other specifications by provid-ing additional direction, design aids, examples, and information on office practices. Where conflicts existbetween this manual and the AASHTO Standard Specifications, this manual will control. When a conflictexists that is not resolved within the manual, further guidance shall be obtained from the Bridge DesignEngineer or his representative.

The AASHTO publications are not duplicated in this manual. Appropriate specifications and otherreferences are listed in Section 1.99.

1.1.3 Format

A. General

The Bridge Design Manual consists of two volumes with each chapter organized as follows:

Criteria or other information

Appendix A (printed on yellow paper) Design Aids

Appendix B (printed on salmon paper) Design Examples

August 1998 1.1-1



B. Chapters

1. General Information

2. Preliminary Design

3. Analysis

4. Loads

5. Reinforced Concrete Superstructures

6. Prestressed Concrete Superstructures

7. Structural Steel

8. Miscellaneous Design

9. Substructure Design

10. Detailing Practice

11. Quantities

12. Construction Costs

13. Construction Specifications

14. Inspection and Rating

C. Numbering System

1. The numbering system for the criteria consists of a set of numbers followed by letters as requiredto designate individual subjects. This format is similar to that used by AASHTO.

Example:

5.0 Reinforced Concrete Superstructures (Chapter)

5.4 Box Girder Bridges (Section)

5.4.2 Girder (Subsection)

C. Shear Resistance

1. The Shear Diagram

a. Shear Reinforcement

(1) Placement

2. Numbering of Sheets

Each section starts a new page numbering sequence. The page numbers are located in the loweroutside corners and begin with the chapter number, followed by the section number, then asequential page number.

Example: 5.4-1, 5.4-2, etc.

1.1-2 August 1998



3. Appendices are included to provide the designer with design aids (Appendix A) and examples(Appendix B). Design aids are generally standard in nature, whereas examples are modified tomeet specific job requirements.

An appendix is numbered using the chapter followed by section number and then a hyphen andthe letter of the appendix followed by consecutive numbers.

Example: 5.4-A1 (Box Girder Bridges) designates a design aid required or useful to accomplishthe work described in Chapter 5, Section 4.

4. Numbering of Tables and Figures

Tables and figures shall be numbered using the chapter, section, subsection in which they arelocated, and then a hyphen followed by consecutive numbers.

Example: Figure 5.4.2-1 is the first figure found in Chapter 5, section 4, subsection 2.

1.1.4 Revisions

A. Manual Updates

The Bridge Design Manual will change as new material is added and as criteria and specificationschange.

Revisions and new material will be issued with a Publications Transmittal Form. The form will havea revision number and remarks or special instructions regarding the sheets. The revision number shallbe entered on the Record of Revision sheet in this manual. This allows the user to verify that themanual is up to date.

B. Bridge Design Instruction

Special instructions regarding interpretation of criteria or other policy statements may be issued usinga Bridge Design Instruction (BDI). The BDI will be transmitted in the same manner as outlined abovefor manual revisions. The BDI should be inserted in the appropriate place in the manual and remainsin effect until the expiration date shown or until superseded by a revision to the manual. A sampleBDI is shown on Figure 1.1.4-1.

P:DP/BDM19807-0802

August 1998 1.1-3



February 1997

BRIDGE DESIGN INSTRUCTION 5.1.1 CHAPTER 5

SUBJECT: Use of Concrete Class 5000 and Class 4000D

ACTION: Place this instruction in your manual and note the instruction number in yourRecord of Manual Revisions, 1.1.4.

TEXT There is confusion regarding the availability of Concrete Class 5000. Thisclass of concrete is available within a 30-mile radius of Seattle, Spokane andVancouver, Washington. “Available” means that there are concrete suppliersin these urban areas capable of supplying Concrete Class 5000 in accordancewith WSDOT specifications. Outside this 30-mile radius (or near the fringe),the concrete suppliers generally do not have the quality control proceduresand expertise to supply this higher strength concrete. The Construction Officeor Materials Lab should be contacted for availability for project sites outsidethese areas.

In general, Class 4000D Concrete would be specified for bridge roadway decksoutside this 30 mile radius. Class 4000D Concrete specifications require a14-day wet cure and flyash as an additive. Typically, Class 4000 Concrete wouldbe specified for other bridge concrete members above ground. This mix wasdeveloped by the Materials Lab to be at least as durable as Class 5000 Concrete.

By utilizing the above guidelines, WSDOT will receive the most durable bridgedeck at the least cost.

Approved: _________________________C. C. RuthBridge Design Engineer

CCR/dbRTS

Figure 1.1.4-1

1.1-4 August 1998



C. Record of Manual Revisions

In order that a ready means be available to check whether a manual is up to date, each manual holderis requested to keep his copy up to date and to record Bridge Design Instructions or Revisions asmaterial is added or changed. The form below is intended for use in keeping this record. At any time,a manual holder will be able to check his list with the list in the “master” manual.

Revision Entry By Revision Entry By Revision Entry ByNumber Date (Initial) Number Date (Initial) Number Date (Initial)

August 1998 1.1-5


General Information Bridge and Structures Office Organization

1.2 Bridge and Structures Office Organization

1.2.1 General

The document defining the responsibilities for bridge design within the Washington State Department ofTransportation (WSDOT) is the Organization Handbook. In that document, the responsibilities of theBridge and Structures Office are stated as follows:

Provides structural engineering services for the department. Provides technical advice and assistanceto other governmental agencies on such matters.

The WSDOT Design Manual states the following:

Bridge design is the responsibility of the Bridge and Structures Office in Olympia. Any designauthorized to be performed at the regional level is subject to review and approval by the Bridgeand Structures Office.

1.2.2 Organizational Elements of the Office

A. Bridge and Structures Engineer

Responsible for structural engineering services for the department. Manages staff and programs forstructure design, contract plan preparation, and inspections and assessments of existing bridges.

B. Bridge Design Engineer

The Bridge Design Engineer is directly responsible to the Bridge and Structures Engineer forstructural design and review, and advises other divisions and agencies on such matters.

1. Structural Design Units

The Structural Design Units are responsible for the final design of bridges and other structures.Final design includes preparation of plans. The units provide special design studies, developdesign criteria, check shop plans, and review designs submitted by consultants.

Each design unit normally consists of individuals including a section supervisor and a bridgespecialist. Organization and job assignments within the unit are flexible and are related to theprojects underway at any particular time as well as to the qualifications of individuals. Theemphasis in the design sections is on providing sound designs, checking, reviewing, anddetailing in an efficient manner.

A bridge specialist is assigned to each design unit. Each specialist has a particular area ofresponsibility. The three areas are concrete, steel, and expansion joints and bearings. Thespecialist acts as a resource person for the bridge office in his specialty and is responsible forkeeping up-to-date on current AASHTO criteria, new design concepts, technical publications,construction and maintenance issues.

The design units are also responsible for the design and preparation of contract plans formodifications to bridges in service. These include bridge rail replacement, deck repair, seismicretrofits, emergency repairs when bridges are damaged by vehicle or ship collision or naturalphenomenon, and expansion joint and drainage retrofit. They review proposed plans of utilityattachments to existing bridges.

August 1998 1.2-1



2. Bridge Projects Unit

The Bridge Projects Engineer directs preliminary design work, specification and cost estimatespreparation, falsework review, and coordinates scheduling of bridge design projects with theBridge Design Engineer and the Design Unit Supervisors.

The Preliminary Design engineers are responsible for bridge project planning from design studiesto preliminary project reports. They are responsible for preliminary plan preparation of bridgeand walls including assembly and analysis of site data, preliminary structural analysis, costanalysis, determination of structure type, and drawing preparation. They also review highwayproject environmental documents and design reports and handle Coast Guard liaison duties.

The Specifications and Estimate (S&E) engineers develop and maintain constructionspecifications and cost estimates for bridge projects originating in the Bridge and StructuresOffice. They also review the specifications and cost estimates for bridge contracts prepared byconsultants and other government agencies which are administered by WSDOT. They assembleand review the completed bridge PS&E before submittal to the Plans Branch. They also coordi-nate the PS&E preparation with the regions, Plans Branch, and maintain bridge constructioncost records.

The Construction Support engineers are responsible for checking the contractor’s falsework,shoring, and form plans. Shop plans review and approval are coordinated with the designsections. Actual check of the shop plan is done in the design section. Field requests for planchanges come through this office for a recommendation as to approval. As built plans areprepared by this unit at the completion of a contract.

The Scheduling Engineer monitors the design work schedule for the Bridge and Structures Officeand maintains records of bridge contract costs.

In addition, the unit is responsible for the Bridge Design Manual, design standards, professionalactivities, and AASHTO support.

C. Bridge Preservation Engineer

Directs activities and develops programs to assure the structural and functional integrity of all statebridges in service. Directs emergency response services when bridges are damaged.

1. Bridge Preservation Unit

The Bridge Preservation Unit is responsible for planning and implementation of an inspectionprogram for the more than 3,000 fixed and movable state highway bridges. In addition, the unitprovides inspection services on some local agency bridges and on the state’s 21 ferry terminals.All inspections are conducted in accordance with the National Bridge Inspection Standards(NBIS).

The unit maintains a statewide computer inventory Washington State Bridge Inventory System(WSBIS), of current information on more than 7,300 state, county, and city bridges in accordancewith the NBIS. This includes load ratings for all bridges. It prepares a Bridge List of the state’sbridges which is published every two years.

The unit is responsible for the bridge load rating and risk reduction (SCOUR) programs. Itprovides damage assessments and emergency response services when bridges are damaged orlost due to vehicle or ship collision or natural phenomenon such as floods, wind, or earthquakes.

1.2-2 August 1998



D. Bridge Management Engineer

This Bridge Management Unit is responsible for program development, planning, and monitoring ofall H-Program activities. These include HBRRP funded bridge replacements and rehabilitation, bridgedeck protection, major bridge repair, and bridge painting.

In addition, this unit manages the bridge deck protection program including the deck testing programand the bridge research program. It is responsible for the planning, development, coordination, andimplementation of new programs (e.g., Seismic Retrofit and Preventative Maintenance), experimentalfeature projects, new product evaluation, and technology transfer.

E. Computer Applications Engineer

The Computer Support Unit is responsible for computer resource planning and implementation,computer user support, liaison with Management Information Systems (MIS), and computer aidedengineer operation support. In addition, the unit is responsible for Standard Plan updates.

F. Consultant Coordinator

The Consultant Coordinator prepares bridge consultant agreements and coordinates consultant PS&Edevelopment activities with those of the department.

G. Architect

The Principal Architect is responsible for approving preliminary plans, preparing renderings, modelmaking, and other duties to improve the aesthetics of our bridges and other structures. The PrincipalArchitect works closely with staff and regions. During the design phase, designers should get theArchitect’s approval for any changes to architectural details shown on the approved preliminary plan.

H. Staff Support Unit

The Staff Support Unit is responsible for many support functions, such as: typing, timekeeping,payroll, receptionist, vehicle management, mail, inventory management, and other duties requestedby the Bridge and Structures Engineer. Other duties include: of field data, plans for bridges undercontract or constructed, and design calculations. This unit also maintains office supplies and providesother services.

I. Office Administrator

The Office Administrator is responsible for coordinating personnel actions, updating theorganizational chart, ordering technical materials, and other duties requested by the Bridgeand Structures Engineer. Staff development and training are coordinated through the OfficeAdministrator. Logistical support, office and building maintenance issues are also handled bythe Office Administrator.

July 2000 1.2-3



1.2.3 Design Unit Responsibilities and Expertise

The following is an updated summary of design responsibilities/expertise within the Bridge DesignSection. Contact the unit manager for the name of the appropriate staff expert for the needed specialty.

Unit Manager Responsibility/Expertise

K. N. Kirker Expansion Joint ModificationsRetaining Walls (including MSE, Tie-Back, and Soil Nail)Seismic Retrofit

Y. A. Mhatre Noise WallsBridge Traffic BarriersStandard Plans for Prestressed Concrete

R. T. Shaefer Coast Guard PermitsCost EstimatesStandard Plans (other than Prestressed Concrete)Bridge Design Manual

J. A. VanLund Sign Supports, Light Standards, Traffic Signal SupportsRepairs to Damaged Prestressed Girder Bridges

P. T. Clarke Floating BridgesSpecial Structures

P65:DP/BDM1

1.2-4 July 2000


General Information Design Procedures and Processes

July 2000 1.3-1

1.3 Quality Control/Quality Assurance (QC/QA) Process for WSDOT Bridge Designs

1.3.0 General

A. The QA/QC process for bridge designs is a critical element of quality structure plan preparation.The overall goals of the structural design process are:

• The structural design maximizes the safety of the traveling public and is in accordance withState Law.

• The structural design is in accordance with the WSDOT Bridge Design Manual, AASHTOBridge Design Specifications, good structural engineering practice, and geometric criteriaprovided by the Region.

• Designed structures are durable, low-maintenance, and inspectable.

• The structural design facilitates constructibility and minimizes overall construction costs, whileexhibiting a pleasing architectural style.

• The structural design contract documents are produced in accordance with customer’s needs(schedule, construction staging, and available program funding).

• Structural design costs are minimized.

• A well-organized and readable structure calculation record is produced.

• Plan quality is maximized.

• Design process allows for change, innovation, and continuous improvement.

The overall goals are listed in order of importance. If there is a conflict between goals, the moreimportant goal takes precedence.

The design unit manager determines project assignments and the QC/QA process to be used inpreparation of the structural design. The intent of the QC/QA process is to facilitate productionefficiency and cost-effectiveness while assuring the structural integrity of the design and maximizingthe quality of the structure contract documents.

1.3.1 Design/Check Procedures

A. PS&E Prepared by WSDOT Bridge and Structures Office

1. Design Team

The design team, consisting of the Designer(s), Checker(s), Structural Detailer(s), and Specifica-tion and Estimate engineer are responsible for preparing a set of contractible, clear, and concisestructural contract documents by the scheduled date and within the workforce hours allotted forthe project. On large projects, the design unit manager may assign a designer additional dutiesas a Design Team Leader to assist the manager in planning, coordinating, and monitoring theactivities of the design team. In this case, the team leader would also coordinate with the Regionand the Geotechnical Branch.

The QC/QA process will likely vary depending on the type and complexity of the structure beingdesigned, and the experience level of the design team members. More supervision, review, andchecking are required when the design team members are less experienced. In general, it is goodQC/QA practice to have some experienced members on each design team. All design teammembers should have the opportunity to provide input for maximizing the quality of the designbeing produced.



1.3-2 July 2000

2. Designer Responsibility

The designer is responsible for the structural analysis, completeness, correctness, and qualityof the plans. The designer shall provide quality control in the process of plan preparation. Thatis, errors and omissions need to be caught and corrected before subsequent checking and reviewof plans. A good set of example plans to follow, representative of bridge type, is indispensablein this regard.

During the design phase of a project, the designer will need to communicate with otherstakeholders. This includes acquiring, finalizing or revising roadway geometrics, soil reports,hydraulics recommendations, and utility requirements. Constructibility issues may also requirethat the designer communicate with the Region or Construction Office. The bridge plans mustbe coordinated with the PS&E packages produced concurrently by the Region.

The designer or team leader is responsible for project planning which involves the following:

a. Prepare a Design Time Estimate Bar Chart (see Section 1.5.2).

b. Identify tasks and plan order of work.

c. Prepare design criteria, which should be included in the design calculations. Use StandardDesign Criteria Form, 1.3-A1-1 for routine projects. A project specific design criteria shouldbe made when appropriate. Compare tasks with BDM office practice and AASHTO bridgedesign specifications.

(1) Sufficient guidelines?

(2) Deviation from BDM/AASHTO?

(3) Any question on design approach?

(4) Deviation from office practices regarding design and details?

(5) Other differences.

d. Meet with the Region design staff and other project stakeholders early in the design processto resolve as many issues as possible before proceeding with final design and detailing.

e. Identify coordination needs with other designers, units, and offices.

f. Early in the project, determine the number and titles of sheets. For projects with multiplebridges, each set of bridge sheets should have a unique set of bridge sheet numbers.The bridge sheet numbering system should be coordinated with the Region design staff.

g. At least monthly or as directed by the design unit manager:

(1) Update Project Schedule and List of Sheets.

(2) Estimate percent complete.

(3) Estimate time to complete.

(4) Work with design unit manager to adjust resources, if necessary.

h. Develop preliminary quantities for 90 percent complete cost estimate.



July 2000 1.3-3

i. Near end of project:

(1) Keep track of sheets as they are completed.

(2) Develop quantities and special provisions checklists that are to be turned in withthe plans.

(3) Prepare Bar List.

(4) Enter information into the Bridge Design Record.

(5) Coordinate all final changes, including review comments from the checker, managers,specialists, the Region, and the Construction Office.

(6) Meet with Region design staff and other project stakeholders at the constructibilitymeeting to address final project coordination issues.

The designer shall advise and get the design unit manager’s approval whenever detailsdeviate from the BDM office practice and AASHTO Bridge Design Specifications. Thedesigner shall provide documentation of the structural design deviations in the calculations.

The designer should inform the design unit manager of any areas of the design which shouldreceive special attention during checking and review.

The design calculations are prepared by the designer and become a very important recorddocument. Design calculations will be a reference document during the construction of thestructure and throughout the life of the structure. It is critical that the design calculations beuser friendly. The design calculations shall be well organized, clear, properly referenced,and include numbered pages along with a table of contents. The design calculations shallbe archived. Computer files should be archived for use during construction, in the event thatchanged conditions arise. Archive-ready design and check calculations shall be bound andsubmitted to the design unit manager within 30 days of submitting the 100 percent PS&E.Calculations shall be stored in the design unit until completion of construction. Afterconstruction, they shall be sent to archives.

The designer is also responsible for resolving construction problems referred to the BridgeOffice during the life of the contract. These issues will generally be referred through theBridge Technical Advisor, the design unit manager, the Construction Support Unit, or theOSC Construction Unit.

3. Design Checker Responsibility

The checker is responsible to the design unit manager for “quality assurance” of the structuraldesign, which includes checking the design and plans to assure accuracy and constructibility.The design unit manager works with the checker to establish the level of checking. The checkingprocedure for assuring the quality of the design will vary from project to project. Following aresome general checking guidelines:

a. Design Calculations

(1) For designs checked by an experienced checker, a review and initialing of the designer’scalculations by the checker is acceptable. If it is more efficient, the checker may chooseto perform his/her own calculations to check. All the designer and checker calculationsshall be placed in one design calculation set.



1.3-4 July 2000

(2) For designs checked by an inexperienced checker, a more thorough check should beperformed by the checker to enhance his/her understanding of structural design. In thiscase, the design unit manager should provide the checker with a design example.

(3) Revision of design calculations, if required, is the responsibility of the designer.

b. Structural Plans

(1) The checker’s plan review comments are recorded on the structural plans, includingdetails and bar lists, and returned to the designer for consideration. If the checker’scomments are not incorporated, the designer should provide justification for not doingso. If there is a difference of opinion that cannot be resolved between the designer andchecker, the unit manager shall resolve the issue.

(2) If assigned by the design unit manager, the checker shall perform a complete check ofthe geometry using CADD, hand calculations, or a geometric program.

(3) Revision of plans, if required, is the responsibility of the designer.

4. Structural Detailer Responsibility

The structural detailer is responsible for the structural plan sheets. The plans shall be neat,correct, and easy to follow and drawn to scale. The structural detailer may also assist the designerand design checker in such areas as determining control dimensions and elevations, geometry,and calculating quantities.

Some detailing basics and principles:

a. Refer to BDM, Chapter 10, for detailing practices.

b. Provide necessary and adequate information. Try to avoid repetition of information.

c. Avoid placing too much information into any one sheet.

d. Plan sheets should detailed in a consistent manner and follow accepted detailing practices.

e. Provide clear and separate detail of structural geometrics. Use clear detailing such as “standalone” cross sections or a framing plan to define the structure.

f. Avoid reinforcing steel congestion.

g. Check reinforcement detail for consistency. Beware of common mistakes about placementof stirrups and ties (such as: stirrups too short, effect of skew neglected, epoxy coating notconsidered, etc.). Check splice location and detail, and welding locations.

h. Use cross references properly.

i. Use correct and consistent terminology. For example, the designation of Sections, Views,and Details.

j. Check for proper grammar and spelling.

k. On multiple bridge contracts, the structural detailing of all bridges within the contract shallbe coordinated to maximize consistency of detailing from bridge to bridge. Extra effortwill be required to assure uniformity of details, particularly if multiple design units and/orconsultants are involved in preparing bridge plans. This is a critical element of good qualitybridge plans.



July 2000 1.3-5

l. Refer to the Bridge Book of Knowledge for current special features and details used onother projects.

5. Specialist Responsibility

There are currently four specialist positions in the Bridge and Structures Office. There is aspecialist assigned to each of the three design sections and one to the Bridge PreservationSection. The primary responsibility of the specialist is to act as a knowledge resource for thisoffice. The Specialists maintain an active knowledge of their specialty area along with a currentfile of products and design procedures. Proactive industry contacts are maintained by the Special-ists. Specialists also provide training in their area of specialty. As contract plans are prepared byother designers, the Specialists are expected to review and initial drawings covered by theirspecialty area. Plans produced directly by Specialists in their specialty area should be preparedwith their own stamp and signature. Specialists also assist the Bridge Engineer in reviewing andvoting on amendments to AASHTO specifications. They also are responsible for keeping theirrespective chapters of the Bridge Design Manual up to date. The secondary responsibility of theSpecialist is to serve as design section supervisor when the supervisor is absent.

There are three specialty areas in the Design Section: Concrete, Expansion Joints and Bearings,and Steel.

6. Design Unit Technical Responsibilities

Each Design Unit is responsible for maintaining a resource of technical knowledge and leader-ship. As described in the previous Section (5.), each unit has a Design Specialist (Concrete, Steel,Expansion Joints and Bearings). In addition, each Design Unit maintains a resource of technicalknowledge in several technical areas. Following, is a list of all technical subjects for which aresource is maintained:

• Coast Guard Permits

• Cost Estimates

• Bridge Special Provisions

• Sign Supports, Light Standards, Traffic Signal Supports

• Repairs to Damaged Prestressed Girders

• Expansion Joint Modifications

• Retaining Walls (Including MSE, Tie-Back, and Soil Nail)

• Seismic Retrofit

• Noise Walls

• Traffic Barrier Retrofits/Standards

• Bridge Standard Plans (BDM)

The resource/leadership responsibility for these technical areas does not necessarily includeresponsibility for performing all of the work relating to the technical area. For many of thetechnical areas, the Design Unit acts as a resource for the technical area, only, and as a contactfor industry and stakeholders.



1.3-6 July 2000

7. Specification and Estimating Engineer Responsibilities

The S&E Engineer is responsible for compiling the PS&E package for bridge and/or relatedhighway structural components. This PS&E package includes Special Provisions (BSPs andGSPs as appropriate), construction cost estimate, construction working day schedule, test holeboring logs and other appendices as appropriate, and the design plan package.

The S&E Engineer begins work after the design unit submits copies of the 90 percent designplans. This normally occurs on or before the date specified in the Bridge Design Schedule.A set of quantities, a copy of the “Not Included in Bridge Quantities,” and a S&E Checklistare included in the PS&E package.

As a first order of business, the S&E Engineer distributes the 90 percent design plans for reviewby the Region and other offices. While other offices are reviewing the plan package, the S&EEngineer attends to the following duties.

• Review the job file, foundation report, and design plans to make sure that materials specifiedin the plans are consistent with the current Standard Specifications.

• Check the plans for engineering accuracy, completeness, and constructibility.

• Create a run list of BSPs, GSPs, and appropriate Standard Specification amendments.

• Compile a cost estimate file using the quantities submitted by the designers and current UnitCost figures for the various materials used in the bridge.

• The S&E Engineer develops a construction working day schedule which is also based on thequantities submitted by the designers.

At the same time, the S&E Engineer coordinates the Bridge and Structures Office review of theReview PS&E and responds with comments to the Region. The S&E Engineer also receives allRegion review comments and distributes them to the appropriate designer for action. The S&EEngineer also participates in the Region Review Roundtable Meeting. After the ReviewRoundtable Meeting, all comments are addressed by the designers.

The S&E Engineer has the following responsibilities during coordination of the Final BridgePS&E turn in.

• Make Special Provision reviews to the Bridge Special Provision word file.

• Inform the appropriate Region PS&E contact when the word file is complete and ready fortransfer.

• Complete Cost Estimate and Quantity revisions to the cost estimate files.

• Electronically distribute all cost estimate file revisions to the appropriate Region PS&Econtact.

Once the final Bridge Sheet mylars are printed, stamped, and signed, the S&E Engineer arrangesfor 11 by 17 paper prints for submittal to the appropriate Region PS&E contact. The originalstamped and signed mylars are turned in to the Construction Plans Unit for storage.

During the Advertising period many questions are funneled into the Bridge Office by the ProjectEngineers and the communications are generally distributed to the S&E Engineer. The S&EEngineer will ascertain the query, answer the question from the Contractors, or seek advice orhelp from the design engineer. The S&E Engineer will then respond back to the PE. Revisionsto the Plans or Specs are sometimes needed as a result of these questions from Contractors.



July 2000 1.3-7

Addendum’s are created to augment the original advertised document to make sure allContractors are advised prior to Bid Openings. These Addendum’s are coordinated with theRegion and OSC Plans.

The S&E Engineer attends the award meetings to justify bids and advise whether or not to awardthe contract.

Other responsibilities included are:

• Special Provisions and Estimates for Change Order Work

• Cost estimates in the scoping stage of a project

• Working Day information during Stage Construction planning

• Initiates/Coordinates Amendment and GSP Updates

• Maintains BSP Library

8. Design Unit Manager Responsibility

a. The design unit manager is responsible to the Bridge Design Engineer for the timelycompletion and quality of the bridge plans.

b. The design unit manager works closely with the design team (designer, checker, andstructural detailer) during the design and plan preparation phases to help avoid majorchanges late in the design process. Activities during the course of design include:

(1) Evaluate the complexity of the project and the designer’s skill and classification levelto deliver the project in a timely manner. Determine both the degree of supervisionnecessary for the designer and the amount of checking that will be required by thechecker.

(2) Assist the design team in defining the scope of the project, identifying the tasks to beaccomplished, developing a project work plan and schedule, and assigning resources toachieve delivery of the project.

(3) Review and approve design criteria before start of design.

(4) Help lead designer conduct face-to-face project meetings, such as: project “kick-off”and “wrap-up” meetings with Region, geotechnical staff, bridge construction, andconsultants to resolve outstanding issues.

(5) Assist the design team with planning, anticipating possible problems, collectivelyidentifying solutions, and facilitating timely delivery of needed information, such asgeometrics, hydraulics, foundation information, etc.

(6) Interact with design team regularly to discuss progress, problems, schedule, analysistechniques, constructibility and design issues. Always encourage forward thinking,innovative ideas and suggestions for quality improvement.

(7) Arrange for and provide the necessary resources and tools for the design team to do thejob right the first time. Offer assistance to help resolve questions or problems.

(8) Help document and disseminate information on special features and lessons learned forthe benefit of others and future projects.



1.3-8 July 2000

(9) Mentor and train designers and detailers on state-of-the-art practices and through theassignment of a variety of structure types.

c. The design unit manager works closely with the design team during the plan review phase.Review efforts should concentrate on reviewing the completed plan details and designcalculations for completeness and for agreement with office criteria and practices. Reviewthe following periodically and at the end of the project:

(1) Design Criteria

• Seismic “a” value

• Foundation report recommendations, selection of alternates

• Deviations from AASHTO, BDM, Documentation

(2) Design Time

d. Review designer’s estimated time to complete the project. Plan resource allocation tocomplete the project to meet the scheduled Ad Date. Monitor monthly time spent on theproject. Prepare and submit to the Bridge Projects Engineer monthly time reports for eachproject. Estimate time remaining to complete project, percent completed, and whetherproject is on or behind schedule. Arrange and plan resources to ensure a timely deliveryof the project within the estimated time to complete the project.

e. Advise Region of project scope and cost-creep. Use quarterly status reports to update Regionand Bridge Projects Engineer.

f. Use appropriate computer scheduling software or other means to monitor time usage and toallocate resources and to plan projects.

g. Fill out Office Time Report (see Appendix 1.3-A5).

h. Review of constructibility. Any problems unique to the project?

i. Check the final plans for the following:

(1) Scan the job file for unusual items relating to geometrics, hydraulics, geotechnical,environmental, etc.

(2) Overall check/review of sheet #1, the bridge layout for:

• Consistency — especially for multiple bridge project

• Missing information

(3) Check footing layout for conformance to Bridge Plan and for adequacy of informationgiven. Generally, the field personnel should be given enough information to “layout”the footings on the ground without referring to any other sheets. Details should be clear,precise, and dimensions tied to base reference such as survey line or defined center lineof bridge.

(4) Check the sequence of the plan sheets. They should adhere to the following order:layout, footing layout, substructures, superstructures, miscellaneous details, barriers,and bar list. Also check for appropriateness of the titles.



July 2000 1.3-9

(5) Check overall dimensions and elevations, spot check for compatibility. For example,check compatibility between superstructures and substructure. Also spot check barmarks.

(6) Use one’s training, common sense, and experience to “size-up” structural dimensionsand reinforcement, etc., for structural adequacy. When in doubt, prepare for a line ofquestioning to the designer/checker.

j. Stamp and seal the plans.

9. Bridge Design Engineer’s Responsibilities

The Bridge Design Engineer is the coach, mentor, and facilitator for the WSDOT QC/QA BridgeDesign Process. The leadership and support provided by this position is a major influence inassuring bridge design quality for structural designs performed by both WSDOT and consultants.The following summarizes the responsibilities of the Bridge Design Engineer relative to QC/QA:

a. When the structural contract plans are sealed by the Bridge Design Engineer, a structural/constructibility review of the plans is performed. This is a quality assurance (QA) functionas well as meeting the “responsible charge” requirements of the laws relating to ProfessionalEngineers.

b. Review and approve the Preliminary Bridge Plans. The primary focus for this responsibilityis to assure that the most cost-effective and appropriate structure type is selected for aparticular bridge site.

c. Participate in coordination, scheduling, and project-related discussions with stakeholders,customers, and outside agencies relating to major structural design issues.

d. Facilitate resolution of major project design issues.

e. Review unique project special provisions and major Standard Specification modificationsrelating to structures.

f. Facilitate partnerships between WSDOT, consultant, and construction industry stakeholdersto facilitate design quality.

g. Encourage designer creativity and innovation.

h. Exercise leadership and direction for maintaining a progressive and up to date Bridge DesignManual.

i. Create an open and supportive office environment in which Design Section staff are empow-ered to do high quality structural design work.

10. General Bridge Plan Signature Policy

The sealing and signature of bridge plans is an important element of the Bridge QC/QA process.It signifies review and responsible charge of the design and details represented in the plans. TheBridge and Structures Office intends to have at least one Licensed Structural Engineer seal andsign each contract plan sheet (except the bar list). For major projects, the Design Unit Managerand the Bridge Design Engineer will typically review, seal, and sign the bridge plans. For routinebridge designs and transportation structure designs, the Design Unit Manager (SE License) anddesigner with a Civil Engineer License will typically review, seal, and sign the contract plans(except the bar list).



1.3-10 July 2000

B. PS&E Prepared by Consultant

This section is yet to be developed, but it will include the following elements:

• Consultant Coordinator ResponsibilitiesScope of WorkNegotiate Contract (Task Assignments)Coordinate/Negotiate Changes to Scope of Work

• WSDOT Design Reviewer/Coordinator ResponsibilitiesReview consultant’s design criteria and standard details early in the projectIdentify resources needed to complete workEarly agreement on structural concepts/design method to be usedIdentify who is responsible for whatMonitor progressFacilitate communicationReview for design consistency with WSDOT practices and other bridge designs in projectResolve differencesAssure that consultant’s QC/QA plan was followed during design

• Design Unit Manager ResponsibilitiesEncourage/Facilitate communicationEarly involvement to assure that design concepts are appropriateEmpower Design Reviewer/CoordinatorFacilitate resolution of problems beyond ability of Reviewer/Coordinator

• S&E Unit ResponsibilitiesPrepare Specials and Estimate based on Consultant’s special provision checklist and quanti-tiesReview plans for consistencyForward Special Provisions and Estimate to consultant for review and comment

• Bridge Design Engineer ResponsibilitiesCursory review of design plansSignature approval of S&E bridge contract package

C. Consultant PS&E — On County and City Right of Way Projects

Consultants are frequently used by counties and cities to design bridges. The Highways and LocalPrograms Office determines which projects are to be reviewed by the Bridge and Structures Office.

Where a review is required, the PS&E is sent by Highways and Local Programs to the Bridge ProjectsEngineer for assignment. The Bridge and Structures Office Consultant Coordinator does not becomeinvolved.

A Review Engineer will be assigned to the project and will review the project as outlined forConsultant PS&E — Projects on WSDOT Right of Way (see Section 1.3.1.B).

The plans with the reviewers’ comments should be returned to the Bridge Projects Unit where thecomments will be transferred to a second set of plans which will be returned to Highways and LocalPrograms. The original set will be filed in the Bridge Projects Unit.



July 2000 1.3-11

Review is made of the Preliminary Plan first and the PS&E second. Comments are treated as advisory,although major structural problems must be corrected. An engineer from the county, city, or consultantmay contact the reviewer to discuss the comments.

1.3.2 Design/Check Calculation File

A. File of Calculations

The Bridge and Structures Office maintains a file of all pertinent design/check calculations fordocumentation and future reference.

B. Procedures

After an assigned project is completed and the bridge is built, the designer should turn in to themanager a bound file containing the design/check calculations.

C. File Inclusions

The following items should be included in the file:

1. Index Sheets

Number all calculation sheets and prepare an index by subject with the corresponding sheetnumbers.

List the name of the project, SR Number, designer/checker initials, date (month, day, and year),and supervisor’s initials.

2. Design Calculations

These should include design criteria, loadings, structural analysis, one set of moment and sheardiagrams and pertinent computer input and output data (reduced to 81

2 inch by 11 inch sheetsize).

3. Special Design Features

Brief narrative of major design decisions or revisions and the reasons for them.

4. Construction Problems or Revisions (As They Develop)

Not all construction problems can be anticipated during the design of the structure; therefore,construction problems arise that require revisions. Calculations for revisions made duringconstruction should be included in the design/check calculation file when construction iscompleted.

D. File Exclusions

The following items should not be included in the file:

1. Geometric calculations.

2. Irrelevant computer information.

3. Prints of Office Standard Sheets.

4. Irrelevant sketches.

5. Voided sheets.



1.3-12 July 2000

6. Preliminary design calculations and drawings unless used in the final design.

7. Test hole logs.

8. Quantity calculations.

E. Upon completion of the design work, fill out a Design Completed Checklist (Form 230-035).(See Appendix 1.3-A3.)

1.3.3 Office Copy Review

Office Copy is the compiled contract documents (plans/specials) of all involved disciplines (Region,service center, and Bridge Office). It is normally distributed for final review for compatibility,completeness, and accuracy before final printing and going to Ad with the contract.

a. Note the due date to determine priority.

b. Review the comments from any previous reviews of the Region PS&E and check to see if the itemshave been corrected.

c. Review all indexes for items related to traffic signals, illumination, signs, retaining walls, trafficbarrier, and other structural items.

d. Review the index and verify that no bridge plans have been omitted.

e. Review pertinent sections of the special provisions for consistency with the plans, design criteria,and specifications.

f. Verify that Standard Plans and preapproved plans are called out where applicable.

g. Review pertinent plan sheets.

h. Verify consistency between Region plans and bridge plans; particularly geometry, drainage,guardrail, and other pertinent items.

i. Determine if any nonstandard designs are shown or specified. If so, a structural review of them maybe necessary. Note any missing specifications, Standard Plans, etc.

j. Return plans and comments to the unit manager.

1.3.4 Addenda

Plan or specification revisions during the advertising period require an addendum. The Bridge ProjectsEngineer will evaluate the need for the addendum after consultation with the OSC Bridge ConstructionEngineer, Region, and the Plans Branch. The Bridge Design Engineer or the design unit manager mustinitial all addenda.

For addenda to contract plans, obtain the original drawing from the Bridge Project Unit. Use shading tomark all changes (except deletions) and place a revision note at the bottom of the sheet (Region and PlansBranch jointly determine addendum date) and a description of the change. Return the original and an11 × 17 reduced copy to the Bridge Project Unit who will submit the reduced copy to the Plans Branchfor processing. See Chapter 10, Section 10.1.1I, for additional information.

For changes to specifications, submit a copy of the page with the change to the Bridge S&E Unit forprocessing.



July 2000 1.3-13

1.3.5 Shop Plans

The following is intended to be a guide for checking shop plans.

A. Bridge Shop Plans

1. Mark one copy of each sheet with the following, near the title block, in red pencil or with arubber stamp:

Office CopyContract (number)(Checker’s initials) (Date)

2. On the Bridge Office copy, mark with red pencil any errors or corrections. Yellow shall beused for highlighting the checked items, and ordinary lead (gray) pencil for other comments,arithmetic, etc. (Only the red pencil marks will be copied onto the other copies to be returnedto the contractor.)

3. Items to be checked are typically as follows: Check against Contract Plans, Special Provisions,and Standard Specifications.

a. Material specifications (ASTM specifications, hardness, alloy and temper, etc.).

b. Size of member and fasteners.

c. Length dimensions if shown on the Contract Plans.

d. Finish (surface finish, galvanizing, anodizing, painting, etc.).

e. Weld size and type and welding procedure if required.

f. Strand or rebar placement, jacking procedure, stress calculations, elongations, etc.

g. Fabrication — reaming, drilling, and assembly procedures.

h. Adequacy of details.

i. Erection procedure.

The following items pertain only to post-tensioning shop plans:

j. Center of gravity of post-tensioning (P/T) strands matches contract plans.

k. Seating loss.

l. Friction losses.

m. Time-dependent losses.

n. Steel stress diagram.

o. Elongation of strands in all tendons. These will be compared with the field measurements.(See WSDOT Construction Manual.) For curved bridges where the lengths of the exteriorwebs vary by more than 2 percent, separate elongations should be provided for each web.

p. Anchor plate size. If nonstandard, check bearing stress on concrete and flexural stressin plate material. Test data must be on file to substantiate the adequacy of internal typeanchorages.



1.3-14 July 2000

q. Vent conduit at all high and low points in the spans.

r. Adequate room in the concrete members for the system.

s. Interference with other reinforcement. Special attention to this item if post-tensioning (P/T)supplier proposes a different number of tendons than shown on the plans.

t. Offsets from soffit to bottom of conduits. Watch for sharp curvature of tendons near endanchorages (see minimum radius requirements in Chapter 6 of BDM Criteria).

u. Strand positions in conduit in sag and summit tendon curves.

v. Stressing sequence.

w. Geometric details such as size of blockouts.

Note: Manufacturer’s details may vary slightly from contract plan requirements but must bestructurally adequate and reasonable.

4. Items Not Requiring Check:

a. Quantities in bill of materials.

b. Length dimensions not shown on Contract Plans except for spot checking.

5. Project Engineer’s Copy

If one copy has been marked by the Project Engineer (in green), do not use this as the officecopy. Transfer his corrections, if pertinent, to the office copy using red pencil.

6. Marking Copies

When finished, mark the office copy with one of three categories (in red pencil, lowerright corner).

a. APP’D

(Approved, No Corrections required.)

b. AAN

(Approved as noted — minor corrections only. Do not place written questions on anapproved as noted sheet.)

c. RFC

(Return for correction — major corrections are required followed by resubmittal.)

If in doubt between AAN and RFC, check with the unit manager. An acceptable detail maybe shown in red. Mark the plans Approved-As-Noted provided that the detail is clearly notedSuggested Correction — Otherwise Revise and Resubmit.

Do not mark the other copies. This will be done in the Construction Support Unit. The reviewermay be asked to proof the other copies after they have been marked.

Notify Project Engineer of any approved changes to the contract plans. Also notify the OSCBridge Construction Engineer, who may have to approve a change order and provide justificationfor the change order.



July 2000 1.3-15

If problems are encountered which may cause a delay in the checking of the shop plans orcompletion of the contract, notify the unit manager and the Construction Support Unit.

Return all shop drawings and Contract Plans to the Construction Support unit when checking iscompleted. Include a list of any deviations from the Contract Plans which are allowed and a listof any disagreements with the Project Engineer’s comments (regardless of how minor they maybe). If deviations from the Contract Plans are to be allowed, a Change Order may be required.Alert the Construction Support Unit so that their transmittal letter may inform the Region andthe OSC Bridge Construction Engineer.

B. Sign Structure, Signal, and Illumination Shop Plans

In addition to those instructions described under “Bridge Shop Plans,” the following instructionsapply:

1. Review the shop plans to ensure that the pole sizes conform to the Contract Plans. Determine iffabricator has supplied plans for each pole or type of pole called for in the contract.

2. The Project Engineer’s copy may show shaft lengths where not shown on Contract Plans orwhether a change from Contract Plans is required. Manufacturer’s details may vary slightlyfrom contract plan requirements, but must be structurally adequate to be acceptable.

1.3.6 Contract Plan Changes (Change Orders and As-Builts)

A. Request for Changes

The following is intended as a guide for processing changes to the design plans after a project hasbeen awarded.

For projects which have been assigned a Bridge Technical Advisor, structural design change orderscan be approved at the Regional level provided the instructions outlined in the Construction Manualare followed.

For all other projects, all changes are to be channeled through the Construction Support Unit whichwill coordinate with the OSC Bridge Construction Engineer. Responses to inquiries should behandled as follows:

1. Request by Contractor or Supplier

A designer, BTA, or design unit manager contacted directly by a contractor/supplier may discussa proposed change with the contractor/supplier, but shall clearly tell the contractor/supplier toformally submit the proposed change though the Project Engineer and that the discussion in noway implies approval of the proposed change. Designers are to inform their manager if they arecontacted.

2. Request From the Project Engineer

Requests for changes directly from the Project Engineer to the design unit manager should bediscouraged but may be acceptable when the Bridge Construction Engineer is not available. TheBridge Construction Engineer and Construction Support Unit should be informed of any changes.

3. Request From the Region Construction Engineer

Requests from the Region Construction Engineer are to be handled like requests from the RegionProject Engineer.



1.3-16 July 2000

4. Request From the OSC Bridge Construction Engineer

Requests for changes from the OSC Bridge Construction Engineer or his/her assistants areusually made through the Construction Support Unit and not directly to the Design Unit.However, sometimes, it is necessary to work directly with the Design Unit. The ConstructionSupport Unit should be informed of any decisions made involving changes to the Contract Plans.

5. Request From the Design Unit

Request for changes from the Design Unit due to plan error, omissions, etc., shall be discussedwith the Bridge Design Engineer prior to revising and issuing new plan sheets.

B. Processing Contract Revisions

Changes to the Contract Plans or Specifications subsequent to the award of the contract may requirea contract revision. To clearly identify the scope of work, it is often desirable to provide revised oradditional drawings. When a revision or an additional drawing is necessary, request the originalmylars from the Construction Support Unit’s Plans Technician and prepare revised or new originalmylars.

Send the new mylars to the Construction Support Unit’s Plans Technician. The OSC ConstructionOffice requires two reduced paper copies; Construction Support Unit requires one reduced papercopy; Design Unit requires one or more reduced paper copies; one full-sized paper print, stamped“As Constructed Plans,” shall be sent to the Project Engineer who shall use it to mark constructionchanges and upon project completion, forward them to the Construction Support Bridge PlansTechnician. The Designer is responsible for making the prints and distributing them.

This process applies to all contracts including OSC Ad and Award, Region Ad and Award, or LocalAgency Ad and Award.

Whenever new plan sheets are required as part of a contract revision, the information in the titleblocks of these sheets must be identical to the title blocks of the contract they are for (e.g., JobNumber, Contract No., Fed. Aid Proj. No., Approved by, and the Project Name). These title blocksshall also be initialed by the Bridge Design Engineer, manager, designer, and reviewer of the changebefore they are distributed. If the changes are modifications made to an existing sheet, the sheetnumber will remain the same. A new sheet shall be assigned the same number as the one in theoriginals that it most closely applies to and shall also be given a letter (e.g., the new sheet applies tothe original sheet 25 of 53 so it will be number 25A of 53). A full size mylar of the contract revisionsheet shall be stored in the Bridge Projects Unit.

Every revision will be assigned a number which shall be enclosed inside a triangle (e.g., 1 ).The assigned number shall be located both at the location of the change on the sheet and in therevision block of the plan sheet along with an explanation of the change.

Any revised sheets shall be sent to the OSC Construction Office with a written explanation describingthe changes to the contract, justification for the changes, and a list of material quantity additionsor subtractions.



July 2000 1.3-17

1.3.7 Archiving Design Calculations, Design Files, and S&E Files

Upon Award, the following information will be collected by the Bridge Standard Plans Engineer.

• Design File

• S&E File

• Design Calculations

Place a job file cover sticker on the file folder (see Figure 1). Fill in all fields completely. Keep these fileson site for future reference until the end of the retention period. Update the file with any contract planchanges that occur during construction. After the retention period, send the files to the Office of theSecretary of State for archiving at:

Archives & Records Management1129 Washington Street SEOlympia, WA 98504-0238Telephone: 360-586-4900

SR # _____ County ____________________ CS # _____

Bridge Name _____________________________________

Bridge # _______________ Contract # ________________

Contents ________________________________________

Designed by _____________ Checked by _____________

Archive Box # _____________________ Vol. # _______

Figure 1

P65:DP/BDM1

August 1998 1.4-1


General Information Coordination With Other Divisions and Agencies

1.4 Coordination With Other Divisions and Agencies

During the various phases of design, it is necessary to coordinate the elements of the bridge designfunction with the requirements of other divisions and agencies. E-mail messages, telephone calls, andother direct communication with other offices are necessary and appropriate. Adequate communicationsare essential but organizational format and lines of responsibility must be recognized. However, a writtenrequest sent through channels is required before work can be done or design changes made on projects.

1.4.1 Preliminary Planning Phase

See Chapter 2.1 of this manual for coordination required at preliminary planning phase.

1.4.2 Final Design Phase

A. Coordination With Region

During this phase, final coordination of the bridge design with region requirements must beaccomplished. This is normally done with the Region Project Engineer, Region Design Engineer,or Region Plans Engineer. Details such as division of quantity items between the region PS&E andbridge PS&E become highly important to a finished contract plan set. The region PS&E and bridgePS&E are combined by the Region Plans Branch. However, necessary coordination should beaccomplished before this time.

During the design of a project for a region level contract, the region shall provide a copy of theproposed structural plans (such as retaining walls, barrier, large culverts, etc.) to the Bridge andStructures Office. Bridge and Structures Office will review these plans and indicate any requiredchanges, then send them back to the region.

The region shall incorporate the changes prior to contract advertisement.

After contract advertisement, the region shall return the original plan sheets to Bridge and StructuresOffice. These sheets shall be held in temporary storage until the “As Constructed Plans” for them arecompleted by the region.

The region shall then transmit the “As Constructed Plans” to Bridge and Structures Office wherethey will be transferred to the original plans for permanent storage. Upon request, the region will beprovided copies of these plans by Bridge and Structures Office.

B. Technical Design Matters

Technical coordination must be done with the OSC Materials Laboratory Foundation Engineer andwith the OSC Hydraulic Engineer for matters pertaining to their responsibilities. A portion of thecriteria for a project design may be derived from this coordination, otherwise it shall be developedby the designer subject to approval of the Bridge Design Engineer.

When two or more structures are to be let under the same contract, the designer should make a specialeffort to be uniform on structural details, bid items, specifications, and other items.

P:DP/BDM19807-0802


General Information Bridge Design Scheduling

1.5 Bridge Design Scheduling

1.5.1 General

The Bridge Projects Engineer is responsible for scheduling and monitoring the progress of projects.The “Bridge Design Schedule” is used to track the progress of a project and is updated monthly. A typicalproject would involve the following steps:

A. Regions advise Bridge and Structures Office of an upcoming project.

B. The Bridge Projects Unit estimates design time required for preliminary plans, design, and S&E(see Section 1.5.2).

C. The project is entered into the Bridge Design Schedule with start and due dates for site datapreliminary plan, project design, PS&E, and the ad date.

D. Bridge site data received.

E. Preliminary design started.

F. Final Design Started — Designer estimates time required for final plans (see Section 1.5.3).

G. Monthly Schedule Update — Each Design Unit Supervisor turns in to the Bridge SchedulingEngineer an updated copy of the Bridge Design Schedule showing man-months used last month,man-months used to date, percentage complete, and adjustments required in the schedule. The reportis due by the fourth working day of the month.

H. Project turned in to S&E unit.

1.5.2 Preliminary Design Schedule

The preliminary design estimate done by the Bridge Projects Unit is based on historical records frompast projects factoring in unique features of each individual project, the efficiencies of designing similarbridges on the same project, CADD system efficiencies, designer experience, and other factors asappropriate.

1.5.3 Final Design Schedule

A. Breakdown of Project Man-Hours Required

Using a spreadsheet, list each item of work required to complete the project and the man-hoursrequired to accomplish them. Certain items of work may have been partially completed during thepreliminary design, and this partial completion should be reflected in the columns “% Completed”and “Date Completed.” Formerly, WSDOT Form 232-002 (see Appendix 1.5-A1), was used tomonitor project progress. This form can still be used.

The designer or team leader should research several sources when making the final design timeestimate. The following are possible sources that may be used:

The “Bridge Design Summary” contains records of design time and costs for past projects. Thesummary is kept in the Bridge Projects Unit. The times given include preliminary plan, design,check, drafting, and supervision as reported on the summary from the Accounting Office.

The Bridge Projects Unit has “Bridge Construction Cost Summary” books. These are groupedaccording to bridge types and have records of design time, number of drawings, and bridge cost.The hours shown are the total for the bridge as reported from the designer’s time sheets.

August 1998 1.5-1



B. Estimate Design Time Required

The designer or design team leader shall determine an estimate of design time required to completethe project. The use of a spreadsheet, Microsoft Project, or other means is encouraged to ensuretimely completion and adherence to the schedule. In the past, WSDOT Form 232-003 was used.Typically, the following completion percentages (percent of the total project time) from Form232-002 are applied on Form 232-003 for the following activities:

Activity No. Percentage

1 402 203 254 55 57 5

Completion percentages for Activities 4, 5, and 7 are approximately 5 percent of the project total.

Activity 6 is separate from design time required by needs to be included to determine thecompletion date.

Activities 8 and 9 are estimates dependant on individual circumstances.

Note: Activities 1 through 5 and Activity 7 make up 100 percent of the design time required tocomplete the job.

The individual activities include the specific items as follows under each major activity.

Activity No. 1 Design — Includes:

1. Project coordination.

2. Geometric computations.

3. Design calculations (including time for Load Rating).

4. Complete check of all plan sheets by the designer.

5. Supervisor time related to design (estimate 10 percent of design time).

Activity No. 2 Design Check — As defined in Section 1.3.1A3 — Includes:

1. Checking design at maximum stress locations.

2. Checking major items on the drawings, including geometrics.

3. Additional checking required.

4. Supervisor time related to checking (estimate 10 percent of designcheck time).

1.5-2 August 1998



Activity No. 3 Drawings — Includes:

Preparation of all drawings.

Activity No. 4 Revisions — Includes:

1. Revisions resulting from the checker’s check.

2. Revisions resulting from the supervisory review.

Activity No. 5 Quantities — Includes:

1. Compute quantities including bar list.

2. Check quantities.

Activity No. 6 S&E — Includes:

1. Preparing special provisions checklist.

2. Assemble backup data covering any unusual feature.

Activity No. 7 Review — Includes:

1. Supervisor’s review.

Activity No. 8 Other Jobs — Includes:

1. Interruptions.

Activity No. 9 Leave — Includes:

1. Annual, sick, and other leave.

See Figures 1.5.2-1 and 2 for sample Bar Chart problem and corresponding progress report form.

C. Monthly Project Progress Report

The designer or design team leader is responsible for determining monthly project progress andreporting the results to the Unit Supervisor. In the past, WSDOT Form 232-004 (see Appendix1.5-A2) was used to monitor the progress of the project design. The Design Unit Supervisor isrequired to update a copy of the bridge design schedule each month using information from thedesigner or design team leader. Any discrepancies between actual progress and the project schedulemust be determined. Adjustments, either by revising the workforce assigned to the project, hoursassigned to activities or, the project schedule, should be made accordingly.

“Man-hours Used to Date” indicates the total number of hours used for each activity duringthe current period added to the total shown on the last report done.

“% of Total Time Used” is the number of hours used for the activity divided by the currentnumber of hours assigned to the activity from the “Current Estimate of Time to Complete”on Form 232-003.

“% of Activity Complete” and “% of Total Project Complete” are estimates. Some activitieswill probably be ahead of schedule, some behind, and others on schedule. It is here that majordiscrepancies should be noticed and adjustments made as described above.

August 1998 1.5-3



The designer may use a computer spreadsheet, to track the progress of the project and as an aid inevaluating the percent complete. Other tools include using an Excel spreadsheet listing bridge sheetplans by title, bridge sheet number, percent design complete, percent design check, percent plandetails completed, and percent plan details checked. A spreadsheet with this data allows the designeror design team leader to rapidly determine percent of project completion and where resources need tobe allocated to complete the project on schedule.

P:DP/BDM19807-0802

1.5-4 August 1998



Design Estimate Bar ChartSample Criteria

The designer estimates that 792 man-hours will be required to complete the design phase of the project.The hours are distributed among Activities 1 through 7 and entered in the first column of the Bar ChartForm. Enter the percentage amount in column three. Estimate the time for Activity 8 (approximately5 percent of subtotal) and for Activity 9 (approximately 8 percent of subtotal). Time from Activities 8and 9 will not enter into job manpower estimates, but will affect the estimated completion date. Using aconvenient scale, draw the bar chart.

To compute the “Anticipated Completion Date,” scale from the “zero-line” to the farthest block on theright and to this add Activities 8 and 9 (in effect extending the completion time). Multiply this number bythe scale you are using and divide by 8, and this will give you the number of working days to completiondate. The number of working days in conjunction with the Working Day Calendar (see Bridge ProjectsUnit) will give the completion date. For this example, this will be:

(5.5 + 1.2) × 100 × 1/8 = 84 working days

August 2, 1982 — Start Date = 6,475 (from working day calendar)Number of working days = +84

6,559 Dec. 2, 1982 (anticipated completion date)

Figure 1.5.2-1

August 1998 1.5-5

123456781234567812345678123456781234567812345678123456781234567812345678123456781234567812345678123456781234567812345678

Act

ivity

No.

Act

ivity

Orig

inal

Est

imat

eto

Com

ple

te(M

an H

ours

)

Cur

rent

Est

imat

eof

Tim

e to

Com

ple

te(M

an H

ours

)

Com

ple

tion

Per

cent

age

1

2

3

4

5

6

7

8

9

DesignCheck

Design

Drawings

Revisions

Quantities

S&E

Subtotals

Leave

Totals

100%

DOT 232-003 (formerly C1M4)Rev 3/91

Reviews

Other Jobs

Washington State Department of Transportation Design Time Bar Chart

Remarks

SR No.

Designed By

Job No. Project

Design Checked By Drawn By Design Start Date Scheduled Completion Date Anticipated Completion Date

Scale: 1" = __________ Man Hours

Layout By

Layout Check Bar Chart

Layout Man Hours



Sample Progress Report FormFigure 1.5.2-2

1.5-6 August 1998



1.6 Guidelines for Bridge Site Visits

The following guidelines are established to help all staff in determining the need for visiting bridge sitesprior to final design. These guidelines should apply to consultants as well as to our own staff. In all cases,the associated region should be made aware of the site visit so that they would have the opportunity toparticipate. Region participation would be especially useful if a preliminary bridge plan is involved.

1.6.1 Bridge Rehabilitation Projects (excluding rail and minor expansion joint rehabilitationprojects)

For this type of bridge project, it is critical that the design team know as much as possible about thebridge that is to be rehabilitated. There is good information regarding the condition of existing bridgesat the Bridge Preservation Office (Mottman). As-built drawings and contract documents are also helpful,but may not necessarily be accurate. At least one bridge site visit is necessary for this type of project. Insome cases, an in-depth inspection with experienced condition survey inspectors would be appropriate.The decision to perform an in-depth inspection should include the Unit Supervisor, Region, and theBridge Design Engineer.

1.6.2 Bridge Widenings and Seismic Retrofits

For this type of bridge project, it is important that the design team is familiar with the features andcondition of the existing bridge. There is good information regarding the condition of existing bridgesat the Bridge Preservation Office (Mottman). As-built drawings and contract documents are also helpful,but may not necessarily be accurate. A site visit is recommended for this type of project, particularly ifthe bridge to be widened has unique features or is other than a standard prestressed girder bridge withelastomeric bearings.

1.6.3 Rail and Minor Expansion Joint Retrofits

Generally, pictures and site information from the region along with as-builts and condition surveyinformation are adequate for most of these types of projects. However, if there is any doubt about theadequacy of the available information or concern about accelerated deterioration of the structureelements to be retrofitted, a site visit is recommended.

1.6.4 New Bridges

Generally, pictures and site information from the region are adequate for most new bridge designs.However, if the new bridge is a replacement for an existing bridge, a site visit is recommended,particularly if the project requires staged removal of the existing bridge and/or staged constructionof the new bridge.

1.6.5 Bridge Demolition

If a bridge demolition is required as part of a project, a site visit would help the design team determineif there are unique sit restrictions that could affect the demolition. If unique site restrictions are observed,they should be properly documented, included in the job file and noted on the special provisions checklist.

Before making a site visit, the Condition Survey Unit and the region should be contacted to determineif there are any unique site conditions or safety hazards. Proper safety equipment and procedures shouldalways be incorporated into any site visit. When making a site visit, it is important to obtain as muchinformation as possible. Pictures, video records with spoken commentary, field measurements, and fieldnotes are appropriate forms of field information. A written or pictorial record should be made of any

August 1998 1.6-1



observed problems with an existing bridge or obvious site problem. The site visit data would then beincorporated into the job file. This information will be a valuable asset in preparing constructable andcost-effective structural designs. When negotiating with consultants for structural design work, it isimportant to make appropriate site visits part of the consultants’s scope of work.

P:DP/BDM19807-0802

1.6-2 August 1998

August 1998 1.99-1


General Information Bibliography

1.99 Bibliography

1. Standard Specifications for Highway Bridges, Latest Edition and Interims, American Associationof State Highway and Transportation Officials (AASHTO).

2. LRFD Bridge Design Specifications, Latest Edition and Interims. American Association of StateHighway and Transportation Officials (AASHTO).

3. Organization Handbook, Washington State Department of Transportation.

4. WSDOT Design Manual.

5. WSDOT Construction Manual.

P:DP/BDM19807-0802

BRIDGE DESIGN MANUALAppendix A

General Information Standard Design Criteria Form

STANDARD SPECIFICATIONS FOR HIGHWAY BRIDGES AASHTO_________TH EDITION, 19___________

INTERIM SPECIFICATION, 19____________(IF USED)

STATE OF WASHINGTON, STANDARD SPECIFICATIONS FOR ROAD, BRIDGE, AND MUNICIPAL CONSTRUCTION, 19__________

STATE OF WASHINGTON, STANDARD PLANS FOR ROAD, BRIDGE, AND MUNICIPAL CONSTRUCTION WITH REVISIONS TO 19____________

BRIDGE DESIGN MANUAL, VOLUME_____________, WITH REVISIONS TO 19___________

OTHER_______________________________________________________________________________________________________

DESIGN BY: LOAD FACTOR____________________________________________________________________________________

WORKING STRESS________________________________________________________________________________

STEEL REINFORCING BARS:

A.A.S.H.T.O. M31 GRADE 60_______________

A.A.S.H.T.O. M31 GRADE 40______________

CONCRETE:

F'C = 4000 PSI (CLASS AX)

F'C = 3000 PSI (CLASS B)

F'C = _________ PSI (LIGHTWEIGHT) DENSITY = ________________ LBS. PER FT.

OTHER__________________________________________________________________________________________________

PRESTRESSED GIRDERS:SERIES, __________________________________ SPECIAL,_________________________________

STANDARD CONCRETE DENSITY = ___________________________ LBS. / FT.

LIGHTWEIGHT CONCRETE DENSITY = _______________________________LBS. / FT.

MINIMUM CONCRETE STRENGTH AT STRAND RELEASE = _______________________________PSI

MINIMUM CONCRETE STRENGTH AT 28 DAYS = ________________________________________PSI

FOUNDATION DATA FROM SOILS MAXIMUM DESIGN SOIL OR PILE LOADPIERNO. PILE/SPREAD ALLOWABLE SOIL DESIGNER GROUP CHECKER GROUPp

3

3

3

p

1

2

3

4

5

6

STANDARD DESIGN CRITERIA FOR THIS STRUCTUREITEM

PROJECT

SR MADE BY CHECKED BY DATE SUPV.

1

2

3

4

5

7

8

6

9

10

11

STANDARD DESIGN CRITERIA

August 1998 1.3-A1-1


General Information Standard Design Criteria Form

ITEM

STEEL STRUCTURES:

INDICATE BY SPECIFICATION THE DIFFERENT TYPES OF STEEL USE

SPECIAL CRITERIA:

SEE FORM ENTITLED “EXCEPTIONS TO THE STANDARD DESIGN CRITERIA“

12

13

STANDARD DESIGN CRITERIA FOR THIS STRUCTURE

ROLLERS

CASTINGS

A.A.S.H.T.O.

A.A.S.H.T.O.

A.A.S.H.T.O.

A.A.S.H.T.O.

A.A.S.H.T.O.

OTHER

M-

M-

M-

M-

M-

DOT 230-030Revised 1/89

1.3-A1-2 August 1998

August 1998 1.3-A2


General Information Exceptions to the Standard Design Criteria Form

EXCEPTIONS TO THE STANDARD DESIGN CRITERIA

No. Gen. Area Addition or Modification App’d By

Project SR No.

Made By SupervisorCheck By Date

DOT 230-032 (formerly C1M3)Rev 3/91

August 1998 1.3-A3


General Information Design Completed Checklist

August 1998 1.3-A4


General Information Job File Table of Contents

Job File Table of Contents

Item Date Who Subject

August 1998 1.3-A5


General Information Office Time Report

Bridge and Structures Office Time Report

_______________ Region L-Number ___________

PRELIMINARY PLAN: Design Unit Staffing Level estimate __________

Start Date: ____________________ Completion Date: _______________

TIME CHARGED

Design ____________ Hours Standard _______________Check ____________ HoursDrafting___________ HoursReview ___________ HoursTotal _____________ Hours

DESIGN AND DETAIL Design Unit Staffing Level estimate __________

Start Date: ____________________ Completion Date: _______________

TIME CHARGED

Design ____________ Hours Standard _______________Check ____________ HoursDrafting___________ HoursReview ___________ HoursTotal _____________ Hours

August 1998 1.3-A6


General Information Not Included in Bridge Quantities List

DOT Form 230-038 EFRevised 2/97

Not Included InBridge Quantities List

Environmental And Engineering Service CenterBridge and Structures Office

SR Job Number Project Title

Designed By Checked By Date Supervisor

Type of Structure

The following is a list of items for which the Bridge and Structures Office is relying on the Region to furnishplans, specifications and estimates.

1.

2.

3.

4.

5.

6.

7.

8.

9.

10.

11.

12.

13.

14.

15.

16.

17.


General Information Special Provisions Checklist

August 1998 1.3-A7-1



1.3-A7-2 August 1998



August 1998 1.3-A7-3



1.3-A7-4 August 1998



August 1998 1.3-A7-5



1.3-A7-6 August 1998

August 1998 1.5-A1


General Information Breakdown of Project Manhours Required Form

Desi

gnDr

awCh

eck

Chec

k Dr

awin

g

By

% Completed

Hours Required

Date Completed

By

% Completed

Hours Required

Date Completed

By

% Completed

Hours Required

Date Completed

By

% Completed

Hours Required

Date Completed

Com

men

tsDr

awin

g or

Item

No.

Brea

kdow

n of

Pro

ject

Man

hour

s Re

quire

d

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22D

OT

232-

002

(for

mer

ly C

1M5)

Rev

3/9

1

SRJo

b No

.Pr

ojec

tDa

teM

ade

By

Wash

ingto

n S

tate

D

epart

men

t of

Tra

nsp

ort

ati

on

August 1998 1.5-A2


General Information Monthly Project Progress Report Form

1234567890123456

1234567890123456

1234567890123456

1234567890123456

1234567890123456

1234567890123456

1234567890123456

1234567890123456

1234567890123456

1234567890123456

1234567890123456

1234567890123456

123456789

123456789

123456789

123456789

123456789

123456789

123456789

123456789

123456789

123456789

1234567890123456

1234567890123456

1234567890123456

1234567890123456

1234567890123456

1234567890123456

1234567890123456

1234567890123456

1234567890123456

1234567890123456

1234567890123456

1234567890123456

123456789

123456789

123456789

123456789

123456789

1234567890123456

1234567890123456

1234567890123456

1234567890123456

1234567890123456

1234567890123456

1234567890123456

1234567890123456

1234567890123456

1234567890123456

1234567890123456

1234567890123456

123456789

123456789

123456789

123456789

123456789

12345678901234567

12345678901234567

12345678901234567

12345678901234567

12345678901234567

12345678901234567

12345678901234567

12345678901234567

12345678901234567

12345678901234567

12345678901234567

12345678901234567

Refe

renc

e No

.

As o

f

Refe

renc

e No

.

As o

f

Refe

renc

e No

.

As o

f

Refe

renc

e No

.

As o

f Man HoursUsed to Date

% of TotalTime Used

% of ActivityComplete

% of TotalProject Complete

Man HoursUsed to Date

% of TotalTime Used




% of TotalTime Used




% of TotalTime Used



1 2 3 4 5 6 7 8 9Activity No.

Tota

ls

Mon

thly

Pro

ject

Pro

gres

s Re

port

Wash

ingto

n S

tate

D

epart

men

t of

Tra

nsp

ort

ati

on

DO

T 23

2-00

4 (f

orm

erly

C1M

4)R

ev 3

/91

SRJo

b No

.Pr

ojec

t

August 1998 2.0-i


Preliminary Design Contents

Page

2.0 Preliminary Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.1-1

2.1 Preliminary Studies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

2.1.1 Interdisciplinary Design Studies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

2.1.2 Value Engineering Studies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

2.1.3 Preliminary Project Recommendations (Existing Bridges) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

2.1.4 Preliminary Project Recommendations (New Bridges) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

2.1.5 Type, Size, and Location Studies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2A. TS&L General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2B. TS&L Outline . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3C. Reviews and Submittal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

2.2 Preliminary Plan . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.2-1

2.2.1 Development of the Preliminary Plan . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1A. Responsibilities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1B. Site Reconnaissance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1C. Coordination . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1D. Consideration of Alternatives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2E. Designer Recommendation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2F. Concept Approval . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2G. Inspection and Maintenance Access . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

2.2.2 Documentation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2A. Job File . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2B. Bridge Site Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2C. Request for Preliminary Foundation Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2D. Request for Preliminary Hydraulics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3E. Design Report or Design Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3F. Other Resources . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3G. Notes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

2.2.3 General Factors for Consideration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3A. Site Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3B. Safety . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3C. Economic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4D. Structural . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4E. Environmental . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4F. Aesthetic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4G. Construction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4H. Hydraulic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4I. Other . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

2.2.4 Permits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4A. Coast Guard . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4B. Other . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

2.2.5 Approvals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5A. Bridge Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5B. Bridge Architect . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5C. Region . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5D. Railroad . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

2.0-ii August 1998



Page

2.3 Preliminary Plan Criteria . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.3-1

2.3.1 Highway Crossings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1A. General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1B. Bridge Width . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1C. Horizontal Clearances . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1D. Vertical Clearances . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2E. End Slopes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2F. Determination of Bridge Length . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2G. Pedestrian Crossings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4H. Bridge Redundancy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

2.3.2 Railroad Crossings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4A. General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4B. Criteria . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4C. Bridge Width . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4D. Horizontal Clearances . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5E. Crash Walls . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5F. Vertical Clearances . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5G. Determination of Bridge Length . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5H. Special Considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

2.3.3 Water Crossings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6A. Bridge Width . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6B. Horizontal Clearances . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6C. Vertical Clearances . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6D. End Slopes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6E. Determination of Bridge Length . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6F. Scour . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7G. Pier Protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7H. Construction Access and Time Restrictions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

2.3.4 Bridge Widenings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8A. Bridge Width . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8B. Traffic Restrictions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8C. Construction Sequence . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

2.3.5 Detour Structures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8A. Bridge Width . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8B. Live Load . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

2.3.6 Retaining Walls and Noise Walls . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

2.3.7 Bridge Deck Drainage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

2.3.8 Bridge Deck Protective Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

2.3.9 Construction Clearances . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

2.3.10 Inspection and Maintenance Acces . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10A. General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10B. Safety Cables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11C. Travelers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

2.4 Selection of Structure Type . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.4-1

2.4.1 Bridge Types . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1A. Reinforced Concrete Flat Slab . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1B. Reinforced Concrete Tee Beam . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

August 1998 2.0-iii



Page

C. Reinforced Concrete Box Girder . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2D. Post Tensioned Concrete Box Girder . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2E. Prestressed Concrete Sections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3F. Composite Steel Plate Girder . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3G. Composite Steel Box Girder . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3H. Steel Truss . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4I. Segmental Concrete Box Girder . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4J. Railroad Bridges . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5K. Timber . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5L. Other . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

2.4.2 Wall Types . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

2.5 Aesthetic Considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.5-1

2.5.1 General Visual Impact . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

2.5.2 End Piers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1A. Wing Walls . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1B. Retaining Walls . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1C. Slope Protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

2.5.3 Intermediate Piers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

2.5.4 Barrier and Wall Surface Treatments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2A. Plain Surface Finish . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2B. Fractured Fin Finish . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2C. Pigmented Sealer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

2.5.5 Superstructure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

2.6 Miscellaneous . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.6-1

2.6.1 Structure Costs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

2.6.2 Handling and Shipping of Precast Members and Steel Beams . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

2.6.3 Salvage of Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

2.7 WSDOT Standard Highway Bridge . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.7-1

2.7.1 Design Elements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1A. General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1B. Substructure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1C. Superstructure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1D. Examples . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

2.99 Bibliography . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.99-1


2.2-A1 Bridge Site Data General2.2-A2 Bridge Site Data Rehabilitation

2.2-A3 Bridge Site Data Stream Crossings

2.2-A4 Preliminary Plan Checklist2.3-A1 Bridge Stage Construction Comparison

2.3-A2 Bridge Redundancy Criteria

2.4-A1 Bridge Selection Guide2.7-A1 Standard Superstructure Elements

2.7-A2 Standard Pier Elements

2.0-iv August 1998



Appendix B — Design Examples

2.2-B1 Preliminary Plan Bridge Replacement2.2-B2 Preliminary Plan Bridge Widening

2.2-B3 Preliminary Plan New Bridge

P:DP/BDM2

August 1998 2.1-1


Preliminary Design Preliminary Studies

2.0 Preliminary Design

2.1 Preliminary Studies

2.1.1 Interdisciplinary Design Studies

As part of the preparation for a major project, an Interdisciplinary Design Team (IDT) may be establishedby the region. The IDT is composed of members of different expertise and backgrounds, selected fromregions, the Service Center, and outside agencies. The IDT members and the support groups serve togive an objective analysis and review of the various design alternatives for the region’s project. Theycontribute ideas and participate in the selection of design alternatives. This work will often culminate inthe publication of the Environmental Impact Statement (EIS).

Bridge Design Engineers are often asked to be a part of this process, either as a support resource or as amember of the IDT itself.

2.1.2 Value Engineering Studies

Value Engineering (VE) is a process of review and analysis of a project. The VE team seeks to define themost cost-effective means of satisfying the basic function(s) of the project. Usually a VE study takes placebefore or during the time that the region is working on the design. Occasionally a VE study examines aproject with a completed PS&E.

A VE team is typically made up of members of different expertise and backgrounds, selected from theregion, Service Center, and outside agencies. The Team Facilitator will lead the team through the VEprocess. The team will review the project as defined by the project’s design personnel. They will seek todecide the basic function(s) that are served by the project, brainstorm to develop other alternatives toserve the same function(s), and evaluate these alternatives on how well they satisfy these basic functions.The VE team will present their findings in a presentation to the region. The region is then required toinvestigate these findings further and address them in the design.

Bridge Design Engineers are often asked to be a part of this process, either as support contacts or as VEteam members. The process usually involves three to five days.

2.1.3 Preliminary Project Recommendations (Existing Bridges)

Projects that call for the rehabilitation of an existing bridge require that the existing condition of thebridge be reviewed and a recommendation the existing bridge be prepared. When a region starts a designfor such a project, they will request by an Inter-Departmental (IDC) memorandum that the Bridge andStructures Office make Preliminary Project recommendations. This will provide them with a scope ofwork and a cost estimate for the project. It involves review of the inspection and condition reports fromthe Bridge Preservation Section and a site visit with the region and other project stakeholders. Specialinspections of certain portions of the structure may need to be scheduled to determine the load capacity ofthe existing bridge, what types of rehabilitation work need to be done, the extended life span achieved bycertain types of rehabilitation work, and to develop various alternatives with cost estimates for compari-son, ranging from “do nothing” to “replacement.”

A typical recommendation consists of two parts. The first is a report to the file providing detailedinformation related to the bridge rehabilitation and a summary of the various alternatives considered andan itemized list of the rehabilitation work with the associated costs. The second part is an IDC to theregion discussing the overall project in general terms mentioning any particular items of concern to theregion and a summary of the preferred alternatives with recommendations. The region should be given theopportunity to review a draft report and IDC and provide input prior to finalization.

2.1-2 August 1998



2.1.4 Preliminary Project Recommendations (New Bridges)

Projects that call for a new bridge require that a recommendation for the new structure be prepared. Whilea region is preparing a design for a project, they will seek assistance from the Bridge and StructuresOffice by writing an IDC. This request could range from confirmation of construction cost data toconsideration of various structure designs or staging alternatives. An IDC to the region will providerecommendations and information. A face to face meeting with the region project staff is recommended.

2.1.5 Type, Size, and Location Studies

It is the policy of the Federal Highway Administration (FHWA) that major or unusual bridges must gothrough the preparation of a Type, Size, and Location (TS&L) study. The TS&L study will outline theproject, describe the proposed structure and other design alternatives considered, and show justificationfor the selection of the preferred alternative. Approval of the TS&L study by FHWA is the basis foradvancing the project to the design stage.

The FHWA requires a TS&L study for tunnels, movable bridges, unusual structures, and major structureswith deck areas greater than 125,000 square feet. This is a guideline only. Smaller bridges that are unusualmay also require a TS&L study while some, such as long viaducts, may not. As early as possible in theProject Development stage, the FHWA should be contacted for conformation.

The preparation of the TS&L study is the responsibility of the Bridge and Structures Office. The TS&Lcannot be submitted to FHWA until after the Environmental documents have been submitted. However,TS&L preparation need not wait for Environmental document approval, but may begin as soon as thebridge site data is available. See Chapter 1110 of the Design Manual for the type of information requiredfor a bridge site data submittal.

A. TS&L General

In order to become familiar with the project, the designer should first review its history. TheEnvironmental and Design Reports should be reviewed. The bridge site data should be scrutinized sothat additional data, maps, or drawings can be requested. After reviewing the history of the project, ameeting with region and a site visit should be arranged.

In order to have foundation information, the Materials Lab must be contacted early. FHWA expectsspecific recommendations on the foundation type. The Materials Lab will submit a detailedfoundation report for inclusion as an appendix to the TS&L study.

In order to find the preferred structural alternative, the designer should:

l. Develop a list of all the feasible alternatives. At this stage of the process, the range of alternativesshould be kept wide open. Brainstorming with supervisors and other engineers can help bring outfresh and innovative solutions.

2. Eliminate the unusable alternatives by applying the constraints of the project. Question restrictiveconstraints and document their bases. At the end of this step, there should be no more than fouralternatives.

3. Perform preliminary level design calculations for unique structural problems to ensure that theremaining alternatives are feasible.

4. Compare the advantages, disadvantages, and costs of the remaining alternatives to determine thepreferred alternative(s).

5. Visit the project site with the region and Geotech Branch.

August 1998 2.1-3



After piers have been located, a memorandum request for a Hydraulics Report should be made tothe Olympia Service Center Hydraulics Unit. FHWA expects specific information on scour andbackwater on both falsework and permanent piers. The Olympia Service Center Hydraulics Unitwill submit a report for inclusion as an appendix to the TS&L study.

The Bridge Architect at the Bridge and Structures Office should be consulted early on andthroughout the study process “Notes to the file” should be made documenting the aestheticrequirements and recommendations of the Architect.

Cost backup data is needed for any costs used in the TS&L study. FHWA expects TS&L costsbased on estimated quantities. This data is to be included in an appendix to the TS&L study. It isa good idea to coordinate the quantities submitted are in a form compatible with the estimator’scost breakdown method.

B. TS&L Outline

The TS&L study should describe the project, the proposed structure, and give reasons why the bridgetype, size, and location were selected.

1. Cover, Title Sheet, and Contents

These should identify the project and the contents of the TS&L.

2. Photographs

There should be enough color photographs to provide the look and feel of the area. The printsshould be numbered and labeled and the location indicated on a diagram.

3. Introduction

The introduction describes the report and references other reports used to prepare the TS&Lstudy. The following reports should be listed if used.

• Design Reports and Supplements

• Environmental Reports

• Architectural or Visual Assessment Reports

• Hydraulic Report

• Geotechnical Reports

4. Project Description

The project description is intended to summarize the preferred alternative of the project design sothat the TS&L study clearly defines the project. Care should be taken to describe the projectadequately but briefly. A vicinity map should be shown.

5. Design Criteria

Design criteria states to what code, loading, etc., the bridge will be constructed. Besidesthe AASHTO specifications and assorted AASHTO guide specifications, other criteria aresometimes used. These criteria should be listed. Examples of this would be the temperatureloading used for segmental bridges or areas defined as wetlands.

2.1-4 August 1998



6. Structural Studies

The structural studies section documents how the proposed structure type, size, and location weredetermined. The following considerations should be addressed.

• Aesthetics

• Cost Estimates

• Geometric constraints

• Project staging

• Foundations

• Hydraulics

• Feasibility of construction

• Structural constraints

• Maintenance

This section should have a narrative style describing how these factors point to the preferredalternative. Show how each constraint eliminated or supported the alternatives. For instance,“Because the geometry required a 200-foot span, prestressed concrete girders could not be used”or “Restrictions on falsework placement forced the use of self supporting precast concrete orsteel girders.”

7. Executive Summary

The executive summary should be able to stand alone as a separate document. The project andstructure description should be given. Present the recommended alternative with its cost andinclude a summary of considerations used to choose or eliminate alternatives.

8. Drawings

Preliminary Plan drawings of the recommended alternative are included in the appendix. Thedrawings show the plan, elevation, and typical section. For projects where alternative designs arespecified as recommended alternatives, Preliminary Plans for each of these structure types shallbe included. Supplemental drawings showing special features, such as complex piers, are oftenprovided to clearly define the project.

C. Reviews and Submittal

While writing the TS&L study, all major decisions should be discussed with the unit supervisor, whocan decide if the Bridge Design Engineer needs to be consulted. A peer review meeting with theBridge Design Engineer should be scheduled at 50 percent completion. The FHWA Bridge Engineershould be invited to provide input.

The final report must be reviewed, approved, and the Preliminary Plan drawings signed by the BridgeArchitect, the Bridge Projects Engineer, the Bridge Design Engineer, and the Bridge and StructuresEngineer. The TS&L study is submitted with a cover letter to FHWA signed by the Bridge andStructures Engineer.

2:DP:BDM2

August 1998 2.2-1


Preliminary Design Preliminary Plan

2.2 Preliminary Plan

The Preliminary Plan is the most important phase of bridge design as it sets the groundwork for the finaldesign. The intent is to completely define the bridge geometry so final roadway design by the regions andthe structural design by the Bridge and Structures Office can take place with minimal revisions.

During the region’s preparation of the highway design, they also begin work on the bridge site data.Region submits the bridge site data to the Bridge and Structures Office which initiates the start of thePreliminary Plan. Information that must be included as part of the bridge site data submittal is outlinedin Chapter 1110 of the Design Manual.

2.2.1 Development of the Preliminary Plan

A Responsibilities

In general, the responsibilities of the designer, checker, detailer, and supervisor are as specified inChapter 1 of the Bridge Design Manual. The primary design engineer is responsible for developing aPreliminary Plan for the structure that is compatible with geometric, aesthetic, staging, geotechnical,hydraulic, financial, and structural requirements and conditions that exist at the site.

Upon receipt of the bridge site data from the region, the designer shall review it for completeness andverify that what the project calls for is realistic and structurally feasible. Any omissions or correctionsare to be called to the region’s attention immediately.

The supervisor shall be kept informed of progress on the preliminary plan so that the schedule canbe monitored. Should problems develop, the supervisor can make adjustments to the schedule ormanpower assignments. The designer must keep the job file up to date by documenting all conversa-tions, meetings, requests, questions, and approvals concerning the project. Notes to the designer, anddetails not shown in the Preliminary Plan shall be documented in the job file.

The checker shall give an independent review of the plan, verifying that it is in compliance with thesite data as provided by the region and as corrected in the job file. The plan shall be compared againstthe Preliminary Plan checklist to ensure that all necessary information is shown. The checker is toreview the plan for consistency with office design practice, detailing practice, and for constructibility.

The preliminary plan shall be drawn using current office CAD equipment and software by theEngineer or Detailer.

B. Site Reconnaissance

The site data submitted by the region will include a video and photographs of the site. Even forminor projects, this may not be enough information for the designer to work from in developing thePreliminary Plan. For most bridge projects, site visits are necessary. Site visits with region projectstaff and other project stakeholders such as Hydraulics, Design, and Geotech Branch should bearranged with the knowledge and approval of the Bridge Projects Engineer.

C Coordination

The designer is responsible for coordinating the design and review process throughout the project.This includes seeking input from various WSDOT units and outside agencies.

D. Consideration of Alternatives

In the process of developing the Preliminary Plan, the designer should brainstorm, develop, andevaluate various design alternatives. Depending on how the General Factors for Consideration(Section 2.2.3) apply to a particular site, the number of alternatives will usually be limited to only a

2.2-2 August 1998



few for most projects. For some smaller projects and most major projects, design alternatives meritdevelopment and close evaluation. The process of considering and rejecting design alternativesprovides documentation for the preferred alternative.

E. Designer Recommendation

Once the designer has done a thorough job of evaluating the needs and limitations of the site,analyzed all information and developed and evaluated design alternatives for the project, he shouldbe able to make a recommendation for the optimum solution. Based on this recommendation, thedesigner should discuss the recommendation with the Bridge Projects Engineer.

F. Concept Approval

For some projects, the presentation, in “E” above, to the Bridge Projects Engineer will satisfy theneed for concept approval. Large complex projects, projects of unique design, or projects where twoor more alternatives appear viable, should be presented to the Bridge Design Engineer for hisconcurrence before plan development is completed. For unique or complex projects a presentation ismade to the Bridge and Structures Office Peer Review Committee.

G. Inspection and Maintenance Access

In the process developing the Preliminary Plan, the design engineer should consult with the BridgePreservation Section for input.

2.2.2 Documentation

A. Job File

When a memorandum IDC, transmitting site data from the region is received by the Bridge andStructures Office, a job file is created. This official job file serves as a depository for allcommunications and resource information for the job. Scheduling and time estimates are logged inthis file, as well as cost estimates, preliminary quantities, and documentation of all approvals.

When the Preliminary Plan is completed, the job file continues to serve a useful purpose as acommunications and documentation depository for all pertinent project-related information duringthe design process.

B. Bridge Site Data

All Preliminary Plans are developed from site data as submitted by the region. This submittal willconsist of a memorandum IDC, and appropriate attachments as specified by Chapter 1110 of theDesign Manual. When this information is received, it should be reviewed for completeness so thatmissing or incomplete information can be noted and requested.

C. Request for Preliminary Foundation Data

A Request for Preliminary Foundation Data is sent to Geotech Branch to solicit any foundationdata that is available at this preliminary stage. The Geotech Branch is provided with approximatedimensions for overall structure length and width, an approximate number of intermediate piers(if applicable), and approximate stations for beginning and end of structure on the alignment.

Based on test holes from previous construction in the area, geological maps, and soil surveys.The Materials Lab responds by IDC giving an analysis of what foundation conditions arc likely tobe encountered and what types of substructure are best suited for these conditions.

August 1998 2.2-3



D. Request for Preliminary Hydraulics

A Request for Preliminary Hydraulics data is sent to the Hydraulics Office to document hydraulicrequirements that must be considered in the structure design. The Hydraulics Office is provided withthe contour plan and other bridge site data.

Seal vent elevations, normal water, 100-year flood and 500-year flood elevations, and flows (Q), pierconfiguration, scour depth and minimum footing cover, ice pressure, minimum waterway channelwidth, riprap requirements, and minimum clearance to the 100-year flood elevation are provided inan ºIDC response from the Hydraulics Office.

E. Design Report or Design Summary

Some bridge construction projects have a Design Report or Design Summary prepared by the region.This is a document which includes design considerations and conclusions reached in the developmentof the project. It defines the scope of work for the project. It serves to document the design standardsand applicable deviations for the roadway alignment and geometry. It is also an excellent referencefor project history, safety and traffic data, environmental concerns, and other information.

F. Other Resources

For some projects, preliminary studies or reports will have been prepared. These resources canprovide additional background for the development of the Preliminary Plan.

G. Notes if meetings with Regions and other project stakeholders shall be included in the documentation.

2.2.3 General Factors for Consideration

Many factors must be considered in preliminary bridge design. Some of the more common of these arelisted in general categories below. These factors will be discussed in appropriate detail in subsequentportions of this manual.

A. Site Requirements

Topography Alignment (tangent, curved, skewed)Vertical profile and superelevationProposed or existing utilities

B. Safety

Feasibility of falsework (impaired clearance and sight distance)Density and speed of trafficDetours or possible elimination of detours by staging constructionSight distanceHorizontal clearance to piersHazards to pedestrians, bicyclistsInspection and Maintenance Access (UBIT clearances) (see Figure 2.3.10-1)

C. Economic

Funding classification (federal and state funds, state funds only, local developer funds)Funding level

2.2-4 August 1998



D. Structural

Limitation on structure depthRequirements for future wideningFoundation and groundwater conditionsAnticipated settlement

E. Environmental

Site conditions (wetlands, environmentally sensitive areas)EIS requirementsMitigating measures

F. Aesthetic

General appearanceCompatibility with surroundings and adjacent structuresVisual exposure and importance

G. Construction

Ease of constructionFalsework clearances and requirementsErection problemsHauling difficulties and access to siteConstruction seasonTime limit for construction

H. Hydraulic

Bridge deck drainageStream flow conditions and driftPassage of flood debrisScour, effect of pier as an obstruction (shape, width, skew, number of columns)Bank and pier protectionConsideration of a culvert as an alternate solutionPermit requirements for navigation and stream work limitations

I. Other

Prior commitments made to other agency officials and individuals of the communityRecommendations resulting from preliminary studies

2.2.4 Permits

A. Coast Guard

As outlined in Chapter 240 of the Design Manual, the Bridge and Structures Office is responsible forcoordinating and applying for Coast Guard permits for bridges over waterways. This is handled bythe Coast Guard Liaison Engineer in the Bridge Projects Unit of the Bridge and Structures Office.

A determination of whether a bridge requires a permit is known before the bridge site data isreceived. Generally, tidal-influenced waterways and waterways used for commercial navigation willrequire Coast Guard permits. However, some waterways may qualify for an exemption from a permitif certain conditions apply including the exclusion of use by vessels larger than 21 feet long. The

August 1998 2.2-5



process of getting this exemption, from FHWA, not the Coast Guard, is the responsibility of theregion. The Coast Guard Liaison Engineer should be asked to check with the region and the CoastGuard to confirm the situation on a case by case basis.

For all waterway crossings, the Coast Guard Liaison Engineer is required to initial the PreliminaryPlan as to whether a Coast Guard permit or exemption is required. This box regarding Coast Guardpermit status is located in the center left margin of the plan. If a permit is required, the permit targetdate will also be noted. The reduced print, signed by the Coast Guard Liaison Engineer, shall beplaced in the job file.

The work on developing the permit application should be started such that it is ready to be sent to theCoast Guard eight months before the project ad date. The Coast Guard Liaison Engineer should begiven a copy of the Preliminary Plan from which to develop the plan sheets that are part of the permit.

B. Other

All other permits will be the responsibility of the region. The Bridge and Structures Office may beasked to provide information to the region to assist them in making applications for these permits.

2.2.5 Approvals

A. Bridge Design

When the Preliminary Plan has been checked by the checker and signal by the Bridge ProjectsEngineer, it is ready to go to the Bridge Design Engineer and the Bridge and Structures Engineerfor approval.

B. Bridge Architect

For all preliminary plans, the Architect should be aware and involved when the designer is firstdeveloping the plan. The Architect should be presented with a reduced print of the plan by thedesigner. This is done prior to the job going to the checker. The Architect will review the print andsignify his approval by signing it. This print is placed in the job file. If future plan revisions changeelements of aesthetic importance, the Architect should be asked to review and approve, by signature,a print of the revised plan.

For large, multiple bridge projects, the Bridge Architect should be contacted for development of acoordinated architectural concept for the project corridor. The architectural concept for a projectcorridor is generally developed in draft form and reviewed with the project stakeholders prior tofinalizing.

C. Region

Prior to the completion of the preliminary plan the designer should meet with the region to discuss theconcept and get their input. When the Preliminary Plan and the “Not Included in Bridge QuantitiesList” along with the preliminary plan transmittal IDC.

The region will review the plan for compliance and agreement with their original site data. They willwork to answer any notes to the region that have been listed on the plan. When this review is com-plete, the Regional Administrator, or his representative, will sign the plan. The region will send backa print of the plan with any comments noted in red (additions) and green (deletions) along withresponses to the notes to the region.

2.2-6 August 1998



D. Railroad

When a railroad is involved with a structure on a Preliminary Plan, the Right of Way AccommodationEngineer of the Design Office must be involved during the plan preparation process. A copy of thePreliminary Plan is sent to the Right of Way Accommodation Engineer, who then sends a copy to therailroad involved for their comments and approval.

The railroad will respond with approval by letter to the Right of Way Accommodation Engineer.A copy of this letter is then routed to the Bridge and Structures Office and is placed in the job file.

P:DP/BDM2

August 1998 2.3-1


Preliminary Design Preliminary Plan Criteria

2.3 Preliminary Plan Criteria

2.3.1 Highway Crossings

A. General

A highway crossing is defined as a grade separation between two intersecting roadways. A highwaycrossing is further categorized as either an undercrossing or an overcrossing.

1. Undercrossing

A bridge which provides for passage of a state highway under a less important state highway,a county road, or a city street is called an undercrossing. Relative importance between statehighways is indicated by functional classification. For details, see Chapter 440 of theDesign Manual.

For example, a bridge included as a part of an interchange involving SR 182 (Interstate) andSR 14 (Principal) and providing for passage of traffic on SR 182 under SR 14 would be calledSR 14 I/C Undercrossing.

2. Overcrossing

A bridge which carries traffic on a state highway over a less important state highway, a countyroad, or a city street is called an overcrossing.

For example, a bridge which carries traffic on SR 5 over Hamilton Road would be calledHamilton Road Overcrossing.

B. Bridge Width

The bridge roadway channelization is provided by the region with the Bridge Site Data. For statehighways, the roadway geometrics are controlled by Chapters 430 and 440 of the Design Manual. Forcity and county arterials, the roadway geometrics are controlled by Chapter IV of the Local AgencyGuidelines.

C. Horizontal Clearances

Safety dictates that fixed objects be placed as far from the edge of the roadway as is economicallyfeasible. Criteria for minimum horizontal clearances to bridge piers and retaining walls are outlined inthe Design Manual. Chapter 710 of the Design Manual outlines clear zone and recovery arearequirements for horizontal clearances without guardrail or barrier being required.

Actual horizontal clearances shall be shown in the plan view of the Preliminary Plan (to the nearest0.1 foot). Minimum horizontal clearances to inclined columns or wall surfaces should be provided atthe roadway surface and for a vertical distance of 6 feet above the edge of pavement. When bridgeend slopes fall within the recovery area, the minimum horizontal clearance should be provided for avertical distance of 6 feet above the fill surface. See Figure 2.3.1-1.

Bridge piers and abutments ideally should be placed such that the minimum clearances can besatisfied. However, if for structural or economic reasons, the best span arrangement requires a pier tobe within clear zone or recovery area, then guardrail or barrier can be used to mitigate the hazard.

There are instances where it may not be possible to provide the minimum horizontal clearance evenwith guardrail or barrier. An example would be placement of a bridge pier in a narrow median. Therequired column size may be such that it would infringe on the shoulder of the roadway. In suchcases, the New Jersey barrier shape would be incorporated into the shape of the column. Barrier or

2.3-2 August 1998



guardrail would need to taper into the pier at a flare rate satisfying the criteria in Chapter 710 of theDesign Manual. See Figure 2.3.1-2. The reduced clearance to the pier would need to be approved bythe region.

D. Vertical Clearances

The required minimum vertical clearances are established by the functional classification of thehighway and the construction classification of the project. For state highways, this is as outlined inChapters 430 and 440 of the Design Manual. For city and county arterials, this is as outlined inChapter IV of the Local Agency Guidelines.

Actual minimum vertical clearances are shown on the Preliminary Plan (to the nearest 0.1 foot). Theapproximate location of the minimum vertical clearance is noted in the upper left margin of the plan.For structures crossing divided highways, minimum vertical clearances for both directions are noted.

E. End Slopes

The type and rate of end slope used at bridge sites is dependent on several factors. Soil conditions andstability, right of way availability, fill height or depth of cut, roadway alignment and functionalclassification, and existing site conditions are all important.

The region should have made a preliminary determination based on these factors during thepreparation of the bridge site data. The side slopes noted on the Roadway Section for the roadwayshould indicate the type and rate of end slope.

The Materials Lab will recommend the minimum rate of end slope. This should be compared to therate recommended in the Roadway Section and to existing site conditions (if applicable). The types ofend slopes and the conditions for which each are applicable are spelled out in Chapter 640 of theDesign Manual.

End slope protection may be required at certain highway crossings, as spelled out in Chapter 1120 ofthe Design Manual. Examples of slope protection are shown on Standard Plan D-9.

F. Determination of Bridge Length

Establishing the location of the end piers for a highway crossing is a function of the profile grade ofthe overcrossing roadway, the minimum vertical and horizontal clearances required for the structure,and the type and rate of end slope used.

For the general case of bridges in cut or fill slopes, the control point is where the cut or fill slopeplane meets the bottom of ditch or edge of shoulder as applicable. From this point, the fill or cut slopeplane is established at the recommended rate up to where the slope plane intersects the grade of theroadway at the shoulder. Following the requirements of Standard Plan H-9, the back of pavementseat, end of wing wall or end of retaining wall can be established at 3 feet behind the slopeintersection.

For the general case of bridges on wall type or “closed” abutments, the controlling factors are therequired horizontal clearance and the size of the abutment. This situation would most likely occur inan urban setting or where right of way is limited.

August 1998 2.3-3



Horizontal Clearance to Inclined Piers1990

Figure 2.3.1-1

Bridge Pier in Narrow Median1990

Figure 2.3.1-2

2.3-4 August 1998



G. Pedestrian Crossings

Pedestrian crossings follow the same format as highway crossings. Geometric criteria for pedestrianfacilities are established in Chapter 1020 of the Design Manual. Width and clearances would be asestablished there and as confirmed by region. Unique items to be addressed with pedestrian facilitiesinclude ADA requirements, the railing to be used, handrail requirements, overhead enclosurerequirements, and profile grade requirements for ramps and stairs.

H. Bridge Redundancy

Design bridges to minimize the risk of catastrophic collapse by using redundant supporting elements(columns and girders).

For substructure design use:

One column minimum for roadways 28 feet wide and under.Two columns minimum for roadways over 28 feet to 40 feet.Three columns minimum for roadways over 40 feet to 60 feet.Collision protection or design for collision loads for piers with one or two columns.

For superstructure design use:

Three girders (webs) minimum for roadways 32 feet and under.Four girders (webs) minimum for roadways over 32 feet.

See Appendix 2.3-A2 for details.

Note: Any deviation from the above guidelines shall have a written approval by the BridgeDesign Engineer.

2.3.2 Railroad Crossings

A. General

A railroad crossing is defined as a grade separation between an intersecting highway and a railroad.A bridge which provides highway traffic over the railroad is called an overcrossing. A bridge whichprovides highway traffic under the railroad is called an undercrossing.

Requirements for railroad separations for both undercrossings and overcrossings may involvenegotiations with the railroad company concerning clearances, geometrics, utilities, and maintenanceroads. The railroad’s review and approval, will be based on the completed Preliminary Plan.

B. Criteria

The initial Preliminary Plan shall be prepared in accordance with the criteria of this section toapply uniformly to all railroads. Variance from this criteria will be negotiated with the railroad,when necessary, after a Preliminary Plan has been provided for their review.

C. Bridge Width

For railroad overcrossings, the provisions of Section 2.3.1 pertaining to bridge width of highwaycrossings shall apply. Details for railroad undercrossings will depend on the specific project and therailroad involved.

August 1998 2.3-5



D. Horizontal Clearances

For railroad undercrossings, the provisions of Section 2.3.1 pertaining to horizontal clearances forhighway crossings shall apply. However, because of the heavy live loading of railroad spans, it isadvantageous to reduce the span lengths as much as possible. For railroad undercrossings skewed tothe roadway, piers may be placed up to the outside edge of 8-foot (minimum) shoulders if certainconditions are met (structural requirements, satisfactory aesthetics, satisfactory sight distance, etc.).

The actual minimum horizontal clearances are shown in the Plan view of the Preliminary Plan (to thenearest 0.1 foot). For railroad overcrossings, minimum horizontal clearances are as noted below:

Railroad Alone

Fill Section 14 feet

Cut Section 16 feet

Horizontal clearance shall be measured from the center of the outside track to the face of pier. Whenthe track is on a curve, the minimum horizontal clearance shall be increased at the rate of 11/2 inchesfor each degree of curvature. An additional 8 feet of clearance for off-track equipment shall only beprovided when specifically requested by the railroad.

E. Crash Walls

Crash walls, when required, shall be designed to conform to the criteria from of the AREA Manual.

F. Vertical Clearances

For railroad undercrossings, the provisions of Section 2.3.1 pertaining to vertical clearances ofhighway crossings shall apply. For railroad overcrossings, the minimum vertical clearance shallsatisfy the requirements of Chapter 1120 of the Design Manual.

The actual minimum vertical clearances are shown on the Preliminary Plan (to the nearest 0.1 foot).The approximate location of the minimum vertical clearance is noted in the upper left margin of theplan.

G. Determination of Bridge Length

For railroad overcrossings, the provisions of Section 2.3.1 pertaining to the determination of bridgelength shall apply. For railroad overcrossings, the minimum bridge length shall satisfy the minimumhorizontal clearance requirements. The minimum bridge length shall generally satisfy therequirements of Figure 2.3.2-1.

H. Special Considerations

For railroad overcrossings, the top of footings for bridge piers or retaining walls adjacent to railroadtracks shall be 2 feet or more below the top of tie. The footing face shall not be closer than 10 feet tothe center of the track. Any cofferdams, footings, excavation, etc., encroaching within 10 feet of thecenter of the track requires the approval of the railroad.

2.3-6 August 1998



For railroads, the minimum horizontal construction opening is 8 feet 6 inches to either side of the center-line of track. The minimum vertical construction opening is 22 feet 6 inches above the top of rail at 6 feetoffset from the centerline of track. Falsework openings shall be checked to verify that enough space isavailable for falsework beams to span the required horizontal distances and still provide the minimumvertical falsework clearance. Minimum vertical openings of less than 22 feet 6 inches may be negotiatedwith the railroad through the Utilities-Railroad Engineer.

2.3.3 Water Crossings

A. Bridge Width

The provisions of Section 2.3.1 pertaining to bridge width for highway crossings apply here.

B. Horizontal Clearances

Water crossings over navigable waters requiring clearance for navigation channels shall satisfy thehorizontal clearances required by the Coast Guard. Communication with the Coast Guard will behandled through the Coast Guard Liaison Engineer. For bridges over navigable waters, the centerlineof the navigation channel and the horizontal clearances (to the nearest 0.1 foot) to the piers or the pierprotection are shown on the Plan view of the Preliminary Plan.

C. Vertical Clearances

Vertical clearances for water crossings must satisfy floodway clearance and, where applicable,navigation clearance.

Bridges over navigable waters must satisfy the vertical clearances required by the Coast Guard.Communication with the Coast Guard will be handled through the Coast Guard Liaison Engineer.The actual minimum vertical clearance (to the nearest 0.1 foot) for the channel span is shown on thePreliminary Plan. The approximate location of the minimum vertical clearance is noted in the upperleft margin of the plan. The clearance shall be shown to the water surface as required by the CoastGuard criteria.

Floodway vertical clearance will need to be discussed with the Hydraulics Office. In accordance withthe flood history, nature of the site, character of drift, and other factors, they will determine a mini-mum vertical clearance for the 100-year flood. The roadway profile and the bridge superstructuredepth must accommodate this. The actual minimum vertical clearance to the 100-year flood is shown(to the nearest 0.1 foot) on the Preliminary Plan, and the approximate location of the minimumvertical clearance is noted in the upper left margin of the plan.

D. End Slopes

The type and rate of end slopes for water crossings is similar to that for highway crossings. Soilconditions and stability, fill height, location of toe of fill, existing channel conditions, flood and scourpotential, and environmental concerns are all important.

As with highway crossings, the region, and Materials Lab will make preliminary recommendations asto the type and rate of end slope. The Hydraulics Office will also review the Regions’srecommendation for slope protection.

E. Determination of Bridge Length

Determining the overall length of a water crossing is not as simple and straight forward as for ahighway crossing. Floodway requirements and environmental factors have a significant impact onwhere piers and fill can be placed.

August 1998 2.3-7



Determination of Bridge Length for a Railroad UndercrossingFigure 2.3.2-1

If a water crossing is required to satisfy floodway and environmental concerns, it will be known bythe time the Preliminary Plan has been started. Environmental studies and the Design Report preparedby the region will document any restrictions on fill placement, pier arrangement, and overall flood-way clearance. The Hydraulics Office will need to review the size, shape, and alignment of all bridgepiers in the floodway and the subsequent effect they will have on the base flood elevation. The overallbridge length may need to be increased depending on the span arrangement selected and the change inthe flood backwater, or justification will need to be documented.

F. Scour

The Hydraulics Office will indicate the anticipated depth of scour at the bridge piers. They willrecommend pier shapes to best streamline flow and reduce the scour forces. They will also recom-mend measures to protect the piers from scour activity or accumulation of drift (minimum cover totop of footing, riprap, pier alignment to stream flow, closure walls between pier columns, etc.).

G. Pier Protection

For bridges over navigable channels, piers adjacent to the channel may require pier protection. TheCoast Guard will determine whether pier protection is required. This determination is based on thehorizontal clearance provided for the navigation channel and the type of navigation traffic using thechannel.

H. Construction Access and Time Restrictions

Water crossings will typically have some sort of construction restrictions associated with them. Thesemust be considered during preliminary plan preparation.

2.3-8 August 1998



The time period that the contractor will be allowed to do work within the waterway may be restrictedby regulations administered by various agencies. Depending on the time limitations, a bridge withfewer piers or faster pier construction may be more advantageous even if more expensive.

Contractor access to the water may also be restricted. Shore areas supporting certain plant species aresometimes classified as wetlands. In order to work in or gain access through such areas, a work trestlemay be necessary. Work trestles may also be necessary for bridge removal as well as new bridgeconstruction.

2.3.4 Bridge Widenings

A. Bridge Width

The provisions of Section 2.3.1 pertaining to bridge width for highway crossings shall apply. In mostcases, the width to be provided by the widening will be what is called for by the design standards,unless a deviation is approved.

B. Traffic Restrictions

Bridge widenings inherently involve traffic restrictions on the lanes above and where applicable onthe lanes below. The bridge site data submitted by the district should contain information regardingtemporary lane widths and staging configurations. This information should be checked to be certainthat the existing bridge width, and the bridge roadway width during the intermediate constructionstages of the bridge are sufficient for the lane widths, shy distances, temporary barriers, and construc-tion room for the contractor. These temporary lane widths and shy distances are noted on thePreliminary Plan. The temporary lane widths and shy distances on the roadway beneath the bridgebeing widened should also be checked that adequate clearance is available for any substructureconstruction.

C. Construction Sequence

Using the traffic restriction data in the bridge site data, a construction sequence shall be developed.Such a sequence shall take into account necessary steps for construction of the bridge widening(substructure and superstructure), any construction work off of and adjacent to the structure, and therequirements of traffic flow on and below the structure. Checks shall be made to be certain that girderspacings, closure pours, and removal work are all compatible with the traffic arrangements.

Projects with several bridges being widened at the same time should have sequencing that iscompatible with the region’s traffic plans during construction and that allow the contractor roomto work. It is important to meet with the region project staff to assure that the construction staging andcharacterization of traffic during construction is constructible and minimizes the impact to thetraveling public.

2.3.5 Detour Structures

A. Bridge Width

The lane widths, shy distances, and overall roadway widths for detour structures are determined bythe Region. Review and approval of detour roadway widths is done by the Traffic Office.

B. Live Load

Unless otherwise justified, all detour structures shall be designed for an AASHTO HS 15 live load.Construction requirements and staging can be sufficient reason to justify designing for a higherlive load.

August 1998 2.3-9



2.3.6 Retaining Walls and Noise Walls

The requirements for Preliminary Plans for retaining walls and noise walls are similar to the requirementsfor bridges. The plan and elevation views define the overall limits and the geometry of the wall. Thesection view will show general structural elements that are part of the wall and the surface finish of thewall face.

The most common types of walls are outlined in Section 9.4.2 of the Bridge Design Manual andChapter 1130 of the Design Manual. The Bridge and Structures Office is responsible for PreliminaryPlans for all nonstandard walls (retaining walls and noise walls) as spelled out in Chapter 1130 of theDesign Manual.

2.3.7 Bridge Deck Drainage

The Hydraulics Office provides a review of the Preliminary Plan with respect to the requirements forbridge deck drainage. As soon as the Preliminary Plan has been developed to the point that the length andwidth of the structure, profile grade, and superelevation diagram are shown on the plan, a reduced printshall be provided to the Hydraulics Office for their review. Any other pertinent information (such aslocations of drainage off the structure) should be given to them also. For work with existing structures, thelocations of any and all bridge drains shall be noted.

The Hydraulics Office will determine the type of drains necessary (if any) and their location and spacingrequirements. They will furnish any details or modifications required for special drains or specialsituations.

If low points of sag vertical curves or superelevation crossovers occur within the limits of the bridge, theregion should be asked to revise their geometrics to place these features outside the limits of the bridge.If such revisions cannot be made, the Hydraulics Office will provide details to handle drainage withbridge drains on the structure.

2.3.8 Bridge Deck Protective Systems

The Preliminary Plan shall note in the lower left margin the type of deck protective system to be utilizedon the bridge. The most commonly used systems are described in Section 8.4.7 of the Bridge DesignManual.

New construction will generally be System 1 (21/2-inch concrete cover plus epoxy-coated rebars).System 2 (MC overlay) and System 3 (ACP overlay) are to be used on new construction that requireoverlays and on widenings for major structures. The type of overlay to be used should be noted in thebridge site data submitted by the region. The bridge condition report will indicate the preference of theBridge and Structures Office and the Deck Systems Specialist in the Bridge and Structures Office.

2.3.9 Construction Clearances

Most projects will involve construction in and around traffic. Both traffic and construction have to beaccommodated. Construction clearances and working room must be reviewed at the Preliminary Planstage to verify the constructibility of the project.

For construction clearances for roadways, the region shall supply the necessary traffic staging informationwith the bridge site data. This includes temporary lane widths and shy distances, allowable or necessaryalignment shifts, and any special minimum vertical clearances. With this information, the designer canestablish the falsework opening or construction opening.

2.3-10 August 1998



The horizontal dimension of the falsework or construction opening shall be the sum of the temporarytraffic lane widths and shy distances, plus two 2-foot temporary concrete barriers, plus 2 feet shy behindthese barriers. For multispan openings, a minimum of 2 feet shall be assumed for the interior support. Thisinterior support shall also have 2 feet shy on both sides to the two 2-foot temporary concrete barriers thatwill flank it.

The vertical clearance shall normally be 14 feet 6 inches minimum. The space available for the falseworkmust be enough for whatever depth is necessary to span the required horizontal opening. If the necessarydepth is greater than the space available, either the minimum vertical clearance for the falsework shall bereduced or the horizontal clearance and span for the falsework shall be reduced.

Preferably, the falsework span shall not exceed 38 feet. This limits the stresses in the new structure fromthe construction and concrete pouring sequences. While the falsework or construction openings aremeasured normal to the crossroad alignment, the falsework span is measured parallel to the bridgealignment.

Once the construction clearances have been determined the designer should meet with the region toreview the construction clearances to assure compatibility with the construction staging. This reviewshould take place prior to finalization of the preliminary bridge plan.

For railroads see Section 2.3.2H.

2.3.10 Inspection and Maintenance Access

A. General

Bridge inspection is required by the FHWA a minimum of every two years. The inspectors arerequired to access the bridge components to within 3 feet (1 meter). Maintenance forces need toaccess damaged members and locations that may collect debris. This is accomplished by using manymethods. Safety cables, ladders, bucket trucks, Under Bridge Inspection Truck (UBIT), (see Figure2.3.10-1), and under bridge travelers are just a few of the most common methods. Preliminarydesigners need to be aware of these requirements to assist the inspectors efforts over the life of thebridge. Access should be considered throughout the Preliminary Plan TS&L stages.

August 1998 2.3-11



Figure 2.3.10-1

B. Safety Cables

Safety cables strung on steel plate girders or trusses allow for walking access. Care must be given tothe application and location. Built-up plate girder bridges are detailed with a safety cable for inspec-tors walking the bottom flange. However, when the girders become more than 8 feet deep, theinspection of the top flange and top lateral connections becomes difficult. When the girders are lessthan 5 feet deep, it is not feasible for the inspectors to stand on the bottom flanges. On large trusses,large gusset plates (3 feet or more wide) are difficult to negotiate around. Cable are best run on theexterior of the bridge except at large gusset plates. At these locations, cables or lanyard anchorsshould be placed on the inside face of the truss. This way inspectors can utilize bottom lateral gussetplates to stand on while traversing around the main truss gusset.

C. Travelers

Under bridge travelers, placed on rails that remain permanently on the bridge, can be considered onlarge steel structures. This is an expensive option but it should be evaluated for large bridges withhigh ADT as access to the bridge would be limited by traffic windows that specify when a lane can beclosed. Some bridges are restricted to weekend UBIT inspection for this reason.

4:P:BDM2

August 1998 2.4-1


Preliminary Design Selection of Structure Types

2.4 Selection of Structure Type

2.4.1 Bridge Types

The following superstructure depth to span ratios have been determined from past experience to bereasonable and economical and are in some cases less than the minimum depth recommended byAASHTO. In this situation, the Bridge Design Manual will govern. The length of span used to determinesuperstructure depth shall be the length between centerline of bearings. Do not use the length betweenpoints of dead load contraflexure as noted in AASHTO for design.

A. Reinforced Concrete Slab

l. Use

Used for simple and continuous spans up to 60 feet.

2. Characteristics

Design details and falsework relatively simple. Shortest construction time for any cast-in-placestructure. Correction for anticipated falsework settlement must be included in the dead loadcamber curve because of the single concrete pour.

3. Depth/Span Ratios

a. Constant depth

Simple spans 1/22Continuous spans 1/25

b. Variable depth

Adjust ratios to account for change in relative stiffness of positive and negative momentsections.

B. Reinforced Concrete Tee-Beam

1. Use

Used for continuous spans 30 feet to 60 feet. Has been used for longer spans with inclinedleg piers.

2. Characteristics

Forming and falsework is more complicated than flat slab. Construction time is longer than for aflat slab.


a. Constant depth


b. Variable depth


2.4-2 August 1998



C. Reinforced Concrete Box Girder

1. Use

Used for continuous spans 50 feet to 130 feet. Maximum simple span 110 feet to limit excessivedead load deflections.

2. Characteristics

Forming and falsework is somewhat complicated. Construction time is approximately the sameas for a tee-beam. High torsional resistance makes it desirable for curved alignments.

3. Depth/Span Ratios*

a. Constant depth


b. Variable depth


*If the configuration of the exterior web is sloped and curved, a larger depth/span ratio maybe necessary.

D. Post-Tensioned Concrete Box Girder

1. Use

Normally used for continuous spans longer than 130 feet or simple spans longer than 110 feet.Should be considered for shorter spans if a shallower structure depth is needed.

2. Characteristics

Construction time is somewhat longer due to post-tensioning operations. High torsionalresistance makes it desirable for curved alignments.

3. Depth/Span Ratios*

a. Constant depth

Simple spans 1/20.5Continuous spans 1/25

b. Variable depth

Two span structures@ Center of span 1/25@ Intermediate pier 1/12.5

Multispan structures@ Center of span 1/36@ Intermediate pier 1/18

*If the configuration of the exterior web is sloped and curved, a larger depth/span ratio maybe necessary.

August 1998 2.4-3



E. Prestressed Concrete Sections

1. Use

Local precast fabricators have several standard forms available for precast concrete sectionsbased on WSDOT standard girder series plans. They are versatile enough to cover a wide varietyof span lengths.

WSDOT standard girders are:

a. W74G, W58G, W50G, and W42G prestressed, concrete I-girders requiring a cast-in-placeconcrete roadway deck.

b. W53DG, and W35DG prestressed, concrete decked bulb tee girders requiring an ACPoverlay roadway surface.

c. 12-inch, 18-inch, and 26-inch precast prestressed slabs requiring an ACP overlay roadwaysurface.

d. 26-inch precast prestressed tribeam requiring an ACP overlay roadway surface.

2. Characteristics

Construction details and forming are fairly simple. Construction time is less than for acast-in-place bridge. Little or no falsework is required.

F. Composite Steel Plate Girder

1. Use

For simple spans up to 260 feet and for continuous spans from 120 to 400 feet. Relatively lowdead load when compared to a concrete superstructure makes this bridge type an asset in areaswhere foundation materials are poor.

2. Characteristics

Construction details and forming are fairly simple Construction time is comparatively short.Shipping and erecting of large sections must be reviewed. Cost of maintenance is higher than forconcrete bridges. Current cost information should be considered because of changing steelmarket conditions.


a. Constant depth


b. Variable depth

@ Center of span 1/40@ Intermediate pier 1/20

G. Composite Steel Box Girder

1. Use

For simple spans up to 260 feet and for continuous spans from 120 to 400 feet. Relatively lowdead load when compared to a concrete superstructure makes this bridge type an asset in areaswhere foundation materials are poor.

2.4-4 August 1998



2. Characteristics

Construction details and forming are more difficult than for a steel plate girder. Shipping anderecting of large sections must be reviewed. Current cost information should be consideredbecause of changing steel market conditions.


a. Constant depth


b. Variable depth


Sloping webs are not used on box girders of variable depth.

H. Steel Truss

1. Use

For simple spans up to 300 feet and for continuous spans up to 1,200 feet. Used where verticalclearance requirements dictate a shallow superstructure and long spans or where terrain dictateslong spans and construction by cantilever method.

2. Characteristics

Construction details are numerous and can be complex. Cantilever construction method canfacilitate construction over inaccessible areas. Through trusses are discouraged because of theresulting restricted horizontal and vertical clearances for the roadway.


a. Simple spans 1/6b. Continuous spans


I. Segmental Concrete Box Girder

1. Use

For continuous spans from 200 to 700 feet. Used where site dictates long spans and constructionby cantilever method.

2. Characteristics

Use of travelers for the form apparatus facilitates the cantilever construction method enablinglong-span construction without falsework. Precast concrete segments may be used. Tightgeometric control is required during construction to ensure proper alignment.


Variable depth


August 1998 2.4-5



J. Railroad Bridges

1. Use

For railroad undercrossings, most railroad companies prefer simple span steel construction. Thisis to simplify repair and reconstruction in the event of derailment or some other damage to thestructure.

2. Characteristics

The heavier loads of the railroad live load require deeper and stiffer members than for highwaybridges. Through girders can be used to reduce overall structure depth if the railroad concurs.Piers should be normal to the railroad to eliminate skew loading effects.


Constant depth

Simple spans 1/12Continuous two span 1/14Continuous multi-span 1/15

K. Timber

1. Use

Generally used for spans under 40 feet. Usually used for detour bridges and other temporarystructures.

2. Characteristics

Excellent for short-term duration as for a detour. Simple design and details.


Constant depth

Simple span – Timber beam 1/10Simple span – Glulam beam 1/12Continuous spans 1/14

L. Other

Bridge types such as cable-stayed, suspension, arch, tied arch, and floating bridges have special andlimited applications. Their use is generally dictated by site conditions. Preliminary design studies willgenerally be done when these types of structures are considered.

2.4.2 Wall Types

The process of selecting a type of retaining wall should economically satisfy structural, functional, andaesthetic requirements and other considerations relevant to a specific site. A detailed listing of thecommon wall types and their characteristics can be found in Section 9.4.2 of the Bridge Design Manual.

2:-4DTP:BDM2

August 1998 2.5-1


Preliminary Design Aesthetic Considerations

2.5 Aesthetic Considerations

2.5.1 General Visual Impact

A bridge can be a strong feature in any landscape. Steps must be taken to assure that even the most basicstructure will complement rather than detract from its surroundings. The Design Report, EIS, and bridgesite data submitted by the region should each contain a discussion on the aesthetic importance of theproject site. This commentary, along with the video and/or pictures submitted, will help the designerdetermine the appropriate structure. Generally a visit to the bridge site with the Bridge Architect and theregion will be made as well. The Bridge Architect should be contacted early in the preliminary bridge planprocess for input.

Aesthetics is a very subjective element that must be factored into the design process in the otherwise veryquantitative field of structural engineering. Bridges that are well proportioned structurally using the leastmaterial possible are generally well proportioned. However, the details such as pier walls, columns, andcrossbeams require special attention to ensure a structure that will enhance the general vicinity.

2.5.2 End Piers

A. Wing Walls

The size and exposure of the wing wall at the end pier should balance, visually, with the depth andtype of superstructure used. For example, a prestressed girder structure fits best visually with a15-foot wing wall (or curtain wall/retaining wall). However, there are instances where a 20-foot wingwall (or curtain wall/retaining wall) may be used with a prestressed girder (maximizing a span in aremote area, for example). These guidelines shall be used with engineering judgment and with thereview of the Bridge Architect.

It is less expensive for bridges of greater than 40 feet of overall width to be designed with wing walls(or curtain wall/retaining wall) than to use a longer superstructure.

B. Retaining Walls

For structures at sites where profile, right of way, and alignment dictate the use of high exposedwall-type abutments for the end piers, retaining walls that flank the approach roadway can be used toretain the roadway fill and reduce the overall structure length. Stepped walls are often used to breakup the height, and allow for landscape planting. A curtain wall runs between the bridge abutment andthe heel of the abutment footing. In this way, the joint in the retaining wall stem can coincide with thejoint between the abutment footing and the retaining wall footing. This simplifies design and providesa convenient breaking point between design responsibilities if the retaining walls happen to be theresponsibility of the region. The length shown for the curtain wall dimension is an estimated dimen-sion based on experience and preliminary foundation assumptions. It can be revised under design tosatisfy the intent of having the wall joint coincide with the end of the abutment footing.

C. Slope Protection

The region is responsible for making initial recommendations regarding slope protection. It should becompatible with the site and should match what has been used at other bridges in the vicinity. Thetype selected shall be shown on the Preliminary Plan. It shall be noted on the “Not Included in BridgeQuantities” list.

2.5-2 August 1998


Preliminary Design Aesthetic Considerations

2.5.3 Intermediate Piers

The size, shape, and spacing of the intermediate pier elements must satisfy two criteria. They must becorrectly sized and detailed to efficiently handle the structural loads required by the design and shaped toenhance the aesthetics of the structure.

The primary view of the pier must be considered. For structures that cross over another roadway, theprimary view will be a section normal to the roadway. This may not always be the same view as shown onthe Preliminary Plan as with a skewed structure, for example. This primary view should be the focus ofthe aesthetic review.

Tapers and flairs on columns should be kept simple and structurally functional. Fabrication andconstructibility of the formwork of the pier must be kept in mind. Crossbeam ends should be carefullyreviewed. Skewed bridges and bridges with steep profile grades or those in sharp vertical curves willrequire special attention to detail.

Column spacing should not be so small as to create a cluttered look. Column spacing should beproportioned to maintain a reasonable crossbeam span balance.

2.5.4 Barrier and Wall Surface Treatments

A. Plain Surface Finish

This finish will normally be used on structures that do not have a high degree of visibility or whereexisting conditions warrant. A bridge in a remote area or a bridge among several existing bridges allhaving a plain finish would be examples.

B. Fractured Fin Finish

This finish is the most common and an easy way to add a decorative texture to a structure. Variationson this type of finish can be used for special cases. The specific areas to receive this finish should bereviewed with the Bridge Architect.

C. Pigmented Sealer

The use of a pigmented sealer can also be an aesthetic enhancement. The particular hue can beselected to blend with the surrounding terrain. Most commonly, this would be considered in urbanareas. The selection should be reviewed with the Bridge Architect and the region.

2.5.5 Superstructure

The horizontal elements of the bridge are perhaps the strongest features. The sizing of the structure depthbased on the span/depth ratios in Section 2.4.1, will generally produce a balanced relationship.

Haunches or rounding of girders at the piers can enhance the structure’s appearance. The use of suchfeatures should be kept within reason considering fabrication of materials and construction of formwork.The amount of haunch should be carefully reviewed for overall balance from the primary viewingperspective.

The slab overhang dimension should approach that used for the structure depth. This dimension should bebalanced between what looks good for aesthetics and what is possible with a reasonable slab thickness andreinforcement.

For box girders, the exterior webs can be sloped. The amount of slope should not exceed l1/2: l forstructural reasons. Sloped webs should only be used in locations of high aesthetic impact.

DP:BDM2

August 1998 2.6-1


Preliminary Design Miscellaneous

2.6 Miscellaneous

2.6.1 Structure Costs

Historical bridge and structure cost data is outlined in Chapter 12. When using this data for cost estimates,the cost range assumed shall be based on the amount of information available. Unless foundation condi-tions are known, the worst case conditions would be assumed (e.g., pile foundations) for cost analysis. Anestimate contingency of 10 percent (minimum) staff be added to all preliminary bridge plan estimates. Forsmall projects or remote areas, high-range costs would be used. The cost data would be adjusted forinflation to the current date. Estimates include mobilization but not sales tax, engineering, future inflation,or contingencies, and the accuracy of the estimate is ±15 percent.

2.6.2 Handling and Shipping Precast Members and Steel Beams

Bridges utilizing precast concrete beams or steel beams need to have their access routes checked and sitesreviewed to be certain that the beams can be transported to the site. It must also be determined that theycan be erected once they reach the site.

Both the size and the weight of the beams must be checked. Likely routes to the site must be adequate tohandle the truck and trailer hauling the beams. Avoid narrow roads with sharp turns, steep grades, and/orload-rated bridges which may prevent the beams from reaching the site. The Condition Survey Section ofthe Bridge and Structures Office should be consulted for limitations on hauling lengths and weights.

The site should be reviewed for adequate space for the contractor to set up the cranes and equipmentnecessary to pick up and place the girders. The reach and boom angle should be checked and shouldaccommodate standard cranes.

2.6.3 Salvage of Materials

When a bridge is being replaced or widened, the material being removed should be reviewed for anythingthat WSDOT may want to salvage. Items such as aluminum rail, luminaire poles, sign structures, and steelbeams should be identified for possible salvage. The region should be asked if such items are to besalvaged since they will be responsible for storage and inventory of these items.

DP:BDM2

August 1998 2.7-1



2.7 WSDOT Standard Highway Bridge

2.7.1 Design Elements

The following are standard design elements for highway undercrossings and overcrossings. They aremeant to provide a generic base for consistent, clean looking bridges, and to reduce design and construc-tion costs. Modification of some elements may be required, depending on site conditions. This should bedetermined on a case-by-case basis during the preliminary plan stage of the design process.

A. General

Fractured Fin Finish shall be used on the exterior face of the traffic barrier. All other surfaces shall bePlain Surface Finish.

Exposed faces of wingwalls, columns, and abutments shall be vertical. The exterior face of the trafficbarrier and the end of the intermediate pier crossbeam and diaphram shall have a 1:12 backslope.

B. Substructure

End piers use the following details:

15′-0″ wingwalls (Standard Cadd File WW15_21.FGB).

Stub abutment wall with vertical face. Footing elevation, pile type (if required), and setbackdimension are determined from recommendations in the WSDOT Materials LaboratoryFoundation Report.

Intermediate piers use the following details:

“Semi-drop” Crossbeams: The crossbeam below the girders is designed for the girder and slabdead load, and construction loads. The crossbeam and the hinge diaphram together are designedfor all live loads and composite dead loads. The crossbeam shall be 3′-0″ minimum depth.

Round Columns: Columns shall be 3′-0″ or 4′-0″ in diameter. Dimensions are constant full heightwith no tapers. Bridges with roadway widths of 28′-0″ or less will generally be single columnpiers. Bridges with roadway widths of greater than 28′-0″ shall have two or more columns,following the criteria established in Section 2.3.1 H.

C. Superstructure

Concrete Slab: 712 ″ minimum thickness, with the top mat being epoxy coated steel reinforcing bars.

Prestressed Girders: Girder spacing will vary depending on roadway width and span length. The slaboverhang dimension is approximately half of the girder spacing. Girder spacings typically rangebetween 6′-0″ and 8′-0″.

W74G spans up to about 132″. (Standard Cadd File W74G.FGB).

W58G spans up to about 110′. (Standard Cadd File W58G.FGB).

Intermediate Diaphrams: Locate at the midspan for girders up to 80′ long. Locate at third points forgirders over 80′ long. (Standard Cadd File DIA63A5.FGB).

End Diaphrams: “End Wall on Girder” type. (Standard Cadd File DIA63A5.FGB).

Traffic Barrier: New Jersey face barrier. (Standard Cadd File TB.FGB).

2.7-2 August 1998



Hinge Diaphram: Full width of crossbeam between girders and outside of the exterior girders.Exterior face is flush with the end of the crossbeam and matches the 1:12 slope of the crossbeam face.(Standard Cadd File TO BE DEVELOPED).

BP Rail: 3′-6″ overall height for pedestrian traffic. 4′-6″ overall height for bicycle traffic. (StandardCadd File BPRAIL.FGB).

Sidewalk: 6″ height at curb line. Transverse slope of -.01′ per foot towards the curb line. (StandardCadd File PED_BAR.FGB).

Sidewalk barrier: Inside face is vertical. Outside face slopes 1:12 outward. (Standard Cadd FilePED_BAR.FGB).

D. Examples

Appendices 2.7-A1 and A2 detail the standard design elements of a standard highway bridge.

The following bridges are good examples of a standard highway bridge. However, they do have somemodifications to the standard.

SR 17 Undercrossing 395/110 Contract 3785Mullenix Road Overcrossing 16/203E&W Contract 4143

DTP:BDM2

August 1998 2.99-1


Preliminary Design Bibliography

2.99 Bibliography

1. Federal Highway Administration (FHWA) publication Federal Aid Highway Program Manual.

FHWA Order 5520.1 (dated December 24, 1990) contains the criteria pertaining to Type, Size, andLocation studies.

Volume 6, Chapter 6, Section 2, Subsection 1, Attachment 1 (Transmittal 425) contains the criteriapertaining to railroad undercrossings and overcrossings.

2. Washington Utilities and Transportation Commission Clearance Rules and Regulations GoverningCommon Carrier Railroads.

3. American Railway Engineering Association (AREA) Manual for Railroad Engineering. Note: This isthe criteria which we follow except as superseded by FHWA or WSDOT criteria. This manual is usedas the basic design and geometric criteria by all railroads.

4. Washington State Department of Transportation (WSDOT) Design Manual (M 22-01).

5. Local Agency Guidelines (M 36-63).

6. American Association of State Highway and Transportation Officials (AASHTO) StandardSpecifications for Highway Bridges.

DTP:BDM2

August 1998 2.2-A1

Bridge Site DataGeneral


Vicinity Map

Bridge Site Contour Map

Specific Roadway sections at bridge site and approved roadway sections

Vertical Profile Data

Horizontal Curve Data

Superelevation Transition Diagrams

Photographs and video tape of structure site, adjacent existing structures and surrounding terrain

Attachments

Structure width between curbs ?

Will the structure be widened in acontract subsequent to this contract ?

Which side and amount ?

Can a pier be placed in the median?

What is the required vertical clearance?

Can profile be revised to provide greateror less clearance?

If Yes, which line and how much?

Yes No N/A

Yes No N/A

Yes No N/A

Are sidewalks to be provided?

If Yes, which side and width?

Will sidewalks carry bicycle traffic?

Can the R/W be adjusted to accommodate toe of approach fills?

What is the available depth for superstructure?

Are overlays planned for a contract subsequent to this contract ?

Will signs or illumination be attached to the structure?

Yes No N/A

Yes No N/A

Yes No N/A

Yes No N/A

Yes No N/A

SR Control Section Project No.

Region Made By Date

Bridge InformationBridge Name

Highway Section Section, Township & Range Datum

Should the additional clearance for off-track railroad maintenanceequipment be provided?

Will the roadway under the structure be widened in the future?

Stage construction requirements ?

Are there detour or shoofly bridge requirements?(If Yes, attach drawings) Yes No N/A

What are the required falsework or construction opening dimensions ?

Yes No N/A

Will bridge be contracted before, with or after approach fill?

Before With After N/A

When can foundation drilling be accomplished?

What are expected foundation conditions?

Furnish type and location of existing features within the limits of thisproject, such as retaining walls, sign support structures, utilities,buildings, powerlines, etc.

Is slope protection or riprap required for the bridge end slopes?

Yes No N/A

Any other data relative to selection of type, including yourrecommendations?

Yes No N/A

Will utility conduits be incorporated in the bridge?

Yes No N/A

What do the bridge barriers transition to?

Tabulated field surveyed and measured stations, offsets, and elevations of existing roadways


Preliminary Design Bridge Site Data General

2.2-A2 August 1998

DOT Form 235-002A EFRevised 3/97

Right of

Thickness

Roadway deck elevations at curb lines (10-foot spacing)

Existing drains to be plugged, modified, moved, other?

Proposed overlay (ACP, ACP w /membrame, LMC, epoxy) Thickness

Yes NoIs bridge rail to be modified?

Existing rail type

Proposed rail replacement type

Yes NoWill terminal design “F” be required?

Yes NoWill utilities be placed in the new barrier?

Existing roadway width, curb to curb CLLeft of CL

Proposed roadway width, curb to curb CLLeft of Right of CL

Existing wearing surface (concrete, ACP, ACP w /membrane, LMC, epoxy, other)

Will the structure be overlayed with or after rail replacement? With Rail Replacement After Rail Replacement

Condition of existing joints

Yes NoExisting joints watertight?

Inch Inch Inch

Estimate structure temperature at time of joint measurement

Type of existing joint

Describe damage, if any, to existing joints

Existing Vertical Clearance

Video tape of project

Photographs of existing joints.

Measure width of existing joint, normal to skew.

CL@@ curb line @ curb lineroadway

Sketch indicating points at which joint width was measured.

Proposed Vertical Clearance (at curb lines of traffic barrier)

Attachments

Existing deck chloride and detamination data.

Bridge Information

Bridge Site DataRehabilitation


Region Made By Date

Bridge Name



Preliminary Design Bridge Site Data Rehabilitation

August 1998 2.2-A3

Bridge Information

Bridge Site DataStream Crossings


Stream Velocity Depth of Flow

Streambed Material

Amount and Character of Drift


Region Made By Date

Name of Stream Tributary of

Max Highwater Elevation

Normal Highwater Elevation

Extreme Low Water Elevation

Elevation of W.S.

Other Data Relative to Selection of Type and Design of Bridge, Including your Recommendations (i.e., requirements ofriprap, permission of piers in channel, etc.)

Manning’s “N” Value (Est.)

Highway Alignment and Profile (refer to map and profiles)

Streambed: Profile and Cross Sections (500 ft. upstream and downstream)

Photographs

Character of Stream Banks (i.e., rock, silt, etc.) / Location of Solid Rock

Bridge Name


Site Contour Map (See Sect. 7.02.00 Highway Hydraulic Manual)

Normal Stage Elevation

@ Date

@ Date

@ Date

@ Date

(@ date of survey) (fps @ date of survey) (@ date of survey)

Datum (i.e., USC and GS, USGS, etc.)

Attachments


Preliminary Design Bridge Site Data Stream Crossings

2.2-A4 August 1998

Project__________________ SR______ Prelim. Plan by _____ Check by _____ Date_____

PRELIMINARY PLAN CHECKLIST

PLAN___Survey Lines and Station Ticks___Survey Line Intersection Angles___Survey Line Intersection Stations___Survey Line Bearings___Roadway and Median Widths___Lane and Shoulder Widths___Sidewalk Width___Connection/Widening for Guardrail/Barrier___Profile Grade and Pivot Point___Roadway Superelevation Rate (if constant)___Lane Taper and Channelization Data___Traffic Arrows___Mileage to Junctions along Mainline___Back to Back of Pavement Seats___Span Lengths___Lengths of Walls next to/ part of Bridge___Pier Skew Angle___Bridge Drains, or Inlets off Bridge___Existing drainage structures___Existing utilities Type/Size, and Location___New utilities - Type, Size, and Location___Luminaires, Junction Boxes, Conduits___Bridge mounted Signs and Supports___Contours___Top of Cut: Toe of Fill___Bottom of Ditches___Test Holes (if available)___Riprap Limits___Stream Flow Arrow___R/W Lines and/or Easement Lines___Points of Minimum Vertical Clearance___Horizontal Clearance___Exist. Bridge No. (to be removed, widened)___Section, Township, Range___City or Town___North Arrow___SR Number___Bearing of Piers, or note if radial

MISCELLANEOUS___Structure Type___Live Loading___Undercrossing Alignment Profiles/Elevs.___Superelevation Diagrams___Curve Data___Riprap Detail___Layout Approval Block___Notes to Region___Names and Signatures___Not Included in Bridge Quantities List___Inspection and Maintenance Access

ELEVATION___Full Length Reference Elevation Line___Existing Ground Line x ft. Rt of Survey Line___End Slope Rate___Slope Protection___Pier Stations and Grade Elevations___Profile Grade Vertical Curves___BP/Pedestrian Rail___Barrier/Wall Face Treatment___Construction/Falsework Openings___Minimum Vertical Clearances___Water Surface Elevations and Flow Data___Riprap___Seal Vent Elevation___Datum___Grade elevations shown are equal to …___For Embankment details at bridge ends …___Indicate F, H, or E at abutments and piers

TYPICAL SECTION___Bridge Roadway Width___Lane and Shoulder Widths___Profile Grade and Pivot Point___Superelevation Rate___Survey Line___Overlay Type and Depth___Barrier Face Treatment___Limits of Pigmented Sealer___BP/Pedestrian Rail dimensions___Stage Construction Lane Orientations___Locations of Temporary Concrete Barrier___Closure Pour___Structure Depth/Prestressed Girder Type___Conduits/Utilities in bridge___Substructure Dimensions

LEFT MARGIN___Job Number___Bridge (before/with/after) Approach Fills___Structure Depth/Prestressed Girder Type___Deck Protective System___Coast Guard Permit Status___Railroad Agreement Status___Points of Minimum Vertical Clearance___Cast in Place Concrete Strength

RIGHT MARGIN___Control Section___Project Number___Region___Highway Section___SR Number___Structure Name


Preliminary Design Preliminary Plan Checklist

January 1991 2.3-A1


Preliminary Design Bridge Stage Construction Comparison


Analysis Contents

Page

3.0 Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.1-1

3.1 General Considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

3.1.1 Philosophy of Analysis Procedures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

3.1.2 Analysis Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

3.2 Frame Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . *

3.2.1 Theory . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . *

3.2.2 Member and Frame Factors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . *

3.2.3 Partial Fixity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.2-1

3.2.4 Development of F.E.M.s and Distribution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . *

3.2.5 Influence Lines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . *

3.3 Sidesway . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . *

3.4 Trusses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . *

3.5 Computer Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . *

3.5.1 General Discussion of Computer Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . *

3.5.2 List of Programs Available . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . *

3.6 Other Analysis Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . *

3.6.1 Energy Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . *

3.6.2 Castiglano . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . *

3.6.3 Virtual Work . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . *

3.6.4 The Buckling Problem . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . *

3.6.5 Finite Element . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . *

3.7 Dynamic Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . *

3.8 Special Analysis Problems by Bridge Type . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . *

3.8.1 Suspension bridges . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . *

3.8.2 Cable Stayed Bridges . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . *

3.9 Special Problems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . *

3.9.1 Skew . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . *

3.9.2 Footing Deflections and Rotations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . *

Appendix A

3.0-A1 Concentrated Load Coefficients — General3.0-A2 Concentrated Load Coefficients — Case I

3.0-A3 Fixed End Moment Coefficient Chart

3.0-A4 Influence Lines — Two Equal Spans3.0-A5 Coefficients and Factors for Double Tapered Members

3.0-A6 Stiffness Factors for Tapered Members

3.0-A7 Carry Over Factors for Tapered Members3.0-A8 Fixed End Moments for Tapered Members

*Indicates sections not issued to date.

3-CON:V:BDM3

July 1994 3.0-i


Analysis General Considerations

3.0 Analysis

3.1 General Considerations

3.1.1 Philosophy of Analysis Procedures

For the design of concrete bridges, in distribution of moments, generally use the gross moment of inertiaof the concrete superstructure. In lieu of including the transformed area of steel for columns or othercompression members, 120 percent of the gross moment of inertial of columns and other compressionmembers may generally be used.

3.1.2 Analysis Methods

The maximum live load deflection computed shall be in accordance with AASHTO except that the maxi-mum live load deflection in a span shall not exceed 1/1000 and for a cantilever 1/375, regardless ofwhether the bridge is used by pedestrians.

3-1:V:BDM3

July 1994 3.1-1


Analysis Frame Analysis

3.2.1 Theory (Vacant)

3.2.2 Member and Frame Factors (Vacant)

3.2.3 Partial Fixity

In general, assume 50 percent fixity of footings except footings on rock shall be 100 percent fixed. Forframe analysis, the point of fixity shall normally be taken to be at the approximate center line of footing.For column design, Volume 2 Sheets 9-220 through 9-225 shall be consulted. This shall hold for footingswith or without seals. Where superstructures are supported directly on piles, for analyses of the structurethe piles may be assumed fixed at a point 5 feet to 10 feet in the ground. For flat slab bridges supportedon piling, the piles shall be assumed pinned at the tops. For design of structures with large diametershafts see Section 9.8

For one column piers assume the footing fully fixed in the direction transverse to the roadway. For loadson one column piers assume the pier acts transversely as a simple cantilever, fixed at the footing, with noallowance for torsional, or lateral stiffness of the superstructure.

3-2:V:BDM3

July 1994 3.2-1

July 1994 3.0-A1


Concentrated LoadAnalysis Coefficients — General

3.0-A2 July 1994


Concentrated LoadAnalysis Coefficients — Case I


Fixed End MomentAnalysis Coefficient Chart

July 1994 3.0-A3-1


Fixed End MomentAnalysis Coefficient Chart

3.0-A3-2 July 1994

July 1994 3.0-A4


Influence Lines —Analysis Two Equal Spans

July 1994 3.0-A5-1


Coefficients and FactorsAnalysis for Double Tapered Members


Coefficients and FactorsAnalysis for Double Tapered Members

3.0-A5-2 July 1994

July 1994 3.0-A6


Stiffness FactorsAnalysis for Tapered Members

3.0-A7 July 1994


Carry Over FactorsAnalysis for Tapered Members

July 1994 3.0-A8-1


Fixed End MomentsAnalysis for Tapered Members


Fixed End MomentsAnalysis for Tapered Members

3.0-A8-2 July 1994

August 1998 4.0-i


Loads and Loading Contents

Page

4.0 Loads and Loading . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.1-1

4.1 Loads . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

4.1.1 Dead Loads . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

4.1.2 Live Loads . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1A. General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1B. Distribution to Superstructure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1C. Distribution to Substructure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

4.1.3 Wind Loads . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

4.1.4 Wind on Live Load . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

4.1.5 Earthquake Loads . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

4.1.6 Other Loads . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4A. Thermal, Shrinkage, and Prestressing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4B. Buoyancy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4C. Centrifugal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4D. Force from Stream Current, Floating Ice, and Drift . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

4.2 Load Combinations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.2-1

4.2.1 Combination of Loads . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

4.2.2 Load Factor Coefficients . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

4.2.3 Service Load Coefficients . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

4.3 Application of Loads . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.3-1

4.3.1 Dead Loads . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

4.3.2 Live Loads . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

4.3.3 Wind Loads . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

4.3.4 Earthquake Loads . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

4.4 Foundation Modeling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.4-1

4.4.1 Procedure Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

4.4.2 Spread Footings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

4.4.3 Pile Foundations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1A. Lateral Spring Input from P-Y Curves . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1B. Lateral Spring Input to Dynamic Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4C. Vertical Springs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7D. Stiffness Matrix . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8E. GPILE Computer Program . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

4.99 Bibliography . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.99-1

Appendix A4.4-A1-1 Foundation Design Seismic Flow Chart4.4-A2 Peak Ground Acceleration Map

Appendix B4.3-B1 Basic Truck Loading4.3-B2 Common Response Modification Factors4.3-B3 Seismic Analysis Example4.4-B1 Spring Constants Evaluation Example

P:DP/BDM4

August 1998 4.1-1


Loads and Loading Loads

4.0 Loads and Loading

AASHTO loading specifications shall be the minimum design criteria used for all bridges.

4.1 Loads

4.1.1 Dead Loads

Use values in AASHTO except as herein modified:

Reinforced Concrete — 160 pounds per cubic foot.

D.L. Forms in Top Slab of Concrete Box Girders — 5 pounds per square foot of cell area.

4.1.2 Live Loads

A. General

Live load design criteria is specified in the lower right corner of the bridge preliminary plan sheet.The Bridge Projects Unit determines this criteria using the following guideline:

• HS 25 — New bridges on the interstate or state system and bridge widenings involving additionof substructure.

• HS 20 — Bridge widenings with no addition of substructure.

• HS 15 — Detour bridges.

Use values described in AASHTO. Design for HS25 loading by multiplying HS20-44 axle loads by1.25. The loading consisting of two 24K axles at 4-foot centers sometimes governs for short spanbridges. See Figure 4.3.2-1 for illustration of this “alternative” loading.

See Figures 4.3.2-2 and 3 for “L” value to use in the formula in Section 4.3.2. Figure 4.3.2-2illustrates determination of the “L” length of the member under consideration. For beams and girders,use span length center to center of supports. For cantilevers, use length from center of support tofarthest load on cantilever. See Figure 4.3.2-2 for illustration.

B. Distribution to Superstructure

1. Integral Deck Precast Sections

The Live Load Distribution factor for Bulb Tee, Single Tee, and Double Tee bridges shall be asdetermined through use of the “DISTBM” computer program. (See Bridge Computer ProgramsManual.)

The AASHTO Specifications should be used for Rib Deck Bridges and the beam types listedtherein. For Rib Deck Bridges use a K value of 2.2.

Examples of beam types are shown on Figure 4.1.2-1.

2. Concrete Box Girders

The value for the number of traffic lanes to be used in the concrete box girder superstructuredesign shall be determined by dividing the entire roadway slab width by 14. Use fractional lanes,rounding to the nearest tenth of a foot, if applicable. Roadway slab widths of less than 28 feetshall have two design lanes. No reduction factor will be applied to the superstructure for multipleloadings.

4.1-2 August 1998



Beam TypesFigure 4.1.2-1

August 1998 4.1-3



3. Other Types

See AASHTO Specifications.

C. Distribution to Substructure

The value for the number of traffic lanes to be used in the substructure design shall be determinedby dividing the entire roadway slab width by 12. No fractional lanes shall be used. Roadwayslab widths of less than 24 feet shall have a maximum of two design lanes. A reduction factor will beapplied in the substructure design for multiple loadings in accordance with AASHTO. The followingpercentages of the resulting live loading shall be used:

Number of Lanes Loaded Percent

Two Lanes 100Three Lanes 90Four Lanes or More 75

4.1.3 Wind Loads

AASHTO load combinations for wind are based on probability of simultaneous load occurrence. Thebasic wind loads result from 100 mph wind, which produces 75 psf on trusses and arches, 50 psf ongirders and beams, and 40 psf on substructures. This wind is assumed to act on the structure when liveload is not present. A 30 mph wind (0.3 × 100, or a 70 percent reduction from basic) is included inGroups III and IV, and is assumed to act when live load is present.

The forces tending to overturn a structure are represented by an upward high wind pressure of 20 psfacting on the plan view area, for Groups II, V, and IX. A moderate wind pressure of 6 psf is used forGroups III and VI. The force is applied at the windward quarter point of the transverse superstructure.

4.1.4 Wind on Live Load

A moderate wind force is assumed to act on the live load itself, represented by a live load acting 6 feetabove the roadway surface, both transversely and longitudinally. This force is computed by multiplyingthe bridge length tributary to a particular member by 0.1 for transverse and 0.04 for longitudinal direction.

4.1.5 Earthquake Loads

a. Design for earthquake shall be in accordance with Division 1-A, Seismic Design of the 1996AASHTO Standard Specifications for Seismic Design of Highway Bridges.

b. The Multimode Spectral Method of dynamic analysis described in the AASHTO Specifications shallbe used for most continuous bridges. The SEISAB computer program can be used to analyze mostcommon bridges. The GTSTRUDL dynamic analysis system is capable of handling a larger range ofstructures.

c. The Single Mode Spectral Method may be used in certain cases, as described in the AASHTOSpecifications.

d. Use the USGS Peak Ground Acceleration map (Appendix 4.4-A2, 10 percent Probability ofExceedance in 50 Years) to obtain an acceleration coefficient for preliminary design. The projectFoundation Report will contain the acceleration coefficient to use in the final design of a bridge.When using Appendix 4.4-A2, interpolate between contours to find the value to use for particular site,and round to the nearest 1 percent of gravity (g). In general, Appendix 4.4-A2 can also be used for

4.1-4 August 1998



bridge seismic retrofit designs. However, seismic evaluation and retrofitting of older bridges cansometimes result in excessive costs (the retrofit costs are not consistent with the benefit gained). Inthese situations, the Bridge Design Engineer should be consulted for direction.

e. It is recommended that temporary (detour) structures shall be designed for a seismic accelerationcoefficient equal to 0.5 x the acceleration coefficient for a permanent structure. All other require-ments of the AASHTO Specifications for Seismic Design of Highway Bridges shall apply. SeismicPerformance Category shall be based on the magnitude of the reduced acceleration coefficient.

f. The Geotechnical Engineer should be consulted when determining the soil type to be used in theseismic analysis.

4.1.6 Other Loads

A. Thermal, Shrinkage, and Prestressing

Member loadings are induced by movements of the structure and can result from several sources.Movements due to temperature changes are calculated using coefficients of thermal expansion of0.000006 ft/ft per degree for concrete and 0.0000065 ft/ft per degree for steel. Reinforced concreteshrinks at the rate of 0.0002 ft/ft.

Refer to AASHTO and Bridge Design Manual Chapters 6, 8, and 9 for guidance on computation andapplication of these force types.

B. Buoyancy

The effects of submergence of a portion of the substructure is to be calculated, both for designingpiling for uplift and for realizing economy in footing design.

C. Centrifugal

Centrifugal forces are included in all groups which contain vehicular live load. They act 6 feet abovethe roadway surface and are significant where curve radii are small or columns are long. They areradial forces induced by moving trucks. See AASHTO for force equation.

August 1998 4.1-5



D. Force from Stream Current, Floating Ice, and Drift

In designing for stream flow force on piers, a reasonable area of drift or floating ice must bedetermined, considering the stream or river characteristics (check with the Hydraulics Unit). Waterdepth and pier spacing will partly determine drift areas.

W.S. = Water surface as defined by the Hydraulics Unit

SF = PdAd + PpAp

Ad = Area of drift or floating ice = D x E

Ap = Area of pier below ice = B x C. Where the pier is skewed to the stream, flow Cequals the width of the column normal to the stream flow.

V = Velocity of water (ft/sec)

Pd = Pressure on drift (psf) = 1.38 V2

Pp = Pressure on pier (psf) = KV2

In the absence of other data, the maximum values of D and E shall be 10 feet and 50 feet,respectively.

Water Related ForcesFigure 4.1.6-1

DP:BDM4

August 1998 4.2-1


Loads and Loading Load Combinations

4.2 Load Combinations

4.2.1 Combination of Loads

Group numbers represent various combinations of loads and forces which may act on a structure. Grouploading combinations for both Load Factor and Service Load Design are defined by the followingequation:

Group (N) = γ[βd D + βp PS + β

L (L+I) + β

c CF + β

E E + β

D B + β

s SF + β

w W + β

wL WL + β

L LF + β

R

(R + S + T) + βEQ

EQ + βICE

ICE]

where:

N = Group Numberγ = General Factorβ

N= Specific Factor

D = Dead Load (including overburden)PS = Prestress Load*L = Live LoadI = Live Load ImpactE = Earth Pressure (Lateral, only)B = BuoyancyW = Wind Load on StructureWL = Wind Load on Live Load — 100 pounds per linear foot of spanLF = Longitudinal Force from Live LoadCF = Centrifugal ForceR = Rib ShorteningS = ShrinkageT = TemperatureEQ = EarthquakeSF = Stream Flow PressureICE = Ice Pressure

*PS = Forces and moments transferred from members containing post-tensioning steel to othermembers upon application of the post-tensioning force.

Terms in the general equation that do not contribute to a particular combination are represented by zerosin the table.

4.2.2 Load Factor Coefficients

LFD requires basic design loads or related internal moments and forces to be increased by specified loadfactors, γ and β.

The γ factor is applied for stress control. Its common value is 1.3, which enables use of 77 percent of theultimate capacity. The 30 percent increase in design load represented by the factor is intended to accountfor variations in weight, reinforcement placement, structural behavior, and calculation of stress.

The β factor is a measure of the accuracy of load prediction and the probability of simultaneousapplication of loads in a combination.

Table 4.2.2-1 contains the terms and factors required to meet AASHTO Load Factor Design.

4.2-2 August 1998



Column Design

βD = 0.75 or bD = 1.0, whichever governs.

Flexural and Tension Members

βD = 1.0βE = 1.0

Footing Bearing Pressure and Internal Footing Stresses

βD = 0.75 or βD = 1.0βE = 1.0

Footing Stability and Sliding

βD = 0.75 or βD = 1.0, whichever governs.βE = 0.4 or βE = 1.3, whichever governs.

Notes:

1. For footing design, check Basic Loading Combination in accordance with BDM Section 9.5.1A3.a.

2. For rigid frame design, see BDM Section 9.3.4.E.

3. Check stability for all group loadings in accordance with BDM Section 9.5.1A3.b.

4. Group 1A load combination shall be applied only with live loadings less than HS 20 or H 20. SeeAASHTO.

*Applies if design loads are already factored, such as in cases where MDes

= 1.0 ML + 0.3 M

T or M

Des = 0.3

ML + 1.0 M

T are used.

Table of Coefficients γ and βFor Load Factor Design

Table 4.2.2-1

August 1998 4.2-3



4.2.3 Service Load Coefficients

Table 4.2.3-1 contains the terms and factors required to meet AASHTO Service Load Design. Theallowable percentage of the basic unit stress is given in the right hand column of the table.

Footing Bearing Pressure and Internal Footing Stresses

βE = 1.0

Footing Stability and Sliding

βE = 0.5 or βE = 1.0, whichever governs.

Notes:

1. For culvert loading, see AASHTO.

2. No increase in allowable unit stresses shall be permitted for members or connections carrying windload only.

Table of Coefficients γ and βFor Service Load Design

Table 4.2.3-1

4-2:P:BDM4

August 1998 4.3-1


Loads and Loading Application of Loads

4.3 Application of Loads

4.3.1 Dead Loads

Dead load is commonly applied to supports by assuming that it acts along each girder line.

4.3.2 Live Loads

The three types of live loadings ordinarily applied to a bridge when checking for maximum stresses in itscomponents are illustrated in AASHTO and Figure 4.3.2-1. The standard H-S truck represents commonvehicles. The lane load consists of combinations of uniform and concentrated loads which represent threelighter trucks spaced close together. The alternative loading represents certain heavy military vehicles.

The loading type governing the design depends on the structure configuration. For example, truck loadinggoverns for maximum moment in simple spans shorter than 145 feet and lane loading controls for longerspans. In continuous spans, lane loading governs for maximum negative moment, except for spans shorterthan 45 feet, in which truck loading will govern. The maximum positive moment in continuous spans isusually produced by using lane loading, for span lengths of over about 110 feet. Alternative loadinggoverns in certain short span situations.

Figures 4.3.2-2 and 4.3.2-3 illustrate application of loads to produce maximum stresses in various spanarrangements. Appendix 4.3-B1 illustrates calculation of reactions and maximum moments in a simplespan. Impact is figured using the following formula:

IL

=+50

125

Where L is the loaded portions of the spans.

Alternative (Military) LoadingFigure 4.3.2-1

4.3-2 August 1998



Application of LoadsFigure 4.3.2-2

August 1998 4.3-3



Application of LoadingFigure 4.3.2-3

4.3-4 August 1998



4.3.3 Wind Loads

Wind loads acting on the superstructure are based on the profile presented to the wind, the height of whichusually consists of the girder depth and traffic barrier height.

4.3.4 Earthquake Loads

Bibiography 1 through 4 contain several examples of applying earthquake loads to bridges. This sectionserves to amplify some analysis concepts.

Load factors applied in the Group VII combination are based on two concepts:

1. Full utilization of the elastic capacity of a particular element or member.

2. Taking advantage of the ductility or redundancy of the structure to absorb the energy released in anearthquake and keep the structure intact.

Two typical AASHTO load case equations are:

MEQ

= 1.0 ML

+ 0.3 MT

orM

EQ= 1.0 M

L+ 1.0 M

T

Where the moments are:

MEQ

= EarthquakeML = LongitudinalMT = Transverse

These equations are intended to satisfy concept 1. The SEISAB computer program prints out solutions tothe two equations as load cases 3 and 4.

Concept 2 is handled through use of the “R” factor. It appears in the factored loading equation:

Mu

= 1.0 (MDL

+ MEQ

/R)

The Guide Specification lists values for “R” for various structural components and types of supports.Some common examples are:

• Single column bents, considered ductile but nonredundant, R = 3 for both directions.

• Multi-column bents, considered ductile and redundant, R = 5 both ways.

• Wall-type piers, less ductile than single column bents, often having R = 2 for transverse behavior andR = 3 longitudinally.

• Footings, R = 1 for seismic performance Categories C and D and R = Rcol

for SPC B. Higher valuesare used than for columns and crossbeams because below ground structural damage is difficult to spotand repair. Plastic hinging moments are often less than those produced using an R of 1, so that someeconomy may be realized.

• Bearing type connections and stops, R = 0.8, due to lack of ductility and redundancy and because theyserve to prevent large displacements.

See Appendix 4.3-B2-1 and 2 for illustrations of common piers and appropriate factors to apply to themembers.

August 1998 4.3-5



In order to design structures to survive the forces and strains resulting from earthquake motion, thefollowing factors need to be considered:

• The proximity of the site to known active faults and the historical record of activity.

• The seismic response of the soil at the site.

• The dynamic response characteristics of the total structure.

See Appendix 4.3-B3-1 through 3 for a general discussion of a seismic analysis.

4-3:P:BDM4

August 1998 4.4-1


Loads and Loading Foundation Modeling

4.4 Foundation Modeling

Proper foundation modeling for earthquake loads is necessary because misinterpreted AASHTO Specifi-cations can lead to a wide range of member sizes. Realistic models will likely produce savings in material,especially when determining loads to apply to a substructure. Analysis is an iterative process whichconverges to an acceptable design.

4.4.1 Procedure Summary

Following is a workable procedure for analysis:

a. Assume the foundation as fixed (unless you know otherwise). Use SEISAB or GTSTRUDL toperform a dynamic analysis to determine initial loading.

b. If the support is not founded in rock, multiply the forces from the fully fixed model by 0.85 for theinitial trial design. Otherwise, use the fully fixed forces for the trial.

c. Determine a preliminary footing size, pile size, and arrangement, as applicable to the type of support.

d. Determine foundation springs as outlined in this section and Section 4.4.2. If pile support is beingused, see Section 4.4.3.E.

e. Rerun the dynamic model with springs included.

f. Compare loads and deflections using the same range used to determine the springs.

g. Redesign the footing, piles, adjust the springs, etc., until tolerable convergence is attained.

4.4.2 Spread Footings

a. You may apply load factor column moments from groups other than Group VII and column plastichinging moments for a first trial footing configuration. Then determine soil spring constants using thefooting plan area and depth of embedment. Assuming a shear wave velocity value, consult a Founda-tion or Geotechnical Engineer for an appropriate value.

b. Appendix 4.4-B1 through 4 illustrate a procedure to determine soil spring constants for spreadfootings.

4.4.3 Pile Foundations

A. Lateral Spring Input from P-Y Curves

Spring constants that represent pile supports may be obtained using a procedure which begins byapplying moments (as described in Section 4.4.1A) to an assumed footing and pile configuration. P-Ycurves from the foundation report may be input to the LPILE1 computer program to derive the initialspring constants.

The spacing between pile centers is often about 4 times the pile diameter (D), which means that eachpile in the group may deflect more than if it were acting alone. Apply efficiency factors, if providedon the soils report, to quantify that difference. If information is not available, use the following tableto estimate values.

4.4-2 August 1998



Efficiency FactorTable 4.4.3-1

For driven piles, the following factors apply:

Contact the Olympia Service Center Materials Lab to verify any assumptions.

The LPILE1 computer program will generate P-Y curves, or the user can input them. Toobtain generated curves, input a modulus of subgrade reaction (K), and a soil shear strength(C) which are the values taken from the soils report multiplied by the efficiency factor. Tofigure P-Y curves for input, multiply the P-Y values from the soils report by the efficiencyfactor.

For a typical soil, the relationship between its normalized resistance value and friction angleis defined by the curve in Figure 4.4.3-1. The friction angle could be adjusted for efficiencyand input to LPILE1 by following these steps:

1. Begin at the coordinate of the natural friction angle (36°).

2. Read across to the normalized resistance (61).

3. Multiply the resistance by the efficiency reduction factor, i.e., 61 (0.5) = 31.

4. Read across from the reduced value to obtain the adjusted friction angle (31°).

5. Input the φ value to LPILE1.

August 1998 4.4-3



Friction Angle (φ)

PS

b xγ = Ka (tan8B-1) + K

o tan φ tan 4B

PS

= Soil Resistance on Pile Element

b = Pile Width

g = Soil Unit Weight

X = Depth to Pile Element

N = Step in Example

B = 45° + φ/2

Ka

= tan2(45° – φ/2)

Ko

= 1 – Sin φFigure 4.4.3-1

4.4-4 August 1998



B. Lateral Spring Input to Dynamic Analysis

Lateral spring constants can be generated for input to SEISAB (or GTSTRUDL) by using LPILE1and two types of loading.

Case 1 — Applied Lateral Load — See Figure 4.4.3-2(A). Apply a lateral load (F) to the model of apile, and restrain its top against rotation. The load produces a deflected shape with the top deflectionbeing ∆. A moment (M) is also induced. F and M may be plotted against ∆ to produce two curves.The spring constants are defined as slopes of the curves, and their calculation and SEISABnomenclature are given by the equations in Figure 4.4.3-2(A).

Make enough LPILE1 runs to define a linear range along the lateral force versus a deflection curve.Vary axial loads, to bracket the values expected from the dynamic analysis (i.e., SEISAB results).Include negative axial loads to represent anticipated tension due to uplift effects.

Case 2 — Applied Moment — See Figure 4.4.3-2(B). Apply a moment (M) to the pile model,restraining the pile top against translation. Calculate the pile top rotation (φ) from the LPILE1 outputby dividing the deflection at the bottom of the top increment (∆

1) by the increment length (H

1). The

spring constants are defined as slopes of the curves, and they are calculated using the equations inFigure 4.4.3-2(B).

A rapid way to approximate the slope of any curve is to select a point at half of the ultimate lateralforce or moment capacity of the pile. Note that the off-diagonal terms must be equal and opposite insign.

Figure 4.4.3-3 contains examples of spring calculation from LPILE1 output.

August 1998 4.4-5



Figure 4.4.3-2B

Figure 4.4.3-2A

4.4-6 August 1998



Loading Number 1

Boundary condition code = 2Lateral load at the pile head = 0.250D+05 lbs = 25 K appliedSlope at the pile head = 0.000D+00 in/inAxial load at the pile head = 0.758D+05 lbs

X Deflection Moment Shear Soil Total FlexuralReaction Stress Rigidity

In In Lbs-In Lbs Lbs/In Lbs/In**2 Lbs-In**2

***** ********** ********** ********** ********** ********** **********

0.00 0.267D+01 -0.383D+07 0.250D+05 0.000D+00 0.270D+05 0.392D+11

=2.67″ =25K

KF1F1 = KF3F3 = 25

2 67 12112

K

in in ft

K

ft( . / / )=

(A)

Loading Number 1

Boundary condition code = 4Deflection at the pile head = 0.000D+00 inMoment at the pile head = 0.391D+07 in-lbs = 391 K-in appliedAxial load at the pile head = 0.103D+06 lbs

X Deflection Moment Shear Soil Total FlexuralReaction Stress Rigidity

In In Lbs-In Lbs Lbs/In Lbs/In**2 Lbs-In**2

***** ********** ********** ********** ********** ********** **********

0.00 0.000D+00 0.391D+07 0.189D+05 0.000D+00 0.281D+05 0.392D+1128.04 -0.237D+00 0.340D+07 -0.186D+05 0.208D+02 0.247D+05 0.392D+11

0.237″ = ∆1

28.04″ = H

f = Tan–1∆1

1H = Tan–10 237

28 04

.

. = 0.48426°

or = 0.00845 rad

(B)

Sample LPILE1 OutputFigure 4.4.3-3

August 1998 4.4-7



C. Vertical Springs

Vertical spring constants, Kv (or KF2F2) can be calculated from the following equations:

Point bearing pile: Kv =

AE

L

where,

A = Cross sectional areaE = Young’s modulusL = Length

Pile having constant skin friction:

Kv =

2AE

L

Pile linearly varying skin friction:

Kv =

3AE

L

Pile partially embedded in the soil:

1. Kv =

AEF

L12

−

2. Kv =

AEF

L123

−

4.4-8 August 1998



Torsional (M/φ) spring constants for individual piles are based on the strength of the pile only. Thetorsional resistance is given by the following equation:

M/φ = T/φ = JG/L

where,

G = 0.4 EJ = Torsional Moment of InertiaL = length of pile

D. Stiffness Matrix

Eight individual pile stiffness terms should be put into Seisab, which forms a {6 × 6} matrix as shownbelow:

F1 F2 F3 M1 M2 M3

F1 KF1F1 0 0 0 0 KF1M3F2 KF2F2 0 0 0 0F3 KF3F3 -KF3M1 0 0M1 KM1M1 0 0M2 KM2M2 0M3 "Symmetrical" KM3M3

KF1M3 is cross-coupling term P/φ. -KF3M1 is cross-coupling term M/d. Note that the two haveopposite signs.

E. GPILE Computer Program

If a large number of piles is required per footing, to reduce Seisab input/output, individual springs canbe used in the GPILE computer program. The output will contain a {6 × 6} stiffness matrix for thepile group which can be used to model the foundation in SEISAB. GPILE input includes pile configu-ration and spring constants. The program also computes individual pile loads and deflections from aset of input loads. GPILE can be used in conjunction with the plastic hinging moments, transmittedfrom the column, to converge on an acceptable pile configuration.

4-4:P:BDM4

August 1998 4.99-1


Loads and Loading Bibliography

4.99 Bibliography

1. AASHTO, Standard Specifications for Design of Highway Bridges, 1996, Division 1-A SeismicDesign.

2. Imbsen, R. A., Seismic Design of Highway Bridges, FHWA Workshop Manual, January 1981,DOT-FH-11-9426.

3. FHWA/RD-83/007 Seismic Retrofitting Guidelines for Highway Bridges, December 1983.

4. FHWA-IP-87-6, Seismic Design and Retrofit Manual for Highway Bridges, May 1987.

5. California Department of Transportation, Bridge Design Practice, 1983.

6. Chen, R. L., Pile Foundation Modeling for Bridge Dynamic Response Analysis, unpublished paperavailable in WSDOT Bridge and Structures Design, April 1987.

7. Engineering Computer Corporation, SEISAB-I, Workshop Manual, October 1984 and August 1985.

8. Reese, Lymon C., Documentation of Computer Program LPILE1, report for Ensoft, Inc., TheUniversity of Texas at Austin, 1985.

9. AASHTO, Standard Specifications for Highway Bridges, 1996.

10. Washington State Department of Transportation, Bridge Computer Programs Manual, GPILE andDISTBM.

11. Washington State Department of Transportation, 1996, USGS National Seismic Hazards, MappingProject.

12. Hart Crowser, Subsurface Explorations and Design Phase Geotechnical Engineering Study, SR 90,Seattle Access, Volume 111, September 1986, J-712-50.

13. Federal Highway Administration, Manual on Design and Construction of Driven Pile Foundations,FHWA-DD-66-1, Revision 1.

14. Imbsen & Associates, FHWA, Seismic Design of Highway Bridges Training Course ParticipantWorkbook, February 1989.

15. FHWA-86/103, Seismic Design of Highway Bridges, Vol. II: Example problems and SensitivityStudies, June 1986.

4-99:P:BDM4

August 1998 4.4-A1-1


Loads and Loading Foundation Design Seismic Flow Chart

4.4-A1-2 August 1998



August 1998 4.4-A1-3



4.4-A1-4 August 1998



August 1998 4.4-A1-5



4.4-A1-6 August 1998



August 1998 4.4-A1-7



4.4-A1-8 August 1998



August 1998 4.4-A1-9



4.4-A1-10 August 1998



August 1998 4.4-A2


Loads and Loading Peak Ground Acceleration Map

August 1998 4.3-B1

BRIDGE DESIGN MANUALAppendix B

Loads and Loading Basic Truck Loading

Basic Truck LoadingHS25

August 1998 4.3-B2-1


Loads and Loading Common Response Modification Factors

4.3-B2-2 August 1998


Loads and Loading Common Response Modification Factors

August 1998 4.3-B3-1


Loads and Loading Seismic Analysis Example

A recent analysis of a bridge on I-90 in the Mercer Slough area near Bellevue provides the followingexample:

The deep soft soil at the site is classified as “Type III” from the AASHTO Specifications. Anacceleration coefficient of 0.25, see Figure 4.1.5-1, was selected as appropriate.

The acceleration spectrum shown in Appendix 4.3-B3-2 was used to load the bridge. The results whichSEISAB calculated for the first 6 modes of oscillation appear in Appendix 4.3-B3-3. The CS values inthe table relate directly to the response periods of the various modes as solutions to the equation:

CS =

where:

A = The acceleration coefficient

S = The soil profile coefficient (1.5 in this case)

T = The period of vibration of the bridge, the time it takes for one cycle of oscillation

In an undamped, single degree of freedom system, the natural period is defined as:

T = π M

K

where:

M = The mass involved

K = The spring constant

See Bibliography 1 and 7 for further comments and procedures.

CS, the elastic seismic response coefficient, is the percentage of a gravity force which is applied to thebridge for a particular mode. The participation factors indicate that modes 1 and 3 contribute most heavilyto the design forces. In this case, the ground sends 0.25 g and the bridge receives about 0.50 g.

The 0.50 g applied, divided by R = 5, translates to 0.1 g when figuring design moments for a multiplecolumn bent. Design shears would be the lesser of the values produced by 0.50 g and the shears associatedwith plastic hinging moments. Since the column reinforcement may yield when the 0.1 g level is reached,the energy remaining will be redistributed to the remainder of the bridge. The main column reinforcementmust be adequately confined by ties or spirals to allow redistribution to occur while maintaining structuralintegrity.

P:DP/BDM4

1 22 3

./

AS

T

4.3-B3-2 August 1998



Example Seismic Analysis

August 1998 4.3-B3-3



Example Seismic Analysis (Continued)

August 1998 4.4-B1-1


Loads and Loading Spring Constants Evaluation Example

Given Data

• Cohesionless soil – Poisson’s ratio = 0.33 = µ

• Soil density – 120 pcf = σ

• VS = shear wave velocity = 1,500 ft/sec

Solution:

Shear Modulus

G= °Vs2 =

120 1 500

32 2 1000

2 lb/ft ft/sec

ft/sec Lb/

3

2 K

,

.( )

( )Vertical Stiffness

L/W; 1.0 1.5 2.0 3.0 5.0 10.0ß

Z; 2.12 2.14 2.18 2.26 2.44 2.82

L/W = 18

15 = 1.20 ß

Z = 2.13

KZ =

βµ

ZG LW

1− = 2 13 8385 18 15

1 0 33

.

.

× ×−

= 438,000 K

ft

Embedment Factor

ro =

KW

π =- 9.27′

H

ro

= 6

9 27. = 0.65

4.4-B1-2 August 1998



Vertical Stiffness — Modified

KZH

= 1.36 KZ = 1.36 × 438,000 = 596,000 kips/ft = KFY

Horizontal Stiffness

L

W = 1.20 < 5 ßx = 2.0 (See page 6-37 of Bilbliography 2 for explanation.)

KX = ß

X (1 – µ) G LW

= 2.0 (1 – 0.33) 8385 18 15× = 185,000 K/ft

Assuming that the horizontal embedment effect is the same as the vertical.

Horizontal Stiffness — Modified

KXH

= 1.85 × 105 1.36 = 2.5 × 105 K/ft = KFX = KFZ

August 1998 4.4-B1-3



Rocking Stiffness

Long Direction c = 7.5′ d = 9′

R = d

c = 1.20 ßψ = 0.52

R; 0.2 0.5 1.0 2.0 4.0 6.0 8.0ßψ; 0.4 0.45 0.5 0.6 0.8 0.95 1.1

Kψ = ßψ 8

1

2G cd ( )− µ

= 0 52 8 8385 7 5 9

1 0 33

2. .

.

× × × ×−

= 3.2 × 107 K ft

rad

−

KH = 1.36 (3.2 × 107) = 4.3 × 107

K ft

rad

− = KMZ

Short Direction

R = c

d = 0.83 ßψ = 0.48

Kψ = ßψ 8

1

2G dc( )− µ = 2.4 × 107

K ft

rad

−

= 0 48 8 8385 9 7 5

1 0 33

2. .

.

× × × ×−

Kψ H = 1.36 (2.4 × 107) = 3.3 × 107 K ft

rad

−

Torsional Stiffness

rc =

16

6

16 7 5 9 7 5 9

6

2 2

4

2 2

4cd c d+( )

=× × +( )

π π. .

Kθ = 16

3 Gr

e3 =

16

3 × 8385 × 9.423 = 3.7 × 107

K ft

rad

−

Kθ H = 1.36 (3.7 × 107) = 5.0 × 107 K ft

rad

− = KMY

Appendix 4.4-B1-4 depicts the footing from the example in spring matrix form. The nomenclature isgeneral, and is used for GTSTRUDL input (GTSTRUDL 4.2.2d contains a similar matrix usingSEISAB nomenclature).

4.4-B1-4 August 1998



Spring Matrix


Reinforced Concrete Superstructures Contents

July 2000 5.0-i

Page

5.0 Reinforced Concrete Superstructures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.1-1

5.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

5.1.1 Concrete and Grout . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1A. Classes of Concrete . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1B. Strength of Concrete . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1C. Grout . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

5.1.2 Reinforcement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3A. Grades . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3B. Sizes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3C. Development . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4D. Splices . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4E. Bends . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9F. Fabrication Lengths . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9G. Placement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10H. Percentage Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

5.2 Design Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.2-1

5.2.1 Strength Design Method . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1A. Design Philosophy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1B. Flexure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1C. Shear . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2D. Strut-and-Tie Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2E. Shear and Torsion, ACI Method . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7F. Shear and Torsion, Strut-and-Tie Method . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7G. Deflection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7H. Serviceability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

5.2.2 Working Stress Design Method . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

5.3 Reinforced Concrete Box Girder Bridges . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.3-1

5.3.1 Girder Spacing and Basic Geometries . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1A. Girder Spacing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1B. Basic Dimensions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1C. Construction Considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3D. Load Distribution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

5.3.2 Reinforcement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4A. Top Slab Reinforcement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4B. Bottom Slab Reinforcement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7C. Web Reinforcement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7D. Intermediate Diaphragm . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

5.3.3 Crossbeam . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13A. Basic Geometry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13B. Reinforcing Steel Details . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

5.3.4 End Diaphragm . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14A. Basic Geometry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14B. Reinforcing Steel Details . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

5.3.5 Dead Load Deflection and Camber . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16



5.0-ii July 2000

Page

5.3.6 Thermal Effects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17A. Effective Bridge Temperature and Movement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17B. Differential Temperature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

5.3.7 Hinges . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

5.3.8 Utility Openings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19A. Confined Spaces . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19B. Drain Holes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19C. Access Hole and Air Vent Holes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

5.4 Hinges and Inverted T-Beam Pier Caps . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.4-1A. Local Failure Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1B. Shear Friction Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4C. Flexural Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5D. Hanger Tension Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6E. Punching Shear Check . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7F. Bearing Strength Check . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

5.5 Widenings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.5-1

5.5.1 Review of Existing Structures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1A. General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1B. Original Contract Plans and Special Provisions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1C. Original Calculations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1D. Final Records . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

5.5.2 Analysis and Design Criteria . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2A. General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2B. Seismic Design Criteria for Bridge Widenings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4C. Substructure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5D. Superstructure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6E. Stability of Widening . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

5.5.3 Removing Portions of the Existing Structures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

5.5.4 Attachment of Widening to Existing Structure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7A. General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7B. Connection Details . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

5.5.5 Expansion Joints . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

5.5.6 Possible Future Widening for Current Designs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

5.5.7 Bridge Widening Falsework . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

5.5.8 Existing Bridge Widenings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

5.99 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.99-1



July 2000 5.0-iii

Appendix A Design Aids5.1-A1 Reinforcing Bar Properties5.1-A2 Bar Area vs. Bar Spacing5.1-A3 Bar Area vs. Number of Bars5.1-A4 Tension Development Length of Straight Deformed Bars5.1-A5 Tension Development Length of Standard 90° and 180° Hooks5.1-A6 Tension Lap Splice Lengths of Grade 60 Uncoated Bars5.1-A7 Minimum Development Length and Minimum Lap Splices of Deformed Bars

in Compression5.2-A1 ρ Values for Singly Reinforced Beams fc′ = 3,000 psi fy = 60,000 psi5.2-A2 ρ Values for Singly Reinforced Beams fc′ = 4,000 psi fy = 60,000 psi5.2-A3 ρ Values for Singly Reinforced Beams fc′ = 5,000 psi fy = 60,000 psi5.3-A1 Positive Moment Reinforcement5.3-A2 Negative Moment Reinforcement5.3-A3 Adjusted Negative Moment Case I (Design for M @ Face of Effective Support)5.3-A4 Adjusted Negative Moment Case II (Design for M @ 1/4 Point)5.3-A5 Load Factor Slab Design fc′ = 4,000 psi5.3-A6 Load Factor Slab Design fc′ = 5,000 psi5.3-A7 Slab Design — Traffic Barrier Load

Appendix B Design Examples5.2-B1 Slab Design5.2-B2 Slab Design for Prestressed Girders5.2-B3 Strut-and-Tie Design5.2-B4 Working Stress Design

P65:DP/BDM5


Reinforced Concrete Superstructures General

July 2000 5.1-1

5.0 Reinforced Concrete Superstructures

5.1 General

Prior to precast pretensioned and post-tensioned concrete members introduced in the early 1960s, all shortand medium span bridges were built as cast-in-place (CIP) reinforced concrete superstructures.

Examples of reinforced concrete superstructures are: flat slabs, slab and T-beams, arches, slabs for alltypes of steel bridges, and box girders.

Many of the bridges built before 1960 are functional, durable, and structurally sound. The service life ofsome of these early bridges can be extended by widening their decks to accommodate increased trafficdemand or to improve safety. This chapter addresses special requirements for widenings.

The design aids in this chapter can also be utilized in the design of nonprestressed reinforcement inprestressed structural elements and reinforced concrete substructures.

5.1.1 Concrete and Grout

A. Classes of Concrete

1. CLASS 3000

Used in large sections with light to nominal reinforcement, mass pours, sidewalks, curbs, gutters,and nonstructural concrete guardrail anchors, luminaire bases.

2. CLASS 4000

Used in traffic and pedestrian barriers, approach slabs, footings, box culverts, wing walls, curtainwalls, retaining walls, columns, and crossbeams.

3. CLASS 4000D

Used in bridge concrete decks. Standard specifications require two coats of curing compound anda continuous wet cure for 14 days.

4. CLASS 4000P

Used for cast-in-place pile and shaft.

5. CLASS 4000W

Used underwater in seals.

6. CLASS 5000 or Higher

Used in CIP post-tensioned concrete box girder construction or in other special structuralapplications situations. Use of CLASS 5000 or higher requires approval of the Bridge DesignEngineer, the Olympia Service Center, and Materials Lab. Place documentation in job file.

B. Strength of Concrete

1. The 28-day compressive design strengths (fc′) in pounds per square inch (psi) are:



5.1-2 July 2000

Class fc′

COMMERCIAL 23003000 3000

4000, 4000D 40004000W 2400*5000 5000**6000 60004000P 3400***

*40 percent reduction from CLASS 4000. **Concrete Class 5000 is available within a 30-mile radius of Seattle, Spokane, and Vancouver. Outside this 30-mile radius, concrete suppliers do not have the quality control rocedures and expertise to Supply Control Class 5000.***15 percent reduction from CLASS 4000 for all drilled shafts.

2. Relative Compressive Concrete Strength

a. During design or construction of a bridge, it is necessary to determine the strength ofconcrete at various stages of construction. For instance, Section 6-02.3(17)J of the StandardSpecifications discusses the time at which falsework and forms can be removed to variouspercentages of the concrete design strength. Occasionally, construction problems will arisewhich require a knowledge of the relative strengths of concrete at various ages. Table 5.1-1is intended to supply this information.

b. Curing conditions of the concrete (especially in the first 24 hours) have a very importantinfluence on the strength development of concrete at all ages. Temperature affects the rateat which the chemical reaction between cement and water takes place. Loss of moisture canseriously impair the concrete strength.

c. Table 5.1-1 shows the approximate values of the minimum compressive strengths of differ-ent classes of concrete at various ages. If the concrete has been cured under continuous moistcuring at an average temperature, it can be assumed that these values have been developed.

d. If test strength is above or below that shown in Table 5.1-1, the age at which the designstrength will be reached can be determined by direct proportion.

For example, if the relative strength at 10 days is 64 percent instead of the minimum70 percent shown in Table 5.1-1, the time it takes to reach the design strength can bedetermined as follows:

Let x = relative strength to determine the age at which the concrete will reachthe design strength

Therefore, x = 110

From Table 5.1-1, the design strength should be reached in 40 days.

C. Grout

Grout is usually a prepackaged cement based grout or nonshrink grout that is mixed, placed, andcured as recommended by the manufacturer. It is used under steel base plates for both bridge bearingsand luminaire or sign bridge bases. Nonshrink grout is used in keyways between precast prestresseddeck slabs, tri-beams, and bulb-tees. For design purposes, the strength of the grout, if properly cured,can be assumed to be equal to or greater than that of the adjacent concrete.

Should the grout pad thickness exceed 4 inches, steel reinforcement shall be used.

x 10070 64

=



July 2000 5.1-3

The following chart shows approximate relative strength of concrete and compressive strength of differentclasses of concrete at various ages based on continuous moist curing at an average temperature.

Relative and Compressive Strength of ConcreteTable 5.1.1-1

5.1.2 Reinforcement

A. Grades

Steel reinforcing bars are manufactured as plain or deformed bars (which have ribbed projections thatgrip the concrete in order to provide better bond between steel and concrete). In Washington State,main bars are always deformed. Plain bars are used for spirals and ties.

Reinforcing bars conform to either the requirements of AASHTO M31, Grade 60 (ASTM A-615Grade 60) with a 60,000 psi yield strength or in the case of bars in portions of concrete memberswhere plastic hanging can occur during an earthquake or which are to be spliced by welding,ASTM A 706 Specifications for Low-Alloy Steel deformed Bars for Concrete Reinforcement.

B. Sizes

Reinforcing bars are referred to in the contract plans and specifications by number and vary insize from #3 to #18. For bars up to and including #8, the number of the bar coincides with the bardiameter in eighths of an inch. The #9, #10, and #11 bars have diameters that provide areas equalto 1″ x 1″ square bars, 11/8″ x 11/8″ square bars and 11/4″ x 11/4″ square bars respectively. Similarly,the #14 and #18 bars correspond to 11/2″ x 11/2″ and 2″ x 2″ square bars, respectively. Tables 5.1-A1through 5.1-A3 in Appendix A, show the sizes, number, and various properties of the types of barsused in Washington State.

Relative Class Class ClassAge Strength 5000 4000 3000

(Days) (%) (psi) (psi) (psi)

3 35 1750 1400 10504 43 2150 1720 12905 50 2500 2000 15006 55 2750 2200 16507 59 2950 2360 17708 63 3150 2520 18909 67 3350 2680 2010

10 70 3500 2800 210011 73 3650 2920 219012 75 3750 3000 225013 77 3850 3080 231014 79 3950 3160 237015 81 4050 3240 243016 83 4150 3320 249017 85 4250 3400 255018 87 4350 3480 261019 89 4450 3560 2670

Relative Class Class ClassAge Strength 5000 4000 3000

(Days) (%) (psi) (psi) (psi)

20 91 4550 3640 273021 93 4650 3720 279022 94 4700 3760 282023 95 4750 3800 285024 96 4800 3840 288025 97 4850 3880 291026 98 4900 3920 294027 99 4950 3960 297028 100 5000 4000 300030 102 5100 4080 306040 110 5500 4400 330050 115 5750 4600 345060 120 6000 4800 360070 125 6250 5000 375080 129 6450 5160 387090 131 6550 5240 3930



5.1-4 July 2000

C. Development

1. Development Length, ld, in Tension

Development length or anchorage of reinforcement is required on both sides of a point ofmaximum stress at any section of a reinforced concrete member.

Development of bars in tension involves calculating the basic development length, ldb, whichis modified by factors to reflect bar spacing, cover, enclosing transverse reinforcement, topbar effect, type of aggregate, epoxy coating, and ratio of required area to provided area ofreinforcement to be developed.

The development length, ld (including all applicable modification factors) must not be lessthan 12 inches.

Tables 5.1-A4 and 5.1-A5 in Appendix A, show the tension development length for both un-coated and epoxy coated Grade 60 bars for normal weight concrete with specified strengths of3,000 to 6,000 psi.

2. Development Length, ld, in Compression

The basic development lengths for deformed bars in compression are shown in Table 5.1-A7,Appendix A. These values may be modified for ratio of required area vs. provided area ofreinforcement, or for bars enclosed in a 1/4 inch diameter spiral at 4 inch maximum pitch.However, the minimum development length is 1 foot 0 inches (office practice).

3. Standard End Hook Development Length, ldh, in Tension

Standard end hooks, utilizing 90 and 180 degree end hooks, are used to develop bars in tensionwhere space limitations restrict the use of straight bars. End hooks on compression bars are noteffective for development length purposes. Figures 5.1.2-1 and 5.1.2-2 and Table 5.1.2-1 showthe minimum embedment lengths necessary to provide 2 inches of cover on the tails of 90 and180 degree end hooks. Epoxy coating does not affect the tension development lengths, ldh, ofstandard 90 and 180 degree end hooks. The values shown in Table 5.1-1A5, Appendix A, showthe tension development lengths for normal weight concrete with specified strengths of 3,000 to6,000 psi.

D. Splices

Three methods are used to splice reinforcing bars; lap splices, mechanical splices, and welded splices.Lap splicing of reinforcing bars is the most common method. The Contract Plans should clearly showthe locations and lengths of lap splice. Lap splices are not permitted for bars larger than #11.

No lap splices, for either tension or compression bars, shall be less than 2 feet 0 inches (officepractice). See Section 8.32 of the Standard Specifications for Highway Bridges and Section6-02.3(24)D Standard Specifications for additional splice requirements.

1. Lap Splices — Tension

Many of the same factors which affect development length affect splices. Consequently, tensionlap splices are a function of the bar’s development length, ld. There are three classes of tensionlap splices: Class A, B, and C. Designers are encouraged to splice bars at points of minimumstress and to stagger lap splices along the length of the bars.



July 2000 5.1-5

Minimum Embedment Lengths to Provide 2-inch Cover to Tail of Standard 180° End HooksTable 5.1.2-1

#3 #4 #5 #6 #7 #8 #9 #10 #11 #14 #18

6″ 7″ 9″ 10″ 1′-0″ 1′-2″ 1′-3″ 1′-5″ 1′-7″ 2′-10″ 3′-7″

Standard 180° and 90° End HooksFigure 5.1.2-1

Special Confinement for 180° and 90° End HooksFigure 5.1.2-2



5.1-6 July 2000

Recommended End HooksTable 5.1.2-2



July 2000 5.1-7

Figure 5.1.2-3



5.1-8 July 2000

Figure 5.1.2-4

(a)

(b)

(c)



July 2000 5.1-9

Table 5.1A6 in Appendix A, shows tension lap splices for both uncoated and epoxy coatedGrade 60 bars for normal weight concrete with specified strengths of 3,000 to 6,000 psi. Foradditional requirements, see Section 8.32.3 of the AASHTO Standard Specifications forHighway Bridges.

For Seismic Performance Categories C and D, Section 8.4.1(F) of the AASHTO StandardSpecifications for Seismic Design of Highway Bridges, the lap splices for longitudinal columnbars are permitted only within the center half of the column height and shall not be less than thelap splices given in Table 5.1-A6 in Appendix A, or 60 bar diameters whichever is greater.

Note that the maximum spacing of the transverse reinforcement (i.e., column ties) over thelength of the splice shall not exceed the smaller of 4 inches or 1/4 of the minimum column plandimension.

2. Lap Splices — Compression

The compression lap splices shown in Table 5.1-A7 (right-hand column) in Appendix A, arefor concrete strengths greater than 3,000 psi. If the concrete strength is less than 3,000 psi, thecompression lap splices should be increased by one third. Note that when two bars of differentdiameters are lap spliced, the length of the lap splice shall be the larger of the lap splice for thesmaller bar or the development length of the larger bar.

3. Mechanical Splices

A second method of splicing is by mechanical splices, which are proprietary splicingmechanisms. The requirements for mechanical splices are found in Section 6-02.3(24)F of theStandard Specifications, Sections 8.32.2 and 8.32.3 of the AASHTO Standard Specifications forHighway Bridges, and Section 8.4.1(F) of the Standard Specifications for Seismic Design ofHighway Bridges.

4. Welded Splices

Welding of reinforcing bars is the third acceptable method of splicing reinforcing bars. Section6-02.3(24)E of the Standard Specifications describes the requirements for welding reinforcingsteel. On modifications to existing structures, welding of reinforcing bars may not be possiblebecause of the non-weldability of some steels. See Sections 8.32.2 and 8.32.3 of the AASHTOStandard Specifications for Highway Bridges and Section 8.4.1(F) of the Standard Specificationsfor Seismic Design of Highway Bridges for additional welded splice requirements.

E. Bends

For standard hooks and bend radii, see Table 5.1-15. Note that the tail lengths are greater for the 135°seismic tie hook than for the regular or nonseismic 135° tie hook. For field bending requirements, seeSection 6-02.3(24)A of the Standard Specifications.

F. Fabrication Lengths

Reinforcing bars are normally stocked in lengths of 60 feet. They can also be fabricated in longerlengths.



5.1-10 July 2000

The maximum overall bar lengths to be specified on the plans are:

Bar Size Maximum Length

#3 30′-0″#4, #5 40′-0″#6, #7 60′-0″

#8, #9, #10 60′-0″#11, #14, #18 60′-0″

Where possible, specify lengths 60 feet and less for bar sizes #8 through #18. Because of placementconsiderations, the overall lengths of bar size #3 has been limited to 30 feet and bar sizes #4 and #5to 40 feet. To use longer lengths, the designer should make sure that the bars can be placed andtransported by truck. See Table 5.1-A1 in Appendix A.

G. Placement

Placement of reinforcing bars can be a problem during construction. Reinforcing bars are more thanjust lines on the drawing, they have size, weight, and volume. In confined areas, the designer shouldensure that reinforcing bars can be placed. Sometimes it may be necessary to make a large scaledrawing of reinforcement to look for interference and placement problems. If interference is expected,additional details may be required in the contract plans showing how to handle the interference andplacement problems.

H. Percentage Requirements

There are several AASHTO requirements to ensure that minimum reinforcement is provided inreinforced concrete members.

1. Flexure

The reinforcement provided at any section should be adequate to develop a moment at least 1.2times the cracking moment calculated on the basis of the modulus of rupture for normal weightconcrete. The modulus of rupture for normal weight concrete is . This requirement maybe waived if the area of reinforcement provided is at least one-third greater than that required byanalysis. For additional minimum reinforcement required, see Section 8.17, AASHTO StandardSpecifications for Highway Bridges.

2. Compression

For columns, the area of longitudinal reinforcement shall not exceed 0.08 nor be less than 0.01 ofthe gross area, Ag, of the section. Preferably, the ratio of longitudinal reinforcement should notexceed 0.04 of the gross area, Ag, to ensure constructibility and placement of concrete. If a ratiogreater than 0.04 is used, the designer should verify that concrete can be placed. If for architec-tural purposes the cross section is larger than that required by the loading, a reduced effectivearea may be used. The reduced effective area shall not be less than that which would require1percent of the longitudinal area to carry the loading. Additional lateral reinforcement require-ments are given in Section 8.18, AASHTO Standard Specifications for Highway Bridges, andfor plastic hinge zones, see Section 8.4.1(D), AASHTO Standard Specifications for the SeismicDesign of Highway Bridges. For column reinforcing, ASTM A 706 reinforcing should bepecified to improve durability.

3. Other Minimum Reinforcement Requirements

For minimum shear reinforcement requirements, see Section 8.19 and for minimum temperatureand shrinkage reinforcement, see Section 8.20, AASHTO Standard Specifications for HighwayBridges.

√7.5 fc′


Reinforced Concrete Superstructures Design Methods

July 2000 5.2-1

5.2 Design Methods

5.2.1 Strength Design Method

A. Design Philosophy

In the strength design method or ultimate strength method, the service loads are increased by loadfactors to obtain the ultimate design load. The structural members are then proportioned to providethe design ultimate strength. Several textbooks listed in the bibliography, which are excellentsources [1,2,3].

B. Flexure

The basic strength design requirement can be expressed as follows:

Design Strength≥ Required Strength or φ Mn ≥ Mu (1)

For design purposes, the area of reinforcement for a singly reinforced beam or slab can be determinedby letting:

Mu = φ Mn = φ [As (fy) (d – a/2)] (2)

However, if a As(fy)/(0.85)(fc′)(b) and ρ = As/(b)(d) (3)

Equation (2) can be expressed as:

Mu/φ (b) (d)2 = ρ (fy) [1 – 0.59 (ρ) fy/fc′] (4)

Tables 5.2-1 through 5.2-3 in Appendix 5.2-A1, -A2, and -A3, were prepared based on Eq (4) toquickly determine the amount of reinforcing steel required, As required, when Mu, fc′, fy, b, and dare known.

An alternate approach is to solve directly for As required from:

As required= (5)

Similarly, substituting 1.2Mcr for Mu, As min can be found from:

As min = where h = slab thickness (6)

From AASHTO 8.16.3.1.1 and 8.16.3.2.2, As max can be found from:

As max = 0.6375β1 (b) (d) (7)

where β1 = 0.85 if fc′ ≤ 4 ksi and β1 = 0.85 – 0.05 (fc′ – 4) if fc′ > 4 ksi, but not less than 0.65

Tension reinforcement should be designed in the following order:

1. From Eq (5) or Tables 5.2-A1 through 5.2-A3 in Appendix A, determine As required.

2. From Eq (6) determine As min.

3. From Eq (7) or Tables 5.2-A1 through 5.2-A3 in Appendix A, determine As max.

31.3725 Mu fc′ (b)

d2 –0.85 fc′ (b) fy

d –( )√

0.124 h2d2 –0.85 fc′ (b) fy

d –( )√ √ fc′

fc′ 87fy 87 + fy( )

where Mu = kips – in fc′ = ksi



5.2-2 July 2000

4. If As required > As max, increase the member’s dimensions.If A s max > As required> As min, use As ≥ As required.If A s required< As min < 1.33 As required, use As≥ As min.If 1.33 As required< As min, use As≥ 1.33 As required.Always use As≤ As max.

See Appendix 5.2-B1 and 5.2-B2 for design examples.

C. Shear

The AASHTO Standard Specifications for Highway Bridges addresses shear design of membersin Section 8.16.6. Shear friction provisions (Section 8.16.6.4) are applied to transfer shear acrossa plane, such as: an existing or potential crack, an interface between dissimilar materials, or at aconstruction joint between two sections of concrete placed at different times.

The shear design for deep beams is not addressed in the AASHTO Standard Specifications, but isdiscussed in Section 11.8, ACI 318-89 Building Code Requirements for Reinforced Concrete andCommentary, and ACI-ASCE Committee 343 Analysis and Design of Reinforced Concrete BridgeStructures [4,5,6].

D. Strut-and-Tie Model

1. General

Strut-and-tie models may be used to determine internal force effects near supports and the pointsof application of concentrated loads [16].

The strut-and-tie model should be considered for the design of deep footings and pile caps orother situations in which the distance between the centers of applied load and supporting reactionis less than twice the member thickness.

2. Structural Modeling

The structure and a component or region, thereof, may be modeled as an assembly of steeltension ties and concrete compressive struts interconnected at nodes to form a truss capableof carrying all the applied loads to the supports as shown in Figure 5.2.1-1 for a deep beam.The required widths of compression struts and tension ties shall be considered in determiningthe geometry of the truss. The truss model does not necessarily need to conform to structuralstability as a real truss would.

The factored resistance, Pn,of struts and ties shall be taken as that of axially loaded components.

Pu′ = ϕ Pn

where:

Pn = nominal resistance of strut or tie (KIP)ϕ = 0.7 Compressionϕ = 0.9 Tension



July 2000 5.2-3

3. Proportioning of Compressive Struts

a. Strength of Unreinforced Strut

The nominal resistance of an unreinforced compressive strut shall be taken as:

Pn = fcuAcs

where:

Pn = nominal resistance of a compressive strut (kips)

fcu = limiting compressive stress (ksi)

Acs = effective cross-sectional area of strut (in2)

b. Effective Cross-Sectional Area of Strut

The value of Acs shall be determined by considering both the available concrete area and theanchorage conditions at the ends of the strut, as shown in Figure 5.2.1-2.

When a strut is anchored by reinforcement, the effective concrete area may be consideredto extend a distance of up to six bar diameters from the anchored bar, as shown in Figures5.2.1-2(a), 5.2.1-2(b), and 5.2.1-2(c).

c. Limiting Compressive Stress in Strut

The limiting compressive stress, fcu, shall be taken as:

fcu = ≤ 0.8 fc′

for which:

ε1 = εs + (εs + 0.002) cot2 αs

where:

as = the smallest angle between the compressive strut and adjoining tensionties (DEG)

εs = the tensile strain in the concrete in the direction of the tension tie (in/in)fc′ = specified compressive strength (ksi)

d. Reinforced Strut

If the compressive strut contains reinforcement that is parallel to the strut and detailed todevelop its yield stress in compression as shown in Figure 5.2.1-2(d), the nominal resistanceof the strut shall be taken as:

Pn = fcu Acs + fy Ass

where:

Ass = area of reinforcement in the strut (in2)

fc′0.8 + 170ε1



5.2-4 July 2000

Strut-and-Tie Model for Deep BeamFigure 5.2.1-1



July 2000 5.2-5

Influence of Anchorage Conditions on Effective Cross-Sectional Area of StrutFigure 5.2.1-2



5.2-6 July 2000

4. Proportioning of Tension Ties

a. Strength of Tie

Tension tie reinforcement shall be anchored to the nodal zones by specified embedmentlengths, hooks, or mechanical anchorages. The tension force shall be developed at the innerface of the nodal zone.

The nominal resistance of a tension tie in KIP shall be taken as:

Pn = fy Ast + Aps [fpe + fy]

where:

Ast = total area of longitudinal mild steel reinforcement in the tie (IN2)Aps = area of prestressing steel (IN2)fy = yield strength of mild steel longitudinal reinforcement (KSI)fpe = stress in prestressing steel due to prestress after losses (KSI)

b. Anchorage of Tie

The tension tie reinforcement shall be anchored to transfer the tension force therein tothe node regions of the truss in accordance with the requirements for development ofreinforcement as specified in Article 5.1.2C.

5. Proportioning of Node Regions

Unless confining reinforcement is provided and its effect is supported by analysis orexperimentation, the concrete compressive stress in the node regions of the strut shall not exceed:

• For node regions bounded by compressive struts and bearing areas: 0.85 ϕ fc′

• For node regions anchoring a one-direction tension tie: 0.75 ϕ fc′

• For node regions anchoring tension ties in more than one direction: 0.65 ϕ fc′

where:

ϕ = 0.7 resistance factor for bearing on concrete

The tension tie reinforcement shall be uniformly distributed over an effective area of concrete atleast equal to the tension tie force divided by the stress limits specified herein.

In addition to satisfying strength criteria for compression struts and tension ties, the node regionsshall be designed to comply with the stress and anchorage limits.

6. Crack Control Reinforcement

Structures and components or regions thereof, except for slabs and footings, which have beendesigned in accordance with the provisions strut-and-tie model, shall contain an orthogonalgrid of reinforcing bars near each face. The spacing of the bars in these grids shall not exceed12.0 inches.

The ratio of reinforcement area to gross concrete area shall not be less than 0.003 in eachdirection.

Crack control reinforcement, located within the tension tie, may be considered as part of thetension tie reinforcement.



July 2000 5.2-7

E. Shear and Torsion, ACI Method

The AASHTO Standard Specifications for Highway Bridges does not address the design of reinforcedconcrete members for torsion. The design for shear and torsion is based on ACI 318-95 BuildingCode Requirements for Structural Concrete and Commentary (318F-95) and is satisfactory for bridgemembers with dimensions similar to those normally used in buildings. The AASHTO LRFD Specifi-cations Article 5.8.3.6 may also be used for design of sections subjected to shear and torsion.

F. Shear and Torsion, Strut-and-Tie Method

According to Hsu [7], utilizing ACI 318-89 for members is awkward and overly conservative whenapplied to large-size hollow members. Collins and Mitchell [8] propose a rational design method forshear and torsion based on the compression field theory or strut and tie method for both prestressedand non-prestressed concrete beams. These methods assume that diagonal compressive stresses canbe transmitted through cracked concrete. In addition to transmitting these diagonal compressivestresses, shear stresses are transmitted from one face of the crack to the other by a combination ofaggregate interlock and dowel action of the stirrups.

For recommendations and design examples for beams in shear and torsion, the designer can referto the paper by M.P. Collins and D. Mitchell, Shear and Torsion Design of Prestressed andNon-Prestressed Concrete Beams, PCI Journal, September-October 1980, pp. 32-100 [8]. SeeAppendix 5.2-B3 for a strut and tie design example for a pier cap.

G. Deflection

Flexural members are designed to have adequate stiffness to limit deflections or any deformationswhich may adversely affect the strength or serviceability of the structure at service load plus impact.The minimum superstructure depths are specified in AASHTO Table 8.9.2 and deflections shall becomputed in accordance with Section 8.13, AASHTO Standard Specifications for Highway Bridges.

H. Seviceability

In addition to the deflection control requirements described above, service load stresses shall belimited to satisfy fatigue (Section 8.16.8.3) and for distribution of tension reinforcement when fy fortension reinforcement exceeds 40,000 psi (Section 8.16.8.4 AASHTO Specifications).

To control cracking of the concrete, tension reinforcement at maximum positive and negative momentsections shall be chosen so that the calculated service load stress, fs in ksi, shall be less than the valuecomputed by:

fs = ≤ 0.6 fy

The requirements for control of cracking apply to superstructure elements only

The calculated service load stress is calculated utilizing Working Stress Design (WSD) principlesdescribed below. The values of dc and A are defined in Section 8.16.8.4 of the AASHTO StandardSpecifications for Highway Bridges. The value z shall be 130 kips per inch for girder and crossbeamreinforcing bars in negative moment regions, and all deck reinforcing bars. A value of 170 kips perinch shall be used for all other positive moment regions. Note that this check is for distribution offlexural reinforcement to control cracking. See Appendix 5.2-B2 which shows the flexural reinforce-ment at a pier location placed equally in top and bottom layers. When this is done, the total slabthickness can be used in computing A.

z

(dc x A)1/3



5.2-8 July 2000

5.2.2 Working Stress Design Method

Prior to the strength design method, introduced in the 1973, AASHTO Standard Specifications forHighway Bridges, the working stress design (WSD) method was used to design bridges. Many design aidswere produced as a result. The ACI Publication SP-3, Reinforced Concrete Design Handbook WorkingStress Method [9], is a publication that was widely used by designers and several textbooks have sectionsdevoted to WSD [1,2].

Working Stress Design principles are used to compute the tensile stress, fs, and Mcr, which are used tocheck crack control and minimum flexural reinforcement respectively. Design aid for working stressdesign method for Class 3000 and 4000 concrete is provided in Appendix B4.

P65:DP/BDM5


Reinforced Concrete Superstructures Reinforced Concrete Box Girder Bridges

July 2000 5.3-1

5.3 Reinforced Concrete Box Girder Bridges

A typical box girder bridge is comprised of top and bottom concrete slabs connected by a series of verticalgirder stems. This section is a guide for designing:

Top slabBottom slabGirder stem (web)

For design criteria not covered, see Section 2.4.1.C.

5.3.1 Girder Spacing and Basic Geometries

A. Girder Spacing

The most economical web spacing for ordinary box girder bridges varies from about 8 to 12 feet.Greater girder spacing requires some increase in both top and bottom slab thickness, but the cost ofthe additional concrete can be offset by decreasing the total number of girder stems. Fewer girderstems reduces the amount of form work required and a lower cost.

The number of girder stems can be reduced by cantilevering the top slab beyond the exterior girders.A deck overhang of approximately one-half the girder spacing generally gives satisfactory results.This procedure usually results in a more aesthetic as well as a more economical bridge.

For girder stem spacing in excess of 12 feet or cantilever overhang in excess of 6 feet, transversepost-tensioning shall be used.

B. Basic Dimensions (Figure 5.3.1-1)

1. Top Slab Thickness, T1 (includes 1/2″ wearing surface)

T1 = 12 x (S+10)/30 but not less than 7″ with overlay or 7.5″ without overlay.

2. Bottom Slab Thickness, T2

a. Near Center Span

T2 = 12 x (Sclr)/16 but not less than 5.5″ (normally 6.0″ is used).

b. Near Intermediate Piers

Thickening of the bottom slab is often used in negative moment regions to controlcompressive stresses that are significant.

Transition slope = 24:1 (see T2′ in Figure 5.3.2-8).

3. Girder Stem (Web) Thickness, T3

a. Near Center Span

Minimum T3 = 9.0″ — vertical

Minimum T3 = 10.0″ — if sloped

b. Near Supports

Thickening of girder stems is used in areas adjacent to supports to control shearrequirements.



5.3-2 July 2000

Changes in girder web thickness shall be tapered for a minimum distance of 12 times thedifference in web thickness.

Maximum T3 = T3+4.0″ maximum

Transition length = 12 x (T3) in inches

Basic DimensionsFigure 5.3.1-1



July 2000 5.3-3

4. Intermediate Diaphragm Thickness, T4 and Diaphragm Spacing

a. For tangent and curved bridge with R > 800 feet

T4 = 0″ (Diaphragms are not required.)

b. For curved bridge with R < 800 feet

T4 = 8.0″

Diaphragm spacing shall be as follows:

For 600′ < R < 800′at 1/2 pt. of span.

For 400′ < R < 600′ at 1/3 pt. of span.

For R < 400′ at 1/4 pt. of span.

C. Construction Considerations

Review the following construction considerations to ensure that:

1. Construction joints at slab/stem interface or fillet/stem interface at top slab are appropriate.

2. All construction joints to have roughened surfaces.

3. Bottom slab is parallel to top slab (constant depth).

4. Girder stems are vertical.

5. Dead load deflection and camber to nearest 1/8″.

6. Skew and curvature effects have been considered.

7. Thermal effects have been considered.

8. The potential for falsework settlement is acceptable. This always requires added stirrupreinforcement in sloped outer webs.

D. Load Distribution

1. Unit Design

According to the AASHTO specifications, the entire slab width shall be assumed effective forcompression. It is both economical and desirable to design the entire superstructure as a unitrather than as individual girders. When a reinforced box girder bridge is designed as an indi-vidual girder with a deck overhang, the positive reinforcement is congested in the exterior cells.The unit design method permits distributing all girder reinforcement uniformly throughout thewidth of the structure.

2. Dead Loads

a. Box dead loads.

b. D.L. of top deck forms — 5 lbs. per sq. ft. of the area.— 10 lbs. per sq. ft. if web spacing > 10′−0″.

c. Traffic barrier.

d. Overlay, intermediate diaphragm, and utility weight if applicable.



5.3-4 July 2000

3. Live Load

a. Superstructure

No. of lanes = slab width (curb to curb) / 14

Fractional lane width will be used

For example, 58 roadway / 14 = 4.14, then no. of lanes = 4.14

b. Substructure

No. of lanes = slab width (curb to curb) / 12

Fractional lane width will be ignored

For example, 58 roadway / 12 = 4.83, then no. of lanes = 4.0

c. Overload if applicable.

5.3.2 Reinforcement

This section discusses moment reinforcement for top slab, bottom slab, and intermediate diaphragms inbox girders.

A. Top Slab Reinforcement

1. Near Center of Span

Figure 5.3.2-1 shows the reinforcement required near the center of the span and Figure 5.3.2-2shows the overhang reinforcement.

a. Transverse reinforcing in the top and bottom layers to transfer the load to the main girderstems shall be equal in size and spacing.

b. Bottom longitudinal “distribution reinforcement” in the middle half of the deck span (Seff) toaid in distributing the wheel loads.

c. Top longitudinal “temperature and shrinkage reinforcement.”

2. Near Intermediate Piers

Figure 5.3.2-3 illustrates the reinforcement requirement near intermediate piers. See Appendix5.2-B2 for design of longitudinal deck reinforcement.

a. Transverse reinforcing same as center of span.

b. Longitudinal reinforcement to resist negative moment (see Figure 5.3.2-3).

c. “Distribution of flexure reinforcement” to limit cracking (see Figure 5.3.2-3).

Allowable fs = z/(dc x A)1/3 ≤ 0.6fy, where z = 130 kips per inch.

3. Bar Patterns

a. Transverse Reinforcement

It is preferable to place the transverse reinforcement parallel to the X-Beam and enddiaphragm on skews up to 25 degrees or less. Where skew angles exceed 25 degrees, thetransverse bars are normal to bridge center line and the areas near the expansion joint andbridge ends are reinforcement by partial length bars. The bottom transverse slab reinforce-ment is discontinued at the X-Beam (see Figure 5.3.2-4).



July 2000 5.3-5

b. Longitudinal Reinforcement

For longitudinal reinforcing bar patterns, see Chapter 6.

Partial Section Near Center of SpanFigure 5.3.2-1

Overhang DetailFigure 5.3.2-2



5.3-6 July 2000

Top Slab Flexural Reinforcing Near Intermediate PierFigure 5.3.2-3

Partial Plans at AbutmentsFigure 5.3.2-4



July 2000 5.3-7

B. Bottom Slab Reinforcement

1. Near Center of Span

Figure 5.3.2-5 shows the reinforcement required near the center of the span.

a. Minimum transverse “distributed reinforcement.”

As=0.005 x flange area with 1/2 As distributed equally to each surface.

b. Longitudinal “main reinforcement” to resist positive moment.

c. Check “distribution of flexure reinforcement” to limit cracking (see Figure 5.3.2-5).

Allowable fs = z/(dc x A)1/3 ≤ 0.6fy, where z = 170 kips per inch.

d. Add steel for construction load (sloped outer webs).

2. Near Intermediate Piers

Figure 5.3.2-6 shows the reinforcement required near intermediate piers.

a. Minimum transverse reinforcement same as center of span.

b. Minimum longitudinal “temperature and shrinkage reinforcement.”

As=0.004 x flange area with 1/2 As distributed equally to each face.

c. Add steel for construction load (sloped outer webs).

3. Bar Patterns

a. Transverse Reinforcement

See top slab bar patterns, Figures 5.3.2-1, 5.3.2-2, and 5.3.2-3.

All bottom slab transverse bars shall be bent at the outside face of the exterior web.For vertical web, the tail will be 1′-0″ and for sloping exterior web 2′-0″ minimum splicewith the outside web stirrups. See Figure 5.3.2-7.

b. Longitudinal Reinforcement

For longitudinal reinforcing bar patterns, see Chapter 6.

C. Web Reinforcement

1. Vertical Stirrups (see Figure 5.3.2-8)

The web reinforcement should be designed for the following requirements:

Vertical shear requirements.

Out of plane bending on outside web due to live load on cantilever overhang.

Horizontal shear requirements for composite flexural members.

Minimum (#5 bars @ 1′-6″), where bw = no. of girder stems (T3). Av bw s fy

= 50



5.3-8 July 2000

2. Web Longitudinal Reinforcement (see Figure 5.3.2-8)

If the depth of the side face of a member exceeds 3 feet, longitudinal skin reinforcement shall beuniformly distributed along both side faces of the member for a distance d/2 nearest the flexuraltension reinforcement. The area of skin reinforcement Ask per foot of height on each side faceshall be ≥ 0.012 (d – 30). The maximum spacing of skin reinforcement shall not exceed the lesserof d/6 and 12 inches. Such freinforcement may be included in strength computations if a straincompatibility analysis is made to determine stresses in the individual bars or wires. The total areaof longitudinal skin reinforcement in both faces need not exceed one half of the flexural tensilereinforcement.

Where As = Total required area of longitudinal reinforcing steel.

Reinforcing steel spacing < Web Thickness (T3) or 12″.

For cast-in-place sloped outer webs, increase inside stirrup reinforcement and bottom slab toptransverse reinforcement as required for the web moment locked-in during construction of the topslab. This moment about the bottom corner of the web is due to tributary load from the top slabconcrete placement plus 10 psf form dead load. See Figure 5.3.2-10 for typical top slab forming.

Bottom Slab Reinforcement Near Center of SpanFigure 5.3.2-5

Bottom Slab Reinforcement Near Intermediate PierFigure 5.3.2-6



July 2000 5.3-9

Figure 5.3.2-7



5.3-10 July 2000

Figure 5.3.2-8



July 2000 5.3-11

D. Intermediate Diaphragm (see Figure 5.3.2-9)

Figure 5.3.2-9

Intermediate diaphragms are not required for bridges on tangent alignment or curved bridges with aninside radius of 800 feet or greater.

Notes:

1. If the bar is not spliced, the horizontal dimension should be 4″ shorter than the slab width.

2. Stirrup hanger must be placed above longitudinal steel when diaphragm is skewed and slabreinforcement is placed normal to center of roadway. (Caution: Watch for the clearance withlongitudinal steel).

3. The reinforcement should have at least one splice to facilitate proper bar placement.

Notes:



5.3-12 July 2000

1. The diagonal brace supports web forms during web pour. After cure, the web is stiffer than the brace,and the web attracts load from subsequent concrete placements.

2. The tributary load includes half the overhang because the outer web form remains tied to andtransfers load to the web which is considerably stiffer than the formwork.

Increase Web Reinf. for Locked-In Construction Load

Due to Typical Top Slab Forming for Sloped Web Box GirderFigure 5.3.2-10



July 2000 5.3-13

5.3.3 Crossbeam

A. Basic Geometry

For aesthetic purposes, it is preferable to keep the crossbeam within the superstructure so that thebottom slab of the entire bridge is a continuous plane surface interrupted only by the columns.Although the depth of the crossbeam may be limited, the width can be made as wide as necessary tosatisfy design requirements. Normally, it varies from 3 feet to the depth of box but is not less thancolumn sizes to utilize the column reinforcement (see Figure 5.3.3-1 and 5.3.3-2).

Crossbeams on box girder type of construction shall be designed as a T beam utilizing the flange incompression, assuming the deck slab acts as a flange for positive moment and bottom slab a flangefor negative moment. The effective overhang of the flange on a cantilever beam shall be limited to sixtimes the flange thickness.

The bottom slab thickness is frequently increased near the crossbeam in order to keep the main boxgirder compressive stresses to a desirable level for negative girder moments (see Figure 5.3.2-8). Thisbottom slab flare also helps resist negative crossbeam moments. Consideration should be given toflaring the bottom slab at the crossbeam for designing the cap even if it is not required for resistingmain girder moments.

B. Reinforcing Steel Details

Special attention should be given to the details to ensure that the column and crossbeam reinforce-ment will not interfere with each other. This can be a problem especially when round columns with agreat number of vertical bars must be meshed with a considerable amount of positive crossbeamreinforcement passing over the columns.

1. Top Reinforcement

Provide negative moment reinforcement at the 1/4 point of the square or equivalent squarecolumns (see Appendix 5.3-A1 and 5.3-A4).

a. When Skew Angle < 10 Degrees

If the bridge is tangent or slightly skewed and the deck reinforcement is parallel to the crossbeam, the negative cap reinforcement can be placed either in contact with top deck negativereinforcement or directly under the main deck reinforcement (see Figure 5.3.3-1). Reinforce-ment must be epoxy coated if the location of reinforcement is less than 4″ below top of deck.

b. When Skewed Angle > 10 Degrees

When the structure is on a greater skew and the deck steel is normal or radial to the longitu-dinal centerline of the bridge, the negative cap reinforcement should be lowered to below themain deck reinforcement (see Figure 5.3.3-2).

c. To avoid cracking of concrete, interim reinforcements are required below the constructionjoint in diaphgragms and crossbeams.

The interim reinforcements shall develop a moment capacity of 1.2 Mcr where Mcr may begiven as:



5.3-14 July 2000

Mcr =

fr =

Mcr = 1.25 bh2

Mn = 1.2Mcr = 1.5 bh2

As =

5.3.4 End Diaphragm

A. Basic Geometry

Bearings at the end diaphragms are usually located under the girder stems and transfer loads directlyto the pier (see Figure 5.3.3-3). In this case, the diaphragm width should be equal to or greater thanbearing sole plate grout pads (see Figure 5.3.3-4).

Designer should provide access space for maintenance and inspection of bearings.

Allowance should be provided to remove and replace the bearings. Lift point locations, jack capacity,number of jacks, and maximum permitted lift should be shown in the plan details.

Skew Angle ≤ 10°Crossbeam Top Reinforcement

Figure 5.3.3-1

fr Ig yt

√7.5 fc′

√ fc′

√ fc′

31.3725Md2 –0.85 fc′ b fy

d –( )√ fc′



July 2000 5.3-15

Skew Angle > 10°Crossbeam Top Reinforcement

Figure 5.3.3-2

Bearing Locations, Lift Points, Jack Capacity, and Maximum Lift Permitted at End DiaphragmFigure 5.3.3-3



5.3-16 July 2000

“L” Abutment End DiaphragmFigure 5.3.4-1

The end diaphragms should be wide enough to provide adequate reinforcing embedment length.When the structure is on a skew greater than 10 degrees and the deck steel is normal or radial tothe center of the bridge, the width should be enough to accommodate the embedment length ofthe reinforcement.

The most commonly used type of end diaphragm is shown in Figure 5.3.3-5. The dimensions shownhere are used as a guideline and should be modified if necessary. This end diaphragm is used with astub abutment and overhangs the stub abutment. It is used on bridges with an overall or out-to-outlength less than 400 feet. If the overall length exceeds 400 feet, an “L” abutment should be used.

B. Reinforcing Steel Details

Typical reinforcement details for an end diaphragm are shown in Figure 5.3.3-6.

5.3.5 Dead Load Deflection and Camber

Camber is the adjustment made to the vertical alignment to compensate for the anticipated dead loaddeflection and the long-term deflection caused by shrinkage and creep. The multipliers for estimatinglong-term deflection and camber for reinforced concrete flexural members may be taken as shown inTable 1.



July 2000 5.3-17

Multipliers for Estimating Long-term Deflection and Camber of Concrete MembersTable 5.3.5-1

MultiplierCoefficient

Girder Adjacent to Existing/Stage Construction

Deflection (downward) — apply to the elastic deflection due 1.90to the weight of member

Deflection (downward) — apply to the elastic deflection due 2.20to superimposed dead load only

Girder Away From Existing/Stage Construction

Deflection (downward) — apply to the elastic deflection due 2.70to the weight of member

Deflection (downward) — apply to the elastic deflection due 3.00to superimposed dead load only

In addition to dead load deflection, forms and falsework tend to settle and compress under the weightof freshly placed concrete. The amount of this takeup is dependent upon the type and design of thefalsework, workmanship, type and quality of materials and support conditions. The camber should bemodified to account for anticipated takeup in the falsework.

5.3.6 Thermal Effects

Concrete box girder bridges are subjected to stresses and/or movements resulting from temperaturevariation. Temperature effects result from time-dependent variations in the effective bridge temperatureand from temperature differentials within the bridge superstructure.

A. Effective Bridge Temperature and Movement

Fluctuation in effective bridge temperature causes expansion and contraction of the structure. Propertemperature expansion provisions are essential in order to ensure that the structure will not bedamaged by thermal movements. These movements, in turn, induce stresses in supporting elementssuch as columns or piers, and result in horizontal movement of the expansion joints and bearings.For more details, see Chapter 8.

B. Differential Temperature

Although time-dependent variations in the effective temperature have caused problems in bothreinforced and prestressed concrete bridges, detrimental effects caused by temperature differentialwithin the superstructure have occurred only in prestressed bridges. Therefore, computation ofstresses and movements resulting from the vertical temperature gradients is not included in thischapter. For more details, see AASHTO Guide Specifications, Thermal Effects on ConcreteBridge Superstructures (1989).



5.3-18 July 2000

End Diaphragm With Stub AbutmentFigure 5.3.4-2

Typical End Diaphragm ReinforcementFigure 5.3.4-3



July 2000 5.3-19

5.3.7 Hinges

Hinges are one of the weakest links of box girder bridges subject to earthquake forces and it is desirable toeliminate hinges or reduce the number of hinges. For more details on the design of hinges, see Section 5.4.

Designer should provide access space or pockets for maintenance and inspection of bearings.

Allowance should be provided to remove and replace the bearings. Lift point locations, maximum liftpermitted, jack capacity, and number of jacks should be shown in the hinge plan details.

5.3.8 Utility Openings

A. Confined Spaces

A confined space is any place having a limited means of exit which is subject to the accumulation oftoxic or flammable contaminants or an oxygen deficient environment. Confined spaces include butare not limited to pontoons, box girder bridges, storage tanks, ventilation or exhaust ducts, utilityvaults, tunnels, pipelines, and open-topped spaces more than 4 feet in depth such as pits, tubes, vaults,and vessels. The designer should provide for the following:

• A sign with “Confined Space Authorized Personnel Only.”

• In the “Special Provisions Check List,” alert and/or indicate that a special provision might beneeded to cover confined spaces.

B. Drain Holes

Drain holes should be placed in the bottom slab at the low point of each cell to drain curing waterduring construction and any rain water that leaks through the deck slab. Additional drains shall beprovided as a safeguard against water accumulation in the cell (especially when waterlines are carriedby the bridge). In some instances, drainage through the bottom slab is difficult and other means shallbe provided (i.e., cells over large piers and where a sloping exterior web intersects a vertical web).In this case, a horizontal drain should be provided through the vertical web. Figure 5.3.8-1 showsdrainage details for the bottom slab of concrete box girder bridges.

C. Access Hole and Air Vent Holes

Access holes with doors should be placed in the bottom slab if necessary to inspect utilities insidecells (i.e., waterline, conduits, E.Q. restrainers, etc.). Figure 5.3.8-2 and 5.3.8-3 shows access holeand air vent hole details. Air vents are required when access holes are used.



5.3-20 July 2000

P65:DP/BDM5

Figure 5.3.8-1



July 2000 5.3-21

Figure 5.3.8-2



5.3-22 July 2000

Figure 5.3.8-3


Reinforced Concrete Superstructures Hinges and Inverted T-Beam Pier Caps

July 2000 5.4-1

5.4 Hinges and Inverted T-Beam Pier Caps

Hinges and inverted T-beam pier caps require special design and detailing considerations. Continuoushinge shelves (both top and bottom projecting shelves) and continuous ledges of inverted T-beam piercaps, which support girders, are shown in Figures 5.4-1 and 5.4-2 respectively. In each case, verticaltensile forces (hanger tension) act at the intersection of the web and the horizontal hinge shelf or ledge.In the ledges of inverted T-beam pier caps, passage of live loads may also cause reversing torsionalstresses which together with conventional longitudinal shear and bending produce complex stressdistributions in the ledges [10,11].

Provide minimum shelf or ledge support lengths (N, N1, and N2) and provide positive longitudinallinkage (e.g., earthquake restrainers) [12] in accordance with the current AASHTO seismic designrequirements.

A. Local Failure Modes

In addition to conventional longitudinal bending and shearing forces, there are several local modesof failure which should be addressed in the design [10,11]. These are: shear friction failure, flexuralfailure, hanger tension failure, punching shear failure of the horizontal hinge shelf or ledge, andspalling under the bearing.

Figure 5.4-3 shows these local failure modes and potential cracks. For all conditions, except for thebearing strength check, use φ=0.85. For the bearing strength check, use φ=0.7 [13].

Continuous HingeFigure 5.4-1



5.4-2 July 2000

Inverted T-Beam Pier CapFigure 5.4-2



July 2000 5.4-3

The forces acting on the hinge shown in Figure 5.4-3 are: shear, Vu; horizontal tensile force, Nuc;and moment, Mu.

Vu = Factored Shear (Dead Load + Live Load + Impact) (1)

Nuc ≥ 0.2Vu, but less than 1.0Vu (2)

Mu = Vu(af) + Nuc(h-d) (3)

where: af = Flexural moment arm is the distance from the reaction to thecenterline of the hanger reinforcement, and shall include the thermalmovement of the reaction, Vu.

h-d = Moment arm for the horizontal load, Nuc.

The horizontal tensile load, Nuc, is due to indeterminate causes such as restrained shrinkage ortemperature stresses and is considered a live load [13].

In addition, service load conditions should also be checked for deflections and crack control.

Crack 1 could lead to a flexural or shear friction failure mode.

Crack 2 necessitates hanger reinforcement.

Crack 3 could lead to a punching shear failure.

Crack 4 can be avoided by reducing the bearing stress or allowing more edge distance.

Failure Modes and Potential CracksFigure 5.4-3



5.4-4 July 2000

B. Shear Friction Design

1. Interior Bearing

Figure 5.4-4 shows the effective shelf width used to compute the allowable shear strength. Theratio av/d shall satisfy equation (4) and the factored shear force (including shelf dead load) shallsatisfy both equations (5) and (6) [13]:

av/d ≤ 1.0 (4)

Vu ≤ φ (0.2fc′)(W+4av)(d) (5)

Vu ≤ φµ (Avf)(fy) (6)

where: av = Distance from the reaction to the vertical faced = Depth from compression face to tensile reinforcementφ = 0.85

0.2fc′ ≤ 800 psiW+4av = Effective shelf width

µ = 1.4 for cast-in-place concrete (e.g., monolithic construction,no construction joint)

Avf = Shear friction reinforcement

When W+4av > S, check:

Vu ≤ φ (0.2fc′)(S)(d) (7)

2. Bearing at End of Hinge or Ledge

When S > 2c < (W+4av), check:

Vu ≤ φ (0.2fc′)(2c)(d) (8)

When S > (W+4av) < 2c, check:

Vu ≤ φ (0.2fc′)(W+4av)(d) (9)

When (W+4av) > S > 2c, check:

Vu ≤ φ (0.2fc′)(S)(d) (10)

In addition, equation (6) shall be satisfied. Avf is distributed over 2c, W+4av, or S, whicheveris less.

where c = Distance from the end of the hinge or ledge to the center of theexterior bearing.

S = Center-to-center of girders or hinge seat bearings.



July 2000 5.4-5

Shear Friction DesignFigure 5.4-4

C. Flexural Design (Figure 5.4-5)

The primary reinforcement, As, for the shelf or ledge shall be determined from equations (11),(12), and (13), whichever is greater [13]:

As ≥ Af + An (11)

As ≥ 2(Avf)/3 + An (12)

As ≥ ρmin (W+5af)(d) (13)

where:

ρmin = 0.04(fc′/fy)

Af = Flexural reinforcement required for Mu

Avf = Shear friction reinforcement

An = Tensile reinforcement = Nuc/φ(fy)

In addition, closed stirrups or ties parallel to As with a total area Ah of not less than 0.5(As-An)shall be uniformly distributed within two thirds of the effective depth adjacent to As [13].

If the effective width W+5af≥S place the reinforcement over distance S. At the ends of the hingeor ledge, distribute the reinforcement over distance 2c, S, or W+5af, whichever is less.



5.4-6 July 2000

Flexural DesignFigure 5.4-5

D. Hanger Tension Design (Figure 5.4-6)

The hanger tension reinforcement, Ahr, shall satisfy both of the following strength and service-ability equations:

Vu ≤ φAhr/s)(fy)(S) Strength (14)

V ≤ (Ahr/s)(0.5fy)(W+3av) Serviceability (15)

where:

Ahr = Hanger reinforcement in square inches

s = Spacing of the hanger reinforcement

V = Service load reaction

W+3av = Effective width for hanger reinforcement-Serviceability

Hinge Hanger ReinforcementFigure 5.4-6



July 2000 5.4-7

In addition to equations (14) and (15), the following equation shall also be satisfied for invertedT-beam pier caps (see Figure 5.4-7):

2Vu ≤ 2[2φ bfdf] + φ(ahr/s)(fy)(W+2df) (16)

where bf = Width of bottom flange of inverted T-beam

df = Distance from top of ledge to center of longitudinal cap reinforcementnear the bottom flange of the inverted T-beam

W+2df = Effective width for hanger reinforcement for inverted T-beam.

If S>(W+2df), it is not necessary to add the stirrup reinforcement for conventional shear andtorsion to the hanger reinforcement. Ensure that the stirrup reinforcement satisfies either theconventional longitudinal shear and torsion reinforcement requirements or the hanger reinforce-ment requirement, whichever is greater. If S<(W+2df), it will be necessary to add the requiredhanger reinforcement to that required for shear and torsion [11].

Inverted T-Beam Hanger ReinforcementFigure 5.4-7

E. Punching Shear Check

As shown in Figure 5.4-8, punching shear of the horizontal shelves of hinges and ledges of invertedT-beam pier caps should be checked. For an interior bearing, check:

Vu ≤ φ (4 )(W + 2L′ + 2d)(d) (17)

For an exterior bearing at the end of a hinge or inverted T-beam cap, check:

Vu ≤ φ (4 )(W + L′ + d)(d) (18)

where:

= Allowable tensile strength of concrete for punching shear

W = Width of the rectangular bearing perpendicular to the longitudinal axisof the bridge (e.g., width parallel to the centerline of bearings)

L′ = Length from face of hinge or ledge to back of bearing = L+c

√ fc′

√ fc′

√ fc′

√ 4 fc′



5.4-8 July 2000

Punching Shear at Interior BearingFigure 5.4-8

F. Bearing Strength Check

To prevent spalling under the bearing, the bearing stress should not exceed 0.85(φ)(fc′) [13]:

Vu ≤ 0.85(φ)(fc′)(W)(L) (19)

where: φ = 0.70

L = Length of the rectangular bearing parallel to the longitudinalaxis of the bridge (e.g., parallel to the direction of traffic).

P65:DP/BDM5


Reinforced Concrete Superstructures Widenings

July 2000 5.5-1

5.5 Widenings

This section provides general guidance for the design of bridge widenings. Included are additions to thesubstructure and the superstructure of reinforced concrete box girder, flat slab, T-beam, and precast-prestressed girder bridges. For additional information, see ACI Committee Report, Guide for WideningHighway Bridges [15].

5.5.1 Review of Existing Structures

A. General

Obtain the following documents from existing records for preliminary review, design, and planpreparation:

1. Reduced copy of “As-Built”contract plans from our microfilm records in Bridge Records, Officeof Bridges and Structures.

2. Reduced copy of original contract plans and special provisions, which can be obtained fromEngineering Records (Plans Vault), Records Control. These will not include the “As-Built” plans,since they are made prior to receiving the “As-Built” plans from the Project Engineer. Backupmicrofilm records are also maintained by Engineering Records (Plans Vault), Records Control,but the “As-Built” plans may not be current.

3. Check with the Bridge Preservation Unit for records of any unusual movements/rotations andother structural information.

4. Original design calculations, which are stored in State Archives and can be retrieved by BridgeRecords personnel.

5. Current field data on Supplemental Site Data Form (including current deck elevations at interfaceof widening and existing deck, as well as cross slopes), are obtained from District. Current fieldmeasurements of existing pier crossbeam locations are recommended so that new prestressedgirders are not fabricated too short or too long. This is particularly important if piers have beenconstructed with different skews. This information may not be available in any existing plans,so field trips may be necessary to determine actual details.

6. Original and current Foundation Reports from the Materials Lab or from the Plans Vault.

7. Change Order files to the original bridge contract in Records Control Unit.

B. Original Contract Plans and Special Provisions

Location and size of reinforcement, member sizes and geometry, location of construction joints,details, allowable design soil pressure, and test hole data are given on the plans. Original contractplans can be more legible than the microfilm copies.

The special provisions may include pertinent information that is not covered on the plans or in theStandard Specifications.

C. Original Calculations

The original calculations should be reviewed for any “special assumptions” or office criteria usedin the original design. The actual stresses in the structural members, which will be affected by thewidening, should be reviewed. This may affect the structure type selected for the widening.



5.5-2 July 2000

D. Final Records

For major widening/renovation projects, the Final Records should be reviewed particularly forinformation about the existing foundations and piles. Sometimes the piles indicated on the originalplans were omitted, revised, or required preboring. Final Records are available from Records Controlor Bridge Records (Final Records on some older bridges may be in storage at the Materials Lab).

5.5.2 Analysis and Design Criteria

A. General

Each widening represents a unique situation and construction operations may vary between wideningprojects. The guidelines in this section are based on over 20 years of WSDOT design experience withbridge widenings.

1. Appearance

The widening of a structure should be accomplished in such a manner that the existing structuredoes not look “added on to.” When this is not possible, consideration should be given to enclo-sure walls, cover panels, paint, or other aesthetic treatments. Where possible and appropriate, thestructure’s appearance should be improved by the widening.

2. Materials

Preferably, materials used in the construction of the widening shall have the same thermal andelastic properties as the materials used in the construction of the original structure.

3. Load Distribution and Construction Sequence

The members of the widening should be proportioned to provide similar longitudinal andtransverse load distribution characteristics as the existing structure. Normally this can beachieved by using the same cross sections and member lengths that were used in the existingstructure.

The construction sequence and degree of interaction between the widening and the existingstructure, after completion, shall be fully considered in determining the distribution of the deadload for design of the widening and stress checks for the existing structure. The distribution oflive load shall be in accordance with the AASHTO specifications. Where precast-prestressedgirders are used to widen an existing cast-in-place concrete box girder or T-beam bridge, the liveload distribution factor for interior girder(s) shall be S/5.5.

The construction sequence or stage construction should be clearly shown in the plans to avoidconfusion and misinterpretation during construction. A typical construction sequence mayinvolve placing the deck concrete, removing the falsework, placing the concrete for the closurestrip, and placing the concrete for the traffic barrier. Indicate in the plans a suggested stageconstruction plan to avoid misinterpretation.

4. Specifications

The design of the widening shall conform to the current AASHTO Specifications and the state ofWashington’s Standard Specifications for Road, Bridge, and Municipal Construction.

The method of design for the widening shall be by load factor design methods even though theoriginal design may have been by service load design.



July 2000 5.5-3

5. Geometrical Constraints

The overall appearance and geometrical dimensions of the superstructure and columns of thewidening should be the same or as close as possible to those of the existing structure. This is toensure that the widening will have the same appearance and similar structural stiffness as theoriginal structure.

6. Strength of Concrete

The allowable stresses shown in the latest AASHTO Specifications are to be used. For concretestructures located in rural areas or where the volume of concrete is less than 30 cubic yards, useClass 4000 (fc′ = 4000 psi) and Grade 60 reinforcement. For projects located in urban areas andhaving a volume of concrete greater than 30 cubic yards, Class 5000 may be specified only ifnecessary to meet structural requirements and if facilities are available. Concrete with a greaterstrength may be used, if needed, with consultation and approval of the Bridge Design Engineer.

7. Overlay

It should be established at the preliminary plan stage if an overlay is required as part of thewidening.

8. Strength of the Existing Structure

A review of the strength of the main members of the existing structure shall be made forconstruction conditions utilizing AASHTO Load Factors.

A check of the existing main members after attachment of the widening shall be made for thefinal design loading condition.

If the existing structural elements do not have adequate strength, consult your supervisor or in thecase of consultants, contact the Consultant Liason Engineer for appropriate guidance.

If significant demolition is required on the existing bridge, consideration should be given torequesting concrete strength testing for the existing bridge and including this information in thecontract documents.

9. Special Considerations

a. For structures that were originally designed for HS20 loading, HS25 shall be used to designthe widening. For structures that were originally designed for less than HS20, considerationshould be given to replacing the structure instead of widening it.

b. Where large cambers are expected, a longitudinal joint between the existing structure and thewidening may be considered. Longitudinal joints, if used, should be located out of traveledlanes or beneath median barriers to eliminate potentially hazardous vehicle control problems.

c. The Standard Specifications do not permit falsework to be supported from the existingstructure unless the Plans and Specifications state otherwise. This requirement eliminates thetransmission of vibration from the existing structure to the widening during construction.The existing structure may still be in service.

d. For narrow widenings where the Plans and Specifications require that the falsework besupported from the original structure (e.g., there are no additional girders, columns,crossbeams, or closure strips), there should be no external rigid supports such as posts orfalsework from the ground. Supports from the ground do not permit the widening to deflect



5.5-4 July 2000

with the existing structure when traffic is on the existing structure. This causes the uncuredconcrete of the widening to crack where it joins the existing structure. Differential dead loaddeflection during construction should be given consideration.

e. Precast members may be used to widen existing cast-in-place structures. This method isuseful when the horizontal or vertical clearances during construction are insufficient to buildcast-in-place members.

f. The alignment for diaphragms for the widening shall generally coincide with the existingdiaphragms.

g. When using battered piles, estimate the pile tip elevations and ensure that they will haveample clearance from all existing piles, utilities, or other obstructions. Also check that thereis sufficient clearance between the existing structure and the pile driving equipment.

B. Seismic Design Criteria for Bridge Widenings

1. Adequacy of Existing Structure

Early in the project, determine whether earthquake loading poses any problems for the structuraladequacy of the existing structure (e.g., original unwidened structure). The amount of reinforce-ment and structural detailing of older structures may not meet the current AASHTO seismicdesign requirements. It is important that these deficiencies be determined as soon as possible sothat remedial/retrofitting measures can be evaluated. It should be noted that for some structures,because of deterioration and/or inadequate details, the widening may not be structurally oreconomically feasible. In this case, the Bridge Design Engineer should be consulted for possiblestructure replacement instead of proceeding with widening the structure.

2. Superstructure Widening Without Adding Substructure

No seismic analysis is necessary for this condition. Check the support shelf length required at allpiers. Check the need for longitudinal earthquake restrainers and transverse earthquake stops.

3. Superstructure Widening by Adding Column(s) and Substructure

Use the AASHTO/BDM seismic design criteria with appropriate R factors to design and detailthe new columns and footings for the maximum required capacity.

Analyze the widening and the existing structure as a combined unit.

If the existing structure is supported by single column piers, and is located in SPC or C (LRFDSeismic Zone 2, 3, or 4), the existing columns should be retrofitted if the existing column doesnot have adequate ductility to meet current standards.

If the existing structure is supported by multiple column piers, determine the need to retrofit theexisting columns as part of the widening as follows:

a. For existing bridges in SPC B or C (LRFD, Zone 2, 3, or 4) that are widened with additionalcolumns and substructure, existing columns should be considered for retrofitting unlesscalculations or column details indicate that the existing columns have adequate ductility.Nonductile existing columns will likely not be able to carry vertical load if they experiencethe inelastic deflection that a new (ductile) column can tolerate.



July 2000 5.5-5

b. Only the columns should be retrofitted. Retrofitting the foundations supporting existingcolumns is generally too expensive to consider for a widening project. Experience in pastearthquakes in California has shown that bridges with columns (only) retrofitted haveperformed quite well.

c. Approval for retrofitting existing multiple column piers is subject to available funding andapproval of the Bridge Design Engineer.

4. Other Criteria

a. If recommended in the foundation report, the superstructure widening with new substructureshall also be checked for differential settlement between the existing structure and the newwidened structure. All elements of the structure shall be analyzed and detailed to account forthis differential settlement especially on spread footing foundations.

b. Check support width requirements; if there is a need for earthquake restrainers on theexisting structure as well as the widened portion, they shall be included in the wideningdesign.

c. The current AASHTO seismic design criteria may result in columns with more reinforce-ment and larger footings for the widened portion than those on the existing structure. If it isnot possible to use larger footings because of limited space, an alternate design concept suchas drilled shafts may be necessary.

d. When modifications are made near or on the existing bridge, be careful to isolate any addedpotential stiffening elements (such as traffic barrier against colmuns).

e. The relative stiffness of the new columns compared to the existing columns should beconsidered in the combined analysis. The typical column retrofit is steel jacketing withgrouted annular space (between the existing column and the steel jacket).

f. When strutted columns (horizontal strut between existing columsn) are encountered, removethe strut and analyze the existing columns for the new unbraced length and retrofit, ifnecessary. Refer to WSDOT Research Report on Strutted Columns (nearing completion).

C. Substructure

1. Selection of Foundation

a. The type of foundation to be used to support the widening should generally be the same asthat of the existing structure unless otherwise recommended by the Geotechnical Engineer.The effects of possible differential settlement between the new and the existing foundationsshall be considered.

b. Consider present bridge site conditions when determining new foundation locations. Theconditions include: overhead clearance for pile driving equipment, horizontal clearancerequirements, working room, pile batters, channel changes, utility locations, existingembankments, and other similar conditions.

2. Scour and Drift

Added piles and columns for widenings at water crossings may alter stream flow characteristicsat the bridge site. This may result in pier scouring to a greater depth than experienced with theexisting configuration. Added substructure elements may also increase the possibility of trappingdrift. The Hydraulics Engineer should be consulted concerning potential problems related toscour and drift on all widenings at water crossings.



5.5-6 July 2000

D. Superstructure

1. Camber

Accurate prediction of dead load deflection is more important for widenings than for newbridges, since it is essential that the deck grades match [15].

The multipliers for estimating long-term delfection and camber for bridge widening may be takenas 2.7 times the elastic deflection due to the weight of the member and 3.0 times the elasticdeflection due to the superimposed loads.

To obtain a smooth transition in transverse direction of the bridge deck, the camber of the girderadjacent to the existing structure shall be adjusted for the difference in camber between new andexisting structure. A linear interpolation may be used to adjust the camber of the girders locatedaway from the existing structure.

When large cambers are expected, see Section 5.5.2.A9b.

2. Closure Strip

Except for narrow deck slab widenings (see Section 5.5.2.A9c) a closure strip is required for allcast-in-place widenings. The width shall be the minimum required to accommodate the necessaryreinforcement and for form removal. Reinforcement, which extends through the closure stripshall be investigated in accordance with Section 5.5.4A7. Shear shall be transferred across theclosure strip by shear friction and/or shear keys.

All falsework supporting the widening shall be released and formwork supporting the closurestrip shall be supported from the existing and newly widened structures prior to placing concretein the closure strip. Because of deck slab cracking experienced in widened concrete decks,closure strips are required unless the mid-span dead load deflection is 1/2 inch or less.

3. Stress Levels and Deflections in Existing Structures

Caution is necessary in determining the cumulative stress levels, deflections, and the need forshoring in existing structural members during rehabilitation projects.

For example, a T-beam bridge was originally constructed on falsework and the falsework wasreleased after the slab concrete gained strength. As part of a major rehabilitation project, thebridge was closed to traffic and the entire slab was removed and replaced without shoring.Without the slab, the stems behave as rectangular sections with a reduced depth and width. Theexisting stem reinforcement was not originally designed to support the weight of the slab withoutshoring. After the new slab was placed, wide cracks, eminating from the bottom of the stemopened, indicating that the reinforcement was overstressed. This overstress resulted in a lowerload rating for the newly rehabilitated bridge. This example shows the need to shore up theremaining T-beam stems prior to placing the new slab so that excessive deflections do not occurand overstress in the existing reinforcing steel is prevented.

It is necessary to understand how the original structure was constructed, how the rehabilitatedstructure is to be constructed, and the cumulative stress levels and deflections in the structurefrom the time of original construction through rehabilitation.



July 2000 5.5-7

E. Stability of Widening

For relatively narrow box girder and T-beam widenings, symmetry about the vertical axis should bemaintained because lateral loads are critical during construction. When symmetry is not possible, usepile cap connections, lateral connections, or special falsework. A minimum of two webs is generallyrecommended for box girder widenings. For T-beam widenings that require only one additional web,the web should be centered at the axis of symmetry of the slab. Often the width of the closure stripcan be adjusted to accomplish this.

5.5.3 Removing Portions of the Existing Structure

Portions of the existing structure to be removed shall be clearly indicated on the plans. Where a cleanbreak line is required, a 3/4″ deep saw cut shall be specified for a slab with normal wear and a 1/2″ deep sawcut for worn roadway slabs. In no case, however, shall the saw blade cut or nick the main transverse topslab reinforcement. The special provisions shall state that care will be taken not to damage any reinforce-ment which is to be saved. Hydromilling is preferred where reinforcing bar cover is shallow and caneffectively remove delaminated decks because of the good depth control it offers. When greater depths ofslab are to be removed, special consideration should be given to securing exposed reinforcing bars toprevent undue vibration and subsequent fatigue cracks from occurring in the reinforcing bars.

The current General Special Provisions should be reviewed for other specific requirements on slabremoval.

Removal of any portion of the main structural members should be held to a minimum. Careful consider-ation shall be given to the construction conditions, particularly when the removal affects the existingframe system. In extreme situations, preloading by jacking is acceptable to control stresses and deflectionsduring the various stages of removal and construction. Removal of the main longitudinal slab reinforce-ment should be kept to a minimum. See “Slab Removal Detail,” Figure 5.5-1, for the limiting case for themaximum allowable removal.

The plans should include a note that critical dimensions and elevations are to be verified in the field priorto the fabrication of precast units or expansion joint assemblies.

In cases where an existing sidewalk is to be removed but the supporting slab under the sidewalk is to beretained, district personnel should check the feasibility of removing the sidewalk. Prior to design, districtpersonnel should make recommendations on acceptable removal methods and required constructionequipment. The plans and specifications should then be prepared to accommodate these recommendations.This will ensure the constructibility of plan details and the adequacy of the specifications.

5.5.4 Attachment of Widening to Existing Structure

A. General

1. Lap and Mechanical Splices

To attach a widening to an existing structure, the first choice is to utilize existing reinforcingbars by splicing new bars to existing. Lap splices or mechanical splices should be used. However,it may not always be possible to splice to existing reinforcing bars and spacing limitations maymake it difficult to use mechanical splices.



5.5-8 July 2000

2. Welding Reinforcement

Existing reinforcing steel may not be readily weldable. Mechanical splices should be usedwherever possible. If welding is the only feasible means, the chemistry of the reinforcing steelmust be analyzed and acceptable welding procedures developed.

3. Drilling Into Existing Structure

It may be necessary to drill holes and set dowels in epoxy resin in order to attach the widening tothe existing structure.

When drilling into heavily reinforced areas, chipping should be specified to expose the mainreinforcing bars. If it is necessary to drill through reinforcing bars or if the holes are within4 inches of an existing concrete edge, core drilling should be specified. Core drilled holes shallbe roughened before resin is applied. If this is not done, a dried residue, which acts as a bondbreaker and reduces the load capacity of the dowel, will remain. Generally, the drilled holes are1/8 inch in diameter larger than the dowel diameter for #5 and smaller dowels and 1/4 inch indiameter larger than the dowel diameter for #6 and larger dowels.

In special applications requiring drilled holes greater than 11/2″ inch diameter or deeper than2 feet, core drilling shall be specified. These holes should also be intentionally roughened priorto applying epoxy resin.

Core drilled holes should have a minimum clearance of 3 inches from the edge of the concreteand 1-inch clearance from existing reinforcing bars in the existing structure. These clearancesshould be noted in the plans.

4. Dowelling Reinforcing Bars Into the Existing Structure

a. Dowel bars shall be set with an approved epoxy resin. The existing structural element shallbe checked for its adequacy to transmit the load transferred to it from the dowel bars.

b. Dowel spacing and edge distance affect the allowable tensile dowel loads [14]. Allowabletensile loads, dowel bar embedments, and drilled hole sizes for reinforcing bars (Grade 60)used as dowels and set with an approved epoxy resin are shown in Table 5.5-1. These valuesare based on an edge clearance greater than 3 inch, a dowel spacing greater than 6 inch, andare shown for both uncoated and epoxy coated dowels. Table 5.5-2 lists dowel embedmentlengths when the dowel spacing is less than 6 inch. Note that in Table 5.5-2 the edgeclearance is equal to or greater than 3 inch, because this is the minimum edge clearancefor a drilled hole from a concrete edge.

If it is not possible to obtain these embedments, such as for traffic railing dowels intoexisting deck slabs, the allowable load on the dowel shall be reduced by the ratio of theactual embedment divided by the required embedment.



July 2000 5.5-9

c. The embedments shown in Table 5.5-1 and -2 are based on dowels embedded in concretewith fc′=4,000 psi.

Allowable Tensile Load for Dowels Set With Epoxy Resin fc′=4,000 psi,Gr 60 Reinforcing Bars, Edge Clearance ≥ 3 in., and Spacing ≥ 6 in.[14]

Table 5.5-1

Allowable Design Drill Hole Required Embedment, Le**Bar Tensile Load, T* Size Uncoated Epoxy CoatedSize (kips) (in) (in) (in)

4 12.0 5/8 7 8

5 18.6 3/4 8 9

6 26.4 1 9 10

7 36.0 11/8 11 12

8 47.4 11/4 13 141/2

9 60.0 13/8 16 171/2

*Allowable Tensile Load (Strength Design) = (fy)(As).**Based on removed cover. In cases where concrete cover is not removed, the designer should add the cover thickness to the required embedment.

Allowable Tensile Load for Dowels Set With Epoxy Resin fc′=4,000 psi,Gr 60 Reinforcing Bars, Edge Clearance ≥ 3 in., and Spacing < 6 in.[14]

Table 5.5-2

Allowable Design Drill Hole Required Embedment, Le**Bar Tensile Load, T* Size Uncoated Epoxy CoatedSize (kips) (in) (in) (in)

4 12.0 5/8 91/2 101/2

5 18.6 3/4 101/2 111/2

6 26.4 1 111/2 121/2

7 36.0 11/8 131/2 158 47.4 11/4 161/2 189 60.0 13/8 20 22

*Allowable Tensile Load (Strength Design) = (fy)(As).**Based on removed cover. In cases where concrete cover is not removed, the designer should add the cover thickness to the required embedment.

5. Shear Transfer Across a Dowelled Joint

Shear should be carried across the joint by shear friction on an intentionally roughened surfaceinstead of depending on the dowels to transmit the shear force. Chipping shear keys in theexisting concrete can also be used to transfer shear across a dowelled joint, but is expensive.



5.5-10 July 2000

6. Preparation of Existing Surfaces for Concreting

See “Removing Portions of Existing Structure” in the General Special Provisions forrequirements. Unsound, damaged, dirty, porous, or otherwise undesirable old concrete should beremoved, and the remaining concrete surface should be clean, free of laitance, and intentionallyroughened to ensure proper bond between the old and new concrete surfaces.

7. Control of Shrinkage and Deflection on Connecting Reinforcement

Dowels that are fixed in the existing structure may be subject to shear as a result of longitudinalshrinkage and vertical deflection when the falsework is removed. These shear forces may resultin a reduced tensile capacity of the connection. When connecting the transverse reinforcing barsacross the closure strip is unavoidable, the interaction between shear and tension in the dowelor reinforcing bar should be checked. The use of wire rope or sleeved reinforcement may beacceptable, subject to approval by your supervisor.

Where possible, transverse reinforcing bars should be spliced to the existing reinforcing bars in ablocked-out area which can be included in the closure strip. Nominal, shear friction, temperatureand shrinkage, and distribution reinforcing bars should be bent into the closure strip.

Rock bolts may be used to transfer connection loads deep into the existing structure, subject tothe approval of your supervisor.

8. Post-Tensioning

Post-tensioning of existing crossbeams may be utilized to increase the moment capacity andto eliminate the need for additional substructure. Generally, an existing crossbeam can becore drilled for post-tensioning if it is less than 30 feet long. The amount of drift in the holesalignment may be approximately 1 inch in 20 feet. For crossbeams longer than 30 feet, externalpost-tensioning should be considered.

For an example of this application, refer to Contract 3846, Bellevue Transit Access — Stage 1.



July 2000 5.5-11

Slab Removal DetailFigure 5.5.-1

B. Connection Details

The details on the following sheets are samples of details which have been used for wideningbridges. They are informational and are not intended to restrict the designer’s judgment.



5.5-12 July 2000

1. Box Girder Bridges

Figures 5.5-2, -3, -4, and -5 show typical details for widening box girder bridges.

Box Girder Section in SpanFigure 5.5-2



July 2000 5.5-13

Box Girder Section Through X-BeamSee Box Girder Section in Span for additional details.

Figure 5.5-3

Welding or mechanical butt splice are preferred over dowelling for the main reinforcement in crossbeamsand columns when it can be done in the horizontal or flat position. It shall be allowed only when the barsto be welded are free from restraint at one end during the welding process.

**If bars are to be dowelled, provide a sufficient embedment depth for moment connection bars intoexisting structure that will provide the required moment capacity in the existing structure. See Table 5.5-1or 5.5-2.



5.5-14 July 2000

Box Girder Section in Span at Diaphragm Alternate IFigure 5.5-4



July 2000 5.5-15

Box Girder Section in Span at Diaphragm Alternate IIFigure 5.5-5



5.5-16 July 2000

2. Flat Slab Bridges

It is not necessary to remove any portion of the existing slab to expose the existing transversereinforcing bars for splicing purposes, because the transverse slab reinforcement is only distribu-tion reinforcement. The transverse slab reinforcement for the widening may be dowelled directlyinto the existing structure without meeting the normal splice requirements.

For the moment connection details, see Figure 5.5-6 for “Flat Slab — Section through X-Beam.”

Note: Falsework shall be maintained under pier crossbeams until closure pour is made and cured 10 days.

Flat Slab — Section through X-BeamFigure 5.5-6



July 2000 5.5-17

3. T-Beam Bridges

Use details similar to those for box girder bridges for crossbeam connections. See Figure 5.5-7for slab connection detail.

T-Beam — Section in SpanFigure 5.5-7



5.5-18 July 2000

4. Prestress Concrete Girder Bridges

Use details similar to those for box girder bridges for crossbeam moment connections and usedetails similar to those in Figure 5.5-8 for connecting to the slab.

Prestressed Girder — Section in SpanFigure 5.5-8



July 2000 5.5-19

5.5.5 Expansion Joints

The designer should determine if existing expansion joints can be eliminated. It will be necessary todetermine what modifications to the structure are required to provide an adequate functional system whenexisting joints are eliminated.

For expansion joint design, see Section 8.4.1 “Expansion Joints.” Very often on widening projects it isnecessary to chip out the existing concrete deck and rebuild the joint. Figures 5.5-9 and 5.5-10 showdetails for rebuilding joint openings for compression seal expansion joints.

If a widening project includes an overlay, the expansion joint may have to be raised, modified or replaced.See the Joint Specialist for plan details that are currently being used to modify or retrofit existingexpansion joints.

Expansion JointDetail Shown for Compression Seal — Existing Reinforcing Steel Saved

Figure 5.5-9



5.5-20 July 2000

Expansion JointDetail shown for compression seal with new reinforcing steed added.

Figure 5.5-10

5.5.6 Possible Future Widening for Current Designs

For current projects that include sidewalks (and where it is anticipated that the structure may be modifiedor widened in the future), provide a smooth rather than a rough construction joint between the sidewalkand the slab. This will normally pertain to flat slab bridges or where the sidewalk width exceeds the slabcantilever overhang.

5.5.7 Bridge Widening Falsework

For widenings which do not have additional girders, columns, crossbeams, or closure pours, flaseworkshould be supported by the existing bridge. There should be an external support from the ground. Thereason is that the ground support will not allow the widening to deflect the existing bridge when traffic ison the bridge. This will cause the “green” concrete to crack where it joins the existing bridge. Designershould contact the bridge construction support unit regarding fasework associated with widenings.



July 2000 5.5-21

5.5.8 Existing Bridge Widenings

The following listed bridge widenings are included as aid to the designer. These should not be construedas the only acceptable methods of widening; there is no substitute for the designer’s creativity or ingenuityin solving the challenges posed by bridge widenings.

Contract Type ofBridge SR No. Bridge Unusual Features

NE 8th Street U’Xing 405 9267 Ps. Gir. Pier replacements

Higgins Slough 536 9353 Flat Slab

ER17 and AR17 O-Xing 5 9478 Box Girder Middle and outside widening.

SR 538 O-Xing 5 9548 T-Beam Unbalanced widening section support atdiaphragms until completion of closure pour.

B-N O’Xing 5 9566 Box Girder Widened with P.S. Girders, X-beams, anddiaphragms not in line with existing jackingrequired to manipulate stresses, addedenclusure walls.

Blakeslee Jct. E/W 5 9638 T-Beam andBox Girder Post-tensioned X-beam, single web.

B-N O’Xing 18 9688 Box Girder

SR 536 9696 T-Beam Similar to Contract 9548.

LE Line over Yakima River 90 9806 Box Girder Pier shaft.

SR 18 O-Xing 90 9823 P.S. Girder Lightweight concrete.

Hamilton Road O-Xing 5 9894 T-Beam Precast girder in one span.

Dillenbauch Creek 5 Flat Slab

Longview Wye SR 432 U-Xing 5 P.S. Girder Bridge lengthening.

Klickitat River Bridge 142 P.S. Girder Bridge replacement.

Skagit River Bridge 5 Steel Truss Rail modification.

B-N O-Xing at Chehalis 5 Replacement of thru steel girder spanwith stringer span.

Bellevue Access EBCD Widening Flat Slab and Deep, soft soil. Stradle best replacingand Pier 16 Modification 90 3846 Box Girder single column.

Totem Lake/NE 124th I/C 405 3716 T-Beam Skew = 55 degrees.

Pacific Avenue I/C 5 3087 Box Girder Complex parallel skewed structures.

SR 705/SR 5 SB Added Lane 5 3345 Box Girder Multiple widen structures.

Mercer Slough Bridge 90/43S 3846 CIP Conc. Tapered widening of flat slab outriggerFlat Slab pier, combined footings.

Spring Street O-Xing CIP Conc. Tapered widening of box girder withNo. 5/545SCD 3845 Box Girder hingers, shafts.

Fishtrap Creek Bridge 546/8 3661 P.C. Units Widening of existing P.C. Units.Tight constraints on substructure.

Columbia Drive O-Xing 395/16 3379 Steel Girder Widening/Deck replacement using standardrolled sections.



5.5-22 July 2000

Contract Type ofBridge SR No. Bridge Unusual Features

S 74th-72nd St. O-Xing No. 5/426 3207 CIP Haunched Haunched P.C. P.T. Bath Tub girderCon. Box Girder sections.

Pacific Avenue O-Xing No. 5/332 3087 CIP Conc. Longitudinal joint between new andBox Girder existing.

Tye River Bridges 2/126 and 2/127 3565 CIP Conc. Stage construction with crown shift.Tee Beam

SR 20 and BNRR O-Xing No. 5/714 9220 CIP Conc. Widened with prestressed girdersTee Beam raised crossbeam.

NE 8th St. U’Xing No. 405/43 9267 Prestressed Pier replacement — widening.Girders

So. 212th St. U’Xing SR 167 3967 Prestressed Widening constructed as stand aloneGirders structure. Widening column designed

as strong column for retrofit.

SE 232nd St. SR 18 5801 CIP Conc. Skew = 50 degree. Longitudinal “linkPost-tensioned pin” deck joint between new andBox existing to accommodate new creep.

Obdashian Bridge 2/275 N/A CIP Post-tensioned Sidewalk widening with pipe struts.1999 Box

P65:DP/BDM5


Reinforced Concrete Superstructures Bibliography

July 2000 5.99-1

5.99 Bibliography

1. McCormac, J. C., Design of Reinforced Concrete, Harper & Row, New York, 1st Ed., 1978, 507 pp.

2. Wang, C.-K. and Salmon, C. G., Reinforced Concrete Design, Harper & Row, New York, 3rd Ed.,1979, 918 pp.

3. Park, R. and Pauley, T., Reinforced Concrete Design, John Wiley & Sons, New york, 1st ed., 1975,769 pp.

4. ACI 318-89, Building Code Requirements for Reinforced Concrete and Commentary, AmericanConcrete Institute, 1989, pp.353.

5. Ghosh, S. K. and Rabbat, B. G., Editors, Notes on ACI 318-89, Building Code Requirements forReinforced Concrete with Design Applications, Portland Cement Association, 5th ed., 1990.

6. ACI-ASCE Committee 343, Analysis and Design of Reinforced Concrete Bridge Structures,American Concrete Institute, 1988, 162 pp.

7. Hsu, T. T. C., Torsion of Reinforced Concrete, Van Nostrand Reinhold Co., New York, 1st Ed.,1984, 516 pp.

8. Collins, M. P. and Mitchell, D., Shear and Torsion Design of Prestressed and Non-PrestressedConcrete Beams, PCI Journal, September-October, 1980, pp. 32-100.

9. ACI Committee 317, Reinforced Concrete Design Handbook — Working Stress Method, PublicationSP-3, American Concrete Institute, 3rd Ed., 1965, 271 pp.

10. Mirza, S.A., and Furlong, R.W., Design of Reinforced and Prestressed Concrete Inverted T Beamsfor Bridge Structures, PCI Journal, Vol. 30, No. 4, July-August 1985, pp. 112-136.

11. Rabbat, B.G., Reader Comments Design of Reinforced and Prestressed Concrete inverted T Beamsfor Bridge Structures, PCI Journal, Vol. 31, No. 3, May-June 1986, pp. 157-163.

12. Supplement A, Standard Specifications for Seismic Design of Highway Bridges, AASHTO,Washington, D.C., 1991, pp. 14-16.

13. Standard Specifications for Highway Bridges, 16th Edition, AASHTO, Washington, D.C., 1996.

14. Babaei, K. and Hawkins, N. M., Bending/Straightening and Grouting Concrete Reinforcing Steel:Review of WSDOT’s Specifications and Proposed Modifications, Final Report WA-RD 168.1,Washington State Transportation Center (TRAC), December 1988, 75 pp.

15. ACI Committee 345, Guide for Widening Highway Bridges, ACI Structural Journal, July/August,1992, pp. 451-466.

16. AASHTO LRFD Specifications, 2nd Edition, AASHTO, Washington, D.C., 1998.

P65:DP/BDM5

July 2000 5.1-A1

Nominal Outside Maximum NormalWeight Diameter* Diameter Bar Length Bar Length

Size (lbs/ft) (in) (in) Area (in 2) (ft) (ft)

#3 0.376 3/8″ 0.42 0.11 40′ 30′

#4 0.668 1/2″ 0.56 0.20 40′ 40′

#5 1.043 5/8″ 0.70 0.31 60′ 40′

#6 1.502 3/4″ 0.83 0.44 60′ 60′

#7 2.044 7/8″ 0.96 0.60 60′ 60′

#8 2.670 1″ 1.10 0.79 72′** 60′

#9 3.400 1.13 (11/8″) 1.24 1.00 72′** 60′

#10 4.303 1.27 (11/4″) 1.40 1.27 72′** 60′

#11 5.313 1.41 (13/8″) 1.55 1.56 90′** 60′

#14 7.650 1.69 (13/4″) 1.86 2.25 90′** 60′

#18 13.600 2.26 (11/4″) 2.48 4.00 90′** 60′

*Normally 1/8 per bar size number.

**Requires large special order. Since these lengths may pose problems in transporting and handling, get your supervisor’s approval before using them. See Chapter 5, Section 5.1.2F.

Note: For sizes > #9, area and weight are based on the decimal diameter.

Table 5.1-A1


Reinforced Concrete Superstructures Reinforcing Bar Properties

5.1-A2 July 2000

(Reinforcing Bars AASHTO M31)

Bar Size

#3 #4 #5 #6 #7 #8 #9 #10 #11 #14 #18

Spacing 3″ 0.44 0.80

31/4 0.41 0.74 1.14

31/2 0.38 0.69 1.06 1.51 2.06

33/4 0.35 0.64 0.99 1.41 1.92 2.53 3.20

4 0.33 0.60 0.93 1.32 1.80 2.37 3.00 3.81 4.68

41/4 0.31 0.56 0.88 1.24 1.69 2.23 2.82 3.59 4.40

41/2 0.29 0.53 0.83 1.17 1.60 2.11 2.67 3.39 4.16 6.00

43/4 0.28 0.51 0.78 1.11 1.52 2.00 2.53 3.21 3.94 5.68

5 0.26 0.48 0.74 1.06 1.44 1.90 2.40 3.05 3.74 5.40

51/4 0.25 0.46 0.71 1.01 1.37 1.81 2.29 2.90 3.57 5.14

51/2 0.24 0.44 0.68 0.96 1.31 1.72 2.18 2.77 3.40 4.91

53/4 0.23 0.42 0.65 0.92 1.25 1.65 2.09 2.65 3.26 4.70 8.35

6 0.22 0.40 0.62 0.88 1.20 1.58 2.00 2.54 3.12 4.50 8.00

61/2 0.20 0.37 0.57 0.81 1.11 1.46 1.85 2.35 2.88 4.15 7.38

7 0.19 0.34 0.53 0.75 1.03 1.35 1.71 2.18 2.67 3.86 6.86

71/2 0.18 0.32 0.50 0.70 0.96 1.26 1.60 2.03 2.50 3.60 6.40

8 0.17 0.30 0.47 0.66 0.90 1.19 1.50 1.91 2.34 3.38 6.00

81/2 0.16 0.28 0.44 0.62 0.85 1.12 1.41 1.79 2.20 3.18 5.65

9 0.15 0.27 0.41 0.59 0.80 1.05 1.33 1.69 2.08 3.00 5.33

91/2 0.14 0.25 0.39 0.56 0.76 1.00 1.26 1.60 1.97 2.84 5.05

10 0.13 0.24 0.37 0.53 0.72 0.95 1.20 1.52 1.87 2.70 4.80

101/2 0.13 0.23 0.35 0.50 0.69 0.90 1.14 1.45 1.78 2.57 4.57

11 0.12 0.22 0.34 0.48 0.65 0.86 1.09 1.39 1.70 2.45 4.36

111/2 0.11 0.21 0.32 0.46 0.63 0.82 1.04 1.33 1.63 2.35 4.17

As Per Foot of BarTable 5.1-A2


Reinforced Concrete Superstructures Bar Area vs. Bar Spacing

July 2000 5.1-A3

Areas for Various Bar Sizes and Number of BarsTable 5.1-A3

Size No. #3 #4 #5 #6 #7 #8 #9 #10 #11 #14 #18

1 0.11 0.20 0.31 0.44 0.60 0.79 1.00 1.27 1.56 2.25 4.00

2 0.22 0.40 0.62 0.88 1.20 1.58 2.00 2.54 3.12 4.50 8.00

3 0.33 0.60 0.93 1.32 1.80 2.37 3.00 3.81 4.68 6.75 12.00

4 0.44 0.80 1.24 1.76 2.40 3.16 4.00 5.08 6.24 9.00 16.00

5 0.55 1.00 1.55 2.20 3.00 3.95 5.00 6.35 7.80 11.25 20.00

6 0.66 1.20 1.86 2.64 3.60 4.74 6.00 7.62 9.36 13.50 24.00

7 0.77 1.40 2.17 3.08 4.20 5.53 7.00 8.89 10.92 15.75 28.00

8 0.88 1.60 2.48 3.52 4.80 6.32 8.00 10.16 12.48 18.00 32.00

9 0.99 1.80 2.79 3.96 5.40 7.11 9.00 11.43 14.04 20.25 36.00

10 1.10 2.00 3.10 4.40 6.00 7.90 10.00 12.70 15.60 22.50 40.00

11 1.21 2.20 3.41 4.84 6.60 8.69 11.00 13.97 17.16 24.75 44.00

12 1.32 2.40 3.72 5.28 7.20 9.48 12.00 15.24 18.72 27.00 48.00

13 1.43 2.60 4.03 5.72 7.80 10.27 13.00 16.51 20.28 29.25 52.00

14 1.54 2.80 4.34 6.16 8.40 11.06 14.00 17.78 21.84 31.50 56.00

15 1.65 3.00 4.65 6.60 9.00 11.85 15.00 19.05 23.40 33.75 60.00

16 1.76 3.20 4.96 7.04 9.60 12.64 16.00 20.32 24.96 36.00 64.00

17 1.87 3.40 5.27 7.48 10.20 13.43 17.00 21.59 26.52 38.25 68.00

18 1.98 3.60 5.58 7.92 10.80 14.22 18.00 22.86 28.08 40.50 72.00

19 2.09 3.80 5.89 8.36 11.40 15.01 19.00 24.13 29.64 42.75 76.00

20 2.20 4.00 6.20 8.80 12.00 15.80 20.00 25.40 31.20 45.00 80.00

21 2.31 4.20 6.51 9.24 12.60 16.59 21.00 26.67 32.76 47.25 84.00

22 2.42 4.40 6.82 9.68 13.20 17.38 22.00 27.94 34.32 49.50 88.00

23 2.53 4.60 7.13 10.12 13.80 18.17 23.00 29.21 35.88 51.75 92.00

24 2.64 4.80 7.44 10.56 14.40 18.96 24.00 30.48 37.44 54.00 96.00

25 2.75 5.00 7.75 11.00 15.00 19.75 25.00 31.75 39.00 56.25 100.00

26 2.86 5.20 8.06 11.44 15.60 20.54 26.00 33.02 40.56 58.50 104.00

27 2.97 5.40 8.37 11.88 16.20 21.33 27.00 34.29 42.12 60.75 108.00

28 3.08 5.60 8.68 12.32 16.80 22.12 28.00 35.56 43.68 63.00 112.00

29 3.19 5.80 8.99 12.76 17.40 22.91 29.00 36.83 45.24 65.25 116.00

30 3.30 6.00 9.30 13.20 18.00 23.70 30.00 38.10 46.80 67.50 120.00


Reinforced Concrete Superstructures Bar Area vs. Number of Bars

5.1-A4 July 2000

Tension Development Length of Uncoated Deformed Barsfc′ = 3,000 psi f c′ = 4,000 psi f c′ = 5,000 psi f c′ = 6,000 psi

Top Bars Others Top Bars Others Top Bars Others Top Bars OthersBar Size ft-in ft-in ft-in ft-in ft-in ft-in ft-in ft-in

3 1′-5″ 1′-0″ 1′-5″ 1′-0″ 1′-5″ 1′-0″ 1′-5″ 1′-0″4 1′-5″ 1′-0″ 1′-5″ 1′-0″ 1′-5″ 1′-0″ 1′-5″ 1′-0″5 1′-9″ 1′-3″ 1′-9″ 1′-3″ 1′-9″ 1′-3″ 1′-9″ 1′-3″6 2′-3″ 1′-8″ 2′-2″ 1′-6″ 2′-2″ 1′-6″ 2′-2″ 1′-6″7 3′-1″ 2′-3″ 2′-8″ 1′-11″ 2′-6″ 1′-9″ 2′-6″ 1′-9″8 4′-1″ 2′-11″ 3′-6″ 2′-6″ 3′-2″ 2′-3″ 2′-11″ 2′-1″9 5′-2″ 3′-8″ 4′-6″ 3′-2″ 4′-0″ 2′-10″ 3′-8″ 2′-7″

10 6′-6″ 4′-8″ 5′-8″ 4′-1″ 5′-1″ 3′-8″ 4′-8″ 3′-4″11 8′-0″ 5′-9″ 6′-11″ 5′-0″ 6′-3″ 4′-5″ 5′-8″ 4′-1″14 10′-11″ 7′-10″ 9′-5″ 9′-9″ 8′-5″ 6′-1″ 7′-9″ 5′-6″18 14′-1″ 10′-1″ 12′-3″ 8′-9″ 10′-11″ 7′-10″ 10′-0″ 7′-2″

Top Bars are so placed that more than 12″ of concrete is cast below the reinforcement. Modification Factor for Spacing >=6″ and side cover >=3″= 0.8. Minimum Development Length = 12″. Modification Factor for Reinforcement Enclosed in Spiral = 0.75

Table 5.1-A4

Tension Development Length of Epoxy Coated Deformed Barsfc′ = 3,000 psi f c′ = 4,000 psi f c′ = 5,000 psi f c′ = 6,000 psi


3 1′-9″ 1′-6″ 1′-9″ 1′-6″ 1′-9″ 1′-6″ 1′-9″ 1′-6″4 1′-9″ 1′-6″ 1′-9″ 1′-6″ 1′-9″ 1′-6″ 1′-9″ 1′-6″5 2′-2″ 1′-11″ 2′-2″ 1′-11″ 2′-2″ 1′-11″ 2′-2″ 1′-11″6 2′-9″ 2′-5″ 2′-7″ 2′-3″ 2′-7″ 2′-3″ 2′-7″ 2′-3″7 3′-9″ 3′-4″ 3′-3″ 2′-11″ 3′-0″ 2′-8″ 3′-0″ 2′-8″8 4′-11″ 4′-4″ 4′-3″ 3′-9″ 3′-10″ 3′-5″ 3′-6″ 3′-1″9 6′-3″ 5′-6″ 5′-5″ 4′-9″ 4′-10″ 4′-3″ 4′-5″ 3′-11″

10 7′-11″ 7′-0″ 6′-10″ 6′-1″ 6′-2″ 5′-5″ 5′-7″ 4′-11″11 9′-9″ 8′-7″ 8′-5″ 7′-5″ 7′-6″ 6′-8″ 6′-11″ 6′-1″14 13′-3″ 11′-8″ 11′-6″ 10′-1″ 10′-3″ 9′-1″ 9′-4″ 8′-3″18 17′-1″ 15′-1″ 14′-10″ 13′-1″ 13′-3″ 11′-8″ 12′-1″ 10′-8″

Tension Development Length of Standard 90 ° and 180° Hooksfc′ = 3,000 psi f c′ = 4,000 psi f c′ = 5,000 psi f c′ = 6,000 psi

Side Cover Side Cover Side Cover Side Cover Side Cover Side Cover Side Cover Side Cover< 21/2″ Cover >= 2 1/2″ Cover < 2 1/2″ Cover >= 2 1/2″ Cover < 2 1/2″ Cover >= 2 1/2″ Cover < 2 1/2″ Cover >= 2 1/2″ Cover

Bar Size on Tail < 2 ″ on Tail >= 2 ″ on Tail < 2 ″ on Tail >= 2 ″ on Tail < 2 ″ on Tail >= 2 ″ on Tail < 2 ″ on Tail >= 2 ″

3 0′-9″ 0′-6″ 0′-8″ 0′-6″ 0′-7″ 0′-6″ 0′-6″ 0′-6″4 0′-11″ 0′-8″ 0′-10″ 0′-7″ 0′-9″ 0′-7″ 0′-8″ 0′-7″5 1′-2″ 0′-10″ 1′-0″ 0′-9″ 0′-11″ 0′-8″ 0′-10″ 0′-7″6 1′-5″ 1′-0″ 1′-3″ 0′-10″ 1′-1″ 0′-9″ 1′-0″ 0′-8″7 1′-8″ 1′-2″ 1′-5″ 1′-0″ 1′-3″ 0′-11″ 1′-2″ 0′-10″8 1′-10″ 1′-4″ 1′-7″ 1′-2″ 1′-5″ 1′-0″ 1′-4″ 0′-11″9 2′-1″ 1′-6″ 1′-10″ 1′-3″ 1′-8″ 1′-2″ 1′-6″ 1′-1″

10 2′-4″ 1′-8″ 2′-1″ 1′-5″ 1′-10″ 1′-3″ 1′-8″ 1′-2″11 2′-7″ 1′-10″ 2′-3″ 1′-7″ 2′-0″ 1′-5″ 1′-10″ 1′-4″14 3′-1″ 3′-1″ 2′-9″ 2′-9″ 2′-5″ 2′-5″ 2′-3″ 2′-3″18 4′-2″ 4′-2″ 3′-7″ 3′-7″ 3′-3″ 3′-3″ 2′-11″ 2′-11″


Reinforced Concrete Superstructures

Table 5.1-A5

July 2000 5.1-A5

Tension Lap Splice Lengths of Grade 60 Uncoated Bars – Class Bfc′ = 3,000 psi f c′ = 4,000 psi f c′ = 5,000 psi f c′ = 6,000 psi


3 2′-0″ 2′-0″ 2′-0″ 2′-0″ 2′-0″ 2′-0″ 2′-0″ 2′-0″4 2′-0″ 2′-0″ 2′-0″ 2′-0″ 2′-0″ 2′-0″ 2′-0″ 2′-0″5 2′-4″ 2′-0″ 2′-4″ 2′-0″ 2′-4″ 2′-0″ 2′-4″ 2′-0″6 2′-11″ 2′-1″ 2′-9″ 2′-0″ 2′-9″ 2′-0″ 2′-9″ 2′-0″7 4′-0″ 2′-11″ 3′-6″ 2′-6″ 3′-3″ 2′-4″ 3′-3″ 2′-4″8 5′-3″ 3′-9″ 4′-7″ 3′-3″ 4′-11″ 2′-11″ 3′-9″ 2′-8″9 6′-8″ 4′-9″ 5′-9″ 4′-2″ 5′-2″ 3′-9″ 4′-9″ 3′-5″

10 8′-6″ 6′-1″ 7′-4″ 5′-3″ 6′-7″ 4′-8″ 6′-0″ 4′-4″11 10′-5″ 7′-5″ 9′-0″ 6′-5″ 8′-1″ 5′-9″ 7′-4″ 5′-3″14 Lap Splices Lap Splices Lap Splices Lap Splices18 Not Allowed Not Allowed Not Allowed Not Allowed

Top Bars are so placed that more than 12″ of concrete is cast below the reinforcement.

Definition of Splice Classes: Class A: Low stressed bars – 75% or less are splicedClass B: Low stressed bars – more than 75% are spliced

High stressed bars – 1/2 or less are splicedClass C: High stressed bars – more than 50% are spliced

Class B Lap splice is the preferred and most commonly used by bridge office.

Modification Factor for Class A: 0.77Modification Factor for Class C: 1.31Modification Factor for 3-bar Bundle = 1.2

Tension Lap Splice Lengths of Grade 60 Epoxy Coated Bars – Class Bfc′ = 3,000 psi f c′ = 4,000 psi f c′ = 5,000 psi f c′ = 6,000 psi


3 2′-3″ 2′-0″ 2′-3″ 2′-0″ 2′-3″ 2′-0″ 2′-3″ 2′-0″4 2′-3″ 2′-0″ 2′-3″ 2′-0″ 2′-3″ 2′-0″ 2′-3″ 2′-0″5 2′-10″ 2′-6″ 2′-10″ 2′-6″ 2′-10″ 2′-6″ 2′-10″ 2′-6″6 3′-7″ 3′-2″ 3′-4″ 3′-0″ 3′-4″ 3′-0″ 3′-4″ 3′-0″7 4′-11″ 4′-4″ 4′-3″ 3′-9″ 3′-11″ 3′-5″ 3′-11″ 3′-5″8 6′-5″ 5′-8″ 5′-7″ 4′-11″ 5′-0″ 4′-5″ 4′-6″ 4′-0″9 8′-1″ 7′-2″ 7′-0″ 6′-2″ 6′-3″ 5′-7″ 5′-9″ 5′-1″

10 10′-3″ 9′-1″ 8′-11″ 7′-10″ 8′-0″ 7′-0″ 7′-3″ 6′-5″11 12′-8″ 11′-2″ 10′-11″ 9′-8″ 9′-9″ 8′-0″ 8′-11″ 7′-11″14 Lap Splices Lap Splices Lap Splices Lap Splices18 Not Allowed Not Allowed Not Allowed Not Allowed


Reinforced Concrete Superstructures

Table 5.1-A6

5.1-A6 July 2000

Concrete f c′ = 3,000 psi f c′ = 4,000 psi f c′ = 5,000 psi f c′ = 6,000 psi f c′ > 3,000 psi

Reinf. Grade 60 Grade 60 Grade 60 Grade 60 Grade 60

Bar MinimumSize Development Length, l d Lap Splice

3 & 4 1′-0″* 1′-0″* 1′-0″* 1′-0″* 2′-0″4

5 1′-2″ 1′-0″ 1′-0″* 1′-0″* 2′-0″4

6 1′-5″ 1′-3″ 1′-2″ 1′-2″ 2′-0″4

7 1′-8″ 1′-5″ 1′-4″ 1′-4″ 2′-3″

8 1′-10″ 1′-7″ 1′-6″ 1′-6″ 2′-6″

9 2′-1″ 1′-10″ 1′-9″ 1′-9″ 2′-10″

10 2′-4″ 2′-1″ 1′-11″ 1′-11″ 3′-3″

11 2′-7″ 2′-3″ 2′-2″ 2′-2″ 3′-7″

14 3′-1″ 2′-9″ 2′-7″ 2′-7″ 4′-3″

18 4′-2″ 3′-7″ 3′-5″ 3′-5″ 5′-8″

Note:1. Where excess bar area is provided, ld may be reduced by the ratio of required area to area provided.2. *1′-0″ minimum (office practice).3. ld (compression) must be developed with straight bar extension. Reduced length noted in (1) shall also be

straight bar extension.4. 2′-0″ minimum (office practice).5. When splicing smaller bars to larger bars, the lap splice shall be the larger of the minimum compression lap

splice or the development length of the larger bar in compression, AASHTO Art. 8.32.4.1.

Table 5.1-A7

Development Length of Deformed Bars inCompression and Minimum Compression Lap Splice

Per AASHTO Standard Specifications, 1991, 16th Edition Articles 8.26, 8.32.4


Minimum Development Length and MinimumReinforced Concrete Superstructures Lap Splices of Deformed Bars in Compression

July 2000 5.2-A1

0.0010 59.3 0.0053 298.1 0.0097 515.4 0.0141 705.20.0011 65.1 0.0054 303.4 0.0098 520.0 0.0142 709.20.0012 71.0 0.0055 308.6 0.0099 524.6 0.0143 713.20.0013 76.8 0.0056 313.8 0.0100 529.2 0.0144 717.20.0014 82.6 0.0057 319.0 0.0101 533.8 0.0145 721.10.0015 88.4 0.0058 324.2 0.0102 538.3 0.0146 725.10.0016 94.2 0.0059 329.4 0.0103 542.9 0.0147 729.00.0017 100.0 0.0060 334.5 0.0104 547.4 0.0148 732.90.0018 105.7 0.0061 339.7 0.0105 551.9 0.0149 736.80.0019 111.4 0.0062 344.8 0.0106 556.4 0.0150 740.70.0020 117.2 0.0063 349.9 0.0107 560.9 0.0151 744.60.0021 122.9 0.0064 355.0 0.0108 565.4 0.0152 748.40.0022 128.6 0.0065 360.1 0.0109 569.9 0.0153 752.30.0023 134.3 0.0066 365.2 0.0110 574.3 0.0154 756.10.0024 139.9 0.0067 370.2 0.0111 578.8 0.0155 759.90.0025 145.6 0.0068 375.3 0.0112 583.2 0.0156 763.70.0026 151.2 0.0069 380.3 0.0113 587.6 0.0157 767.50.0027 156.8 0.0070 385.3 0.0114 592.0 0.0158 771.20.0028 162.4 0.0071 390.3 0.0115 596.4 0.0159 775.00.0029 168.0 0.0072 395.0 0.0116 600.7 0.0160 778.70.0030 173.6 0.0073 400.3 0.0117 605.1 0.0161 782.50.0031 179.2 0.0074 405.2 0.0118 609.40.0032 184.8 0.0075 410.2 0.0119 613.70.0033 190.3 0.0076 415.1 0.0120 618.00.0034 195.8 0.0077 420.0 0.0121 622.30.0035 201.3 0.0078 424.9 0.0122 626.60.0036 206.8 0.0079 429.8 0.0123 630.90.0037 212.3 0.0080 434.7 0.0124 635.10.0038 217.8 0.0081 439.5 0.0125 639.40.0039 223.2 0.0082 444.4 0.0126 643.60.0040 228.7 0.0083 449.2 0.0127 647.80.0041 234.1 0.0084 454.0 0.0128 652.00.0042 239.5 0.0085 458.8 0.0129 656.20.0043 244.9 0.0086 463.6 0.0130 660.30.0044 250.3 0.0087 468.4 0.0131 664.50.0045 255.7 0.0088 473.2 0.0132 668.60.0046 261.0 0.0089 477.9 0.0133 672.80.0047 266.4 0.0090 482.6 0.0134 676.90.0048 271.7 0.0091 487.4 0.0135 681.00.0049 277.0 0.0092 492.1 0.0136 685.00.0050 282.3 0.0093 496.8 0.0137 689.10.0051 287.6 0.0094 501.4 0.0138 693.20.0052 292.9 0.0095 506.1 0.0139 697.2

0.0096 510.7 0.0140 701.2

Notes:1. Units of are in psi.

2. ρmin should be based on 1.2 Mcr or 1.33 ρ analysis, whichever is smaller.3. ρmax = 0.75ρb = 0.0161 based on β1 = 0.85.

Table 5.2-A1

ρ ρ ρ ρMu Mu Mu Mu

φbd2 φbd2 φbd2 φbd2

Mu

ρbd2

ρmax

BRIDGE DESIGN MANUALAppendix A ρ Values for Singly

Reinforced BeamsReinforced Concrete Superstructures fc′ = 3,000 psi fy = 60,000 psi

5.2-A2 July 2000



0.0010 59.5 0.0056 319.3 0.0102 556.7 0.0148 771.7 0.0194 964.10.0011 65.4 0.0057 324.7 0.0103 561.7 0.0149 776.1 0.0195 968.10.0012 71.2 0.0058 330.1 0.0104 566.6 0.0150 780.5 0.0196 972.00.0013 77.1 0.0059 335.5 0.0105 571.5 0.0151 784.9 0.0197 975.90.0014 83.0 0.0060 340.9 0.0106 576.3 0.0152 789.3 0.0198 979.80.0015 88.8 0.0061 346.2 0.0107 581.2 0.0153 793.7 0.0199 983.70.0016 94.6 0.0062 351.6 0.0108 586.1 0.0154 798.1 0.0200 987.60.0017 100.5 0.0063 356.9 0.0109 590.9 0.0155 802.4 0.0201 991.50.0018 106.3 0.0064 362.2 0.0110 595.7 0.0156 806.8 0.0202 995.30.0019 112.1 0.0065 367.6 0.0111 600.6 0.0157 811.1 0.0203 999.20.0020 117.9 0.0066 372.9 0.0112 605.4 0.0158 815.4 0.0204 1003.00.0021 123.7 0.0067 378.2 0.0113 610.2 0.0159 819.7 0.0205 1006.80.0022 129.4 0.0068 383.4 0.0114 615.0 0.0160 824.1 0.0206 1010.70.0023 135.2 0.0069 388.7 0.0115 619.8 0.0161 828.3 0.0207 1014.50.0024 140.9 0.0070 394.0 0.0116 624.5 0.0162 832.6 0.0208 1018.30.0025 146.7 0.0071 399.2 0.0117 629.3 0.0163 836.9 0.0209 1022.00.0026 152.4 0.0072 404.5 0.0118 634.1 0.0164 841.2 0.0210 1025.80.0027 158.1 0.0073 409.7 0.0119 638.8 0.0165 845.4 0.0211 1029.60.0028 163.8 0.0074 414.9 0.0120 643.5 0.0166 849.7 0.0212 1033.30.0029 169.5 0.0075 420.1 0.0121 648.2 0.0167 853.9 0.0213 1037.10.0030 175.2 0.0076 425.3 0.0122 653.0 0.0168 858.1 0.0214 1040.80.0031 180.9 0.0077 430.5 0.0123 657.7 0.0169 862.30.0032 186.6 0.0078 435.7 0.0124 662.3 0.0170 866.50.0033 192.2 0.0079 440.9 0.0125 667.0 0.0171 870.70.0034 197.9 0.0080 446.0 0.0126 671.7 0.0172 874.90.0035 203.5 0.0081 451.2 0.0127 676.3 0.0173 879.10.0036 209.1 0.0082 456.3 0.0128 681.0 0.0174 883.20.0037 214.7 0.0083 461.4 0.0129 685.6 0.0175 887.40.0038 220.3 0.0084 466.5 0.0130 690.3 0.0176 891.50.0039 225.9 0.0085 471.6 0.0131 694.9 0.0177 895.60.0040 231.5 0.0086 476.7 0.0132 699.5 0.0178 899.70.0041 237.1 0.0087 481.8 0.0133 704.1 0.0179 903.90.0042 242.6 0.0088 486.9 0.0134 708.6 0.0180 907.90.0043 248.2 0.0089 491.9 0.0135 713.2 0.0181 912.00.0044 253.7 0.0090 497.0 0.0136 717.8 0.0182 916.10.0045 259.2 0.0091 502.0 0.0137 722.3 0.0183 920.20.0046 264.8 0.0092 507.1 0.0138 726.9 0.0184 924.20.0047 270.3 0.0093 512.1 0.0139 731.4 0.0185 928.30.0048 275.8 0.0094 517.1 0.0140 735.9 0.0186 932.30.0049 281.2 0.0095 522.1 0.0141 740.4 0.0187 936.30.0050 286.7 0.0096 527.1 0.0142 744.9 0.0188 940.30.0051 292.2 0.0097 532.0 0.0143 749.4 0.0189 944.30.0052 297.6 0.0098 537.0 0.0144 753.9 0.0190 948.30.0053 303.1 0.0099 542.0 0.0145 758.3 0.0191 952.30.0054 308.5 0.0100 546.9 0.0146 762.8 0.0192 956.20.0055 313.9 0.0101 551.8 0.0147 767.2 0.0193 960.2Notes:1. Units of are in psi.2. ρmin should be based on 1.2 Mcr or 1.33 ρ analysis, whichever is smaller.3. ρmax = 0.75ρb = 0.0214 based on β1 = 0.85.

Table 5.2-A2

ρmax

Mu

ρbd2

ρ ρ ρ ρ ρMu Mu Mu Mu Muφbd2 φbd2 φbd2 φbd2 φbd2

July 2000 5.2-A3

0.0010 59.6 0.0061 350.2 0.0113 623.8 0.0165 874.3 0.0217 1102.00.0011 65.5 0.0062 355.7 0.0114 628.8 0.0166 878.9 0.0218 1106.10.0012 71.4 0.0063 361.1 0.0115 633.8 0.0167 883.5 0.0219 1110.30.0013 77.3 0.0064 366.6 0.0116 638.8 0.0168 888.1 0.0220 1114.40.0014 83.2 0.0065 372.1 0.0117 643.8 0.0169 892.7 0.0221 1118.50.0015 89.0 0.0066 377.5 0.0118 648.9 0.0170 897.2 0.0222 1122.60.0016 94.9 0.0067 382.9 0.0119 653.8 0.0171 901.8 0.0223 1126.80.0017 100.8 0.0068 388.4 0.0120 658.8 0.0172 906.3 0.0224 1130.90.0018 106.6 0.0069 393.8 0.0121 663.8 0.0173 910.9 0.0225 1134.90.0019 112.5 0.0070 399.2 0.0122 668.8 0.0174 915.4 0.0226 1139.00.0020 118.3 0.0071 404.6 0.0123 673.7 0.0175 919.9 0.0227 1143.10.0021 124.1 0.0072 410.0 0.0124 678.7 0.0176 924.4 0.0228 1147.20.0022 129.9 0.0073 415.4 0.0125 683.6 0.0177 928.9 0.0229 1151.20.0023 135.8 0.0074 420.7 0.0126 688.6 0.0178 933.4 0.0230 1155.30.0024 141.6 0.0075 426.1 0.0127 693.5 0.0179 937.9 0.0231 1159.30.0025 147.3 0.0076 431.5 0.0128 698.4 0.0180 942.4 0.0232 1163.40.0026 153.1 0.0077 436.8 0.0129 703.3 0.0181 946.8 0.0233 1167.40.0027 158.9 0.0078 442.2 0.0130 708.2 0.0182 951.3 0.0234 1171.40.0028 164.7 0.0079 447.5 0.0131 713.1 0.0183 955.7 0.0235 1175.40.0029 170.4 0.0080 452.8 0.0132 718.0 0.0184 960.2 0.0236 1179.40.0030 176.2 0.0081 458.1 0.0133 722.9 0.0185 964.6 0.0237 1183.40.0031 181.9 0.0082 463.4 0.0134 727.7 0.0186 969.0 0.0238 1187.40.0032 187.7 0.0083 468.7 0.0135 732.6 0.0187 973.5 0.0239 1191.40.0033 193.4 0.0084 474.0 0.0136 737.4 0.0188 977.9 0.0240 1195.30.0034 199.1 0.0085 479.3 0.0137 742.3 0.0189 982.3 0.0241 1199.30.0035 204.8 0.0086 484.6 0.0138 747.1 0.0190 986.6 0.0242 1203.20.0036 210.5 0.0087 489.8 0.0139 751.9 0.0191 991.0 0.0243 1207.20.0037 216.2 0.0088 495.1 0.0140 756.7 0.0192 995.4 0.0244 1211.10.0038 221.9 0.0089 500.4 0.0141 761.5 0.0193 999.8 0.0245 1215.00.0039 227.5 0.0090 505.6 0.0142 766.3 0.0194 1004.1 0.0246 1218.90.0040 233.2 0.0091 510.8 0.0143 771.1 0.0195 1008.5 0.0247 1222.80.0041 238.9 0.0092 516.0 0.0144 775.9 0.0196 1012.8 0.0248 1226.70.0042 244.5 0.0093 521.3 0.0145 780.7 0.0197 1017.1 0.0249 1230.60.0043 250.1 0.0094 526.5 0.0146 785.4 0.0198 1021.5 0.0250 1234.50.0044 255.8 0.0095 531.7 0.0147 790.2 0.0199 1025.8 0.0251 1238.40.0045 261.4 0.0096 536.9 0.0148 795.0 0.0200 1030.1 0.0252 1242.20.0046 267.0 0.0097 542.0 0.0149 799.7 0.0201 1034.40.0047 272.6 0.0098 547.2 0.0150 804.4 0.0202 1038.70.0048 278.2 0.0099 552.4 0.0151 809.1 0.0203 1042.90.0049 283.8 0.0100 557.5 0.0152 813.9 0.0204 1047.20.0050 289.4 0.0101 562.7 0.0153 818.6 0.0205 1051.50.0051 295.0 0.0102 567.8 0.0154 823.3 0.0206 1055.70.0052 300.5 0.0103 572.9 0.0155 827.9 0.0207 1060.00.0053 306.1 0.0104 578.1 0.0156 832.6 0.0208 1064.20.0054 311.6 0.0105 583.2 0.0157 837.3 0.0209 1068.40.0055 317.1 0.0106 588.3 0.0158 842.0 0.0210 1072.70.0056 322.7 0.0107 593.4 0.0159 846.6 0.0211 1076.90.0057 328.2 0.0108 598.5 0.0160 851.3 0.0212 1081.10.0058 333.7 0.0109 603.5 0.0161 855.9 0.0213 1085.30.0059 339.2 0.0110 608.6 0.0162 860.5 0.0214 1089.50.0060 344.7 0.0111 613.7 0.0163 865.1 0.0215 1093.6

0.0112 618.7 0.0164 869.7 0.0216 1097.8Notes:1. Units of are in psi.2. ρmin should be based on 1.2 Mcr or 1.33 ρ analysis, whichever is smaller.3. ρmax = 0.75ρb = 0.0252 based on β1 = 0.80.

Table 5.2-A3



ρ ρ ρ ρ ρMu Mu Mu Mu Muφbd2 φbd2 φbd2 φbd2 φbd2

Mu

ρbd2

ρmax

July 2000 5.3-A1


Reinforced Concrete Superstructures Positive Moment Reinforcement

Figure 5.3-A1

5.3-A2 July 2000


Reinforced Concrete Superstructures Negative Moment Reinforcement

Figure 5.3-A2

July 2000 5.3-A3

BRIDGE DESIGN MANUALAppendix A Adjusted Negative Moment

Case I (Design for M @Reinforced Concrete Superstructures Face of Effective Support)

Figure 5.3-A3

5.3-A4 July 2000


Adjusted Negative MomentReinforced Concrete Superstructures Case II (Design for M @ 1/4 Point)

Figure 5.3-A4

July 2000 5.3-A5


Load Factor Slab DesignReinforced Concrete Superstructures fc′ = 4,000 psi

Figure 5.3-A5

5.3-A6 July 2000


Load Factor Slab DesignReinforced Concrete Superstructures fc′ = 5,000 psi

Figure 5.3-A6

July 2000 5.3-A7


Reinforced Concrete Superstructures Slab Design — Traffic Barrier Load

Notes:

1. Section “A-A” is taken to be the critical section. Other sections ordinarily do not need to be investigated.

2. Provide enough extension to the left of “A-A” to develop the As required (usually will require hooking bars).

3. Service Load fs = 20,000, Load Factor = (1.3D + 2.17L).

4. For Load Factor design, check distribution of flexural reinforcement — AASHTO 8.16-8.4. If #5 or #6 barsare used to furnish the As from this chart, then this requirement will not have to be checked.

Figure 5.3-A7

July 2000 5.2-B1-1


Reinforced Concrete Superstructures Slab Design

Example 5.2-B1

Given: Center-to-center spacing of girders = 12 feet 3 inchesWidth of top flange of steel girder = 18 inches wideDeck concrete, Class 4000 fc′ = 4,000 psiReinforcing steel, Grade 60 fy = 60,000 psiCover to top bars = 2.5 inchesCover to bottom bars = 1.0 inchAnalyze a 1 foot wide section of slab

Find: Deck thickness, deck reinforcement

1. Determine Deck Thickness

Seff = 12.25′ – 2 (18″) / (4) (12) = 11.50′

Minimum thickness, tmin = (Seff + 10) (12) / 30 = (11.50 + 10) (12) / 30 = 8.60″

Use 83/4″ thick slab

2. Determine Transverse Deck Reinforcement — Top Slab Reinforcement

Dead Load Moment, MDL:

MDL = (1/10) [ (8.75″ / 12) (0.160 kcf) ] (11.50)2 = 1.55 kip-ft/ft

Live Load Moment + Impact, MLL+I :

MLL+I = (Pwheel) (0.8) (1.30) AASHTO, 1989, Section 3.24.3.1

where: Pwheel = 1.25 (16 kips/wheel) = 20.0 kips/wheel (HS25 Truck)

continuity factory = 0.8 AASHTO, 1989, Section 3.24.3.1impact factor = 1.30

MLL+I = (20.0) (0.8) (1.30) = 8.78 kip-ft/ft

Factored Design Moment, Mu:

Mu = 1.3 [ 1.55 + (5/3) (8.78) ] = 21.04 kip-ft/ft

Determine As req’d: dtop bars = 8.75 – 2.5 – (0.75) / 2 = 5.875″

Mu / (φ) (b) (d)2 = 21.04 (12,000) / (0.9) (12) (5.875)2 = 677.3 psi

Interpolating from Table 5.2-A2, Appendix A:ρ = 0.01272

As req’d = ρ (b) (d) = 0.01272 (12) (5.875) = 0.90 in2/ft

Use #6 bars at 5″ ctrs, As = 1.06 in2/ft > 0.90 in2/ft ok

Use same bar size and spacing for bottom slab reinforcement. An alternate approach is to solve directly forAs req’d from Eq (5), BDM Section 5.2.1B:

As req’d = 0.85 (fc′ / fy) (b) [ d – d2 – (31.3725 Mu / fc′ b) ] (5)

= [ 0.85 (4) (12) / 60 ] [ 5.875 – (5.785)2 – 31.3725 (21.04) / (4) (12) ]

As req’d = 0.90 in2/ft Agrees with value previously computed by tables.

(S + 2) 32

(11.50 + 2) 32

√

√

5.2-B1-2 July 2000

Check As min using Table 5.2-A2, Appendix A:

Mu = 1.2 Mcr = 1.2 fr S = (1.2) 7.5 fc′ (1/6) (b) (t)2

= (1.2) 7.5 4,000 (1/6) (12) (8.75)2 87,160 in-lbs/ft

Mu / φ bd2 = 87,160 / [ 0.9 (12) (5.875)2 ] = 233.8 psi

From Table 5.2-A2, Appendix A, interpolate ρ = 0.00404

As min = ρ (b) (d) = 0.00404 (12) (5.875) = 0.28 in2/ft < 1.06 in2/ft

Check As min using Eq (6):

As min = (d – d2 – ) (6)

As min = (5.875 – (5.875)2 – )As min = 0.285 in2/ft Agrees with value from tables.

Check As max: From Table 5.2-A2, Appendix A, ρmax = 0.75 ρb = 0.0214

As max = 0.0214 (12) (5.875) = 1.51 in2/ft

Check As max using Eq (7), BDM Section 5.2.1B:

As max = 0.6375 β1 (b) (d) (7)

As max = 0.6375 (0.85) (12) (5.875) = 1.51 in2/ft ok

3. Check Crack Control Requirements

Calculate fs due to Service Load:

M service load= 1.55 + 8.78 = 10.33 kip-ft/ft

fs calc = M(12,000) / Asjd

Where j = l – k/3 = 0.884 Agrees with Table 1, page 81, ACI Publication SP-3 ReinforcedConcrete Design Handbook Working Stress Design, 1965

k = 1 / 1 [ 1 + fs/nfc] = 1 / [ 1 + 24,000 / (8) (1,600) ] = 0.348fs = 24,000 psi Grade 60 bars per AASHTO, Section 8.15.2.2fc = 0.40 fc′ = 1,600 psi for Conc Cl 4000n = Es / Ec = 29,000,000 / 3,620,000 = 8.0

fs calc = 10.33 (12,000) / (1.06) (0.884) (5.875) = 22,517 psi

Using Eq (21), BDM Section 5.2.1G, Calculate allowable fs:

fs allowable = z / [ (dc) (A) ]1/3 Eq (21)

= 130 / [ (2.875) (5) (5.75) ]1/3 = 29.63 ksi > 22.52 ksi ok



√√

0.85 fc′ (b) fy √0.85 (4) (12) (60)

0.124 h2

√ fc′

0.124 (8.75)2

√ 4√

fc′ 87fy 87 + fy( )

(4) 87(60) 87 + 60( )

July 2000 5.2-B1-3



Alternate Approach, Check zcalc < 130 kips/in using Eq (22):

zcalc = fs calc [ (dc) (A) ]1/3 < 130 kips/in Eq (22)

= (22.52) [ (2.875) (5) (5.75) ]1/3 = 98.1 kips/in < 130 kips/in ok

Use #6 bars at 5″ ctrs top and bottom transverse slab reinforcement.

Deck Reinforcement — Mid-Span Steel Plate Girder

July 2000 5.2-B2-1


Reinforced Concrete Superstructures Slab Design for Prestressed Girders

Example 5.2-B2

Given: Center-to-center spacing of W58G girders = 8 feet 0 inchesWidth of top flange = 25 inches wideAverage flange thickness = 6 inchesGirder concrete strength fc′ = 7,000 psiDeck concrete, Class 5000 fc′ = 5,000 psiCover to top bars = 2.5 inchesCover to bottom bars = 1.0 inch

Find: Deck thickness, deck reinforcement

1. Determine Deck Thickness

Minimum slab thickness = 7.5″ no overlay, per BDM, Chapter 6. This thickness permits the use of#6 transverse and #5 longitudinal bars.

Seff = clear span per AASHTO 3.24.1.2(a)

Width of top flange/average flange thick = 4.16

Close enough to 4.0, use clear span for Seff

Seff = Sg – W2 = 8.0′ – 2.083′ = 5.92′

Check Minimum Slab Thickness, tmin:

tmin = (Seff + 10) (12) / 30 = (5.92′ + 10) (12) / 30 = 6.37″ < 7.5″ ok

2. Determine Transverse Deck Reinforcement — Top Slab Reinforcement

Dead Load Moment, MDL:

MDL = (1/10) [ (7.5″ / 12) (0.160 kcf) ] (5.92)2 = 0.43 kip-ft/ft

Live Load Moment + Impact, MLL+I :

MLL+I = (Pwheel) (0.8) (1.30) = (20.0) (0.8) (1.30)

MLL+I = 5.15 kip-ft/ft

Factored Design Moment, Mu:

Mu = 1.3 [ 0.35 + (5/3) (5.15) ] = 11.61 kip-ft/ft

Determine As req’d: dtop bars = 7.5 – 2.5 – (0.75) / 2 = 4.625″

Mu / (φ) (b) (d)2 = 12.54 (12,000) / (0.9) (12) (4.625)2 = 651.4 psi


As req’d = ρ (b) (d) = 0.01089 (12) (4.625) = 0.61 in2/ft

Use #6 bars at 8″ ctrs, As = 0.66 in2/ft ok

Use same bar size and spacing for bottom slab reinforcement.

(S + 2) 32

(6.54 + 2) 32

5.2-B2-2 July 2000

3. Check Crack Control Requirements — Transverse Reinforcement

Calculate fs due to Service Load:

Mservice load= 0.35 + 5.15 = 5.50 kip-ft/ft

fs calc = M (12,000) / Asjd

where: j = l – k/3 = 1 – 0.375/3 = 0.875k = 1 / 1 [ 1 + fs/nfc ] = 1 / [ 1 + 24,000 / (7.2) (2,000) ] = 0.375fc = 0.40 fc′ = (0.40) (5,000) = 2,000 psi for Concrete Class 5000Ec = 57,000 5,000 = 4,030,500 psifs = 24,000 psi Grade 60 barsn = Es / Ec = 29,000,000 / 4,030,500 = 7.2

fs calc = 5.50 (12,000) / (0.66) (0.875) (4.625) = 24,710 psi top bar

Calculate fs allowable = z / (Adc)1/3:

A = (7.5″) (2.875″) (2) / 1 bar = 43.125 dc = 2.5 + 0.75 / 2 = 2.875″

fs allow = 130 / [ (43.125) (2.875) ]1/3 = 26.07 ksi > 24.71 ksi ok

4. Determine Longitudinal Deck Reinforcement

Moments at Pier, Negative Reinforcement:

MDL = 187.6 kip-ft/girder MLL+I = 780.0 kip-ft/girder Service Load Moments

Mu = 1.3 [ 187.6 + (5/3) (780.0) ] = 1,933.8 kip-ft/girder

Determine As req’d assume two layers of #5 with davg = 64.0″:

Mu / (φ) (b) (d)2 = 1,933.8 (12,000) / (0.9) (25) (64)2 = 251.8 psi


As req’d = 0.00433 (25) (64.0) = 6.93 in2

Use 24-#5 (12-#5 in each layer) As = 7.44 in2 > 6.93 in2 ok

Spacing is approximately 8.0″, As/ft = 0.47 in2/ft

Check longitudinal distribution reinforcement so that spacing can be coordinated with the reinforcementrequired for negative pier girder moment:

P = 220 / S = 220 / 6.54 = 86.0 percent but not to exceed 67 percent

Distribution Reinforcement = 0.67 (As actual) = 0.67 (0.70) = 0.47 in2/ft

As provided = 0.47 in2/ft ok



√

√ √

July 2000 5.2-B2-3



√

5. Check Crack Control Requirement — Longitudinal Reinforcement

24-#5 As = 7.44 in2 n = Es/Ec = 29,000,000 / 4,769,000 = 6.0

k = 2 ρ n + (ρ n)2 – ρ n

k = 2 (0.0047) (6.0) + [ (0.0047) (6.0) ]2 – (0.0047) (6.0) = 0.210

j = l – k/3 = 0.93

fs calc = M (12,000) / Asjd = 967.6 (12,000) / (7.44) (0.93) (64.0) = 26,220 psi

fs allowable = z / [ (dc) (A) ]1/3

Use actual girder spacing = (8.0′) (12) = 96.0″ to compute A

A = (96) (7.5) / 24 bars = 30.0 in2/bar dc = 2.5 + 0.75 + 0.625/2 = 3.56″

√

fs allowable = 130 / [ 30.0 (3.56) ]1/3 = 27.40 psi > 26.22 psi ok

Deck Reinforcement at Intermediate Pier — Prestressed Girder Bridge

Longitutdinal Deck Reinforcement is designed for the negative moment at an intermediate pier. Otherwise, thelongitudinal deck reinforcement will be similar to that shown in Example 5.2-B1-1.

July 2000 5.2-B3-1


Reinforced Concrete Superstructures Strut-and-Tie Design

Design Loads

Group I: Pu = 1600k H = 0Group VII: Pu = 1500k H = 400k

Assume crossbeam dead load is included with bearing loads.Use Section 12.4 of AASHTO’s Guide Specifications for Design and Construction of Segmental Concrete Bridges,1989.

Example 5.2-B3

5.2-B3-2 July 2000



Develop a Preliminary Strut-and-Tie Model:

Estimate node size at top of column:

φb (fcn Acn) ≥ Su

Assuming spiral reinforcement provides confinement, use φb = 0.75 and fcn = 0.85 fc′:

0.75 (0.85× 5) Acn ≥ 2,400

Acn ≥ 753 in2

Use the following node size at the top of column:

July 2000 5.2-B3-3



Determine Truss Element Forces:

Group I Strut Loads Group VII Strut Loads

Determine Minimum Size of Node Regions:

φb (fcn Acn) ≥ Su where: φb = 0.70 for bearing

fcn = 0.85 fc′ in regions with compression only

fcn = 0.70 fc′ in regions with one tension tie

At base of inclined strut,

0.75 (0.85× 5) Acn ≥ 2,596

Acn ≥ 873 in2

depth of node = = 12.1″ (72″ × 12.1″)

where width of crossbeam =72″

At top of inclined strut, Acn ≥ = 1,060 in2

depth of node = = 14.7″ (72″ × 14.7″)

For 1,600k chord: Acn ≥ = 538 in2

depth of node = = 7.5″

For 915k chord: Acn ≥ (538) = 308 in2

depth of node = = 4.3″

87372″

2,5960.70 (0.70× 5)

1,060 72″

1,6000.70 (0.85× 5)

53872″

30872″

9151,600

5.2-B3-4 July 2000

Determine Minimum Sizes of Compression Members:

φv (fcu Acs) ≥ Su (inclined compressive struts)

φf (0.85 fc′ Acc + As′ fs′) ≥ Su (compression chords)

For 2,596k inclined compressive strut:

0.85 (0.45× 5) Acs ≥ 2,596k (fcu = 0.45 fc′)

Acs ≥ = 1,357 in2

and depth of strut = = 18.9 in

For 915k inclined compressive strut:

Acs ≥ (1,357) = 478 in2

and depth of strut = = 6.6 in

For 1,600k compression chord:

Acs ≥ = 418 in2

and depth of chord = = 5.8 in

Incorporate Node and Member Sizes Into Model:



2,5960.85 (0.45) (5)

1,357 72

9152,596

478 72

1,6000.9 (0.85) (5)

418 72

July 2000 5.2-B3-5



Recalculate Truss Member Forces:

Group I Strut Loads Group VII Strut Loads

Design Tie Member:

φf (As fsy + A*s f*su) ≥ Su

without prestress: 0.90 (As) (60) ≥ 2,240

As ≥ 41.5 in2

Try using 12 bundles of #14 top and #11 bot (As = 45.7 in2)

Check development length of tie bars:

For #14 bars with fc′ = 5,000 psi, ldh = 2′ – 5″

Development length available = 2′ – 4″ < 2′ – 5″

For #11 bars, ldh = 1′ – 5″ ok

Therefore, total developed steel As = 12 (1.56) + 12 (2.25)

As = 44.8 in2 > 41.5 in2 ok

Partial Elevation-Tension Tie at Top of Pier Cap

x = = 4.37″ = 4″ estimate ok12 (2.25) (3.26) + 12 (1.56) (5.97) 45.7

28 29( )

5.2-B3-6 July 2000



Determine Minimum Vertical and Horizontal Steel Using Sections 12.5.3.2 and 12.5.3.3:

For vertical reinforcing: As fy ≥ 120 bw s

where s < or 12″

Therefore, As ≥ = 0.002 bw s

Assume 4 legs of #6 stirrups: As = 1.76 in2

s ≤ =

s ≤ 12.2 in

Check: = = 16.9″

Therefore, use 4 #6 legs at 12″ maximum spacing.

For horizontal reinforcing: As fy ≥ 120 bw s

where s < or 12″

For s = 12″, As ≥ 0.002 (72) (12) = 1.73 in2 (2 – #9 bars)

Try 2 #8 bars: As = 1.58 in2

s ≤ = 11.0″

Use #8 bars at 11″ maximum spacing on side faces.

For bottom bars, use #6 at approximately 12″ (7 – #6 bars)

120 bw s 60,000

d4

As0.002 bw

1.760.002 (72)

d4

72 – 4.37 4

d3

1.580.002 (72)

July 2000 5.2-B4-1


Reinforced Concrete Superstructures Working Stress Design

Example 5.2-B4

Service Load — Concrete Stresses and Constants

5.2-B4-2 July 2000



July 2000 5.2-B4-3




Prestressed Concrete Superstructures Contents

July 2000 6.0-i

Page

6.0 Prestressed Concrete Superstructures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.1-1

6.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

6.1.1 Criteria . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1A. General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1B. Allowable Stresses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

6.1.2 Concrete Properties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1A. Strength of Concrete . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1B. Modulus of Elasticity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2C. Creep Rate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2D. Shrinkage Rate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

6.1.3 Prestressing Steel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3A. General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3B. Allowable Stresses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

6.1.4 Prestressing Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3A. General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3B. Anchorages . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

6.1.5 Losses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3A. Instantaneous Losses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4B. Time-dependent Losses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

6.1.6 Construction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5A. General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5B. Contract Plans . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5C. Shop Plans . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

6.1.7 Connections (Joints) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

6.1.8 Deflection and Camber . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

6.2 Precast Sections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.2-1

6.2.1 Pre-Tensioning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

6.2.2 Post-Tensioning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

6.2.3 Washington Standard Prestressed Girder Sections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1A. Properties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1B. Section Geometry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1C. Basic Assumptions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3D. Design Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4E. Prestressing Strands . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7F. Development of Prestressing Strand . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8G. Fabrication and Handling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

6.2.4 Precast Prestressed (Short Span Bridges) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14A. Precast Prestressed Slabs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14B. Precast Prestressed Tri-Beam . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14C. Precast Prestressed Deck Bulb-Tee Girders . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

6.2.5 Precast Box Girders . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

6.3 Precast Girder Bridges . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.3-1

6.3.1 Criteria for Girder Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1A. Support Conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1B. Composite Action . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1C. Prestressed Girder Camber . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7



6.0-ii July 2000

Page

6.3.2 Framing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10A. Girder Selection and Spacing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10B. Slab Cantilevers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11C. Diaphragm Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12D. Skew Effects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13E. Grade and Cross Slope Effects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13F. Curve Effect and Flare Effect . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

6.3.3 Reinforcement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13A. Simple Spans . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13B. Continuous Spans . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

6.3.4 Roadway Slab . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18A. Slab Thickness . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18B. Transverse Reinforcement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

6.3.5 Crossbeam Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21A. General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21B. Loads . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21C. Geometry and Construction Requirement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21D. Skin Reinforcement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

6.3.6 Repair of Damaged Bridge Girders . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22A. General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22B. Repair Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22C. Miscellaneous References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

6.4 Cast-in-Place Bridges . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.4-1

6.4.1 Design Parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1A. General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1B. Bridge Types . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1C. Section Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2D. Strand and Tendon Arrangements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3E. Layout of Anchorages and End Blocks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3F. Superstructure Shortening . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

6.4.2 Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10A. Section Properties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11B. Preliminary Stress Check . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11C. Tendon Layout . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12D. Prestress Losses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13E. Steel Stress Curve . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13F. Prestress Moment Curves . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15G. Flexural Stress in Concrete . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16H. Temperature Effects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17I. Shear . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18J. End Block Stresses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19K. Anchorage Stresses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20L. Camber . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20M. Expansion Bearing Offsets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20N. Post-Tensioning Notes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

6.4.3 Review of Shop Plans . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

6.99 Bibliography . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.99-1



July 2000 6.0-iii


6.1-A1 “A” Dimension for P.S. Concrete Bridges6.2-A1 W95G and W83G

6.3-A1 Prestressed Girder Intermediate Hinge Diaphragm

6.4-A1-1 WSDOT Standard Girder — Composite Sections6.4-A1-2 WSDOT Standard Girder — Non-Composite Sections

6.4-A2 WSDOT Standard Girders Section Properties — Composite Sections

6.4-A3-1 WSDOT Standard Girders Section Properties — Non-Composite Sections 1 of 26.4-A3-2 WSDOT Standard Girders Section Properties — Non-Composite Sections 2 of 2

6.4-A4 WSDOT Standard Girders Span Range Capacity

6.5-A1-1 W42G Girder Details 1 of 26.5-A1-2 W42G Girder Details 2 of 2

6.5-A2-1 W50G Girder Details 1 of 2




6.5-A5-1 WF74G Girder Details 1 of 3

6.5-A5-2 WF74G Girder Details 2 of 36.5-A5-3 WF74G Girder Details 3 of 3





6.5-A8 End Wall on P.S. Concrete Girder — Diaphragm Details

6.5-A9 Abutment Type Pier — Diaphragm Details6.5-A10-1 Intermediate Pier — Fixed Recessed-Face Diaphragm Details

6.5-A10-2 Intermediate Pier — Fixed Flush-Face Diaphragm Details

6.5-A10-3 Intermediate Pier — Hinge Diaphragm Details6.5-A10-4 Intermediate Pier — End Wall on Girder Details

6.5-A11 Intermediate Diaphragm Details

6.5-A12 Miscellaneous Diaphragm Details6.5-A13 Single Span Prestressed Girder Construction Sequence

6.5-A14 Multiple Span Prestressed Girder Construction Sequence

6.6-A1-1 Precast Prestressed 1′-0″ Solid Slab Details 1 of 26.6-A1-2 Precast Prestressed 1′-0″ Solid Slab Details 2 of 2

6.6-A2-1 Precast Prestressed 1′-6″ Voided Slab Details 1 of 2

6.6-A2-2 Precast Prestressed 1′-6″ Voided Slab Details 2 of 26.6-A3-1 Precast Prestressed 2′-2″ Voided Slab Details 1 of 2

6.6-A3-2 Precast Prestressed 2′-2″ Voided Slab Details 2 of 2



6.0-iv July 2000

6.6-A4 Precast Prestressed Slab End Pier Details

6.6-A5 Precast Prestressed Slab Intermediate Pier Details6.6-A6 Precast Prestressed Slab Layout

6.7-A1-1 Precast Prestressed Ribbed Tri-Beam Girder Details 1 of 2

6.7-A1-2 Precast Prestressed Ribbed Tri-Beam Girder Details 2 of 26.7-A3 Precast Prestressed Ribbed Tri-Beam Girder Pier Details

6.8-A1-1 W35DG Deck Bulb Tee Girder Details 1 of 2

6.8-A1-2 W35DG Deck Bulb Tee Girder Details 2 of 26.8-A1-3 W35DG Deck Bulb Tee Girder Design Tables

6.8-A1-4 W35DG Deck Bulb Tee Diaphragm Details

6.8-A2-1 W41DG Deck Bulb Tee Girder Details 1 of 26.8-A2-2 W41DG Deck Bulb Tee Girder Details 2 of 2

6.8-A2-3 W41DG Deck Bulb Tee Girder Design Tables

6.8-A2-4 W41DG Deck Bulb Tee Diaphragm Details6.8-A3-1 W53DG Deck Bulb Tee Girder Details 1 of 2


6.8-A3-3 W53DG Deck Bulb Tee Girder Design Tables6.8-A3-4 W53DG Deck Bulb Tee Diaphragm Details


6.8-A4-2 W65DG Deck Bulb Tee Girder Details 2 of 26.8-A4-3 W65DG Deck Bulb Tee Girder Design Tables

6.8-A4-4 W65DG Deck Bulb Tee Diaphragm Details

6.8-A5 Deck Bulb Tee Diaphragm Details


6.1-B1 Post-Tensioning Anchorages6.2-B1 Notes to Designers Post-Tensioning

6.3-B1 P.T. Box Girder Bridges Single Span

6.3-B2 P.T. Box Girder Bridges Two Span6.3-B3 P.T. Box Girder Bridges Multiple Span

P65:DP/BDM6


Prestressed Concrete Superstructures General

July 2000 6.1-1

6.0 Prestressed Concrete Superstructures

6.1 General

WSDOT uses three types of prestressed concrete bridges. They are (1) prestressed precast concrete girderor slab bridges, (2) cast-in-place post-tensioned bridges, and (3) combination prestressed/post-tensionedbridges. WSDOT utilizes prestressed concrete in special structures such as segmental cast-in-place orprecast construction. This section provides criteria for these structure types and provides general guidancefor other designs using prestressed concrete.

6.1.1 Criteria

A. General

AASHTO specifications shall be used to design prestressed concrete bridges, except as modifiedin this section. Prestressed concrete bridges shall be designed using working stress design andchecked for ultimate load capacity. Refer to portions of Chapter 5 for information relating toconcrete reinforcement and design methods used for prestressed structures.

B. Allowable Stresses

AASHTO standard specifications list the allowable stresses to be used in design except as notedbelow.

1. Concrete Stresses at Service Load

Under working stress conditions, tensile stresses in the precompressed tensile zone shall belimited to zero. This prevents cracking of the concrete during service life of the structure andprovides more allowance for overloads during the life of the bridge.

2. Shear Capacity

Shear in webs of prestressed bridges shall be in accordance with AASHTO specifications.Where additional guidance is needed, the latest ACI Code should be consulted. For specialconsiderations used for design of Washington State standard prestressed girders, seeSubsection 6.3.

6.1.2 Concrete Properties

A. Strength of Concrete

Pacific NW aggregates have consistently resulted in excellent concrete strengths, to as much as10,000 psi in 28 days. The following strengths are normally used for design.

1. Precast Girders

Nominal 28-day concrete strength (fc′) for precast girders with a cast-in-place deck is 7,000 psi.Where higher strengths would eliminate a line of girders, this strength can be specified, prefer-ably at 8,500 psi, to a maximum of 10,000 psi. The final strength of concrete shall be specified asrequired by design and shall be shown on the plans.

The minimum concrete compressive strength at release (fci′) for each prestressed girder in abridge is to be calculated and shown in the plans. For a 28-day concrete compressive strengthof 7,000 psi, a concrete compressive strength (at release) of between 3,500 and 6,000 psi shallbe specified. For high strength concrete, the compressive strength at release shall be limited to



6.1-2 July 2000

7,500 psi. Release strengths of up to 8,500 psi can be achieved with extended curing for specialcircumstances. The specified concrete strength at release should be rounded to the next highest100 psi.

2. Cast-in-Place Post-tensioned Bridges

Since conditions for placing and curing concrete on cast-in-place bridges are not controlled,as they are for precast bridge sections, a lower figure is used for concrete strength. Normally,use class 4000 concrete for post-tensioned cast-in-place bridges. Where significant economycan be gained and structural requirements dictate, the structure could be designed for class5000 concrete.

3. Cast-in-Place Slabs

Concrete class 4000D shall be used for all cast-in-place bridge decks unless otherwise approvedby the Bridge Design Engineer.

B. Modulus of Elasticity

The modulus of elasticity for concrete strength up to 10 ksi is normally 33w3/2 fc′, where w is theweight of concrete in lbs/ft3. Normal weight concretes used in Washington generally have weightsclose to 160 lbs/ft3. With this value, the modules of elasticity equation simplifies to E = 66,800 .

C. Creep Rate

The creep coefficient for standard conditions may be taken as follows:

Standard conditions are relative humidity ≤40 percent and average thickness of section 6 inches.

1. Cast-in-Place Girders

For most designs, the creep coefficient for loading at 7 days for moist-cured concrete and 1-3days for steam-cured concrete is:

Ct =

The final deflection is a combination of the elastic deflection and the creep effect associated withgiven loads shown by the equation below.

∆ total = ∆ elastic (1+ Ct)

For other factors affecting this equation, see Reference 6.99.2 and 6.99.4. Reference to 6.99.4discusses methods for calculating creep effects.

2. Standard Prestressed Girders

The creep coefficient for standard prestressed girders may be taken as:

Ct =

Ct = creep coefficient

t = time in days

fc′ = ultimate strength of concrete in ksi

√

√fc′

22 . t0.6

6 + fc′ 10 + t0.6

3.95 . 6 + fc′

Ln (t + 1)



July 2000 6.1-3

D. Shrinkage Rate

To compute the variation of shrinkage with time, use the following equations:

For moist cured concrete after 7 days:

For steam cured concrete after 1 to 3 days:

Where (∑SH)t is the shrinkage strain at any point in time.

For corrections to the shrinkage rate values including correction for initial shrinkage, seeReference 6.99.4.

6.1.3 Prestressing Steel

A. General

Three types of high-tensile steel are used for producing prestress. They are:

1. Strands: ASTM A 416 Grade 270, low relaxation or stress relieved.

2. Bars: ASTM A 722 Grade 150, Type 2.

3. Parallel wires: ASTM A 421 Grade 240.

All WSDOT designs are based on low relaxation strands using either 1/2″ or 0.6″ diameter strands.

B. Allowable Stresses

Allowable stresses for design are as listed in AASHTO specifications.

6.1.4 Prestressing Systems

A. General

There are numerous prestressing systems. Most systems combine a method of stressing theprestressing strands with a method of anchoring it to concrete.

B. Anchorages

WSDOT requires approval of all multi-strand and/or bar anchorages used in prestressed concretebridges by testing or by a certified report, stating that the anchorage assembly will develop the yieldstrength of post-tensioning steel. Manufacturers whose anchorages have been approved are.

1. V.S.L. Corporation

2. Avar Construction System

3. Dywidag Systems International

6.1.5 Losses

AASHTO specifications outline the method of predicting prestress losses for usual prestressed concretebridges which may be used in design except as noted below.

The following sources of prestress loss can influence the effective stress in the strand.

(∑SH)t = x 0.51 x 10-3t35 + t

(∑SH)t = x 0.56 x 10-3t55 + t



6.1-4 July 2000

A. Instantaneous Losses

1. Anchorage slippage. This slippage is assumed to be 1/4 inch for design purposes.

2. Friction losses. These losses are due to intended cable curvature and unintended wobblecoefficient. For strands against rigid galvanized metal duct these values are respectively µ = 0.20and k = 0.0002. For strands against smooth polyethylene duct µ = 0.16 and k = 0.0002.

3. Elastic shortening of concrete.

B. Time-dependent Losses

1. Creep of concrete.

2. Shrinkage of concrete.

3. Steel relaxation.

For normal design in lieu of more accurate methods, time dependent losses may be taken as given inTable 6.1.5-1.

Type of Section Low-relaxation Strands Bars

Rectangular Beam 33 ksi 25 ksi

Box Girder 21 ksi 15 ksi

I-Girder 33 [1- 0.15 (fc′ - 6) / 6 ] 19 ksi

Single/Double T, HollowCore Voided Slab 37 [ 1- 0.15 (fc′ - 6) / 6 ] 29 [ 1- 0.15 (fc′ - 6) / 6 ]

Time Dependent Prestress LossesTable 6.1.5-1

Prestress losses due to instantaneous sources shall be added to the time dependent losses to determinethe total losses. The loss due to elastic shortening in pretensioned members shall be taken as:

PLES = (Ep / Eci ) fcgp

The loss due to elastic shortening in post-tensioned members shall be taken as:

PLES = [(N-1)/2N x Ep / Eci ] fcgp

where: Ep = modulus of elasticity of prestressing steel, ksi

Eci = modulus of elasticity of concrete at transfer, ksi

N = number of identical prestressing tendons

fcgp = sum of concrete stresses at the center of gravity of prestressing tendons due to theprestressing force at transfer (after jacking for posttensioned members) and theself-weight of the member at the section of maximum moment, ksi

For pretensioned member and low-relaxation strands, fcgp may be calculated on the basis of 0.7fpu.For post-tensioned members with bonded tendons, fcgp may be calculated on the basis of prestressingforce after jacking at the section of maximum moment.

For preliminary design of pretensioned prestressed girders with normal strength concrete limited to7,000 psi, the total prestress loss may be taken as 48 ksi.



July 2000 6.1-5

6.1.6 Construction

A. General

Construction plans for conventional post-tensioned box girder bridges include two different sets ofdrawings. The first set (contract) is prepared by the design engineer (WSDOT or contracting agency)and the second set (shop) is prepared by the post-tensioning materials supplier (contractor).

B. Contract Plans

The plans should be prepared to accommodate any post-tensioning system, so only prestressing forcesand eccentricity should be detailed. The concrete sections should be detailed so that available systemscan be installed. Design the thickness of webs and flanges to facilitate concrete placement. Generally,web thickness for post-tensioned bridges shall be at least 12 inches.

C. Shop Plans

The shop plans are used to detail, install, and stress the post-tensioning system selected by theContractor. These plans must contain sufficient information to allow the engineer to check theircompliance with the contract plans. These plans must also contain the location of anchorages,stressing data, and arrangement of tendons.

6.1.7 Connections (Joints)

The connections or joints must divide the structure into a logical pattern of separate elements which alsopermit ease of manufacture and assembly.

The connection or joint surfaces should be oriented perpendicular to the centroidal axis of the precastelement.

Types of Connections (Joints):

Connections or joints are either wide or match cast. Depending on their width, they may be filledwith cast-in-place concrete or grouted. Match cast joints are normally bonded with an epoxy bondingagent. Dry match cast joints are not recommended.

Shear and Alignment Keys:

In order to assist shear transmission in wide joints, use a suitable system of keys. The shape of thekeys may be chosen to suit a particular application and they can be either single keys or multiplekeys. Single keys are generally large and localized whereas multiple keys generally cover as muchof the joint surface area as is practical.

Single Key Multiple Keys



6.1-6 July 2000

Single keys provide an excellent guide for erection of elements. Single keys are preferred for allmatch cast joints.

For all types of joints, the surfaces must be clean, free from grease and oil, etc. When using epoxy forbonding, the joints should be lightly sand-blasted to remove laitance. For cast-in-place or other typesof wide joints, the adjacent concrete surfaces should be roughened and kept thoroughly wet, prior toconstruction of the joint. Cast-in-place joints are generally preferred.

6.1.8 Deflection and Camber

Deflections of prestressed concrete beams can be predicted with greater accuracy than those for reinforcedconcrete beams. Since prestressed concrete is more or less homogeneous and obeys ordinary laws offlexure and shear, the deflection can be computed using elementary methods. However, accurate predic-tions of the deflections are difficult to determine, since modulus of elasticity of concrete, Ec, varies withstress and age of concrete. Also, the effects of creep on deflections are difficult to estimate. For practicalpurposes, an accuracy of 10 to 20 percent is often sufficient. Prestressing can be used advantageously tocontrol deflections, however, there are cases where excessive camber due to prestress have causedproblems. For normal design, in lieu of more accurate methods, the deflection and camber of prestressedmembers may be estimated by the multipliers as given in Table 6.1.8-1.

Multipliers for Estimating Long-term Deflection of Prestressed Concrete GirdersTable 6.1.8-1

Normal Strength High StrengthConcrete fc′ <= 7.0 ksi Concrete fc′ > 7.0 ksi

Non- Non-Composite Composite Composite Composite

Deflection at ErectionApply to the elastic deflection due to the member weight 1.85 1.85 1.75 1.75at release of prestress

Apply to the elastic deflection due to prestressing at 1.80 1.80 1.70 1.70release of prestress

Deflection at FinalApply to the elastic deflection due to the member weight 2.70 2.40 2.50 2.20at release of prestress

Apply to the elastic deflection due to prestressing at 2.45 2.20 2.25 2.10release of prestress

Apply to the elastic deflection due to the Super Imposed 3.00 3.00 2.75 2.75Dead Loads

Apply to the elastic deflection due to weight of slab ---- 2.30 ---- 2.15release of prestress

P65:DP/BDM6


Prestressed Concrete Superstructures Precast Sections

July 2000 6.2-1

6.2 Precast Sections

Precast sections are generally cast in a permanent plant or somewhere near the construction site and thenerected. Precasting permits better material quality control and is often more economical than cast-in-placeconcrete. The precast ‘U’ sections are commonly called ‘bathtubs’ which can be joined together with“wet joint.”

6.2.1 Pre-Tensioning

Pre-tensioning is accomplished by stressing high strength steel strands to a predetermined tension andthen placing concrete around the strands, while the stress is maintained. After the concrete has hardened,the strands are released and the concrete, which has become bonded to the tendon, is prestressed as aresult of the strands attempting to relax to their original length. The strand stress is maintained duringplacing and curing of the concrete by anchoring the ends of strands to abutments that may be as much as500 feet apart. The abutments and appurtenances used in this procedure are referred to as pre-tensioningbed or bench.

6.2.2 Post-Tensioning

Post-tensioning consists of installing steel tendons into a hollow metalic duct in a structure after theconcrete sections are cast. These tendons are usually anchored at each end of the structure and stressed toa design strength using a hydraulic jacking system. Commonly the tendons are encased in a tight metaltube. This tube is referred to as a sheath or duct and remains in the structure. After the tendon has beenstressed, the duct is filled with grout which bonds the tendon to the concrete section and prevents corro-sion of the strand. Finally, closure pours are made at the anchor heads to provide corrosion protection.

6.2.3 Washington Standard Prestressed Girder Sections

Washington State Standard girders were adopted in the mid-1950s. These girder shapes proved to be veryefficient due to their thin webs and small flange fillets. These are still the most efficient shapes availableand variations of these girders have been adopted by other states. The original series was graduated in10-foot increments from 30 feet to 100 feet.

In 1990, revisions were made to the prestressed concrete girder standards incorporating the results of theresearch done at Washington State University on girders without end blocks. The new standards incorpo-rate three major changes. They have a thicker web, the end blocks are eliminated, and have increaseddistance between strands. The new standard designations are W74G, W58G, W50G, W42G, and deckbulb tee standards W53DG and W35DG. The numbers refer to the depth of the section.

In 1999, deeper girders, commonly called “Supergirders” were added to the WSDOT prestressed concretegirder standards. These new supergirders may be pretensioned or post-tensioned. The pretensionedstandards are designated as WF74G, W83G and W95G and the post-tensioned standards are designatedas W83PTG and W95PTG.

A. Properties

The properties which are needed for design of standard girders are listed in Appendix 6.4-A3-1 and 2.

B. Section Geometry

Table 6.2.3-1 gives the dimensions of the Washington State Standard Girder Sections.



6.2-2 July 2000

Dimensions of Standard Prestressed Girder SectionsTable 6.2.3-1



July 2000 6.2-3

C. Basic Assumptions

The following basic assumptions are used in the design of these standard girders. Figure 6.2.3-1illustrates some of the factors which are constant in the WSDOT Prestressed Girder Design computerprogram. Figure 6.2.3-2 show variations from those assumptions for a typical backwall design and atypical notched girder design.

Typical Prestressed Girder ConfigurationFigure 6.2.3-2

Figure 6.2.3-3 and Appendix 6.5-A1 through A7 show the standard strand positions in these girders.

Typical Prestressed Girder SpanFigure 6.2.3-1



6.2-4 July 2000

1. Prestress

For final conditions, the designer shall assume the prestress acting on the section to be NAs(.70 fs′-PL) for stress relieved strands and NAs (.75 fs′-PL) for low relaxation strands.

Where:

N = number of stressed strands passing through the section

As = the area of one strand, in2

fs′ = the ultimate strength in ksi

PL = indicates total prestress losses in ksi in pretensioned members.

For checking of stresses during release, lifting, transportation, and erection of prestressed girders,the elastic and time dependent losses shall be as follows:

Release — 1 day (lifting of girders from casting beds) computed losses1 month — 4 months (transportation and erection of girders) 35 ksiAfter 4 months computed losses

2. Strand Patterns

Standard strand patterns are shown in Appendix 6.5-A1 through A7.

D. Design Procedure

1. General

The WSDOT “Prestressed Girder Design” computer program uses a trial and error method toarrive at solution for stress requirement and is the preferred method for final design of lengthand spacing. Some publications suggest various direct means for determining stress and position,but the procedures are generally quite complex.

2. Stress Conditions

The stress limits as described in Table 6.2.3-2 must be met for the girder and its prestress. Oneor more of the conditions described below may govern design. Each condition is the result ofthe summation of stresses with each load acting on its appropriate section (such as girder only,composite section). Precast girders shall also be checked during lifting, transportation, anderection stages by the designer to assure that girder delivery is feasible. Impact during the liftingstage shall be 0 percent and during transportation shall be 20 percent of the dead load of thegirder. Impact shall be applied either upward or downward to produce maximum stresses.



July 2000 6.2-5

Prestressed Girder Strand LocationsFigure 6.2.3-3

Note: Fo may be increased in 1-inch increments to keep slope of harped strands below the slope limit.

Fb may be increased in 1-inch increments in order to reduce tension at the top of the girder at

harping point at time of strand release.



6.2-6 July 2000

Condition Stress Location Allowable Stress

Temporary Stress Tensile In areas other than <=0.2 psiat Transfer Precompressed

Tensile Zone

PrecompressedTensile Zone

Compression All Locations 0.6 fci′

Temporary Stress Tensile In areas other thanat Lifting Precompressed

Tensile Zone


Compression All Locations 0.6 fci′

Tempoary Stress Tensile In areas other thanat Shipping Precompressed

Tensile Zone


Compression All Locations 0.6 fc′

Final Stresses at Tensile Precompressed 0.0 psiService Load Tensile Zone

Compression All Locations due to:

Permanent loads 0.45 fc′and effective

Prestressing Load

Live load, one-half 0.4 fc′permanent loads

and effectiveprestressing load

All load combinations 0.6 fc′

Allowable Concrete StressesTable 6.2.3-2

√6 fci′

√3 fci′

√6 fci′

√6 fci′

√6 fci′

√6 fci′



July 2000 6.2-7

E. Prestressing Strands

1. Straight Strands

The position of the straight strands in the bottom flange and temporary strands for shipping andhandling in top flange has been standardized for each size of flange. Those strand positions andthe girder flange size are summarized in Appendix 6.5-A1 through A7.

2. Harped Strands

The harped strands are bundled at the 4/10 points of the span for series W83G, W95G, WF74Gand W58G and at the 1/3 points at the girders for series W50G and W42G. The harped strandsare bundled at the harping points. Bundles are limited to 12 strands each. Twelve (12) and fewerharped strands are placed in a single bundle with the centroid normally 3 inches above the bottomof the girder. Strands in excess of 12 are bundled in a second bundle with the centroid 6 inchesabove the bottom of the girder. At the girder ends, the strands are splayed to a normal pattern.The centroid of strands at both the girder end and the harping point may be varied to suit girderstress requirements.

3. Stirrups

Shear for computation of stirrup requirements is computed at a point 1/2 of the girder depth fromthe end of the girder and at the harping point. Ultimate shear is computed at these points based on1.3 DL + 2.17 (L.L. + Impact). The portion of this shear which is carried by the concrete is givenin section 9.20.2 of AASHTO. The stirrup spacing is then calculated using the formula:

S = where Vs = Vu / 0.85 – Vc and

d is the distance from the extreme compressive fiber to the centroid of the prestressing force.For precast girders made continuous for live load, d shall be the distance from the extremecompressive fiber to the centroid of the negative moment reinforcement, i.e., d = h + A - 4.5",where h = height of the girder; A as defined in Subsection 6.3.4 A(3).

Shear reinforcement are furnished by two vertical bars. Maximum spacing is taken to be 1 foot6 inches The point where 1-foot 6-inch spacing starts is found by interpolating between the point1/2 of the girder depth from the end of the girder and the harping point to find the location wherethe portion of the shear carried by the stirrups (Vs) yields 1 foot 6 inches Vs for 1-foot 6-inch

stirrup spacing can be found by using Vs (18) = where dmin is the smallest of the

d values found for the point 1/2 of the girder depth from the end of the girder and the harping

point. The 1-foot 6-inch stirrup spacing is used throughout the rest of the girder.

If the stirrup spacing at the point 1/2 of the girder depth from the end of the girder is smaller thanabout 1 foot 2 inches, further interpolation may be done to obtain a multiple step increment ofstirrup spacing.

4. End Section Reinforcement

The Washington State Standard Prestressed Concrete Girders are not provided with a thickenedend block section, but have constant thickness webs. The end section reinforcement is detailedon the Office Standard Plans. This reinforcement is based on the requirement to resist burstingforces due to strand force development in this area. If the stirrup spacing required at the end of

Av • fy(d)

Vs

Avfy(dmin)

18



6.2-8 July 2000

the girder is less than shown on the Office Standard Plans, end section stirrups spacing on theStandard Plans should be altered to show this spacing. For a distance of 1.5d from the end of thegirder, reinforcement shall be placed to confine the p/s steel in bottom flange. The spacing ofconfinement reinforcement shall not exceed 6 inch and shall be shaped to enclose the strands.

F. Development of Prestressing Strand

1. General

In determining the resistance of pretensioned concrete components in their end zones, the gradualbuildup of the strand force in the transfer and development lengths shall be taken into account.

The prestress force may be assumed to vary linearly from 0.0 at the point where bondingcommences to a maximum at the transfer length.

Between the transfer length and the development length, the strand force may be assumedto increase in a parabolic manner, reaching the tensile strength of the strand at the end ofdevelopment length.

For the purpose of this article, the transfer length may be taken as 60 strand diameters and thedevelopment length shall be taken as specified in Article 6.2.3F2.

The effects of debonding shall be considered as specified in Article 6.2.3F3.

2. Bonded Strand

Pretensioning strand shall be bonded beyond the critical section for development length, ininches, taken as:

where:

D = nominal strand diameter (in)

fse = effective stress in prestressing steel after all losses (ksi)

fsu = in the prestressing steel at nominal strength (ksi)

3. Partially Debonded Strands

Where a portion or portions of a pretensioning strand are not bonded and where tension existsin the precompressed tensile zone, the development length specified in Article 6.2.3F2 shallbe doubled.

The number of partially debonded strands should not exceed 25 percent of the total numberof strands.

The number of debonded strands in any horizontal row shall not exceed 40 percent of the strandsin that row.

Debonded strands shall be symmetrically distributed about the centerline of the member.Debonded lengths of pairs of strands that are symmetrically positioned about the centerline ofthe member shall be equal.

Exterior strands in each horizontal row shall be fully bonded.

Ld′ ≥ fsu – fse D( * )23

*



July 2000 6.2-9

4. Unbonding Strands

Where it is necessary to prevent a strand from actively supplying prestress force near the endof a girder, it may be unbonded. This can be accomplished by taping a close fitting pvc tube tothe stressed strand from the end of the girder to some point where the strand can be allowed todevelop its load. Since this is not a common procedure, it should be carefully detailed on theplans. It is important when this method is used in construction that the taping of the tube bedone in such a manner that grout cannot leak into the tube and provide an undesirable bond ofthe strand.

5. Strand Development Outside of Girder

For girders made continuous for live load, extended bottom prestress strands are used to carrypositive live load, creep, and other moments from one span to another. Usually four strands pergirder will provide an adequate resistance. Strands used for this purpose must be developed in theshort distance between the two girder ends. This is normally accomplished by requiring strandchucks and anchors as shown in Figure 6.2.3-4. The nominal development length is normally2 feet. For wide crossbeams, the strands may be extended straight and a 1 foot 0 inch splice used.At back walls, which are connected to the superstructure, the extended strands may be used towithstand earthquake forces and, in this case, should be developed accordingly. The numberof strands to be extended cannot exceed the number of straight strands available in the girder.

Designer shall calculate the exact number of extended straight strands needed to develop therequired moment capacity at the end of girder. This calculation shall be based on the tensilestrength of the strands, the stress imposed to the anchor, and concrete bearing against theprojected area of the anchor.

The appropriate strand stress available to resist ultimate load (fgu*) at this section shall be nogreater than [(Ld / D -2/3 fse] where:

Ld is the developed length available

D is the diameter of the strand

fse is the effective prestress in steel after all losses.

Strand DevelopmentFigure 6.2.3-4



6.2-10 July 2000

G. Fabrication and Handling

1. Shop Plans

Fabricators of prestressed girders are required to submit shop plans which show specific detailsfor each girder that they construct. These shop plans are checked and approved by the ProjectEngineer’s office for conformance with the Contract Plans and specifications.

2. Special Problems for Fabricators

a. Strand Tensioning

The method selected for strand tensioning may affect the design of the girders. The strandarrangements shown in the office standard plans and included in the Prestressed GirderDesign computer program are satisfactory for tensioning methods used by fabricators in thisstate. Harped strands are normally tensioned by pulling them as straight strands to a partialtension. The strands are then deflected vertically as necessary to give the required harpingangle and strand stress. In order to avoid overtensioning the harped strands by this proce-dure, the slope of the strands is limited to a maximum of 6:1 for 1/2″ φ strands and 8:1 for0.6″ φ strands. The straight strands are tensioned by straight jacking.

b. Hold Down Forces

Forces on the hold-down units are developed as the harped strands are raised. The hold-downdevice provided by the fabricator must be able to hold the vertical component of the harpingforces. Normally a two or more hold-down unit is required. Standard commercial hold-downunits have been preapproved for use with particular strand groups.

c Numbers of Strands

Since the prestressing beds used by the girder fabricators can carry several girders in a line,it is desirable that girders have the same number of strands where practical. This allowsseveral girders to be set up and cast at one time and saves both time and strand material.

3. Handling and Hauling of Long Prestressed Girders

a. General

Considerations for handling and shipping long prestressed girders relate primarily to weight,length, height, and lateral stability. The effect of each variable differs considerably depend-ing on where the handling is taking place: in the plant, on the road, or at the jobsite.

b. In-Plant Handling

The primary considerations for in-plant handling are weight and lateral stability. Themaximum weight that can be handled by precasting plants in the Pacific Northwest is200 kips. Pretensioning lines are normally long enough so that the weight of a girdergoverns capacity, rather than its length. Headroom is also not generally a concern for thedeeper sections.

Lateral stability can be a concern when handling long, slender girders. When the girder isstripped from the form, the prestressing level is higher and the concrete strength is lowerthan at any other point in the life of the member.



July 2000 6.2-11

The WSDOT prestressed girder sections are relatively wide and stiff about their weak axesand, as a result, exhibit good stability, even at their longer pretentioned lengths. The simplestmethod of improving stability is to move the lifting devices away from the ends. Thisinvariably increases the required concrete release strength, because decreasing the distancebetween lifting devices increases the concrete stresses at the harp point. Stresses at thesupport may also govern, depending on the exit location of the harped strands.

Alternatively, the girder sections may be braced to provide adequate stability. Temporaryprestressing in the top flange can also be used to provide a larger factor of safety againstcracking.

Other types of bracing have also been used successfully for many years. These systemsare generally based on experience rather than theory. Other methods of improving lateralstability, such as raising the roll axis of the girder, are also an option.

For stability analysis of prestressed girder during in-plant handling in absence of moreaccurate information, the following parameters shall be used:

• Height of pick point above top of girder = 0.0 in

• Lifting loop or lifting bars placement tolerance = 0.25 in

• Maximum girder sweep tolerance = 0.00052 in/in

c. Pick Up Points

The office standard plans show pick-up points for the girders. These points are critical sincethe girder is in its most highly stressed condition just after strand release. In some cases,fabricators may request to move the pick-up points toward the center of the girder. Therequest must be reviewed carefully since a decrease in girder dead load moment nearcenterline span may cause overstressing of the girder. Similarly, the girders must never besupported at any point other than the centerline of bearing during storage. The girders arealso very sensitive to lateral loads and accordingly must be stored in a true vertical position.

d. Girder Lateral Bending

Long prestressed girders are very flexible and highly susceptible to lateral bending. Lateralbending failures are sudden, catastrophic, costly, pose a serious threat to workers andsurroundings, and therefore must be guarded against. The office standard plans state thatgirders over certain given lengths must be laterally braced and that all girders must behandled carefully. It is the fabricator’s responsibility to provide adequate bracing andprovide suitable handling facilities. On unusually long girders, however, the designer shouldgive this matter additional consideration. Published material on girder lateral bending shouldbe consulted and used to assure the constructability of the girder design chosen (14, 17,18, 19).

e. Shipping

The ability to ship deep girder sections can be influenced by a large number of variables,including mode of transportation, weight, length, height, and lateral stability. Some variableshave more influence than others. As such, the feasibility of shipping deep girders is stronglysite-dependent. It is recommended that routes to the site be investigated during the prelimi-nary design phase. To this end, on projects using long, heavy girders, WSDOT can place anadvisory in their special provisions including shipping routes, estimated permit fees, escortvehicle requirements, Washington State Patrol requirements, and permit approval time.



6.2-12 July 2000

f. Mode of Transportation

Three modes of transportation are commonly used in the industry: truck, rail, and barge.In Washington State, an overwhelming percentage of girders are transported by truck, sodiscussion in subsequent sections will be confined to this mode. However, on specificprojects, it may be appropriate to consider rail or barge transportation.

Standard rail cars can usually accommodate larger loads than a standard truck. Rail carsrange in capacity from approximately 120 to 200 kips. However, unless the rail system runsdirectly from the precasting plant to the jobsite, members must be trucked for at least someof the route, and weight may be restricted by the trucking limitations.

For large number of girders construction, barge transportation is usually most economical.Product weights and dimensions are generally not limited by barge delivery, but by thehandling equipment on either end. In most cases, if a product can be made and handled inthe plant, it can be shipped by barge. Of course, this applies only if both the plant and jobsiteare fully accessible by barge.

g. Weight Limitations

Girders shipped in some states have weighed in excess of 200 kips. The net weight limitationwith trucking equipment currently available in Washington State is approximately 167 to180 kips, if a reasonable delivery rate (number of pieces per day) is to be maintained.Product weights of up to 200 kips can be hauled with currently available equipment at alimited rate.

Local carriers should be consulted on the feasibility of shipping heavy girders on specificprojects. Some girders can be fabricated and shipped in two or more segments to reduce theweight and assembled and post-tensioned at the bridge site. However, it is more economicalto fabricate and ship a single-piece pretensioned girder whenever possible.

h. Length Limitations

Length limitations are generally governed by turning radii on the route to the jobsite.Potential problems can be circumvented by moving the support points closer together (awayfrom the ends of the girder), or by selecting alternate routes. A rule of thumb of 130 feetbetween supports is commonly used. The support points can be moved away from the endswhile still maintaining the concrete stresses within allowable limits. Length limitations arenot expected to be the governing factor for most project locations.

i. Height Limitations

The height of a deep girder section sitting on a jeep and steerable trailer is of concern whenconsidering overhead obstructions on the route to the jobsite. The height of the support isapproximately 6 feet above the roadway surface. When adding the depth of the girder,including camber, the overall height from the roadway surface to the top of concrete canrapidly approach 14 feet. Overhead obstructions along the route should be investigated foradequate clearance in the preliminary design phase. Obstructions without adequate clearancemust be bypassed by selecting alternate routes.



July 2000 6.2-13

Expectations are that, in some cases, overhead clearance will not accommodate the verticalstirrup projection on deeper WSDOT standard girder sections. Alternate stirrup configura-tions can be used to attain adequate clearance, depending on the route from the plant tothe jobsite.

j. Lateral Stability During Shipping

Long, slender members can become unstable when supported near the ends. However, thestability of girders sitting on flexible supports is governed by the rotational stiffness of thesupport rather than the girder. Recommended factors of safety 1.0 against cracking, and1.5 against failure (rollover of the truck) should be used.

The control against cracking the top flange is obtained by introducing the number of temp-orary top strands, jacked to the same load as the permanent strands, required to provide afactor of safety of 1.0. This variable depends on the combination of girder dead load, pre-stressing, and tension in the top flange induced by the girder tilt. The calculated tilt includesboth the superelevation and its magnification based on the truck’s rotational stiffness.

For stability analysis of prestressed girders during shipping, in absence of more accurateinformation, the following parameters shall be used:

• Roll stiffness of truck/trailer = 40500 kip-in/rad• Height of girder bottom above roadway = 72 in• Height of truck roll center above road = 24 in• Center to center distance between truck tires = 72 in• Maximum expected roadway superelevation = 0.06• Maximum girder sweep tolerance = 0.001042 in/in• Support placement lateral tolerance = 1 in• Increase girder C.G. height for camber by 2%

k. Erection

A variety of methods are used to erect precast concrete girders, depending on the weight,length, available crane capacity, and site access. Lifting long girders during erection is not ascritical as when they are stripped from the forms, particularly when the same lifting devicesare used for both. However, if a separate set of erection devices are used, the girder shouldbe checked for stresses and lateral stability. In addition, once the girder is set in place, thefree span between supports is usually increased. Wind can also pose a problem. Conse-quently, when long girders are erected, they should immediately be braced at the ends.Generally, the temporary support of the girders is the contractor’s responsibility.

l. Construction Sequence for Muli-Span Prestressed Girder Bridges

For multi-span prestressed girder bridges, the sequence and timing of the superstructureconstruction has a significant impact on the performance and durability of the bridge. Inorder to maximize the performance and durability, the “construction sequence” detailsshown on the attached sheets shall be followed for all new WSDOT multi-span prestressedgirder bridges. Particular attention shall be paid to the timing of casting the lower portion ofthe pier diaphragms/crossbeams (30 days minimum after release of prestress) and the upperportion of the diaphragms/crossbeams (10 days minimum after placement of the roadwayslab). The requirements apply to multi-span prestressed girder bridges with monolithic andhinge diaphragms/crossbeams.



6.2-14 July 2000

4. Repair of Damaged Girders

This section pertains only to girders which have been damaged before becoming part of a finalstructure. Repair of damaged girders in existing bridges is covered in Section 6.3.6.

a. Repairs to Girders Prior to Strand Release

When girders suffer defects during casting or damage prior to strand release, the repairprocedures are documented in reference 6.99.7. Normally, no designer action is required.In prescribing repairs for unusual situations not covered in reference 6.99.7, the designermust ensure that the required strength and appearance of the girder can be maintained. Sincestressing will occur after the repair is made, normally no test loading is required; however,such a test should be considered.

6.2.4 Precast Prestressed (Short Span Bridges)

General — To expedite scheduling and promote economy in building short span bridges, the WSDOT’sBridge Design Office developed standards for short span bridges (range 12 to 70 feet for length of spans).A small bridge program was developed in 1983. A National Cooperative Highway Research ProgramReport (NCHRP) No. 287, entitled Load Distribution and Connection Design for Precast StemmedMultibeam Bridge Superstructures was utilized to obtain the most effective keyway geometry betweenadjacent beam for shear transfer and live load distribution to the girders. These type of bridges are usedonly for low ADT roads.

A. Precast Prestressed Slabs

The slab sections utilize low relaxation prestressing strands and are connected together permanentlywith transverse weld tie and keyway. The following are recommendations for the type of precast slabsections to be used for various span lengths:

1. 12-inch depth precast section (see Appendixes 6.6-A1-1 and 2). This section is capable ofspanning between 15 to 35 feet.

2. 18-inch depth voided precast section (see Appendixs 6.6-A2-1 and 2). This section is capable ofspanning between 30 to 50 feet.

3. 26-inch depth voided precast section (see Appendixs 6.6-A3-1 and 2). This section is capable ofspanning between 40 to 70 feet.

Layout, end abutment, and Intermediate Pier standards have been developed for use with the slabsections noted above (see Appendix 6.6-A4 through A6).

B. Precast Prestressed Tri-Beam

Tri-Beam sections are available as an option to the slab spans. Low relaxation prestressing strands areutilized which enable these sections to span 25 to 70 feet.

Two standards have been developed; one for a 4 foot 0 inch minimum to 6 foot 0 inch maximumwide section (see Appendix 6.7-A1-1 and 2). Standard sheets for abutment and Intermediate pier fortri-beam sections are shown in Appendix 6.7-A3.



July 2000 6.2-15

C. Precast Prestressed Deck Bulb-Tee Girders

Deck bulb-tee girders are also available as an option to the slab sections. Precast fabricators oftenprefer deck bulb-tee girders because voided slabs are less efficient sections. We have developed fourstandard sections while working closely with local fabricator requirements or constraints. 65-inch,53-inch, 41 inch, and a 35-inch deep bulb-tee girders are used by the state of Washington 4-foot,5-foot, and 6-foot wide or variable width deck. For deck bulb tee girders, diaphrams andmiscellaneous details, see Appendix 6.8-A1 through A5.

6.2.5 Precast Box Girders

For moderate bridge spans of up to 160 feet, and where girder depth is critical, precast box girders aregenerally used. These are generally in the form of U-sections called bath-tubs and joined together withwet joint and post-tensioning.

P65:DP/BDM6


Prestressed Concrete Superstructures Precast Girder Bridges

July 2000 6.3-1

6.3 Precast Girder Bridges

The precast prestressed girder bridge is an economical and rapid type of bridge construction. This sectiondiscusses the design of precast prestressed girder bridges.

6.3.1 Criteria for Girder Design

The following criteria is described for simple span bridges. Present practice is to use simple span girderdesigns in continuous prestress bridges. Effects of creep and shrinkage are not considered. This is asomewhat conservative procedure, but it minimizes engineering time. For continuous structures consist-ing of a large number of girders, a more exact analysis could be used, as directed by the design supervi-sor. Additional comments concerning special problems in design of continuous bridges are added below.The design criteria for P/S girders may be summarized in Table 6.3.1-1.

A. Support Conditions

The prestressed girders are assumed to be supported on rigid permanent simple supports. Thesesupports can be either bearing seats or elastomeric pads. The design span length is the distance centerto center of bearings for simple spans. For continuous spans erected on falsework (raised crossbeam),the effective point of support for girder design is assumed to be the face of the crossbeam. Forcontinuous spans on crossbeams (dropped or semi-dropped crossbeam), the design span length isusually the distance center to center of temporary bearings. See Figure 6.2.3-1.

B. Composite Action

1. General

The sequence of construction and loading is extremely important in the design of prestressedgirders. The composite section has a much larger capacity than the basic girder section but itcannot take loads until the slab has obtained adequate strength. For assumptions used incomputing composite section properties, see Figure 6.3.1-1.

2. Load Application

The following sequence and method of applying loads is used in girder analysis:

a. Girder Dead Load

The dead load of the girder is applied to the girder section.

b. Diaphragm Dead Load

The dead load of the diaphragms is applied to the girder section.

c. Slab Dead Load

The dead load of slab is applied to the girder section. Temporary strands shall be removedprior to slab casting.

d. Barrier, Overlay Dead Load, and Live Load

Dead load of one traffic barrier is divided among a maximum of three girders and thisuniform load is applied to the composite section. The dead load of any overlay and live loadplus impact is applied to the composite section.



6.3-2 July 2000

Design Specifications AASHTO Standard Specifications and WSDOT Bridge Design Manual

Design Method Prestressed girder are designed for service load stresses and checked forthe requirements of load factor design.

All other elements are designed in accordance with the requirements ofload factor design.

Design Assumption Prestressed girders are designed as simple span for both simple andcontinuous span superstructures.

Load and Load BDM Articles 4.2 and 4.3Combinations Service load Group I

Load factor design Group I

Allowable Stresses BDM Table 6.2.3-2

Prestress Losses BDM Article 6.1.5 and Table 6.1.5-1

Shear Design Shear Design may be based on one of the following:

• Shear design per AASHTO Standard Specifications 9.20

• Predesigned for shear Standard Prestressed Girder plans

Shipping and BDM Article 6.2.3G-3Handling

Design Criteria for Prestressed Girder SuperstructuresTable 6.3.1-1

3. Composite Section Properties

Minimum deck slab thickness is specified as 7 1/2 inches by office practice, but may be thickerif girder spacing dictates. This slab forms the top flange of the composite girder in prestressedgirder bridge construction. The properties of this slab-girder composite section are affected byspecification and by physical considerations. Figure 6.3.1-1 shows some standard values tobe used for design and detailing.

a. Flange Width

The effective width of slab on each side of the girder centerline which can be considered toact as a compressive flange shall not exceed any of the following:

One-eighth of the span length.

Six times the thickness of slab plus one-fourth of the girder flange width.

One-half the distance to the next girder.

The actual distance to the edge of slab.

For effective tension flange widths, see AASHTO.



July 2000 6.3-3

b. Flange Position

For purposes of calculating composite section properties, the bottom of the slab shall beassumed to be directly on the top of the girder. This assumption may prove to be true atcenter of span when excess girder camber occurs.

For dimensioning the plans, an increased dimension from top of girder to top of slab is usedat centerline of bearing. This is called the “A” dimension. This dimension accounts for theeffects of girder camber, vertical curve, slab cross slope, etc. See Appendix 6.1-A1 formethod of computing.

c. Flange Thickness

For purposes of computing composite section properties, the slab thickness shall be reducedby 1/2 inch to account for wearing. Where it is known that a bridge will have an asphaltoverlay applied prior to traffic being allowed on the bridge, the full slab thickness can beused as effective slab thickness. The effective slab width shall be reduced by the ratio Es/Eg.The effective modulus of composite section is then Eg.

d. Section Dead Load

The slab dead load to be applied to the girder shall be based on full thickness plus anyoverhang. The full effective pad (“A”-t) weight shall be added to that load. This assumedpad weight is applied over the full length of the girder.

4. Shear Transfer

Transfer of shear forces in prestressed girder bridge design is critical in three areas. The first hasbeen previously discussed; the section through the web at the point 1/2 of the girder depth fromthe end of the girder. The other two critical areas for shear transfer are between slab and girderand at the end connection of the girder to the crossbeam for girders in continuous bridges. Shearin these areas will normally be resisted by reinforcement extending from the girder.

a. Shear Between Slab and Girder

This shear represents a rate of change of compression load in the flange of simple spangirders or a rate of change of tension load in the flange near the piers of continuous girders.For a simple span girder as represented by Figure 6.3.1-2, the top flange stress is the factoredcenterline moment divided by the section modulus of the composite girder at the centerlineof the slab. The slab load is this stress times the area of the slab. The factored centerlinemoment can be taken as total factored moment less 1.0 times dead load applied to girder.



6.3-4 July 2000

Composite Prestressed Girder SectionFigure 6.3.1-1



July 2000 6.3-5

Shear in Simple GirderFigure 6.3.1-2

The design composite section slab modulus is used for this shear calculation However, afull slab width should be used to compute force. As an alternate and for a more accurateanalysis, a composite section can be calculated using the full slab width, but this is usuallynot necessary. Further explanation of this calculation and a solved example are available inreference 5.99.4, PCA Notes on Load Factor Design.

This shear is resisted by the girder stirrups which extend up through the interface betweenthe girder and the slab. The top surface of the girder top flange must be roughened. The forcemay be assumed to be carried uniformly over the entire girder top surface from centerlineof bearing to centerline of span. All stirrups in this area can be assumed to be acting inaccordance with the shear friction theory as described in Subsection 5.2.1 C.

For continuous girders, the span, shear, and moment relationships are shown in Figure6.3.1-3. Similar methods are used to analyze slab to girder shear. For positive momentresistance, only those stirrups within length Lc are considered effective in resisting the slabforce due to moment. Likewise, only those stirrups within one continuous length Le are usedto resist the negative moment slab force (tension) in that area.



6.3-6 July 2000

For illustrative purposes, a single concentrated load has been shown. In actual practice, thepoint of factored maximum moment of the actual moment diagram would be used.

Other flange shear problems are described in Section 5.4. These problems also need to beconsidered for prestressed girder bridges.

Shear in Continuous GirderFigure 6.3.1-3

b. Shear at Girder End

A continuous prestressed girder will nearly always be required to carry end reaction shears atthe surface of the end of the girder. An exception to this is girders with notched crossbeamswhere loads must be carried across the connections which act as hinges. See Chapter 5.



July 2000 6.3-7

End Connection for a Continuous Prestressed GirderFigure 6.3.1-4

The usual end condition is similar to that shown in Figure 6.3.1-4. The shear which must becarried along the interface A-A is the actual factored dead load and live load shear acting onthe section. The girder end is required by the plans to be roughened. The sawtoothed shearkey shown on the office standard girder plans may be assumed to provide a friction factor of1.0. Shear resistance must be developed using shear friction theory and assuming the G5 barsand the extended strands to be actively participating. The main longitudinal slab reinforce-ment is already fully stressed by girder bending moments and thus cannot be considered forshear requirements. All bars, including the extended strands, must be properly anchored inorder to be considered effective. This anchorage requirement must be clearly shown onthe plans.

Note that similar requirements exist for connecting the end diaphragm at bridge ends wherethe diaphragm is cast on the girders. In this case, however, loads consist only of the factoreddiaphragm dead load, approach slab dead load, and those wheel loads which can distribute tothe interface.

C. Prestressed Girder Camber

1. General

The computer program ‘PGSDEF’ is used to determine the amount of girder camber forprestressed girder bridges. This program computes the deflections due to prestress, girder deadload, slab dead load, and live load.



6.3-8 July 2000

2. Calculation

Figure 6.3.1-5 shows a typical pattern of girder deflection with time at centerline span. Portionsof this characteristic curve are described below. The subparagraph numbers correspond withcircled numbers on the curve.

a. Elastic Deflection Due to Prestress Force

The prestress force produces moments in the girder tending to bow the girder upward.Resisting these moments are girder section dead load moments. The result is a net upwarddeflection. In addition, a shortening of the girder occurs due to axial prestress loading.

b. Creep Deflection

The girder continues to deflect upward due to the effect of creep. This effect is computedusing the equation stated in Subsection 6.1.2C.2.

c. Diaphragm Load Deflection

The load of diaphragm is applied to the girder section resulting in an elastic downwarddeflection.

d. Deflection Due to Removal of Temporary Strands

Removal of temporary strands results in an elastic upward deflection.

e. Slab Load Deflection

The load of the slab is applied to the girder section resulting in an elastic downwarddeflection. It is this deflection which is offset by the screed camber that is to be applied tothe bridge deck during construction.

f. Final Camber

It might be expected that the above slab dead load deflection would be accompanied bya continuing downward deflection due to creep. Many measurements of actual structuredeflections have shown, however, that once the slab is poured, the girder tends to act asthough it is locked in position. To obtain a smooth riding surface on the deck, the deflectionindicated on Figure 6.3.1-5 as “Screed Camber” is added to the profile grade elevation of thedeck screeds. The actual position of the girder at the time of the slab pour has no effect onthe screed camber.



July 2000 6.3-9

Prestressed Girder CamberFigure 6.3.1-5



6.3-10 July 2000

6.3.2 Framing

A. Girder Selection and Spacing

Cost of the girders is a major portion of the cost of prestressed girder bridges. Much care is thereforewarranted in the selection of girders and in optimizing their position within the structure. Thefollowing general guidelines should be considered.

1. Girder Series Selection

All girders in a bridge will normally be of the same series. If vertical clearance is no problem,a larger girder series, utilizing fewer girder lines, may be a desirable solution. This must bebalanced with considerations such as appearance. At the present time, the following relativegirder series cost factors may be used as a guide for this decision:

RelativeSeries Cost Factors

W42G 0.89W50G 0.93W58G 0.96W74G 1.00WF74G 1.05W83G 1.10W95G 1.25

Note that the small marginal cost factors between series tends to make the larger series moreeconomical.

The wider spacings expected when using larger series girders may result in extra reinforcementand concrete but less forming cost. These items must also be considered.

2. Girder Concrete Strength

Higher girder concrete strengths should be specified where that strength can be effectively usedto reduce the number of girder lines. See Subsection 6.1.2 A.1. When the bridge consists of alarge number of spans, consideration should be given to using a more exact analysis than theusual design program in an attempt to reduce the number of girder lines. This analysis shouldtake into account actual live load, creep, and shrinkage stresses in the girders.

3. Girder Spacing

Consideration must be given to the slab cantilever length to determine the most economicalgirder spacing. This matter is discussed in Subsection 6.3.2.B. The slab cantilever length shouldbe made a maximum if a line of girders can be saved. The spacing of the interior girders mustbe considered at the same time. Once the positions of the exterior girders have been set, thepositions and lengths of interior girders can be established. The following guidance is suggested.

a. Straight Spans

On straight constant width roadways, all girders should be parallel to bridge centerline andgirder spacings should be equal.



July 2000 6.3-11

b. Tapered Spans

On tapered roadways, the minimum number of girder lines should be determined as if allgirder spaces were to be equally flared. As many girders as possible, within the limitations ofgirder capacity should be placed. Slab thickness may have to be increased in some locationsin order to accomplish this.

c. Curved Spans

On curved roadways, normally all girders will be parallel to each other. It is critical that theexterior girders are positioned properly in this case, as described in Subsection 6.3.2.B.

d. Geometrically Complex Spans

Spans which are combinations of taper and curves will require especially careful consider-ation in order to develop the most effective and economical girder arrangement. Wherepossible, girder lengths and numbers of straight and harped strands should be made the samefor as many girders as possible in each span.

e. Number of Girders in a Span

Usually all spans will have the same number of girders. Where aesthetics of the underside ofthe bridge is not a factor and where a girder can be saved in a short side span, considerationshould be given to using unequal numbers of girders. It should be noted that this willcomplicate crossbeam design by introducing torsion effects and that additional reinforcementwill be required in the crossbeam.

B. Slab Cantilevers

The selection of the location of the exterior girders with respect to the curb line of a bridge is acritical factor in the development of the framing plan. This location is established by setting thecurb distance, which is that dimension from centerline of the exterior girder to the adjacent curbline. For straight bridges, the curb distance will normally be no less than 1′-6″ for W42G, W50G,and W58G; 2′-0″ for W74G; and 2′-6″ for WF74G, W83G, and W95G. Some considerationswhich affect this are noted below.

1. Appearance

In the past, some prestressed girder bridges have been designed by placing the exteriorgirders directly under the curb (traffic barrier). This gives a very poor bridge appearance andis uneconomical. Normally, for best appearance, the largest slab overhang which is practicalshould be used.

2. Economy

Fortunately, the condition tending toward best appearance is also that which will normallygive maximum economy. Larger curb distances may mean that a line of girders can beeliminated, especially when combined with higher girder concrete strengths.

3. Slab Strength

This is one of the governing conditions which limits the maximum practical curb distance.Chapter 5 Appendix, gives some guidance for cantilever design. It must be noted that forlarger overhangs, the slab section between the exterior and the first interior girder may becritical and may require thickening. In some cases, live load moments which producetransverse bending in the exterior girder should be considered.



6.3-12 July 2000

4. Drainage

Where drainage for the bridge is required, water from bridge drains is normally piped acrossthe top of the girder and dropped inside of the exterior girder line. A large slab cantileverlength may severely affect this arrangement and it must be considered when determiningexterior girder location.

5. Bridge Curvature

When straight prestressed girders are used to support curved roadways, the curb distancemust vary. Normally, the maximum slab overhang at the centerline of the long span will bemade approximately equal to the overhang at the piers on the inside of the curve. At thepoint of minimum curb distance, however, the edge of the girder top surface should be nocloser than 6 inches from the slab edge. Where curvature is extreme and the differencebetween maximum and minimum curb distance becomes large, say 1 foot 6 inches, othertypes of bridges should be considered. Straight girder bridges on highly curved alignmentshave a poor appearance and also tend to become structurally less efficient.

C. Diaphragm Requirements

1. General

Diaphragms used with prestressed girder bridges serve two purposes. During the construc-tion stage, the diaphragms provide girder stability for pouring the slab. During the life of thebridge, the diaphragms act as load distributing elements, and are particularly advantageousfor distribution of large overloads. Standard diaphragms and diaphragm spacings are given inthe office standards for prestressed girder bridges. Diaphragms that fall within the limitationsstated on the office standards need not be analyzed. Where large girder spacings are to beused or other unusual conditions exist, special diaphragm designs should be performed.

2. Design

Diaphragms shall be designed as transverse beam elements carrying both dead load andlive load. Wheel loads for design shall be placed in positions so as to develop maximummoments and maximum shears.

3. Geometry

Diaphragms shall normally be oriented parallel to skew (as opposed to normal to girdercenterlines). This procedure has the following advantages:

a. The build-up of higher stresses at the obtuse corners of a skewed span is minimized.This build-up has often been ignored in design.

b. Skewed diaphragms are connected at points of approximately equal girder deflectionsand thus tend to distribute load to the girders in a manner which more closely duplicatesdesign assumptions.

On curved bridges, diaphragms shall normally be placed on radial lines.



July 2000 6.3-13

D. Skew Effects

Skew in prestressed girder bridges affects structural behavior and member analysis andcomplicates construction.

1. Analysis

Normally, the effect of skew on girder analysis is ignored. It is assumed that skew has littlestructural effect on normal spans and normal skews. For short, wide spans and for extremeskews (values over 50 degrees), the effect of the skew on structural action should beinvestigated. All short span prestressed slabs, tri-beams, and bulb-tee girders have a skewrestriction of 30 degrees.

2. Detailing

To minimize labor costs and to avoid stress problems in prestressed girder construction, theends of girders for continuous spans shall normally be made skewed. When girder ends areskewed, the angle of the girder end should be rounded to the nearest 5 degrees. If this causesproblems where the girder extends into the crossbeam, the angle can be specified to thenearest degree. See Standard Specifications for girder tolerances.

E. Grade and Cross Slope Effects

Large cross slopes require an increased amount of girder pad dimension (‘A’ dimension) neces-sary to ensure that the structure can be built. See Appendix 6.1-A1. This effect is especiallypronounced if the bridge is on a horizontal or vertical curve. Care must be taken that deckdrainage details reflect the cross slope effect (see Subsection 6.3.2 B). Girder lengths may needto be modified to correct for added length along slope. Remember that the girder is a rectangle inelevation; thus, the position of the girder top corner is affected by grade, girder camber, andtolerances. Details must account for this.

F. Curve Effect and Flare Effect

Curves and tapered roadways each tend to complicate the design of straight girders. The designermust determine what girder spacing to use for dead load and live load design and whether or nota refined analysis, that considers actual load application, is warranted. Normally, the girderspacing at centerline of span can be used for girder design, especially in view of the conservativeassumptions made for the design of continuous girders.

G. Always skew ends of prestressed girders shall match the piers they rest on at either end.

6.3.3 Reinforcement

This section discusses reinforcement requirements for resistance of longitudinal moments in continuousmulti-span precast girder bridges and is limited to reinforcement in the top slab since capacity for resistingpositive moment is provided by the prestressing of the girders.

A. Simple Spans

For simple span bridges, longitudinal slab reinforcement is not required to resist negative momentsand therefore the reinforcement requirements are nominal. Figure 6.3.3-1 defines longitudinalreinforcement requirements for these slabs. The bottom longitudinal reinforcement is defined byAASHTO requirements for distribution reinforcement. The top longitudinal reinforcement is basedon current office practice. The requirements of Distribution of Flexural Reinforcement do not applyto these bars.



6.3-14 July 2000

Nominal Longitudinal Slab Reinforcement for Prestressed Girder BridgesWith Main Reinforcement Perpendicular to Traffic

Figure 6.3.3-1

B. Continuous Spans

1. General

Longitudinal reinforcement of continuous spans at intermediate support is dominated bythe moment requirement. Where these bars are cut off, they are lapped by the nominal toplongitudinal reinforcement described in Subsection 6.3.3A. Typical arrangement of transverseand longitudinal reinforcement is shown in Figure 6.3.3-1.

2. Distribution of Flexural Reinforcement

The provision of AASHTO specifications dealing with this subject is provided to limit crackwidth. At service load, the value of “z” for the equation fs = z/ (dc A)1/3 shall be taken as130 k/inch regardless of whether or not a deck seal or overlay is used. Figure 6.3.3-2 showsthe area to be used for computing “A.” For unevenly spaced bars, this area can be computedas: Total Flange Area/Number of Bars.

3. Distribution Reinforcement

Figure 6.3.3-3 shows typical arrangement of main reinforcement in the slab. “Distributionreinforcement” shall be accounted for in the bottom longitudinal layer as follows:

a. Prestressed Girder Bridges with Girders Designed as Simple Spans

For bridges designed using the “Prestressed Girder Design” program, “distributionreinforcement” need not be added to the area of steel required to resist the negativemoments. The bars in the bottom layer, however, shall provide an area not less than thatrequired for distribution reinforcement.



July 2000 6.3-15

Placement of Longitudinal Reinforcement for Negative Moment Over PiersFigure 6.3.3-2

b. Other Prestressed Girder Bridges

On bridges where the effect of continuity is taken into account to reduce moments forgirder design, additional longitudinal steel shall be provided as “distribution reinforcement.”The sum of the areas in both layers of longitudinal bars shall be equal to the area required toresist negative moments plus the area required by the AASHTO specification for “distribu-tion reinforcement.” Equal area of reinforcement shall be used in the top and bottom layersthroughout the negative moment region. See Figure 6.3.3-2. The total area of steel requiredin the bottom longitudinal layer shall not be less than that required for “distributionreinforcement.” (For “distribution reinforcement,” see Figure 6.3.3-1.)



6.3-16 July 2000

The minimum clearance between top and bottom bars should be 1-inch . Table 6.3.3-1 showsrequired slab thickness for various bar combinations.

Minimum Slab Thickness = 7 Inches

Slab Thickness (Inches)

Transv. Bar

Longit. Bar #5 #6 #7

#4 71/2 -- --

5 71/2 71/

2 73/4

6 71/2 73/

4 8

7 73/4 8 81/

4

8 8 81/2 83/

4

9 81/2 83/

4 9

10 83/4 -- --

11 -- -- --

14 -- -- --

18 -- -- --

Minimum Slab Thickness for Various Bar Sizes(Slab Without Overlay)

Table 6.3.3-1

Note: Deduct 1/2-inch from slab thickness shown in table when asphalt overlay is usedand 1 inch when concrete overlay is used. However, the minimum slab thickness shallbe 7 inches when overlay is used.

3. Bar Patterns

Figure 6.3.3-3 shows two typical top longitudinal reinforcing bar patterns. Care must betaken that bar lengths conform to the requirements of Chapter 5. Note that the reinforce-ment is distributed over a width equal to the girder spacing according to office practiceand does not conform to AASHTO.



July 2000 6.3-17

Staggered Bar PatternFigure 6.3.3-3

The symmetrical bar pattern shown should normally not be used when required barlengths exceed 60 feet. If the staggered bar pattern will not result in bar lengths withinthe limits specified in Chapter 5, the method shown in Figure 6.3.3-4 may be used toprovide an adequate splice. All bars shall be extended development length beyond thepoint where the bar is required.

Bar Splice Within Moment EnvelopeFigure 6.3.3-4



6.3-18 July 2000

In all bar patterns, the reinforcement shall be well distributed between webs. Where thiscannot be done without exceeding the 1-foot 0-inch maximum spacing requirement,the nominal longitudinal bars may be extended through to provide the 1-foot 0-inchmaximum.

Normally, no more than 20 percent of the main reinforcing bars shall be cut off at onepoint. Where limiting this value to 20 percent leads to severe restrictions on the rein-forcement pattern, an increase in this figure may be considered. Two main reinforce-ment bars shall be carried through the positive moment area as stirrup hangers.

6.3.4 Roadway Slab

Requirements for longitudinal reinforcement of roadway slabs for prestressed girder bridges have beengiven in Subsection 6.3.3. The following information is intended to provide guidance for slab thicknessand transverse reinforcement.

Information on deck deterioration prevention systems is provided in Chapter 8.

A. Slab Thickness

1. General

Slab thickness for prestressed girder bridges shall be controlled by the following limitations:

a. Seven inches minimum thickness when overlay is used; Seven and one-half inches minimumwithout overlay.

b. The requirements for proper reinforcement clearances.

c. The requirements of strength.

The 7-inch or 71/2 inch minimum thickness is established in order to ensure that overloads on thebridge will not result in premature slab cracking.

The requirement of adequate reinforcement clearances: 2 inches clear to top transversereinforcement for slabs with overlay and 21/2 inches clear to top transverse reinforcement forslabs without overlay; 1-inch clear to bottom transverse reinforcement.

2. Computation of Slab Strength

The thickness and reinforcement requirements for usual slabs are shown in Chapter 5. The slabdesign span is defined Figure 6.3.1-1 (Composite Prestressed Girder Section).

The thickness of the slab and reinforcement in the area of the cantilever may be governed bytraffic barrier loading. See appendix sheet in Chapter 5. Wheel loads plus dead load shall beresisted by the sections shown in Figure 6.3.4-1.

Cantilever loads may govern the slab thickness just inside the exterior girder as shown by “Z”in Figure 6.3.4-1.

Design of the cantilever is normally based on the expected depth of slab at centerline of girderspan. This is less than the dimensions at the girder ends. See Subsection 6.3.4A.3.



July 2000 6.3-19

Depths for Slab Design at Centerline of Girder SpanFigure 6.3.4-1

3. Computation of “A” Dimension

The distance from the top of the slab to the top of the girder at centerline bearing (A dimen-sion) is calculated in accordance with the guidance of Appendix 6.1-A1. This ensures thatadequate allowance will be made for effects of excess camber, superelevation vertical curve,and horizontal curvature. Ideally the section at centerline of span will have the final geom-etry shown in Figure 6.3.4-2. This must be modified to account for excess camber whichmay be present in the girders when the slab is poured. Where temporary prestressing strandsat top of girder are used to control the girder stresses due to shipping and handling, the “A”dimension shall be adjusted accordingly.

Geometry for A DimensionFigure 6.3.4-2



6.3-20 July 2000

B. Transverse Reinforcement

The size and spacing of transverse reinforcement may be governed by interior slab span design,cantilever design, or the requirements of traffic barrier load. Where traffic barrier load governs,short hooked bars may be added at the slab edge to increase the reinforcement available in thatarea. Top transverse reinforcement is always hooked at the slab edge unless a traffic barrier is notused. Top transverse reinforcement is preferably spliced at some point between girders in orderto allow the clearance of the hooks to the slab edge forms to be properly adjusted in the field.Usually, the slab edge hooks will need to be tilted in order to place them. On larger bars, theclearance for the longitudinal bar through the hooks should be checked. Bottom transverse slabreinforcement is normally carried far enough to splice with the traffic barrier main reinforcement.The appendix in Chapter 5 can be used to aid in selection of bar size and spacing.

For skewed spans, the transverse slab reinforcement is placed parallel to the skew for skewangles of 10 degrees or less. Where skew angles exceed 10 degrees, the transverse bars areplaced normal to bridge centerline and the areas near the expansion joints and bridge ends arereinforced by partial length bars. For raised crossbeam bridges, the bottom transverse slabreinforcement is discontinued at the crossbeam.

The spacing of bars over the crossbeam must be detailed to be open enough to allow concrete tobe poured into the crossbeam. For typical requirements, see Subsection 6.3.5.

For slabs with a crowned roadway, the bottom surface and rebar of the slab should be flat, asshown in Figure 6.3.4-3 below.

Bottom of Top Slab at Crown PointFigure 6.3.4-3



July 2000 6.3-21

6.3.5 Crossbeam Design

A. General

Crossbeam shall be designed in accordance with the requirements of Load Factor Design, LFD, andshall satisfy the serviceability requirements for crack control.

B. Loads

For concrete box girders, prestressed giders with hinged or fixed diaphragms, the superstructure deadload shall be considered as uniformly distributed over the crossbeam. For prestressed girders or othertype of girders sitting on the bearings, the superstructure dead load shall be considered as concen-trated loads to the crossbeam at girder on web locations.

For concrete box girders, prestressed girders with hinged or fixed diaphragms, the live load shall beconsidered as the truck load directly to the crossbeam from the wheel axles. Truck axles shall bemoved transversely over the crossbeam to obtain the maximum design forces for the crossbeam andsupporting colums. For prestressed girders or other type of girders sitting on the bearings, the liveload shall be considered as concentrated loads to the crossbeam at girder locations.

C. Geometry and Construction Requirement

The crossbeam section consists of rectangular section with overhanging deck and bottom slab ifapplicable. The overhang length of the crossbeam shall be taken as the lesser of 6 times slab thick-ness, 1/10 of column spacing, or 1/20 of crossbeam cantilever. The rectangular section of thecrossbeam shall have a minimum width of column dimension plus 6 inches.

Geometry and Construction RequirementsFigure 6.3.5-1



6.3-22 July 2000

Crossbeam is usually cast to the fillet below the top slab. To avoid cracking of concrete on top of thecrossbeam, construction reinforcement shall be provided at approximately 3 inches below theconstruction joint. The design moment for construction reinforcement shall be the factored negativedead load moment due to the weight of crossbeam and adjacent 10 feet of superstructure. The totalamount of construction reinforcement shall be adequate to develop an ultimate moment at the criticalsection at least 1.2 times the cracking moment Mcr.

Where, Mcr = 7.5

Mu > = 1.2 Mcr

D. Skin Reinforcement

If the depth of crossbeam exceeds 3 feet, longitudinal skin reinforcement shall be provided on bothsides of the member for a distance of d/2 nearest the flexural reinforcement. The area of skin rein-forcement per foot of height on each side shall be Ask >= 0.012 (d-30)

The maximum spacing of skin reinforcement shall not exceed d/6 or 12 inches whichever is less.

6.3.6 Repair of Damaged Bridge Girders

A. General

This section is intended to cover repair of damaged girders on existing bridges. For repair of newlyconstructed girders, see Section 6.2.3G. Overheight loads are a fairly common source of damage toprestressed girder bridges. The damage may range from spalling and minor cracking of the lowerflange of the girder to loss of a major portion of a girder section. Occasionally, one or more strandsmay be broken. The damage is most often inflicted on the exterior or first interior girder.

B. Repair Procedure

The determination of degree of damage of a prestressed girder is largely a matter of judgment.Where the flange area has been reduced or strands lost, calculations can aid in making this judgmentdecision. The following are general categories of damage and suggested repair procedures.

1. Minor Damage

If the damage is slight and concerns only spalling of small areas of the outside surface of theconcrete, repair may be accomplished by replacing damaged concrete areas with concrete grout.The area where new concrete is to be applied shall first be thoroughly cleaned of loose material,dried, and then coated with epoxy.

2. Moderate Damage

If damage is moderate, consisting of loss of a substantial portion of the flange and possibly lossof one or more strands, a repair procedure must be developed using the following guidelines. It isprobable that some prestress will have been lost in the damaged area due to reduction in sectionand consequent strand shortening or through loss of strands. The following repair procedure isrecommended to assure that as much of the original girder strength as possible is retained:

a. Determine Condition

Sketch the remaining cross section of the girder and compute its reduced section properties.Determine the stress in the damaged girder due to the remaining prestress and loads in thedamaged state. If severe overstresses are found, action must be taken to restrict loads on the

√ fc′IgYt



July 2000 6.3-23

structure until the repair has been completed. If the strand loss is so great that AASHTOprestress requirements cannot be met with the remaining strands, consideration should begiven to replacing the girder.

b. Restore Prestress If Needed

If it is determined that prestress must be restored, determine the stress in the bottom fiberof the girder as originally designed due to DL + LL + I + Prestress. (This will normally beabout zero psi). Determine the additional load (P) that, when applied to the damaged girderin its existing condition, will result in this same stress. Take into account the reduced girdersection, the effective composite section, and any reduced prestress due to strand loss. Shouldthe damage occur outside of the middle one-third of the span length, the shear stress with theload (P) applied should also be computed. Where strands are broken, consideration should begiven to coupling and jacking them to restore their prestress.

c. Prepare a Repair Plan

Draw a sketch to show how the above load is to be applied and specify that the damaged areais to be thoroughly prepared, coated with epoxy, and repaired with grout equal in strength tothe original concrete. Specify that this load is to remain in place until the grout has obtainedsufficient strength. The effect of this load is to restore lost prestress to the strands whichhave been exposed.

d. Test Load

Consideration should be given to testing the repaired girder with a load equivalent to 1.0DL+ 1.5(LL + I).

3. Severe Damage

Where the damage to the girder is considered to be irreparable due to loss of many strands,extreme cracking, etc., the girder may need to be replaced. This has been done several times, butinvolves some care in determining a proper repair sequence.

In general, the procedure consists of cutting through the existing slab and diaphragms andremoving the damaged girder. Adequate exposed reinforcement steel must remain to allowsplicing of the new bars. The new girder and new reinforcement is placed and previously cutconcrete surfaces are cleaned and coated with epoxy. New slab and diaphragm portions are thenpoured.

It is important that the camber of the new girder be matched with that in the old girders.Excessive camber in the new girder can result in inadequate slab thickness. Girder camber can becontrolled by prestress, curing time, or dimensional changes.

Pouring the new slab and diaphragms simultaneously in order to avoid overloading the existinggirders in the structure should be considered. Extra bracing of the girder at the time of slab pourshould be required.

Methods of construction should be specified in the plans that will minimize inconvenience anddangers to the public while achieving a satisfactory structural result. High early strength groutsand concretes should be considered.



6.3-24 July 2000

C. Miscellaneous References

Some of the girder replacement contracts which have been completed are:

C-9593 Columbia Center 1C Brs. 12/432 Repair (Simple Span)

C-9593 16th Avenue IC-Br. 12/344 Repair (Continuous Span)

C-9446 Mae Valley U-Xing (Simple Span)

KD-2488 13th Street O-Xing 5/220 (Northwest Region)

KD-2488 SR 506 U-Xing 506/108 (Northwest Region)

SR 12 U-Xing 12/118 (Northwest Region)

C-5328 Bridge 5/411 NCD (Continuous Span)

KD-2976 Chamber of Commerce Way Bridge 5/227

KD-20080 Golder Givens Road Bridge 512/10

KD-2154 Anderson Hill Road Bridge 3/130W

These and other similar jobs should be used for guidance.

P65:DP/BDM6


Prestressed Concrete Superstructures Cast-in-Place Bridges

July 2000 6.4-1

6.4 Cast-in-Place Bridges

6.4.1 Design Parameters

A. General

Post-tensioning is generally used for cast-in-place construction since pretensioning is generallypractical only for fabricator-produced structural members. The Post-Tensioned Box Girder BridgeManual published by the Post-Tensioning Institute in 1978 is recommended as the guide for design.This manual discusses longitudinal post-tensioning of box girder webs and transverse post-tensioningof box girder slabs, but the methods apply equally well to other types of bridges. The followingrecommendations are intended to augment the PTI Manual and the AASHTO Code and point outwhere current WSDOT practice departs from practices followed elsewhere.

The AASHTO criteria for reinforced concrete apply equally to bridges with or without post-tensioning steel. However, designers should note certain requirements unique to prestressed concretesuch as special f-factors, load factors (see Chapters 4 and 9 of this manual), and shear provisions.

B. Bridge Types

Post-tensioning has been used in various types of cast-in-place bridges in this state with box girderspredominating. See Appendix 6.4-B1 for a comprehensive list of box girder designs. The followingare some examples of other bridge types:

Kitsap CountyMulti-Span SlabC-9788

Covington Way to 180th Avenue SE WideningTwo-Span Box GirderLongitudinal Post-TensioningC-4919

Snohomish River BridgeMulti-Span Box GirderLongitudinal Post-TensioningC-4444

Chapter 2 of this manual should be consulted when selecting the structure type. In general, aprestressed cast-in-place bridge can have a smaller depth-to-span ratio than the same bridge withconventional reinforcement. This is an important advantage where minimum structure depthis desirable.

1. Slab Bridge

Structure depth can be quite shallow in the positive moment region when post-tensioning iscombined with haunching in the negative moment region. However, post-tensioned cast-in-placeslabs are usually more expensive than when reinforced conventionally. Designers should proceedwith caution when considering post-tensioned slab bridges because severe cracking in the decksof bridges of this type has occurred. See reference 6.99.9 of the Bibliography.



6.4-2 July 2000

2. T-Beam Bridge

This type of bridge, combined with slope-leg columns, can be structurally efficient andaesthetically pleasing, particularly when the spacing of the beams and the columns are the same.A T-Beam bridge can also be a good choice for a single-span simply-supported structure.

3. Box Girder Bridge

This type of bridge has been a popular choice in this state. The cost of a prestressed box girderbridge is practically the same as a conventionally-reinforced box girder bridge, however, longerspans and shallower depths are possible with prestressing.

C. Section Requirements

1 Slabs

The Olalla Bridge (Contract 9202) has spans of 41.5 feet - 50 feet - 41.5 feet, a midspan structuredepth of 15 inches, and some haunching at the piers.

2. T-Beams

When equally spaced beams and columns are used in the design, the width of beam webs shouldgenerally be equal to the width of the supporting columns. See SR 16, Union Avenue O’Xings,for an example. Since longitudinal structural frame action predominates in this type of design,crossbeams at intermediate piers can be relatively small and the post-tensioning tendons can beplaced side-by-side in the webs, resulting in an efficient center of gravity of steel line throughout.For other types of T-Beam bridges, the preferred solution may be smaller, more closely spacedbeams and fewer, but larger pier elements. If this type of construction is used in a multispan,continuous bridge, the beam cross-section properties in the negative moment regions need to beconsiderably larger than the properties in the positive moment regions to resist compression.

Larger section properties can be obtained by gradually increasing the web thickness in thevicinity of intermediate piers or, if possible, by adding a fillet or haunch. The slab overhangover exterior webs should be roughly half the web spacing.

3. Box Girders

The superstructure shall be designed as a unit. The entire superstructure section (traffic barrierexcluded) shall be considered when computing the section properties.

Web spacing should normally be 8 to 11 feet and the slab overhang over exterior girders shouldbe approximately half the girder spacing unless transverse post-tensioning is used. The apparentvisual depth of box girder bridges can be reduced by sloping all or the lower portion of theexterior web. If the latter is done, the overall structure depth may have to be increased (forclearance requirements see Subsection 2.3.1D). Web thickness should be 12 inches minimum,but not less than required for shear and for concrete placing clearance. Providing 21/2-inches ofclear cover expedites concrete placement and consolidation in the heavily congested regionsadjacent to the post-tensioning ducts. Webs should be flared at anchorages. Top and bottom slabthickness should normally meet the requirements of Subsection 5.3.1B, but not less than requiredby stress and specifications. Generally, the bottom slab would require thickening at the interiorpiers of continuous spans. This thickening should be accomplished by raising the top surface ofthe bottom slab at the maximum rate of 1/2-inch per foot.

For criteria on distribution of live loads, see Subsection 4.1.2 B. All slender members subjectedto compression must satisfy buckling criteria.



July 2000 6.4-3

D. Strand and Tendon Arrangements

The total number of strands selected should be the minimum required to carry the service loads at allpoints. Duct sizes and the number of strands they contain vary slightly, depending on the supplier.Chapter 2 of the PTI Post-Tensioned Box Girder Bridge Manual, and shop drawings of the recentpost-tensioned bridges kept on file in the Construction Plans Section offer guidance to strand selec-tion. In general, a supplier will offer several duct sizes and associated end anchors, each of which willaccommodate a range of strand numbers up to a maximum in the range. Present WSDOT practice isto indicate only the design force and cable path on the contract plans and allow the post-tensioningsupplier to satisfy these requirements with tendons and anchors. The most economical tendonselection will generally be the maximum size within the range. Commonly-stocked tendons include 9,12, 19, 27, and 31 1/2-inch strands, and the design should utilize a combination of these commonly-stocked items. For example, a design requiring 72 strands per web would be most economicallysatisfied by two standard 27-strand tendons and one standard 19-strand tendon containing 18 strands.A less economical choice would be three standard 27-strand tendons containing 24 strands each.Tendons should not be larger than (31) 1/2-inch strand units or (22) 0.6-inch strand units, unlessspecifically approved by the Bridge Design Engineer and the Design Unit Supervisor. The duct areashould be at least 2.5 times the net area of the prestressing steel. In the regions away from the endanchorages, the duct placement patterns indicated in Figure 6.4.1-1 through -4 should be used.

Although post-tensioning steel normally takes precedence in a member, sufficient room must beprovided for other essential mild steel and placement of concrete, in particular near diaphragms andcross-beams.

More prestress may be needed in certain portions of a continuous superstructure than elsewhere, andthe designer may consider using separate short tendons in those portions of the spans only. However,the savings on prestressing steel possible with such an arrangement should be balanced against thedifficulty involved in providing suitable anchoring points and sufficient room for jacking equipmentat intermediate locations in the structure. For example, torsion in continuous, multigirder bridges ona curve can be counter-balanced by applying more prestress in the girders on the outside of the curvethan in those on the inside of the curve.

Some systems offer couplers which make possible stage construction of long bridges. With suchsystems, forms can be constructed and concrete cast and stressed in a number of spans during stage 1,as determined by the designer. After stage 1 stressing, couplers can be added, steel installed, concretecast and stressed in additional spans. To avoid local crushing of concrete and/or grout, the stressexisting in the steel at the coupled end after stage 1 stressing should not be exceeded during stage 2stressing (see Figure 6.4.1-5).

E. Layout of Anchorages and End Blocks

Consult industry brochures and shop plans for recent bridges before laying out end blocks.To encourage bids from a wider range of suppliers, try to accommodate the large square bearingplate sizes common to several systems.



6.4-4 July 2000

Tendon Placement PatternsBox Girder Bridges

Figure 6.4.1-1



July 2000 6.4-5


Figure 6.4.1-2



6.4-6 July 2000


Figure 6.4.1-3



July 2000 6.4-7


Figure 6.4.1-4



6.4-8 July 2000

Figure 6.4.1-5



July 2000 6.4-9

Plan at Exterior Girder(Roadway Slab Not Shown)

Figure 6.4.1-6



6.4-10 July 2000

Sufficient room must be allowed inside the member for mild steel and concrete placement and outsidethe member for jacking equipment. The size of the anchorage block in the plane of the anchor platesshould be large enough to provide a minimum of 1-inch clearance from the plates to any free edge.

In general, the end block dimensions must meet the requirements of the AASHTO Code. Note that inlong-span box girder superstructures requiring large bearing pads, the end block should be somewhatwider than the bearing pad beneath to avoid subjecting the relatively thin bottom slab to high bearingstresses. When the piers of box girder or T-beam bridges are severely skewed, the layout of endblocks, bearing pads, and curtain walls at exterior girders become extremely difficult (see Figure6.4.1-6). Note that if the exterior face of the exterior girder is in the same plane throughout its entirelength, all the end block widening must be on the inside. To lessen the risk of tendon break-outthrough the side of a thin web, the end block should be long enough to accommodate a horizontaltendon curve of 200 feet minimum radius. For a discussion of the radial component of force in acurved cable, see Chapter 4-7 of reference 6.99.1.

F. Superstructure Shortening

Whenever members such as columns, crossbeams, and diaphragms in bridges without prestressingsteel are appreciably affected by post-tensioning of the main girders, those effects should be includedin the design. This will generally be true in structures containing rigid frame elements. For furtherdiscussion, see Chapter 2.6 of reference 6.99.8 and Subsection 9.3.2.

Past practice in the state of Washington regarding control of superstructure shortening in post-tensioned bridges with rigid piers can be illustrated by a few examples. Single-span bridges have beenprovided with a hinge at one pier and longitudinal slide bearings at the other pier. Two-span bridgeshave been detailed with longitudinal slide bearings at the end piers and a monolithic middle pier. Onthe six-span Evergreen Parkway Undercrossing structure, the center pier (pier 4) was built monolithicwith the superstructure, and all the other piers were constructed with slide bearings. After post-tensioning, the bearings at piers 3 and 5 were converted into fixed bearings to help resist largehorizontal loads such as earthquakes.

Superstructures which are allowed to move longitudinally at certain piers are typically restrainedagainst motion in the transverse direction at those piers. This can be accomplished with suitabletransverse shear corbels or bearings allowing motion parallel to the bridge only. See Subsection9.3.2E of this manual. The casting length for box girder bridges shall be slightly longer than theactual bridge layout length to account for the elastic shortening of the concrete due to prestress.

6.4.2 Analysis

The procedures outlined in Section 2.1 through 2.5 of reference 6.99.8 for computation of stress in singleand multispan box girders can be followed for the analysis of T-beams and slab bridges, as well.

The BDS program available on the WSDOT system will quickly perform a complete stress analysis of abox girder, T-beam, or slab bridge, provided the structure can be idealized as a plane frame. For furtherinformation, see the program user instructions.

The STRUDL program is recommended for complex structures which are more accurately idealized asspace frames. Examples are bridges with sharp curvature, varying superstructure width, severe skew,or slope-leg intermediate piers. An analysis method in Chapter 10 of reference 6.99.1 for continuousprestressed beams is particularly well adapted to the loading input format in STRUDL. In the method,the forces exerted by cables of parabolic or other configurations are converted into equivalent verticallinear or concentrated loads applied to members and joints of the superstructure. The vertical loads are



July 2000 6.4-11

considered positive when acting up toward the center of tendon curvature and negative when acting downtoward the center of tendon curvature. Forces exerted by anchor plates at the cable ends are coded in asaxial and vertical concentrated forces combined with a concentrated moment if the anchor plate group iseccentric. Since the prestress force varies along the spans due to the effects of friction, the differencebetween the external forces applied at the end anchors at opposite ends of the bridge must be coded in atvarious points along the spans in order for the summation of horizontal forces to equal zero. With correctinput (check thoroughly before submitting for computation), the effects of elastic shortening and second-ary moments are properly reflected in all output listings, and the prestress moments printed out are theactual resultant (total) moments acting on the structure. For examples of the application of STRUDL topost-tensioning design, see the calculations for SR 90 West Sunset Way Ramp (simple), SR 5 NalleyValley Viaduct (complex), and the STRUDL manuals.

A. Section Properties

As in other types of bridges, the design normally begins with a preliminary estimate of the superstruc-ture cross-section and the amount of prestress needed at points of maximum stress and at points ofcross-section change. For box girders, See Figure 2.0 through 2.5 of Reference 6.99.8. For T-beamand slab bridges, previous designs are a useful guide in making a good first choice.

For frame analysis, use the properties of the entire superstructure regardless of the type of bridgebeing designed. For stress analysis of slab bridges, calculate loads and steel requirements for a 1-footwide strip. For stress analysis of T-beam bridges, use the procedures outlined in the AASHTOspecifications.

Note that when different concrete strengths are used in different portions of the same member, theequivalent section properties should be calculated in terms of either the stronger or weaker material.In general, the concrete strength should be limited to the values indicated in Subsection 6.1.2A ofthis manual.

B. Preliminary Stress Check

In accordance with AASHTO, flexural stresses in prestressed members are calculated at service loadlevels. Shear stresses, stirrups, moment capacities vs. applied moments are calculated at ultimate loadlevels.

During preliminary design, the first objective should be to satisfy the allowable flexural stresses in theconcrete at the critical points in the structure with the chosen cross-section and amount of prestressingsteel, then the requirements for shear stress, stirrups, and ultimate moment capacity can be readilymet with minor or no modifications in the cross-section. For example, girder webs can be thickenedlocally near piers to reduce excessive shear stress.

In the AASHTO formulas for allowable tensile stress in concrete, bonded reinforcement should beinterpreted to mean bonded auxiliary (nonprestressed) reinforcement in conformity with Article 8.6of the 1995 ACI Code for Analysis and Design of Reinforced Concrete Bridge Structures. Normalpractice is to use the time-dependent prestress loss from Table 6.1.5-1. The long-hand formulas forcomputing time-dependent losses in steel stress given in the code should be used only when a morethorough investigation is deemed necessary. To minimize concrete cracking and protect reinforcingsteel against corrosion for bridges, the allowable concrete stress under final conditions in theprecompressed tensile zone should be limited to zero in the top and bottom fibers.



6.4-12 July 2000

In all cases where tension is allowed in the concrete under initial or final conditions, extra mild steel(auxiliary reinforcement) should be added to carry the total tension present. This steel can becomputed as in the following example (also see Chapter 9-5 of Reference 6.99.1):

Figure 6.4.2-1

In case of overstress, try one or more of the following remedies: Adjust tendon profiles, add orsubtract prestress steel, thicken slabs, revise strength of concrete of top slab, add more short tendonslocally, etc. Then repeat calculations as necessary.

C. Tendon Layout

After a preliminary estimate has been made of the concrete section and the amount of prestressingneeded at points of maximum applied load, it may be advantageous in multispan bridges to draw atendon profile to a convenient scale superimposed on a plot of the center of gravity of concrete(c.g.c.) line. The most efficient tendon profile from the standpoint of steel stress loss will normally bea series of rather long interconnected parabolas, but other configurations are possible. For continuousbridges with unequal span lengths, the tendon profile (eccentricity) shall be based on the spanrequirement. This results in an efficient post-tensioning design. The tendon profile and c.g.c. line plotis strongly recommended for superstructures of variable cross-section and/or multiple unsymmetricalspan arrangements, but is not necessary for superstructures having constant cross- section andsymmetrical spans. The main advantages of the tendon profile and c.g.c. plot are:



July 2000 6.4-13

1. The primary prestress moment curves (prestress force times distance from c.g.c. line to center ofgravity of steel (c.g.s.) lines) at all points throughout all spans are quickly obtained from this plotand will be used to develop the secondary moment curves (if present) and, ultimately, to developthe resultant total prestress moment curve.

2. Possible conflicts between prestressing steel and mild steel near end regions, crossbeams, anddiaphragms may become apparent.

3. Possible design revisions may be indicated. For example, camber in bridges with unequal spanscan be balanced by adjusting tendon profiles.

The tendon profile and c.g.c. line diagram should also contain a sketch of how the end bearingplates or anchors are to be arranged at the ends of the bridge. Such a sketch can be useful indetermining how large the end block in a girder bridge will have to be and how much space willbe required for mild steel in the end region. In general, the arrangement of anchor plates shouldbe the same as the arrangement of the ducts to which they belong to avoid problems with ductcross-overs and to keep end blocks of reasonable width.

D. Prestress Losses

Friction losses occurring during jacking and prior to anchoring, depend on the system and materialsused. For purposes of design, this office has specified a rigid spiral galvanized ferrous metal ductsystem for which µ shall be 0.20 and K = 0.0002. This system is at present available from severallarge suppliers. To avoid the substantial friction loss caused by sharp tendon curvature in the endregions where the tendons flare out from a stacked arrangement towards the bearing plates, use0.10 times the span length or 20 feet as the minimum flare zone length. The recommended minimumradius (horizontal or vertical) of flared tendons is 200 feet. In the special cases where sharp curvaturecannot be avoided, extra horizontal and vertical ties should be added along the concave side of thecurve to resist the tendency to break through the web. See stirrup calculations for SR 2, EU-LineO’Xing, for a suggested method of calculating this additional steel.

When summing the α angles for total friction loss along the structure, horizontal curvature of thetendons as well as horizontal and vertical roadway curvature should be included in the summation.All other losses (those due to shrinkage, elastic shortening, creep, and relaxation of steel) shall be asindicated in Subsection 6.1.5.

E. Steel Stress Curve

Steel stresses may be plotted either as the actual values or as a percentage of the jacking stresses.A steel stress diagram for a typical two-span bridge is shown below. Spans are symmetrical aboutpier 2 and the bridge is jacked from both ends. All values are in ksi and pertain to 270 ksi eitherstress relieved or low relaxation strands. Fs’ denotes ultimate strength of strands in ksi.



6.4-14 July 2000

Losses due to creep, shrinkage, and relaxation of prestressing steel are 33.30 ksi forstructures of usual design and normal weight concrete.

Yield Stress for Stress-Releive Strands = 0.85

Yield Stress for Low-Relaxation Strands = 0.90Figure 6.4.2-2

Accurate plotting of steel stress variation due to local curvature is normally not necessary, andstraight lines between intersection points on the diagram are usually sufficient. When tendons arecontinuous through the length of the bridge, the stress for design purposes at the jacked end should belimited to 0.75 x fs′ or 202 ksi for 270 ksi stress relieved strands or 0.79 x fs′ or 213 ksi for 270 ksilow relaxation strands. This would permit the post-tensioning contractor to jack to the slightly highervalue of 0.77 x fs′ for stress relieved strands or 0.81 x fs′ for low relaxation strands as allowed by theAASHTO Code in case friction values encountered in the field turn out somewhat greater than thestandard values used in design. Stress loss at jacked end should be calculated from the assumedanchor set of 1/4 inch, the normal slippage during anchoring in most systems. At the high points on theinitial stress curve, the stress should not exceed 0.70 x fs′ for stress relieved strands or 0.75 x fs′ lowrelaxation strands after sealing of anchorage. If these values are exceeded, the jacking stress can belowered or alternately the specified amount of anchor set can be increased.

When the total tendon length (L) is less than the length of cable influenced by anchor set (x) and thefriction loss is small, as in short straight tendons, the 0.70 x fs′ value governs. In these cases, themaximum allowable jacking stress value of 0.75 x fs′ for stress relieved or 0.78 x fs′ for low relax-ation strands cannot be used and a slightly lower value should be specified. See the following sketch:



July 2000 6.4-15

Figure 6.4.2-3

In single-span, simply supported superstructures friction losses are so small that jacking from bothends is normally not warranted. In the longer multispan bridges where the tendons experience greaterfriction losses, jacking from both ends will usually be necessary. Jacking at both ends need not bedone simultaneously, since final results are virtually the same whether or not the jacking is simulta-neous. If unsymmetrical two-span structures are to be jacked from one end only, the jacking must bedone from the end of the longest span.

F. Prestress Moment Curves

1. Single-Span Bridges, Simply Supported

The primary prestress moment curve is developed by multiplying the initial steel stress curveordinates by the area of prestressing steel times the eccentricity of steel from the center of gravityof the concrete section at every tenth point in the span. The primary prestress moment curve isnot necessary for calculating concrete stresses in single-span simply supported bridges. Sincethere is no secondary prestress moment developed in the span of a single span, simply supportedbridge which is free to shorten, the primary prestress moment curve is equal to the total prestressmoment curve in the span. However, if the single span is rigidly framed to supporting piers, theeffect of elastic shortening should be calculated. The same would be true when unexpected highfriction is developed in bearings during or after construction.

2. Multispan Continuous Bridges

The primary prestress moment curve for all spans is developed as in 1. above for single spanbridges.

With the exception of T.Y. Lin’s equivalent vertical load method used in conjunction with theSTRUDL program, none of the methods described in the following take into account the elasticshortening of the superstructure due to prestressing. To obtain the total prestress moment curveused to check concrete stresses, the primary and secondary prestress moment curves must beadded algebraically at all points in the spans. As the secondary moment can have a large absolutevalue in some structures, it is very important to obtain the proper sign for this moment, or aserious error could result.



6.4-16 July 2000

A discussion of methods for calculating secondary prestress moments follows:

WSDOT BEAMDEF Program

If the primary prestress moment values at tenth points are coded into this program, spanstiffness factors, carry-overs, and fixed-end moments will be obtained. Distribution of thefixed-end moments in all spans will yield the secondary moments at all piers. The secondarymoments will be zero at simply supported span ends and cantilevers.

Equivalent Vertical Load

See discussion in Subsection 6.4.2 of this manual.

Table of Influence Lines

See Appendix A.1 of Reference 6.99.8 for a discussion. This method is similar to T. Y. Lin’sequivalent vertical load method and is a relatively quick way to manually compute prestressmoments in bridges of up to five spans. Since the secondary moment effect due to verticalsupport reactions is included in the coefficients listed in the tables, the support momentcomputed is the total moment at that point.

Slope Deflection

See Section 2.5 of Reference 6.99.8 for a discussion. The method, though straightforward, istime consuming.

G. Flexural Stress in Concrete

Stress at service load levels in the top and bottom fibers of prestressed members should be checkedfor at least two conditions that will occur in the lifetime of the members. The initial condition occursjust after the transfer of prestress when the concrete is relatively fresh and the member is carrying itsown dead load. The final condition occurs after all the prestress losses when the concrete has gainedits full ultimate strength and the member is carrying dead load and live load. For certain bridges,other intermediate loading conditions may have to be checked, such as when prestressing andfalsework release are done in stages and when special construction loads have to be carried, etc.The concrete stresses shall be within the AASHTO allowables except as amended in Subsection6.4.2.B of this manual.

In single-span simply supported superstructures with parabolic tendon paths, flexural stresses atservice load levels need to be investigated at the span midpoint where moments are maximum, atpoints where the cross-section changes, and near the span ends where shear stress is likely to bemaximum (see Subsection 6.4.2.I, Shear). For tendon paths other than parabolic, flexural stressshould be investigated at other points in the span as well.

In multispan continuous superstructures, investigate flexural stress at service load should be at pointsof maximum moment (in the negative moment region of box girders, check at the quarter point ofthe crossbeam), at points where the cross section changes, and at points where shear is likely to bemaximum. At points of maximum moment, the ultimate moment capacity of the section shouldexceed or equal the applied ultimate moment. Normally, mild steel should not be used to supplementthe ultimate moment capacity. It may be necessary, however, to determine the partial temperature andshrinkage stresses that occur prior to post-tensioning and supply mild steel reinforcing for thiscondition.

In addition, maximum and minimum steel percentages and cracking moment should be checked.See Subsection 2.3.8 of Reference 6.99.8.



July 2000 6.4-17

H. Temperature Effects*

Most specifications for massive bridges call for a verification of stresses under uniform temperaturechanges of the total bridge superstructure. Stresses due to temperature unevenly distributed within thecross-section are not generally verified. In reality, however, considerable temperature gradients areset up within the cross-section of superstructures. Such temperature differences are mostly of a verycomplex nature, depending on the type of cross-section and direction of solar radiation.

Solar radiation produces uniform heating of the upper surface of a bridge superstructure which isgreater than that of the lower surface. An inverse temperature gradient with higher temperatures at thelower surface occurs rarely and involves much smaller temperature differences. In statically indeter-minate continuous bridge beams, a temperature rise at the upper surface produces positive flexuralmoments which cause tensile stresses in the bottom fibers. When the temperature gradient is constantover the entire length of a continuous beam superstructure, positive flexural moments are induced inall spans. These moments are of equal constant magnitude in the interior spans and decrease linearlyto zero in the end spans. The most critical zones are those which have the lowest compressive stressreserve in the bottom fibers under prestress plus dead load. Normally, these are the zones near theinterior supports where additional tensile stresses develop in the bottom fibers due to (1) a concen-trated support reaction and (2) insufficient curvature of prestressed reinforcement.

Studies have shown that temperature is the most important tension-producing factor, especially intwo-span continuous beams in the vicinity of intermediate supports, even when the temperaturedifference is only 10°C between the deck and bottom of the beam. In practice, a box girder canexhibit a DT=30°C. The zone at a distance of about 0.3 to 2.0d on either side of the intermediatesupport proved to be particularly crack-prone.

Computation of stresses induced by vertical temperature gradients within prestressed concrete bridgescan become quite complex and are ignored in typical designs done by WSDOT. It is assumed thatmovements at the expansion devices will generally relieve any induced stresses. However, suchstresses can be substantial in massive, deep bridge members in localities with large temperaturefluctuations. If the structure being designed falls within this category, a thermal stress investigationshould be considered. See Reference 6.99.10 and the following temperature criteria for furtherguidance.

1. A Mean temperature 50°F with Rise 45°F and Fall 45°F for longitudinal analysis using one-halfof the Modulus of Elasticity. (Maximum Seasonal Variation.)

2. The superstructure box girder shall be designed transversely for a temperature differentialbetween inside and outside surfaces of ±15°F with no reduction in Modulus of Elasticity(Maximum Daily Variation).

3. The superstructure box girder shall be designed longitudinally for a top slab temperature increaseof 20°F with no reduction in modulus of elasticity. (In accordance with Post-Tensioning InstituteManual, Precast Segmental Box Girder Bridge Manual, Subsection 3.3.4.)

The coefficient of thermal expansion used is 0.000006.

Modulus of Elasticity Wc1.5 (W=weight of concrete in lbs. per cubic foot).

*From “Conclusions Drawn from Distress of Prestressed Concrete Bridges” by Dr. Fritz Leonardt.

√33 fc′



6.4-18 July 2000

I. Shear

Concrete box girder and T-beam bridges with horizontal construction joints (which result from websand slabs being cast at different times) should be checked for both vertical and horizontal shearcapacity. Generally, horizontal shear requirements will control the stirrup design.

Vertical concrete shear capacity for prestressed or post-tensioned structural members is calculated asthe lesser of Vci or Vcw as outlined in Section 9.20.2 of the AASHTO Standard Specifications forHighway Bridges. Minimum stirrup area, maximum stirrup spacing, and maximum stirrup capacity,Vs, are further subject to the limitations presented in Section 9.20.3. For further explanation, refer toSection 11.4 of the ACI 318-95 Building Code Requirements for Reinforced Concrete and Commen-tary. Chapter 27 of Notes on ACI 318-95 Building Code Requirements for Reinforced Concrete withDesign Applications presents two excellent example problems for vertical shear design. The use ofan electronic spreadsheet simplifies the repetitive and detailed nature of these calculations.

Horizontal shear stress acts over the contact area, of width bv, between two interconnected surfacesof a composite structural member. The moment gradient produced by vertical shear causes thishorizontal stress. At elastic stress levels, this shear stress is generally expressed as t=VQ/(Ibv).Because the concrete section is generally cracked at the full factored load level, VQ/(Ibv), basedupon Q and I of the uncracked section, does not apply. Instead, the moment gradient is, essentially,developed as a couple; the steel reinforcement being in tension and the concrete slab being in com-pression. The distance between these two forces approximately equals the structural depth d. Hence,the resulting horizontal shear stress at the interface can be shown to approximately equal Vu/(bvd).This stress can be resisted by a combination of 1) interlock of the two concrete surfaces and 2) shear-friction resulting from stirrups being placed across the interface. The vertical shear capacity corre-sponding to the concrete horizontal resistance is Vnh-c. The vertical shear capacity corresponding tothe horizontal resistance of the stirrup steel is Vnh-s. The post-tensioning force does not subject thehorizontal interface to compression along the full span length. Therefore, the horizontal concreteshear capacity should not be augmented by Vp, as is done when calculating the vertical concreteshear capacity Vcw.

Horizontal shear design is relatively straightforward. However, the presentation in Section 9.20.4 ofthe AASHTO specifications is somewhat confusing in that it deviates from the standard load factorformat. The AASHTO procedure differs somewhat from the ACI 318-95 procedure which refersdirectly to shear-friction design.

When the concrete interface is clean, free of laitance, intentionally roughened, and has a minimumquantity of stirrup reinforcement of 50bvs/Fy, the AASHTO specifications allow a concrete ultimatehorizontal shear stress of 350 psi, where s is the longitudinal spacing between adjacent stirrups.This corresponds to a concrete vertical shear capacity, Vnh-c, of (350 psi) bvd.

Additional stirrups in a quantity exceeding the specified minimum provide additional vertical shearcapacity, Vnh-s. It is shown below that the equation in Section 9.20.4.3(d) of the AASHTO specifi-cations for additional shear capacity provided by these stirrups is equivalent to designing for theadditional horizontal shear force by mobilizing shear friction using a m value of 0.4.

τ·bv·s = Vnh-s·bv·s/(bv·d)

= [(160·Fy·bv·d/40000)·Av/(.01·bv·s)]·bv·s/(bv·d)

= 0.4·Fy·Av



July 2000 6.4-19

The total stirrup quantity required is the sum of the minimum 50 bv s/Fy and the additional requiredamount to mobilize shear friction.

In load factor notation, these relationships can be expressed as follows:

Vu ≤ φ·Vnh = φ·Vnh-c + φ·Vnh-s

Vnh-s ≥ Vu/φ - Vnh-c

Vnh-c = (350 psi)·bv·d

Vnh-s = 0.4·Av·Fy·d/s

(Av/s)total ≥ 50·bv/Fy + Vnh-s/(0.4·Fy·d)

≥ 50·bv/Fy + 2.5·Vnh-s/(Fy·d)

≥ 50·bv/Fy + 2.5·(Vu/φ - Vnh-c)/(Fy·d)

The horizontal shear requirements of the AASHTO specifications can be satisfied using either of twomethods: (1) Stirrup spacing is designed to satisfy the shear capacity requirement at each and everypoint along the span (AASHTO Section 9.20.4.3), or (2) Stirrup spacing is designed to transfer thechange in flange axial force over a segment length not exceeding one tenth of the span (AASHTOSection 9.20.4.4). The second method permits the designer to average the stirrup spacing over onetenth the span, resulting in an increased minimum stirrup spacing. Again, the use of an electronicspreadsheet can simplify these repetitive computations.

For cast-in-place sloped outer webs, increase inside stirrup reinforcement and bottom slab toptransverse reinforcement as required for the web moment locked-in during construction of the topslab. This moment about the bottom corner of the web is due to tributary load from the top slabconcrete placement plus 10 psf form dead load. See Figure 5.3.2 for typical top slab forming.

For precast tub outer webs, increase the stirrup and bottom slab steel as required by moment inducedby falsework overhang brackets supporting concrete plus 10 psf overhang deck load.

J. End Block Stresses

The highly concentrated forces at the end anchorages cause bursting and spalling stresses in theconcrete which must be resisted by vertical and horizontal reinforcement. For a better understandingof this subject, see Chapter 7 of Reference 6.99.1, 6.99.3, and Section 2.82 of Reference 6.99.8.

Note that the procedures for computing horizontal bursting and spalling steel in the slabs of boxgirders and T-beams are similar to those required for computing vertical steel in girder webs, exceptthat the slab steel is figured in a horizontal instead of a vertical plane. In box girders, this slab steelshould be placed half in the top slab and half in the bottom slab. See Appendix 6.4-A1 for typical boxgirder end block reinforcement details. The anchorage zones of slab bridges will require verticalstirrups as well as additional horizontal transverse bars extending across the width of the bridge.The horizontal spalling and bursting steel in slab bridges shall be placed half in a top layer and halfin a bottom layer.



6.4-20 July 2000

K. Anchorage Stresses

The average bearing stress on the concrete behind the anchor plate and the bending stress in the platematerial should satisfy the requirements of the AASHTO Code. In all sizes up to the 31-strandtendons, the square anchor plates used by three suppliers (VSL, AVAR, Stronghold) meet theAASHTO requirements, and detailing end blocks to accommodate these plates is the recommendedprocedure. In the cases where nonstandard (rectangular) anchor plates must be specified because ofspace limitations, assume that the trumpet associated with the equivalent size square plate will beused. In order to calculate the net bearing plate area pressing on the concrete behind it, the trumpetsize can be scaled from photos in supplier brochures. Assume for simplicity that the concrete bearingstress is uniform. Bending stress in the steel should be checked assuming bending can occur across acorner of the plate or across a line parallel to its narrow edge.

See Appendix 6.4-A3 for preapproved anchorages for post-tensioning.

L. Camber

The camber to be shown on the plans should include the effect of both dead load and final prestressand may be taken as given in Table 6.1.8-1.

M. Expansion Bearing Offsets

Figure 6.4.1-6 indicates expansion bearing offsets for the partial effects of elastic shortening, creep,and shrinkage. The initial offset shown is intended to result in minimal bearing eccentricity for themajority of the life of the structure. The bearing should be designed for the full range of anticipatedmovements: ES+CR+SH+TEMP.

N. Post-Tensioning Notes

The design plans shall contain the following information for use by the post-tensioner and stateinspector: Strength of concrete in superstructure, tendon jacking sequence, friction coefficients, ducttype, elastic and time-dependent losses, anchor set, prestress forces, strand elongations, deviation of±7 percent between measured and theoretical elongations, false work construction and removal. Ifjacking is done at both ends of the bridge, the minimum strand elongation due to the specified jackingload for the end jacked first as well as the end jacked last should be indicated. When calculatingstrand elongation, use Es = 28,000 ksi. The calculated strand elongations at the ends of the bridge arecompared with the measured field values to ensure that the friction coefficients (and hence the levelsof prestressing throughout the structure) agree with the values assumed by the designer.

The tendons shall be jacked in a sequence that avoids causing overstress or tension in the bridge.

The following notes for the sequence of stressing of longitudinal tendons should be shown inthe plans:

1. The final prestressing force shall be distributed with an approximately equal amount in each weband shall be placed symmetrically about the centerline of the bridge.

2. No more than one half of the prestressing force in any web may be stressed before an equal forceis stressed in the adjacent webs. At no time during the stressing operations will more than 1/6 ofthe total prestressing force be applied eccentrically about the centerline of the structure.

Sidewalks and traffic barriers are normally cast after post-tensioning.

See Appendix 6.2-B1 for typical post-tensioning notes for plans.



July 2000 6.4-21

6.4.3 Review of Shop Plans

See also section on Review of Shop Plans in Chapter 1 of this manual as well as Section 6.2.8 of theConstruction Manual.

A. Check that the manufacturer provides a “lift off” force as required in Standard Specifications.

B. Check that the number of PT strands in a tendon proposed by the contractor do not exceed the numberallowed by the contract (i.e., 31-1/2 inch diameter or 22-0.6 in diameter).

C. Check that the allowable tendon stress at anchorages and along the tendon are not exceeded.

D. The maximum size of a post-tensioned tendon should be 31-1/2 inch strands or 22-0.6 inch strands.Use of a larger tendon requires the approval of the Bridge Design Engineer and the Design UnitSupervisor.

E. If the post-tensioning shop drawings show a PT tendon larger than the size specified in contractplans, review should mark “Not Approved” with a note indicating that “the tendon size exceeds themaximum tendon size specified in the contract plans.”

F. Temporary strands may be required for shipping, reducing camber, and lower the release strength.These strands may be pretensioned or post-tensioned and are bonded only for the end 10 feet of thegirder, or may be post-tensioned prior to lifting the girder from the form. These strands must be cutbefore the deck slab concrete is placed, and preferably after the diaphragms are cast and cured.

P65:DP/BDM6


Prestressed Concrete Superstructures Bibliography

July 2000 6.99-1

6.99 Bibliography

1. Prestressed Concrete StructuresT. Y. Lin Wiley

2. Prestressed Concrete Design and ConstructionF. Leonhardt (in WSDOT Library)

3. Prestressed Concrete Vol. I and IIGuyon Wiley

4. Designing for Effects of Creep, Shrinkage, and TemperatureACI SP 27 620.1 Design 1 1971 (WSDOT Library)

5. Post-Tensioned Bridges - Design & Construction Manual of WCRSI1499 Bayshore Highway, Burlingame, CaliforniaCopyright 1969

6. Analysis & Design of Reinforced Concrete Bridge StructuresACI Committee 443 Report 71-14ACI Journal, April 1974

7. Preapproved Repair ProceduresWSDOT Manual for Repair of Concrete

8. Post-Tensioned Box Girder Bridge ManualPost-Tensioning Institute301 West Osborn, Phoenix, Arizona

9. Cracking of Voided Post-Tensioned Concrete Bridge DecksMinistry of Transportation and CommunicationsToronto, Ontario, Canada

10. Design of Concrete Bridges for Temperature GradientsACI Journal, May 1978

11. Transportation Research Board Report No. 226 titled, Damage Evaluation and Repair Methods forPrestressed Concrete Bridge Members.

12. Transportation Research Board Report No. 280 titled, Guidelines for Evaluation and Repair ofPrestressed Concrete Bridge Members.

13. AASHTO, LRFD Bridge Design Specifications, American Association of State Highway andTransportation Officials, Washington, D.C.

14. Seguirant, S.J., “New Deep WSDOT Standard Sections Extend Spans of Prestressed ConcreteGirders,” PCI JOURNAL, V. 43, No. 4, July-August 1998, pp. 92-119.

15. PCI Bridge Design Manual, Precast/Prestressed Concrete Institute, Chicago, IL, 1997.

16. PCI Design Handbook, Precast and Prestressed Concrete, Fifth Edition, Precast/Prestressed ConcreteInstitute, Chicago, IL, 1999.

17. Mast, R.F., “Lateral Stability of Long Prestressed Concrete Beams, Part 1,” PCI JOURNAL, V. 34,No. 1, January-February 1989, pp. 34-53.


Prestressed Concrete Superstructures Bibliography

6.99-2 July 2000

18. Mast, R.F., “Lateral Stability of Long Prestressed Concrete Beams, Part 2,” PCI JOURNAL, V. 38,No. 1, January-February 1993, pp. 70-88.

19. Imper, R.R., and Laszlo, G., “Handling and Shipping of Long Span Bridge Beams,” PCI JOURNAL,V. 32, No. 6, November-December 1987, pp. 86-101.

20. Standardization of Shear Reinf. for WSDOT Standard Prestressed Girders.

21. AASHTO LRFD Specifications. Second Edition 1998.

P65:DP/BDM6


“A” Dimension forPrestressed Concrete Superstructures P.S. Concrete Bridges

July 2000 6.1-A1-1

(For Simple Span or Continuous P.S. Bridges)

Definitions:

S = Span length (ft.)L = Vertical curve length (ft.)G = Algebraic diff. in profile tangent grades (%)R = Horizontal curve radius to girder per next sheet (ft.)W = Girder top flange width (inches)m = Deck crown or super slope (ft./ft.)

Note: The following assumes that sag breaks in curb line profiles due to super transitions will occur @ Piers so asnot to require any increase “A.”

“A” Dimension (At Piers only)

Slab Thickness + 3/4″) fillet = + (Normally 81/4″)Excess Girder Camber Allowance = +

Top Flange Width Effect = W × = +

Horiz. Curve Effect = = +

Vert. Curve Effect = = {+ for Sag Vert. or - for Crown Vert.)

Round “A” to nearest 1/4″ Total “A”

(See minimums below) May make shorter span critical.

Use “A” = (Slab thickness + 3/4″) + Top Flange Width Effect) Min.Use “A” = 9″ Min. where Drain Type 5 crosses girder.

The basic attempt is to have the top of girder not higher than 3/4″ below the bottom of slab at the center of the span.This provides that the actual girder camber could exceed the calculated value by 13/4″ before the top of the girderwould start interfering with the slab steel.

Allowance for the amount the girder camber, at time of slab pour, exceeds the screed camber.

Use 2.50 @ preliminary plan stage to determine vertical clearance. Note in left margin of Layout:“A” Dimen. = “X” (not for design).

Use value from deflection program results to determine “A” Dimen. to use for design.

1

1

*

*

m2

1.5 S2m R

GS2

100L

{



6.1-A1-2 July 2000

Horizontal Curve Effect:

Vertical Curve Effect:

Algebraic difference in profile tangent grades = G (%)

Vertical curve length = L (ft)

Span Length = S (ft)

φ = × × m5,730 R

S400

H = × 0.01746 × × 12573Sm 4R

S2

tan φ = × 0.01746 tan 1°5,730Sm 400R (approx.)

1.5 × S2

RH × m (inches)

(approx.)

K = a = K × × 12 = × × 12

a = 1.5 × × S2 (inches)

100G 2L

S2

40,000 G 2L

G100 L

S2

400



July 2000 6.1-A1-3

Check for excess pad at span

For bridges which are on sharp crowned vertical curves, the pad at span can become excessive to the pointwhere the girder and diaphragm stirrups (based on the “A” dimension) are too short to bend into the properposition. This is a problem on bridges with spans in excess of 100 feet and a total grade change of 10 percenton a 900-foot vertical curve. The effect of girder cambers which are less than the calculated values tends to addto this error.

Pad at span (A = top of slab to top of girder at span)

A = A + a + C - G

where a is the vertical curve effect as calculated on Appendix 6.1-A1-1, C is the screed camber, and G is thegirder camber at the time of slab pour. A value for “G” of 1 inch less than that shown on the deflection programoutput should probably be used to accommodate the worst case of camber variation.

A correction should be made to the stirrup lengths if the value of A exceeds A by more than 2 inches.

P65:DP/BDM6

CL

CL

CL CL CL

CL

CL

July 2000 6.2-A1-1


Prestressed Concrete Superstructures W95G and W83G

Notes to Designer for Pretensioned “Deep” Standard Girders — W95G and W83G

Section Dimensions and Properties

1. Girder section dimensions and properties of the W95G and W83G are based on hard metric units as shownon the metric version of the Washington Standard Girders sheet in Appendix A. The U.S. Customary unitdimensions of the W95G and W83G are conversions from metric units.

2. Girder section dimensions and properties of other standard girders are based on U.S. Customary units asshown on the U.S. Customary version of the Washington State Girder sheet in Appendix A. Metric versionsof other standard girders are conversions from U.S. Customary units.

Design Assumptions and Requirements

1. These design assumptions and requirements apply to pretensioned girders only.

2. Design is to be in accordance with the current edition of the AASHTO LRFD Bridge Design Specifications13,and the following requirements:

• Deck thickness is to be 9 inches minimum unless a thinner deck can be justified by analysis or by thespace necessary to place the deck reinforcement with the required clearances and cover.

• Deck wearing surface is to be assumed as 1/2 inch.

• Concrete Strengths:

• Deck strength fc′ shall be 4.0 ksi (Class 4000D Concrete).

• Girder strength at transfer of pretension force fci′ shall be 3.50 ksi minimum and 7.50 ksi maximum.Girder transfer strength shall be determined by analysis (see section on girder handling), rounded upto the nearest 0.10 ksi. Transfer strengths less than or equal to 7.00 ksi can be achieved on a daily turnaround schedule. Transfer strengths between 7.00 ksi and 8.50 ksi can be achieved with extendedcuring time. For transfer strengths between 7.50 ksi and 8.50 ksi, the girders shall be designed aspretensioned, but the substructure shall be designed for the heavier post-tensioned, segmental sections(W83PTG and W95PTG) to allow for alternate bid proposals. Transfer strengths higher than 8.50 ksishall not be specified.

• Girder design strength fc′ shall be 7.00 ksi minimum and 10.00 ksi maximum. The design strengthshall be specified as the calculated maximum of 1) the required transfer strength, 2) the strengthrequired at shipping (see section on girder shipping) and, 3) the strength required in service. Themaximum calculated value shall be rounded up to the nearest 0.10 ksi. For design strengths less thanor equal to 9.00 ksi, the age at cylinder testing shall be specified at 28 days. For design strengthsbetween 9.00 ksi and 10.00 ksi, the age at cylinder testing shall be specified at 56 days. The designstrength shall not be specified higher than 10.00 ksi.

• Prestressing:

• The prestressing strand shall be 0.6 inch diameter, AASHTO M 203, 270 ksi, low-relaxation strand.

• Temporary strands in the top flange of the girder will most likely be required for shipping (see sectionon girder shipping). These strands may be pretensioned and bonded only for the end 10 feet of thegirder, or may be post-tensioned prior to lifting the girder from the form. These strands shall beconsidered in the design to reduce the required transfer strength, to provide stability during shipping,and to reduce the “A” dimension. These strands must be cut before the cast-in-place deck is placed,and preferably after the diaphragms are cast and cured.



6.2-A1-2 July 2000

• The maximum number of harped strands is 22, harped at 0.40 of the span length.

• The maximum number of straight strands is 46 in the bottom flange of the girder.

• The center to center strand spacing is 2 inches.

• The jacking stress fpi = 0.75fpu = 202.5 ksi.

• The slope of the harped strands shall not be steeper than 8 horizontal to 1 vertical.

• The harped strand exit location at the girder ends shall be held as low as possible while maintainingthe concrete stresses within allowable limits.

• Allowable Stresses:

• At Service: Tension = zero (0)Sustained compression fc = 0.45 fc′Total compression fc = 0.60 fc′

• At Release: Tension ft = (psi)Compression fci = 0.60 fci′

• For flexural strength, it has been determined14 that AASHTO LRFD Article 5.7.3 underestimates thestrength of the composite deck-girder system. The strain compatibility method given in Section 8.2.2.5 ofthe PCI Bridge Design Manual15 is recommended for this analysis. In addition to the effective area of thedeck, the top flange of the girder and the mild reinforcement in the deck and the top flange of the girdershould be included in the analysis.

• Simple spans shall be assumed for positive moment flexural design.

• The W83G and W95G girders shall not be used for bridges with skew angles that exceed 30o.

3. The W95G and W83G sections are high performance girders. They generally rely on high strength concreteto be effective for the spans expected as a single piece. Maximum girder length is based on a single pieceweight not to exceed 200 kips. The approximate range of maximum span lengths for practical minimumand maximum girder spacings are as follows:

Girder Spacing (ft) Span (ft) Girder Length (ft)*

W83G 5 – 185 (maximum)

W83G 10 155 –

W95G 5 – 172 (maximum)

W95G 10 164 –

*Design may be controlled by 200 kips maximum hauling weight.

√7.5 fc′

July 2000 6.2-A1-3



Handling

The designer shall specify the lifting device locations and the corresponding concrete transfer strength thatprovides an adequate factor of safety for lateral stability. The calculations shall conform to Article 5.2.9 of thePCI Design Handbook, Precast and Prestressed Concrete, Fifth Edition16, or other approved methods. Otherreferences14,15,17,18,19 provide the derivation of the theory and design examples. Temporary top strands may beused to improve the stability of the girder during handling, and to reduce the required concrete transfer strength.

Shipping

1. The designer shall assure that the girders can be reasonably delivered to the site as part of the preliminarydesign. The girder weight shall not exceed 200 kips. Vertical and horizontal clearances along the selecteddelivery route shall be verified.

2. The designer shall check the lateral stability of the girder during shipping14,18,19. Temporary top strands shallbe used to provide a minimum factor of safety against cracking of 1.0. In the absence of more accurateinformation on the properties of the truck, the following may be used: 1) the truck rotational spring stiffnessK

q = 41,000 kip-in./radian, 2) the height of the roll center above the road h

r = 24 in., 3) the height of the top

of the truck support above the road = 6 ft, 4) the distance from the center of truck to the center of dual tiresz

max= 36 in. and, 5) the maximum distance between truck supports = 130 ft. The maximum superelevation

along the selected route shall be used in the analysis.

Shear Reinforcement in End Region

1. The end region is considered to be about 1.5 times the depth of the girder, h, from the end of the girder.

2. The vertical reinforcement shown on the standard plans provides for the maximum bursting (splitting) demandat the end of the girder for the maximum number of straight and harped strands plus six temporary strands inthe top flange of the girder (46 + 22 high + 6 respectively). This need not be changed unless the number ofstrands is increased. Generally the maximum number of strands is limited to 68 plus 6 temporary by themaximum concrete transfer strength of 8.50 ksi. The vertical bursting (splitting) reinforcement is locatedwithin approximately h/5 from the end of the girder and closely approximates 4 percent of the appliedprestressing force at transfer (AASHTO LRFD 5.10.10).

3. Other reinforcement shown in the end region accounts for vertical shear for the span configurations above andfour (4) support conditions,

• Lifting with no reaction at the end region, i.e. lifting devices located interior from the end of the girder,

• Girder plus three intermediate diaphragms plus 20 psf supported on oak bunking block,

• Bridge reactions on elastomeric bearings introducing compression into the end region, and

• Bridge reactions at the end face of the girder (End Types C and D).

The designer shall investigate any additional vertical reinforcement for reaction forces, in the direction of theapplied shear, along the vertical end face of the girder. This applies to girder End Types C and D, where allloads are eventually transferred to the face of the hinge diaphragm or crossbeam. Adequate vertical shearreinforcing is required to take the reaction back up to the top of the girder near the diaphragm interface.



6.2-A1-4 July 2000

Shear Reinforcement Beyond End Region

1. Shear reinforcement size and spacing beyond the end region of the girder shall be determined by the designer.The variation in reinforcing demand for the entire range of span and spacing configurations is considerable.The shear reinforcement is likely to be light, or nominal, for the longest single piece spans with a narrowgirder spacing, whereas the demand will be significant well out into the span for shorter spans with widegirder spacing.

2. The minimum angle theta, θ, for calculating shear reinforcement should be 25 degrees to avoid excessivehorizontal tension demand through the bottom corner of the girder by the AASHTO LRFD modifiedcompression field theory.

Girder Sheets

1. There are four end types shown on the girder sheets. Due to the extreme depth of the W83G and W95Ggirders, and possible end of girder tilt at the piers for profile grades, the designer will need to pay particularattention to details to assure the girders will fit and perform as intended. The four end types are identifiedwith pertinent detailing dimensions as follows:

• End Type A – is for cantilever end piers with an end diaphragm cast on the end of the girders.

End Type A has a recess at the bottom of the girder near the end for an elastomeric bearing pad. Themaximum bearing pad size expected for the W95G and W83G girders is 18 inches long x 35 incheswide. The recess at the centerline of bearing is 3/4 inch deep to accommodate an elastomeric pad lengthof 18 inches. This recess is to be used for profile grades up to and including 4 percent. The recess is tobe replaced by an embedded steel plate flush with the bottom of the girder for grades over 4 percent.A tapered bearing plate, with stops at the edges to contain the elastomeric pad, can be welded or boltedto the embedded plate to provide a level bearing surface.

July 2000 6.2-A1-5



Reinforcing bars and pretensioned strands project from the end of the girder. The designer shall assurethat these bars and strands fit into the end diaphragm. Embedment of the girder end into the end dia-phragm shall be a minimum of 3 inches and a maximum of 6 inches. For girder ends where the tilt wouldexceed 6 inches of embedment, the girder ends shall be tilted to attain a plumb surface when the girder iserected to the profile grade. Embedment into the end wall shall be 3 inches.

The gap between the end diaphragm and the stem wall shall be a minimum of 21/2 inches or 1/2 inch greaterthan required for longitudinal direction.



6.2-A1-6 July 2000

• End Type B – is for “L” type abutments. End Type B also has a recess at the bottom of the girder for anelastomeric bearing pad. Notes regarding the bearing recess on End Type A also apply to End Type B.End Type B is the only end type that does not have reinforcing or strand projecting from the girder end.

Note that the centerline of the bearing is not coincident with the centerline of the diaphragm. For girderson a grade, dimensions for each bearing, P1 and P2, from the ends of the girder will be different. Typi-cally the centerline of bearing will be 1′-3″ minimum from the end of the girder to fit the bearing andprovide adequate edge distance. The designer may want to locate the diaphragm such that it is equaldistance from the centerline of the bearing, and the centerline of the bearing is equal distance from theface of the back wall of both abutments. This should create consistency in dimensions and make it easierto calculate girder lengths.

July 2000 6.2-A1-7



• End Type C – is for continuous spans and an intermediate hinge diaphragm at an intermediate pier. Thereis no bearing recess and the girder is temporarily supported on oak bunking blocks. This detail is generallyused only in low seismic areas. This end type is generally used for bridges east of the Cascade Mountains.

The designer shall check the edge distance and provide a dimension that prevents edge failure, or spalling,at the top corner of the supporting cross beam for load from the oak bunking block.



6.2-A1-8 July 2000

• End Type D – is for continuous spans fully fixed to columns at intermediate piers. There is no bearingrecess and the girder is temporarily supported on oak bunking blocks.

The designer shall check the edge distance and provide a dimension that prevents edge failure, or spalling,at the top corner of the supporting cross beam for load from the oak bunking block.

July 2000 6.2-A1-9



Summary of Checks Required by Designer

1. Shear reinforcing size and spacing beyond the end region of the girder shall be determined by the designer.It is uneconomical to provide a standard pattern to cover all span and girder spacing arrangements.

2. Determine lifting location and required concrete transfer strength to provide adequate stability duringhandling. The lifting bar location, concrete release strength, and “A” dimension should be based on six (6)temporary strands in the top flange. Generally the temporary strands provide additional stability for liftingand transportation, and reduce the camber. Less camber allows for less “A” dimension and concrete pad deadweight on the structure. Temporary strands are assumed to be cut after all intermediate diaphragms are castand cured, but before the cast-in-place deck is placed.

3. Attention to detail: Due to the extreme depth of the W83G and W95G girders, and possible tilt at the piersfor profile grades, the designer will need to pay particular attention to details to assure the girders will fit andperform as intended. Girder data required to be placed in the table on Girder Details 2 of 2 include the girderidentifiers, “A” dimension, end types, girder geometric data, and strand forces and pattern required.

4. Check edge distance of supporting cross beam.

5. For continuous bridges, design girders as simple spans for live load (Do not deduct negative moments frommaximum simple beam positive moments).

6. Provide reinforcement for negative moments at intermediate piers due to live loads and superimposed deadloads from traffic barrier, pedestrian walkway, utilities, etc.

P65:DP/BDM6


Prestressed GirderPrestressed Concrete Superstructures Intermediate Hinge Diaphragm

July 2000 6.3-A1

Notes to Designer for Prestressed Girders Intermediate Hinge Diaphragms

1. All girders in each bridge shall be of the same depth.

2. Design girders as simple span (do not deduct negative moments from maximum simple beam positivemoments).

3. Provide reinforcement for negative moments at intermediate piers due to live loads and superimposed deadloads from traffic barrier, pedestrian walkway, utilities, etc.

4. Include reinforcement on this sheet in the bar list you prepare.

5. Check hinge bars for minimum embedment in crossbeam. See hinge bar table for size when girders exceed6.0 ksi. Check hinge bar size.

Design Assumption — Saw Tooth Shear Key

Design criteria based on AASHTO LRFD { Vn = c*Acv + mu*(A uf*f y + Pc) }

1. Creep and shrinkage not considered due to simple span design

2. c = 0.100 ksi, and mu = 1.0*lambda, where lambda = 1.0 for normal weight concrete

3. Assume Pc = 0.0

4. Maximum ultimate shear stress = 0.800 ksi (on sawtooth area only)

5. fy = 60 ksi

Maximum Ultimate Shear = 1.25(DC) + 1.75 (L + IM)

W95G Vu = 629 kipsW83G Vu = 588 kipsW74G Vu = 291 kipsW58G Vu = 241 kipsW50G Vu = 215 kipsW42G Vu = 170 kips

Minimum Crossbeam Width

In order to have room for placing oak blocks with required clearances on cross-beams, the cross-beams must bedesigned with a minimum width of 4′-6″ for W95G and W83G, 4′-2″ for W74G, and 4′-0″ for all other girders.Designer is to check edge distance of oak blocks to top outside corner of cross-beam for reaction from girderweight + diaphragms + (20 psf) construction load. Adjust minimum width of cross-beam as necessary to preventcorner support failure.

P65:DP/BDM6


Prestressed Concrete Superstructures Post-Tensioning Anchorages

July 2000 6.1-B1-1

Preapproved Anchorages for Post-Tensioning

The following are the anchorages approved by the Washington State Department of Transportation (WSDOT).

(Note: The majority of these anchorages have been approved and accepted by WSDOT on the bases of tests doneby suppliers for various state and local jurisdictions outside the state of Washington.

VSL Corporation (Owned by DYWIDAG Systems International)

Anchorage Type Maximum Number of Strands

E5-31 Bearing Plate 31 1/2-inch strands


E6-22 Bearing Plate 22 0.6-inch strands





EC5-31 Casting With External and Intermediate Flange 31 1/2-inch strands




SO6-4 Casting With External Flange (for Bearing) 4 0.6-inch strands used for dock(or slab) post-tensioning

ACS-28.5 Bearing Plate 28 1/2-inch strands



C-22.5 Casting With External and Intermediate Flange 22 1/2-inch strands

Prescon Corporation (Owned by Freyssinet International)

Anchorage Type Remarks

19 KD 5 Casting With External and Intermediate Flange 19 1/2-inch strands

27 KD 5 Casting With External and Intermediate Flange 27 1/2-inch strands


Prestressed Concrete Superstructures Post-Tensioning Anchorages

AVAR Post-tensioning Systems

Anchorage Type Minimum Number of Strands

SP 12.5 Single Plane System 12 1/2-inch strands



MP 12.5 Multiple Plane System 12 1/2-inch strands

MP 22.5 Single Plane System 22 1/2-inch strands

C 12.5 Single Plane System 12 1/2-inch strands



Bar Anchorages

DYWIDAG Systems International

1-inch thread bars through 13/8 at fu of 150 ksi only.

(Note: For anchorages not shown, contact supervisor.)

P65:DP/BDM6

6.1-B1-2 July 2000


Notes to DesignersPrestressed Concrete Superstructures Post-Tensioning

July 2000 6.2-B1

Post-Tensioning Notes

1. The cast-in-place concrete in superstructure shall be Class _____. The minimum compressive strength ofthe cast-in-place concrete at the time of post-tensioning shall be _____. ksi.

2. The minimum prestressing load after seating for each web shall be _____. ksi. Each web shall have aminimum of _____ strands.

3. The design is based on _____ inch diameter low relaxation strands with a jacking load of _____ ksi each web,an anchor set of 1/4 inch, a friction curvature coefficient, m=0.20, and a friction wobble coefficient, k=0.0002.The actual anchor set used by the contractor shall be specified in the shop plans and included in the transferforce calculations.

4. The design is based on the estimated prestress loss of post-tensioned prestressing strands of _____. ksi due tosteel relaxation, elastic shortening, creep and shrinkage of concrete.

5. The contractor shall submit the stressing sequence and elongation calculations to the engineer for approval.All losses due to tendon horizontal curvature must be included in elongation calculations. The stressingsequence shall meet the following criteria:

A. The prestressing force shall be distributed with an approximately equal amount in each web and shall beplaced symmetrically about the center line of bridge.

B. No more than one-half of the prestressing force in any web may be stressed before an equal force isstressed in the adjacent webs. At no time during stressing operation will more than one-sixth of the totalprestressing force be applied eccentrically about the center line of the bridge.

6. The maximum outer diameter of the duct shall be _____ inches. The area of the duct shall be at least 21/2 timesthe net area of the prestressing steel in the duct.

7. All tendons shall be stressed from pier _____.

Note to Designers:

1. Small changes in thickness of web (up to 1 inch) shall not require redesign of structure on the part of thecontractor.

2. Commonly used stress levels in note number 1 are 3000 psi and 3500 psi.

3. Use of a tendon with more strands than the maximum noted above requires the approval of the Bridge DesignEngineer and the Design Unit Supervisor.

4. Post-tensioning shop drawings detailing a tendon with more strands than the maximum specified by thecontract shall be returned “Not Approved” with a note stating “the number of strands per tendon exceeds themaximum specified in the contract.”

P65:DP/BDM6

July 2000 6.3-B1


P.T. Box Girder BridgesPrestressed Concrete Superstructures Single Span

WidthContract Award Curb Span/ Skew

No. Name County Date Span Curb (ft.) Depth Deg. Remarks

9215 AR Line O’xing Spokane 12/71 112 38 28.9 Curved Limited available6000′R structure depth.

9150 Sunset I/C SR 2 O’xing* Spokane 8/71 150 38 21.4 52

9664 W-Line O’xing Chelan & 12/73 130 59 21.7 0 5′ sidewalk onDouglas one side.

9900 W. Snoqualmie I/C O’xing King 4/75WB 165 68 22.0 45EB 135 52 22.5 40

0839 Euclid Avenue I/C O’xing Chelan & 10/77WB Douglas 158 38 19.8 Curved

2200′REB 158 50 19.8 Curved

2200′F

0902 Allen Street I/C O’xing* Cowlitz 2/78 132 52 22.0 Curved3274′R

2156 14 E Line U’xing (N&S)* Clark 11/81 112 26 21.3 Curved625′R

*Twin bridges.



8569 Brickyard Road U’xing King 2/69 137 38 22.2 45155

9122 NE 50th Avenue U’xing Clark 7/71 124 44 24.8 12124

9122 NE 69th Avenue U’xing Clark 7/71 130 84 23.6 0130

9289 SE 232nd Street U’xing King 3/72 141 55 23.5 51133

9448 NE 18th Street U’xing Clark 1/73 138 44 22.8 17 6′ sidewalk on138 each side.

9737 Mill Plain Road I/C U’xing Clark 5/74 167 84 22.2 8 5′ sidewalk on172 each side.

0862 East Zillah I/C U’xing Yakima 10/77 178 40 23.0 44158

0862 Hudson Road U’xing Yakima 10/77 151 30 22.6 37151

1219 Johnson Road U’xing Yakima & 8/78 156 34 22.7 45Benton 161

1366 Donald Road U’xing Yakima 12/78 142 55 23.8 45155

1764 148th Avenue NE U’xing King 12/79 168 60 21.9 41157

1788 Gap Road U’xing Yakima 1/80 131 30 22.1 37131


P.T. Box Girder BridgesPrestressed Concrete Superstructures Two Span

July 2000 6.3-B2-1



2156 14-H Line U’xing Clark 11/81 114 60 22.8 0114

2156 14-D Line U’xing (North) Clark 11/81 196 26 21.8 Curbed196 600′R

2217 SR 12 U’xing Benton 2/82 147 55 23.3 0147

2217 Keene Road U’xing Benton 2/82 150 34 21.4 Curved 25′ counterweighted150 11,459′R cantilever spans at

each end. Transv. P.T.

2207 G Line U’xing Benton 4/82 162.4 Varies 20.5 0 30′ counterweighted180.6 78.6-84.6 cantilever spans at


2207 N-S Line U’xing Benton 4/82 155 38 22.1 0155

2207 SR 240 Connection U’xing Benton 4/82 163.5 72 20.4 0 25′ counterweighted(R-Line) 163.5 cantilever spans at


2236 Road 68 I/C U’xing Franklin 4/82 191 64 23.2 35191

2236 Road 100 I/C U’xing Franklin 4/82 183 55 21.5 15167

2236 SR 14 I/C U’xing (Eastbound) Franklin 4/82 170 26 22.4 Curved156 1600′R

2236 SR 14 I/C U’xing (Westbound) Franklin 4/82 159 38 21.8 Curved148 1500′R


P.T. Box Girder BridgesPrestressed Concrete Superstructures Two Span

6.3-B2-2 July 2000



8759 Kalama River Bridge Cowlitz 40 Varies 6′ sidewalkSB 2/70 200 46-53 0 on one side.

20040

40NB 2/70 200 Varies Varies 0 6′ sidewalk

200 46.5 on one side.40

888761 Valley View Road O’xing Snohomish 2/70 170 38 25.2 0

88

1909102 Columbia River Bridge Chelan & 7/71 260 74 Varies 0

at Olds** Douglas 190

100.5145

9749 Evergreen Parkway Thurston 145 26 Varies 47 Hourglass columns.114114

87.5

1609840 W Sunset Way Ramp U’xing King 12/74 159 26 22.9 Curved

100 500′R &600′R

1291193 24F Over MD Line Clark 8/78 201 26 Varies 0

129

1263794 Sen. Sam C. Guess Memorial 5/90 182 77 Varies 12 Replaced arch, built

(Division St. 2/644) 126 in two stages.

**Middle 3 spans of 7-span bridge are post-tensioned.


P.T. Box Girder BridgesPrestressed Concrete Superstructures Multiple Span

July 2000 6.3-B3-1



63.51439 SR 516 O’xing King 3/79 133 42 24.2 40

63.5

1580 Ahtanum Creek O’xing Yakima 167SB 8/79 5@172 26 25.1 Curved

167 1200′R

137NB 8/79 6@172 38 25.1 Curved

166 1200′R

1950 Yakima River Bridges Benton 10/80North Bridge 140+ Varies Varies Curved Transverse post-

161 48′-100′ 6000′R tentioning.161215147

South Bridge 140+ 38 Varies Curved Transverse post-161 5900′R tensioning.161 10′ bicycle and215 pedestrian path147 on one side.

2156 14-I Line Clark 11/81 163 38 22.2 Curved145 600′R

82

2156 14 D Line (South) Clark 11/81 128 26 24.4 Curved171 625′R128

2207 GE Line Over G Line Benton 4/82 90 38 23.5 Curved188 1400′R

90



6.3-B3-2 July 2000



2207 RA Line Over ER Line Benton 4/82 47 55 17.3 20 Transverse post-104 tentioning.

47

2245 Pearl Street O’xing Pierce 4/82 49 54 22.7 Curved159 1400′R

49

2245 6th Avenue O’xing Pierce 4/82 43 Varies 22.7 Curved125 87.4- 1400′R &

43 102 400′R

2327 Spokane River Bridge Spokane 6/82 175 76 Varies 0 Transverse post-Stage 1 255 tentioning.

175

*** Green River Bridge King 118 74 Varies 22150

99

1263794 Sen. Sam C. Guess Memorial 5/90 182 77 Varies 12 Replaced arch, built

(Division St. 2/644) 126 (depth 5.5 to in two stages.8.5 at piers)

***Not yet to contract.

P65:DP/BDM6



July 2000 6.3-B3-3

July 2000 7.0-i


Structural Steel Contents

Page

7.0 Structural Steel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.0-1.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

7.1 Design Considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.1-1.2 Girder Depth . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.3 Girder Spacing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.4 Estimating Structural Steel Weights . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2.5 Types of Steel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.6 Available Plate Sizes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.7 Girder Segment Sizes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.8 Computer Programs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.9 Fasteners . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

7.2 Girder Bridges . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.2-1.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.2 “I” Girders . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

7.3 Design “I” Girders . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.3-1.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.2 Composite Section . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.3 Flanges . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.4 Webs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.5 Transverse Intermediate Stiffeners . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.6 Longitudinal Stiffeners . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.7 Bearing Stiffeners . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.8 Crossframes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.9 Bottom Laterals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.10 Bolted Field Splice . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.11 Camber . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.12 Roadway Slab Placement Sequence . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.13 Bridge Bearings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.14 Surface Roughness . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.15 Welding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.16 Fabrication . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

7.4 Plan Details . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.4-1.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.2 Structural Steel Notes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.3 Framing Plan . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.4 Girder Elevation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.5 Typical Girder Details . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.6 Crossframe Details . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.7 Camber Curve and Bearing Stiffener Details . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.8 Roadway Slab . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.9 Safety Cable Details . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

7.5 Shop Plan Review . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.5-1

7.99 Bibliography . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.99-1

7.0-ii July 2000


Structural Steel Contents

Appendix A

7.0-A1 Steel Plate Girder Design Flow Chart7.4-A1 Girder Framing Plan and Elevation View

7.4-A2 Part Longitudinal Girder Elevation

7.4-A3 Primary Stiffeners7.4-A4 Transverse Intermediate Stiffeners

7.4-A5 Splices

7.4-A6 Optional Web Splices7.4-A7 Fillet Weld Termination Detail

7.4-A8 Field Splice Detail

7.4-A9 Drip Plate Details7.4-A10 Crossframes

7.4-A11 Crossframe Attachment Details

7.4-A12 Lateral Plate Detail7.4-A13 Camber Curve and Bearing Stiffener Camber Details

7.4-A14 Roadway Slab-Plan View

7.4-A15 Roadway Slab-Section View7.4-A16 Safety Cable Details

P65:DP/BDM7

July 2000 7.0-1


Structural Steel Structural Steel

7.0 Structural Steel

7.0.1 Introduction

The most common type of steel superstructure used on bridges in Washington State is the built-up steel“I” girder. Rolled beams have been used on a very limited basis but much of the following is applicable.Because of their uniqueness and limited application, other types of steel superstructures (box girders,trusses, arches, suspension, etc.) are not addressed.

Use English units for all widening and rehabilitation on existing English designed and detailed steelbridge projects. Metric units are acceptable for new previously designed steel bridge projects.

P65:DP/BDM7

July 2000 7.1-1


Structural Steel Design Considerations

7.1 Design Considerations

7.1.1 General

Use the Strength Design Method Load Factor Design of Section 10 Structural Steel of AASHTOStandard Specifications for Highway Bridges to design steel girders. Bridges on horizontal curves shallalso meet the requirements of the AASHTO Guide Specifications for Horizontally Curved HighwayBridges, as applicable. The information provided in this chapter is intended to help apply these AASHTOspecifications and to define office practice.

Typical construction is nonshored steel girders acting compositely with a reinforced concrete roadwayslab. This is discussed in more detail in Section 7.3.2. Since plate stock of M 270 grade 50W and M 270grade 50 are close in price, office practice is to specify grade 50W for plate girders.

The use of nonredundant load path structures should be avoided. Nonredundant loadpath structures arestructures where the failure of a single load carrying member, or a component thereof, could cause a totalcollapse. An example would be a twin plate girder structure.

Nonredundant structures are generally not used because of the extensive ongoing annual maintenanceinspections required by FHWA. Also, nonredundant structures increase fabrication costs and requiregreater attention to detail during design. Even so, the use of nonredundant structures may be approvedby the Bridge Design Engineer, however, approval shall be obtained by the designer prior to beginningthe design.

Steel girder bridges typically require a paint system to provide protection against corrosion. The paintsystem for girder bridges is defined in the Special Provisions and is a three-part system. The first coat isan inorganic zinc shop primer. This is a sacrificial protection system. The second coat is an epoxy sealnormally applied after the slab has been placed. This is a barrier protective system but in combinationwith the zinc primer, is considered a composite protective system. The third and final coat is a urethanewhich protects the epoxy from UV attack and provides color for the bridge. The color is specified in theSpecial Provisions. This paint system will normally require repainting in approximately 30 years.

Unpainted weathering steel should be considered for locations deemed appropriate. See NCHRP Report314. Approval for its use must be obtained from the Bridge Design Engineer. Careful attention to detailsis required for proper weathering. Accumulation of debris, staining of substructure, and water fromexpansion joints can pose considerable problems and add to life cycle costs. Provisions to sand blasterected steel and apply controlled wet-dry cycles are required to produce a sound protective coating withgood appearance. Recommendations for using weathering steel are contained in Uncoated WeatheringSteel Bridges, Vol. I, Chapter 9 of AISC’s Highway Structures Design Handbook. A more comprehensivetreatment is found in NCHRP Report 314 Guidelines for the Use of Weathering Steel in Bridges. Surfacesto be embedded in concrete, such as top flanges, should be shop painted.

7.1.2 Girder Depth

The superstructure depth is initially determined during preliminary plan development and is based uponthe span/depth ratios provided in Chapter 2 of this manual. The designer will have to verify this depth bymeeting live load deflection requirements and by meeting stress requirements. It is office practice to limitlive load deflections to L/800 for HS-25 or L/1000 for HS-20. Live load deflection is calculated on a perbridge basis with reduction for multiple lanes.

The superstructure depth is typically the distance from the top of the concrete roadway slab to the bottomof the web. This distance is in multiples of 6 inches for shorter span bridges, and 1 foot 0 inches forlonger span bridges, and should be consistent throughout the length of the bridge.

7.1-2 July 2000



Other features such as notching at hinges (combined with notching for expansion joint system), verticalclearances, etc., should be considered in selecting the superstructure depth.

7.1.3 Girder Spacing

For simplicity of design, girders should be spaced such that each is designed for the same load; that isbasically, girders will be identical. Spacing should be such that slab dead load is equally distributed onall girders and the distribution of wheel loads on the exterior girder is close to that of the interior girder.Barrier weights shall be equally distributed to a maximum of two “I” girders. The least number of girdersshould be used that is consistent with a reasonable deck design.

In general, live load distribution to girders shall be in accordance with AASHTO Section 3, Part C for“I” girders. When these bounds are exceeded, a rational live load distribution method should be used.

7.1.4 Estimating Structural Steel Weights

For the preliminary quantities or preliminary girder design, an estimate of steel weights for built-up platecomposite “I” girders can be obtained from Figures 7.1.4-1 through 7.1.4-3. These figures are based uponprevious designs with HS-20 live loads with no distinction between service load designs and load factordesigns. These charts provide a good double check on final quantities.

The weights shown include webs, flanges, and all secondary members (web stiffeners, diaphragms,crossframe, lateral systems, gusset plates) plus a small allowance (usually 5 percent or less) for weldmetal, bolts, and shear connectors.

7.1.5 Types of Steel

The most common types of steel used for bridges are now grouped in ASTM A 709 or AASHTO M 270specifications. The following table shows equivalent designations. Grades of steel are based on minimumyield points.

ASTM ASTM A 709 AASHTO AASHTO M 270

A 36 Grade 36 M 183 Grade 36A 572 gr 50 Grade 50 M 223 gr 50 Grade 50A 588 Grade 50W M 222 Grade 50WA 852 Grade 70W M 313 Grade 70WA 514 Grade 100 M 244 Grade 100

Grade l00W Grade l00W

Plates and rolled sections are available is these specifications and grades. Rolled sections include beams(W, S, and M shapes), H-piles, tees, channels, and angles. These materials are prequalified under theBridge Welding Code.

Use AASHTO M 270 grade 50W for plate girders. The fabricated costs of structural carbon and structurallow alloy steel plate girders are about equal. The use of M 270 grade 100, 100W requires approval by theBridge Design Engineer.

Availability of weathering steel can be a problem for some sections. For example, steel suppliers do notstock angles or channels in weathering steel. Weathering steel wide flange and tee sections are availablebut difficult to locate. Also, AASHTO M 270 steels are not stocked by local suppliers. The use of M 270steel should be restricted to large quantities such as found in typical plate girder projects.

July 2000 7.1-3



Structural tubes and pipes are covered by other specifications. See Table 1-4 of AISC Manual of SteelConstruction for selection and availability. These materials are not considered prequalified under theBridge Welding Code. They are covered under the Structural Welding Code AWS D1.1. Structuraltubing ASTM A 500 is not recommended for dynamic loading applications.

7.1.6 Available Plate Sizes

Readily available lengths and thicknesses of steel plates should be used to minimize costs. Tables ofstandard plate sizes have been published by various steel mills and should be used for guidance. Thesetables are available through the steel specialist.

In general, an individual plate should not exceed 14 feet in width, including camber requirements, or alength of about 60 feet. If either or both of these dimensions are exceeded, a butt splice is required andshould be shown or specified on the plans.

Plate thicknesses of less than 5/16 inches should not be used for bridge applications.

7.1.7 Girder Segment Sizes

Locate bolted field splices so that individual girder segments can be handled, shipped, and erectedwithout imposing unreasonable requirements on the contractor. Crane limitations need to be consideredin congested areas near traffic or buildings. Transportation route options between the girder fabricatorand the bridge site can effect the size and weight of girder sections allowed. The region should helpdetermine the possible routes, and the restrictions they impose, during preliminary planning or early inthe design phase.

“I” girder segment lengths should be limited to 150 feet depending upon their cross section. Weight isseldom a controlling factor. However, 40 tons is a practical limit for some fabricators. Long, slendersegments can be difficult to handle and ship due to their flexibility. Horizontal curvature of girdersegments may increase handling and shipping concerns.

Consider the structure’s span length and the above factors when determining girder segment lengths.

7.1.8 Computer Programs

The designer should consult the design supervisor to determine the computer program currently beingused for analyses. Instruction manuals for the programs are available in the Bridge Office ComputerSection.

Office practice and good engineering principles require that the results of any computer program shouldbe independently verified for accuracy. Verification is necessary to identify input errors which renderserroneous output. Also, programs with built-in code checks must be checked for default settings. Defaultsettings may reflect old code or office practice may supercede the code that the program was written for.

7.1-4 July 2000



7.1.9 Fasteners

All bolted connections shall be friction type. Design is based on Class B coating on fraying surfaces.The term “slip critical” implies a friction type connection.

Properties of High-Strength Bolts

Tensile YieldStrength Strength

Material Bolt Diameter ksi ksi

AASHTO M 164 1/2 - 1″ inc. 120 92(ASTM A325) 11/8 - 1″ inc. 105 81

Over 11/2″ Not Available

ASTM A 449 1/4″ - 1″ inc. 120 92(No AASHTO 11/8 - 11/2″ inc. 105 81equivalent) 13/4″ -3″ inc. 90 58

Over 3″ Not Available

AASHTO M 314 1/4″ - 3″ inc. 125-150 105ASTM F 1554Grade 105

AASHTO M253 1/2″ - 11/2″ inc. 150-170 130(ASTM A 490)

Over 11/2″ Not Available

ASTM A 354 1/2 - 21/2″ inc. 150 130Grade BD(No AASHTO 3″ - 4″ inc. 140 115equivalent)

Over 4″ Not Available

July 2000 7.1-5



General Guidelines for Steel Bolts

1. M 164 (A325) High strength, headed structural steel bolts for use in structural joints. Suitableheavy hex nuts and plain hardened washers are covered by this specification.These bolts may be hot-dip galvanized. Do not specify for anchor bolts.

2. A449 High strength steel bolts and studs for general applications including anchorbolts. Recommended for use as anchor bolts where strengths equivalent toA325 bolts are desired. These bolts may be hot-dip galvanized.

3. M 314 (F1554) Grade 105 — Higher strength anchor bolts to be used for larger sizes (11/2″ to3″). These bolts are not covered in the Standard Specifications so they requirecoverage in the Special Provisions when called for.

4. M 253 (A490) High strength alloy steel headed bolts for use in structural joints. Thesebolts should not be galvanized, because of the high susceptibility to hydrogenembrittlement. In lieu of galvanizing, the application of two or three coatsof an approved zinc rich paint may be specified. Suitable heavy hex nuts andplain hardened washers are covered by this specification. Do not specify foranchor bolts.

5. A354 Grade BD — high strength alloy steel bolts and studs. These bolts are suitablefor use as anchor bolts where strengths equal to A490 bolts are desired. Nutsand washers are covered by this specification.

These bolts should be treated in the same manner as A490 bolts in regardto galvanizing.

7.1-6 July 2000



Co

mp

osi

te W

eld

ed

Ste

el P

late

“I”

Gir

de

r —

Sim

ple

Sp

an

Fig

ure

7.1

.4-1

July 2000 7.1-7



Co

mp

osi

te W

eld

ed

Ste

el P

late

“I”

Gir

de

r —

Tw

o C

on

tinu

ou

s S

pa

ns

Fig

ure

7.1

.4-2

7.1-8 July 2000



Co

mp

osi

te W

eld

ed

Ste

el P

late

“I”

Gir

de

r —

Th

ree

or

Mo

re C

on

tinu

ou

s S

pa

ns

Fig

ure

7.1

.4-3

July 2000 7.1-9



Equivalent ASTM and AASHTO Specifications

ASTM Designations AASHTO Designations ASTM Designations AASHTO Designations

A 6/A 6M............................................ M 160/M 160M A 500 ...................................................... No Equivalent

A 27/A 27M ....................................... M 103/M 103M A 501 ...................................................... No Equivalent

A 36/A 36M ....................................... M 183/M 183M A 502 ...................................................... No Equivalent

A 48 ................................................................... M 105 A 514/A 514M .................................... M 244/M 244M

A 53 ...................................................... No Equivalent A 525 ...................................................... No Equivalent

A 108 ................................................................. M 169 A 525M .................................................. No Equivalent

A 109 .................................................... No Equivalent A 536 ...................................................... No Equivalent

A 109M................................................. No Equivalent A 563 ...................................................................M 291

A 123 ................................................................. M 111 A 563M ........................................................... M 291M

A 153 ................................................................. M 232 A 572/A 572M .................................... M 223/M 223M

A 252 .................................................... No Equivalent A 588/A 588M .................................... M 222/M 222M

A 307 .................................................... No Equivalent A 618 ...................................................... No Equivalent

A 325 ................................................................. M 164 A 668 ...................................................................M 102

A 325M.......................................................... M 164M A 673/A 673M .......................................T 243/T 243M

A 328/A 328M ................................... M 202/M 202M A 709/A 709M .................................... M 270/M 270M

A 354 .................................................... No Equivalent A 852/A 852M .................................... M 313/M 313M

A 370 .................................................................. T 244 A 898/A 898M .......................................No Equivalent

A 435/A 435M ..................................... No Equivalent B 695 ...................................................................M 298

A 446/A 446M ..................................... No Equivalent F436 ....................................................................M 293

A 449 .................................................... No Equivalent F436M ....................................................No Equivalent

A 486/A 486M ................................... M 192/M 192M F606 ....................................................... No Equivalent

A 490 ................................................................. M 253 F 606M ................................................... No Equivalent

A 490M.......................................................... M 253M F 959M ...................................................No Equivalent

F 1554 ................................................................. M 314

Figure 7.1.5-1

July 2000 7.2-1


Structural Steel Girder Bridges

7.2 Girder Bridges

7.2.1 General

Once the material of choice, steel has been eclipsed by concrete. Numerous graphs and charts areavailable to demonstrate the falling percentage of steel bridges and the rising percentage of concretebridges being constructed. Corrosion and fatigue cracking have contributed to unanticipated life cyclecosts. Fabrication and material costs have also contributed to steel’s relative cost disadvantage. Thesetrends may be compensated for by simplification of fabrication details, elimination of expansion jointsand hinges, and the lowering of steel prices due to the advent of mills that recycle scrap iron.

The specifications allow a combination of plastic design in positive moment regions and elastic designin negative moment regions. Plate girders, of the depths typically built in this state, have traditionallybeen designed to elastic limits or lower. Newer design methods may help reduce steel weight and narrowthe cost gap between steel and concrete bridges. Steel girders can also be shallower than the same spanprestressed girders.

7.2.2 “I” Girders

As stated in the introduction, welded plate “I” girders constitute the majority of steel girders designed byWSDOT. The “I” girder represents an efficient use of material for maximizing stiffness. Its shortcomingis inefficiency in resisting shear. Office practice is to maintain constant web thickness for short to mediumspan girders. Weight savings is achieved by minimizing the number of webs used for a given bridge. Thisalso helps minimize fabrication, handling, and painting costs. Current office practice is to use a minimumof three girders to provide redundant load path structures. Two girder superstructures are considerednon-redundant and hence, fracture critical.

Steel plate girder design is complicated by buckling behavior of relatively thin elements. Most strengthcalculations involve buckling in some form. Either a minimum thickness condition must be met to achievea given stress state, or strength is reduced by some amount to account for buckling. Buckling can be aproblem in flanges as well as webs if compression is present. Also, stability needs to be insured for allstages of construction, with or without a roadway deck. The art of designing these girders is to minimizematerial and fabrication expense while ensuring adequate strength and stiffness.

“I” girders are an excellent shape for welding. All welds for the main components are easily accessibleand visible for welding and inspection. The plates are oriented in line with the rolling direction so as tomake good use of strength, ductility, and toughness of the structural steel. The web is attached to the topand bottom flanges with continuous fillet welds. Usually, they are made with automatic submerged arcwelders. These welds are loaded parallel to the longitudinal axis and resist horizontal shear between theflanges and web. Minimum size welds based on plate thickness controls design in most cases. The flangesand webs are fabricated to full segment length with full penetration groove welds. These welds areinspected by ultrasound (UT) 100 percent. Tension welds, as designated in the plans, are also radio-graphed (RT) 100 percent. Office practice is to have flanges and webs fabricated full length before theyare welded into the “I” shape. Weld splicing built-up sections results in poor fatigue strength and zonesthat are difficult or impossible to inspect.

P65:DP/BDM7

July 2000 7.3-1


Structural Steel Design “I” Girders

7.3 Design “I” Girders

7.3.1 General

Composite girders may be used for continuous and simple spans. As mentioned in Section 7.1.1, officepractice is to use nonshored girders. The girder section must carry the weight of the fluid (wet) concretedeck as well as its own dead load. After the concrete has cured, the composite section becomes effectivein carrying all superimposed loads. Shear connectors are provided over the full length of the top flange ofthe structure or continuous portions of the structure. The stiffness analysis is performed for superimposeddead loads and live load plus impact, assuming the section acts compositely over the total length of thestructure or continuous portion thereof.

The fatigue truck shall be HS-20 for LFD design. When designing by the LRFD method, the fatigue truckshall be applied without neglecting axles that do not contribute to the extreme force effect. Assume Case Iroad type when determining the number of stress cycles for design.

7.3.2 Composite Section

Short-term primary loading live load plus impact is applied to the composite section transformed usingES/EC, commonly denoted n. Long-term loading (dead load of barriers, signs, luminaries, overlays, etc.)is applied to the composite section transformed using 3 ES/EC. The moments resulting from the stiffnessanalysis are applied to the composite section in the positive moment region.

The negative moments from the analysis are applied to the steel girder section including longitudinalreinforcing (negative moment composite section).

Longitudinal reinforcing steel shall be used in negative moment regions of composite, continuous spans.Refer to AASHTO Section 10.38.4.3.

7.3.3 Flanges

When determining girder section at locations of maximum positive and negative moment, try to use aconstant top and bottom flange width throughout the length of the bridge. If a width change in the topflange is necessary, it is best made at a field splice. The cross sectional areas of the top and bottom flangesmay be varied by changing thickness. Generally two changes in girder section located within the negativemoment region, one each side of maximum moment and between field splices, will be most economical.Flange thickness changes at field splices are easily accomplished. One girder section change in end spansbetween maximum positive moment and end bearing may be justified.

As a general rule, a welded splice may be justified if more than 500 pounds of steel can be saved.

7.3.4 Webs

Maintain constant web thickness throughout the structure. Except for extremely deep superstructures,maintain webs full depth without longitudinal splices. Vertical web splices for girders should be shown onthe plans in an elevation view with additional splices made optional to the fabricator. All welded websplices on exterior faces of exterior girders and in tension zones elsewhere shall be ground smooth. Likesplices on interior girders need not be ground in compression zones.

7.3.5 Transverse Intermediate Stiffeners

These stiffeners shall be used in pairs at crossframe locations on interior girders and on the inside of websof exterior girders. They shall be welded to the top flange, bottom flange and web at these locations. Thisdetail is considered fatigue stress category C. Stiffeners used between crossframes shall be located on one

7.3-2 July 2000



side of the web, welded to the compression flange, and cut short of the tension flange. Stiffeners locatedbetween crossframes in regions of stress reversal shall be welded to one side of the web and cut short ofboth flanges. Alternatively, they may be welded to both flanges if fatigue Category C is checked.

7.3.6 Longitudinal Stiffeners

On long spans where web depths exceed 12 feet, comparative web evaluations shall be made to determinewhether the use of longitudinal stiffeners will be more economical. Fabrication costs indicate the use oflongitudinal stiffeners is not economical on webs 12 feet deep or less.

7.3.7 Bearing Stiffeners

Stiffeners are required at all bearings to enable the reaction to be transmitted from the web to the bearing.These stiffeners are designated as columns, therefore, must be vertical under total dead load. The connec-tion of the bearing stiffener to the girder consists of full penetration groove welds to the bottom flange andfillet welding to the top flange and web. These connection details limit the design stress to Category C forall girder sections at points of maximum negative moment.

In the case of severe horizontal curvature on structures where girders and crossframes are subjected tolarge transverse forces resulting in considerable lateral flange bending, full penetration welds at top andbottom flanges may be necessary. Full penetration welds are expensive and should be used only wherenecessary.

7.3.8 Crossframes

The primary function of intermediate crossframes is to distribute vertical loads transversely and givetorsional rigidity to the superstructure. Together with the bottom laterals they stabilize the superstructureduring erection, pouring, and curing of the roadway slab. On curved bridges, the crossframes also resistlateral flange bending. Pier crossframes are subjected to lateral loads that originate primarily from wind,earthquake, and curvature and are transmitted from the roadway slab to the bearings.

Crossframes are generally patterned as K-frames or as X-frames. Typically the configuration selected isbased on the most efficient geometry. The members should closely approach a slope of 1:1 or 45°. Avoidconflicts with utilities passing through the girders.

On K-frames like the following, avoid connection congestion at bottom laterals:

K-frames like the following may be better for utilities, however, create some congestion at the bottomlateral connection:

July 2000 7.3-3



X-frames like the following, where girder depth approaches girder spacing, are more efficientgeometrically:

Intermediate crossframes for straight girders with little or no skew should be designed as secondary

members. Choose a section which satisfies kL

r ≤ 140 and design connections only for anticipated loads,

not for 75 percent strength of member. This should result in greater economy but still meet the intent of

AASHTO specifications.

In general, crossframes should be installed parallel to piers for skew angles of 0° to 10°. For greater skewangles, other arrangements may be used. Consult with the design unit supervisor or the steel specialist forspecial requirements.

Intermediate crossframes for curved I-girders require special consideration. Curved girder systems shouldbe designed according to AASHTO “Guide Specifications for Horizontally Curved Highway Bridges.”Use Table 1.4A of the guide specifications to distinguish between straight and curved girders.

Crossframes at piers must be designed to transmit transverse loads due to wind or earthquake from theroadway slab to the bearings or transverse stops. Design and detail pier crossframes separately fromintermediate crossframes.

Bolted connections for crossframes are favored because they allow adjustment during fit up and erection.

Connections of crossframes to web stiffeners require careful attention to detailing to minimize fabricationdifficulties and most importantly increase fatigue resistance. Web stiffeners at crossframes shall bewelded to top and bottom flanges. This practice minimizes out-of-plane bending of the girder web.The resulting detail must be checked for Category C stress range.

7.3.9 Bottom Laterals

The primary function of a bottom lateral system is to stabilize the girders against lateral loads before thedeck hardens and stabilize the steel portion of the superstructure while the roadway slab is placed.

On straight bridges, office practice is to design the diagonal members in bottom laterals as secondarymembers. X-framing may be designed in tension only. K-framing must be designed as compression andtension members. One hundred fifty percent of the allowable service load design stress is permitted in thelaterals for the temporary construction condition. Consult AASHTO for further guidance. Determine onesize of diagonal member to be used throughout the structure. Partial loading (total panels less one-half ofthe end panel) yields maximum shear in the end panel.

Also, on curved structures, the bottom laterals are effective in resisting live load plus impact therebybecoming primary members and must be modeled in the structure to determine the actual forces themembers experience.

Lateral patterns are formed depending on number of girder lines, girder spacing, and crossframespacing. Cost considerations should include geometry, repetition, number, and size of connections.See Figure 5.1.2-1. Consideration should be given to limiting bottom laterals to one or two bays onstraight bridges.

7.3-4 July 2000



Examples of Lateral BracingFigure 7.3.9-1

July 2000 7.3-5



Note: Where lateral gusset plates are welded to girder webs, the design stress level in the girder, at theweb, is governed by the Category E detail.

For widening projects, bottom laterals are not needed since new can be braced against existing construc-tion. Framing which is adequately braced should not require bottom laterals.

7.3.10 Bolted Field Splice

Office practice is to use bolted field splices. Splices are usually located at the dead load inflection point tominimize the design bending moment. The latest USS Highway Structures Design Handbook should beconsulted for examples of splice designs. See AASHTO Section 10.18 for splice design requirements.

Splices should be designed for the greater of:

1. 75 percent of the moment capacity of the smaller section.

2. The average of the required moment due to factored loads and the moment capacity of the smallersection.

Web splice bolts are designed to resist a shear force due to:

1. Total factored shear force plus;

2. Shear force due to moment resulting from the above shear force times the eccentricity of the distancesfrom the centerline of the splice to the center of gravity of the bolt group on one side of the centerlineof the splice plus;

3. Shear force due to the portion of the design moment resisted by the web, which is:

I

IWEB

SECTION

× design moment at centerline of splice

The outer most bolt in the bolt group is the most highly stressed. The shear force can be determined byusing the “elastic moment of inertia” method.

The flange splice is designed to resist the portion of the design moment not resisted by the web.

Split splice plates are used at the bottom of the bottom flange to allow moisture to pass through the splice.

Fill plates are used to maintain constant flange splice plate thickness across the splice.

Allow fabricators to use steel sheet (ASTM A 715) for fill plates less than 14 inch thick.

Fill plates are not subject to tension and therefore a charpy V-notch toughness test should not be requiredfor them. Mark splice plates that carry tensile stress.

Allow fill plates to be fabricated from AASHTO M183, if steel is painted.

7.3.11 Camber

Permanent girder deflections shall be shown in the contract plans in the form of camber diagrams.The traditional format for detailing these diagrams should be adhered to for the benefit of construction.Camber curves are used by shop plan detailers, girder fabricators at the shop assembly stage, girdererectors, and field personnel. Most, if not all, phases of girder fabrication and erection involve potentialsources of error in camber. Also, the Standard Specifications provide for adjustments at the time of slabforming. Therefore, the slab design should reflect the possibility of reduced slab depths.

7.3-6 July 2000



Girder camber is accomplished at three stages of construction. First, girder webs are cut from plates sothat the completed girder segment will assume the shape of camber superimposed on profile grade. Thefabricated girder segment will incorporate the as-cut web shape and some degree of welding distortion.Next, the girder segments are brought together for shop assembly. Field splices are drilled as the segmentsare placed in position to fit profile grade plus total dead load camber. Finally, the segments are erected,sometimes with supports at field splices. There may be slight angle changes at field splices, resulting inaltered girder profiles. Errors at mid-span can be between one to two inches at this stage.

The following is a general outline for calculating camber and is based on girders having shear studs thefull length of the bridge.

Two curves will be required, one for total dead load plus slab shrinkage and one for girder self-weight(steel only).

Girder dead load deflection is determined by using various computer programs. Girder self-weight isassumed to include the basic section plus stiffeners, crossframes, welds, shear studs, etc. These itemsmay be accounted for by adding an appropriate percentage of basic section weight. Fifteen percent oftotal girder weight, distributed evenly along the bridge, should suffice. This loading is applied to thesteel section only.

Total dead load camber shall consist of:

1. Steel weight.2. Slab weight.3. Traffic barriers and overlays.4. Slab shrinkage.

Slab dead load deflection will require the designer to exercise some judgment concerning degree ofanalysis. A two-span bridge of regular proportions, for example, should not require a rigorous analysis.The slab may be assumed to act instantaneously on the steel section only. Therefore, the calculation wouldbe performed as above. For long structures, unusual girder arrangements, and especially structures withhinges, an analysis coupled with a slab pour sequence may be justified. This would require an incrementalanalysis where previous slab pours are treated as composite sections and successive slab pours are addedon noncomposite sections. Each slab pour requires a separate deflection analysis. The total effect of slabconstruction is the superposition of each slab pour. A note must accompany the camber diagram explain-ing the relation between camber and the slab pour sequence. The contractor should be required to submita new camber diagram if a different slab pour sequence is proposed.

Traffic barriers, overlays, and other items constructed after the slab pour should be analyzed as if appliedto a composite section full length of the bridge. The modulus of elasticity of the slab concrete should bereduced to one third of its short term value. For example, if f′c = 5000 psi, then use a value of n = 21.

Slab shrinkage has a varying degree of effect on superstructure deflections. Again, the designer must usesome judgment in evaluating this effect on camber. Slab shrinkage should be the smallest portion of thetotal camber (approximately 20 percent).

In addition to girder deflections, show girder rotations at bearing stiffeners. This will allow shop plandetailers to compensate for rotations so that bearing stiffeners will be vertical in their final position.

Camber tolerance is governed by the Bridge Widening Code AWS D1.5. A note of clarification is addedto the plan camber diagram: “For the purpose of measuring camber tolerance during shop assembly,assume top flanges are embedded in concrete without a designed haunch.” This allows a high or lowdeviation from the theoretical curve. In the past, no negative camber tolerance was allowed.

July 2000 7.3-7



7.3.12 Roadway Slab Placement Sequence

The roadway slab is placed in a prescribed sequence allowing the concrete in each sequence to shrinkfreely. This minimizes cracking of the slab due to shrinkage. Furthermore, placing the slab sequentiallyallows the contractor to place manageable volumes of concrete at a time.

For the first sequence, concrete is placed on the dead load positive moment region of end spans and in thepositive moment regions of alternate interior spans.

For the second sequence, concrete is placed on the dead load positive moment region of the remainingspans after the concrete in the first sequence has attained a minimum specified tensile strength. Checktensile stresses in the first sequence slab pour due to the second sequence slab pour.

For the third sequence, concrete is placed on the dead load negative moment region over each interiorpier. Generally, slab placement in negative moment regions does not cause cracking in previously placedconcrete.

7.3.13 Bridge Bearings

Office practice and design criteria for bridge bearings can be found in Chapter 8 of this manual.

7.3.14 Surface Roughness

The standard measure of surface roughness is the microinch value. It is specified by the symbol xxx andshall be shown on the plans for all surfaces for which machining is required unless covered by theStandard Specifications or Special Provisions. When used, this symbol means that the average value ofthe depth of the surface grooves shall not exceed xxx millionths of an inch. The lower the number (xxx),the smoother the surface.

Following is a brief description of some finishes:

500 A rough surface finish typical of “as rolled” sections. Suitable for surfaces that do notcontact other parts and for bearing plates on sheet lead or grout.

250 A fairly smooth surface. Suitable for connections and surfaces not in moving contactwith other surfaces. This finish is typical of ground edges in tension zones of flanges.

125 A fine machine finish resulting from careful machine work using high speeds and takinglight cuts. It may be produced by all methods of direct machining under proper condi-tions. Suitable for steel to steel bearing or rotational surfaces including rockers and pins.

63 A smooth machine finish suitable for high stress steel to steel bearing surfaces includingroller bearings on bed plates.

32 An extremely fine machine finish suitable for steel sliding parts. This surface isgenerally produced by grinding.

16 A very smooth, very fine surface only used on high stress sliding bearings. This surfaceis generally produced by polishing.

For examples, see Figure 7.3.14.

For stainless steel sliding surfaces, specify a #8 mirror finish. This is a different methodof measurement and reflects industry standards for polishing. No units are implied.

7.3-8 July 2000



Surface Finish ExamplesFigure 7.3.14

July 2000 7.3-9



7.3.15 Welding

All structural steel and rebar welding shall be in accordance with the WSDOT Standard Specifications,amendments thereto and the special provisions. The Standard Specifications currently calls for weldingstructural steel according to the AASHTO/AWS D1.5-96 Bridge Welding Code (BWC) and the latestedition of the AWS D1.1 Structural Weld Code. The designers should be especially aware of currentamendments to the following sections of the Standard Specifications, 6-03.3(25) Welding and RepairWelding and 6-03.3(25)A Welding Inspection.

Exceptions to both codes and additional requirements are shown in the Standard Specifications and thespecial provisions.

Standard symbols for welding, brazing, and nondestructive examination can be found in theANSI/AWS A 2.4 by that name. This publication is a very good reference for definitions ofabbreviations and acronyms related to welding.

The designer must consider the limits of allowable fatigue stress, specified for the various welds used toconnect the main load carrying members of a steel structure. See Chapter 10 of AASHTO.

The minimum fillet weld size shall be as shown in the following table. Weld size is determined by thethicker of the two parts joined unless a larger size is required by calculated stress. The weld size need notexceed the thickness of the thinner part joined.

Base Metal Thickness of Minimum Size ofThicker Part Joined Fillet Weld

Inches (mm) Inches (mm)

To 34 (20 mm) inclusive 1

4 (6 mm)

Over 34 (20 mm) 5

16 (8 mm)

The minimum size seal weld shall be 316 inch (5 mm) fillet weld.

In general, the maximum size fillet weld which may be made with a single pass is 516 inch for submerged

arc, gas metal arc, and flux-cored arc welding processes. The maximum size fillet weld made in a singlepass is 1 4 inch for the shield metal arc welding process.

The major difference between AWS D1.1 and D1.5 is the welding process qualification. The only processdeemed prequalified in D1.5 is shielded metal arc. All others must be qualified by test. Qualification ofM 270 grade 50W (A709 grade 50W) in Section 5 of D1.5 qualifies the welding of all AASHTO approvedsteels with a minimum specified yield of 50 Ksi or less. Bridge fabricators generally qualify to M 270grade 50W (A709 grade 50W).

All welding procedure specifications (WPS) submitted for approval must be accompanied by a procedurequalification record (PQR), a record of test specimens examination and approval except for SMAWprequalified. Some handy reference aids in checking WPS in addition to PQR are:

Matching filler metal requirements are found in BWC Section 4.

Prequalified joints are found in BWC Section 2.

AWS electrode specifications and classifications are obtained from the structural steel specialist.

Lincoln Electric Arc Welding Handbook.

Many of Lincoln Electric’s published materials and literature are available through those designers andsupervisors who have attended their seminars.

7.3-10 July 2000



WSDOT Standard Specifications for preheat and Interpass temperatures.

Notes: Electrogas and electroslag welding processes are not allowed in WSDOT work. Narrow gapimproved electroslag welding will be allowed on a case-by-case basis.

Often in the rehabilitation of existing steel structures, it is desirable to weld, in some form, to the inplacestructural steel. Often it is not possible to determine from the contract documents for the structure whetheror not the existing steel is weldable. WSDOT fabrication inspectors in the Northwest Region contract witha company which can make that determination economically. Coupons from the steel must be furnishedfor a spectrographic examination. Contact these inspectors to verify that the service is still availablebefore making preparations.

7.3.16 Fabrication

In most cases, a one girder line progressive longitudinal shop assembly is sufficient to assure proper fit ofsubsections, field splices, and crossframe connections, etc., in the field. Due to geometric complexity ofsome structures, progressive transverse assembly, in combination with progressive longitudinal assemblymay be desirable. The designer shall consult with the supervisor and the steel specialist to determine theextent of shop assembly and clarification of the Standard Specifications. The desired method of assemblyshown in the Standard Specifications will then be required in the special provisions.

P65:DP/BDM7

August 1998 7.4-1


Structural Steel Plan Details

7.4 Plan Details

7.4.1 General

Detailing practice should follow industry standards. Designations for structural steel can be found inTable 2-1 of AISC Detailing for Steel Construction. Old plans are a good reference for traditionaldetailing practices. Radical or even modest changes in detailing practice can result in misinterpretationof plans. Innovation is best reserved for content, not presentation of steel detailing.

Actual details for plate girders are continually being revised or improved. Cost benefits for individualdetails vary from shop to shop and even from time to time. For these reasons, previous plan details canbe guides but should not be considered standards.

In general, office practice is to favor field bolted as opposed to field welded connections. In addition,members of cross frames are shop bolted to give some degree of field adjustment. Welded assembliestend to be less adjustable when it comes time to install them.

7.4.2 Structural Steel Notes

Due to their dynamic nature, the structural steel notes are not shown in this manual. The designer’sattention is directed to the Bridge and Structures Office Book of Knowledge (BOK) which contains themost current version of the structural steel notes in their entirety. These notes must be edited based onthe requirements unique to each project and additions and deletions made accordingly.

7.4.3 Framing Plan

Define girders and component parts not shown on the girder elevation view such as jacking stiffeners.Locate panel points (crossframe locations). Show general arrangement of bottom laterals. Providegeometry, bearing lines, and transverse intermediate stiffener locations. Show field splices and detailthe general configuration of crossframes in a section through framing plan.

For geometrically complicated structures, a rather detailed framing plan should be made to help guidethe shop detailer and the shop plan reviewer.

7.4.4 Girder Elevation

Define flanges, webs, and components thereof. Show shear connector spacing, location, and numberacross the flange. Show shear connectors in the girder details also. Locate transverse intermediatestiffeners and show requirements for clearance from tension flange. Define those components of thegirder subject to the Charpy V-notch requirements shown in the Standard Specifications. Define fullpenetration welds X or portions thereof subject to tension for which Radiographic (x-ray) examinationis required. See Standard Specifications. V and X are mentioned also in the Structural Steel Notes,Section 7.4.2. Permissible welded web splices may show, however, the optional welded web spliceshown elsewhere in the plans permits the fabricator to add splices subject to the approval of the engineer.

7.4.5 Typical Girder Details

One or two plan sheets should be devoted to showing typical details to be used throughout the girders.Such details include the weld details, various stiffener plates and weld connections, locations of optionalweb splices, and drip plate details. Include field splices here if only one type of splice will suffice forthe plans. An entire sheet may be required for complicated bridges with multiple field splice designs.See Appendix 7.4-A1 to A9. Note: Do not distinguish between field bolts and shop bolts. A solid boltsymbol will suffice.

7.4-2 August 1998


Structural Steel Plan Details

7.4.6 Crossframe Details

Typical crossframe and bottom lateral details are shown on Appendix 7.4-A10 to A12. Actual lengthsof members and dimensions of connections will be determined by the shop plan detailer. Details shouldincorporate actual conditions such as skew and neighboring members so that geometric conflicts can beminimized. Tee sections are preferred over double angles for easier painting. If double angles are used,leave a minimum of 1 inch between legs and include fillers as needed for stability.

7.4.7 Camber Curve and Bearing Stiffener Details

Camber curves should be detailed using conventional practices. Dimensions given at tenth points hasbeen office practice in the past. In lieu of tenth points, dimensions may also be given at crossframelocations which are more useful in the field. See Appendix 7.4-A13.

7.4.8 Roadway Slab

The roadway slab is detailed in section and plan views. For continuous spans, add a section showingnegative moment longitudinal reinforcing to the typical section shown at mid-span. If possible, continuethe positive moment region reinforcing pattern from end-to-end of the slab with the negative momentregion reinforcing superimposed on it. The plan views should detail typical reinforcing and cutofflocations for negative moment steel. Avoid termination of all negative moment steel at one location.See Appendix 7.4-A14 and A15.

The “pad” dimension for steel girders is treated somewhat differently than for prestressed girders. Thepad dimension is assumed to be constant throughout the span length. Ideally, the girder is cambered tocompensate for dead loads and vertical curves. However, fabrication and erection tolerances result inconsiderable deviation from theoretical elevations. The pad dimension is therefore considered only anominal value and is adjusted as needed along the span once the steel has been erected and profiled.The screed for the slab is to be set to produce correct roadway profile. The plans should reference thisprocedure contained in Standard Specification 6-03.3(39). The pad dimension is to be noted as nominal.As a general rule of thumb, use 11″ for short span rolled beam bridges, 12″ for short span plate girderbridges (150′ to 180′), 13″ for medium spans (180′ to 220′) and 14″ to 15″ for long spans (over 220′).These figures are only approximate. Use good engineering judgment when detailing this dimension.

7.4.9 Safety Cable Details

Safety cables for maintenance crews are standardized details. If room permits, include safety cables withtypical girder details. Cable locations may be adjusted to avoid conflicts with other details such as largegusset plates. See Appendix 7.4-A16.

P65:DP/BDM7

August 1998 7.5-1


Structural Steel Shop Plan Review

7.5 Shop Plan Review

Shop plans must be checked for agreement with the Contract Plans, Standard Specifications, and thespecial Provisions. The review procedure is described in Section 1.3.5 of this manual.

Welding procedure specifications and procedure qualification records should be submitted with shopplans. If not, they should be requested and received before shop plans are approved.

Most shop plans may be stamped:

“GEOMETRY NOT REVIEWEDBY THE BRIDGE & STRUCTURES OFFICE”

However, the reviewer should verify that lengths, radii, and sizes shown on shop plans are in generalagreement with the contract. The effects of profile grade and camber would make exact verificationdifficult. Some differences in lengths, between top and bottom flange plates for example, are to beexpected.

The procedures to follow in the event changes are required or requested by the fabricator can befound in Section 1.3.6 of this manual. In the past, shop plans with acceptable changes have been sonoted and stamped.

STRUCTURALLY ACCEPTABLE, BUT DOES NOTCONFORM TO THE CONTRACT REQUIREMENTS

P:DP/BDM7


Structural Steel Bibliography

7.99 Bibliography

The following publications can provide general guidance for the design of steel structures. Some of thismaterial may be dated and its application should be used with caution.

1. U.S. Steel Highway Structures Design Handbook, Volumes I and II.

This is a detailed design reference for “I” girders and box girders, both straight and curved, utilizingeither service load design or load factor design. Guidance for the design of wide flange beams is alsoincluded.

2. Design of Welded Structures by Omer H. Blodgett.

This publication is quite helpful in the calculation of section properties and the design of individualmembers. There are sections on bridge girders and many other welded structures.

3. Curved Girder Workshop produced by the Federal Highway Administration.

This publication is helpful in the design of curved “I” girders and box girders with explanation of theassociated lateral flange bending, torsional, and warping stresses.

P:DP/BDM7

August 1998 7.99-1

August 1998 7.4-A1


Girder Framing PlanStructural Steel and Elevation View


Part LongitudinalStructural Steel Girder Elevation

August 1998 7.4-A2


Structural Steel Primary Stiffeners

August 1998 7.4-A3


Structural Steel Transverse Intermediate Stiffener

August 1998 7.4-A4


Structural Steel Splices

August 1998 7.4-A5


Structural Steel Optional Web Splice

August 1998 7.4-A6


Structural Steel Fillet Weld Termination Detail

August 1998 7.4-A7


Structural Steel Field Splice Detail

August 1998 7.4-A8


Structural Steel Drip Plate Details

August 1998 7.4-A9


Structural Steel Crossframes

August 1998 7.4-A10


Structural Steel Crossframe Attachment Details

August 1998 7.4-A11-1



7.4-A11-2 August 1998



August 1998 7.4-A11-3


Structural Steel Lateral Plate Detail

August 1998 7.4-A12


Camber Curve and BearingStructural Steel Stiffener Camber Details

August 1998 7.4-A13


Miscellaneous Design Contents

August 1998 8.0-i

Page

8. Miscellaneous Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . *

8.1 Other Bridge Types . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . *

8.1.1 Timber . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . *

8.1.2 Railroad . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . *

8.1.3 Movable Bridge and Machinery . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . *

8.1.4 Cable Stayed . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . *

8.1.5 Floating Structures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . *

8.1.6 Suspension Bridges . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . *

8.1.7 Tunnels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . *A. General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . *B. Cut and Cover . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . *C. Bored . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . *

8.1.8 Elevated Railways . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . *

8.2 Sign and Luminaire Supports . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.2-1

8.2.1 Loads . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1A. General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1B. Deadloads . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1C. Wind Loads . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1D. Live Loads . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2E. Ice Loads . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2F. Snow Loads . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2G. Load Groups . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

8.2.2 Bridge-Mounted Signs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3A. Vertical Clearance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3B. Geometrics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4C. Aesthetics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6D. Sign Placement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6E. Installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7F. Dimensioning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

8.2.3 Sign Bridges Mounted on Bridges . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7A. Design Loads . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7B. Vertical Clearance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7C. Geometrics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

8.2.4 Foundations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

8.3 Miscellaneous Highway Structures Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.3-1

8.3.1 Impact Attenuator Supports . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1A. General Concept . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1B. Push Force on Back-Up Wall . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1C. Pulling Force from Restraining Cables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1D. Ground Mounted Units . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1E. Factored Load Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2F. Details . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2




8.0-ii August 1998

Page

8.3.2 Traffic Barriers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.3.2-1A. Guidelines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1B. Bridge Railing Performance Levels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1C. Available Bridge Rail Designs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2D. At Grade Cast-in-Place Barriers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

8.3.3 Bridge Rail Rehabilitation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.3.3-1A. Policy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1B. Guidelines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1C. WSDOT Bridge Inventory of Bridge Rails . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1D. Available Retrofit Designs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

8.3.4 Bridge Approach Slabs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . *

8.3.5 Utility Installation on Bridges . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.3.5-1A. Confined Spaces . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1B. Guidelines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1C. General Concepts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1D. Criteria for Utility Installation on New Bridges . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2E. Special Considerations for Various Districts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3F. Type of Conduit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4G. Types of Supports . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5H. Utility Review Procedure for Existing Bridges . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5I. Utility Review Checklist . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

8.3.6 Structural Plate Arches . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . *

8.4 Bridge Details . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.4.1-1

8.4.1 Expansion Joints . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1A. Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1B. Specifications for Bridge Deck Joints . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10C. Reviewing Shop Plans . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10D. Other Considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

8.4.2 Drainage Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.4.2-1A. General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1B. Geometrics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1C. Hydrology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1D. On Bridge Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1E. Construction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

8.4.3 Bridge Bearings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.4.3-1A. Purpose . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1B. Forces to Be Resisted . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1C. Movements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2D. Bearing Details . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4E. Orientation of Bearings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15F. Bearing Selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

8.4.4 Bridge Railing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . *

8.4.5 Ladders, Stairs, Grates, Etc. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . *

8.4.6 Surface Treatments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . *




August 1998 8.0-iii

Page

8.4.7 Deck Protective Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.4.7-1A. System Types . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1B. System 1 (Epoxy Coated Bars) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2C. System 2 (Dense Concrete or Latex Modified Concrete Overlay) . . . . . . . . . . . . . . . . . . . . . . 3D. System 3 (Asphalt Overlay with Waterproof Membrane) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4E. System Selection for New Structures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5F. System Selection for Bridge Deck, Widening, and Rehabilitation . . . . . . . . . . . . . . . . . . . . . . 5

8.5 Lighting and Electrical Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . *

8.5.1 General Considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . *

8.5.2 Illumination . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . *

8.5.3 Navigation Lighting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . *

8.5.4 Electrical Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . *

8.99 Bibliography . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.99-1


8.2-A1 Sign Structure Foundation Material Quantities

8.2-A2 Vacant

8.2-A3 Notes to Designers for Truss Sign Bridge Foundations

8.2-A4 Double Faced Barrier Foundation Types 1, 2, and 3 for Truss Sign Bridge

8.2-A5 Notes to Designers for Monotube Sign Bridge Foundations

8.2-A6 Doubled Faced Barrier Foundation Types 1, 2, and 3 for Monotube Sign Bridge

8.2-A7 Notes to Designers for Monotube Sign Structures

8.2-A8 Monotube Sign Structures — Member and Sign Criteria

8.2-A9 Monotube Sign Structures — Sign Bridge Layouts

8.2-A10 Monotube Sign Structures — Cantilever Layouts

8.2-A11 Monotube Sign Structures — Structure Details

8.2-A12 Monotube Sign Structures — Structure Details

8.2-A13 Monotube Sign Structures — Foundation Details Types 1, 2, and 3

8.3-A1 General Notes and Design Criteria for Utility Installation to Existing Bridges

8.3-A2 Guide for Utility Installations Existing Bridges

8.3-A3 Bridge Railing Type BP

8.3-A4 Bridge Railing Type BP-B

8.3-A5 Notes to Designers for Bridge Railing

8.3-A6 Traffic Barrier

8.3-A7 Traffic Barrier w/Fractured Fin Finish

8.3-A8 Pedestrian Barrier

8.3-A9 Pedestrian Barrier w/Fractured Fin Finish

8.3-A10 Notes to Designers for Traffic Barrier

8.3-A11 Utility Hanger Details

8.3-A12 Utility Hanger Details




8.0-iv August 1998

8.4-A1 Expansion Joint Details

8.4-A2 Standard Drain Modifications

8.4-A3 Bridge Drains Types 7 and 8

8.4-A4 Bridge Grate Inlet

8.4-A5 Bridge Grate Inlet Type 2

Appendix B — Examples

8-B1 Notes to Designers — Pin Bearings

8-B2 Notes to Designers — Spherical Bearings

8-B3 Notes to Designers — General

8-B4 Notes to Designers — Post-Tensioning

8-B5 Notes to Designers — Structural Steel (Box Girder)

8-B6 Notes to Designers — Structural Steel (Plate Girder)

8-B7 Notes to Designers — Strip Seal Expansion Joint

8-B8 Notes to Designers — Modular Expansion Joint

8-B9 Notes to Designers — Rail Rehabilitation

8.4-B1 Compression Seal Design Example

8.4-B2 Strip Seal Design — Example 1



8.4-B5 Gmin and Gmax for Modular Joints

8.4-B6 Modular Joint Design — Example 1



8.4-B9 Elastomeric Bearing Pad Example for P.S. Girder (Prestressed)

8.4-B10 Vacant

8.4-B11 Vacant

8.4-B12 Girder Stop Bearing Pads Example

8.4-B13 Elastomeric Bearing Pad Design Chart

8.4-B14 Girder Stop Bearing Pads Spacing Chart

8.4-B15 Girder Stop Bearing Pads Pad Thickness Chart

P:DP/BDM89807-0802


Miscellaneous Design Sign and Luminaire Supports

April 1991 8.2 - 1

8.2 Sign and Luminaire Supports

8.2.1 Loads

A. General

The reference used in developing the following office criteria is the 1975 AASHTO “StandardSpecifications for Structural Supports for Highway Signs, Luminaires, and Traffic Signals,” and shallbe the basis for analysis and design.

B. Deadloads

Sign (incl. stiffeners) 3.25 lbs./ft.2

Luminaire 60 lbs./eachFluorescent Lighting 3.0 lbs./ln. ftStandard Signal Head 60 lbs./eachMercury Vapor Lighting 6.0 lbs./ln. ftSign Brackets (No Maintenance Walkway) Calc.Structural Members Calc.5-foot-wide maintenance walkway (incl. sign mounting brackets) 60 lbs./ln. ft.11/2-foot-wide maintenance walkway between signs 28 lbs./ln. ft.

C. Wind Loads

Mean DragRecurrance Velocity Coeff

Type of Structure Interval (MPH)* (Cd)

Roadside Sign Support Round 10 80 1.10Roadside Sign Support Square 10 80 1.45Roadside Sign Support Octagonal 10 80 1.20Standard Plan G-2 50 80 1.20Standard Plan G-3 Chords 50 80 1.10Standard Plan G-3 Post 50 80 .45Monotube 50 80 1.45Signs 50 80 1.30Square Luminaires 50 80 1.20Round Luminaires 50 80 .50Signal Heads 25 80 1.20

*When designing structures on the Olympic Peninsula or south of Olympia and west of Interstate 5consideration should be given to using a wind velocity between 80 mph and 100 mph, see Isotachfigure (Appendix A). Local topography may also dictate the use of higher wind velocities.



8.2 - 2 April 1991

Wind Pressure **Height above for 80 MPH WindGround (FT) P (psf)

0 < H < 14 2214 < H < 29 2829 < H < 49 3149 < H < 99 3599 < H < 149 39

149 < H < 199 42199 < H < 299 44

**Values in this table were computed using Cd = 1.00; design pressures must be corrected by using thespecified value for Cd.

Wind Combination Normal Comp. Trans. Comp.

1 1.0 BL 0.2 BL2 .6 BL 0.3 BL

BL is a wind force and is equal to P times the exposed area of the sign and support system. BL isthen applied to the centroid.

D. Live Load

500 lbs. applied as a concentrated load at 3 feet from sign face (only where maintenance walkwaysare used).

E. Ice Loads

3 psf applied around all the surfaces of structural supports, horizontal members, and luminaires, butapplied to only one face of sign panels.

F. Snow Loads

The above stated ice load shall be considered to include any snow load for the commonly usedstructural support systems.

G. Load Groups

Sign, luminaire, and signal structures are designed using the maximum of the following three loadgroups:

Percent of *Loads Allowable Stress

Group I – DL 100Group II – DL + W 140Group III – DL + Ice + 1/2 (W**) 140

*No load reduction factors shall be applied in conjunction with these increased allowable stresses.

**W to be computed on the basis of the wind pressure formula, 25 psf minimum for W Group III.



April 1991 8.2 - 3

8.2.2 Bridge-Mounted Signs

A. Vertical Clearance

The bottom of the sign lighting bracket should be placed a minimum of 17 feet 6 inches and amaximum of 21 feet 0 inches above the lower roadway (see Figure 8.2.2-1). The minimum clearanceis a requirement of the current electrical code. Greater or lesser clearance may be approved byRoadway Development on an individual project basis.

Sign Vertical ClearanceFigure 8.2.2-1



8.2 - 4 April 1991

B. Geometrics

1. Signs should be installed at approximate right angles to approaching motorists. For structuresabove a tangent section of roadway, signs may be installed parallel to the structure provided thestructure skew does not exceed 10°. If the structure skew exceeds 10°, support brackets should bedesigned to provide a sign skew of no more than 10° from perpendicular to the lower roadway(see Figure 8.2.2-2).

Sign Skew on Tangent RoadwayFigure 8.2.2-2



April 1991 8.2 - 5

2. For structures located on or just beyond a horizontal curve of the lower roadway, signs may beinstalled parallel to the structure provided the structure chord-skew does not exceed 10°. If thestructure chord-skew exceeds 10°, support brackets should be designed to provide a sign chord-skew of no more than 10° from perpendicular to the chord-point determined by the approachspeed (see Figure 8.2.2-3).

3. The top of the sign shall be level.

Sign Skew on Curved RoadwayFigure 8.2.2-3



8.2 - 6 April 1991

C. Aesthetics

1. Preferably, the top of the sign and its support should not project above the bridge rail (see Figure8.2.2-4).

2. Whenever possible, the support structure should be hidden from view of traffic.

3. The sign support shall be detailed in such a manner that will permit the sign and lighting bracketto be installed level.

4. When the sign support will be exposed to view, special consideration is required in determiningmember sizes and connections to provide as pleasing an appearance as possible.

Sign Vertical LocationFigure 8.2.2-4

D. Sign Placement

1. Whenever possible, the designer should avoid locating signs under bridge overhangs. This causespartial shading or partial exposure to the elements. Also avoid placing the sign directly under thedrip-line of the structure. These conditions may result in uneven fading, discoloring, anddifficulty in reading (see Figure 8.2.2-5).

2. Whenever it is necessary to place a sign under a bridge due to structural or height requirements,the installation should be reviewed by Roadway Development.

Sign Horizontal LocationFigure 8.2.2-5



April 1991 8.2 - 7

E. Installation

1. Consideration shall be given to the method of installing the sign support and sign on thestructure. For example, a sign located underneath the overhang can cause problems in lifting thematerial into position and making the required connections.

2. When locating sign support brackets on the structure, a minimum of 2 inches of clearance shallbe provided between the edge of the required sign lighting zee-bar bracket and edge of thevertical sign support members.

3. An expansion-type concrete anchor is undesirable for attaching sign support brackets to thestructure. This is because the nature of the loads imposed on the anchors can cause vibration andpull-out. The Hilti HVA, Molly Parabond, Kelken-Gold Keli Bond, or ITW/Redhead EPCONCeramic 6, or approved equal with AASHTO M164 anchor bolts should be used for existingstructures and cast-in-place anchor bolts (ASTM A307) for new structures. When Hilti HVA,Molly Parabond, or Kelken-Gold, or ITW/Redhead systems are specified, the following shouldbe included:

(a) Anchor bolt system is to be installed using manufacturer recommendations in dry conditions.

(b) Torque anchor bolt nuts to proof load.

F. Dimensioning

Where show on the plans, the sign size shall be expressed in terms of horizontal by verticaldimension, i.e., X x Y, where X = horizontal dimension and Y = vertical dimension.

8.2.3 Sign Bridges Mounted on Bridges

A. Design Loads

Design loads for the supports of the sign bridges should be calculated based on assuming a 12-footdeep sign over the entire roadway width, under the sign bridge. This will account for any signs thatmay be added in the future. The design loads should follow the same criteria as described inSection 8.2.1. Loads from the sign bridge should be included in the design of the structure.

B. Vertical Clearance

Vertical clearance for sign bridges follow the same requirements as Bridge-Mounted Signs as statedin Section 8.2.1A.

C. Geometrics

Sign structures should be placed at approximate right angles to approaching motorists. Dimensionsand details of sign structures are shown in the Standard Plans, Sheets G-2, G-2a, G-3, andAppendix A of this chapter. When maintenance walkways are included, refer to Standard Sheet G-6.



8.2 - 8 April 1991

8.2.4 Foundations

The most efficient foundation design for sign, luminaire, and signal supports is the Caisson Foundation.Standard foundations have been designed; see Standard Plans G-2b, G-3a, J-1b, and Appendix A of thischapter.

The headquarters Materials Lab should be consulted as to which foundation type is to be used. Foundationtype 1 and 2 are designed for a lateral bearing pressure of 2,500 psf. Type 2 is the alternate to type 1when drilled shafts are not suitable. The type 3 foundation is designed for poor soil conditions where thelateral bearing pressure is between 2,500 psf and 1,500 psf.

The standard foundations have been modified for placement under traffic barrier, see Appendix A of thischapter.

8-2:V:BDM8


Miscellaneous Design Miscellaneous Highway Structures Design

April 1991 8.3 - 1

8.3 Miscellaneous Highway Structures Design

8.3.1 Impact Attenuator Supports

A. General Concept

This criteria is concerned with the support design of the Hi-Dro Cushion attenuator (liquid-filled cellswith cable guides and side panels), which is one of the two FHWA qualified energy-absorbingsystems to protect occupants of highway vehicles from fixed objects within the highway system. Forother systems, similar design procedures should be followed.

B. Push Force on Back-Up Wall

1. Vehicle Force Limitation

G loads for varying speeds and number of bay units can be found on page 2 of the DesignData — Hi-Dro Cushion Reusable Systems brochure. These values have good correlation withcalculated deceleration.

It is desirable that the average vehicle deceleration be limited to a maximum of 10 Gs. If thisvalue is higher than 10 Gs, we should recommend to the district that more units should be used.

2. Design Speed

Design speed shall be per highway Design Manual.

3. Design Force

The design force shall be determined from other values given in the above-mentioned table or1.8 x 4k x G, whichever is greater. The table is based on the results of full scale tests.

C. Pulling Force from Restraining Cables

If the attenuator is impacted at an angle, the restraining cables will exert a pulling force on theback-up wall and the front cable anchorage. The ultimate strength of the 7/8-inch restraining cables is56 kips each. To avoid a complicated dynamic analysis, design the back-up wall and front cableanchorage for a symmetrical load of 112 kips and also for unsymmetrical load of 56 kips actingthrough one restraining cable only. Provide flexure, shear and torsion reinforcement in the back-upwall as required by these two loading conditions.

D. Ground-Mounted Units

It is recommended that the back-up wall and anchor block foundations for ground-mounting units becombined into an integral unit. By this means, the stability of the structure in enhanced. Sliding andoverturning should be checked. The service loads should be used in establishing factors of safety.A minimum of 1.5 for overturning and for sliding, where:

W = Weight of Supportφ = Friction CoefficientH = Horizontal ForcePp = Passive Pressure =

φ = Angle of Internal Frictionγ = Unit Weight of Soil

γh2 (1 + Sin φ) 2 (1 - Sin φ)

Wφ + Pp H

>= 1.3



8.3 - 2 October 1993

E. Factor Load Design

The loads previously determined due to impacting or pulling of cables shall be multiplied by a factorof 1.5 for Ultimate Load condition because it is an impulse loading. The dead load of the supportshall be multiplied by the usual factor of 1.3. The resultant of these loads should lie in the middle halfof the support footing. Minimum steel requirements of AASHTO Reinforced Concrete Design shouldbe checked except where a construction joint makes it impossible for tension to develop in theconcrete.

F. Details

For details of scale anchorages and attenuator hardware required for the back-up wall, see themanufacturer’s brochure or shop drawings of previous installations.



8.3.2 Bridge Traffic Barriers

A. Guidelines

1. The design criteria for bridge traffic barriers on structures shall be in accordance with Section 2of the Standard Specifications for Highway Bridges adopted by AASHTO.

2. The standard approach for new bridge rails is a 32 inch high safety shape (F Shape) concretebarrier on all interstate and major highway routes. Use a Single Slope concrete bridge rail whenthere are Single Slope concrete barriers on grade in the median for approaches to bridges or forcontinuity within a corridor. (See Design Manual Section 710 for additional background andcriteria.) The Standard Single Slope bridge rail is 34 inches high to be consistent with the heightsbeing used on grade applications.

3. Use taller 42 inch high safety shape or single slope bridge rails on interstate or freeway routes inthe following circumstances:

• When accident history suggests a need.

• When roadway geometrics increase the possibility of larger trucks hitting the barriers ata high angle (such as on ramps for freeway to freeway connections with sharp curvature inthe alignment).

4. In addition, the Guide Specifications for Bridge Railings have been adopted by AASHTO togive specific requirements for crash testing of bridge barriers prior to their use on all newbridge structures. The AASHTO Guide Specifications differentiate crash test criteria for variousperformance levels depending upon in part traffic volume, design speed, vehicle mix, and otherfactors that produce a vast variation in traffic railing performance needs from one site to another.

5. Guardrail approach transitions to bridge railing shall also be crash tested and consistent with theperformance level dictated by the bridge site. The criteria for its use shall be in accordance withthe Highway Design Manual, Section 710.10 and the appropriate standard plans.

B. Bridge Railing Performance Levels

It must be recognized that bridge railing performance needs differ greatly from site to site over ourhighway network and that railing designs and costs should match facility needs. This concept isembodied within the Guide Specifications for Bridge Railing. Three bridge railing performance levelsand associated crash test/performance requirements are given in these guide specifications along withguidance for determining the appropriate performance level for a given bridge.

1. Performance Level 1 (PL1)

On low-volume roads with little accident history, the concrete traffic barrier may not bewarranted with concurrence of roadway geometrics. Crash tested breakaway guardrail systemsand otherwise semi-rigid guardrail systems have shown that they can effectively contain vehicleson the bridge without undue damage to the bridge deck.

Other semi-rigid guardrail systems also qualify for this performance level due to geometricfeatures such as height. Examples of these semi-rigid and weak post guardrail systems are shownin Section 8.3.2C.1.

July 2000 8.3.2-1




This performance level is defined as a rigid rail system that generally meets AASHTO’s strengthrequirements of 10 kips lateral impact capacity. The concrete New Jersey barrier and F shapeconfiguration would qualify under this performance level. Rail systems under this category haveto be capable of resisting not only compacts and passenger cars but also 18,000 lb. single unittrucks (see Table G2.7.1.3A in the Guide Specification).


Higher capacity bridge rails are sometimes required for cases of high traffic volume withlarge truck or bus percentage. High accident rates with these trucks or buses may warrant thisperformance level. The crash test matrix for this performance category includes a 50,000 lb.tractor trailer.

C. Available Bridge Rail Designs

1. Performance Level 1

a. Service Level 1 Weak Post Guardrail

This bridge railing is a crash tested weak post rail system that was developed by NCHRPReport 239 for low-volume rural roadways with little accident history. We have utilized thisdesign on some of our short concrete spans and on our timber bridges. A failure mechanismis built into this rail system such that upon impact the post will break away with the thriebeam guardrail containing the vehicle by virtue of its ribbon strength. This failure mecha-nism assures minimum damage, if any at all, to the bridge deck and stringers. The estimatedcost for this system as a retrofit to existing structures is $75 to $85 per linear foot. Details forsome examples of retrofitted weak post systems are shown in Figures 8.3.2-1 and 8.3.2-2.This system could be used by cities and counties on new structures in which the cost can beestimated at $40 to $50 per linear foot. The appropriate guardrail approach transition shall bea Case 14 placement as shown on Standard Plan C-2h.

b. Oregon Side Mounted Guardrail

This thrie beam guardrail system is an approved crash tested rigid rail which will requirea Type 4B transition leading up to the bridge (see Standard Plan C-3 2 of 2). This systemis ideally suited for cast-in-place and precast slab superstructures with at least 15-inchminimum slab depth (see Figure 8.3.2-3).

c. California Side Mounted Guardrail

This thrie beam guardrail system is a crash tested rigid rail system which again requires aType 4B transition. This rail system is suited to slab superstructures of 12-inch minimumdepth (see Figure 8.3.2-4).

d. Glu-Lam Timber Rail on Wood Deck

This is a crash tested treated timber rail system that may be used for low performance levelfacilities (see Figure 8.3.2-5).

8.3.2-2 July 2000



e. Texas T-202 Concrete Beam and Post

This crash tested rail system offers a combination of low maintenance and low profilesee-through characteristics. A Type 1 guardrail transition as shown by Standard Plan C-31 of 2 is required (see Figure 8.3.2-6).

f. Nebraska Concrete Beam and Post

This is a similar rail system to the Texas T-202 rail with more opening at the base. Again aType 1 guardrail approach is required at bridge ends (see Figure 8.3.2-7).

g. California Type 115 Tubular Steel Rail

This crash tested system offers a see-through low profile steel rail option to the thrie beamguardrail. A Type 1 guardrail approach transition would be required at the bridge ends (seeFigure 8.3.2-8).

h. Texas T-411 Aesthetic Concrete Baluster

Texas developed this standard for a section of highway that was considered to be a historiclandmark. So in response to this fact, the existing deficient concrete baluster rail wasreplaced with a much stronger concrete baluster that satisfactorily passed the crash testperformance criteria set forth by the NCHRP Report 230 (see Figure 8.3.2-9).

i. Texas Guardrail Fence for Box Culverts

Texas developed this semi-rigid standard for the many box culvert situations that face allhighway engineers. W-Beam guardrail is attached to steel posts that is mounted to the top ofthe concrete deck for fill depths of 0 inches to 37 inches. A disadvantage of this is that whenthis rail system is hit the repair sometimes requires the replacement of the steel post therebynecessitating excavation of the fill. Washington has developed a take off from this designthat addresses this point by introducing a stiffer steel post in the fill that will hopefully neverneed replacement. This detail is shown in Standard Plan C-10. The required guardrailtransition is shown in Standard Plan C-2i.


a. 32-Inch New Jersey (NJ) Shape Concrete Traffic Barrier

This rail treatment is preferred for most higher volume state highway facilities because ofits past performance as far as the redirection capability and its low maintenance costs. If anoverlay is contemplated either at the time of construction or within one year after the project,the vertical lip at the base shall be 3 inches plus the overlay depth. Otherwise this lip depthshall be allowed to vary from 0 inch to 3 inch max. Under no circumstances shall thisdepth exceed 3 inches. Any additional barrier height adjustments due to camber shall beaccommodated at the top of the barrier (see Figure 8.3.2-10).

A tapered traffic barrier end section is used to allow a snow plow to approach the bridgeusing the guardrail as a guide without damaging the toe of the barrier. The vertical faceof the barrier end section allows for an easy thrie beam guardrail Terminal Design Fconnection.

July 2000 8.3.2-3



b. 32-Inch “F” Shape Concrete Traffic Barrier

This configuration was crash tested in the late 1960s along with the NJ Shape and then againrecently at this performance level. This more vertical shape actually tested better than the NJface which had more of an inclination to roll vehicles over upon impact. Oregon DOTcurrently uses this configuration (see Figure 8.3.2-11).

An alternate precast barrier with the “F” shape configuration is now available for useadjacent to bridges near the Oregon border (see Standard Plan C-8d).

c. 32-Inch Vertical Face Concrete Barrier

This crash tested rail system offers a simple to build concrete alternative to the NJ and“F” shape traffic rail configurations (see Figure 8.3.2-12).

d. Illinois 2399 Tubular Steel Rail

This crash tested model offers a light weight and open rail alternative to the concrete trafficbarriers outlined above. A rigid thrie beam guardrail transition would be required at thebridge ends (see Figures 8.3.2-13 and 8.3.2-14).

e. New York Thrie Beam Guardrail

This crash tested rail system can be utilized at the top of a raised concrete sidewalk toseparate pedestrian traffic from the vehicular traffic as shown in Figure 8.3.2-15 or can bemounted directly to the top of the concrete deck. A Type 4B guardrail transition shall beemployed at the ends of the bridge.

f. Oregon 2 Tube and 3 Tube Curb Mounted Rail

This is another crash tested model offering a light-weight, see-through option. A rigid thriebeam guardrail transition would be again required at the bridge ends. A cross-section of thisrail is offered in Figure 8.3.2-16.

A three tube rail system is also available for sidewalk use without vehicular traffic. This hasnot been crash tested satisfactorily to be utilized as a vehicular rail. This rail is shown inFigure 8.3.2-17.


a. 42-Inch “F” Shape Concrete Barrier

This barrier is very similar to the 32 inch F shape concrete barrier in that the slopes of thefront surface are identical except for its height. This barrier and all remaining options withinthis section have been crash tested for a 50,000 lb. tractor trailer.

This barrier was used on a portion of the Seattle Access project in Seattle due to the largevehicular mix of intercity buses and the fact that there was a building below that needed tobe protected. Another application of this barrier was utilized on the SR101 to SouthboundSR5 structure where there were an unusually large amount of truck accidents with debristhrown to the structure below (see Figure 8.3.2-18).

8.3.2-4 July 2000



b. 42-Inch Vertical Concrete Parapet

This crash tested option offers a simple to build alternative to the “F” shape configuration(see Figure 8.3.2-19).

4. Special Higher Performance Level

a. Texas Type HT

This crash tested rail employs a combination New Jersey Traffic Barrier and a special steelrail mounted to the top with an overall height of 50 inches. This and other options listedwithin this section have been crash tested for a 80,000 lb. truck (see Figure 8.3.2-20).

b. Texas C202 Bridge Rail

This rail system offers a combination open concrete beam/post and a metal rail with anoverall height of 54 inches (see Figure 8.3.2-21).

D. At Grade Cast-in-Place Barriers

1. Median Barriers

a. Cast-in-Place barriers (Type 2) at grade are sometimes required in median areas withdifferent roadway levels at each side (see Figure 8.3.2-22). A Cast-in-Place barrier with1 foot 0 inch or less difference in elevation has been crash tested successfully with a 10-inchembedment depth. No foundation such as a footing is required. If this difference in elevationis greater than 1 foot, the barrier shall be designed as a wall with AASHTO’s barrier loadingand will require a footing.

Design criteria for allowable distribution width for impact on barriers with greater than1 foot of elevation difference is as follows:

(1) For stability calculations: distribution width for impact load shall be 16 feet for wallsunder 16 feet high.

(2) For reinforcing steel design in the stem and footing: distribution shall be the smaller of2H or 16 feet where H is the height of the wall.

Additional design data is given on Standard Plan D-2e.

2. Shoulder Barriers

Cast-in-Place shoulder barriers at grade are sometimes desired adjacent to bridge sidewalkbarriers in lieu of standard precast Type 2 barriers (see Figure 8.3.2-23). This barrier crosssection has equivalent mass and resisting moment for stability considerations to that of theembedded double face New Jersey Traffic Barrier which has been satisfactorily crash tested.A wire rope and pin connection shall be made at the bridge barrier end section per StandardPlan C-8. If a connection is made to an existing traffic barrier or parapet on the bridge, 15 incheslong holes shall be drilled for the wire rope connection and shall be filled with an adhesive resin.

P65:DP/BDM8

July 2000 8.3.2-5



Figure 8.3.2-1

8.3.2-6 September 1992



Fig

ure

8.3.

2-2

September 1992 8.3.2-7



Ore

gon

Sid

e M

ount

ed G

uard

rail

Fig

ure

8.3.

2-3

8.3.2-8 September 1992



California Side Mounted GuardrailFigure 8.3.2-4

September 1992 8.3.2-9



Glu

-Lam

Tim

ber

Rai

lF

igur

e 8.

3.2-

5

8.3.2-10 September 1992



Texas T-202 RailFigure 8.3.2-6

September 1992 8.3.2-11



Neb

rask

a C

oncr

ete

Bea

mpo

st R

ail

Fig

ure

8.3.

2-7

8.3.2-12 September 1992



Cal

ifor

nia

Typ

e 11

5 R

ail

Fig

ure

8.3.

2-8

September 1992 8.3.2-13



Tex

as T

-411

Aes

thet

ic C

oncr

ete

Bal

uste

rF

igur

e 8.

3.2-

9

8.3.2-14 September 1992



32-Inch New Jersey ShapeFigure 8.3.2-10

September 1992 8.3.2-15



32-Inch “F” ShapeFigure 8.3.2-11

8.3.2-16 September 1992



32-Inch Vertical Concrete ParapetFigure 8.3.2-12

September 1992 8.3.2-17



Illi

nois

239

9R T

ubul

ar S

teel

Rai

lF

igur

e 8.

3.2-

13

8.3.2-18 September 1992



Illi

nois

239

9R T

ubul

ar S

teel

Rai

lF

igur

e 8.

3.2-

14

September 1992 8.3.2-19



New York Thrie BeamFigure 8.3.2-15

8.3.2-20 September 1992



Oregon 2 Steel Tube RailFigure 8.3.2-16

September 1992 8.3.2-21



Oregon 3 Steel Tube RailFigure 8.3.2-17

8.3.2-22 September 1992



42-Inch “F” ShapeFigure 8.3.2-18

September 1992 8.3.2-23



42-Inch Vertical Concrete ParapetFigure 8.3.2-19

8.3.2-24 September 1992



Texas Type HT RailFigure 8.3.2-20

September 1992 8.3.2-25



Texas C202 Bridge RailFigure 8.3.2-21

8.3.2-26 September 1992



CIP Median BarrierFigure 8.3.2-23

September 1992 8.3.2-27

CIP Median BarrierFigure 8.3.2-22



September 1992 8.3.3 - 1

8.3.3 Bridge Rail Rehabilitation

A. Policy

The bridge rail retrofit policy is “To systematically improve or replace existing deficient rails withinthe limits of 3R resurfacing projects by (1) utilizing an approved crash tested rail system that isappropriate for the site or (2) designing up to the strength requirements set forth by Section 2 ofAASHTO.”

B. Guidelines

Strength and geometric review, using the latest AASHTO Specifications, is required for all bridge railrehabilitation projects. If the strength of the existing bridge rail is found to be less than 10 Kips or hasnot been crash tested, then modifications or replacement will be required to improve its redirectionalcharacteristics and strength.

C. WSDOT Bridge Inventory of Bridge Rails

The Bridge Condition Unit maintains an inventory of all bridges in the state on the State ofWashington Inventory of Bridges and Structures (SWIBS) program. Bridge rail types are indicated bya code from 1 to 8 depending upon type of rail. The coded rail types are shown in Figure 8.3.3-1.

1. This Timber Post and Rail system has been used on timber trestle structures. The rail is structur-ally deficient and requires a retrofit with thrie beam guardrail (see Section 8.3.2C.1a).

2. This combination steel post and flex beam guardrail system generally includes steel posts withspacing between 9 feet and 12 feet 6 inches, which is in excess of the required 6 feet 3 inches.Generally, additional steel posts are required as well as thrie beam guardrail or other approvedrail system to bring this system up to standards.

3. This combination steel post and tubular guardrail system was used in a limited way for a shortperiod of time. It is normally adequate but, if damaged, it is very difficult to repair because thesections of guardrail are welded back to back.

4. Concrete balusters are deficient in lateral load capacity, having approximately 3 kips while10 kips is required. These rails are normally retrofitted with thrie beam guardrail (see Section9.3.3D.1).

5. New Jersey shaped traffic barriers have been used by WSDOT since 1970 and meet the currentcode requirements.

6. This combination low-base concrete pedestal and metal rail is considered deficient and should bereplaced with Type 1, 1A, and 2 metal rails.

7. This combination high-base concrete parapet and metal rail may or may not be consideredadequate depending upon the rail type. Metal rail Type R, S, and SB are considered capable ofresisting the required 5 kips of lateral load. Types 3, 1B, and 3A are considered inadequate. SeeHighway Design Manual, Section 710.09 for replacement criteria.

8. A combination metal rail and New Jersey Traffic Barrier has been used rarely by WSDOT but isconsidered to be adequate.



8.3.3 - 2 September 1992

D. Available Retrofit Designs

1. Washington Thrie Beam Retrofit of Concrete Balusters

This system consists of thrie beam guardrail stiffening of existing concrete baluster rails withtimber blockouts (see Figure 8.3.3-2). Southwest Research Institute conducted full-scale crashtests of this retrofit in 1987. Results of the tests were satisfactory and complied with criteria for aPerformance Level 1 (PL1) category in the Guide Specifications. Bids over the last several yearshave shown that this retrofit can be estimated at $25 per linear foot.

2. Thru Truss Rail Retrofit

High priority is placed upon retrofitting thru truss span bridges, not only because of the possibil-ity of serious injury accidents, but also because severe damage may occur to the main structuralelements of the bridge. Design details which accommodate a rigid guardrail system have beendeveloped. The design both alleviates the problems mentioned and provides redirectional capabil-ities (see Figures 8.3.3-3 through 8.3.3-8). The thrie beam and post system on the curb side aredesigned for a 10 kip lateral load as described by AASHTO. The thrie beam and steel post on thesidewalk side is the New York crash tested system as described in Section 8.3.2-C.

3. New Jersey Traffic Barrier

This is our preferred treatment for replacing deficient rails and parapets on high volumehighways with a large truck percentage. All interstate highway bridges shall use this type (seeFigures 8.3.3-9 through 8.3.3-11).

8-3-3:V:BDM8



September 1992 8.3.3 - 3

WSDOT Bridge Inventory Bridge Rail TypesFigure 8.3.3-1



8.3.3 - 4 September 1992

Was

hing

ton

Thr

ie B

eam

Fig

ure

8.3.

3-2



September 1992 8.3.3 - 5

Rai

l Ret

rofi

t — P

L2

Thr

u T

russ

Spa

nF

igur

e 8.

3.3-

3



8.3.3 - 6 September 1992

Figure 8.3.3-4



September 1992 8.3.3 - 7

Rai

l Ret

rofi

t — P

L2

App

roac

h S

pan

— T

hru

Tru

ssF

igur

e 8.

3.3-

5



8.3.3 - 8 September 1992

Rail Retrofit — Truss SpanFigure 8.3.3-6



September 1992 8.3.3 - 9

Figure 8.3.3-7



8.3.3 - 10 September 1992

Rail Retrofit — Approach SpansFigure 8.3.3-8



September 1992 8.3.3 - 11

Typical Section — Traffic Barrier Without OverhangFigure 8.3.3-9



8.3.3 - 12 September 1992

Typical Section — Traffic Barrier With OverhangFigure 8.3.3-10



September 1992 8.3.3 - 13

Traffic Barrier RetrofitFigure 8.3.3-11



8.3.4 - 1



8.3.5 Utility Installation on Bridges

A. Confined Spaces

A confined space is any place having a limited means of exit which is subject to the accumulation oftoxic or flammable contaminants or an oxygen deficient environment. Confined spaces include but arenot limited to pontoons, box girder bridges, storage tanks, ventilation or exhaust ducts, utility vaults,tunnels, pipelines, and open-topped spaces more than 4 feet in depth such as pits, tubes, vaults, andvessels. The designer should provide for the following:

• A sign with “Confined Space Authorized Personnel Only.”

• In the “Special Provisions Check List,” alert and/or indicate that a special provision might beneeded to cover confined spaces.

B. Guidelines

The utilities which are to be considered under this guideline are power and telephone lines, naturalgas, volatile fluid pipes, water pipes, and sewer pipes. Each utility has its unique installationproblems.

Most utility installations will be initiated by the utility company or the district, and the BridgeManagement Section will review the design. In some cases, such as new projects, certain originaldesigns are done by the Bridge Division, such as hanger details for water lines.

The following subjects are covered below:

General ConceptsCriteria for Utilities Installation on New Bridgesspecial Considerations for Various UtilitiesType of ConduitTypes of SupportsUtility Review Procedure for Existing BridgesUtility Review Checklist

C. General Concepts

On new construction, the utility installation shall be located so as to minimize the effect on theappearance of the structure. In most cases, this will mean installing the utility between girders or incurbs. Utilities and supports shall not normally extend below the bottom of the superstructure. Whenthe utility is located between girders, it shall be installed no lower than 1 foot 0 inches above thebottom of the girders. In some cases when appurtenances are required (such as air release valves),care should be taken to provide adequate space.

When the bridge is to receive pigmented sealer, consideration shall be given to painting any exposedutility lines and hangers to match the bridge. When pigmented sealer is not required, steel utility linesand hangers shall be painted or galvanized for corrosion protection. This special provisions shall spec-ify cleaning and painting procedures.

On existing structures, proposed utility attachments are normally reviewed by the Bridge ManagementSection and either approved or returned for correction. A current file for most utility attachments ismaintained in the Bridge Management Section. See “Utility Review Procedure For Existing Bridges”and “Utility Review Checklist” (Sections 8.3.5G and 8.3.5H).

July 1994 8.3.5 - 1



D. Criteria for Utilities Installation on New Bridges

1. All pipelines carrying volatile fluids shall be encased throughout the length of the structure. Asleeve approximately 3 inches larger than the outside diameter of the carrying pipe shall be used.The space between the carrying pipe and the encasing sleeve shall be effectively vented beyondthe structure at each end and at high points.

2. Utilities shall not be attached above the bridge deck nor attached to the railings or posts. Theymay be placed in the concrete traffic barrier no higher than 16 inches above the top of the deck.

3. Utilities shall not extend below the bottom of the superstructure.

4. The utilities shall be provided with suitable expansion devices at bridge expansion joints orexpansion methods as required to prevent longitudinal temperature forces from being transferredto bridge members. Longitudinal restraint may often be considered to be the bridge end fill. Fortelephone and power conduit, this restraint may be considered to be the cable itself. Where longruns of water pipe are used, care must be taken that expansion joints in the pipe are properlyspaced with longitudinal load-carrying supports.

5. Rigid conduit shall extend 10 feet minimum beyond the ends of the structure in order to reduceeffects of embankment settlements on the utility and provide protection in case of future workinvolving excavation near the structure. This requirement shall be stated on the plans. Utilities offthe bridge must be installed prior to paving of approaches. This should be stated in the SpecialProvisions.

6. Utility supports shall be designed so that neither the conduit, the supports, nor the bridgestructure or members are overstressed by any loads imposed by the utility installation.

Provide longitudinal and transverse support for loads from gravity, earthquakes, temperature,inertia, etc. It is especially important to provide transverse and longitudinal support for Grinnellinserts and other similar inserts which cannot resist moment.

7. Utility locations and supports shall be designed so that a failure will not result in damage to thebridge, the surrounding area, or be a hazard to traffic.

8. All conduit shall be steel pipe or rigid PVC pipe.

*(Items 1 through 8 may be cross-referenced with Design Criteria of “General Notes and DesignCriteria” in Appendix A of this chapter or Chapter 1 Examples of the Utilities Manual.)

9. Utilities installed in the cells of box girder bridges shall be embedded in concrete wherestructurally and economically feasible. Where utilities, other than telephone and power conduit,are not embedded in concrete, access shall be provided in each cell. Such access can be frommanholes in the shoulder of the roadway or in the sidewalk. Current practice for access to boxgirder cells is to locate a hatch in the bottom of the box girder at the end piers. Where access isprovided into the cells, the Special Provisions must call for removal of the top slab formwork inthose cells.

10. Telephone and power conduit may be installed in the cells of box girder bridges withoutprovision for embedment or access provided that conduit is galvanized steel pipe, or Schedule80 PVC rigid or heavier.

8.3.5 - 2 May 1995



E. Special Considerations for Various Utilities

1. Gas Lines or Volatile Fluids

Gas lines or lines carrying volatile fluids shall be of steel pipe (usually Schedule 40) designed inaccordance with CFR Part 192, Transportation of Natural and Other Gas by Pipeline: MinimumSafety Standards (see WAC 480-93-010). Volatile fluids shall be encased in a steel encasementpipe as noted in C “Criteria.” Gas lines are not required to be encased in a steel encasement pipe.Contact the District Utilities Engineer for guidance on whether or not the utility uses encasementpipe. If it does not, provide the transverse insert as if there will not be encasement and blockoutsin the structure as if they will be encasement (BDM 8.3.5-D). All gas lines shall be transverselybraced. District Utility Engineers shall be contact by the S&E (Specifications and Estimates)office for additional design requirements that may be stipulated in the utility agreement. Nor-mally, the utility will make provision to electrically insulate the gas line from its support. Linescarrying other volatile materials shall be supported, as required by the utility, with due care takento protect the structure and traffic.

Access and ventilation shall always be provided in box girder cells containing gas lines.

2. Water Lines

Water lines shall be galvanized steel pipe or ductile iron pipe. Where freezing may beencountered, consideration should be given to the use of insulation on the pipe. Insulation shallbe jacketed and saddles shall be galvanized to avoid electrolysis.

Care shall be taken that all inertia loads due to dynamic action (water hammer, etc.) can beproperly carried. Transverse supports shall be provided for all water lines. Additional temporarybracing will be required during pressure testing. The design loading of the temporary bracingalong with a note stating “See Special Provisions” shall be shown on the plans. Pressure testloading force magnitude shall be obtained from District Utility Engineers by the S&E unit.

Fire control piping is a special case where unusual care must be taken to handle the inertial loadsand associated deflections. Normally, the Hydraulic Section will also be involved in this case.

In box girders, care shall be taken to ensure that a failure of the water line would not flood thecell with an excess amount of water which may cause consequential structural failure of thegirder. Additional weep holes or open grating shall be used if necessary (see Figure 8.3.5-3).

3. Sewer Lines

Normally, an appropriate encasement pipe is required for sewer lines on bridges. Sewer linesmust meet the same design criteria as waterlines. See the utility agreement or the HydraulicSection for types of sewer pipe material typically used.

4. Telephone and Power Conduit

Generally, telephone, television cable, and power conduit shall be galvanized steel pipe or a PVCpipe of a UL approved type and shall be Schedule 40 or heavier. Where such conduit is buried inconcrete curbs or barriers or has continuous support, such support is considered to be adequate.Where conduit is supported by hangers or brackets at intervals, the distance between supportsshall be small enough to avoid excessive sag between supports (see PVC pipe in E below).Generally, the conduit shall be designed to support the cable in bending without exceeding work-ing stresses for the conduit material. When the conduit is intended to encase Department ofTransportation electrical wiring and is encased in concrete, only galvanized steel conduit shall beused. Also, only galvanized steel conduits will be allowed in barriers when slipforming is

July 1994 8.3.5 - 3



employed. Stub outs for galvanized steel pipe shall be protected against corrosion as stated insubparagraph 5.

5. Rigid Electrical Conduit for Highway Circuits

In the case of all new bridge construction where roadway shoulders have not yet been paved andwhere usable shoulder width is 4 feet or greater in width, electrical conduit shall be stubbed-outand capped 1 foot 6 inches below grade and 3 feet 0 inches horizontally toward roadway center-line from the face of the traffic barrier. Longitudinally, this stub-out location should be near theback of pavement seat. The conduit in this location should clear any foreseeable obstructions. Thelocation of the stubbed-out conduit at bridge ends should be clearly shown on the plans. Thegalvanized steel conduit stub out shall be wrapped with corrosion resistant tape at least one footinside and outside of the concrete structure, and this requirement shall be so stated on the plans.The corrosion resistant tape shall be 3M Scotch 50, Bishop 5, Nashua AVI 10, or approved equal.The usual location of the conduit throughout the remainder of the bridge should be in the trafficbarrier.

The number and size of conduits within the traffic barrier shall be minimized to assure properconcrete consolidation. A maximum of one (1) 4-inch conduit or two (2) 2-inch conduits will beallowed.

Pull boxes shall be provided at a maximum spacing of 200 feet. Their size shall conform to thespecifications of the National Electric Code or be a minimum of 6 inches by 6 inches by18 inches to facilitate pulling of wires. Galvanized steel pull boxes (or junctions boxes)shall meet the specifications of the “NEMA Type 4X” standard and shall be so stated on the plans.Stainless steel pull boxes shall be allowed as an option to the galvanized steel.

In the case of existing bridges, an area 2 feet in width shall be reserved for conduit beginning at apoint either 4 feet or 6 feet outside the face of usable shoulder. The fastening for and location ofattaching the conduit to the existing bridge should be worked out on a job-by-job basis.

See Figure 8.3.5-1.

F. Type of Conduit

1. Steel Pipe

All steel pipe conduits shall be Schedule 40 or greater. All pipe and fittings shall be galvanizedexcept for special uses.

2. PVC Pipe

PVC pipe may be used with suitable considerations for deflection, the location and placement ofexpansion fittings, and of freezing water within the conduits. Where conduit is to be exposed inthe cells of box girder bridges, PVC should be avoided because of the possibility of damageoccurring when the top slab falsework collapses. If such falsework is specified on the plans to beremoved after construction, this provision does not apply.

PVC pipe should not be placed in concrete traffic barriers due to damage and pipe separation thatoften occurs during concrete placement and from temperature variations.

Where conduit is to be supported by hangers or pedestals at intervals, the distance betweensupports shall be small enough to avoid excessive sag of the conduit. For recommended supportspacing and tabulated properties of PVC pipe, see Table 8.3.5-1.

8.3.5 - 4 July 1994



3. High Density Polyethylene

This material may be specified by some utilities. Unless other data is available, support as forPVC. Same restrictions to traffic barriers apply.

4. Fiberglass Pipe

This material may be specified by some utilities. Unless other data is available, support as forPVC. Same restrictions to traffic barriers apply.

G. Types of Supports

The following types of supports have been used. Selection of a particular support type should bebased on the needs of the installation and the best economy.

1. Concrete Embedment — This is the best structural support condition and offers maximumprotection to the utility. Its cost may be high for larger conduit and the conduit cannot bereplaced. Special car must be taken to handle expansion joints.

2. Continuous Support — This support condition may be achieved by providing ledge of concreteto support the conduit. In addition, some type of clamping will be required. The support conditionhere is very good, but the cost may be very high.

3. Concrete Pedestals — This consists of concrete supports formed at suitable intervals andprovided with some type of clamping device.

4. Pipe Hangers — This is the most usual type of support for utilities to be supported under thebridge deck. It allows the use of standard ordered parts (usually “Grinnell”) and is very flexible interms of expansion requirements. It will not normally provide longitudinal support*, andtransverse support must be provided by a second hanger extending from a girder or by placingbracing against the girder.

*Support at every pipe joint — longitudinal restraint of hangers may be necessary with the use ofGrinnell Universal Insert, Figure 282 or similar inserts.

5. The Figures 8.3.5-2, 3, and 4 depict typical utility support installations and placement atabutments and diaphragms.

H. Utility Review Procedure for Existing Bridges

It is the responsibility of the District Utilities Engineer to forward any proposed bridge attachments tothe Bridge Office. The Bridge Office is responsible for reviewing only those details pertaining to thebridge crossing such as attachment details or trenching details adjacent to bridge piers or abutments.The turnaround time for reviewing the proposals should not exceed two weeks; however, most attach-ments that have simple connections with epoxy anchors can be reviewed, stamped, and responded towithin one day. This is provided that corrections and additional notes are minimal.

The number of copies to be returned is determined by the district. Most districts send five copies ofthe proposed utility attachment. We keep one copy and, if it’s been approved, return four markedcopies. If it has been returned for correction or not approved, we keep one and return two markedcopies. See the “Utility Review Checklist” below (Section 8.3.5H).

July 1994 8.3.5 - 5



Conduit Location Beyond Bridge EndFigure 8.3.5-1

8.3.5 - 6 July 1994



July 1994 8.3.5 - 7



Occasionally, a utility company wants a conceptual approval of their proposed attachment before theyinvest their time in detailed drawings and calculations. Often they will request this approval by send-ing a sketch of their proposal directly to the Bridge Office. We will usually respond directly to themin a letter by concurring with their proposal or by suggesting an alternate. This letter includes instruc-tions for them to resubmit their final proposal through the District Utilities Engineer with a courtesycopy of this letter sent to the District Utilities Engineer.

Utility attachments which exert moments or large forces at the bridge connection should be accompa-nied by at least one set of calculations from the utility company. Bridge attachments designed to resistsurge forces should always be accompanied by calculations. The engineer may request calculationsfrom the utility company for any attachment detail that may be questionable.

The engineer shall check the utility company’s design with his own calculations. The connectiondetail shall be designed to successfully transfer all forces to the bridge without causing overstress inthe connections or to the bridge members to which they are attached. For large utilities, the bridgeitself shall have adequate capacity to carry the utility without affecting the live load capacity.

For more detailed guidelines, see “General Notes and Design Criteria . . .” and “Guide for UtilityInstallations to Existing Bridges” in Appendix A of this chapter.

1. Utility Review Checklist

(For review of all proposed utility attachments to existing bridges.)

1. Do a cursory check to become familiar with the proposal.

2. Determine location of existing utilities.

a. Check Bridge Inspection Report for any existing utilities (available in Bridge Conditions).

b. Check utility file for any existing utility permits or franchises and possible as-built plans.(Currently maintained in the Bridge Management Section.)

c. Any existing utilities on the same side of the structure as the proposed utility should beshown on the proposal.

d. Obtain as-built plans from bridge vault if not in an existing utility file.

3. Review the following with all comments in red:

• Layout with directions, SR no. and bridge no.

• Adequate spacing of supports.

• Adequate strength of supports as attached to the bridge (calculations may be necessary).

• Maximum design pressure and regular operating pressure for pressure pipe systems.

• Adequate lateral bracing and thrust protection for pressure pipe systems.

• Does the utility obstruct maintenance or accessibility to key bridge components. Check withthe Bridge Condition Section if in doubt.

• Location (elevation and plan view) of the utility with respect to pier footings or abutments. Iftrench limits encroach within the 45° envelope from the footing edge, consult the MaterialsLab.

8.3.5 - 8 July 1994



Figure 8.3.5-2

July 1994 8.3.5 - 9



Figure 8.3.5-4

8.3.5 - 10 July 1994



• Force mains or water flow systems may require encasement if they are in excavations belowthe bottom of a footing.

4. Write a preliminary IDC or letter of reply for the supervisor to review before final typing. Uponhis approval, include your initials at the bottom of the IDC or letter so that a copy will bereturned to you indicating that the package has been accepted and sent out.

5. Stamp and date the plans using the same date as shown on the IDC.

6. Create a file folder:

a. Bridge no., name, utility company or type of utility, and franchise or permit number.

b. One set of approved plans and possibly one or two pages of the original design plans ifnecessary for quick future reference. (Previous transmittals and plans not approved orreturned to correction should be discarded to avoid unnecessary clutter of the files.)

c. The letter of submittal and a copy of the IDC or letter of reply after it has been accepted.

7. Give the complete package to the section supervisor for review and place the folder in the utilityfile after the review.

8-3-5:V:BDM8

July 1994 8.3.5 - 11


Miscellaneous Design Bridge Details

8.4 Bridge Details

8.4.1 Expansion Joints

Expansion joints or bridge deck joints are designed to accommodate cyclic and long-term structuremovements, to support and to provide smooth and quiet passage of traffic, to prevent water runoff fromdamaging the supporting structural elements, and to have a long service life.

For new construction, the criteria shown below should be followed for expansion joints.

Steel Bridges: Use L-Abutments with expansion joints at ends for multiple-span bridges.Expansion joints may be eliminated for single span bridges with the approvalof the Bridge Design Engineer. Whenever the bridge skew exceeds 30 degrees,consult the Expansion Joint Specialist and the Bridge Design Engineer forrecommendations and approval.

Note: The use of intermediate expansion joints should be avoided,where possible.

All Concrete Bridges: Use L-Abutments with expansion joints at ends when the bridge length ex-ceeds 400 feet. Whenever the bridge skew exceeds 30 degrees, consultthe Expansion Joint Specialist and the Bridge Design Engineer forrecommendations and approval.

Note: The use of intermediate expansion joints should be avoided,where possible.

Expansion joints are not normally designed for seismic movements. The assumption is that damagewill occur after a seismic event; and the joint will be repaired. If seismic isolation bearings are used,the expansion joints must accommodate the seismic movement so that the bearings perform properly.

The following design, specification, and shop plan review criteria cover the bridge deck joint systemsmost commonly used in Washington State.

A. Design

Bridge deck joints are classified as small, medium, or large movement joints. The total movementto be accommodated at the joint determines the classification:

Small Movement Joint Total Movement ≤ 13/4″Medium Movement Joint 13/4″ < Total Movement ≤ 5″Large Movement Joint 5″ < Total Movement

1. Small Movement Joints

Compression seals have most frequently been used for small movement range joints.Compression seals are continuous preformed elastomeric sections, typically with extrudedinternal web systems, installed within an expansion joint gap to effectively seal the joint againstwater and debris infiltration. Compression seals are held in place by mobilizing friction againstadjacent vertical joint faces. Hence, design philosophy requires that they be sized and installedto always be in a state of compression.

Silicone sealant joints and asphalt plug joints have both been used as alternatives to compressionseals in recent years, particularly on rehabilitation projects. This office is continuing to monitorthese systems in order to assess their long term performance. Consult the Expansion JointSpecialist for the current design policy on each of these systems.

August 1998 8.4.1-1



An asphaltic plug joint consists of polymer modified asphalt (PMA) installed within a blockoutover a steel plate. The steel plate spans across the expansion gap to retain the PMA during itsinstallation. In theory, asphaltic plug joints provide a smooth seamless riding surface for traffic.This office has used asphaltic plug joints for motion ranges up to 1 inch.

Application guidelines must be carefully followed to assure successful performance of asphalticplug joints. They should not be used at joints subjected to differential vertical movements (forexample, longitudinal separation joints). They should not be used for joints having large skewangles, joints subjected to large rotations, or in situations where the total height of the polymermodified asphalt above the steel plate is less than 2 inches. The PMA has a tendency to creepout of the blockout, particularly within wheel lines. This tendency is amplified by any horizontalloading applied to the asphaltic plug joint. Therefore, asphaltic plug joints should not be used insituations where the adjacent pavement is subjected to significant acceleration or deceleration(off ramps, traffic signals). Overall, asphaltic plug joints have demonstrated erratic performancein Washington State. Consult the Expansion Joint Specialist for current policy and guidelines.

Silicone sealants are generally poured in place directly over a foam backer rod placed in theexpansion gap. A primer may be sprayed onto the vertical faces of the concrete or steel substrateto enhance bonding of the sealant. Several different chemical variations of silicone sealant areavailable depending upon the joint geometry and construction requirements. The primarydifferentiating characteristics of the silicone sealants are viscosity and curing time. A commonlyused silicone sealant for rehabilitation projects is the two-part Dow Corning 902 RCS sealant.This product is self leveling, can bond to itself, and cures very quickly. In situations were therapid curing and self leveling properties are not required, less expensive silicone sealants can beused. The completely cured silicone sealant joint can accommodate tensile movements of up to100 percent and compressive movements of up to 50 percent of the sealant width at installation.This office has used silicone sealant joints for motion ranges up to 1 inch. A minimum recess isrequired from the top of the pavement to the top of the silicone sealant in order to prevent tiretraffic from contacting and debonding the sealant from the substrate. Consult the ExpansionJoint Specialist for guidelines and example details.

Polymer concrete headers are generally recommended at compression seal joints and at siliconesealant joints. Polymer concrete provides tensile strength and toughness to resist traffic impact.Generic and proprietary polymer concrete formulations are available. Proprietary elastomericconcretes are occasionally used in lieu of polymer concrete to further enhance impact resistance.Consult the Expansion Joint Specialist regarding patent infringement issues which may resultwhen generic polymer concrete is used in combination with a Dow Corning silicone sealant.

a. Design Criteria

(1) When more exact temperature data is not available, use the following designtemperature ranges:

Concrete Structure 0° to 100°FSteel Structures (Eastern Washington) -30° to 120°FSteel Structures (Western Washington) 0° to 120°F

All plan dimensions are based on a normal installation temperature of 64°F inaccordance with the WSDOT Standard Specifications.

8.4.1-2 August 1998



(2) Use a shrinkage coefficient 0.0002 for normal weight concrete. The calculated shrinkageis multiplied by a shrinkage factor, µ, to account for anticipated future shrinkage thatoccurs after the joint is installed.

b. Compression Seal Size Determination

To function properly, seals must be compressed at all times, otherwise they will fall out.Generally, the compression range for bridge compression seals is 40 to 85 percent ofthe uncompressed width. All movement of the joint must be within this range. It isrecommended that compression seals not be used when the skew exceeds 45 degrees.

To determine the compression seal size (W) required, proceed as follows:

(1) Determine the total movement, Mt, along the bridge centerline:

Mt = Temp + Shrink + Other Movement = Total Movement (1)

where:

Temp = 12 L α ∆ TShrink = 12 L ,ß µOther Movement includes all other factors which affect movement.

α = Coefficient of thermal expansion: 0.000006 per degree Fahrenheitfor concrete 0.0000065 per degree Fahrenheit for steel

ß = Shrinkage coefficient for reinforced concrete: 0.0002 ft/ftµ = Shrinkage factor: 1.0 for Rat slabs, 0.8 for box girders and T-beams,

0.5 for prestressed-precast girder bridges, and 0.0 for steel bridgesL = Length of structure contributing to movement of the joint in feet

∆ T = Design temperature range

(2) Determine movements parallel to the joint, Mp, and normal to the joint, Mn(Figure 8.4.1-1):

Mp = Mt Sin θ (Movement parallel to the joint) (2)

Mn = Mt Cos θ (Movement normal to the joint) (3)

where: θ = skew angle

(3) Define the working range of joint width, A, in terms of required uncompressed sealwidth, W:

Width of joint opening, A, shall be:

A min = 0.4W = maximum compression of 40%(4)

A max = 0.85W = minimum compression of 85% (5)

A movement = 0.85W - 0.4W = 0.45W = movement rangenormal lo the seal (6)

February 2000 8.4.1-3



Skewed Expansion JointFigure 8.4.1-1

Assume a minimum midrange installation width at 64°F:

A install = 0.6W (7)

(4) Determine required compression seal size, W:

Seal width to accommodate movement parallel to the joint, Mp:

W = Mp/0.22 (8)

Seal width to accommodate movement normal to the joint, Mn:

W = Mn/0.45 (9)

Assume the seal is installed at a temperature of 64°F and the joint opening at installationplus the total opening movement does not exceed the maximum permitted joint opening(0.85W):

A max = A install + Cos θ [K(Temp) + Shrink + Other Movement] (10)

where: K = Temperature drop divided by temperature range:0.64 (64° to 0°F) for concrete bridges,0.53 (64° to 0°F) for western Washington steel bridges, and0.63 (64° to -30°F) for eastern Washington steel bridges.

Temp = Temperature movement previously defined.Shrink = Shrinkage movement previously defined.

Substituting Eq’s. (5) and (7) into (10), and solving for W yields the following formula:

W = 4(Cos θ)[K(Temp) + Shrink + Other Movement] (11)

Use a seal size based on the largest value of W from Eqs. (8), (9) and (11).

8.4.1-4 August 1998



(5) Determine width of joint opening at time of construction, A const:

A const = 0.6(W) + Cos θ[12(L)α] (64°F - Tc) (12)

where: Tc = Ambient air temperature during construction of joint,in degrees Fahrenheit.

(6) When the computed seal size required exceeds the maximum seal widths noted in the“Compression Seal table” (see Appendix 8.4-A1), a joint providing greater movementcapacity is required.

(7) See Appendix 8.4-B I for example.

2. Medium Movement Joints

Strip seals are the first choice for joint movements greater than 13/4 inch and less than 5 inch.Strip seals are available in whole inch sizes from 2 inches to 5 inches, with 3 inches and 4 inchesas the most widely used.

a. Design Criteria

(1) In addition to the design criteria for small movement joints, all factors which affectmovements, including rotations, should be considered in dimensioning the joint. Theseinclude: creep, shrinkage, stage construction, construction tolerances, temperature range,bearing type and direction(s) of permitted movements, skew, and external restraints.

(2) Earthquake movement need not be considered for medium movement joints exceptwhen required for structure performance. For example, when using base isolationbearings, the superstructure must be allowed to displace without hitting the backwall.So, to ensure proper functioning of the bearings, a larger size joint than normal maybe required.

(3) When designing for existing joint rehabilitation or joint modifications, the designershould review as-built plans, past inspection reports for recorded joint movements, andmeasure the existing joint opening at several locations (note the structure temperaturewhen taking field measurements).

(4) Joints with 0 to 30 degree skew should be designed for the movement along thecenterline of the bridge. For skews greater than 30 degrees, consult the Joint Specialist.

The skew angle can influence strip seal performance. At large skews, large size stripseals can buckle and invert above the top surface of the steel edge rails. Therefore, asystem which provides the most movement capacity at a 0 degree skew angle may notalways provide the most movement capacity at greater skew angles.

(5) The preferred maximum allowable opening, measured in the direction of traffic, formedium movement expansion joints is 4 inches. This maximum limitation improves theride, reduces impact, and reduces the hazard to motorcyclists and bicyclists. The use ofany medium movement joint with an opening greater than 4 inches must be approved bythe Joint Specialist.

(6) Adjustment of the joint to compensate for the temperature at time of installation must beallowed. Generally, ambient air temperatures, taken in the shade, are used in adjustingthe joint at the time of installation.

August 1998 8.4.1-5



To facilitate installation of the seals, size the joint and position the edge beams so thatthe joint opening, normal to the joint, is equal to the minimum installation width at64°F. The seal can now be installed at any temperature below 64°F. Generally, allstrip seals have a minimum installation width of 11/2 inch normal to the joint.

(7) Use only steel shapes, plates, reinforcement, and anchors in edge beams. No aluminumparts shall be permitted.

(8) Use continuous seals for the full width of the bridge including parapets. No splices inthe seals other than one preapproved manufacturer’s shop vulcanized field splice perseal is permitted. No welding of shipping clamps, lifting straps, hooks, or temperatureadjusting devices shall be permitted. Temporary threaded studs, used for positioningand securing the edge beams during placement of concrete in the blockout, may betack welded to the edge beams and removed later by grinding.

(9) Carefully detail joints at sidewalks and parapets with respect to leakage, constructibility,and maintenance. If required by the manufacturer, strip seal extrusions may be split atthe curb or traffic barrier. Do not use steel shapes with horizontal projecting legs in thecurb or barrier region. Steel sliding plates shall be used in sidewalk areas to preventseal damage.

(10)Many anchorage systems of bridge joints in the medium movement range have failedbecause of high impact from wheel loads. These dynamic impact loads can be as muchas 70 percent greater than a static wheel load. For an HS25 vehicle, the maximumstatic wheel load is 20 kips per wheel without impact (1.25 times 16 kips per wheel).Anchorage systems must resist the rebound effect of the impact wheel loads.

(11)Bolt-down panel elastomeric joints were widely used in the past. When the bolts holdingthe panel failed, the panel was no longer restrained and a safety hazard to motorists(particularly to motorcyclists) was created because of the loose panel in the roadway.In addition to continued maintenance because of loose hold down bolts, these jointswere subject to snowplow damage. Do not use bolt-down elastomeric expansion joints.

b. Strip Seal Size Determination

(1) Starting with a temperature of 64°F, calculate the total opening movement, using thelength of the bridge along centerline, due to:

(a) Temperature

64°F to 0°F for concrete superstructures, and64°F to either 0°F or -30°F for steel superstructure.

(b) Shrinkage

Use a shrinkage coefficient of 0.0002 for normal weight concrete and a shrinkagefactor, pL, to account for anticipated future shrinkage that occurs after the joint isinstalled. Shrinkage is not required for rehabilitation projects where shrinkage ofthe superstructure has already taken place.

(2) Starting with a temperature of 64°F, calculate the total closing movement, along thebridge centerline, due to:

8.4.1-6 August 1998



(a) Temperature

64°F to 100°F, for concrete superstructures, and64°F to 120°F for steel superstructure.

(b) Minimum Opening Required for Seal Installation at 64°F

For calculation purposes, strip seal joints have been classified as either Group 1 orGroup 2 (see Appendix 8.4-A1).

A Group 1 joint requires a 1/2 inch gap between steel supporting elements at fullclosure so the seal is not damaged. The minimum opening normal to the joint is1 inch (e.g., minimum installation width less 1/2 inch minimum gap equals 1 inch).

A Group 2 joint permits full closure between steel supporting elements. Generally,Group 2 joints use a 11/2 inch minimum opening normal to the joint.

(3) Determine the required strip seal size by adding the total opening movement and thelarger of either the total closing movement or the minimum installation width.

(4) Determine the “G” dimension at time of edge beam installation

Show the construction width, G, at time of edge beam installation for temperaturesof 40°F, 64°F, and 80°F. Note that the “G” dimension is normal to the joint and ismeasured from face-to-face of edge beams. This helps the Contractor adjust the edgebeams during construction at different temperatures.

(5) See Appendixes 8.4-B2 through 8.4-B4 for typical design calculations.

3. Large Movement Joints — Modulas Expansion Joints

Modular joints are the first choice for movements greater than 5 inches. See the Expansion JointSpecialist for approved manufacturers and latest plan details.

a. Design Criteria

(1) Where applicable, the “Design Criteria” for medium movement joints applies to largemovement joints where the total movement is expected to exceed 5 inches.

(2) All seals must be continuous across the full roadway width, including curb and trafficbarriers. The entire joint shall be shipped completely preassembled to the job site. Nosplices in the seals other than one preapproved manufacturer’s shop vulcanized spliceper seal is permitted.

(3) The expansion joint system must be durable enough to resist the damaging effects oftraffic impact, abrasion, and snowplow damage.

(4) Joints should be designed for the total movement normal to the joint (e.g., the productof the total movement along the centerline of the bridge and the cosine of the skewangle) plus a 15 percent factor of safety, which allows for unpredictable non-seismicmovements. Try to avoid skews greater than 30 degrees for modular expansion joints.

(5) The movement allowed per sealing element shall be limited to 3 inch maximum. Themaximum gap between centerbeams or centerbeam and edge beams is 31/2 inches at theminimum temperature condition. The purpose of limiting the gap is to reduce the wheelimpact on the joint system and subsequent wear on supporting elements.

August 1998 8.4.1-7



(6) All supporting structural members shall be designed for the limit states, wheel loads,impact percentages, and distribution factors specified in the Special Provision “ModularExpansion Joint System.” These requirements are derived from research summarized inNCHRP Report 402 “Fatigue Design of Modular Bridge Expansion Joints,” NationalAcademy Press, Washington, D.C., 1997.

(7) In the past, box seals were used; the current practice is to use factory installed stripseals. Consideration should be given to using reinforced strip seals.

(8) To allow for replacement of damaged seals or seal installation under stage construction,all seals shall be removable and replaceable at 64°F per manufacturer’s recommendedprocedure. Generally, this is accomplished by jacking the center beams apart or to oneside. This creates a larger gap between center beams for seal removal and reinstallation.

For retrofit or stage construction applications, this procedure may be both timeconsuming and expensive. It may be more convenient to oversize the joint so that theseals can be installed at the minimum manufacturer’s installation width at 64°F. Thedesigner should work closely with his Supervisor and the Expansion Joint Specialistto determine the best solution considering the time constraints of stage constructionand increased cost.

(9) Access to the modular expansion joint components shall be provided so that repairs,adjustments, and replacement of components can be made.

(10)Only manufacturers who have satisfied the prequalification requirements stipulated inthe Special Provisions “Modular Expansion Joint System” will be permitted to supplymodular expansion joints. This Special Provision includes requirements for fatigueresistance characterization, testing, and design.

(11)Traffic barrier cover plates should be designed for removability.

b. Modular Expansion Joint Size Determination

Modular joints are sized according to movement rating (MR) and are in increments of3 inches beginning with a 6-inch modular system. The movement rating is equal to theproduct of the number of seals and the 3 inch maximum allowable movement rating of eachseal. For example, a three seal modular joint with three strip seals, each with a maximumallowable movement rating of 3 inches, has a total movement rating of 9 inches.

(1) “G” Dimension and Temperature Setting

The “G” dimension, face-to-face of edge beams, helps the Contractor adjust the jointassembly in the field for different temperatures. This dimension is normal to the jointand is dependent upon two variables:

(a) Flange width of center beams.

(b) Minimum gap per seal permitted by the manufacturer at full closure.

Therefore, Gmin and Gmax can be determined from:

Gmin = (N-l)(B) + (N)(MG) (13)Gmax = Gmin + MR (14)

8.4.1-8 August 1998



where: B = Center beam flange widthMR = Total movement rating of the joint system

N = Number of seals = MR/MSN-1 = Number of center beamsMG = Minimum gap per seal permitted at full closureMS = Maximum permitted movement rating per seal = 3 inch maximum

In addition to the Gmin and Gmax dimensions, “G” dimensions should be shown forstructure temperatures of 40°F, 64°F, and 80°F following the same procedure as usedfor strip seals. These dimensions are normal to the joint. For large movement joints,in concrete bridges, consideration should be given to using structure temperatures indetermining construction openings at 40°F, 64°F, and 80°F, because of the time lagbetween ambient air temperature and structure temperature. For long span bridges,where temperature is not constantly monitored as part of the construction procedure,temperature movements require more attention. Consideration should be given to usinga two- or three-day running mean temperature for setting joints during construction.

(2) Generally, large movement joints are not designed for earthquake movements. It is feltthat the joint will suffer damage in a seismic event and have to be rebuilt. However,consideration may be given to accommodating some earthquake movement. Thedesigner should work closely with his Supervisor and the Expansion Joint Specialistto determine the best combination of cost versus design movement.

(3) See Appendixes 8.4-B5 through 8.4-B8 for typical design calculations.

4. Large Movement Joints—Steel Finger Joints

Prior to the development of watertight modular joints, finger joints were used to accommodatelarge movements. However, these joints do not provide a watertight seal and are not currentlybeing specified. Consult the Joint Specialist before selecting this type of joint.

These joints are open-type, either cantilever or propped cantilever steel tooth plates. The toothplates can be cut from a plate l1/2 inch thick for movements up to 5 inches, but for larger move-ments, it is preferable for tooth plates to be cast or fabricated by welding. The teeth should haveadequate transverse and longitudinal stiffness to avoid chatter under traffic. The design shouldalso accommodate differential deflection, rotation, or settlement across the joint. The steelfingers should have the top surface parallel to the roadway grade, but tapered downward slightlyto prevent snowplow damage. The steel fingers should also be stress relieved to prevent warping.Additional requirements suggested by the FHWA include:

(a) Limit deck surface openings in finger joints to permit safe operation of motorcycles.

(b) Where narrow bicycle tires are anticipated, use special floor plates in the shoulder area.

(c) Limit the minimum joint opening in the longitudinal direction to 1 inch.

(d) At the maximum joint opening, the teeth should overlap at least 2 inches.

(e) Elastomeric troughs should be provided under the joint to protect the structure below.Reinforced elastomeric material for troughs should have a low durometer (50 or 60) andbe at least 3/8 inch thick. The troughs should be continuous across the full width of thebridge including the curb and parapet area and sloped at least 1 inch per foot to prevent

August 1998 8.4.1-9



sedimentation. However, the slope may vary depending on the expected rainfall and debris ateach location. The troughs should be attached in a secure manner with a minimum of 5/8-inchdiameter bolts at 18-inch centers.

The designer should avoid specifying finger joints for new construction. However, they maybe needed where snowplow use is extensive or where widening of an existing structureprecludes the use of any other joint system.

B. Specifications for Bridge Deck Joints

Bridge deck joints shall be specified as follows:

1. Specify only approved manufacturers that provide good field performance and service. Do notspecify “or an approved equal.”

2. A single manufacturer (sole source) may be specified if the designer determines that their systemis the only one that can satisfy the design criteria. Furnish justification to the SpecificationsSection and check with the Joint Specialist. Approval will have to be obtained from the FHWAby the Bridge Design Engineer before a sole source can be specified.

3. Specify quality assurance requirements, material specifications, design requirements, fabricationrequirements (e.g., welding, personnel requirements, inspection, testing), acceptance criteria,corrosion protection, and payment.

4. Specify that the manufacturers of modular joints or finger joints, be certified under the AISCQuality Certification Program (Simple Steel Bridges). For all joints, specify that weldinginspection shall be done by certified welding inspectors under AWS QC1, Standard forQualification and Certification of Welding Inspectors. Personnel performing nondestructivetesting (NDT) shall be certified as NDT Level II under the American Society for NondestructiveTesting (ASNT) Recommended Practice SNT-TC-1a.

C. Reviewing Shop Plans

1. Review the shop plans to ensure that they conform with the Contract Plans and SpecialProvisions regarding the following information

a. Plan and elevation of the joint.

b. Complete details of all components and sections showing all materials incorporated inthe joint.

c. All AASHTO or other material designation and method of corrosion protection.

d. Movement rating. HS 25 live loading plus impact. Behavior on skew, if present.

e. Opening dimensions at 40°F, 64°F, and 80°F for setting the joint. Note on the shop planswhether these temperatures are structure temperatures or ambient air temperatures takenin the shade.

f. Installation procedures, including any required services by a manufacturer’s fieldrepresentative.

g. Consideration of weld details in areas of stress concentration, welding procedures toinclude pre- and post-heat, and methods proposed by the manufacturer to prevent weldinduced cracks.

8.4.1-10 August 1998



h. Prohibition of temporary lifting, temperature, and construction adjustment devices that arewelded to the centerbeams or edge beams, except for threaded studs used to support stripseal joints. Threaded studs should be removed by grinding and an appropriate corrosionprotection system applied to the steel affected by grinding.

i. Manufacturer’s part numbers, so replacement parts can be easily identified and ordered.

j. Anchorage details, blockout size to facilitate placement of concrete, method of supportduring placement of deck concrete, and all blockout reinforcing steel.

k. Treatment of curbs, sidewalks, parapets, and traffic barriers (to include the non-traffic side)with respect to leakage and maintenance.

1. Ease of removal and handling of traffic barrier cover plates by two persons without speciallifting equipment.

m. Minimum radii permitted by the AISC for cold bending steel traffic barrier cover plates.

n. Design calculations for all structural elements of modular expansion joints. All calculationsshall satisfy the requirements of the Special Provision “Modular Expansion Joint System.”See the Expansion Joint Specialist for sample calculations.

2. Provide the following information to the Expansion Joint Specialist for performance tracking andmaintenance purposes:

a. Contract Number/Bridge Number.

b. Location.

c. Manufacturer.

d. Type of Joint.

e. Type of Extrusion/Steel Shape Designation.

f. Seal Size/Manufacturer’s Designation.

g. Approved By/Date Approved.

D. Other Considerations

1. Maintenance

During design, consideration should be given to maintenance of the joints. For large movementjoints, parts availability, replaceability, and access provisions should be considered. The designershould consult with the Expansion Joint Specialist on the maintenance and durability of themodular joints.

2. Widening and Rehabilitation of Bridges

a. For the rehabilitation of bridges, existing joints and structure layout should be studiedto determine if existing joints can be eliminated. It will be necessary to determine whatmodifications to the structure are required to provide an adequate and functional systemwhen existing joints are eliminated.

b. Consideration should be given to proper anchorage of edge beams for wheel impact loads.

P:DP/BDM89807-0802

August 1998 8.4.1-11



8.4.2 Drainage Design

A. General

Even though it is rare that poor drainage is directly responsible for a structural failure, it still mustbe a primary consideration in the design. Poor drainage can cause problems such as ponding on theroadway, erosion of abutments, and deterioration of structural members. Most of the problems can beprevented by collecting the runoff and transporting it away from the bridge. Proper geometrics duringthe preliminary stage is essential in order to accomplish this. The Hydraulics Section recommendsplacing the bridge deck drainage off of the structure. So the Bridge Design Section has adopted thepolicy that all expansion joints will be watertight.

B. Geometrics

Bridges should have adequate transverse and longitudinal slopes to allow the water to run quicklyto the drains. A transverse slope of .02′/ft. and longitudinal slope of 0.5 percent for minimum valvesare adequate. Avoid placing sag vertical curves and superelevation crossovers on the structure whichcould result in hydroplaning conditions or, in cold climates, sheets of ice from melting snow. The useof unsymmetrical vertical curves may assist the designer in shifting the low point off the structure.

C. Hydrology

Hydrological calculations are made using the rational equation. A 10-year storm event with a5-minute duration is the intensity used for all inlets except for sag vertical curves where a 50-yearstorm intensity is required.

D. On Bridge Systems

In some cases, such as box girder structures, a bridge drainage system is required for the structure.The first selection is to place 5-inch diameter pipe drains which have no bars and drop straight tothe ground. At other times, such as for steel structures, the straight drop drain is unacceptable and apiping system with bridge drains (see appendix) is required. The minimum piping diameter shouldbe 6 inches with no sharp bends within the system.

E. Construction

Bridge decks have a striated finish in accordance with the Standard Specifications listed below,however, the gutters have an untextured finish (steel trowel) for a distance of 2 feet from the curb.This untextured area provides for smooth gutter flow and a Manning n value of .015 in the design.

Standard Specification Section 6-02.3(10) — Bridge Decks

Standard Specification Section 5-05.3(11) — Approach Slabs

P:DP/BDM89807-0802

August 1998 8.4.2-1



8.4.2-2 August 1998



8.4.3 Bridge Bearings

A. Purpose

The purpose of a bridge bearing is to support the superstructure at a constant elevation, to carry allforces from the superstructure into the substructure, and to allow necessary superstructure movementsto take place.

B. Forces to Be Resisted

Bridge bearing reactions can come from any of the forces associated with bridge loadings. Theseforces can be combined into the basic loading vectors described below.

1. Vertical Force

This force can be considered to act directly through the center of the bearings. It is normallymade up of dead load and live load. This force is resisted by bearing against the concrete ofthe pier cap at the reduced stress values specified in AASHTO design specifications forsuch bearing.

2. Transverse Force

This force acts normal to the centerline of the bridge in a horizontal direction at the top of thebearing. It is made up of wind, earthquake, and other horizontal forces, and must be resistedby keys, anchor bolts, pintles, or other suitable means. In some cases, girder stops may be usedto resist this force, in which case the bearing itself need not resist it. Friction on the stop mayrequire a “stop bearing.” The transverse force will develop a moment within the bearing itself,which is equal to the product of the force times the height of the bearing. This moment maybe significant for tall bearings and should be included in the analysis. For “stop bearings,”see Section 8.4.3D5.e.

3. Longitudinal Force

This is any horizontal force acting parallel to the centerline of the bridge, including thermalmotion forces and forces due to concrete shrinkage. Longitudinal forces generally will not bedeveloped in an expansion bearing. Curved bridges require special consideration. Expansionbearings may, however, develop significant longitudinal forces due Lo sliding or rolling friction,shear deformation forces in neoprene bearings, and so forth. Where thcse forces may exist, theymust be accounted for in the design.

4. Uplift Forces

With the exception of elastomeric pads, usual bearings shall be designed for uplift forces dueto earthquake in an amount equal to 10 percent of the vertical dead load reaction of thesuperstructure.

5. Other Forces

Bending moments in each of the three planes may be developed by a particular structure.The resulting forces induced in the bearings should be considered and accounted for in thedesign when they are significant.

August 1998 8.4.3-1



C. Movements

Allowance must be provided in the design of each structure for all anticipated movements. Normallythese movements will be primarily in the longitudinal direction. For extremely wide structures,transverse movements may also be significant. The following material provides guidance for design.

1. Temperature

Expansion and contraction due to temperature change will occur throughout the life of thestructure. Proper temperature expansion provisions are essential to ensure that the structure willnot be damaged by restricting such movements Where these movements are restrained due topoor design or construction, extremely high forces may be imposed on other portions of thestructure. It should be noted for setting bearings that the mean annual temperature throughout thestate of Washington is approximately 50°. Standard construction specifications specify a “nor-mal” temperature of 64°, which is the temperature at which it is assumed steel will be fabricated,expansion joints and bearings set, etc. This means that the plan dimensions are taken to be correctat 64°. Except for elastomeric bearings, bearing setting dimensions should be shown on the plansfor a range of temperatures other than 64°. Figure 8.4.3C1-1 gives additional temperature data forspecific areas. The National Weather Service has information on other areas.

30-Year Extreme Temperatures

High Low

Olympia 100 -7Spokane 108 -25Yakima 110 -25

Mean Annual Temperature

Olympia 50 1Spokane 47.3

Typical Temperature Ranges in WashingtonFigure 8.4.3C1-1

October 1975

a. Steel Structures

In the absence of more exact temperature data, use the following design temperature ranges:

Eastern Washington: -30° to 120°FWestern Washington: 0° to 120°F

Center bearings at 50°F. Specify bearing setting temperatures about a mean constructiontemperature of 64°F.

b. Concrete Structures

Concrete structures possess more thermal mass than steel structures. Consequently, thetemperature extremes to which they are exposed are less than those of steel structures. Inthe absence of more exact temperature data, design temperatures for concrete structuresthroughout Washington State shall be assured to range from 0° to 100°F.

8.4.3-2 August 1998



Sample Temperature versus Motion Graph for a Concrete Box Girder BridgeFigure 8.4.3Clb-l

October 1975

2. Shrinkage

All concrete tends to shrink during curing unless special additives are used. See 5.1.1A. Thedesign of bearing elements shall accommodate this shrinkage movement. If the calculatedmovements are significant, bearings for concrete structures (except elastomeric bearings) shouldbe installed in the direction of the “hot” position (opposite to anticipated shrinkage) in order tobe in the “normal” position after shrinkage has taken full effect. Such adjustment must be shownon the plans.

3. Creep

In certain structures, creep associated with applied loads must be taken into account in thebearing details. This is particularly true for post-tensioned bridges where the prestressing forcewill cause an immediate clastic shortening of the structure and an associated long-term creepeffect. On very unusual structures, this effect could result from dead load sidesway forces.Similar to the adjustment for shrinkage, bearings should be designed and installed to compensatefor this effect.

August 1998 8.4.3-3



4. Earth Pressure

In several structures which have been designed and constructed, unanticipated earth pressuremovements have resulted in tilted rocker bearings, closed expansion joints, and jammed jointopenings. Where it is anticipated that such action may occur, bearings should be designed sothat they can be readjusted in position, if necessary, to account for such motions. Similar actionshould be considered where settlements may cause bearing misalignment. Consideration shouldbe given to providing jacking pads to minimize the labor involved in making such adjustments.In any case, bearings should be designed so that if these motions occur, they will not result indamage to the structure.

5. Force/Motion Combinations

In the process Of bearing design, the question often arises as to what position of the bearing toassume for design. Usually the bearing will be designed in the “normal” position for dead loadand live load. Design will include an analysis of bearing elements at high and low temperaturepositions utilizing the load factors normally associated with those temperature conditions.Similar procedures should be used for other motion conditions.

6. Replacement Considerations

Whenever possible, bearings shall be detailed, fabricated, and installed to facilitate inspection,maintenance, and eventual replacement if required. Jacking points shall be identified on thecontract drawings so that bearings can be reset, replumbed, or replaced to mitigate constructioninduced displacement.

7. Construction Tolerances

Care should be taken that the design includes adequate construction tolerance for settingbearings.

D. Bearing Details

The following are some specific design criteria with discussion for various bearing types and details(see Figure 8.4.3C-1).

1. Fixed Bearings

The bearings are called “fixed” because they do not allow longitudinal motion. They are nor-mally not fixed in the static sense but are actually pinned, in that they allow rotational motionin the longitudinal direction (see Figure 8.4.3C-1). Base plate pressures on the concrete aregoverned by AASHTO Specifications. Bending stress in the base plate of all steel bearings shallnormally not exceed 24,000 psi in order to avoid use of thin plates and the resultant concentrationof loads due to flexural distortions of the plate. Higher plate stresses may be allowed if a morerigorous analysis is used. The body of the bearing is normally cast steel or a weldment. Nor-mally, castings will be specified only where the bearings will be duplicated several times dueto the high cost of the pattern.

Forces in the longitudinal direction are assumed to act through the center of the pin, and themoment applied to the base plate is the horizontal force times h. Forces in the transverse direc-tion (along the axis of the pin) may be assumed to act on the bearing in double bending. That is,the moment applied to the base and to the pin along its length is equal to the force times h/2. Thebase plate must be capable of transmitting the horizontal forces to the concrete through positive

8.4.3-4 August 1998



means. This may include anchor bolts, shear lugs, or other suitable devices. Normally, frictionalone will not be considered to be adequate. Webs of the body of the bearing will be designedtaking into account the minimum thickness requirements for steel plates.

Bearing DetailsFigure 8.4.3C-lOctober 1975

2. Rocker Bearings

These bearings are intended to allow the end of the structure to move longitudinally along ahorizontal line. They are usually used for movable bearings supporting very large loads. The baseplate of these and of all movable bearings shall be placed level in order to avoid the tendency forthe bridge to move down slope. AASHTO equations are used to select an appropriate line bearingvalue and a dimension for the rocker radius. Sufficient clearance must be maintained between theedges of the top and bottom bearing blocks to allow the bearing to rotate freely at the extremesof motion. Pintles are always used with thcse bearings to prevent “walking” of the rocker on thebase plate and to resist transverse horizontal forces. The line bearing force values should bebased on a net contact length, deducting the pintle widths.

The line bearing values should take into account the increase in line pressure due to transverseloads when the loading combination being considered contains such loads. Moment at thebearing line of the rocker due to transverse loads can be developed using assumptions similar tothose noted for fixed bearings. Base plate design consists of selecting a plate thickness to satisfythe strength requirements shown in Figure 8.4.3C-1. The strength of the plate ends beyond theend of the rocker may require additional investigation. Provision must be made to hold down therocker to the base plate for earthquake uplift requirements. The designer should be aware of thelongitudinal horizontal force which may be developed through pin friction. That force is equal toP w/R, where u is the steel friction coefficient (could be taken as 0.7 for the dry static condition),P the load, and r and R the radius of the pin and rocker respectively.

Other design provisions are similar to those for fixed bearings.

August 1998 8.4.3-5



3. Roller Bearings

These bearings are simpler than rocker bearings, but due to the smaller radius are suitable forcarrying only moderate loads. These bearings are limited to a maximum of about 7 inches inroller size due to availability of bar stock. They are normally made from finished roller stock,but may be manufactured from thick plates (see Figure 8.4.3C-l). Yield points to 70,000 psimay be specified in order to keep the line bearing values within AASHTO allowables. If bearingplates and rollers are fabricated from steels with different yield strengths, the line bearing valuewill be controlled by the lowest yield strength. Pintles are required at both the top and bottom ofthe roller. Office practice is to not allow roller nests (multiple rollers in one bearing) except fortemporary bearings. Roller nests do not allow rotation of the beam end (unless special pins andguides are used) and are difficult to maintain. For additional criteria, see “fixed bearings” and“rocker bearings.”

4. Sliding Bearings

These bearings rely on a reduced coefficient of friction between the two contact surfaces to allowlongitudinal bearing motion. These bearings must be used in combination with a device whichwill allow beam end rotation. This device can be curved sliding surfaces, neoprene pads, or pins.Numerous bearing materials and configurations are possible. Sliding materials may be Tronze,“Teflon,” “Lubrite,” stainless steel, or other patented materials. Many combinations of the aboveare possible. Sliding bearings will always develop significant horizontal longitudinal forces, andthese forces must be accounted for in the design. Reasonable friction coefficients must beselected for the particular materials selected.

5. Elastomeric Bearings

An elastomeric bearing is fabricated wholly or partially from either natural rubber or neoprene.Steel reinforced elastomeric bearings are reinforced with multiple steel shim plates vulcanizedbetween adjacent elastomeric layers. Elastomeric bearings rely on their inherent shear flexibilityto accommodate bridge movements in any horizontal direction. This shear flexibility alsoenhances their rotational capability. Steel shim plates limit the tendency for elastomer to bulgelaterally. Elastomeric bearings are commonly used on prestressed girder bridges and may beused on other bridge types. The cost of elastomeric bearings is relatively low compared tomost high-load multi-rotational bearings.

a. General Design Criteria

Design of elastomeric bearings shall be in accordance with the AASHTO specifications.Conventional elastomeric bearings are designed using the Method A procedure. High-loadelastomeric bearings are designed using the Method B procedure. The Method B designprocedure allows significantly higher average compressive stresses. These higher allowablestress levels are justified by an additional acceptance test, specifically a long-durationcompression test. Design criteria for both methods is based upon satisfying fatigue, stability,delamination, steel reinforcement yield/rupture, and elastomer stiffness requirements. Thedesign of a steel reinforced elastomeric bearing requires an appropriate balance of compres-sive, shear, and rotational stiffnesses. The shape factor, as defined by the steel shim spacing,significantly affects the compressive and rotational stiffness of the bearing. However, it hasno impact on the translational stiffness of the bearing or its translational deformationcapacity. Large rotations and translations generally require taller bearings.

8.4.3-6 August 1998



High-load elastomeric bearings (AASHTO Method B design) can provide economicalalternatives to lightly loaded high-load multi-rotational bearings. Additionally, theirflexibility provides some degree of seismic isolation which may reduce substructurecosts. Designers shall obtain the approval of the Bearings Specialist and the BridgeDesign Engineer in order to use high-load elastomeric bearings on a specific project.

The Standard Specifications states that elastomeric bearing pads shall conform to therequirements of AASHTO M 251 Plain and Laminated Elastomeric Bridge Bearings andthat internal shims shall be fabricated from ASTM A 570 Grade 36 (A 570M Grade 250)steel unless noted otherwise on the plans.

The minimum elastomeric bearing length or width shall be 6 inches (except for girder stoppads). Generally, all pads shall be 60 durometer hardness. Pads shall be laminated in 1/2 inchelastomeric layers with a minimum total thickness of 1 inch. For overall bearings heightsless than 3 inches, a minimum of 1/8 inch of side clearance shall be provided over the steelshims. For overall heights between 3 inches and 7 inches, a minimum of 1/4 inch of sideclearance shall be provided. For overall heights greater than 7 inches, a minimum of 1/2 inchof side clearance shall be provided.

Live load plus impact compressive deflection shall be limited to 1/16 inch. In determiningbearing pad thickness, it should be assumed that slippage will not occur. Bearing padthickness shall be no less than twice the maximum lateral deflection (see Figure 8.4.3D5a-1).The equations shown in b, c, and d below are approximations of this motion.

Section 8.4-B9 of Appendix B presents a reinforced elastomeric bearing pad design exampleusing the AASHTO Method A design procedure. Electronic spread sheet programs areavailable for designing high-load elastomeric bearings using the Method B design procedure.Reference 5 on page 8.99-1 provides additional guidance for the design of elastomericbearings.

b. Elastomeric Bearings for Precast Concrete Spans

For prestressed or precast concrete girder spans, it should be assumed that the beams maynot be placed at the “mean” temperature range. In addition, allowance must be made forhalf shrinkage.

Minimum Pad Thickness for Prestressed Girders = 2[3/4 (∆ Temp. Rise + ∆ Temp. Fall) +∆ 1/2 Shrink.]

March 2000 8.4.3-7



Figure 8.4.3D5a-lOctober 1975

c. Elastomeric Bearings for Cast-in-Place Concrete Spans

For cast-in-place concrete spans, it should be assumed that the temperature of concreteat time of casting is the normal temperature. However, allowance must be made forfull shrinkage.

Minimum Pad Thickness for Cast-in-Place Girders = 2 [∆ Temp. Fall + ∆ Shrink.],where temperature fall is the deflection corresponding to a temperature change of 45°.

d. Elastomeric Bearings for Steel Girder Spans

For steel girder spans, it should be assumed that the beams may not be placed at the “mean”temperature and design should provide for 3/4 of the total temperature range. No allowanceis needed for shrinkage.

Minimum Pad Thickness for Steel Girders = 2 [3/4 (∆ Temp. Rise + ∆ Temp. Fall)]

e. Girder Stop Bearing Pads

Where earth pressure on the back wall (end diaphragm) of skewed bridges or othertransverse loads must be resisted by girder stops, these stops must be capable of allowing theanticipated motion (see Article 9.3.2D and Figure 8.4.3DSe-l). The following procedure isrecommended for design of stop pads for skewed prestressed girder bridges for loads due toearth pressure on back walls.

Design Assumptions (Series 80, 100, and 120 Prestressed Girders Only)

Cold ClimateElastomeric Bearing Pads of 60 Durometer Hardness and 1/2-inch LaminatesT = 2 [3/4 (∆ Temp. Range) +1/2 (Shrink.)]Pad Width Equals 5 inches

8.4.3-8 August 1998



Girder Stop Bearing PadFigure 8.4.3D5e-l

October 1975

Procedure

The transverse load girder due to earth pressure plus live load surcharge pressure can bedetermined from the Spacing Chart on page 8.4-B14 of Appendix B. By entering this chartwith skew angle, girder series, and girder spacing (normal to girder), the transverse load pergirder F(Ep)T may be read on the right-hand side of the chart. Note: If F(Ep)T is less than2,200 pounds, no girder stop bearing pads are required since the girder bearing pad iscapable of resisting 2,200 pounds with a maximum transverse deflection of 1/8 inch.

If the Spacing Chart indicates that girder stop bearing pads are required, the requiredpad thickness can be obtained by entering the Pad Thickness Chart on page 8.4-B15 ofAppendix B on the left side with the bridge length (back to back of pavement seat). Thepad thickness should be rounded lo the next higher half-inch increment. The width of thegirder stop bearing pad is a constant 5 inches for series 80, 100, and 120 girders. The lengthof the pad is equal to three times the rounded “T.”

August 1998 8.4.3-9



By reentering the Pad Thickness Chart on the bottom with the pad thickness (from chartas rounded), F(Ep)T (from the Spacing Chart), and the number of lines of girders in theend span, the number of girders in the end span requiring girder stop bearing pads can beobtained. See the sample problem Appendix B Section 8.4-B12.

6. Preformed Fabric Pads

These pads can withstand large compression loads. They can provide for rotation. When usedin combination with a PTFE sliding surface, they will allow bridge movements in a horizontaldirection. When a PTFE sliding surface is specified, the PTFE sheet shall be 1/8 inch thick andshall be recessed 1/16 inch into 1/2 inch-thick steel plate that is bonded to the top of the fabric pad.They have been used on reinforced and post-tensioned concrete box girder bridges and can beused on other bridge types. The cost of bearings incorporating preformed fabric pads is relativelylow compared to most steel bearings.

a. Criteria

Maximum average allowable bearing pressure on the fabric pad is 1,200 psi at service load.

Maximum allowable concrete bearing pressure is determined by 1977 AASHTO Article1.5.26(3).

Maximum total load on bearing is 500 kips. If the design load exceeds this value, anothertype of bearing should be used.

Maximum bearing thickness is 4 inches.

b. Sample Problem

The following method is used to calculate the required dimensions of a preformed fabric padused in combination with a TFE sliding surface:

Maximum Edge Strain = Average Strain + Rotation

Where:

T = Pad ThicknessL = Pad Length (parallel to longitudinal axis of beam)R = Rotation due to loading plus construction tolerances

Allowance for Rotation = .015 Radians minimum (AASHTO)0.14 = maximum strain with edge stress of 2,000 psiAt 1,200 psi, strain = 10 percent or 0.10T

Hence:

0.14T = (0.10)T + L

2 (R)

T = 12.5LR

Given:

DL + LL + I = 260 kips/bearingRotation = 0.015 radiansAllowable Bearing Pressure for Fabric Pad = 1,200 psifc′ = 3,000 psi

8.4.3-10 August 1998



Solution:

Pad Area Required = 260,000 lbs./1,200 psi = 216.67 in2

Try a 20-inch-wide by 11-inch-long padArea = 220 in2

Check allowable concrete bearing pressure by AASHTO

Al = 20 inches × 11 inches = 220 in2

A

A2

1

= 1.42 ≤ 2

A2 = (20+6)(11+6) = 442 in2

Allowable Bearing on loaded area = fb

fb = (0.30f

c′ )

A

A2

1

Allowable fb = (.3) (3,000 psi) (1.42) = 1,278 psi> 1,200 psi

Allowable Bearing on the Fabric Pad Controls

Thickness of Pad:

T = 12.5LR = 12.5(11)(0.015) = 2.06 inches

Use Fabric Pad that is 20 inches by 11 inches by 21/4 inches

7. Combination Bearings

The bearing types which have been discussed above can be used in many combinations in orderto develop a satisfactory solution for a bearing problem. For instance, an elastomeric bearing maybe used to provide rotational ability when using a sliding bearing.

8. Patented Bearings

These bearings are available from several sources. They are quite expensive and have seldombeen used to date in Washington. In some cases, they may prove to be a good solution for heavilyloaded bearings. If used, care must be taken to ensure that the bearing actually supplied by theContractor meets all of the requirements of specifications.

9. Bearing Pins

Pins of the type shown schematically in Figure 8.4.3C-I, Fixed Bearings, are commonly usedwith many bearing types. Figure 8.4.3D9-1 shows a typical configuration of such a pin. The pindiameter and strength must be such that vertical loads can be adequately carried. This is normallynot a problem. The critical factor in pin design is the ability to carry transverse loads. Normally,in the figure shown, Diameter D2 is Y2 inch less than Dl. The transverse loads are carried fromthe top bearing plate to the bottom bearing plate by the inner ring of the upper bearing blockbearing against the washer and nut. This causes a bending plus axial tension stress in the threadedportion of the pin. This stress must not exceed that allowed for tension at the root of the thread.The position of the acting force may be taken as shown in Figure 8.4.3C8-1 by force “H,” half ofD2 from centerline pin. This is allowable because any slight bending of the pin will tend to movethe point of application of the force vector closer to the centerline. High strength bar steel shouldbe used where necessary to keep pin sizes reasonable. It is desirable to have pins fabricated of a

August 1998 8.4.3-11



steel with slightly different composition from the bearing blocks in order to avoid the possibilityof “freezing” of the bearing surface. Pins of ASTM A-108 grade 1040, 70,000 Y.P. have beenused successfully with A36 bearing blocks. The keeper rings used with such pins must beadequate to carry required uplift loads.

Typical Bearing Pin(For Use With Bearing Blocks)

Figure 8.4.3D9-1October 1977

10. Bearing Blocks

The bearing blocks for use with the typical pin described above are rectangular steel blocksmachined for the pin shaft and the keeper ring (see Figure 8.4.3D10-1).

Bearing BlockFigure 8.4.3D10-1September 1986

8.4.3-12 August 1998



Design of such blocks is nominal. The dimension “T,” least thickness to pin, must be largeenough to clear the nut and the weld on the end of the block. It must also be large enough toensure that the stress due to vertical pin loads is within allowables. If P is the vertical loadapplied to the bearing, R is the pin radius, W is the width of the load applying element, H is thehorizontal component of force developed by the pin curvature, and x and y are the distancesto the reactive forces P/2 and H then; the movement on the section dimensioned at “T” can beshown to be:

M = P T R W

2 8π π+ −

This moment tends to fail the bearing block in bending at this section and must be resisted by thestrength of the section at that point.

11. Anchor Bolts

Anchor bolts are used for all except neoprene bearings and perform a variety of functions. Thesefunctions may be:

Hold down uplift loads. Resist transverse loads from bearings. Provide temporary support forbase plate. Hold base plate firmly to erection shims.

Not all of these functions are necessarily needed in each design. Figure 8.4.3C11-1 shows asection through a typical anchor bolt. AASHTO Specifications give sizes for nominal anchorbolts. Where uplift loads must be held, the bolts must be adequate in length and the washer nutmust be of sufficient size and strength to engage a mass of concrete as specified in AASHTOunder “Uplift.” Where reinforcement in the concrete can be engaged, that reinforcement may alsobe considered to act to resist uplift Transverse loads cannot be resisted by the anchor bolts unlessthe void between the pipe and the bolt has been well grouted. The plans should require that thecontractor grout from the bottom of the pipe before grouting the bearing plate. An arrangementfor doing this must be shown on the plans. See Figure 8.4.3C11-2 for a typical detail. If theanchor bolt is to provide temporary support for a base plate, sufficient number of shims shall beused to carry the weight of the plate and other loads applied before grouting the plate. These mayinclude the weight of erected steel superstructure for structural steel bridges.

Anchor bolts shall be ASTM A 449 where strengths equal to ASTM A 325 are desired, andASTM A 354, Grade BD, where strengths equal to ASTM A 490 are desired.

For anchor bolt specifications and properties, see Bridge Instruction 7.1.8, Volume 1.

12. Construction Shims

The Construction Specifications require that bearings for steel bridges be supported on sets of21/2 inch square shims while the steel is being erected. The plans shall normally show how theseshims are to be placed in order to avoid overstressing the base plate or bearing webs or theconcrete of the pier.

13. Pintles

Pintles are used with rollers and rockers to carry transverse loads and to keep the moving partsin alignment. They are detailed so that transverse shear is applied at the surface of the parts.Their size must be such that these shear forces can be adequately resisted by the cross sectionof the pintle.

August 1998 8.4.3-13



Typical Anchor BoltFigure 8.4.3C11-1

Anchor Bolt as DetailedFigure 8.4.3C11-2

E. Orientation of Bearings

Movable bearings must be aligned to correspond to the actual direction of motion anticipated in thestructure. On curved and skewed structures, care must be taken that the details clearly show thebearings set relative to the actual axis of motion. On curved bridges, this axis may correspond witha chord between the two ends of the span. STRUDL may be helpful in establishing the exact motionvectors of the structure.

8.4.3-14 August 1998



F. Bearing Selection

Consideration should be given to elimination of bearings by making the superstructure continuouswith the substructure, where feasible. Engineering judgment based on the particular design conditionsshould govern bearing in any particular case. The following bridge types and bearings are commonlyused together:

Prestressed Girder Bridges - Elastomeric Bearings

Slab Bridges - Continuity or Elastomeric Bearings

Concrete Box Girder Bridges - Elastomeric BearingsRoller BearingsPreformed Fabric Pads w/TFE Sliding Surfaces

Steel Girder Bridges - Roller BearingsSliding BearingsRocker Bearings

Steel Truss Bridges - Rocker Bearings

Occasionally, other devices which act as bearings may be used. These include hinged columnsand bents.

8.4.4 Bridge Railing (Vacant)

8.4.5 Ladders, Stairs, Grates, Etc. (Vacant)

8.4.6 Surface Treatments (Vacant)

P:DP/BDM89807-0802

August 1998 8.4.3-15



8.4.7 Deck Protection Systems

A deck protective system is to be included in all projects involving concrete bridge deck construction orrehabilitation. The type of system to be used shall be determined by the Bridge and Structures Branchduring the preliminary plan stage and shall be shown on the preliminary plan in the left margin. The mostcommonly used systems are listed below.

Future overlays for bridges with one of the following systems is unlikely; however, if an overlay becomesnecessary, a layer of concrete shall be removed equal to the weight of the asphalt overlay that will replaceit so that the dead load remains unchanged.

A. System Types

1. System 1: A 21/2-inch concrete cover over an epoxy-coated top mat of reinforcing with no over-lay (see Section 8.4.7B). The 21/2-inch cover includes 0.15 feet of depth for traction striations inthe roadway surface and 1/4-inch tolerance of the placement of reinforcing steel.

2. System 2: A 13/4-inch concrete design cover over an epoxy-coated top map of reinforcing steelwith 11/2 inches of later modified concrete overlay (see Section 8.4.7C). The design concretecover includes 1/4-inch tolerance for placement of reinforcing steel and 1/4-inch for scarifying theconcrete deck. The 11/2-inch latex modified concrete overlay is a minimum depth and includes.015 feet for traction striations. The bridge elevations shown on the layout sheet are to be basedon top of the overlay (3 inches total cover). Deck elevations shown on other plan sheets shall betop of concrete as constructed (13/4-inch cover).

3. System 3: A 11/2-inch or 2-inch concrete cover over an epoxy-coated top mat of reinforcing witha waterproofing membrane and asphalt overlay. Overlay thickness should be .15 feet (see Section8.4.7D). The 2-inch concrete cover is for cast-in-place construction and includes a 1/4-inch toler-ance for the placement of rebar. Because of the high quality of concrete and better control ofreinforcing placement, the concrete cover for the precast prestressed deck members is reduced to11/2 inches.

4. Other Systems: The type of systems available for use may change as new products becomeavailable. At present, there are four other systems available, namely thin polymer concreteoverlays, polyester polymer concrete, microsilica modified concrete, and cathodic protection.Thin polymer concrete overlays can be methyl methacrylate overlay or epoxy concrete overlay.All of the above systems are considered to be experimental and should not be used without theapproval of the Bridge Design Engineer.

June 1994 8.4.7-1



B. System 1 (Epoxy Coated Reinforcing Only)

1. With this system, only the roadway slap top mild reinforcing mat and traffic barrier S1 bars arecoated. This includes the top longitudinal negative moment reinforcing tied to the transversedeck reinforcing. Indicate the epoxy-coated reinforcing on the plan sheets and with an “E” in the“Epoxy Coated” column of the bar list. Add a note to the traffic barrier sheet to epoxy coat theS1 bars.

2. Secure all stirrups for crossbeams, diaphragms, webs, and prestressed girders for the roadwayslab with 135 hooks. Do not epoxy coat stirrups (see Figure 8.4.7-1).

March 1984Figure 8.4.7-1

8.4.7-2 April 1991



C. System 2 (Latex Modified Concrete Overlay with Epoxy Coated Reinforcing) Note: See System 1for additional details.

April 1991 8.4.7-3




D. System 3 (Asphalt Overlay with Waterproof Membrane and Epoxy-Coated Reinforcing) Note: Theclass of asphalt is to be determined by the district. See System 1 for additional details.


8.4.7-4 April 1991



E. System Selection for New Structures

1. System 1: This system will normally be used.

2. System 2: This system is considered to provide double protection and shall be specified for struc-tures with transverse post-tensioning in the deck. Deterioration of such decks seriously impairsthe structural integrity, and their restoration is complex and costly.

Consideration should also be given to this system for other types of structures. Factors that mayinfluence the decision are the type and size of structure, ADT, nature of traffic, impact of futuredeck reconstruction on traffic flow, and anticipated use of deicing chemicals. The Bridge DesignEngineer should be consulted before considering the use of a double protection system.

3. System 3: This system is also considered to provide some degree of double protection. However,the primary use of this system is for decks where a flexible leveling course is needed for joints inprecast deck units. This system is most suitable for bridges with Bulb “T” girders and precastslabs.

F. System Selection for Bridge Deck, Widening, and Rehabilitation

Only design widenings for a future overlay when the adjacent existing structure is not overlaid as partof the widening.

1. Epoxy-coated reinforcement is to be specified in the widened portion of the bridge.

2. System 2: This system is preferred since it provides long-term protection. This system willnormally be used when one or more of the following criteria are met:

a. Delaminated and patched areas of the concrete deck exceed 5 percent of the deck area.

b. A pacometer survey shows concrete cover over reinforcing steel of less than or equal to1 inch over 15 percent or more of the deck area.

c. Chloride contamination at the rebar level exceeds 2 pounds per cubic yard for 40 percent ormore of the samples tested.

d. When removal of an asphalt and membrane system is required. (This requirement willremain in effect until such time as a removal procedure is developed which will not result indamage to the underlying concrete.

e. Concrete in the deck exhibits inferior durability based on visual observation.

3. System 3: In this system, asphalt concrete is a nonstructural component; it tends to reduce theload carrying capacity of the bridge by the amount of the overlay added. This system may beused when all of the following criteria are met:

a. Delaminated and patched areas of the deck are less than 5 percent of the deck area.

b. Concrete cover exceeds 1 inch or 90 percent or more of the deck area.

c. ADT is less than 10,000 and the traffic index is less than 7.5.

d. Chloride contamination at the rebar level is less than 2 pounds per cubic yard or exceeds2 pounds per cubic yard for less than 40 percent of the samples tested.

e. Deck surface must be compatible with the membrane system. A rough or pocked surface willresult in damage to or early failure of the protective membrane.

4. Other Systems: Thin Polymer Concrete Overlay systems should be considered only in specialcases. They are particular suitable for bridges where weight of the overlay is critical, such asmovable span bridges, or where extended traffic disruptions are intolerable, but due to theirexperimental nature should be used only in special cases.

June 1994 8.4.7-5



Adoption of thin overlays should be coordinated with the district through the Bridge Planningand Technology Unit. The bridge Planning and Technology Development Unit must be contactedearly in the planning stage for using this system. This is required to coordinate development ofthe project with the district and if necessary the FHWA.

Use of a system other than Systems 2 and 3 (stated previously) is considered as an exception andwill require approval of the Bridge Design Engineer for its use.

The Bridge Planning and Technology Unit should be consulted about the latest information onthe new products available and also about the condition of the existing decks.

5. Deck Replacement: In some cases, deck deterioration will have advanced beyond the point ofcost effective rehabilitation and/or protection. Excessive delamination, high chloride content, re-active aggregate, and freeze-thaw have been the predominant factors contributing to deck deterio-ration. When deck replacement or bridge replacement becomes necessary, the replacementscheduled should be coordinated with the districts.

8-4-7:V:BDM2

8.4.7-6 April 1991


Miscellaneous Design Bibliography

8.99 Bibliography

1. E. I. Dupont de Nemours, Inc.“Design of Neoprene Bridge Bearing Pads.”

2. Bridge Drainage SystemNCHRP—Synthesis of Highway Practice No. 67Transportation Research BoardNational Research CouncilWashington, D.C. December 1979

3. Bridge Deck Drainage GuidelinesReport No. FHWA/RD-87/014December 1986

4. Hydraulics ManualWSDOT M23-03Olympia, WA 98504

5. Burke, M. P. Jr., “Bridge Deck Joints,” NCHRP 141, TRB, National Research Council, Washington,D.C., 1989, 66 pp.

6. Puccio, G. S., “Extruded Seals for Bridges and Structures,” Joint Sealing and Bearing systems forConcrete Structures, Vol. 2, SP-70, American Concrete Institute, 1982, p. 959.

7. Bashore, F. J., Price, A. W., and Branch, D. E., “Determination of Allowable Movement Ratings forVarious Proprietary Bridge Deck Expansion Joint Devices at Various Skew Angles, Second TestingSeries,” Research Report No. R-1245, Michigan Transportation Commission, Lansing, Michigan,May 1984, 24 pp.

8. Koster, W., “The Principle of Elasticity for Expansion Joints,” Joint Sealing and Bearing Systems forConcrete Structures, Vol. 2, SP-94, American Concrete Institute, 1986, pp. 675-712.

9. Babaei, K. and Hawkins, N. M., “Development of Durable Anchorage Systems for Bridge ExpansionJoints,” Final Report WA-RD 181.1, Washington State Transportation Center (TRAC), June 1989,56 pp.

10. Fatigue Design of Modular Bridge Expansion JointsNCHRP-Report 402Transportation Research BoardNational Research CouncilWashington, D.C. — 1997

11. Handbook of Bridge EngineeringChen, W. F. and Lian Duan, editorsChapter 25: Expansion JointsCRC Press — 1988

12. Steel Bridge Bearing Selection and Design GuideNational Steel Bridge AllianceAmerican Iron and Steel Institute, 1996

P:DP/BDM89807-0802

August 1998 8.99-1

September 1992 8.2 - A1 - 1


Sign Structure FoundationMiscellaneous Design Material Quantities


Sign Structure FoundationMiscellaneous Design Material Quantities

8.2 - A1 - 2 September 1992

8-2-A1:VP:BDM8

September 1992 8.2 - A3


Notes to DesignersMiscellaneous Design Truss Sign Bridge Foundations

Notes to designers pertaining to the use of BDM Appendix A, 8.2-A4 (double-faced barrier foundation, Type 1, 2,and 3, for truss sign bridge).

1. Indicate type of foundation to be used (Type 1, 2, or 3).

2. Determine conduit needs. If none exist, delete all references to conduit. If it is needed, verify with district as tosize and quantity needed.

3. Show sign bridge base elevation, number, “D” dimension and station.

4. Modify details if other than a 3-inch curb is required.

5. Transition section can be 10 feet 0 inches or 12 feet 6 inches.

6. Note vertical shaft and tie steel No. 1 and No. 2.

7. Quantities for the barrier as shown:

Class 4000 concrete .185 CY/LF above foundation cap.269 CY/LF outside foundation cap

Class 3000 or 3000W Varies with type and depth ofconcrete foundation. See Standard Plan

G-2b for dimensions.

Gr. 60 Rebar Varies, depends upon type offoundation and “D” dimension.

Mark No. 21 and 22 Constant

Mark No. 24 Maintain 6-inch o.c. spacingbetween end posts of truss.

Mark No. 26 Varies with span length and “D”dimension

8. Example contracts: 3345 SR 5 Southbound Add Lane3393 Interstate VMS Signing

8-2-A3:V:BDM8



Notes to DesignersMiscellaneous Design Monotube Sign Bridge Foundations

Notes to designers pertaining to the use of BDM Appendix A, 8.2-A6 (double-faced barrier foundation, Type 1, 2,or 3, for Monotube Sign Bridge).

1. Indicate type of foundation to be used (Type 1, 2, or 3).

2. Determine conduit needs. If none, delete. If needed, contact district for number and size.

3. Determine sections needed to “build” foundation, transition sections can be 10 feet 0 inches or 12 feet 6 inches.

4. Show sign bridge : 1. Base elevation

2. Station

3. Number

5. Modify details if other than 3-inch curb is required.

Approximate quantities for foundation as shown:

Class 4000 .289 CY/LF over shaft foundation.

Class 3000 or 3000W Varies – see typical foundation sheet.

Steel Reinforcing 372 poundsGr. 60

Steel AASHOT M222 or M223 GR. 50

60 feet & under = 1,002 pounds

60 feet to 90 feet = 1,401 pounds

90 feet to 120 feet = 1,503 pounds

120 feet to 150 feet N/A

6. Example contract 3283 Eastside to Plum

8-2-A5:V:BDM8



Notes to DesignersMiscellaneous Design Monotube Sign Structures

Notes to designers pertaining to the use of BDM Appendix A, 8.2-A8 through A-13 (Monotube Sign Structures).

1. Note if view is looking ahead or back on stationing.

2. Note the bridge sheets on which the structure details are contained.

3. If not Type 1, 2, or 3, note the average lateral bearing pressure for each foundation.

4. If some span lengths are not used on a particular project, delete these from lower table to free up room.

5. Note size and quantity (if any) of conduit to be installed.

6. If no cantilevers are included, delete detail.

List of contracts with special designs

C-3199 First Hill Lid

C-3334 Third Lake Paving and Systems

C-3502 Seattle Transit Access Phase 1

8-2-A7:V:BDM8

July 1996 8.3 - A1 - 1


Notes for Utility InstallationsMiscellaneous Design to Existing Bridges


Notes for Utility InstallationsMiscellaneous Design to Existing Bridges

8.3 - A1 - 2 July 1996

September 1992 8.3-A5


Notes to DesignersMiscellaneous Design for Bridge Railing

1. Bridge Railing Type BP, Appendix 8.3-A3, is to be used when clear anodic coating is desired.

2. Bridge Railing Type BP-B, Appendix 8.3-A4, is to be used when bronze anodic coating is desired.

3. To determine height of railing, use 4′-6″ measured from the top of the railing to the reference surface (asdefined by AASHTO).

4. On the final plan sheet, show only one dimension for the height of the metal railing in two different places.

8-3-A5:V:BDM8

Notes to Designers for Type BP and Type BP-B Bridge Railing

September 1992 8.3-A10


Notes to DesignersMiscellaneous Design for Traffic Barrier

1. Show back of Pavement Seat in “Plan — Traffic Barrier” detail.

2. At roadway expansion joints, show traffic barrier joints normal to centerline, except as shown in Appendix8.4-A1.

3. When an overlay is required, the 3″ maximum and 2′-8″ minimum dimensions shown in “Typical Section —Traffic Barrier” shall be referenced to the top of the overlay.

4. Approximate quantities for the Traffic Barrier are as follows:

Class 4000 Concrete 0.100 cu. yds./L.F. with 3″ curb0.110 cu. yds./L.F. with overlay427 lb./L.F. with 3″470 lb/L.F. with overlay

Steel Reinforcement Bars 15.2 lb/L.F. (Bars R1 to R6)Bars S1, S2, and S3 (when applicable) should be included in normalBar List.

5. The horizontal leg of S2 should lap the transverse slab bars by 1′-0″ minimum.

6. When bridge lighting is a part of the contract, show lighting bracket and conduit details on a separate sheet.

8-3-A5:V:BDM8

Notes to Dsigners for Cast-in-Place Traffic Barrier

May 1993 8 - B1


Notes to DesignersMiscellaneous Design Pin Bearings

8-B1:V:BDM8

Pin Bearing Notes

(These notes change constantly. For the latest information, check the Bridge Section’s “Book of Knowledge”(BOK) which is available through your supervisor.)

1. Anchor bolts shall conform to ASTM A 490, ASTM A 449.

2. Paint anchor bolts (from top of bolt to 6 inches below top of pier), nuts and washers with two coats of zincrich paint, Standard Formula A-9-73.

3. Anchor bolts shall be pressure grouted from the bottom up utilizing the grout tube. The grout tube shallextend to the bottom of the pipe. Anchor bolts shall be grouted prior to grouting under the masonry plate.Pressure grout the masonry plat from the center to the outside edges through a grout tube.

4. Pin nuts shall conform to AASHTO M291 Grade DH. Pin nuts shall be tightened to a minimum of 200 ft.-lbs.of torque for a snug fit.

5. Pin blocks shall conform to AASHTO M102, including supplementary requirement S4 with a minimumyield point of 50,000 psi.

6. Bearing pins shall conform to ASTM A 434 with a minimum yield strength of 70,000 psi.

7. Clean pin and adjoining bearing surfaces and coat these surfaces with grease.

8. The bearing plate of each expansion bearing shall be centered transversely between the guide barsimmediately prior to grouting of the pipes and grouting under the masonry plates. The bearing plate shall bepositioned longitudinally as shown.

9. Shim stacks shall be plumb and level. The bottom shim of each stack shall be machine tapered to account forboth transverse and longitudinal top of pier slopes.

10. The 28-day compressive strength of the grout in the grout pad and in the pipes shall be 4,000 psi.

11. Stainless steel screws shall conform to ASTM F 593 Type 304.

12. Do not paint sliding surfaces and bearing pin mated surfaces.

8 - B2 May 1993


Notes to DesignersMiscellaneous Design Spherical Bearing

8-B2:V:BDM8

Spherical Bearing Notes


1. Bearing elements shall be designed by the manufacturer in accordance with the Special Provisions to resistthe forces given in the Table of Bearing Loads.

2. Bearing elements and keeper plates shall be sized to fit the geometric limitations shown and to accommodategirder details.

3. Top of grout pad elevations shown on the column sheets are based on an assumed overall bearing height of__________.

The Contractor shall verify this bearing height after design of the bearing elements and shall provide newgrout pad elevations as necessary. Upon receipt of grout pad elevations, the Engineer will review the affectedpier and girder elements and implement any revisions (i.e., column/pier cap reinforcement). Centerline ofbearing locations are shown on bridge sheets _____.

4. Bearing elements shall be removable and replaceable.

Shop drawings shall be submitted to the Engineer for approval prior to the manufacture of the bearings. Thissubmittal shall include a complete set of calculations.

5. Keeper plates shall be designed for applied bearing pressures resulting from the loads and movement providedin the table.

6. Bearing elements shall be sized utilizing Service Load Design methods except for the AASHTO Group VII,allowable stresses shall be increased by 50 percent.

7. Anchor bolts as shown shall be used to secure the lower keeper plate and masonry plate where applicable tothe pier. The bearing manufacturer shall determine the weld size connecting the upper keeper plate to thegirder based upon the bearing loads and size of the upper keeper plate required to accommodate the bearingas per AASHTO.

8. Full horizontal forces shall be resisted by the external restrainer.

9. The stainless steel sheet shall completely cover the T.F.E. surface in all operating positions and shall extendone additional inch in the longitudinal direction.

10. Spherical bearings shall be used at piers _____.

11. Rotational capacity = + _____ degrees minimum.

12. Pressure grout masonry bearing plates after the structural steel has been erected and prior to pouring theroadway slab. Group bearings from the center to the outside edges of the masonry and lower keeper platethrough the grouting tube.

13. Shim stacks shall be level. The bottom shim of each stack shall be machine tapered to account for bothtransverse and longitudinal top of pier slopes.

Reminders:

*Bearing height becomes very important at hinges when the bearings are contractor designed. Hinge gapshould be sized before bearings are designed.

*

May 1993 8 - B3 - 1


Notes to DesignersMiscellaneous Design General

General Notes


1. All material and workmanship shall be in accordance with the requirements of the state of Washington,Department of Transportation, Standard Specifications for Road, Bridge and Municipal Construction dated________.

2. A. This structure has been designed in accordance with the requirements of the ________ AASHTOStandard Specifications for Highway Bridges.

All prestressed concrete elements have been designed for service load stresses and checked for therequirements of load factor design.

All other structural elements are designed in accordance with the requirements for load factor design.

B. This structure has been designed in accordance with the requirements of the _______ AASHTOSpecifications for Highway Bridges.

All structural elements have been designed in accordance with load factor design.

3. Seismic design of this structure conforms with the provisions of the AASHTO Guide Specifications forSeismic Design of Highway Bridges, dated 1983 and interims through __________. An accelerationcoefficient of __________ has been used.

4. Footing elevations and substructure details are subject to change depending upon foundation materialencountered. Reinforcing steel for footings, abutment walls, and columns shall not be cut until final elevationshave been determined and substructure details have been modified, if necessary.

5. The concrete in the seals and shafts shall be Class _______. The concrete in the superstructure, includingroadway deck and crossbeams, as well as bridge columns, shall be Class _______. All other cast-in-placeconcrete shall be Class _______.

6. The concrete seals at piers __________ are designed for a water surface elevation of _________. After sealsare poured, cofferdams shall not be dewatered when the water is above elevation _________. Provision shallbe made to flood the cofferdam in the event that water surface is above the design elevation.

7. The maximum design soil pressure per square foot is _____ tons for piers _____, the maximum design loadfor the piles for piers _____ is _____ tons. The maximum design load for the shafts is _____ tons.

8. Falsework shall be carefully released to prevent impact or undue stress in structure. The traffic barrier andsidewalk shall not be poured until the falsework has been released.

9. All steel shall be AASHTO M183 and galvanized after fabrication according to AASHTO M111, unlessnoted otherwise.

10. All bolts except as noted shall be ASTM A307 and shall have standard nuts and washers and galvanizedaccording to AASHTO M232.

All screws and miscellaneous fasteners shall be ASTM A 307 and galvanized according to AASHTO M232.

11. All bolt hole sizes shall be 1/16-inch diameter larger than bolt diameter. Bolt lengths not shown shall be asrequired to fit.

12. All dimensions and elevations shall be verified in the field by the contractor.

8 - B3 - 2 May 1993


Notes to DesignersMiscellaneous Design General

8-B3:V:BDM8

13. Unless otherwise shown on the plans, clear concrete cover from top of roadway slab to any reinforcement barshall be 21/2 inches, 1 inch from the bottom of the roadway slab, 3 inches from the bottom of footing, and11/2 inches from all other concrete surfaces.

Reminders:

Normally used concrete mixes in Item #5 above are 4000W, 4000, and 4000 respectively.

Items #9, #10, and #11 may be omitted on steel superstructure bridge designs as they may conflict withStructural Steel Notes.

Item #12 is normally appropriate for rehabilitation and widening projects.

May 1993 8 - B4


Notes to DesignersMiscellaneous Design Post-Tensioning

8-B4:V:BDM8

Post-Tensioning Notes


1. The concrete in superstructure shall be Class 5000 mix, fc′ = 5000 psi. The minimum compressive strength ofthe cast-in-place concrete at the time of post-tensioning shall be _____ psi.

2. Design is based on a friction curvature coefficient, µ = 0.2 and a friction wobble coefficient, K = 0.0002. Theloss of stress in post-tensioned prestressing strands due to steel relaxation, elastic shortening, creep andshrinkage of concrete is estimated to be 32 ksi.

3. Design is based on _____ 1/2-inch diameter low relaxation strands with an anchor set of 3/8 inch. The actualanchor set will depend on the jacking equipment used by the contractor and shall be specified in the shopplans. Each web shall be stressed to a load of _____ kips at jacked end after seating.

4. The contractor shall submit the stressing sequence, elongation calculations, and force after anchor set to theengineer for approval. The stressing sequence shall meet the following criteria:

A. Unless otherwise noted, the prestressing force, P-jack shall be distributed with an approximately equalamount in each web and shall be placed symmetrically about the center line of bridge.

B. Whenever possible, no more than one-half of the prestressing force in any web may be stressed before anequal force is stressed in the adjacent webs. At no time during stressing operations will more thanone-six of the total prestressing force be applied eccentrically about the center line of the bridge.

5. The maximum outer diameter of the duct shall be ____ inches. The area of the duct shall be at least twicethe net area of the prestressing steel in the duct.

6. All tendons shall be stressed _____________________________ (either one end or both ends).

7. The maximum number of strands permitted in a duct is limited to 34 numbers. Contractor shall obtainapproval of the Engineer for any deviation to the number of strands in a duct as shown on the plans. Anychanges associated to the thickness of the web shall be at contractor’s expense.

Reminders:

1. Commonly used stress levels in note number 1 are 3000 psi and 3500 psi.

2. For tendons made of 19 or less strands of 1/2-inch diameter, adopt web thickness of 101/2 inches.

3. For tendons made of 20 to 31 strands of 1/2-inch diameter, adopt web thickness of 111/2 inches.

4 For tendons made of 34 strands of 1/2-inch diameter, adopt web thickness of 12 inches.

5. Do not use any tendon made of 1/2-inch strand greater than 34 strands.

6. All longitudinal bars will be placed between vertical stirrups.

May 1993 8 - B5 - 1


Notes to DesignersMiscellaneous Design Structural Steel (Box Girder)

Structural Steel Notes


1. All structural steel shall be structural low alloy steel AASHTO M222 or M223 grade 50, except membersmarked C may be fabricated from AASHTO M183 steel.

2. ASTM A 715 may be used for filler plates less than 1/4-inch thickness.

3. All field and shop connections shall be made with high strength bolts, with the bolt heads toward the outsideand underside of the bridge. High strength bolts shall be to AASHTO M164 and shall be 7/8-inch diameter.Nuts and washers shall conform to Standard Specifications, Section 9-06.5(3). The minimum center-to-centerdimension shall be 3 inches unless shown otherwise. All connections shown are for field bolting. Shop boltingmay be used where approved in the shop plans.

4. All welding shall be done with minimal distortion. The welding sequences and procedures to be used shall besubmitted to the Engineer for approval prior to the start of welding. Top flanges, bottom flanges, and websshall be fabricated to full length between field splices prior to welding flanges to webs. Welding Sequence:(1) flange and web splices, (2) flanges to web, (3) stiffeners to webs and flanges, (4) gusset plates to webs,and (5) shear connectors to top flange.

5. One butt splice will be permitted for flange and web plates exceeding 60 feet in length. A permissiblelocation will be shown in the plans. Any proposed butt splice shall be shown on the shop drawings submittedfor approval.

6. Intermediate transverse stiffeners, web splices, and all intermediate cross frames shall be normal to the flanges.

7. All dimensions are horizontal and vertical, unless otherwise shown.

8. All welded shear studs shall be 7/8-inch diameter.

9. Members marked V are main load carrying tensile members or tension components of flexural membersand shall meet the longitudinal Charpy V-Notch tests as described in the Special Provisions.

10. Members marked FCM are fracture critical members and shall meet the fracture control requirement testsas described in the Special Provisions.

11. X denotes tension butt weld for flanges or webs.

12. Galvanizing shall be in accordance with AASHTO M111 or M232 as applicable.

13. Bolt holes remaining in girder webs upon removal of deck formwork and temporary bracing shall be treatedin accordance with the Standard Specifications. Deck formwork shall not be supported on top laterals.

14. Remove temporary cross frames between box girders after the entire bridge deck has been placed and reacheda minimum strength of 4,000 psi.

15. The contractor shall provide temporary web bracing and/or stiffening at locations where slab forms are attachedto unbraced or unstiffened webs.

16. The designations V , FCM , and C marked on portions of the bottom flange also apply to stiffenersattached to or supported by the bottom flange.

17. All structural steel shall be painted.

Reminders:

Remove Note: “A 715 for Filler Plates” when minimum thickness is > 1/4 inch.

Remove Note Regarding: FCM when not applicable.


Notes to DesignersMiscellaneous Design Structural Steel (Box Girder)

8 - B5 - 2 May 1993

8-B5:V:BDM8

Butt splice locations are the contractor’s option, except, no splice will be permitted within 20 feet of thecenterline of a pier or within 6 inches of an intermediate cross frame stiffener.

Intermediate transverse web stiffeners shall be located a minimum of 6 inches from a welded web orflange splice.

May 1993 8 - B6

8-B6:V:BDM8


Notes to DesignersMiscellaneous Design Structural Steel (Plate Girder)

Structural Steel Notes


1. All structural steel shall be structural low alloy steel AASHTO M222 or M223 grade 50, except membersmarked C may be fabricated from AASHTO M183 steel.

2. ASTM A 715 may be used for filler plates less than 1/4-inch thickness.

3. All field and shop connections shall be made with high strength bolts, with the bolt heads toward the outsideand underside of the bridge. High strength bolts shall be to AASHTO M164 and shall be 7/8-inch diameter.Nuts and washers shall conform to Standard Specifications, Section 9-06.5(3). The minimum center-to-centerdimension shall be 3 inches unless shown otherwise. All connections shown are for field bolting. Shop boltingmay be used where approved in the shop plans.

4. All welding shall be done with minimal distortion. The welding sequences and procedures to be used shall besubmitted to the Engineer for approval prior to the start of welding. Top flanges, bottom flanges, and websshall be fabricated to full length between field splices prior to welding flanges to webs. Welding Sequence:(1) flange and web splices, (2) flanges to web, (3) stiffeners to webs and flanges, (4) gusset plates to webs,and (5) shear connectors to top flange.

5. One butt splice will be permitted for flange and web plates exceeding 60 feet in length. A permissiblelocation will be shown in the plans. Any proposed butt splice shall be shown on the shop drawings submittedfor approval.

6. Intermediate transverse stiffeners, web splices, and all intermediate cross frames shall be normal to the flanges.

7. All dimensions are horizontal and vertical, unless otherwise shown.

8. All welded shear studs shall be 7/8-inch diameter.

9. Members marked V are main load carrying tensile members or tension components of flexural membersand shall meet the longitudinal Charpy V-Notch tests as described in the Special Provisions.

10. Members marked FCM are fracture critical members and shall meet the fracture control requirement testsas described in the Special Provisions.

11. X denotes tension butt weld for flanges or webs.

12. Galvanizing shall be in accordance with AASHTO M111 or M232 as applicable.

13. Bolt holes remaining in girder webs upon removal of deck formwork and temporary bracing shall be treatedin accordance with the Standard Specifications.

14. The contractor shall provide, if required, temporary web bracing and/or stiffening at locations where slab formsare attached to unbraced or unstiffened webs.

15. All structural steel shall be painted.

Reminders:

Remove Note: “A 715 for Filler Plates” when minimum thickness is > 1/4 inch.

Remove Note Regarding: FCM when not applicable.


Notes to DesignersMiscellaneous Design Strip Seal Expansion Joint

8 - B7 May 1993

8-B7:V:BDM8

Strip Seal Expansion Joint Notes


1. See strip seal table for approved manufacturers.

2. The entire strip seal assembly shall be constructed so that the strip seal may be removed and replaced.

3. The contractor shall submit details and installation procedure for strip seal assembly to the engineer forapproval. Temporary lifting, temperature, and construction adjustment devices shall not be welded to thesteel shapes. However, threaded studs may be welded to the steel shapes then removed by grinding and acorrosion protection system applied to the areas affected by the grinding.

4. The strip seal shall be continuous. One factor vulcanized splice will be permitted per seal.

5. If the opening between the steel shapes will be less than 11/2 inches at the time of seal installation, the seal maybe installed prior to encasement of the extrusions in concrete.

6. The shear studs attached to the steel shapes shall be shown on the shop drawings and shall not interfere withreinforcing in the blockout.

7. A. (When Class 4000D concrete is used in the deck.)

Class 4000LS concrete shall be placed in the blockout between the expansion joint system and adjacentroadway slab.

B. (When Class 5000D concrete is used in the deck.)

Class 5000LS concrete shall be placed in the blockout between the expansion joint system and adjacentroadway slab.

May 1993 8 - B8

8-B8:V:BDM8


Notes to DesignersMiscellaneous Design Modular Expansion Joint

Modular Expansion Joint Notes


1. The modular expansion joint system shall allow a minimum total movement normal to joint of ____ inchesat pier 1 and ____ inches at pier _____.

2. Modular expansion joint system shall be as specified in the modular expansion joint table found in thecontract plans.

3. Aluminum components shall not be used.

4. Blockout dimensions as shown in the plans shall be verified by the contractor.

5. Blockout reinforcing steel shall be specified by the expansion manufacturer. The roadway slab reinforcingsteel shown elsewhere is the minimum required.

6. The contractor shall submit details of the modular expansion joint system to be used together withinstallation procedures, and reinforcing steel required to the engineer for approval prior to installation.

7. The contractor shall not install the modular expansion joint until the entire superstructure, except the trafficbarriers, is completed.

8. Sealing elements shall be strip seals. Minimum size and strip seal shall be 80 mm.

9. “G” dimension is measure from nose to nose of steel edge beams and includes effects of anticipated creepand shrinkage.

10. Class _____ LS concrete shall be placed in the blockout between the expansion joint system and adjacentroadway slab.


Notes to DesignersMiscellaneous Design Rail Rehabilitation

8 - B9 May 1993

8-B9:V:BDM8

Rail Rehabilitation Notes


1. All material and workmanship shall be in accordance with the requirements of the current version ofWSDOT Standard Specifications for Road, Bridge, and Municipal Construction, and admendments.

2. This structure has been designed in accordance with the requirements of the 1992 AASHTO specificationsfor highway bridges and interims through _______. All elements have been designed in accordance withthe requirements for load factor design.

3. A. The concrete in the traffic barrier shall be Class 4000.

B. All steel shall be AASHTO M183 and galvanized after fabrication according to AASHTO M111, unlessotherwise shown in the plans.

4. All bolts, unless otherwise shown in the plans, shall be AASHTO M164, and shall be galvanized afterfabrication according to AASHTO M232. All screws and miscellaneous fasteners shall be ASTM A 307 andgalvanized in accordance with AASHTO M232.

5. All bolt hole sizes shall be 1/4-inch diameter larger than the bolt diameter. Bolt lengths not shown shall be asrequired to fit with 1-inch minimum threads exposed beyond nut.

6. Unless otherwise shown on the plans, the concrete cover measured from the face of the concrete to theface of any reinforcing steel shall be 21/2 inches at the top of the roadway slab, 1 inch at the bottom of theroadway slab, 2 inches at the top of footing, 3 inches at the bottom of footing, and 11/2 inches at all otherlocations.

September 1992 8.4 - B1


Miscellaneous Design Compression Seal Design Example

Reinforced concrete box girder bridge with an overall length of 248 feet out to out of pavement seats. Endabutments are “L” abutments with one foot thick backwalls. Note: Joints at the end piers for this bridge could beeliminated by using monolithic or integral end abutments.

Skew angle = 28° < 45°Temperature range = 0° to 100°F

1. Determine Compression Seal Width Required

Determine total movement of joint, Mt: L = (248′/2) - 1′ = 123′

Temperature: 12(123)(0.000006)(100°F) = 0.89"Shrinkage: 12(123)(0.0002)(0.8) = 0.24“

Mt = 1.13"

Total movement parallel to the joint: Mp = 1.13(Sin 28°) = 0.53"Total movement normal to the joint: Mn = 1.13(Cos 28°) = 1.00"

Determine seal width required:

From Eq. (8) W = 0.53/0.22 = 2.41"From Eq. (9) W = 1.00/0.45 = 2.22"From Eq. (11) W = 4(Cos 28°)[0.64(0.89) + 0.24] = 2.86" <= Controls

Use a 3" wide seal (W = 3").

2. Determine Width of Joint at Time of Construction: Use Eq. (12)

Construction Width at Tc = 40°F:

A const = 0.6(3.0) + Cos 28°(12)(123)(0.000006)(64-40) = 1.99" Use 2"


A const = 0.6(3.0) = 1.80" Use 13/4"


A const = 0.6(3.0) + Cos 28°(12)(123)(0.000006)(64-80) = 1.68" Use 15/8"

8-4-B1:V:BDM8



Miscellaneous Design Strip Seal Design Example 1

Cast-in-place concrete bridge with an overall length of 400 feet. The structure is symmetrical and has 200 feet (at64°F) between point of zero movement and the end pier joints.

Skew = 30°, use movement along bridge centerlineTemperature range = 0° to 100°F

1. Determine Size of Strip Seal Required

Total opening movement of joint:

Temperature: 64° to 0°F (12)(200)(0.000006)(64) = 0.92"Shrinkage: (12)(200)(0.0002)(0.8) = 0.38“

= 1.30"

Total closing movement of joint:

Temperature: 64° to 100°F (12)(200)(0.000006)(36) = 0.52"

Set minimum installation width at 64°F:

Min. at installation, Group 1: (1.5-0.5)/Cos 30° = 1.15" > 0.52"(Group 1 joints have a 1/2" gap at full closure)

Min. at installation, Group 2: (1.5-0.0)/Cos 30° = 1.73" > 0.52"(Group 2 joints have no gap at full closure)

Determine size of joint required using the larger of either the minimum installation width or the total closingmovement:

Group 1: Add opening and closing 1.30 + 1.15 = 2.45" Use 3"Group 2: Add opening and closing 1.30 + 1.73 = 3.03" Use 3"

2. Determine Width Calculations for Various Temperatures

Construction Width at 64°F for both Group 1 and 2 Strip Seals:

G = Manufacturer's minimum installation width at 64°F Use 11/2"

Construction Width at 40°F:

G = 1.50 + Cos 30°(12)(200)(0.000006)(64-40) = 1.80" Use 17/8"


G = 1.50 + Cos 30°(12)(200)(0.000006)(64-80) = 1.30" Use 13/8"

Note: In this case, the minimum seal installation width at 64°F is the same for both Group 1 and 2 strip seals,because the minimum installation width at 64°F exceeded the total calculated closing movement of the joint.This may not be true in all cases as shown in Appendix 8.4-B4.

8-4-B2:V:BDM8




Cast-in-place concrete bridge with an overall length of 900 feet. The structure is symmetrical and has 450 feet (at64°F) between point of zero movement and the end pier joints.

Skew = 40° > 30° degrees, see Joint SpecialistTemperature range = 0° to 100°F



Temperature: 64° to 0°F (12)(450)(0.000006)(64) = 2.07"Shrinkage: (12)(450)(0.0002)(0.8) = 0.87“

= 2.94"


Temperature: 64° to 100°F (12)(450)(0.000006)(36) = 1.17"


Min. at installation, Group 1: 1.0/Cos 40° = 1.31" > 1.17"Min. at installation, Group 2: 1.5/Cos 40° = 1.96" > 1.17"

Determine size of joint required using the larger of either the minimum installation width or the total closingmovement:


Watson Bowman ACME (Group 2) has a 2" minimum opening for a 5" seal:

Minimum at installation, Watson Bowman Acme: 2.0/Cos 40° = 2.61"

Add opening and closing for Watson Bowman ACME

2.94 + 2.61 = 5.55" > 5" Cannot use Watsom Bowman ACME 5" Seal

After consulting with the Joint Specialist on the skew and size of strip seal required, the 5-inch seal cannotclose without possibly buckling and inverting above the roadway surface. Therefore, a modular joint shouldbe used.

8-4-B3:V:BDM8

September 1992 8.4 - B4 - 1



Steel bridge with an overall length of 600 feet. The structure is symmetrical and has 300 feet (at 64°F) betweenpoint of zero movement and the end pier joints.

Skew = 20°Temperature range = -30° to 120°F (Eastern Washngton)



Temperature: 64° to -30°F 12(300)(0.0000065)(94) = 2.20"


Temperature: 64° to 120°F 12(300)(0.0000065)(56) = 1.31"


Min. at installation, Group 1: 1.0/Cos 20° = 1.07" < 1.31"Min. at installation, Group 2: 1.5/Cos 20° = 1.60" > 1.31"

Determine size of joint required using larger of either the minimum installation width or the total closingmovement:


2. Construction Width Calculations for Various Temperatures

Group 1 Strip Seals:


Use the larger of the manufacturer's minimum installation width at 64°F or the total closing movement ofthe joint.

G = Manufacturer's minimum installation width at 64°F = 11/2"

Total closing movement of the joint:

Cos 20°(1.31) + 0.50 = 1.73" > 1.50" Use 13/4"(Group 1 joints have a 1/2" gap at full closure.)


G = 1.75 + Cos 20°(12)(300)(0.0000065)(64-40) = 2.28" Use 21/4"


G = 1.75 + Cos 30°(12)(300)(0.0000065)(64-80) = 1.40" Use 13/8"

Group 2 Strip Seals:


G = Manufacturer's minimum installation width at 64°F = 11/2"

8.4 - B4 - 2 September 1992



Total closing movement of the joint:

Cos 20°(1.31) + 0.0 = 1.23" < 1.50" Use 11/2"(Group 2 joints have no gap at full closure.)


G = 1.50 + Cos 20°(12)(300)(0.0000065)(64-40) = 2.03" Use 2"


G = 1.50 + Cos 20°(12)(300)(0.0000065)(64-80) = 1.15" Use 11/8"

8-4-B4:V:BDM8



Miscellaneous Design Determine Gmin and Gmax for Modular Joints

1. D. S. Brown Co., D-241, Modular Joint

B = Center Beam Flange width = 2.213"MR = Total movement rating = 9"N = Total No. of seals (= MR/MS) = 3 sealsN-1 = Number of centerbeams = 2 centerbeamsMG = Minimum gap per seal at full closure = 1/2" per sealMS = Maximum movement rating per seal = 3" max.

Calculate Gmin and Gmax: See Equations (13) and (14) in Section 8.4.1.

Gmin = (N-1)(B) + (N)(MG)= (2)(2.213) + (3)(1/2) = 5.93" Use 6"

Gmax = Gmin + MR = 6 + 9 = 15" Use 15"

2. Watson Bowman ACME, WABO D-1200, Modular Expansion Joint

B = 2.5"MR = 12"N = 4 sealsN-1 = 3 centerbeamsMG = 0" per seal

From Equations (13) and (14), determine Gmin and Gmax:

Gmin = (3)(2.5) + (3)(0) = 7.50" Use 71/2"Gmax = 7.5 + 12 = 19.5" Use 191/2"

Note: Gmin and Gmax for other modular joint manufacturers are computed in a similar manner.

8-4-B5:V:BDM8

September 1992 8.4 - B6 - 1


Miscellaneous Design Modular Joint Design Example 1

Steel bridge with 600 ft (at 64°F) between the point of zero movement and the end pier joint.

Skew = 20° < 30°Temperature range = -30° to 120°F (Eastern Washngton)

1. Determine Size of Joint Required


Temperature: 64° to -30°F (12)(600)(0.0000065)(94) = 4.40"


Temperature: 64° to 120°F (12)(600)(0.0000065)(56) = 2.62"

Design movement along bridge centerline:

Add opening and closing (4.40 + 2.62) = 7.02"

Design movement normal to joint + 15 percent:

Cos 20°(7.02)(1.15) = 7.59"

Need a modular joint with a 5" movement rating (MR).


a. D. S. Brown Co., Type D-241, MR = 9"

Gmin = 6" (See Appendix 8.4-B5 for Gmin and Gmax.)Gmax = 15"


Set the joint opening (normal to the joint) at 64°F and allow a 15 percent safety factor:

G at 64°F = Gmin + total closing movement of joint= 6.0 + Cos 20°(2.62)(1.15) = 8.83"

Any setting greater than 8.83" would be adequate. Choose a setting so that the extra capacity is sharedequally between closing and opening of the joint.

Extra capacity = MR - Design Movement = 9 - 7.59 = 1.41"-30° to 64°F: (94°F/150°F)(1.41) = 0.88"Therefore, set G at 64°F = 8.83 + 0.88 = 9.71" Use 93/4"


G = 9.75 + Cos 20°(12)(600)(0.0000065)(64-40) = 10.81" Use 107/8"


G = 9.75" + Cos 20°(12)(600)(0.0000065)(64-80) = 9.05" Use 9"

Check spacing between centerbeams at 64°F for seal replacement:

Spacing = [9.75 - 2(2.213)]/3 seals = 1.77" > 1.50" ok

8.4 - B6 - 2 September 1992



Therefore, seals can be replaced without jacking the centerbeams apart.

Check spacing between centerbeams at minimum temperature:

G at -30°F = 9.75 + Cos 20°(4.40) = 13.88" < Gmax = 15" okMaximum spacing = [13.88 - 2(2.213)]/3 seals = 3.15" < 31/2" ok

b. Watson Bowman ACME, WABO D-900, MR = 9"

Gmin = 5"Gmax = 14"

Note that Gmin and Gmax are 1" less than those computed for D. S. Brown’s, Type D-241. Therefore, thetemperature setting calculations will also be 1" less than those for D. S. Brown’s type D-241.

G at 40°F = 97/8"G at 64°F = 83/4"G at 80°F = 8"

Check spacing between centerbeams at 64°F for seal replacement:

Spacing = [8.75 - 2(2.50)]/3 seals = 1.25" < 1.50"

Since the spacing is less than the 11/2" minimum recommended by the manufacturer for seal installation,the centerbeam will have to be jacked toward one of the edge rails in order to replace the seals.

Check spacing between centerbeams at minmum temperature:

G at -30°F = 8.75 + Cos 20°(4.40) = 12.88" < Gmax = 14" okMax. spacing = [12.88 - 2(2.50)]/3 seals = 2.63" < 31/2" ok

8-4-B6:V:BDM8

September 1992 8.4 - B7 - 1



Concrete Post-tensioned C.I.P. Box Girder Bridge

Skew = 0°Temperature range = 0° to 100°F

The following calculated movements due to temperature, shrinkage, elastic shortening, and creep were obtained:

Temp Fall 64° to 0°F 2.1" Temp Rise 64° to 100°F 1.2"Shrinkage 1.1"Elastic Shortening (ES) 0.8"Creep Ct(ES) = 1.5(0.8) = 1.2"


The Contractor would like to set the joint assembly 60 days after post-tensioning the structure. The elasticshortening due to post-tensioning has occurred. Assuming a long term creep factor, Ct, of 1.5, and that half ofthe shrinkage has occurred, determine:

Total opening movement of the joint: 2.1 + 0.5(1.1) + 1.2 = 3.9"Total closing movement of the joint: Temp Rise 64° to 100°F = 1.2"

Design Movement = 3.9 + 1.2 = 5.1" > 5" Use a Modular Joint

Determine Size of Modular Joint: Add 15 percent safety factor

Add opening and closing: (3.9 + 1.2)(1.15) = 5.9"

Need a modular joint with a 6" movement rating (MR)


a. D. S. Brown Co., Type D-161, MR = 6"

From Eq’s. (13) and (14), calculate Gmin and Gmax:

Gmin = (1)(2.213) + (2)(0.5) = 3.21" Use 31/4"

Gmax = 3.25 + 6 = 9.25" Use 91/4"


Set the joint opening at 64°F and allow a 15 percent safety factor

G at 64°F = Gmin + (Total Closing Movement due to Temp. Rise + 15 percent safety factor)= 3.25 + (1.2)(1.15) = 4.63" Use 43/4"

The total temperature movement for 100°F is 3.3"


G = 4.75 + (24°F/100°F)(3.3) = 5.54" Use 51/2"


G = 4.75 - (16°F/100°F)(3.3) = 4.22" Use 41/4"

Check spacing between centerbeam and edge rail at 64°F for seal replacement:

Spacing = (4.75 - 2.213)/2 seals = 1.27" < 1.50" ok

Therefore, centerbeams will have to be jacked to one side in order to replace the seals.

8.4 - B7 - 2 September 1992




G at 0°F = 4.75 + 3.9 = 8.65"

Maximum spacing = [8.65 - 2(2.213)]/2 seals = 2.11" < 31/2" ok

b. Watson Bowman ACME, WABO D-600, MR = 6"

Gmin = 2.5"Gmax = 8.5"


G at 64°F = Gmin + (Closing Movement due to Temperature Rise + 15 percent safety factor)

G at 64°F = 2.15 + (1.2)(1.15) = 3.88" Use 4"

The total temperature movement for 100°F is 3.3"


G = 4.0 + (24°F/100°F)(3.3) = 4.79" Use 43/4"


G = 4.0 + (16°F/100°F)(3.3) = 3.47" Use 33/2"

Check Gmin and Gmax, if G at 64°F is 4":

Include the 15 percent safety factor

Total closing = 4.0 - (1.2)(1.15) = 2.62" > Gmin = 2.5" okTotal opening = 4.0 + [2.1 + 0.5(1.1) + 1.2](1.15)

= 8.42" < 81/2" ok

Check spacing between centerbeam and edge rail at 64°F for seal replacement:

Spacing = (4.0 - 2.5)/2 seals = 0.75" < 1.50"

Since spacing is the than the 11/2" minimum recommended by the manufacturer for seal installation, thecenterbeam will have to be jacked toward one of the edge rails in order to replace the seal.

8-4-B7:V:BDM8

September 1992 8.4 - B8 - 1



Two C.I.P. Post-tensioned concrete box girder bridges meet at a hinge adjacent to a pier.

Skew = 0°

The following calculated movements due to temperature, shrinkage, elastic shortening, and creep were obtained:

Bridge A Bridge B

Temp Fall 64° to 0°F 3.0" 1.2"Shrinkage 1.3" 0.6"Elastic Shortening 1.2" 0.5"Creep, (Ct)(ES) = (1.5)(1.2") = 1.8" 0.75"Temp. Rise 64°F to 100°F 1.7" 0.7"


Determine joint opening 60 days after post-tensioning when the joint will be installed. Assume the elasticshortening and half of the shirnkage has occurred; assume a long-term creep factor, Ct = 1.5. Remember thatthe two bridges move opposite to one another.

Total opening movement of the joint due to Bridge A:

3.0 + (0.5)(1.3) + 1.8 = 5.45"

Total opening movement of the joint due to Bridge B:

1.2 + (0.5)(0.6) + 0.75 = 2.25"

Total opening movement due to Bridge A and B = 5.45 + 2.25 = 7.7"Total closing movement due to Bridge A and B = 1.7 + 0.7 = 2.4"

Determine size of Modular Joint: Include 15 percent safety factor

Add total opening and closing movements = (7.7 + 2.4)(1.15) = 11.6"

Need a Modular Joint with a 12" Movement Rating (MR)


a. Watson Bowman ACME, WABO D-1200, MR = 12"

Gmin = 7.5"Gmax = 19.5"


G at 64°F = Gmin + Closing Movement due to Temperature Rise= 7.50 + (2.40)(1.15) = 10.26" Use 103/8"

The total temperature movement for 100°F

= 3.0 + 1.7 + 1.2 + 0.7 = 6.6"/100°F


G = 10.375 + (24°F/100°F)(6.6) = 11.96" Use 12"


G = 10.375 - (16°F/100°F)(6.6) = 9.32" Use 93/8"

8.4 - B8 - 2 September 1992



Check if G at 64°F is 103/8" (include 15 percent safety factor):

Total Closing = 10.375 - (2.4)(1.15) = 7.16" > Gmin = 7.50" okTotal Opening = 10.375 + (7.7)(1.15) = 19.23" < Gmax = 19.50" ok


G at 0°F = 10.375 + 7.7 = 18.075" < GmaxMaximum spacing = [18.075 - 3(2.5)]/4 seals = 2.643" < 31/2" ok

b. D. S. Brown Co.,Type D-321, MR =12"

Gmin = 3(2.213) + 4(0.5) = 8.64" Use 83/4"Gmax = 8.75 + 12 = 20.75" Use 203/4"


G at 64°F = Gmin + Closing Movement Due to Temperature Rise= 8.75 + (2.40)(1.15) = 11.51" Use 115/8"

By comparison to previous calculations for Watson Bowman ACME, the construction width calculationsfor the D. S. Brown Co.’s, Type D-321, will be 11/4" greater (11.625" = 10.375") than those computed forthe Watson Bowman ACME, WABO D-1200.


G = 131/4"


G = 105/8"

Check if G at 64°F is 115/8" (include 15 percent safety factor):

Total Closing = 11.625 - (2.4)(1.15) = 8.86" > Gmin = 83/4" okTotal Opening = 11.625 + (7.7)(1.15) = 20.48" < Gmax = 203/4" ok


G at 0°F = 11.625 + 7.7 = 19.325"Max. spacing = [19.325 - 3(2.213)]/4 seals = 3.17" < 31/2" ok

8-4-B8:V:BDM8


Reinforced Elastomeric Bearing Pad Design ExampleMiscellaneous Design for Prestressed Girder (AASHTO Design Method A)

August 1998 8.4-B9-1

Standard WSDOT W74G simple span prestressed concrete girder bridge. Span length is 130 feet. Bottom flangewidth of the girder is 25 inches. Use a temperature range of 0°F to 100°F for concrete bridges witha normal construction temperature of 64°F. Use AASHTO Standard Specifications Section 14.4.1 DesignMethod A. Bearings shall be installed so that they are horizontal (level) under dead load.

Loading:

Dead Load reaction per bearing:

PDL, Girder = 108 kips

PDL, Slab+Traffic Barrier = 112 kips

Live Load reaction per bearing (excluding impact):

PLL,HS25 = 60 kips

Live Load rotation (calculated from analysis)

θLL,x = Live load rotation (excluding impact)

= 0.003 radians (from structural analysis)

Constants:

α = Coefficient of thermal expansion for concrete = 0.000006/°F

β = Shrinkage coefficient for reinforced concrete = 0.0002 in/in

µ = Shrinkage factor = 0.5 BDM Section 8.4.1A.1.b.(1)

Elastomer Design Parameters:

Durometer Hardness = 60

From AASHTO Table 14.3.1, for a 60 durometer hardness elastomer, the shear modulus varies between0.130 ksi and 0.200 ksi. Use a value corresponding to the most conservative design.

Internal Steel Reinforcement:

14 gauge plate (thickness = 0.075")Fy = 36 ksiFsr = 20 ksi

The bearing design shall conform to the following additional WSDOT standard requirements:

(a) Design for a 60-durometer elastomer.

(b) Unreinforced (plain) pads shall not be used.

(c) Internal elastomer layers shall be 1/2 inches thick; external elastomer layers shall be 1/4 inchesthick.

(d) Minimum number of internal elastomer layers shall be two.

(e) Maximum overall height of the bearing shall not exceed 5 inches.

(f) Tapered elastomer layers shall not be used.

(g) The shape factor of each layer of any reinforced bearing shall be equal to or greater than 5.0.

(h) The average compressive stress from dead load and uplift, if any, shall not be less than 200 psi toavoid “walking” of the bearings.

(i) Design loading shall take into account the effect of skew and curvature.

(j) The bearing design movement shall be based upon 75 percent of the total calculated temperaturerise and fall using an assumed normal temperature of 64°F plus any other anticipated movementsor translations.

(k) Girders are placed on the elastomeric bearing pads 30 days following casting. The remainingcreep of the girders tributary to each bearing has been calculated to be 0.20".

(l) The design details shall provide access for inspection, maintenance, and future replacement ofeach bearing.

(m) For thick bearings, calculate the grout pad elevations using the compressed height of the bearing.

1. Determine preliminary bearing size

Temperature fall (64° → 0°F): (0.000006)(64) (65)(12) = 0.30″

Temperature rise (64° → 100°F): (0.000006)(36)(65)(12) = 0.17″

Shrinkage: (0.5)(0.0002)(65)(12) = 0.08″

Creep (calculated from girder age of 30 days to infinity): = 0.20″

∆s = 0.75 (Dfall + Drise)+ Dshrink +Dcreep

= 0.75(0.30 + 0.17) + 0.08 + 0.20 = 0.63″

Determine bearing thickness:

Minimum total elastomer thickness ≥ 2∆s (AASHTO Section 14.4.1.3)

hrt ≥ (2)(0.63″) = 1.26″ Minimum total elastomer thickness required

Use (2) - 1/2″ thick interior layers of elastomer and 1/4″ thick cover layers.

2 interior layers at 1/2″ = 1.0″2 cover layers at 1/4″ = 0.5″

Total elastomer thickness, hrt = 1.5″ > 1.26″ ok

Use (3) - 14 gage steel shims. Sum of shim thicknesses = (3)(0.075″) = 0.225″

Total bearing thickness = T = 1.50″ + 0.225″ = 1.725″ < 5″ maximum ok

Determine bearing width, W:

Use a width equal to the width of the prestressed concrete girder bottom flange less two 1″ chamfersless an additional 1/2″ on each side.

W = 25 in - 2(1″) - 2(0.5″) = 22″ Use W = 22″

Determine bearing length, L:

σc,TL ≤ 1.000 ksi for steel reinforced bearings (AASHTO 14.4.1.1)

(220 kips + 60 kips) ∏ [(L)(22)] £ 1.000 ksi

L ≥ 12.73″ Use L = 13″

Preliminary bearing size: 13″ wide ξ 22″ long × 1.725″ thick



8.4-B9-2 August 1998

2. Check allowable compressive stress

Determine the Shape Factor, S, of the 1/2″ thick interior layers:

S = (L)(W) ∏ [2(hri)(L + W)] (AASHTO 14.2)

= (13)(22) ∏ [(2)(0.50)(13 + 22)] = 8.17 > 5.0 minimum

σc,TL,allowable= GS/b = (.130)(8.17)/1.0 = 1.062 ksi, but not greater than 1.000 ksi (AASHTO14.4.1.1)

σc,TL= 280 kips ÷ [(13)(22)] = 0.979 ksi £ 1.000 ksi ok

Check compressive stress under minimum load only. Keep σc,DL > 0.200 ksi to keep bearing from“walking” under minimum load. Assume minimum load occurs under dead load and uplift, if any.

σc,DL= 220 kips ∏ [(13)(22)] = 0.769 ksi ≥ 0.200 ksi ok

3. Check bearing stability (AASHTO 14.4.1.5)

To ensure stability, the total thickness of the bearing should not exceed the lesser of W/3 or L/3.

W/3 = 22″/3 = 7.33″ > 1.725″ ok

L/3 = 13″/3 = 4.33″ > 1.725″ ok

4. Check steel reinforcement (AASHTO 14.4.1.6)

Resistance of internal elastomer layer = 1,700hri = 1,700(0.5≤) = 850 lbs/inch

Pallow = (Fsr)(hs) = (20000 psi)(0.075≤) = 1500 lbs/inch > 850 lbs/inch ok

5. Check if bearing needs to be secured against horizontal movement (AASHTO 14.5):

Determine the design shear force on bearing, H:

H = GA∆s /hrt = (0.200)(13)(22)(0.63) ÷ (1.5) = 24.0 kips

PDL / 5 = 220 / 5 = 44.0 > 24.0 kips → Anchorage of the bearing is not required.

6. Check rotation (AASHTO 14.4.1.4)

Rotation perpendicular to the beam’s longitudinal axis: θTL,x ≤ 2∆c/ L

Rotation parallel to the beam’s longitudinal axis: θTL,z ≤ 2∆c/ W

Determine the compressive deflection, ∆c, using AASHTO Figure 14.4.1.2B:

Compressive stress = 0.979 ksi and Shape factor = 8.17 → Compressive strain = 0.039

∆c = (.039)[2(0.5″) + 2(0.25″)] = 0.058″

Assume girders are level after placement of slab and traffic barriers.

Therefore, θTL,x = θLL,x = 0.003 radians and θTL,z= 0.000 radians.

qTL,x, allowable = 2∆c / L

qTL,x,allowable= 2(0.058)/13 = 0.0090 radians > 0.003 radians ok



August 1998 8.4-B9-3

Summary:

Size: Length = 13″ Width = 22″ Overall total thickness = 1.725″

Elastomer layers: 2 interior layers at 1/2″ thick 2 cover layers at 1/4″ thick Total Thickness = 1.725"

Steel reinforcement: 3 steel shims, 14 gage (0.075 inch thickness) Provide 1/8″ minimum side clearance for the steel shims

P:DP/BDM89807-0802



8.4-B9-4 August 1998

July 1996 8.4 - B11


Elastomeric Bearing Pad ExampleMiscellaneous Design for Steel Girder

Spacing Chart: Page 8.4-B14

Pad Thickness Chart: Page 8.4-B15

Known: Skew = 33°

Girder = Series 120

Spacing = 8′-0″ (Normal to Girder)

From Spacing Chart (F(Ep)T ≅ 7,500 Lbs. > 22,200 Lbs. ∴ Pad Required

Known: Bridge Length = 420″ (Bk-Bk. Pavement Seat)

From Pad Thickness Chart: T = 2.32″

Use T = 21/2″ (1/2″ Laminates)

Girder Stop Bearing Pad Dimensions

Thickness = 21/2″

Length = 3 × 2.5 = 71/2″

Width = 5″ (Flange Depth - Chamfer)

(Number of Pads Required):

Known: Pad Thickness = 31/2″

F(Ep)T = 7,500 Lbs. (From Spacing Chart)

Number of Girders = 6

From Pad Thickness Chart: 2.4 Pads Required

Use Girder Stop Bearing Pads on three (3) of the girders in each end span.

Place pads on proper side of girder to oppose lateral component of force from earth pressure.

August 1998 8.4-B12-1


Miscellaneous Design Girder Stop Bearing Pads Example

8.4-B12-2 July 1996


Miscellaneous Design Girder Stop Bearing Pads Example

July 1996 8.4 - B13


Elastomeric Bearing PadMiscellaneous Design Design Chart

July 1996 8.4 - B14


Girder Stop Bearing PadsMiscellaneous Design Spacing Chart

July 1996 8.4 - B15


Girder Stop Bearing PadsMiscellaneous Design Pad Thickness Chart

July 2000 9.0-i


Substructure Design Contents

Page

9. Substructure Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.1-1

9.1 General Considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

9.1.1 Loads . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1A. General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1B. Dead Loads . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1C. Live Loads . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1D. Wind Loads . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3E. Earthquake Loads . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3F. Prestressing Effects from Superstructure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

9.1.2 Concrete Design for Substructures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

9.1.3 Application of Loads to Substructure Units . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4A. Live Loads . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4B. Earthquake . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

9.2 Piers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.2-1

9.2.1 Columns . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1A. Spacing of Piers and Columns . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1B. Section Shape . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1C. Construction Joints . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1D. Column Reinforcement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2E. Column Loads . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

9.2.2 Column Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11A. General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11B. Slenderness Effects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11C. The Moment Magnification Method . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15D. Second-Order Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17E. Resisting Capacities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20F. Service Load Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21G. Seismic Design of Multicolumn Bents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

9.3 Abutments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.3-1

9.3.1 Size and Construction Details . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1A. Representative Types . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1B. Bearing Seats . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1C. Bearing Restraints and Girder Stops . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1D. Face Slope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1E. Sizing Abutments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1F. Class of Concrete . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1G. Abutment and Retaining Wall Junctions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4H. Construction Joints . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4I. Drainage and Backfilling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4J. Embankment at Bridge Ends . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

9.3.2 Abutment Loads . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12A. Applicable Loads . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12B. Usual Governing Load Combinations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16C. Special Handling of Lateral Forces . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16D. Loads on Girder Stop Bearings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19E. Loads on Girder Stops . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

9.0-ii July 2000



Page

9.3.3 General Design Procedures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.3-19A. Design for Stability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19B. Earth Pressure at Front Face . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19C. Design for Strength . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19D. Minimum Reinforcement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

9.3.4 Load and Reinforcement Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20A. Requirements for Pile Cap Abutments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20B. Requirements for Pile Stub Abutments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20C. Requirements for Cantilever Abutments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23D. Requirements for Spill-Through Abutments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23E. Requirements for Rigid Frame Abutments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

9.4 Retaining Walls . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.4-1

9.4.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

9.4.2 Common Types of Walls . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1A. Cantilevered Walls . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1B. Counterfort Walls . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1C. Gravity Walls . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1D. Cribbing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1E. Cylinder Pile Walls . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2F. Tieback Walls . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2G. Proprietary Walls . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2H. Slurry Walls . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4I. Rock Walls . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4J. Soil Nailing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4K. Wingwall . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4L. Noise Walls . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

9.4.3 Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4A. General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4B. Cantilever Walls . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9C. Diaphragm Walls . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10E. Tieback Walls . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

9.4.4 Miscellaneous Items . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29A. Drainage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29B. Joints . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29C. Architectural Treatment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29D. Concrete Fill for Soldier Pile Walls . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30E. Detailing of Standard Reinforced Concrete Retaining Walls . . . . . . . . . . . . . . . . . . . . . . . . . . 30

9.5 Footings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.5-1

9.5.1 Spread Footings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1A. General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1B. Load Distribution Under Footings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5C. Pedestals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5D. Footing Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

9.5.2 Pile Supported Footings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9A. General Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9B. Pile Spacings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9C. Horizontal Forces on Pile Groups . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10D. Uplift Forces . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

July 2000 9.0-iii



Page

9.6 Piles and Piling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.6-1

9.6.1 General Considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1A. Selection of Pile Type . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1B. Friction vs. Point Bearing Piles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1C. Pile Loads and Spacing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

9.6.2 Design Considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2A. Column Action . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2B. Uplift Capacity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3C. Lateral Resistance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4D. Other Considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

9.6.3 Concrete Piles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6A. Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6B. Concrete Pile Types . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

9.6.4 Steel Piling (H Piles) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

9.6.5 Timber Piles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

9.6.6 Sheet Piles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

9.6.7 Cylinder Piles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

9.7 Seals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.7-1

9.7.1 Purpose . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

9.7.2 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1A. Normal High Water Elevation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1B. Seal Vent Elevation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2C. Scour Depth . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2D. Recommended Foundation Elevation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

9.7.3 Spread Footings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2A. Seal Positively Required . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2B. Seal May Not Be Required . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

9.7.4 Pile Supported Footings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

9.8 Drilled Shafts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.8-1

9.8.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1A. Definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1B. Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1C. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

9.8.2 Types of Drilled Shafts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1A. Classification by Load Transfer to the Soil . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1B. Classification by Type of Construction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

9.8.3 Advantages and Disadvantages of the Drilled Shaft . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2A. Advantages . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2B. Disadvantages . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

9.8.4 Preliminary Soils Investigation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3A. Surface Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3B. Subsurface Investigation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3C. Methods of Investigation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3D. Subsurface Conditions Affecting Construction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

9.0-iv July 2000



Page

9.8.5 Design of Drilled Shafts for Axial Loads . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4A. Ultimate Failure vs. Excessive Settlement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4B. Factor of Safety . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4C. Spacing, Depth, Diameter Reinforcing, and Concrete Strength of Drilled Shafts . . . . . . . . . . 5

9.8.6 Design of Drilled Shafts Subject to Lateral Loads . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.8-6A. General Modeling Technique . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6B. P-Y Curves . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7C. Analysis by Computer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8D. Shaft Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

9.8.7 Construction Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9A. Dry Method . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9B. Casing Method . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9C. Slurry Displacement Method . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

9.9 Application of LRFD Code to WSDOT Foundation Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.9-1

9.9.1 Overall Design Process, Roles, and Responsibilities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

9.9.2 Definitions and Geometry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

9.9.3 Load Factors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

9.9.4 LRFD Load Combinations, Basic Equation, and Characteristic Soil/Rock Projects . . . . . . . . . . . . 7A. LRFD Basic Equation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7B. Characteristic Soil/Rock Properties and Their Use in LRFD . . . . . . . . . . . . . . . . . . . . . . . . . . 7

9.9.5 Spread Footing Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9A. Loads and Load Factor Application to Spread Footings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10B. Footing Bearing Stress and Capacity — Strength and Extreme Event Limit States . . . . . . . . . 13C. Sliding Stability for Footings — Strength and Extreme Event Limit States . . . . . . . . . . . . . . . 14D. Overturning Stability for Footings — Strength and Extreme Event Limit States . . . . . . . . . . . 15E. Overall Stability for Footings — Service and Extreme Event Limit States . . . . . . . . . . . . . . . 15F. Resistance Factors for Footing Design — Strength Limit State . . . . . . . . . . . . . . . . . . . . . . . . 16G. Design of Footings at the Service Limit State . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17H. What the Geotechnical Branch Will Provide to the Bridge Office for LRFD Footing Design 17

9.9.6 Loads and Load Factor Application to Deep Foundation Design . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

9.9.7 Drilled Shaft Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22A. Drilled Shaft Capacity — Strength and Extreme Event Limit States . . . . . . . . . . . . . . . . . . . . 23B. Uplift for Drilled Shafts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24C. Lateral Load Analysis for Drilled Shafts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24D. Group Effects for Bearing Capacity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24E. Group Effects for Uplift . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26F. Group Effects for Lateral Loads . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26G. Service Limit State Design for Drilled Shafts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28H. What Geotechnical Branch Will Provide to Bridge Office for LRFD Shaft Design . . . . . . . . 28

9.9.8 Pile Foundation Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31A. Pile Type, Pile Size, Bearing Capacity, and Estimated Tip Elevation — Strength and

Extreme Event Limit States . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33B. Determination of Minimum Pile Tip Elevations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37C. Resistance Factors for Pile Foundation Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38D. Determination of Pile Driveability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39E. What Geotechnical Branch Will Provide to Bridge Office for LRFD Pile Design . . . . . . . . . . 39

9.99 Bibliography . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.99-1

July 2000 9.0-v




9.2-A1 24-Inch Diameter Round Column Section Capacity Chart9.2-A2 36-Inch Diameter Round Column Section Capacity Chart

9.2-A3 48-Inch Diameter Round Column Section Capacity Chart

9.2-A4 60-Inch Diameter Round Column Section Capacity Chart9.2-A5 72-Inch Diameter Round Column Section Capacity Chart

9.2-A6 Column Design Flow Chart

9.2-A7 Column Design Effective Length Factors9.2-A8 Buckling Load — Round Columns

9.2-A9 Factor Charts

9.2-A10 Moment Magnification Factor9.2-A11 Column Design Example

9.3-A1 Wing Wall Notes to Designers

9.3-A2 General Wing Wall Details (applies to 9.3-A1, A-3, A-4, and A-5)9.3-A3 20-Foot Wing Wall 2:1 Slope

9.3-A4 15-Foot Wing Wall 2:1

9.3-A5 15-Foot Wing Wall 1 3/4:1 Slope9.4-A1 Earthquake Force — Retaining Wall

9.5-A1 Stress on a Rectangular Footing Normal Load Outside Kern

9.7-A1 Thickness of Foundation Seals9.7-A2 Pile Extension Below Foundation Seals

9.9-A1-1 through 5 Simplified Example for Pile Foundation Design,Including Resistance Factor Calibration


9.2-B1-1 through 4 Column Shear Example

9.3-B1-1 through 5 L-Abutment Design Example — Sheet 19.4-B1-1 through 8 Curtain Wall

P65:DP/BDM9


Substructure Design General Considerations


9.1.1 Loads

A. General

1. Substructure elements shall be designed to carry all of the loads specified in AASHTO, theGuide Specifications for Seismic Design of Highway Bridges and Chapter 4 of this manual. Goodjudgment is needed to select those load conditions which govern in order to minimize calculationtime. Computer programs such as GPLOAD, GROUPLDS, and YIELD tabulate the loadcombinations as described in Chapter 4 of this manual.

2. Consideration shall be given during design to construction loads in order to ensure that stabilityand appropriate stresses can be handled during all construction conditions. For example, a singlecolumn pier could be overloaded by placing all of the precast girders on one side of the roadwaybefore placing those on the other side. In some cases a sequence of construction is shown on theplans in order to avoid unacceptable loadings.

3. On curved bridges, the substructure units shall be designed for the eccentricity resulting from thedifferences in girder lengths. Where curved girder theory has been used in design of the super-structure, the reactions from such analysis shall be used appropriately as loads to the substructure.

B. Dead Loads

Substructures shall be designed for all anticipated dead load conditions. Sidesway effect shall beincluded where it tends to increase stresses.

C. Live Loads

Live load shall be distributed to the substructure by placing the appropriate live load wheel linereaction in the lane configuration giving maximum stresses in the substructure unit. Liveload impactis not included in some elements of the substructure. See AASHTO “Impact.” The loads are consid-ered to act directly on the substructure without further distribution through the superstructure exceptas previously noted. No consideration is given to torsional or lateral distribution. (See Figure 9.1.1-1.)Normally, sidesway effect from live load need not be considered. The computer programGTSTRUDL will include this effect.

For maximum cantilever moment on the substructure units, the outside vehicle wheel shall be placed2 feet from the curb. For the design loads in the crossbeam members, the design lanes are to beloaded to obtain the maximum moment in the member, then loaded again to obtain the maximumshear in the member. For the design loads in columns, the design lanes are to be loaded to obtain themaximum transverse moment at the top of the column, then loaded again to obtain the maximumaxial force on the column. In each case, the lane reduction factor as described in AASHTO Article“Reduction in Load Intensity” can be applied to the number of lanes actually loaded to obtain thedesign loads.

The live load wheel line reaction can be obtained by the computer programs BDS or UCONBRG.The wheel line reaction will be 1/2 the results for one lane load from BDS or the results for one wheelload from UCONBRG. For simple span structures, Appendix A of AASHTO can be used. The valuesin Appendix A are for one lane. The wheel line reaction will be 1/2 of the values listed.

April 1991 9.1 - 1



9.1 - 2



D. Wind Loads

Wind forces shall be applied to the substructure units in accordance with the loadings specified inAASHTO Article “Wind Loads.” Transverse stiffness of the superstructure may be considered, asnecessary to properly distribute loads to the substructure, provided that the superstructure is capableof sustaining such loads. Uplift wind, per AASHTO Article “Overturning Forces,” shall be included inthe design where appropriate, for example, on single column piers. Wind loads shall be appliedthrough shear keys or other positive means from the superstructure to the substructure. Wind loadsshall be distributed to the piers and abutments in accordance with the laws of statics. Transverse windcan be applied to the piers assuming the superstructure to act as a rigid beam. For large structures, amore appropriate result might be obtained by considering the superstructure to act as a flexible beamon elastic supports.

E. Earthquake Loads

Earthquake loads on elements of the substructure are describe in the Guide Specifications forSeismic Design of Highway Bridges. The resulting loads shall be taken in any horizontal direction togive maximum design load for the substructure element. Final design acceleration coefficient and sitecoefficient will be given in the Foundation Report.

Earthquake uplift forces shall be designed per Guide Specifications “Hold-Down Devices.” As a mini-mum, earthquake forces shall be considered to cause a temporary uplift on the substructure equal to10 percent of the dead load reaction of the superstructure. Where such forces can be developed, thecrossbeam, column and footing shall be designed to carry these temporary loads. For concrete super-structures built integrally with the substructure, the substructure elements shall be designed to carrytheir dead load plus all the elements below them including soil overburden as though they weresuspended from the superstructure. (Seal not included). For this condition, the ultimate downwardforce shall be 1.0 (EQ + Uplift). For structures carried on elastomeric pads or where there is nopositive vertical connection, the uplift force from the superstructure shall be neglected.

F. Prestressing Effects from Superstructure

When cast-in-place, post-tensioned superstructures are constructed monolithic with the piers, thesubstructure design should take into account frame moments and shears caused by elastic shorteningand creep of the superstructure upon application of the axial post-tensioning force at the bridge ends.Frame moments and shears thus obtained should be added algebraically to the values obtained fromthe primary and secondary Pe moment diagrams applied to the superstructure. If the equivalentuniform vertical load method presented in T. Y. Lin’s text, Reference 6.99-1, is coded into thecomputer program GTSTRUDL along with axial forces (and moments at bridge ends if they exist),then the output results will represent all of the above mentioned effects.

When cast-in-place, post-tensioned superstructures are supported on sliding bearings at some of thepiers, the design of those piers should include the longitudinal force from friction on the bearingsgenerated as the superstructure shortens during jacking. When post-tensioning is complete, the fullpermanent reaction from this effect should be included in the governing AASHTO load combinationsfor the pier under design.

January 1991 9.1 - 3



9.1.2 Concrete Design for Substructure

The class of concrete for substructure units shall normally be as specified below:

Seals Class 4000WFootings Class 4000Pedestals Class 4000Massive Piers Class 4000Columns Class 4000Std. Retaining Walls Class 3000Wing Walls Class 4000Crossbeams Class 4000Retaining Walls Class 4000Traffic Barriers Class 4000

Where retaining walls are connected directly to the bridge superstructure and color matching is important,consideration could be given to using Class 4000 in the retaining wall or using pigmented sealer in orderthat the concrete color will not vary from adjacent portions of the structure.

9.1.3 Application of Loads to Substructure Units

A. Live Load

For application of live load, see Figure 9.1.1-1.

B. Earthquake

For earthquake loading, the intermediate pier(s) of each unit of a multispan continuous structure shallbe designed to resist the entire longitudinal earthquake force for that unit (unless the end piers are anintegral part of the superstructure). The calculated longitudinal movement shall be used to determinethe shear force developed by the pads at the abutments. The Modulus of Elasticity of Neoprene at70˚F (21˚C) shall be used for determine the shear force. However, the force transmitted through abearing pad shall be limited to that which causes the pad to slip. For single-span structures supportedon pads, see Guide Specifications “Design Requirements for Single Span Bridges.”

9-1:V:BDM9

9.1 - 4 April 1991


Substructure Design Piers

9.2 Piers

9.2.1 Columns

A. Spacing of Piers and Columns

1. Pier Spacing

Piers normally are spaced to meet the geometric and aesthetic requirements of the site and togive maximum economy for the total structure. Tall piers will generally justify greater spacing(longer spans) than short piers. Difficult and expensive foundation conditions will also justifylong spans. Good judgment must be used in determining pier locations on each job.

2. Multicolumn Spacing

Columns shall be spaced to give maximum structural benefit except where aesthetic considera-tions dictate a modification. The spacing should be selected so that column moments are mini-mized for dead load. Multiple columns should be considered if earthquake loads control thecolumn design.

3. Changing Spacing

Column and pier spacing is usually set at the preliminary plan stage based on preliminaryanalysis.

The designer may, for structural reasons, after column spacing in a multicolumn pier or changefrom a single-column pier to a multicolumn pier. Multicolumn piers are generally better suitedfor handling lateral loads due to wind and/or earthquake. These changes must be reviewed by thesupervisor, who will determine if the changes need to be reviewed by the Bridge PlanningEngineer or the Bridge Architect.

Pier spacing is usually not changed after the preliminary plan stage. However, if substantialstructural improvement and/or cost savings can be realized, changes can still be made. Thedesigner should discuss the possibilities of changing the pier spacing or skew with his/her super-visor at the earliest possible time. Changes in pier spacing could affect the Materials Lab’s soilsinvestigation.

B. Section Shape

Column section shape shall be selected for strength and aesthetics and shall give proper dimensionsfor long column action. Columns should be designed so that construction is as simple and repetitiousas possible. The diameter of circular columns should be a multiple of one foot. Rectangular sectionsshould have lengths and widths that are multiples of 3 inches. Long rectangular columns are oftentapered to reduce the amount of column reinforcement required for strength. Tapers should be kept toone plane for ease of construction.

The column shape is determined at the preliminary plan stage. Changes to column size and shapemay be made by the designer. Any changes must be reviewed by the supervisor, who will determineif the change needs to be reviewed by the Bridge Planning Engineer or the Bridge Architect.

C. Construction Joints

Construction joints in columns are normally placed at the top of the footing or pedestal and thebottom of the crossbeam. Optional construction joints with roughened surfaces should be provided atapproximately 30-foot vertical spacing.

January 1991 9.2 - 1



D. Column Reinforcement

1. Longitudinal Reinforcement

The maximum reinforcement ratio (ratio of the steel area to the gross area of the section - As/Ag)shall be 0.06. The minimum reinforcement ratio shall be 0.01. The reinforcement ratio may bereduced to 0.005 provided that all loads can be carried on a reduced section of similar shape such thatthe selected reinforcement ratio is equal to .01. All dimensions of the section shall be reduced by thesame ratio to obtain the reduced section. The properties of the reduced section should not be used tocompute K1/r ratios for long columns.

Longitudinal reinforcement should extend into the footing and rest on the bottom mat of footingreinforcement with standard 90° hooks. Embedment must be at least 1.25 1dh (1dh is developmentlength of a standard hook). Longitudinal reinforcement should extend into the crossbeam at least1.25 1d. Hooks should be avoided in the crossbeam. If the crossbeam is not deep enough todevelop the bars, 180° hooks generally provide less congestion. A detailed clearance check isessential at the column/crossbeam connection.

2. Splicing of Longitudinal Reinforcement

Column reinforcement shall not be spliced at points of maximum moment, plastic hinge loca-tions, and in columns less than 30 feet long between the top of footing and the bottom of cross-beam. Splices of No. 11 and smaller bars shall be made by lapping the bars. When space islimited, No. 11 and smaller bars can be spliced by welds, an approved mechanical butt splice, orthe top bar can be bent inward (deformed by double bending) to lie inside and parallel to the barsbelow. When the bar size exceeds No. 11, welded splices or an approved mechanical butt spliceshall be used. The smaller of the bars being spliced determines the type of splice required. Theappropriate weld details shall be shown on the plans and approved mechanical splices are cov-ered in the Standard Specifications. All splices of No. 7 and larger bars shall be staggered. Forusual practice in splicing, see Figure 9.2.1-1.

Show splice locations on the plans. Where a column is to have an intermediate construction joint,the shortest bar shall project above the joint 60 bar diameters in the case of lap splicing, or20 bar diameters in the case of welded splices. If the splice is indicated on the plans as“optional,” the method of payment for splice steel shall be defined in the Special Provisions.

The Guide Specifications require that splices fall within the middle one-half of the column. Forextremely tall columns (where a 60-foot bar length cannot reach the middle half), splices shouldnot be closer than 30 feet from the columns ends.

3. Ties and Spirals

Ties or spirals are required in all columns to resist shear forces and to maintain the column’sstructural integrity after catastrophic forces have severely cracked the outer shell. Two sectionviews of transverse reinforcing differentiating the column ends and the typical middle sectionsshould be shown.

The column end section will only be used for the confinement zones, where it must both provideconfinement and resist shear. Hoops and ties in the confinement zones are normally No. 6 bars.No. 7 bars can be used for hoops and ties, but the concrete cover (1 inch to the tie) must bemaintained using the standard radius for a No. 7 bar. Hoops can be made up of several reinforc-ing elements with 135° hooks extending into the core a minimum of 10 diameters or 6 inches.Ties can have a 180° hook on one end and a 90° hook on the other end. The 180° hook is to bealternated both horizontally and vertically with the 90° hook. The tie is to engage the peripheral

9.2 - 2 October 1993



hoop and be tied to the longitudinal reinforcement. The designer should check that the 180° hookcan fit between adjacent hoops and longitudinal bars.

Where confinement is not required, the transverse reinforcing needs to resist the column shear. Cross-ties outside the confinement zones are usually No. 4 or No. 5 bars. Cross-ties should be spaced so asto leave horizontal openings of 18 inches to 21 inches to allow for placing and consolidating concrete.

The area of the transverse reinforcement required to resist the column shear is defined in Article“Column Shear and Transverse Reinforcement” of the Guide Specifications and AASHTOArticle “Shear.” The area of transverse reinforcement required for confinement is determinedfrom Guide Specifications Article “Spacing of Transverse Reinforcement for Confinement” forspirals and ties. The area of transverse reinforcing in the confinement zones is the larger of thetwo requirements. Transverse reinforcement may be provided by spirals, hoops, or cross-ties. SeeDesign Example 9.2B-1 through -5.

The general arrangement for column spirals in circular columns is shown in Figures 9.2.1-1 and2. Note that spirals are to be used for all circular columns including and less than 8 feet diameter.Standard sizes for column spiral use are No. 4 or No. 5 deformed bar, 1/2-inch diameter or5/8-inch diameter plain steel bar, or W20 or W31 cold drawn wire. Label these spirals with allthree options (for example: No. 4, 1/2-inch diameter or W20 spiral). The pitch shall allow for1 inch or 11/3 times the maximum coarse aggregate size clearance to allow aggregate to flowthrough. Anchor spirals at the top and the bottom with a hook that extends into the core adistance of 10 inches past the bend. Twelve feet zero inches is the maximum height normallyfabricated. Show full height of the spiral in the bar list; the fabricator will provide requiredsplices. For diameters larger than 8 feet 0 inches, hoops are to be used.

Constant dimension rectangular columns shall be detailed as shown in Figure 9.2.1-4 with the useof spirals. The same provisions as a spirally-reinforced circular column apply.

The general arrangement for ties in tapered rectangular columns is shown in Figures 9.2.1-5through 5. The maximum vertical spacing for hoops and ties in the confinement zones and overthe length of lap splices is 4 inches for Seismic Performance Categories C and D and 6 inches forSeismic Performance Categories A and B. The vertical opening between layers of confinementreinforcement should be at least 21/2 inches to allow aggregate to flow through. The spacing at lapsplices should be shown on the splice detail and tied to the splice location.

4. Location of Confinement Zones

The typical locations of confinement zones for circular columns are shown in Figure 9.2.1-2 andfor tapered rectangular columns in Figure 9.2.1-3. The locations of confinement zones are thesame for columns of any shape.

Column ends that are framed into footings, multicolumn crossbeams, or longitudinal frames musthave confinement reinforcing over the maximum of:

a. The lesser of:

(1) 1/6 the clear column height, or

(2) The maximum column dimension. For wall type piers where plastic hinging occurs onlyalong the weak axis, use the short dimension.

b. 18 inches.

October 1993 9.2 - 3



Confinement reinforcing is required to extend into these framed footings, multicolumn cross-beams, etc., the larger of one-half the maximum column dimension and 15 inches, but not morethan three-quarters the depth of the crossbeam or footing. Crossbeam and footing steel can becounted as confinement steel as long as it is fully developed at the extended planes of the sideof the column.

5. Column Hinges

The area of the hinge bars in square inches is as follows:

As =

Where:

Pu is the factored axial loadVu is the factored shear loadFy is the reinforcing yield strength (60 ksi)θ is the angle of the hinge bar to the vertical

The development length required for the hinge bars is 1.25 times that described in AASHTOArticle “Development of Flexural Reinforcement.” Figure 9.2.1-6 shows some typical hingedetails. Space the ties and spirals to satisfy Article “Spacing of Transverse Reinforcement forConfinement” of the Guide Specifications, AASHTO Article “Shear,” or a maximum of12 inches (6 inches if longitudinal bars are bundled). Premolded joint filler should be used toassure the required rotational capacity. There should also be a shear key at the hinge bar location.

When the hinge reinforcement is bent, additional confinement reinforcing may be necessary totake the horizontal component from the bent hinge bars. The maximum spacing of confinementreinforcing for the hinge is the smaller of that required above and the following:

Smax =

Where:

Av, Vs, and d are as defined in AASHTO Article “Notations” and 1h is the distance from thehinge to where the bend begins.

Continue this spacing one-quarter of the column width (in the plane perpendicular to the hinge)past the bend in the hinge bars.

E. Column Loads

Loads applied to the columns consist of reactions from loads applied to the superstructure and loadsapplied directly to the columns. The load combinations are described in AASHTO Article “Combina-tion of Loads” and in Chapter 4 of this manual. The Earthquake Load Combination is described in theGuide Specifications, Article “Design Forces for Structural Members and Connections.” For longcolumns, it may be advantageous to reduce the amount of reinforcement as the applied loads decreasealong the column. In these cases, load combinations need to be generated at the locations where thereinforcement is reduced. Computer programs such as YIELD, GROUPLDS, and GPLOAD can beused to combine the loads.

+ + Vu2(Pu) Pu

2 1/2

2 4[ ]0.85 Fy Cos θ

Av Fy

Pu Tan θ Vs0.85 lh d[ ]+

9.2 - 4



9.2 - 5



Spiral Details for Circular or Rectangular ColumnsShow splice details on the plans.

Figure 9.2.1-2

9.2 - 6 October 1993



January 1991 9.2 - 7



Constant Rectangular Column SectionFigure 9.2.1-4

9.2 - 8 November 1993



Tapered Rectangular Column TiesFigure 9.2.1-5

July 1994 9.2 - 9



9.2 - 10



9.2.2 Column Design

A. General

Understanding the effects on long columns due to applied loads is fundamental in their design. Thefollowing is intended to give further guidance of long column design.

1. Modes of Failure

A column subject to axial load and moment can fail in several modes. A “short” column can faildue to crushing of the concrete or to failure of the tensile reinforcement. A “long” column canfail due to elastic buckling even though, in the initial stages, stresses are well within the normalallowable range. Failure of a long column is normally a combination of stability and strengthfailure which might occur in the following sequence:

a. Axial load is applied to the column.

b. Bending moments are applied to the column, causing movement of the center line withrespect to the line of action of the axial loads.

c. Axial loads act eccentrically to the new column center line producing P-∆ moments whichare additive to applied moments.

d. The P-∆ moments increase the deflection of the column and lead to higher eccentricities andmoments.

e. At some curvature (bending strain), failure of the concrete or reinforcement results in suddenfailure of the column.

2. Peculiarities of Bridge Columns

Unlike building columns, bridge columns are required to resist lateral loads through bending andshear. As a result, these columns may be required to resist relatively large applied moments whilecarrying nominal axial loads. In addition, columns are often shaped to give good appearance.This results in complicating the analysis problem with non-prismatic sections.

B. Slenderness Effects

The goal of a slenderness analysis is to estimate the additional bending moments in the columns andthe foundations that are developed as a result of axial loads acting upon the deflected structure.

The following is intended to supplement and clarify the provisions of the AASHTO Specifications.Valuable information is available in the Commentary on Building Code Requirements for ReinforcedConcrete, ACI 318 R-83.

Two primary analysis methods exist:

Method 1: The approximate moment magnifier method detailed in AASHTO Article “ApproximateEvaluation of Slenderness Effects.”

Method 2: A second-order structural analysis which accounts directly for the axial forces.

The decision as to which method to use is based upon a consideration of the slenderness ratio (kLu/r)of the column(s). Method 1 is allowable if kLu/r ≤ 100. Method 2 is recommended (by AASHTO) forall situations and is mandatory (Article “Slenderness Effects in Compression Members”) forkLu/r > 100.

January 1991 9.2 - 11



When compatible assumptions are made, Method 1 is generally more conservative and is easier toapply. For certain structures, however, use of Method 2 can lead to significant economy in the finalstructure.

Determination of (kLu/r) requires an estimate of the value of the effective length factor, k. Forunbraced columns, k ≥ 1.2; for braced columns, k ≤ 1.0.

1. Braced or Unbraced Columns

The AASHTO Specifications use the expression “compression members braced against side-sway” in order to establish an effective column length. In a braced member with loads applied atthe joints, any tendency toward sidesway is resisted by other members.

In building design, bracing is commonly provided by diagonal bracing, shear walls, or similarelements. Bracing for some columns is provided by other columns within a story. Design proce-dures developed for these situations are not readily adaptable to bridge design since typicalbridge columns tend to be dominated by lateral loading while building columns are usuallydominated by axial loading.

In the transverse direction, sidesway, due to axial loads may be resisted by lateral flexure of thesuperstructure as a result of the connections at the end piers. The usual practice is to consider thepiers as unbraced in the transverse direction.

Normal bridge practices is to provide expansion bearings at the end piers. Thus, the columns mustresist the longitudinal lateral loading and therefore are considered unbraced. The only time acolumn can be considered as braced in the longitudinal direction is when it is framed to a bracingmember that does not let the column displace more than L/1500, where L is the total columnlength. In this case, the bracing member must be designed to take all of the horizontal forces.

2. Effective Length Factor, k

The computation of the effective length factor for columns can be readily accomplished by usingthe charts shown on Design Aid Sheet 9.2-A7. The effective length factor (k) should becomputed for both axes of the column. These charts are appropriate only for prismatic members.For nonprismatic columns, k is not used in the column design, a second order analysis is moreappropriate.

G on these charts is the ratio of the sum of the flexural stiffnesses of the columns to the sum ofthe flexural stiffnesses of the restraining members.

a. Gtop

(1) Transverse Direction

When the connection between a single column pier and the superstructure is momentresisting, the torsional rigidity of the superstructure may be accounted for in the compu-tation of the restraining stiffness. In this case, Gtop can be computed as follows:

9.2 - 12 April 1991



Gtop =

where:

Ec is the modulus of elasticity of the columnIc is the column moment of inertia computed for the gross sectionLc is the column lengthEs is the modulus of elasticity of the superstructureLs is the average length of the adjacent connecting spansRs is the torsional rigidity of the superstructure (the I11 value computed for the computer program SEISAB)µs is Poisson’s ratio for the superstructure

(2) Longitudinal Direction

When the connection between the pier and the superstructure is moment resisting, Gtopcan be computed as follows:

Gtop =

where:

Ec, Ic, and Lc are as defined above for the columnEs and Ls are for the connecting spansn = 3 for an end span; n = 4 for an intermediate span with fixity at both endsIs can be taken as the I33 value computed for the computer program SEISAB

AASHTO Article “Approximate Evaluation of Slenderness Effects” requires that theeffect of cracking and reinforcement on the relative stiffnesses must be considered whendetermining k. The use of 1.2Ic for the column stiffness approximates the effect of thecolumn reinforcement. The use of 0.5Is and 0.5Rs for the superstructure accounts for theeffects of cracking. More rational approaches may be considered in some cases.

b. Gbot

By definition, Gbot = Kcol/KR, where:

Kcol = flexural stiffness of the columnKcol = 4Ec(1.2Ig)Lu for a prismatic columnKR = rotational stiffness constant describing the restraint of the foundation

The rotational stiffness constant, KR, is related to the base fixity, γ, as follows:

KRGiven KR, γ =

KR + Kcol

or given γ, KR , = [γ /(1- γ)]*Kcol

Therefore, Gbot = (1- γ)/γ

Note that 0 ≤ γ ≤ 1.0(free) (fixed)

January 1991 9.2 - 13

4Ec(1.2Ic)/Lc9.5EsRs/2(1+µs)Ls

4Ec(1.2Ic)/LcΣnEs(0.5Is)/Ls



Procedures for establishing KR and/or γ will be discussed in Chapter 4, “FoundationModeling.” In most cases, there is a substantial amount of uncertainty involved in thecomputation of KR or γ. Therefore, care must be taken to use conservative values in theslenderness analysis.

For preliminary design or when detailed foundation information is not available, an approxi-mate, conservative value for base fixity, γ, should be used. In this case, Gbot should not betaken ≤ 1.0.

(1) Piers on multiple rows of piles are 100 percent fixed at the connections to the piles.

(2) Piers on a single row of piles are pinned at the connection to the piles.

(3) Piers on spread footings:

(a) allowable* soil pressure of 3-6 TSF; γ = 0.3,

(b) allowable* soil pressure of 6-9 TSF; γ = 0.4,

(c) allowable* soil pressure 9 TSF (competent rock); γ = 1.0.

*at service load level

If additional information becomes available, the effective length of the column(s) should berecalculated. When the new effective length is significantly different, the design should bechecked using the new values.

Lower limits on k values:

k ≥ 1.2 for unbraced columns with rotational restraint at both ends,

k ≥ 2.1 for unbraced columns with no rotational restraint at one end (i.e., cantilever column).

For braced columns, a value of k = 1.0 will normally be used.

c. Alternate Procedure for Determining Base Fixity, γ

The moment induced in columns is dependent on the rotational restraint at the top and the degreeof fixity at the base. In turn, the base fixity is dependent on the connection between the columnand the footing, and the resistance of the soil to footing rotation.

For most cases, it is adequate to assume a base fixity between 0.5 and 1.0, but in some cases amore detailed analysis is warranted. The degree of fixity between a column and a footing is afunction of several factors including the size and spacing of anchor bolts, thickness of base plate,grout strength, etc. The degree of fixity or restraint, γ, between the footing and soil, assuming afixity of 1.0 in the column-footing connection, can be calculated from:

kIfγ =kIf + 4EccIc/h

where:k = Soil modulus, similar to “Modulus of Subgrade Reaction,” used in paving design.

Where this value is not available, it can be estimated from Figure 9.2.2-2. Becausethe equation is not sensitive to values of k, these values will usually be adequate,psi/in.

If = Moment of inertia of the plan of the footing in the direction of bending, in.4.Ic = Moment of inertia of the column, in.4.h = Height of column, in.Ecc = Modulus of elasticity of concrete in column, psi.

9.2 - 14 April 1991



Figure 9.2.2-2 Approximate relationship between allowable soil bearing value and subgrademodulus, k.

C. The Moment Magnification Method

This method can lead to rapid column design. The procedure for its use is well defined in theAASHTO Specifications. Design Aid Sheets 9.2-A1 through 9.2-A6 can be helpful for design by thismethod.

1. General Procedure

The following information is required:

• Column geometry and properties: E, I, Lu, and k.

• All ultimate group loads and column understrength factors, φ (see Figure 9.2.2-1), obtainedfrom conventional elastic analyses using appropriate stiffness and fixity assumptions.

The basic procedure is as follows:

a. Compute Pc for all columns per AASHTO Article “Approximate Evaluation of SlendernessEffects.”

b. Check Pu* ≤ .7Pc. Pu* is the load at the top of the column plus a portion of the columnweight: Pu* = Putop + 1/3 * factored column weight. This ensures that Euler buckling is notapproached.

c. Compute the moment magnification factors as specified in AASHTO using Pu*. Since φ mayvary for different columns for the same load group, Equation 8-41a is modified as follows:

d. Compute the magnified factored moments, Mc, as specified in AASHTO Equation 8-40. M2bis defined by the specifications as the bending moment due to gravity loads which result inno appreciable sidesway (∆ < Lu/1500). Since creep, shrinkage, post-tensioning effects, andthermal deformations do not result in sidesway of the entire frame, it is considered appropri-ate to include those moments in the definition of M2b. This provision applies only to thosecolumns framed together by the superstructure and/or a crossbeam. Note that the use ofEquation 8-40 will generally require that Pc be computed for both the unbraced and thebraced conditions.

April 1991 9.2 - 15

δs = ≥ 1.011-(ΣPu*/ΣφPc)



PHI FactorFigure 9.2.2-1

9.2 - 16 April 1991



2. Critical Load, Pc

The critical load, Pc, can be readily computed for a prismatic column. For a nonprismaticcolumn, however, the computation becomes more difficult. Numerical methods are available forsolving this problem accurately; the computer program COLUMN can be used if an estimate ofthe effective length factor (k) is made. Other numerical methods require that the rotationalrestraint at the column ends be input directly (the effective length is not required).

3. Biaxial Bending

When using the AASHTO specifications regarding bending about both principal axes, the appro-priate values of Pc and moment magnifiers must be computed for each axis separately.

4. Yield Program

Economy in design time can be achieved by using the program YIELD. The program groups theAASHTO loads, magnifies the moments, and checks or designs the column steel. Under thecheck mode, it will determine the Plastic Hinging Moment Envelope to determine foundationloads. The moments are all assumed to be acting on an unbraced column; therefore, the resultswill be conservative. If magnification factors controlling the column design exceed 1.4, thedesigner should use either the more correct method described above or a second-order analysisdescribed in the following section.

D. Second-Order Analysis

1. General

A second-order analysis which includes the influence of axial loads on the deflected structure isrequired under certain circumstances and may be advisable in others. It can lead to substantialeconomy in the final design of many structures.

Performing a second-order analysis can be difficult and time consuming. The designer shouldconsider all of the options carefully and should discuss the situation with the supervisor beforeproceeding with the analysis.

The ACI Building Code Commentary (ACI 318 R-83) discusses some general aspects of carryingout a second-order analysis. Some additional aspects which should be considered are given here.

Previous practice has been to analyze columns separately. This is appropriate only for thosecolumns that are isolated structurally from the frame as a whole (with sliding bearings in thedirection of interest).

For columns framed together, the entire frame should be analyzed as a unit. Analyzing individualcolumns results in overly conservative results for some columns and nonconservative results forothers. This is a result of redistribution of the lateral loads in response to the reduced stiffnessesof the compression members. For example, in a bridge with long, flexible columns and withshort, stiff columns both integrally connected to a continuous superstructure, the stiff columnswill tend to take a larger proportion of the lateral loading as additional sidesway under axialloads occurs.

For a second-order analysis, loads are applied to the structure and the analysis results in memberforces and deflections. It must be recognized that a second-order analysis is non-linear; thus, thecommonly used principle of superposition may not be applicable. The loads applied to the struc-ture should be the entire set of factored loads for the load group under consideration. The analy-sis must be repeated for each group load of interest. The problem is complicated by the fact thatit is often difficult to predict in advance which load groups will govern.

January 1991 9.2 - 17



As with a conventional linear elastic frame analysis, various assumptions and simplificationsmust be made in regard to member stiffness, connectivity, and foundation restraint. Care must betaken to use conservative values for the slenderness analysis. For compression members, use ofthe equations for EI stated in AASHTO Article “Approximate Evaluation of Slenderness Effects”will give an adequately conservative value. For concrete beams, use EI = 0.5EcIg. This is inexactin that reinforcement, cracking, load duration, and their variation along the members are notexplicitly taken into account. More precise methods may be used. Foundation restraint will oftenbe modeled as rotational springs (lateral and vertical springs may also be incorporated). A stiff-ness matrix may be computed to represent the soil-foundation interaction. Procedures to computethese values will be discussed in Chapter 4, “Modeling Foundations.”

For certain loadings, column moments are sensitive to the stiffness assumptions used in theanalysis. For example, loads developed as a result of thermal deformations within a structure maychange significantly with changes in column, beam, and foundation stiffnesses. Accordingly,upper and lower bounds on these stiffnesses should be determined and the analysis repeatedusing both sets to verify that the governing load has been found.

The specifications include the strength reduction factor, φ, in the computation of the momentmagnifiers. No guidance is given with respect to the use of φ in a second-order analysis scheme.The following procedure is adopted:

• For the lower-bound analysis, use the reduced member stiffnesses discussed earlier and thelower-bound foundation restraint stiffness values. Multiply the member stiffnesses by theappropriate reduction factor: φ = 0.9 for beams, and φ varies for columns.

• For the upper-bound analysis, use stiffness assumptions normally employed for elastic analy-sis; IB = Ig, IC = 1.2Ig, and the upper-bound foundation restraint stiffnesses. The stiffnessesfor the upper-bound analysis should not be reduced (φ = 1.0). E for concrete varies withloading type; thus, some superposition of results may be required in spite of the non-linearityof the analysis. In most cases, the non-linear effects will be small for the relatively stiffupper-bound analysis. Judgment is required.

Note: Computations of effective length factors, k, and buckling loads, Pc, are not required for asecond-order analysis, though they may be helpful in establishing the need for such an analysis.In general, if magnification factors computed using the AASHTO Specifications are found toexceed about 1.4, then a second-order analysis may yield substantial benefits.

Methods for satisfying the requirements of a second-order analysis are given as follows:

a. The preferred method for performing a second-order analysis of an entire frame or onisolated single columns is to use the program GTSTRUDL with appropriate stiffness andrestraint assumptions. The columns are divided into a number of individual segments(10 gave good results in tests). The factored group loads (including the self-weight of thecolumns) are applied to the frame. The model is then analyzed using the nonlinear optionavailable in GTSTRUDL. The final design moments are obtained directly from the analysis.Care must be taken in modeling complex structures as the cost of a nonlinear analysis can behigh.

b. For isolated single columns, the program COLUMN gives the magnified moments directly(P-∆ moments are added to the applied moments using an iterative process until stability isreached).

9.2 - 18



c. For isolated single columns, the program LPILE1 can be manipulated to also give the magni-fied moments directly.

Note: Neither of these programs, COLUMN nor LPILE1, includes the effect of the columnweight; therefore, the axial load must be adjusted as follows: Pu* = Pu + 1/3 * factoredcolumn weight. Care and judgment must be used as they have limitations on the boundaryconditions and configurations that may be analyzed.

d. For isolated single columns, the iterative hand method is sometimes economical. Loadsaffected by column stiffness (temperature, shrinkage, and post tensioning) cannot beanalyzed this way.

The factored load is applied to the column and the deflections are computed along the lengthof the member taking into account restraints top and bottom and the effect of variations inmoment and I along the length of the column. The load is adjusted for the P-∆ moment. Theadjusted loads are applied to the column and the deflections are computed again. The deflec-tions usually converge in about five iterations (deflections from last cycle are within 5 per-cent of the total deflections). If not, the column is too flexible and is unstable for that load.The program LOTUS can be used to do the repetitious hand calculations. Column EI mustbe adjusted according to AASHTO Article “Approximate Evaluation of SlendernessEffects.” Pu* including one-third the factored column weight must not exceed .7Pc.

*At service load level.

2. Special Provisions for Seismic Loading

The following applies to those structures designed according to the AASHTO Guide Specifica-tions for Seismic Design.

The seismic analysis program SEISAB does not include the secondary effects of the axial loads.Therefore, a modified approach is necessary to perform a second-order analysis for this loading.The moment magnifier method magnifies the Group VII loads as follows:

Mu = δbMDL + δs(MEQ/R)

where MEQ is the elastic seismic moment obtained from SEISAB and R is the response modifica-tion factor defined in the Guide Specifications.

The design philosophy of the Guide Specifications may be summarized as follows:

The columns are designed to hinge (fail in flexure) at a specified percentage of the computedfully elastic seismic moment. This will occur at a deflection and shear force corresponding toδsMEQ/R. At this point, inelastic deflection will continue to some unknown maximum, butbending moments and shear forces in the columns will theoretically not increase.

Therefore, the problem is to come up with an approach to compute the additional design momentdue to slenderness effects, M, such that:

MEQ/R + M = δsMEQ/R.

A suggested second-order analysis is given as follows:

Estimate the maximum primary elastic deflection of the frame:

∆PR = ∆EQ/R

where ∆EQ is the CQC elastic deflection computed from SEISAB.

January 1991 9.2 - 19



Apply ∆PR to a GTSTRUDL model of the frame. This will yield a set of primary deflectionsand forces, MPR and VPR, corresponding to ∆PR. (Note that for some structures, these forcesmay not agree exactly with the SEISAB results.)

Apply the external gravity loadings and the primary lateral force determined above to theoriginal model. Use the nonlinear option of GTSTRUDL to analyze the structure. The finalmoments (MF) obtained are then equal to the sum of the primary moments (MPR) and theadditional moments due to slenderness effects (M).

Thus, the design moments for the columns are given by:

Mu = MDL + MEQ/R + M

where:

M = MF - MPR obtained from the GTSTRUDL analysis.

Note: The response modification factor, R, used for footing or pile design is generally less thanthe value used for the columns. Thus, a separate analysis may be required to obtain the footingdesign moments.

E. Resisting Capacities

Once magnified moments have been established, the resisting capacity of the column section must bemade adequate to carry this magnified moment. The appropriate capacity reduction factor (φ) must beused in the computation of this resisting capacity. In addition, the superstructure and the foundationmust also be designed to resist this magnified moment.

1. Reduction Factor (φ)

According to AASHTO Article “Design Strength,” the reduction factor (φ) may be increasedlinearly from the value for compression members to the value for flexure as the design axial loadstrength, φPn, decreases from .10fc′Ag or the balanced load strength φPb, whichever is smaller, tozero. Since moment capacities are based on the factored axial load, Pu, this axial load is equal tothe design axial load strength, or Pu = φPn. The balanced load strength can be less than .10fc′Agwhen the area of reinforcement in tension of the column exceeds .02Ag. This is rarely the case incolumn design but can be the case in pile design.

According to the Guide Specifications Article “Flexural Strength,” for Seismic PerformanceCategories C and D, the value of φ for Group VII Loading may be increased linearly from .50 tothe value for flexure when the stress due to the maximum axial load decreases from .20fc′Ag tozero.

Figure 9.2.2-1 shows a graph of φPn versus φ. This graph is appropriate unless φPb is less than.10fc′Ag. Computer program YIELD computes φ according to this graph.

2. Moment Capacity

Computer programs such as YIELD and ULT2AX can be used to compute the moment strength,φMn. The program YIELD computes the moment strength in the direction of the resultant Mxand My. The program ULT2AX computes the moment strength in the direction given in theinput; therefore, the φMn curve must be plotted for the axial load strength, Pn. The resultant ofMux and Muy must fall within the curve.

9.2 - 20



F. Service Load Requirements

When widening bridges originally designed by the allowable stress method, the analysis procedure forthe Moment Magnification Method is as follows.

Compute the capacity of the column by load factor design procedures. The allowable service loadcapacity of the column shall be taken as:

0.35 φ MnMallow =

δ

where:

Cmδ =1 - 2.5P/Pc

and P is the service axial load

G. Seismic Design of Multicolumn Bents

The Guide Specifications require that connections to the superstructure be designed for either theelastic demand moment (Seisab Load Case 2) at the top of the column using an “R” of “1,” or theplastic moment capacity of the top of the column, whichever is less. These column moments are to becarried into the crossbeam and accounted for in the design. (For a center column of a three-columnbent, the moment is distributed to the crossbeam on either side of the column.) The seismic designmoment for the crossbeam would then be the moment at the face of the column or the equivalentsquare column.

9-2WORK:V:BDM3

January 1991 9.2 - 21


Substructure Design Abutments

9.3 Abutments

9.3.1 Size and Construction Details

A. Representative Types

Several representative types of abutments that have been used by the Bridge and Structures Divisionare shown in Figure 9.3.1-1. The types shown are intended for guidance only and may be varied tosuit the type of bridge being designed.

B. Bearing Seats

The bearing seats shall be wide enough to accommodate the size of the bearings used with a mini-mum edge dimension of 3 in. and satisfy the requirements of the Guide Specification for SeismicDesign of Highway Bridges, Article “Design Displacements.” On L-abutments, the bearing seatshould be sloped away from the bearings to prevent a build up or pocket of water at the bearings. Thesuperelevation and profile grade of the structure should be considered for drainage protection.Normally, a 1/4 in. drop across the width of the bearing seat is sufficient.

C. Bearing Restraints and Girder Stops

All structures shall be provided with some means of restraint against lateral displacement at theabutments due to earthquake, temperature and shrinkage, wind, earth pressure, etc. Such restraintsmay be in the form of concrete hinges, concrete girder stops with or without vertical elastomericpads, or pintles in metal bearings. Other solutions are possible. Article “Connection Design Forces” of theGuide Specifications for Seismic Design of Highway Bridges describe longitudinal linkage forceand hold-down devices required.

To eliminate alignment conflicts between prestressed girders and girder stops, prestressed girdersshould be placed in final position before girder stops are cast. Allow 1/8 in. clearance between theprestressed girder flange and the girder stop to prevent binding. Incorporate details of Figure 9.3.1-2in bridge plans.

D. Face Slope

A vertical abutment wall or a 1:4 slope is used on the front face of the abutment as shown on DesignAid Sheets 9.3-A2 through 9.3-A6. On very high abutments, where a 1:4 slope would create anexcessively wide bearing seat, the slope should be adjusted or using the slope only at the exposedleading edge of the abutment and wing wall while leaving the remaining abutment wall surface verti-cal. On abutments with fractured fin surface, the front face should be vertical to match the fracturedfins.

E. Sizing Abutments

Other portions of the abutment shall be sized for stress. As indicated in Figure 9.3.1-1, additionalstem width, where required, may be obtained by sloping the back face of the wall.

On extremely high walls (30 feet and above) subjected to large earth pressures, consideration shouldbe given to using counterfort construction. See Section 9.4.2 B of this manual, Counterfort RetainingWalls.

F. Class of Concrete

The class of concrete used in abutments and standard wingwalls shall be Class 4000.

April 1991 9.3 - 1



9.3 - 2



January 1991 9.3 - 3



G. Abutment and Retaining Wall Junctions

Vertical expansion joints extending from the top of footings to the top of the abutment are usuallyrequired between abutments and adjacent retaining walls to handle anticipated movements. Theexpansion joint is normally filled with premolded joint filler which is not water tight. There may becircumstances when this joint must be water tight; 1/8 butyl rubber may be used to cover the joint.The open joint in the barrier should contain a compression seal to create a water tight joint. Figure9.3.1-3 shows typical details that may be used. Aesthetic considerations may require that verticalexpansion joints between abutments and retaining walls be omitted. This is generally possible if theretaining wall is less than 60 feet long.

The footing beneath the joint may be monolithic or cast with a construction joint. In addition, dowelbars may be located across the footing joint parallel to the wall elements to guard against differentialsettlement or deflection. For further discussion, see Section 9.4, Retaining Walls.

Particular attention should be given to the horizontal reinforcing steel required at the junction betweenabutment and retaining wall. To account for the resistance to rotation found in retaining walls andcantilever abutment walls rigidly connected to one another in a U-shape (as seen in Plan View), anequivalent fluid pressure of 45 pcf shall be assumed for design. This increased loading can normallybe reduced to 30 pcf at a distance, from the junction between the abutment and retaining wall, equalto the average height of the wall under design. At this location, active state soil pressure is assumedto be developed.

H. Construction Joints

To simplify construction, vertical construction joints are often necessary, particularly between theabutment and adjacent wing walls. Construction joints should also be provided between the footingand the stem of the wall. Shear keys shall be provided at construction joints between the footing andthe stem, at vertical construction joints or at any construction joint that requires shear transfer. TheStandard Specifications cover the size and placement of shear keys. The location of such joints shallbe detailed on the plans. Construction joints with roughened surface can be used at locations (exceptwhere needed for shear transfer) to simplify construction. These should be shown on the plans andlabeled “Construction Joint With Roughened Surface.” When construction joints are located in themiddle of the abutment wall, a pour strip should be used for a clean joint between pours. Details ofthe pour strip should be shown in the plans. See Section 5 of this manual and Design Aid Sheets9.3-A1 through A6 for further guidance on construction joints.

I. Drainage and Backfilling

Three-inch (3 in.) weep holes shall be provided in all bridge abutment walls. These shall be located6 inches above the final ground line at about 12 feet on centers. In cases where the vertical distancebetween the top of the footing and the bearing seat is greater than 10 feet, additional weep holes shallbe provided 6 inches above the top of the footing. No weep holes are necessary in cantilever wingwalls where a wall footing is not used.

The details for gravel backfill for walls, underdrain pipe and backfill for drains shall be indicated onthe plans. The gravel backfill for walls shall be provided behind all bridge abutments. The underdrainpipe and gravel backfill for drains shall be provided behind all bridge abutments except abutments onfills with a stem wall height of 5 feet or less. When retaining walls with footings are attached to theabutment, a blockout may be required for the underdrain pipe outfall. Cooperation between Bridgeand the district as to the drainage requirements is needed to guarantee proper blockout locations.

9.3 - 4 April 1991



January 1991 9.3 - 5



Underdrain pipe and gravel backfill for drains are not necessary behind cantilever wing walls. Three-foot (3 ft.) thickness of gravel backfill for walls behind the cantilever wing walls shall be shown inthe plans.

The backfill for walls, underdrain pipe and gravel backfill for drains are not included in bridge quan-tities, the size of the underdrain pipe should not be shown on the plans. Figure 9.3.1-4 illustratesbackfill details.

J. Embankment at Bridge Ends

The minimum clearances for the embankment at the front face of abutments shall be as indicated onStandard Plan Sheet H-9. At the ends of the abutment, the fill may be contained with wing walls or inthe case of concrete structures, placed against the exterior girders. On stub abutments with the enddiaphragm cast on the superstructure, the open expansion joint must be protected from the fill.Normally, 1/8 in. butyl rubber is used to seal the opening. Figure 9.3.1-5 and Figure 9.3.1-6 showtypical details using butyl rubber. The bearings must also be protected from the fill. Figure 9.3.1-7and Figure 9.3.1-8 show typical details to protect the bearings. There are many other different ways toprotect the open expansion joints and bearings than shown in Figures 9.3.1-5 through 8. The methodused should be well detailed in the plans. The Special Provision and Estimates unit can advise as towhat types of materials would or would not require special provisions.

9.3 - 6



January 1991 9.3 - 7



9.3 - 8



January 1991 9.3 - 9



9.3 - 10 July 1994

Open Joint Details — End Diaphragm on GirderFigure 9.3.1-7



January 1991 9.3 - 11



9.3.2 Abutment Loads

A. Applicable Loads

In general, bridge abutments will be subjected to the following loads:

Dead load reaction of superstructure.

Dead load reaction of approach slab, where applicable, taken as 2 kips per foot of wall applied at thepavement seat. Live load surcharge on earth pressure shall not be included with this load.

Weight of the abutment itself.

Weight of wing walls where applicable.

Weight of backfill and toe fill usually taken as 125 pcf.

Frame shortening of post-tensioned superstructure where applicable.

Buoyancy where applicable.

Live load reaction from superstructure without impact.

Live load reaction from approach slab, where applicable, taken as 4 kips per foot of wall for HS-20loading, 3 kips per foot for H-20 and HS-15 loading and 2 kips per foot for H-15 loading applied atthe pavement seat. Live load surcharge on earth pressure shall not be included with this load.

Earth pressure is normally taken at 30 pcf equivalent fluid pressure for group loads I through VI. Forgroup load VII, an equivalent fluid pressure with a rectangular distribution and a magnitude of 1/2 γH(KAE-KA) is added to the earth pressure. Where γ is the unit weight of the backfill (normally takenas 125 pcf), H is the height of the wall, KA is the Coulomb active pressure coefficient, and KAE is theMononobe-Okabe active pressure coefficient for earthquake as described in the Guide Specificationsfor Seismic Design of Highway Bridges.

Live load surcharge on earth pressure where applicable, normally taken as a 2-foot surcharge, causesa vertical and horizontal reaction. Dead load reaction of approach slab and live load reaction fromapproach slab shall not be included with this load.

Earthquake transmitted through bearings, girder stops, or a rigidly attached superstructure.

Seismic inertia force of the substructure, taken as the horizontal acceleration coefficient (1/2

acceleration coefficient) times the weight of the abutment (including footing and soil weight). Thisforce acts horizontally in the same direction as the earth pressure, at the mass centroid of the abut-ment. This is described in the Guide Specifications for Seismic Design of Highway Bridges. Seismicinertia force is only applied for stability and sliding analysis, it is not to be applied to determine thereinforcement required in the abutment.

Longitudinal live load from superstructure.

Temperature and shrinkage.

Centrifugal force.

Wind load from superstructure.

Figure 9.3.2-1 shows the typical loads applied to an L-abutment and Figure 9.3.2-2 shows the typicalloads applied to a cantilever abutment. Figure 9.3.2-3 shows longitudinal and transverse forces fromthe superstructure with a skew.

9.3 - 12 April 1991



January 1991 9.3 - 13



9.3 - 14



January 1991 9.3 - 15



B. Usual Governing Load Combinations

The AASHTO Specifications for load combinations supplemented by Bridge Division Criteria shownin Chapter 4 of this manual apply in the design of abutments. Normally for the design of abutments,only Group I (Service Load) and Group IV and VII (Load Factor) need to be checked. For abutmentfooting design loadings, see Section 9.5. The designer should consider other groups if it appears theymight be critical.

For the typical abutment with wing walls, check the outer 10-foot portion of the abutment with wingwall and approach slab. Beyond the 10-foot section, check the abutment without applying thewingwall and approach slab (using the live load surcharge on earth pressure).

In Group I and IV, apply live load surcharge with and without the live load reaction from the super-structure. Both the vertical and horizontal component of live load surcharge on earth pressure shouldhave the appropriate live load factor applied to it.

C. Special Handling of Lateral Forces

The longitudinal forces from the superstructure is normally transferred to the abutments through thebearings. The calculated longitudinal movement shall be used to determine the shear force developedby the bearing pads at the abutments. The Modulus of Elasticity of Neoprene at 70°F (21°C) shall beused for determining the shear force. However, the force transmitted through a bearing pad shall belimited to that which causes the bearing pad to slip. Normally, the maximum load transferred througha teflon sliding bearing is 6 percent and through an elastomeric bearing pad is 20 percent of the deadload reaction of the superstructure. For Group VII (Seismic), assume no load transfer through thebearings because end diaphragm is in contact with abutment wall. The bearing force shall not beadded to seismic earth pressure forces.

The transverse forces from the superstructure is transferred to the abutment through the girder stopsor the bearings.

1. Special Abutment Loads

a. Cantilever abutment with end diaphragm cast on superstructure:

For structures without expansion joints, the earth pressure against the end diaphragm istransmitted through the superstructure.

b. Cantilever L-abutment:

The compressibility of the expansion joint shall be considered in the design of the abutmentfor earthquake, temperature, and shrinkage when these forces increase the design load.

The following cases will illustrate the handling of typical longitudinal forces:

2. Case A — Force in Direction of Span

The intermediate pier(s) of a multi-span continuous structure shall be designed to resist theentire longitudinal force of the superstructure (unless the end piers are an integral part of thesuperstructure).

The calculated movement at the abutments determined from analysis of the superstructure shallbe used to determine the shear force developed by the bearing pads. The limiting bearing padforce shall be as indicated above. For the earth pressure force, use the βE factor (see Section 4.2),associated with earth pressure tending to decrease stability (cause overturning), except for groupload VII, bE shall be taken as 1.0.

9.3 - 16 September 1992



3. Case B — Force in Direction of Backfill

The force in the bearing pad caused by longitudinal superstructure movements shall be calculatedin a manner similar to Case A. The βE factor for this case shall be the one associated with earthpressure tending to increase stability (resist overturning), except for group load VII, βE shall betaken as 1.0.

4. Case C — Temporary Construction Condition (longitudinal forces in either direction)

a. Superstructure Built Before Backfill at Abutment

In some cases the superstructure of a bridge may be built and falsework underneath releasedbefore backfill is placed at the end abutments. At this stage the structure may be subjected toearthquake, wind or other horizontal forces. The factor (see Section 4.2) associated withthese forces shall be taken as 1.1 owing to the temporary nature of the condition, except forgroup load VII where the factor shall be taken as 1.0

The force in the bearing pad shall be calculated as in Case A. In some instances, this loadingcondition may govern the design and might be severe enough to require very large footingsor excessive amounts of reinforcing steel when compared with loading combinations thatinclude earth pressure and overburden. Rather than trying to design for severe loading condi-tions, the designer should consider recommending to the district that backfill be placed be-fore construction of the superstructure. If agreed to, note this in the sequence of constructionon the plans.

b. Superstructure Built after Backfill at Abutment

If the superstructure is to be built after the backfill is placed at the abutments, the resultingtemporary loading on the abutments will cause them to act like retaining walls. Such wallsrequire additional tensile reinforcement in the top of the footing heel. The bottom of thefooting will normally require tensile reinforcement extending from the heel to the toe oncethe superstructure is completed.

c. Sequence of Falsework Removal

Another temporary construction condition to be considered is the sequence of falseworkremoval. For example, it is usually advantageous in sizing the footing to release the false-work from under the wing walls after some portion of the superstructure load is applied tothe abutment. This item, when applicable, can be covered by a note in the sequence ofconstruction on the plans.

5. Special Considerations

When the force transmitted through the bearing pads is very large, the designer should considerincreasing the bearing pad thickness, using TFE sliding bearings and/or utilizing the flexibility ofthe abutment as a means of reducing the horizontal design force. When the flexibility of theabutment is considered, it is intended that a simple approximation of the abutment deformationbe made.

January 1991 9.3 - 17



9.3 - 18



D. Load on Girder Stop Bearings

For skewed structures with earth pressure against the end diaphragm (see Figure 9.3.2-4), the need forgirder stop bearings shall be investigated. When required, these bearings are placed vertically againstthe girder stop to transfer the skew component of the earth pressure to the abutment without restrict-ing the movement of the superstructure in the direction parallel to centerline. The design procedurefor elastomeric girder stop bearing pads for Series 8, 10, and 14 Prestress Girders is shown inChapter 8, Appendix A of this manual. In some cases bearing assemblies containing sliding surfacesmay be necessary to accommodate large superstructure movements.

Girder stops are often required to transfer earthquake load from the superstructure to the abutment. Inthese cases, all components of the girder stop, including the bearing assembly, shall be designed forthe earthquake loading in addition to the earth pressure described above.

E. Loads on Girder Stops

The loads mentioned in Section 9.3.2 D above apply to girder stops and superstructure restraints.Girder stops are designed using shear friction theory. The possibility of torsion combined withhorizontal shear when the load does not pass through the centroid of the girder stop shall also beinvestigated. Some type of transverse girder stop is required for all abutments.

9.3.3 General Design Procedures

A. Design for Stability

The factors of safety against overturning and sliding shall be as specified in Section 9.3.2 A(d) of thismanual. Special requirements for individual abutments types are covered in Section 9.3.4 A through E.Also see Section 9.5, Footings.

B. Earth Pressure at Front Face

In the usual case, the earth pressure exerted by the fill in front of the abutment is neglected inthe design. The weight of the fill in front of the abutment should be included in the analysis foroverturning if it adds to overturning.

C. Design for Strength

When the primary structural action is parallel to the superstructure or normal to the abutment face, thewall shall be treated as a column subjected to combined axial load and bending moment. Compressivereinforcement need not be included in the design of cantilever walls, but the possibility of bendingmoment in the direction of the span as well as towards the backfill shall be considered. A portion ofthe vertical bars may be cut off where they are no longer needed for stress. For footing design seeSection 9.5, Footings. In addition, see the special requirements for individual abutment types underSection 9.3.4 A through E.

D. Minimum Reinforcement

1. Minimum Wall Steel

The minimum area and maximum spacing of stressed wall reinforcement stipulated in AASHTOSpecifications shall be furnished.

January 1991 9.3 - 19



2. Minimum Temperature and Shrinkage Steel in Wall

The AASHTO Specifications, Article “Shrinkage and Temperature Reinforcement,” requires aminimum temperature and shrinkage steel of 0.125 sq. in. per foot of wall. This is not sufficientto limit shrinkage cracks in thick walls. A more appropriate minimum temperature and shrinkagesteel is taken from the ACI-83, minimum area of reinforcing steel per foot of the wall, in bothdirections on each face of the wall, shall be 0.011 times the thickness of the wall (in inches),spaced at 12 inches. On abutments that are longer than 60 feet, consideration should be given tohave vertical construction joints to minimize shrinkage cracks.

3. Minimum Cross Ties in Wall

Ties, no. 4 bars with 180 degree hooks, spaced at approximately 2 feet center to center verticallyand at approximately 4 feet center to center horizontally shall be furnished throughout the abut-ment stem in all but stub abutments, see Figure 9.3.3-1.

9.3.4 Load and Reinforcement Requirements

A. Requirements for Pile Cap Abutments

Earth pressures on some pile caps are either negligible or very small (when the lateral force on eachpile is less than 6 kips), and vertical dead load and live load are the major effects. The design of thistype of abutment is like that of a crossbeam, and transverse bending as well as shear shall be investi-gated for the spans between the piles. For the analysis of the pile cap, the wheel loads should beplaced for the maximum moment on the pile cap. For the analysis of the piles, the wheel loads shouldbe placed unsymmetrically to obtain the largest pile reaction.

For narrow bridges (one-lane ramps and two-lane bridges without skew) the transverse live loadmoment on the abutment shall be taken about the center of gravity of the pile group assuming theabutment to be a rigid beam. The maximum pile reaction from transverse effect will then be P/N +Mt/S, where P is the total vertical load, N is the total number of piles, Mt is the transverse momentabout the centerline of abutment and S is the transverse pile modulus. This analysis is only valid ifthe lateral forces from earth pressure, etc. are less than 6 kips per pile and all the piles have no batter.

For wide bridges (2 lanes with skew and wider) the abutment may be assumed to act as a flexiblebeam on knife-edge supports. The maximum pile live load reaction from transverse loading can beobtained by assuming the abutment acts as a simple beam between piles and each wheel load (in thedesign lane or approach lane) is proportionally distributed to the adjacent piles (see Figure 9.3.4-1).Transverse moments and shears may be found assuming the spans between piles as semi-simplysupported: i.e. maximum positive or negative moment = 0.80 times the simple beam moment. Maxi-mum shear = simple beam shear. This analysis is valid for piles with a stiffness much less than thepile cap.

For pile caps with lateral loads greater than 6 kips, with battered piles, or for piles with a stiffnessabout the same magnitude as the pile cap, such as shafts, the analysis for the pile cap should be as acrossbeam, see Section 9.2.1, and the analysis for the piles should include the lateral capacity of thepile, see Section 9.6.

B. Requirements for Stub Abutments

For stub abutment (girder seat to top of footing less than approximately 4 feet), the footing and wallcan be considered as a continuous inverted T-beam. The analysis of this type abutment shall includeinvestigation into both bending and shear stresses parallel to centerline of bearing. If the superstruc-ture is relatively deep, earth pressure combined with longitudinal forces from the superstructure maybecome significant (see Section 9.3.4 C).

9.3 - 20



January 1991 9.3 - 21



9.3 - 22

Pile Cap AbutmentFigure 9.3.4-1



January 1991 9.3 - 23

C. Requirements for Cantilever Abutments

If the height of the wall from the bearing seat down to the bottom of the footing exceeds the cleardistance between the girder bearings, the assumed 45° lines of influence from the girder reactions willoverlap, and the dead load and live load from the superstructure can be assumed equally distributedover the abutment width. The design may then be carried out on a per foot basis as described earlierunder Section 9.3.3 A through C. The primary structural action takes place normal to the abutment,and the bending moment effect parallel to the abutment may be neglected in most cases. The wall isassumed to be a cantilever member fixed at the top of the footing and subjected to axial, shear, andbending loads.

D. Requirements for Spill-Through Abutments

The analysis of this type of abutment is similar to that of an intermediate pier. The crossbeam shall beinvestigated for vertical loading as well as earth pressure and longitudinal effects transmitted from thesuperstructure. Columns shall be investigated for vertical loads combined with horizontal forcesacting transversely and longitudinally. For earth pressure acting on rectangular columns, assume aneffective column width equal to 1.5 times the actual column width. Short, stiff columns may require ahinge at the top or bottom to relieve excessive longitudinal moments.

E. Requirements for Rigid Frame Abutments

Abutments which make up parts of rigid frame bridges shall be designed in accordance with serviceload criteria. Whenever a preliminary analysis establishes that the effects of vertical loads are fargreater than the effects of horizontal earth pressure loads (generally the case with low abutments andlong horizontal spans), load factor criteria may be used. Earth pressure loading shall be a maximumof 60 pcf equivalent fluid pressure and a minimum of 30 pcf equivalent fluid pressure to be applied inany combination except as noted below. The 60 pcf value is to be used for normal rigid frames wherethere is a high degree of restraint to the soil mass. Lower figures may be used if lower degree ofrestraints exist. The 30 pcf value is equivalent to a normal cantilever retaining wall. Earth pressureloading of up to 15 pcf may be used to reduce moments in the superstructure provided that suchpressure can be developed. This reduction may also be used for earthquake acting on rigid framestructures. Earthquake forces from the soil mass need not be applied as loads. The abutment designshould include the live load impact factor from the superstructure. However, impact shall not beincluded in the footing design. The rigid frame itself should be considered restrained against sideswayfor live load only.

For requirements for rigid frames with ceramic tile lining, see Section 8.4.6.

9-3WORK:V:BDM3


Substructure Design Retaining Walls

9.4 Retaining Walls

9.4.1 General

A retaining wall is a structure built to provide lateral support for a mass of earth or other material, the topof which is at a higher elevation than the earth or rock in front of the wall.

Retaining walls depend either on their own weight or on their own weight plus an additional weight ofthe laterally supported material, or on a tieback system for their stability.

All retaining walls not covered under Standard Walls or Preapproved Proprietary Walls are designed inthe Bridge and Structures Division. The Hydraulics Section should be consulted for any walls that couldbe threatened by flood water or are located in a flood plain. The Architectural Section should reviewarchitectural features and visual impacts at the Preliminary Design stage.

For illustrations of different types of walls, see Figures 9.4.2-1 through 9.4.2-4 at the end of this section.

9.4.2 Common Types of Walls

A. Cantilevered Walls

Cantilevered walls are reinforced concrete walls consisting of a base slab footing from which avertical stem wall extends. These walls are suitable for heights up to 35 feet. Details for constructionare given in the Standard Plans, along with design criteria. For nonstandard designs, the computerprogram RETWAL can be used for analysis. The major disadvantage of these walls is the lowtolerance to post-construction settlement, which may require use of piling to provide adequatesupport.

B. Counterfort Walls

Counterfort walls are a type of cantilever wall which have ribs on the backside to strengthen thejunction between footing and stem wall. These walls can exceed heights of 50 feet and generallybecome economical for walls having considerable portions exceeding heights of 25 feet.

C. Gravity Walls

Gravity walls can be made from many different materials including plain concrete, rubble masonry,mortar rubble masonry and gabions. Gravity walls depend on their own weight for stability. They aregenerally used for wall heights of 10 feet or less, with the exception of gabion walls, which canexceed 30 feet in height.

1. Mortar Rubble Masonry Walls

Basic design and construction standards for these walls are given in the Standard Plans. Use ofmasonry walls are quite limited due to the excessive cost of placing the material by hand. Theyare primarily used when it is necessary to blend with previously completed projects where amasonry wall already exists.

2. Gabion Walls

Gabion walls consist of wire baskets laced together and filled with rock. These walls are flexibleand some post-construction settlement can be tolerated. Details for gabion wall construction arefound in the Standard Plans and Specifications.

D. Cribbing

Cribbing is made of metal bins, precast reinforced concrete or logs. Cribbing height is generally 10 to30 feet.

January 1991 9.4 - 1



1. Metal Cribbing

There are two types of metal cribbing approved for use in the state of Washington. The detailsare shown in the Standard Plans.

2. Reinforced Concrete Cribbing

Concrete cribbing is similar to metal and can be used as an alternate. It is recommended to usethis type in marine areas for its ability to withstand corrosion.

3. Log Cribbing

Log cribbing has a rustic aesthetic value which makes it popular for use in locations having anatural environment, such as parks, national forests, or primitive areas. It is well suited for use ondetours or temporary walls used for stage construction.

E. Cylinder Pile Walls

This wall utilizes a large diameter, 4 to 10 feet, drilled shaft filled with Class 4000 concrete. Theshaft is reinforced with steel beams or steel reinforcing bars. Wall heights, up to 50 feet, have beenbuilt to retain fills. Wall panels made of cast-in-place concrete, precast concrete or timber areconnected to cylinder piles.

F. Tieback Walls

Tieback walls use vertical main load carrying members, such as soldier piles, cylinder piles, sheetpiles, or slurry walls, to resist horizontal forces. The main members are connected to high strengthsteel bars or strand anchors, which are fixed into soil or rock with high strength grout and stressed tocounteract the horizontal earth pressure loads. These walls can be built to heights exceeding 50 feet.The anchors can be incorporated into a permanent wall by the use of a double corrosion protectionsystem or can be used in a temporary condition for shoring and cribbing. The greatest advantage inusing tiebacks is that it causes minimal disturbance to the soil behind the wall and any structuresresting on this soil. Nonstressed anchors, called deadman anchors, rely on passive pressure of the soilin front of the deadman panel to resist horizontal forces.

G. Proprietary Walls

A wall specified to be supplied from a single source (patented, trademark, or copyright) is a propri-etary wall. These walls can range in heights from 15 to 50 feet. The following is a description of themost common types of proprietary walls:

1. Structural Earth Walls

A structural earth wall is a flexible system consisting of concrete face panels that are held rigidlyinto place with thin galvanized steel or aluminum strips extending into a select backfill mass.These walls will allow for some settlement and are best used for fill sections. The walls havethree principal elements:

• The backfill or wall mass: a grandular soil with good internal friction (gravel borrow).

• The reinforcing metal strips, steel mesh, welded wire, or geotextiles.

• The facing: precast concrete panels, welded wire with vegetation, geotextiles, or shotcrete.

9.4 - 2



There are several important factors when selecting a structural earth wall. These are as follows:

a. Height

In fills more than 10 feet high, structural earth walls are generally less costly than other walltypes in fill locations.

b. Length

Adequate room is needed for earthwork equipment. Short, low walls should be avoided.

c. Backfill

A granular soil meeting the requirements of gravel borrow is required for the wall mass. Inareas where the wall may become saturated, the backfill shall be free-draining. The MaterialsLab will supply the Special Provisions for the wall mass material.

d. Excavation

Structural earth walls are typically more costly than other wall types in excavation areas.Greater excavation is needed to accommodate the wall mass which has a width of about70 percent of the wall height.

e. Foundation

These walls perform well in settlement sensitive areas, but are not adaptable to pile support.

f. Aesthetics

Facing is available in a variety of surface textures, shapes and colors. Welded wire wallsurfaces may have vegetation growing on exposed surfaces to match existing terrain. Thebackfill used in this case must be suitable to sustain vegetation growth at the face of thewall.

2. Geotextile Walls

Geotextile walls are structural earth walls that use geotextile fabric for the reinforcement and thefacing. The main use of fabric walls is for temporary walls, which can become permanent wallswith a cast-in-place or shotcrete facing. The Materials Lab is responsible for the design andreview of geotextile walls.

3. Other Proprietary Walls

Other wall systems similar in concept to the standard crib, bin, precast cantilever, or tieback canoffer cost reductions, reduce construction time, and provide special aesthetic features.

A list of preapproved proprietary walls is on file in our office, including height limitations. Thedistrict can select a particular wall type from the list and include it in the contract plans, as analternate to a Standard Wall. The Materials Lab and the Preliminary Plans Unit will approve theconcept prior to Ad. The Special Provisions will be written by the Bridge Office with designcriteria, and the Materials Lab will give the soil criteria needed for design and check the soil foroverall stability. Prior to wall construction, the supplier will submit design calculations and shopdrawings for approval. The following is a list of the proprietary wall systems that arepreapproved:

a. Criblock Retaining Walls Northwest Inc. — “Criblock” up to 30 feet.

January 1991 9.4 - 3



b. Hilfiker Retaining Walls, a cast-in-place concrete face is not allowed with these wallsystems.

(1) “Reinforced Soil Wall” — up to 30 feet.(2) “Welded Wire Wall” — up to 20 feet.

c. The Reinforced Earth Co. — “Reinforced Earth” — up to 30 feet.

d. VSL Corporation — “Reinforced Earth” — up to 30 feet.

H. Slurry Walls

Slurry wall construction method enables wall placement to precede wall excavation. This is usefulwhen restricted by tight right-of-way, staging construction, or where ground water is a problem. Atrench is excavated for the wall and simultaneously filled with a bentonite slurry. The bentonite slurryrestricts the ground water flow and holds the trench sides in place. Reinforcing steel is placed in theslurry-filled trench and concrete is placed by means of a tremie or a concrete pump while displacingthe slurry. After the concrete has cured, the excavation can be completed. With the addition oftiebacks, these walls can exceed heights of 50 feet. For an aesthetically pleasing appearance, facing isused in the form of precast panels, cast-in-place concrete, or shotcrete.

I. Rock Walls

Rock walls are gravity walls made of stacked large rock. They are used primarily in cut sections toprovide erosion protection and limited support. They are generally 15 feet or less in height.

J. Soil Nailing

Soil nailing is a technique used to stabilize moving earth, such as a landslide, or as a means oftemporary shoring. Soil anchors are used along with the strength of the soil to provide stability. TheMaterials Lab will design the system of soil nailing to be incorporated in the bridge contract plans.

K. Wingwall

A wingwall retains the fill beyond the bridge end. It acts like a horizontal cantilevered wall with itsmain support from the end abutment. The two Office Standards lengths are 15 feet with 1 3/4:1 and2:1 fill slope and 20 feet with 2:1 fill slope wingwalls. The standards also show different surfacetreatments, e.g., fractured fin finish or plain concrete finish. A separate design is required when usinga nonstandard length. See Design Example 9.4 B1-10 for curtain wall rigidly attached to footing andabutment wall.

L. Noise Walls

Noise walls are primarily used in urban or residential areas to mitigate noise or to obstruct view ofroadway. Precast wall panels supported by precast pilasters, cast-in-place wall and footing, or woodfencing are the common types. The Architectural Section is responsible for determining wall type.Design criteria for noise walls is based on AASHTO’s Guide Specifications for Structural Design ofSound Barriers.

9.4.3 Design

A. General

Refer to AASHTO Specifications and Bridge Design Manual Criteria 9.1.2, 9.3.1F and G, and9.5.1A2. Service Load Design is used for design of retaining walls and the loading combinations shallbe as described in AASHTO. Service Load Design is used rather than Load Factor Design, because ofits long history of good performance and due to the lack of development of Load Factor Designcriteria for retaining walls.

9.4 - 4 April 1991



January 1991 9.4 - 5



9.4 - 6



January 1991 9.4 - 7



9.4 - 8



B. Cantilever Walls

In general, concrete for retaining walls shall be Class 3000 Concrete with a 28-day compressivestrength of 3,000 psi. For special retaining wall design, the use of Class 4000 is appropriate.

Earth pressures shall be based on soil weight = 120 lb./cu. ft., the surcharge slope, the coefficient ofinternal friction and/or the cohesion of the backfill material. Normally the earth pressure is taken as30 lb./cu. ft. equivalent fluid pressure when well draining granular backfill material is used. Specialconsideration should be given to the design of the “U” shape abutment without expansion jointsbetween the abutment and retaining walls. At the junction of the abutment and retaining wall anequivalent fluid pressure of 45 lb./cu. ft. shall be used. This increased loading can normally bereduced to 30 lb./cu. ft. at a distance from the junction of the abutment and retaining wall equal to theaverage height of the wall under design.

The resultant for Group I loadings (except for walls with traffic barriers having a height (H) of16 feet or less, see table below) shall be kept within the middle one-third of footing. This can beexpressed as a minimum Factor of Safety (FS) of two against overturning about the toe of the footingfor spread footings or the front row of piles for pile footings (see 9.5.1 for additional criteria regard-ing pile footings). For all other loading combinations, the resultant shall be kept within the middleone-half of the footing. To maintain adequate safety against sliding, the following should be observedfor spread footings.

(FS)P (P = total horizontal force on wall) W (W= total minimum vertical load)

For walls having a height (H) of 16 feet or less, the controlling load is the 10 kip collision load. Thisload occurs occasionally and will have a reduced factor of safety.

Wall Height, H Overturning* Sliding

Roadway Grade to M abt. toe resist Location FS(EP + Sur or 10k) < 0.5Bottom of Footing M abt. toe loads of Resultant* Weight

H, 16 feet greater than within F.S. = 1.2or less 1.5 middle

for 10K collision load 1/2 of footing

H, 17 feet greater than within F.S. = 1.5or more 2.0 middle

for all Wall load cases 1/3 of footing

Earthquake greater than within FS(EP + EQ) < 0.5Group VII 1.5 middle WeightAll Heights 1/2 of footing FS = 1.1

Factor of Safety (FS) Table*Both cases shall be met for determining wall stability.

The 10 kip collision load shall be distributed over 16 feet. This is the minimum wall length allowedfor Type 2 Retaining Walls in the Standard Plans. In a special design, the distribution width shall bethe smaller of wall length between expansion joints (24′-0″ max.) or 5 feet + 2H (assumes AASHTOtraffic barrier distribution plus a 45 degree influence line).

October 1993 9.4 - 9

≤ 0.5



For sliding, the passive resistance in the front of the footing may be considered if the earth is morethan 2 feet deep on the top of the footing and does not slope downward away from the wall. Thedesign soil pressure at the toe of the footing shall not exceed the allowable soil bearing capacitysupplied by the Foundation Engineer.

For retaining walls resting on foundation piles, refer to Bridge Design Manual Sections 9.5.1, 9.5.2,and 9.6.

Mononobe-Okabe analysis in AASHTO Guide Specifications for Seismic Design of Highway Bridgesshall be used as a check in the design of the wall. AASHTO article “Abutments” gives equations tocalculate the earthquake forces. Reduced factors of safety are shown in the preceding table. TheMononobe-Okabe equation requires the following assumptions:

• Kv = 0, vertical acceleration coefficient is zero.

• Kh = A/2, A is the acceleration coefficient.

• δ, angle of friction between soil and abutmenti, backfill slope angle

• δ = i, slip is more likely to occur within the backfill than between soil and abutment interface.The earthquake force will be in the same direction as the slope of the surface of the backfill.

• β = 0, For cantilever walls, the soil fails in a vertical plane through the footing heel. This resultsin β = 0 for cantilever walls, regardless of wall batter.

See example in Design Aid 9.4-A1 to determine earthquake load.

C. Diaphragm Walls (Other names: Slurry Wall, Cut-off Wall, or Curtain Wall)

The permanent diaphragm walls include cylinder or tangent pile walls, simple panel slurry walls, andT-section slurry walls.

1. Advantages of diaphragm walls are:

a. No formwork required;

b. No lowering of the ground water table required;

c. Can form outer wall of structures;

d. Irregular shapes are possible;

e. Relatively impervious in comparison with other types of walls, if dry excavation isnecessary;

f. Construction possible under adverse circumstances, such as unfavorable soils and hydrologicconditions and where other techniques may have limitations;

g. Can be constructed to considerable depths ahead of the main excavation;

h. Relatively free from vibrations and noise during construction.

2. Disadvantages of diaphragm walls are:

a. Limited local contractor experience which may result in higher bid prices or unforeseenconstruction problems;

b. The disposal of used slurries in urban areas may pose special problems.

c. Higher cost.

9.4 - 10 October 1993



3. Design Criteria

a. Class 4000 concrete is typically used. Higher strength concrete may be specified for specialcases with approval of the Bridge Design Engineer.

b. To compensate for the effects of the concrete being cast in a slurry, the assumed concretecompressive strength shall be fc = 0.85fc′. Modulus of elasticity shall be calculated from thereduced concrete strength.

c. Use 80 percent of the allowable bond stress (i.e., increase development length by 25 percent)for deformed bars due to the thin, slippery film coating on the reinforcing steel from theslurry.

d. Lap splices shall be 1.5 times normally specified splice length.

e. To allow for proper placement of concrete, use the following minimum spacing:

• Vertical bars at 6 inch spacing, preferably 9 inch spacing.

• Horizontal bars at 12 inch spacing.

f. Concrete cover shall be a minimum of 3 inches;

g. The wall panel shall be a maximum of 48 inches thick for both simple and T-sectiondiaphragm walls. The maximum panel width is limited to 8 feet for T-section and 24 feet forsimple diaphragm wall. Use the same thickness for the flange and the stem of a T-section ifpossible.

h. There are tree common types of analysis:

(1) Factored soil strength parameters of Cm, φm, and δm with full passive coefficient KP(so-called Duncan’s method):

φm = tan-1 (tanφ) F

Cm =

δm = φm

By reducing soil strength parameters, the length of embedment required for wallstability is used in design.

An approximate correlation between depth factor and factor of safety applied to shearstrength is shown as follows:

Depth CorrespondingSoils Factor* Value of F

Good 1.2 1.15 ~ 1.17Typical 1.3 1.25Bad 1.4 1.29 ~ 1.36

*Conventional practice is to use a factor of safety which increases the embedded depthby 20 to 40 percent above the value required for barely stable equilibrium. The choiceof depth factor is based on engineering judgment.

October 1993 9.4 - 11

23

CF



(2) Unfactored soil parameters use KP/1.5, without adding additional length.

(3) Unfactored soil parameters use KP, when providing 20 ~ 40 percent additional length.

i. Soil loading due to earthquake is based on Mononobe-Okabe pseudo-static analysis (refer toGuide Specification, Commentary “Foundation and Abutment Design Requirements, Free-Standing Abutments”)

KAE = KA + KAE

where

KAE = the coefficient of total earthquake earth pressure

KAE = KA (Coulomb’s static active coefficient), when θ = 0°

∆KAE = the additional dynamic load

The static loads are triangularly distributed and the additional dynamic loads are uniformlydistributed on the wall.

It is recommended that the horizontal acceleration coefficient Kh for diaphragm walls be thevalue of 1.0A, which falls in between the value of 0.5A for yielding walls and 1.5A fornonyielding walls. (A = acceleration coefficient)

The design seismic passive resistances represent the total resistance during earthquake. Thecoefficient of passive resistance can be determined from the Guide Specifications for Seis-mic Design of Highway Bridges.

Note that if, θ = 0°, then KPE = KP (Coulomb’s static passive coefficient)

For the submerged portion of soils, KAE and KPE shall be calculated by replacing γ with γ′.

= tan-1

where

γ ′ = submerged unit weight of soil

Kv = vertical acceleration coefficient

j. Two different techniques can be used for design of diaphragm walls:

(1) Fixed Earth Support Method — So-called “Conventional Method” (refer to USS SteelSheet Piling Design Manual).

(2) Free Earth Support Method — So-called “Simplified Method.” This method usesactive earth pressure on the projecting portions of the wall, and passive pressures on thefront of the wall for the entire embedded length. The required depth of embedment isdetermined based on:

(a) Moment equilibrium about the base of the wall;

(b) Overall wall and slope stability using unfactored (or peak) soil strength parametersand factor of safety ≥ 1.5; and

(c) A minimum wall depth below the excavation level depending on engineeringjudgment or criteria from the Materials Laboratory.

9.4 - 12 October 1993

( Kh . γ ) 1-Kv γ ′



Due to its simplicity and accuracy, the “Free Earth Support Method” isrecommended to design diaphragm walls. A computer program name “Wall” isavailable.

k. The maximum deflection at the top of the wall at service load levels shall be limited toH/120 or 4 inches, whichever is less, and to about 2 inches at the base, and to about11/2 inches at the potential deteriorated plane (or slip plane). The calculation of deflection isbased on a value of n = 16 for determining modulus of elasticity of concrete used.

l. The wall is designed based on “Ultimate Strength Design Method” (or Load Factored DesignMethod”). The following procedures should be used.

(1) The minimum reinforcement provided shall be adequate to fulfill the requirements ofAASHTO Article “Minimum Reinforcement.”

(2) Find the amount of reinforcement (on a trial basis).

(3) Check flexural cracking (see AASHTO Article “Distribution of Flexural Reinforce-ment”).

(4) Calculate moment and shear capacity and check if they are larger than the appliedmoment and shear based on AASHTO table “Table of Coefficients γ and β.”

(5) When using the equivalent (or pseudo)-static earthquake loadings and ultimate strengthdesign methods, the section capacity, U, should be:

U ≥ 1.3 (DL + βE · EP + W)

or

U ≥ 1.0 [DL + βE (EQ + W)]

where

DL = dead load of the structural element;

EP = static earth pressure acting on the element (plus surcharge);

EQ = earthquake earth pressure acting on the element;

W = hydrostatic water pressure

βE = 1.0 when using Duncan’s Method1.3 when using Conventional Method with full KP

m. For diaphragm wall with tiebacks:

(1) Recommended embedment is a minimum of at least 10 feet below the proposedexcavation level. Actual embedment may be increased to provide adequate kick-outresistance through development of passive pressure or for vertical load capacity.

(2) Due to soil-structure interaction, a redistribution of lateral stresses is anticipated,resulting in reduction of pressure near the center of spans between anchors, and aconcentration of pressure at supports. The design of the wall with regard to momentcapacity, estimate the actual moment in the walls as follows:

Mactual = R · Mcalculated

The value of R for clay approaches unity as the compressibility of the soil increases.The value of R for loose sand is larger than that for dense sand. The typical value of

October 1993 9.4 - 13



R for sand is recommended to be 0.8. Also, the values of R for stiff walls are larger thanfor flexible walls.

D. Tieback Walls

1. Principles of Anchor Design

Anchor design includes:

• Evaluation of the feasibility of anchors,

• Selection of an anchor system,

• Estimation of anchor capacity,

• Determination of unbonded length, bonded length, and

• Selection of corrosion protection.

The engineer should determine whether anchors can be economically used at a particular sitebased on the ability to install the anchors and to develop capacity. The presence ofutilities or other underground facilities may govern whether anchors can be installed.

The tendon may consist of bars, wires, or strands. The choice of appropriate type is usually leftto the contractor but may be specified by the designer if special site conditions exist whichpreclude the use of certain tendon types. In general, strands and wires have advantages withrespect to tensile strength, limited work areas, ease of transportation, and storage. Bars are moreeasily protected against corrosion, easier to stress and transfer load.

A reliable estimate of the safe anchor capacity is required from the soil’s report recommendationsfor each project to determine the feasibility of anchoring. The capacity of each anchor shall beverified by testing. Testing shall be part of anchor installation and included in the specifications.Based on previous experience, a range of typical design values is listed as follows:

a. Design loads between 30 and 120 tons.

b. The anchor wall system must be analyzed to ensure long-term stability. The minimumunbonded length must be specified in the contract document, and is usually 15 feet for soiland rock anchors (longer free lengths may be required in plastic soils, consult the Geotech-nical Engineer) in order to avoid unacceptable prestress losses due to creep in the steel, soil,or rock.

c. Angle of inclination between 10 degrees and 45 degrees. A 15 degree angle is preferred tosimplify grouting and minimize vertical forces imposed on the wall by the anchors. Steeperangles, up to 45 degrees, are only recommended to reach deep bearing strata or avoidexisting substructures.

9.4 - 14 October 1993



The estimated ultimate load transferred from the bond length to different types of soils is listed asfollows:

Corrected Standard EstimatedPenetration No. Ultimate Transfer

Soil Type N Load in Kip/ft

Sand & Gravel Loose (4-10) 10Medium Compact (10-30) 15Compact (30-50) 20

Sand Loose (4-10) 7Medium Compact (10-30) 10Compact (30-50) 13

Sand & Silt Loose (4-10) 5Medium Compact (10-30) 7Compact (30-50) 9

Silt-clay mixture Stiff (10-20) 2with minimum LL, PI, Hard (20-40) 4and LI restrictions,or fine micaceoussand or silt mixtures

The maximum allowable anchor design load in soil may be determined by multiplying the bondlength by the ultimate transfer load and dividing by a safety factor of 2.5.

The ultimate load transferred from the bond length to rock deposits may be estimated from therock type in the following table.

EstimatedUltimate Transfer Load

Rock Type in Kip/ft

Granite or Basalt 50Dolomitic Limestone 40Soft Limestone 30Sandstone 30Slates and Hard Shales 25Soft Shales 10

The maximum allowable anchor design load in rock may be determined by multiplying the bondlength by the ultimate transfer load and dividing by a safety factor of 3.

January 1991 9.4 - 15



2. Coefficient of Earth Pressure

Practically, the design should be first considered using active pressure coefficients (KA) unlessstructures exist within a lateral distance equal to twice the wall height. For this case, an averageearth pressure coefficient (K) should be computed as follows:

xK = Ko - 2H (Ko - KA) (1)

wherex = distance from structure wallH = height of wallKo = coefficient of at-rest earth pressure

Note: KA allows lower wall design pressure (if small wall displacements) can be tolerated, i.e.,ground subsidence occurs.

Ko increases wall design pressure but limits wall displacement, i.e., ground subsidence islimited.

9.4 - 16



January 1991 9.4 - 17



Typical amount of wall translation (top movement) to develop the active earth pressure.

Amount ofSoil and Condition Translation

Cohesionless (0.1% to 0.2%)HDense

Cohesionless (0.2% to 0.5%)HLoose

Cohesive (1% to 2%)HFirm

Cohesive (2% to 5%)HSoft

3. Corrosion Protection

The corrosion protection of anchors can be divided into two categories*:

a. Simple Protection The use of simple protection relies on Portland cement grout to protectthe tendon, bar, or strand in the bond zone. The unbonded lengths are sheaths filled withanti-corrosion grease, heat shrink sleeves, and secondary grouting after stressing. Except forsecondary grouting, the protection is usually in place prior to inserting the tendon in thehole.

b. Double Protection Complete encapsulation of the anchor tendon is accomplished by a corru-gated PVC, high-density polyethlene, or steel tube. The same provisions of protecting theunbonded length for simple protection are applied to those for double protection.

*Provide simple protection for temporary tieback walls (less than 18 months) and double protec-tion for permanent tieback walls.

4. Angle of Wall Friction

The wall friction depends on the soil properties, the amount and direction of wall movement, thewall material, and the surface condition. Values of δ = 0 or δ = φ are generally too low andhigh, respectively, for most practical cases. The typical values are between 1 φ/3 and 2 φ/3. It isconservative if assumed δ = 0.

5. Determination of Tieback Spacing

The preliminary anchor spacing can be determined from Figure 9.4.3-1.

Suggested temporary test loads are between 75 and 80 percent of Guaranteed Ultimate TensileStrength (GUTS). Suggested Limits for design loads, T, are between 0.5 and 0.6 of GUTS(typically 53 percent).

Therefore,

Typical pile spacings (horizontal) of 6 to 10 feet and anchor spacings (vertical) of 8 to 12 feet arecommonly used. The minimum spacing of 4 feet in both directions is not recommended forconsidering the effectiveness and disturbance of anchors due to installation.

9.4 - 18

(S1 + S1)S2 = T cos q2 PE



January 1991 9.4 - 19



6. Design of Soldier Pile Tieback Walls

a. Lateral Earth Pressures

Case 1 Cantilever Soldier Piles and Piles with Single Level Tieback

9.4 - 20 July 1996

Figure 9.4.3-2

For the submerged portion of soil, KAE and KPE should be calculated by replacing θ with θ′in Equations (4) and (5) and replacing γ with γ′ for calculating earth pressure.



Note:

(1) Neglect any passive resistance below the base of excavation in D zone where D is thelargest value of 1.5 times shaft diameter, 0.1 times height of the wall, depth of fasciawall footing, or anticipated future excavation depth within 20 feet of wall.

(2) Active pressure is assumed to act over pile spacing above base of excavation and overshaft diameter below base of excavation. Passive pressure is assumed to act over twotimes over shaft diameter or pile spacing, whichever is smaller.

(3) For permanent tiebacks, tie back DESIGN LOAD, T, Shall be (1) + (2) or [(1) +(3)]/1.5, whichever is greater. For temporary tiebacks, tie back DESIGN LOAD, T, shallbe (1) + (2).

(4) Lock-off load is 80 percent of (1) + (2) for permanent wall and 70 percent of (1) + (2)for temporary wall.

(5) Proof test to 1.5T for permanent tiebacks and to 1.3T for temporary tiebacks.

July 1996 9.4 - 21



Case 2 Multiple Level Tieback

9.4 - 22 July 1996

Figure 9.4.3-3



b. Depth of Embedment

For cantilever piles without tieback, the embedment should be determined to satisfy horizon-tal force equilibrium and moment equilibrium about the bottom of the pile.

For piles with tiebacks, the depth of embedment is determined by moment equilibrium oflateral force about kpoint 0.

Neglect the moment resistance of soldier pile member at 0.

Depth of embedment, D, must also be sufficient to provide necessary vertical capacity oradequate kick-out resistance through development of passive pressure.

c. Design of Timber Lagging

Most commonly, the lagging thickness is determined from past construction experience asrelated to depth of excavation, soil condition, and soldier pile spacing. In other cases, soilpressure distribution recommended by geotechnical engineer is used to determine the thick-ness of lagging.

The soil pressure distribution equal to 50 percent of the lateral earth pressure diagram isrecommended to design lagging which is simply supported. The 50 percent reduction is dueto the soil arching effect behind the wall. However, this procedure leads to unreasonablythick lagging for deep excavations with relatively larger soldier pile spacings.

d. Design of Fascia Wall

Fascia wall shall be reinforced concrete and shall be designed according to the latestAASHTO Standard and Interim Specifications for Highway Bridges.* The minimum struc-tural thickness of fascia wall shall be 9 inches. Architectural treatment of facing shall beindicated on the drawing.

Concrete strength shall not be less than 3,000 psi at 28 days. The wall is to extend 2 feetminimum below the ground line adjacent to the wall.

Permanent drainage systems shall be provided to prevent hydrostatic pressures developingbehind the wall. A cut which slopes toward the proposed wall will invariably encounternatural subsurface drainage.

Vertical chimney drains, prefabricated drains, or porous engineering fabrics can be used fornormal situations to collect and transport drainage to a weep hole or pipe located at the baseof the wall. Concentrated areas of subsurface drainage may be controlled by installing hori-zontal drains to intercept the flow at a distance well behind the wall.

*Note:

(1) Most possibilities of load cases governing are:Group I = 1.3(DL + 1.67LL + 1.3E)Group VII = 1.0(D + E + EQ)

(2) 50 percent of worse load is used for design.

(3) Check for 10 kips impact load.

January 1991 9.4 - 23



e. Design of Soldier Piles

The soldier piles shall be designed for shear, bending, and axial stresses, and according tothe latest AASHTO design criteria. Soldier piles may be steel or concrete with a minimumyield strength of steel being 36 ksi or the minimum strength of concrete shall be 4,000 psi at28 days (concrete Class 4000).

Due to soil-structure interaction, a redistribution of lateral stresses is anticipated, resulting ina reduction of pressure near the center of spans between anchors and a concentration ofpressure at supports. The actual bending moment is recommended to be 80 percent of themaximum bending moment calculated based on the free-earth method.

f. Check for Stage Construction

The earth pressure distribution for an anchored wall changes during wall installation. Theprocedures for checking the stability of the wall system for temporary construction loadings aredescribed as follows:

(1) Draw “pressure diagrams” at various construction stages, each including all pertinentloads, i.e., surcharge, water, soil, etc.

(a) A triangular diagram for estimating cantilever excavation to first anchor or for wallswith only one anchor row.

(b) A trapezoidal diagram for temporary excavation below first anchor level.

(c) A trapezoidal diagram for final depth excavation.

(2) Find preliminary anchor spacing.

(a) First anchor row Determine the safe cantilever or unsupported excavation height.Assume the first anchor row is located 3 feet above this level. This distance isrequired for anchor installation. Find lateral spacing by dividing anchor allowablecapacity by area of pressure diagram in step 1c.

(b) Subsequent excavation levels must consider increased loads on previous anchorrows. Necessary embedment of soldier piles must be considered at all stages ofexcavation. Diameter of shaft may be increased to reduce penetration.

(3) Estimate required section modulus of soldier piles at all stages of excavation to ensurestructural integrity. Adjust anchor spacing to optimize structural design.

(4) Estimate the permanent vertical loads due to anchor inclination and wall dead weightand check:

(a) vertical member structural capacity,

(b) bearing capacity of the soil/rock, and

(c) settlement.

(5) Check overall stability of final design.

9.4 - 24



(6) Construction checks during design:

(a) Size anchor tendon structurally to resist maximum prescribed test load at less than80 percent of ultimate strength.

(b) Determine the maximum transfer load for the upper anchor row based on allowablepassive resistance (KP/1.5) at that initial wall height.

g. Design of Bond Length

The bond length should not be specified in the contract plan.

For design purposes, the required bond length can be approximated with sufficient accuracyas discussed in other parts of this section to permit cost estimates and right of way acquisi-tions to be made confidently.

The bond transfer values for soil grout length (or bond length) should be verified by testingto determine the required bond length.

Some important points are listed as follows:

(1) A minimum bond length should be specified in the contract documents. The recom-mended values are 10 feet in rock and 15 feet in soils.

(2) The bond lengths exceeding 40 feet in soils or 254 feet in rock do not efficiently increasethe anchor capacity.

(3) At sites with restricted right of way, the maximum bond length is the distance from theend of unbonded length to within 2 feet of the right of way.

(4) To permit high pressure grouting without damage to existing facilities and to ensureadequate overburden pressure to mobilize the full friction between soil and grout, a15-foot minimum overburden cover over the bond zone is recommended for anchors ofaverage capacity (i.e., 150 kips or less).

(5) Anchors founded in mixed ground condition should be designed assuming the entireembedment is the weakest deposit.

(6) The bar or strand grout length (or bar bond length) is 15 feet.

July 1996 9.4 - 25



h. Recommended Tieback Wall Configuration

(1) Base of excavation larger than 10 feet above soft soil layer.

9.4 - 26

Figure 9.4.3-4a



(2) Base of excavation in or smaller than 10 feet above soft soil layer.

January 1991 9.4 - 27

Figure 9.4.3-4b

Note: Stability number n and m are determined based on stability analysis of the projectwalls. Consult with Material Laboratory to obtain appropriate values of n and m.



(3) Typical section of solider pile tieback wall.

9.4 - 28 January 1991

Figures 9.4.3-5



January 1991 9.4 - 29

9.4.4 Miscellaneous Items

A. Drainage

All concrete retaining walls shall have 3-inch diameter weepholes located 6 inches above final groundline and spaced about 12 feet apart. In case the vertical distance between the top of the footing andfinal ground line is greater than 10 feet, additional weepholes shall be provided 6 inches above thetop of the footing. No weepholes are necessary in cantilever wingwalls. Drainage features shall bedetailed on plans.

Weepholes can get clogged up or freeze up, and the water pressure behind the wall may start to buildup. In order to keep the water pressure from building up, it is important to have well draining gravelbackfill and underdrains. Appropriate details must be shown on the plans.

No under drain pipe or gravel backfill for drains is necessary behind cantilever wingwalls. A 3-footthickness of gravel backfill shall be shown on the plan behind the cantilever wingwalls. Backfillmaterial shall not be a part of bridge quantities. If it is necessary to excavate existing material for thebackfill, then this excavation shall be a part of Structural Excavation Class A of bridge quantities.

B. Joints

For cantilevered and gravity walls, joint spacing should be a maximum of 24 feet on centers. Forcounterfort walls, joint spacing should be a maximum of 32 feet on centers. For tieback wall, jointspacing should be 24-32 feet on centers for cast-in-place walls, but for precast units, the length of theunit would depend on the height and weight of the unit. Odd panels for all types of walls shallnormally be made up at the ends of the walls. Every joint in the wall shall provide for expansion. Forcast-in-place construction, a minimum of 1/2 inch premolded filler should be specified. A compress-ible back-up strip of closed-cell foam polyethylene or butyl rubber with a sealant on the front face isused for precast concrete walls. No joints other than construction joints shall be used in footingsexcept at bridge abutments and where the change from a pile footing to a spread footing occurs. Inthese cases, the footing shall be interrupted by a 1/2 inch premolded expansion joint through both thefooting and the wall. The maximum spacing of construction joints in the footing shall be 120 feet.The footing construction joints should have a minimum 6-inch offset with the expansion joints in thewall.

C. Architectural Treatment

The type of face treatment for retaining walls is decided on a job-to-job basis according to degree ofvisual impact. It should be discussed with the Bridge Architect at the time of preliminary plan prepa-ration. The wall should blend in with its surroundings and complement other structures in the vicinity.Top of walls are usually smooth flowing curves as seen in elevation. See Retaining Wall StandardSheets for top of wall and ground line relationship and also for cambering of front of cantileveredretaining walls.



D. Concrete Fill for Soldier Pile Walls

1. Soldier Pile Walls With No Tieback Anchors

For this type of soldier pile wall, use lean concrete for the entire soldier pile embedment length.For a wet hole, use a special designed lean concrete. Typically, the contractor designs and sub-mits this special design lean concrete for approval.

2. Soldier Pile Walls With Tieback Anchors

For this type of soldier pile wall, use lean concrete for the portion of the soldier pile above finalgrade (above the cut line in front of the soldier pile wall). Below final grade, where transfer of loadfor the vertical component of the sloping tieback(s) is resisted, use concrete Class 4000P. ConcreteClass 4000P is permissible in a wet hole (placed by tremie).

E. Detailing of Standard Reinforced Concrete Retaining Walls

1. In general, the “H” dimension shown on retaining wall plans should be in foot increments. Usethe actual design “H” reduced to the next lower even foot for dimensions up to 3 inches higherthan the even foot.

Examples: Actual height ≤ 15′-3″, show “H” = 15 on design plansActual height > 15′-3″, show “H” = 16 on design plans

For walls which are not of a uniform height, “H” should be shown for each segment of the wallbetween expansion joints or at some other convenient location. On walls with a steep slope orvertical curves, it may be desirable to show 2 or 3 different “H” dimensions within a particularsegment. The horizontal distance should be shown between changes in the “H” dimensions.

The value for “H” shall be shown in a block in the center of the panel or segment. See Example,Figure 9.4.4-1.

2. Follow the example format shown in Figure 9.4.4-1.

3. Calculate approximate quantities using the Standard Plans.

4. Wall dimensions shall be determined by the designer using the Standard Plans.

5. Do not show any details given in the Standard Plans.

6. Note on the plans any deviation from the Standard Plans.

7. Do not detail reinforcing steel, unless it deviates from the Standard Plans.

8. For pile footings, use the example format except revise the footing size, detail any additionalsteel, and show pile locations.

9-4:V:BDM9

9.4 - 30 May 1995



January 1991 9.4 - 31


Substructure Design Footings

9.5 Footings


A. General

The provisions given in this section pertain to both spread footings and pile supported footings exceptas noted in 9.5.2, Pile Supported Footings.

1. Footing Shape and Location

Footings shall normally be rectangular in plan for both square and skewed bridges. Footing depthwill normally be set at the minimum required to assure adequate bearing pressure and cover. Onstream crossings, additional cover depth may be required as protection against scour. TheHydraulic Section should be consulted on this matter. Unnecessary footing depth results in largeincreases in cost. The end slope on the bridge approach fill is usually set at the preliminary planstage but affects the depth of footings placed in the fill. Figure 9.5.1-1 illustrates some items toconsider when developing footing positions.

2. Retaining Wall Footings

Retaining wall footings shall be designed using working stress methods for reasons stated inSubsection 9.4. The resultant of forces shall be kept within the middle one-third of the footing forGroup I loadings and within the middle one-half of the footing for all other service load condi-tions, including impact collision load for walls under 16 feet. See AASHTO Working StrengthLoading Combinations.

3. Design Loadings for Spread or Pile Footings

Footings will normally be designed by load factor methods. The factored loads shall be inaccordance with Section 4, as modified below. Where the footing is being used to support a longcolumn, the magnified moments shall be used for footing design. See Section 9.2.1E for guidanceon computing magnified moments. See Figures 9.5.1-2 and 9.5.1-3 for modes of failure forspread and pile footings.

Allowable soil bearing capacities and pile loads are given in terms of service loads as they areobtained from the Foundation Engineer or, in the case of piles, specified on the plans. Whenfactored loads are applied to the footing, the following maximum soil or pile loading shall apply.This value includes any capacity reduction φ factor.

a. Basic Load Combination

Using Group I Working Stress Design, the soil or pile loading shall not exceed 1.0 times theallowable, and for spread footings, the resultant shall fall within the middle one-third of thefooting area. In the case of a pile footing:

(1) No uplift shall be used for Group I loading.

(2) Stability requirements shall be met without mobilizing the piles.

(3) Stability check against overturning shall be taken about the front row of piles.

b. Factored Load Combinations

(1) Soil Pressure or Pile Reactions

For any factored load combination, the soil loading shall not exceed twice the allowable.Maximum pile loading shall be in accordance with the following:

October 1993 9.5 - 1



Guidelines for Footing LocationFigure 9.5.1-1

9.5 - 2 October 1993



Modes of Failure for Spread FootingsFigure 9.5.1-2

October 1993 9.5 - 3



Modes of Failure for Pile FootingsFigure 9.5.1-3

9.5 - 4 October 1993



Groups I-IV, 1.5 x allowable pile bearing capacityGroups V-IX, 1.75 x allowable pile bearing capacity

Soil pressure or pile reaction is computed considering that it is not possible to developany tension between the footing and the soil or pile below. In some special cases,tension in piles may be allowed as explained in Section 9.6.2B2.

c. Stability Load Combination

The following criteria have been developed for design of footings for stability:

When dead load tends to increase stability, use βD = 0.75 in the AASHTO Load FactorCombinations. The resultant shall fall within the middle two-thirds (or uplift on notmore than one-half of the area of the footing or one-half of the piles).

d. Sliding

An adequate factor of safety against sliding based on factored loads shall be maintainedunder all conditions. Defining Pu as the total minimum factored vertical load on the footingand Hu as the total factored horizontal load on the footing, the ratio between these valuesshall be such that:

1.1 Hu ≤ 0.5 Pu

B. Load Distribution Under Footings

1. Force Distribution

A straight line force distribution shall be assumed for resisting forces. Where appropriate, asuitable “bi-axial” analysis shall be used which accounts for the shape of the actual positivepressure area under the footing. Design Aid sheet 9-5A-1 “Stress on a Rectangular Footing,Normal Load Outside Kern” can be used to calculate true soil pressures. The “Bi-Axial StressAnalysis” computer program will also compute this condition. Negative footing reactions will notbe allowed except in the case of friction piles with appropriate reinforcement provided at theconnection between the pile and the footing. See 9.5.2.

2. Footings With Seals

For establishment of seal size for footings with seals, see 9.7. The footing size shall normally beset as 2′- 0″ less than seal size in rectangular dimensions.

Where there is a good possibility that the seal may be eliminated at the time of construction, analternate footing design with no seals should be detailed on the plans. See Section 9.7 for methodof establishing footing elevation in this case.

C. Pedestals

A pedestal is sometimes used as an extension of the footing in order to provide additional depth forshear near the column. Its purpose is to provide adequate structural depth while saving concrete. Forproportions of pedestals, see Figure 9.5.1-5. Since additional forming is required to constructpedestals, careful thought must be given to the trade off between the cost of the extra forminginvolved and the cost of additional footing concrete. Also, additional foundation depth may be neededfor footing cover.

October 1993 9.5 - 5



Whenever a pedestal is used, the plans shall note that a construction joint will be permitted betweenthe pedestal and the footing. This construction joint should be indicated as a construction joint withroughened surface.

D. Footing Design

1. Footing Thickness and Shear Design

The minimum footing thickness shall be 1 foot 6 inches or, for pile supported footings, 2 feet0 inches. The minimum plan dimension shall be 4 feet 0 inches. Footing thickness may be gov-erned by the development length of the column dowels, or by concrete shear requirements, withor without reinforcement. If concrete shear governs the thickness, it is the Engineer’s judgment,based on economics, as to whether to use a thick footing unreinforced for shear or a thinnerfooting with shear reinforcement. Generally, shear reinforcement should be avoided but not atexcessive cost in concrete, excavation, and shoring requirements. Where stirrups are required,place the first stirrup at d/2 from the face of the column or pedestal. For large footings, considerdiscontinuing the stirrups at the point where vu = vc. For proportions of footings and pedestalsand footings on rock, see Figure 9.5.1-5.

Shear strength requirements are stated in AASHTO Specifications. They are summarized inFigure 9.5.1-4.

2. Reinforcement

a. Column Dowels

Column dowels shall be anchored into the footing in such a manner as to adequately transferloads to the footing. Column dowels shall be hooked in order to facilitate placing, preventtheir insertion into wet concrete, and to minimize footing thickness. Bars in tension shall bedeveloped using length, 1.25 Lb, as shown in Chapter 5 of this manual. Bars in compressionshall develop a length, 1.25 Ld, prior to the bend, as shown on Sheet 5-164. Where bars arenot fully stressed, lengths may be reduced in proportion, but shall not be less than 3/4 Ld.

The concrete strength used to compute development length of the bar in the footing shall bethe strength of the concrete in the footing. The concrete strength to be used to compute thesection strength at the interface between footing and column concrete shall be that of thecolumn concrete. This can be allowed because of the confinement effect of the widerfooting.

b. Bottom Reinforcement

Reinforcement shall be designed in accordance with AASHTO provisions and current officepractice shown on Figure 9.5.1-4. However, reinforcement shall not be less than #6 bars at12-inch centers to account for uneven soil conditions and shrinkage stresses.

9.5 - 6 October 1993



January 1991 9.5 - 7



9.5 - 8



c. Top Reinforcement

Top reinforcement shall be used in any case where tension forces in the top of the footingare developed. Where columns and bearing walls are connected to the superstructure, suffi-cient reinforcement shall be provided in the tops of footings to carry the weight of thefooting and overburden assuming zero pressure under the footing. This is the uplift earth-quake condition described under “Superstructure Loads.” This assumes that the strength ofthe connection to the superstructure will carry such load. Where the connection to the super-structure will not support the weight of the substructure and overburden, the strength of theconnection may be used as the limiting value for determining top reinforcement. For theseconditions, the AASHTO requirement for minimum percentage of reinforcement will bewaived. Regardless of whether or not the columns and bearing walls are connected to thesuperstructure, a mat of reinforcement shall normally be provided at the tops of footings. Onshort stub abutment walls (4 feet from girder seat to top of footing), these bars may beomitted. In this case, any tension at the top of the footing, due to the weight of the smalloverburden, must be taken by the concrete in tension.

Top reinforcement for column or bearing wall footings designed for two-way action shall notbe less than #6 bars at 12-inch centers, in each direction while top reinforcement for bearingwall footings designed for one-way action shall not be less than #5 bars at 12-inch centers ineach direction.

9.5.2 Pile Supported Footings

A. General Requirements

Design of pile footings shall follow the general requirements set forth in 9.5.1 for spread footings.Steel H-Pile or timber piles shall be embedded a minimum of 12 inches into the footing where amoment or tension connection is not required. Cast-in-place concrete piles with reinforcing extendinginto footings shall be embedded a minimum of 6 inches. There shall be 11/2 inches of clearancebetween the bottom mat of footing reinforcement and the top of pile (see Figure 9.5.2.1). In determin-ing the proportion of pile load to be used for calculation of shear stress on the footing, any pile withits center 6 inches or more outside the critical section shall be taken as fully acting on that section.Any pile with its center 6 inches or more inside the critical section shall be taken as not acting forthat section. For locations between, the pile load acting shall be proportioned between these twoextremes. For calculation of moment on the footing, any pile with its center outside of the sectionshall be taken at full load. Any pile with its center inside of the section shall not be assumed tocontribute to that amount. All piles shall have an embedment in the soil sufficient to resist lateralforces and develop axial loads.

B. Pile Spacings

Generalized pile spacings are shown in Section 9.6 for each type of pile. Be aware that the action ofthe pile group for friction piles may be quite different than for point bearing piles, in that the groupcan fail as a unit at a lower load than the summation of the individual pile capacities. This effect isaccounted for in Chapter 4, “Modeling Pile Foundation.”

For point bearing piles, the spacing is a minimum of 3 feet, except for timber piles where theminimum spacing is 3 feet 3 inches. Where the load distribution of the pile is partially point bearingand partially friction, consider using an intermediate spacing value. Distance from center of pile tofooting edge for all pile types shall be a maximum of 1.5 times the pile diameter or 1 foot 6 inches.

April 1993 9.5 - 9



Typical Pile Footing Reinforcing PlacementFigure 9.5.2-1

C. Horizontal Force on Pile Groups

Piles resist horizontal forces by a combination of internal strength and the passive pressure resistanceof the surrounding soil. The pile is modeled like a beam on an elastic foundation or by the use ofcomputer programs, i.e., LPILE1. LPILE1 requires soil properties supplied from the Materials Lab inorder to generate P-Y curves. P-Y curves represent the force required to deflect a pile a unit length.Forces and moments are applied to the pile and LPILE1 calculates the deflections along its length.The results can also be used to determine pile lateral and rotational springs. For more information onmodeling individual piles or pile groups, see Chapter 4 “Foundation Modeling.”

D. Uplift Forces

When piles are subject to uplifting forces or a “built in” condition is needed at the top of the pile, thepile must be adequately connected to the footing by means of extended reinforcement, welded bars,or other means. No uplift capacity is allowed due to the bond between pile and embedment intofooting. Uplift pile capacities shall be determined by Materials Lab. Construction methods used forjetted or spudded piles reduce uplift capacity.

9-5:V:BDM9

9.5 - 10 October 1993


Substructure Design Piles and Piling

9.6 Piles and Piling

9.6.1 General Considerations

A. Selection of Pile Type

Piles should not be used where spread footings can be used at allowable basic bearing pressures ofapproximately 2 to 3 ton/sq. ft. or greater. Where heavy scour conditions may occur, pile foundationsshould be considered in lieu of spread footings. Where large amounts of excavation may be necessaryto place a spread footing, pile support may be more economical. The following is a general summaryof comparative pile properties.

Penetrat. Ease of Lateral Ease Pile of Hard Connect. Force of Type Cost Capacity Strata Friction to Struct. Resist. Splice

Steel High High Very High Moderate High. High HP Good

Conc. Moderate Moderate Moderate Moderate Good High CIP High(CIP Good) Precast

w/tip Low

Timber Low Low Poor Moderate Poor Low Low

Cylinder High Very Good Moderate Moderate Very PrecastHigh High Low

B. Friction vs. Point Bearing Piles

Piles may be of friction type or point bearing or a combination of both. AASHTO “Load Capacity ofPiles” shall pertain for the design of piling, except as noted herein. Normally in the absence of a soillayer which can offer adequate resistance to develop full point bearing, the pile shall be considered tobe acting as a friction pile. The Materials Laboratory will provide information as to the ability of thesoil to support the pile load.

The conditions of support of the pile in the soil may affect several structural properties. These maybe: rate of pile elastic shortening, effect of group action and hence spacing, column stability of thepile, and ability to resist lateral forces.

C. Pile Loads and Spacings

The loads allowed and spacing of piles in groups are usually as tabulated below. Many othercombinations are possible; however, their use should be predicated on suitable analysis andconcurrence of the Bridge Design Engineer and the Foundation Engineer.

Pile selection shall be made to give maximum economy combined with adequate load capacity andability of the pile to be driven into the particular material.

January 1991 9.6 - 1



Spacing ofPile Spacing of Point Bearing Edge

Capacity* Material Friction Piles ‡ Piles Distance** Pile Size

40T Timber 3′-3 ″ 3′-3 ″ 1′-6 ″ Spec.

55 T Concrete 4′-0 ″ 3′-0 ″ 1′-6 ″ †Steel »

HP 12 x 53

70 T Concrete 4′-6 ″ 3′-3 ″ 1′-9 ″ +Steel 4′-6 ″ 3′-3 ″ 1′-6 ″ HP 12 x 53

Table 9.6.1BAugust 1974

» 10 BP 42 may be used if the pile is point bearing for this capacity.

† 12-inch diameter min. for Concrete Filled Casing.13-inch diameter min. for Precast or Precast Prestressed.14-inch diameter min. Butt for Tapered.10-inch or 12-inch Square Precast Prestressed.12-inch diameter min. for Hollow Prestressed Spun Piles.

+ 14-inch diameter min. for Concrete Filled Casing.16-inch diameter min. for Precast or Precast Prestressed.

* Capacity shown is rated Basic (working) load value and includes the effect of any downdrag forces.

‡ The Converse-Labare Formula (AASHTO “Group Pile Loading”) need not be applied to pile valuesshown here. This formula reduces the vertical load carry capacity of a pile group. See FoundationModeling, Chapter 4, for lateral load capacity reduction for pile groups.

** Center of pile to footing edge.

The above table is a guide to usual practice and is not intended to restrict the use of other capacitiesand spacings where needed.

Maximum pile spacings should be limited to about 10 feet. With spacings beyond this, the shearbetween the footing and column or wall may become a problem.

9.6.2 Design Considerations

A. Column Action

Consideration shall be given to the pile acting as a column. Piles which extend above the groundsurface shall be analyzed by the appropriate column design procedures. Piles which are driventhrough very weak soils should be designed for reduced lateral support, using information from theMaterials Laboratory as appropriate. Piles driven through firm material normally can be considered tobe fully supported for column action (buckling not critical).

9.6 - 2 April 1993



B. Uplift Capacity

1. Introduction

The ability of a pile to carry uplift loads is highly dependent upon the strata into which itis driven. Unless detailed knowledge of that strata is available at the time of design, the pileshould not be relied on to carry uplift loads. In all cases where uplift loads are to be carried, theconnection between the pile and the footing must be carefully detailed. The bond between thepile and the seal may be considered as contributing to the uplift resistance. This bond value shallbe limited to 10 psi.

2. Computation of Uplift Capacity

Appropriate values of uplift should be those values recommended by the Materials Lab. If theinformation is not available, the following will give guidance on uplift capacity. Pile uplift maybe considered to act to assist in carrying factored loads within the limits specified below. Whenpile uplift is considered to carry a portion of the factored loads, a check shall be made to ensurethat no tension on the piles is necessary to carry any basic combination (factor of 1.0) of DL, LL,Wind, or Stream Flow.

Where pile tension is used, it shall be computed as follows:

Ro =

Where B is the average blow count from the test hole log in blows/foot and Ro is the resistance ofthe pile surface in Ton/Ft.2, the total resistance of the pile to pull out is then Rp = Ro(1p)Pwhere 1 is the effective pile length and P is the perimeter of the pile. Consider P to be2 X (Flange width plus depth) for H Piles. The above computed value for Ro gives essentially anultimate pull out value. To give usable values, use a factor of safety of 3 for working stressdesign on a “capacity reduction factor” of 2/3 for load factor design. Do not use more than 40 per-cent of the pile downward load capacity, however. For calculation, use a length of pile 5 feetshorter than minimum tip elevation.

3. Cautions to be Exercised with Respect to Pile Uplift

a. The pile must be a friction pile and over 10 feet in length. Whenever uplift is to be used inthe design, the Foundation Engineer shall be consulted. Do not use for full point bearingpiles.

b. The tension connection between the pile and the structure must be adequate.

c. The pile must be adequate to carry tension throughout its length. For example, a timber pilewith a splice sleeve could not be used.

d. Preboring, jetting, or spudding must not be used to aid in driving the pile and must be sonoted in the plans or special provisions.

e. The use of pile load tests to verify the uplift capacity of the piling should be considered.

January 1991 9.6 - 3

B50



C. Lateral Resistance

Lateral forces applied to piles must be carried either by passive soil resistance and bending or bybattered piles.

1. The capacity of the pile to carry horizontal loads should be investigated using beam on elasticfoundation theory. A computer program (LPILE) is available to assist in this calculation. Soilmodules can be obtained for each soil layer from the Materials Laboratory.

For material such as fill compacted to specification requirements, a soil modulus value of 40 tonsper cubic foot, constant variation, might be used. This means that the elastic modulus of the soilat one foot depth is 40 T/sq. ft., at 2-foot depth is 80 T/sq. ft., etc. For other types of soil, themodulus may not vary from top to bottom. The limitation on soil stress is, at the same time,3.0 tons (working stress) per square foot. Again, some deflection (about of 0.5 inch) will usuallybe associated with this resistance and that deflection must be acceptable in the total design.

2. Passive Resistance of Piles

In lieu of the above analysis, a maximum passive resistance of 3 tons (ultimate capacity 6 tons)may be assumed for each foundation pile provided the footing is built directly on the soil andthat the soil below the footing is capable of carrying this load. This figure is to be used for12-inch diameter or 12-inch square piles and larger only. For 10-inch square piles, use half ofthis amount. For this condition, the bending in the pile is neglected and assumed to be within thecapacity of the pile to resist. It should be noted that a horizontal deflection will be associatedwith the development of this resistance.

3. Pile Bents

Piles which support footings or pile caps that are not in contact with the soil below them, must betreated as columns, subject to bending and axial load. The calculation of lateral resistance mustfollow a procedure similar to the one mentioned above.

4. Battered Piles

Where passive pressures will not carry the imposed lateral loads, or where horizontal rigidity isrequired, battered piles must be used. The lateral force which can be resisted by a single batteredpiles is limited by a function of applied vertical load, and this must not be exceeded. Maximumbatter shall be 41/2:12.

D. Other Considerations

1. Driving stresses are calculated by the Materials Lab. Additional information such as recom-mended pile type, wall thickness, bearing stresses, etc., can be requested from their office.

2. Elastic Settlement

The effect of elastic settlement should not be used to develop factors for normal frame momentdistribution. It is valuable when evaluating forces developed by deflection of piers where theseforces must be carried by the structure. Actual footing rotation, due to applied loads on a pilesupported footing, may be computed using the elastic shortening of the piles in the group andusing the usual PL/AE equation. The problem then is to establish an appropriate L value. Forfully point bearing piles, this length can be taken to be the full length to the bearing strata. Forfully friction piles, half of the estimated pile length might be appropriate with intermediatelengths being used for piles which will be partially point bearing.

9.6 - 4 July 2000



3. Pile Splices

Pile splices shall be avoided where possible. If splices may be required in timber piling, a spliceshall be detailed on the plans. Splices between treated and untreated timber shall always belocated below the permanent water line. Concrete pile splices shall have the same strength asunspliced piles.

4. Driving Considerations

The conditions required for driving shall be considered in all designs. Some of the conditions areas follows:

a. Soil Character

The type of soil governs the pile type and may require the use of points or shoes. Timberpiles cannot ordinarily be driven through hard gravel layers, and such layers may require theuse of concrete or steel piles.

When cobbles, boulders, or rock fills exist at the site, a drilled pile or shaft should be used.

b. Preboring

Preboring is used when an intermediate hard layer must be penetrated in order to reachbearing layers below, when the amount of driving must be limited to avoid disturbance tobuildings, or when precise placement of the piles is required. Preboring will normally becarried as a separate bid item. On widenings, driving piles through existing fills oftenrequires spudding or jetting to assist in pile driving. These are contractor options and are notpay items. See Standard Specifications for contractor requirements.

c. Clearances

It is the designer’s responsibility to ensure that sufficient room is available for driving piling.This is a problem when working on widenings adjacent to existing structures and in urbanareas. Normally 20 feet of minimum headroom is necessary. Timber piles can be driven twofeet horizontally from a vertical surface, but additional clearance is desirable. Occasionally,driving the piling from the existing structure is the only alternative. In such a case, theability of the supporting structure to support the pile driver and the dynamic forces must beanalyzed and shall be noted in the Special Provisions.

Access room for the driver to enter the site must be assured.

d. Maximum Batter

The batter on piles shall not exceed 41/2 to 12. Piles with batters in excess of this becomevery difficult to drive and the bearing values become difficult to predict.

Ensure that battered piling do not intersect piling from adjacent footings within the maxi-mum length of the piles.

e. Pile Load Tests

Pile load testing is used when doubt exists as to whether or not the driving formula actuallyrepresents the capacity of the pile. Where such tests are used, they are conducted by theMaterials Laboratory. On large jobs, consideration should be given to pile load tests in thedesign stage in order to reduce foundation costs.

January 1991 9.6 - 5



f. Estimate Pile Length

Pile length quantity calculations are determined from the estimated tip elevation given in theSoils Report.

A 40-ton timber pile in granular material will usually develop full load by the time it is wellinto a layer of 25 to 30 blow count.

9.6.3 Concrete Piles

A. Specifications

When concrete piles are specified, the Standard Specifications Section 6-05 allow the contractor toselect the pile type, i.e., precast or cast-in-place and describes the network of construction. Reinforce-ment for 55- and 70-ton piles is specified in the Standard Specifications. Where bearing values arespecified on the plans other than 55- and 70-ton piles, or if the standard reinforcement is inadequatefor the application, the details or Special Provisions must provide for the reinforcement. The follow-ing criteria shall be used for cast-in-place concrete piles:

1. The wall thickness will be determined by Materials Lab analysis of pile driving formula. Unlessotherwise specified, the design shall be based on a steel shell thickness of 1/4 inch for piles lessthan 14 inches in diameter, 3/8 inches for piles 14 to 18 inches in diameter, and 1/2 inch for largerpiles.

2. Piles shall be embedded into the footing a minimum of 6 inches. The reinforcing mat shall have11/2 inches of cover to the top of the pile.

3. Class 4000 LS Concrete shall be specified for inside the pile. The top 10 feet of concrete in thepile is to be vibrated.

4. The full cross section of the steel shell, minus 1/16 inch for corrosion, is to be used in determiningthe pile stiffness and foundation modeling. It can also be considered as confinement reinforce-ment for the internal cage except at pile/footing interface. The moment of inertia of the pile is tobe computed by adding the components I pile = Iconc + (n)(Ishell) + (n)(Ireinf).

5. A steel reinforcing cage shall be used to tie the pile to the footing. The reinforcement, alone,shall be sufficient to resist the total moment throughout the length of pile without considering theshell. The minimum reinforcement shall be 0.5 percent of the gross concrete area for SeismicPerformance Categories A and B, and 0.75 percent for Category C as required per AASHTO’sSeismic Guideline Specifications, Chapter 6. No less than four No. 5 bars shall be used. Thereinforcement shall extend above the pile into the footing a distance equal to 1.25 1d (tension).

6. Above the top of the pile, the vertical steel reinforcing bars shall be tied together with closely spacedhoops or spirals as required by the seismic guide specifications. Inside the pile, No. 4 hoops at12-inch centers is minimum required for Category B and 9-inch centers for Category C.

B. Concrete Pile Types

The following types of concrete piles have been commonly used:

1. Cast-in-Place Concrete Piles Utilizing Driven Steel Pipe Casings

The casing diameter and thickness is called for in the specifications. The bottom of the casing iscapped with a suitable flat plate before driving. Special tips are sometimes used when difficultdriving is expected.

9.6 - 6 April 1993



2. Precast Concrete Piles

These piles may be of various cross-sectional shapes and are reinforced for handling stresses. Agood knowledge of the in-place length is required since splicing is difficult. Due to handlingrequirements, only short lengths can be used. See Standard Plan Sheet E-4 for precast concretepiles, 13-inch diameter.

3. Precast Prestressed Concrete Piles

These piles are hexagonal, square, or circular in cross-section and are prestressed to allow longerhandling lengths. Again, close length determination at time of driving the test pile is important.

Precast prestresed concrete piles are usually specified in accordance with Standard Plans such asSheet E-4 for 13-inch diameter piles and Sheet E-4a for 16- and 18-inch diameter piles.

9.6.4 Sheet Piling (H Piles)

Steel piles are normally used where there are hard layers which must be penetrated in order to reach anadequate point bearing stratum. Steel stress should be limited to 9.0 ksi (working stress) on the tip.H piling can act efficiently as friction piling due to its large surface area. Do not use steel H piling wherethe soil consists of only moderately dense material. In such conditions, it may be difficult to develop thefriction capacity of the H piles and excessive pile length may result. The bridge layout will denote steelpiles with capacity and size, e.g., steel pile 70-ton HP 12 x 53.

9.6.5 Timber Piles

Timber piles have the lowest cost per foot of any of the pile types. Timber piles may be untreated ortreated. Untreated piles are used only for temporary applications or where the entire pile will be perma-nently below the water line. Composite piles, treated and untreated, may be used if the pile length is longand a splice will be required. Where composite piles are used, the splice must be located below thepermanent water table. If doubt exists as to the location of the permanent water table, treated timber pilesshall be used.

Where dense material exists, consideration should be given to allowing jetting (with loss of upliftcapacity), use of shoes, or use of other pile types.

9.6.6 Sheet Piles

Sheet piles are normally used for cofferdam and shoring and cribbing, but are usually not made a part ofpermanent construction.

9.6.7 Cylinder Piles

Large diameter cylinder piles are used because of their high allowable bearing and bending strengthcapacity.

Cylinder piles are commonly cast-in-place concrete and the shaft is formed by drilling. See “DrilledShafts” Section 9.8.

9-6WORK:V:BDM3

January 1991 9.6 - 7


Substructure Design Seals

9.7 Seals

9.7.1 Purpose

A concrete seal is used within the confines of a cofferdam to permit construction of the pier footing andcolumn in the dry. This type of underwater construction is practical to a water depth of approximately50 feet.

Seal concrete must be placed underwater. This is usually accomplished with the use of a tremie. A tremieis a long pipe that extends to the bottom of the excavation and permits a head to be maintained on theconcrete during placement. After the concrete has been placed and has obtained sufficient strength, thewater within the cofferdam is removed. The weight of the seal concrete resists the hydrostatic pressureexerting force at the base of the seal. In Figure 9.7.1-1, some of the factors that must be considered indesigning a seal are illustrated.

*Usually 1 foot 0 inches for design (use 1 foot 0 inches greater than design seal dimensions for quantitycalculations).

Figure 9.7.1-1

9.7.2 General

A. Normal High Water Elevation

The Normal High Water Elevation is defined as the highest water surface elevation that may normallybe expected to occur during a given time period. This elevation, which appears on the HydraulicsData Sheet, is obtained from discussions with local residents or by observance of high water marks atthe site. The normal high water is not related to any flood condition.

March 1993 9.7 - 1



B. Seal Vent Elevation

The headquarters Hydraulics Section recommends a seal vent elevation in accordance with the followingcriteria:

1. Construction time period not known.

If the time period of the footing construction is not known, the vent elevation reflects the normalhigh water elevation that might occur at any time during the year.

2. Construction time period known.

If the time period of the footing construction can be anticipated, the vent elevation reflects thenormal high water elevation that might occur during this time period. (If the anticipated timeperiod of construction is later changed, the Hydraulics Section shall be notified and appropriatechanges made in the design.)

C. Scour Depth

The depth of the anticipated scour is determined by the Headquarters Hydraulics Section. The bottomof the footing, or bottom of seal, if used, shall be no higher than the scour depth elevation. Afterpreliminary footing and seal thicknesses have been determined, the designers shall review the antici-pated scour elevation with the Hydraulics Section to ensure that excessive depths are not used.

D. Recommended Foundation Elevation (from Soils Report)

Based on the results obtained from test boring made at the site, the Soils Engineer determines afoundation elevation and accompanying soil pressure that will not result in excessive settlement of thestructure. If other factors control, such as scour or footing cover, the footing elevation may have to belower than determined by the Soils Engineer.


A. Seal Positively Required

When there is little possibility of the seal being eliminated during construction, the followingprocedure shall be used for design:

1. Preliminary Sections

The bottom of the seal elevation shall be the lower of the scour elevation or the foundationelevation as recommended by the Soils Engineer. Footing cover requirements of Section 9.5apply when the top of footing is exposed to view.

The size of the seal is selected based on the following:

a. Allowable Soil Pressure

The size of the seal required in order to meet the allowable soil pressure shall be calculatedusing column moments at the base of the footing and vertical load applied at the bottom ofthe seal.

b. Stability

Stability need only be checked at the base of the footing.

2. Final Design

After preliminary sections are determined, the final design is made based on the criteria outlinedin Section 9.5.

9.7 - 2 March 1993



3. Unusual Conditions

At times, unusual conditions are encountered such as rock formations or deep foundations thatrequire special considerations in order to arrive at the most optimum design. When this occurs, itis advisable to discuss the proposed foundation design with both the Soils Engineer and theBridge Hydraulics Section prior to final plan preparation.

B. Seal May Not Be Required

When it is possible but not probable that a seal may be required during construction, the seal andfooting are designed as described in Section 9.7.3A. In addition, a separate design is made for afooting without a seal. The top of the footing, or pedestal when used, shall be no higher than theelevation set by cover requirements. The bottom of the footing shall be no higher than the foundationelevation recommended by the Soils Engineer or the scour elevation set by Headquarters Hydraulics.This alternate footing without a seal shall be detailed on the plans. If the alternate footing elevation isdifferent from the footing with seal, it is also necessary to note on the plans the required changes inlength of column bars and increased number of ties. The quantities shall be based on the footingdesigned with a seal. Both designs shall be included in the plans.

9.7.4 Pile Support Footings

The top of the footing, or pedestal when used, is set by cover requirements of Section 9.5. The bottom ofseal elevation is based on the stream scour elevation determined by Hydraulics. A preliminary analysis ismade using the estimated footing and seal weight, and the column moments and vertical load at the baseof the footing to determine the number of piles and spacing. Seal size will be 1 foot 0 inches larger thanthe footing all around. From Design Aid 9.7-A1, the seal thickness can be obtained based on the ventelevation.

After preliminary dimensions are determined, the final design is made using the criteria outlined inSection 9.5. If the seal is omitted during construction, the bottom of footing shall be set at the scourelevation and an alternate design is made.

9-7:V:BDM9

March 1993 9.7 - 3


Substructure Design Drilled Shafts

9.8 Drilled Shafts

9.8.1 General

A. Definition

A drilled shaft is a machine and/or manually excavated shaft in soil or rock that is filled withconcrete and reinforcing steel. A drilled shaft is circular in cross-section and may be belled at thebase to provide greater bearing area.

Vertical load is resisted by the drilled shaft in base bearing and side friction. Horizontal load isresisted by the shaft in horizontal bearing against the surrounding soil or rock.

B. Characteristics

The following special features distinguish drilled shaft from other types of foundations:

1. The drilled shaft is installed in a drilled hole, unlike the driven pile.

2. Wet concrete is cast and cures directly against the soil forming the walls of the bore hole.Temporary steel casing may be necessary for stabilization of the open hole and is extractedduring concrete placement.

3. The installation method for drilled shafts is adapted to suit the subsurface conditions.

C. Terminology

Other terminology commonly used to describe a drilled shaft includes: drilled pier, drilled caisson,and bored pile. In soil, the shaft is normally drilled with an auger. In rock, a core barrel bit is used incombination with blasting.

9.8.2 Types of Drilled Shafts

Drilled shafts may be categorized by two different methods. The first method defines shafts by their loadtransfer. The second method classifies shafts by their type of construction.

A. Classification by Load Transfer to the Soil

1. Straight shaft, end-bearing drilled shaft. Load is transferred by base resistance only.

2. Straight shaft, side-wall shear or friction drilled shaft. Load is transferred by shaft shearresistance only.

3. Straight shaft, side-wall shear and end-bearing drilled shaft. Load is transferred by combinationof shaft and base resistance.

4. Belled or underreamed drilled shaft. Load is transferred by the bell in end-bearing. Shaft shearresistance may be considered, depending on the dimensions of the drilled shaft and overburdenmaterial.

5. Straight or belled drilled shaft on hard soil or rock. Shaft shear resistance may be considered,under some circumstances, when the shaft is socketed into good rock.

B. Classification by Type of Construction

1. Not cased, reinforced.

2. Temporary casing, removed while placing concrete.

3. Temporary casing with permanent liner.

January 1991 9.8 - 1



4. Permanent casing.

5. Underreamed shafts.

6. Underwater concrete placement.

9.8.3 Advantages and Disadvantages of the Drilled Shaft

A. Advantages

1. Construction equipment is normally mobile and construction can proceed rapidly.

2. The excavated material and the drilled hole can often be examined to ascertain whether or not thesoil conditions at the particular site agree with the projected soil profile.

3. Changes in geometry of the drilled shaft may be made during the progress of a job if thesubsurface conditions so dictate. These changes include adjustment in diameter and in penetrationand the addition or exclusion of underreams.

4. The heave and settlement at the ground surface will normally be very small.

5. The personnel, equipment, and materials for construction are usually readily available.

6. The completed excavation can often be carefully inspected prior to construction if casing orslurry is not required. For end-bearing situations, the soil beneath the tip of the drilled shaft canbe probed for cavities or for weak soil.

7. The noise level from the equipment is less than for some other methods of construction.

8. The drilled shaft is applicable to a wide variety of soil conditions For example, it is possible todrill through a layer of cobbles, many feet into sound rock, and through frozen ground.

9. Very large loads can be carried by a single drilled shaft.

10. Designs of drilled shafts can be made considering load transfer both in end bearing and in sideresistance.

11. The behavior of a drilled shaft at a site can be monitored by available methods of instrumentationand analytical techniques.

12. Use in constricted areas. The shaft occupies less area than a footing and thus can be built closerto railroads and existing structures.

13. When drilling inside a steel casing, pollution of lake or river water is minimized.

14. Drilled shafts may be more economical than spread footing construction, especially when thefoundation is deep.

B. Disadvantages

1. Construction procedures are critical to the quality of the drilled shaft, and very careful inspectionis required.

2. Construction techniques are sometimes very sensitive to subsurface soil and rock conditions.Boulders can be a serious problem, especially in smaller diameter shafts.

3. The proper performance and interpretation of load tests on drilled shafts requires expertknowledge and experience.

4. Lack of general knowledge of construction problems and design methods has restricted the use ofdrilled shafts.

9.8 - 2



5. Shaft length within predicted scour range is not considered effective.

6. Reduced redundancy, with fewer number of shafts versus a large number of piles.

9.8.4 Preliminary Soils Investigation

For proper design and construction, a site investigation is very important not only to the design engineer,but to the contractor as well. All information that is gained in a site investigation should be made avail-able to potential contractors.

A. Surface Features

A careful review of Surface Features should be made from the field data and soils report. Surfacefeatures, such as boulders or cobbles, may dictate whether drilled shafts are feasible or desirable.

Among the things to be aware of are the following:

1. The existence of utilities and any restrictions concerning their relocation or removal.

2. A drilled shaft requires less area than a footing and is appropriate as foundation support nearexisting structures or facilities such as railroad tracks. With less area, excavation, shoring, andcribbing costs are reduced. Installation of drilled shafts produce less noise and vibration than piledriving.

3. Water table elevation will influence the method of construction of the drilled shaft. A casing maybe used to place concrete in the dry or a tremie used to place concrete in water or slurry.

4. A contour map may be needed to determine the finished top elevation of the drilled shaft.

5. Site access by construction equipment.

6. Environmental considerations may also dictate the methods of construction.

B. Subsurface Investigation

A preliminary soils investigation and testing is needed to determine the pertinent characteristics of thesoil in which the drilled shaft is to be constructed. The characteristics of the soil will influence thedesign of the shaft and the method of construction.

C. Methods of Investigation

The standard method for obtaining soil characteristics involves laboratory testing of undisturbedsamples and the use of in-situ techniques such as: Goodman Jack, the static cone test, andpressuremeter tests. The standard penetration test is used extensively.

D. Subsurface Conditions Affecting Construction

1. The stability of the subsurface soils when the excavation is made will determine whether a casingis necessary or not. The dry method (see Section 9.8.7A) of construction can be used only wherethe soils will not cave or collapse. The casing or slurry method (see Section 9.8.7B and 9.8.7C)must be used if there is danger of caving or collapse.

2. It must be determined if groundwater exists at the site and what rate of flow can be expected intoa shaft excavation. The presence of groundwater will indicate if a tremie pour shaft will beneeded or if a tremie seal must first be poured, the shaft dewatered, and then the remainder of theshaft poured in the dry. In either instance, the design must assure access to the top of the seal toallow the surface to be thoroughly cleaned prior to placing additional concrete (i.e., the shaftmust be large enough to accommodate a worker or the top surface of a small diameter shaft sealmust be located so that it is accessible).

January 1991 9.8 - 3



3. Any artesian water conditions must be clearly identified in the contract documents. Artesianwater flowing into a pour could spoil the concrete or cause collapse or heaving of the soil at theexcavation.

4. The presence of cobbles or boulders can cause difficulties in drilling. Drilling with core barrelbits or blasting can remove obstructions.

5. The presence of existing foundations or structures.

6. Presence of landfill that could contain hazardous or dangerous material that cannot be easilyexcavated.

7. Presence of rock may require more sophisticated drilling methods or shooting with explosives.

8. Presence of a weak stratum below the base of the drilled shaft. For this situation, drilling mayhave to be extended below the weak stratum.

9.8.5 Design of Drilled Shafts for Axial Load

The total axial capacity of the drilled shaft is composed of two factors: the base capacity and the sidecapacity. The general formula is:

QT = QB + QS

QT = total axial capacity of the foundationQB = the base capacityQS = the side capacity

QB and QS are treated as independent quantities although research has shown that the base resistance andside resistance have some independence. The degree of reliability of the above formula is compatiblewith the soils information obtained from a routine investigation. Ultimate unit base resistance and sideresistance will be obtained from the Foundation Engineer. Unit side resistance may vary with depth, butnormally one value is given for the entire depth of the shaft. Ultimate base and side resistances arefurnished by the Foundation Engineer along with a factor of safety.

A. Ultimate Failure vs. Excessive Settlement

There are basically two criteria by which recommendations for unit base and shaft resistances arearrived at by the Foundation Engineer. First, the ultimate soil resistance is determined using limitstate criteria. Second, an estimate of the settlement of the shaft is made using anticipated loads. If it isfelt that settlements are excessive, then the settlement criteria will control the design of the shaft. Thedesigner should indicate to the Foundation Engineer what settlements would be acceptable in thedesign. Normally 1 inch is adequate. It must be cautioned, however, that in deep shafts, it is some-times necessary to have vertical deflections on the order of 2 percent of the shaft diameter in order todevelop the base resistance.

B. Factor of Safety

For the design of drilled shafts, the Foundation Engineer should be consulted on ultimate base andshear resistances along with a factor of safety. Drilled shafts are designed by load factor methods. Forfactored load combinations, see Section 9.5.1(3b) for Maximum Pile Load. Group I Basic ServiceLoads are checked against allowable axial bearing and side friction supplied from the Materials Lab.

9.8 - 4



C. Spacing, Depth, Diameter Reinforcing, and Concrete Strength of Drilled Shafts

1. Spacing

In situations where the design load cannot be sustained by a single shaft, several drilled shaftsmay be installed to act as a group. If the spacing between shafts in a group is too small, exces-sive settlement may occur along with a reduction in the side resistance. As a guide to design, anefficiency of 70 percent is recommended for drilled shaft groups in clay and 100 percent forgroups in sand, when the spacing between shafts is in the range of 2.5B to 4B (B = shaftdiameter). The Foundation Engineer will normally give a recommendation on spacing betweenshafts in a group.

2. Depth

In order to develop a high base resistance, the drilled shaft must have sufficient depth of soilabove the base. Depths between 3B and 5B (B = shaft diameter) are recommended for design.The Foundation Engineer will normally recommend a depth. There may be a limitation on thedepth of penetration due to equipment limitations. Penetrations of 100 feet and more are notuncommon.

3. Diameter

The diameter of a shaft should be a minimum of 18 inches. The shaft diameters should bespecified in 6-inch increments. The maximum diameter of the shaft depends on the availability ofequipment. Diameters in the order of 10 feet to 12 feet are common.

4. Reinforcing and Concrete Strength

Due to soil conditions and construction methods, concrete may not be placed in the dry. Areduction in concrete strength used for design shall be as follows:

a. Shaft diameter 4 feet 0 inches or less – assumed concrete compressive strength shall be 0.85fc′ . Concrete placed by tremie method is confined to small area and segregation is reduced.Cover requirement – 3-inch minimum to 6-inch maximum.

b. Shaft diameter 4 feet 6 inches or more – use 0.60 fc′. Cover requirement – 6-inch minimumto 12-inch maximum.

Reinforcing shall be detailed to minimize congestion. Longitudinal reinforcing extending intofooting should be straight. If hooked, detail so that casing can be removed while placing con-crete. Percentage of reinforcing shall be 0.5 percent minimum and 4 percent maximum. Use oftwo concentric circular cages shall be avoided.

January 1991 9.8 - 5



9.8.6 Design of Drilled Shafts Subject to Lateral Loads

A. General Modeling Technique

The modeling technique involved in the analysis of laterally loaded shafts depicts the soil surroundingthe shaft as a set of linear or nonlinear elastic springs. See Figure 9.8.6-1 for illustration.

Model of Laterally Loaded ShaftFigure 9.8.6-1

Present day computer analysis techniques can handle a finite number of springs. The correctmathematical solution involves the solution of an infinite number of springs. The problem is one of abeam-on-elastic foundation which involves the solution of a fourth order differential equation. Theexact mathematical solution is normally difficult except in the very limited cases. Therefore, thismethod of solution is considered impractical for the normal design problems.

The most practical means for analysis of the drilled shaft for lateral loads is by computer. Foradditional modeling techniques, see Chapter 4 Foundation Modeling.

9.8 - 6



B. P-Y Curves

Horizontal deflection of the soil due to load is normally represented by “P-Y” curves. P stands for aforce per unit length of the shaft such as kips per foot. Y is the horizontal deflection of the shaft inunits such as feet. The P-Y relationship usually will vary with depth of the shaft. A reduction forgroup action will be required if the shafts are spaced less than three diameters normal to the directionof loading and less than six to eight diameters parallel to the direction of loading. The FoundationEngineer will provide the design engineer with P-Y curves for the design of the drilled shafts.

A set of P-Y curves must be derived for computer analysis of a drilled shaft.

Set of Nonlinear P-Y CurvesFigure 9.8.6-2

January 1991 9.8 - 7



Another concept in soil mechanics is that of the Soil Modulus “ES” which is defined as -P/Y. This term willhave units such as kips per square foot.

Illustration of the Secant ModulusFigure 9.8.6-3

The soil modulus is taken as being a linear function of depth. Since the P-Y relationship is nonlinear,the modulus ES will be a secant modulus.

C. Analysis by Computer

1. Dr. Reese Program

The “Analysis of Laterally Loaded Piles” program by Dr. Lymon Reese will accommodate P-Ycurve input data for the solution of laterally loaded piles. Linear P-Y curves are generated fordifferent soil layers with known soil properties. The program referred to as “LPILE1” will notallow simultaneous solution of the superstructure and substructure. The program is mostcommonly used to analyze shafts.

2. PILANA

This acronym describes a modeling technique, using STRUDL, to solve lateral loads on piles.The soil spring coefficient (P-Y relationship) must be linear. Superstructure and substructure maybe solved for simultaneously.

3. Pile — Structure Interaction Analysis

The McAUTO STRUDL program will solve the lateral load on a pile problem. P-Y curverelationship values may be entered directly. P-Y values may be linear or nonlinear. Bothsuperstructure and substructure may be analyzed simultaneously. The McAUTO STRUDL pro-gram has the most capabilities of the three computer programs listed.

9.8 - 8



D. Shaft Design

1. Stability

Normally, the soil surrounding a foundation element provides bracing against a buckling failure.For this reason, the drilled shaft can be designed as a short column when the shaft is entirelybelow the groundline. When the shaft extends above the ground a check for stability should bemade. See Section 9.2.1E of the Bridge Design Manual Criteria. The effects of scour must beconsidered in the analysis.

2. Axial Load, Bending Moment, and Shear

The axial load along the shaft varies due to the side friction. It is considered conservative,however, to design the shaft for the full axial load plus the maximum moment. The entire shaftnormally is then reinforced for this axial load and moment, Longitudinal reinforcing should notbe less than 0.5 percent of the area of concrete.

Design shaft for axial load bending movement and shear similar to the design of a column.

9.8.7 Construction Methods

A. Dry Method

The dry method is applicable to soils above the water table that will not cave or slump when the holeis drilled to its full depth. A soil that meets this specification is a homogenous stiff clay. The drymethod can be employed with sands above the water table if the sands have some cohesion.

The dry method can be used for soils below the water table if the soils are low in permeability so that onlya small amount of water will seep into the hole during the time the excavation is open.

The dry method consists of drilling a hole, without casing, placing a rebar cage, and then filling thehole with concrete.

B. Casing Method

The casing method is applicable to sites where soil conditions are such that caving or excessivedeformation will occur when a hole is excavated. An example of such a site is a clean sand below thewater table.

This method employs a cylindrical (usually steel) casing inside the hole to hold back the caving soil.The casing is removed from the hole during concrete placement.

C. Slurry Displacement Method

A Bentonite Slurry is introduced into the excavated hole to prevent caving or deformation of loose orpermeable soils. Drilling continues through the slurry. When the desired depth is reached, the rebarcage is lowered into the hole and the slurry. Concrete is then tremie poured into the hole. Slurry isdisplaced by the heavier concrete and collected at the surface in a sump. The slurry may be usedagain in another hole.

9-8WORK:V:BDM9

January 1991 9.8 - 9


Substructure Design Application of LRFD Code to WSDOT Foundation Design

July 2000 9.9-1

9.9 Application of LRFD Code to WSDOT Foundation Design

9.9.1 Overall Design Process, Roles, and Responsibilities

A flowchart is provided in Figure 9.9.1-1 which illustrates the overall design process needed toaccomplish an LRFD foundation design. The steps in the flowchart are defined as follows:

Conceptual Bridge Foundation Design — This design step results in an informal communication producedby the Geotechnical Branch at the request of the Bridge and Structures Office which provides a briefdescription of the anticipated site conditions, an estimate of the maximum slope feasible for the bridgeapproach fills for the purpose of determining bridge length, conceptual foundation types feasible, andconceptual evaluation of potential geotechnical hazards such as liquefaction. In general, no test holesare drilled at this stage, as only existing site data is used for this determination. The purpose of theserecommendations is to provide enough geotechnical information to allow the bridge preliminary planto be produced.

Develop Site data and Preliminary Bridge Plan — During this phase, the Bridge and Structures Officeobtains site data from the region (see WSDOT Design Manual) and develops a preliminary bridge planadequate for the Geotechnical Branch to locate borings in preparation for the final design of the structure(i.e., pier locations are known with a relatively high degree of certainty). The Bridge and Structures Officewould also provide the following information to the Geotechnical Branch to allow them to adequatelydevelop the preliminary foundation design:

• Anticipated structure type and magnitudes of settlement (both total and differential) the structurecan tolerate.

• At abutments, the approximate maximum elevation feasible for the top of the foundation inconsideration of the foundation depth.

• For interior piers, the number of columns anticipated, and if there will be single foundation elementsfor each column, or if one foundation element will support multiple columns.

• At stream crossings, the depth of scour anticipated, if known. Typically, the Geotechnical Branchwill pursue this issue with the OSC Hydraulics Office.

• Any known constraints that would affect the foundations in terms of type, location, or size, or anyknown constraints which would affect the assumptions which need to be made to determine thenominal resistance of the foundation (e.g., utilities that must remain, construction staging needs,excavation, shoring and falsework needs, other constructability issues).

Preliminary Foundation Design — This design step results in a memorandum produced by theGeotechnical Branch at the request of the Bridge and Structures Office which provides geotechnical dataadequate to do the structural analysis and modeling for all load groups to be considered for the structure.The geotechnical data is preliminary in that it is not in final form for publication and transmittal topotential bidders. In addition, the foundation recommendations are subject to change, depending on theresults of the structural analysis and modeling and the effect that modeling and analysis has on foundationtypes, locations, sizes, and depths, as well as any design assumptions made by the geotechnical designer.Preliminary foundation recommendations may also be subject to change depending on the constructionstaging needs and other constructability issues which are discovered during this design phase.Geotechnical work conducted during this stage typically includes completion of the field explorationprogram to the final PS&E level, development of foundation types and capacities feasible, foundation



9.9-2 July 2000

depths needed, P-Y curve data and soil spring data for seismic modeling, seismic site characterizationand estimated ground acceleration, and recommendations to address known constructability issues.A description of subsurface conditions and a preliminary subsurface profile would also be provided atthis stage, but detailed boring logs and laboratory test data would usually not be provided.

Structural Analysis and Modeling — In this phase, the Bridge and Structures Office uses the preliminaryfoundation design recommendations provided by the Geotechnical Branch to perform the structuralmodeling of the foundation system and superstructure. Through this modeling, the Bridge and StructuresOffice determines and distributes the loads within the structure for all appropriate load cases, factors theloads as appropriate, and sizes the foundations using the foundation nominal resistances and resistancefactors provided by the Geotechnical Branch. Constructability and construction staging needs wouldcontinue to be investigated during this phase. The Bridge and Structures Office would also provide thefollowing feedback to the Geotechnical Branch to allow them to check their preliminary foundationdesign and produce the Final Geotechnical Report for the structure:

• Anticipated foundation loads (including load factors and load groups used).

• Foundation size/diameter and depth required to meet structural needs.

• Foundation details which could affect the geotechnical design of the foundations.

• Size and configuration of deep foundation groups.

Final Foundation Design — This design step results in a formal geotechnical report produced by theGeotechnical Branch which provides final geotechnical recommendations for the subject structure.This report includes all geotechnical data obtained at the site, including final boring logs, subsurfaceprofiles, and laboratory test data, all final foundation recommendations, and final constructabilityrecommendations for the structure. At this time, the Geotechnical Branch will check their preliminaryfoundation design in consideration of the structural foundation design results determined by the Bridgeand Structures Office, and make modifications to the preliminary foundation design as needed to accom-modate the structural design needs provided by the Bridge and Structures Office. It is possible that muchof what was included in the preliminary foundation design memorandum may be copied into the finalgeotechnical report, if no design changes are needed. This report will also be used for publication anddistribution to potential bidders.

Final Structural Modeling and PS&E Development — In this phase, the Bridge and Structures Officemakes any adjustments needed to their structural model to accommodate any changes made to thegeotechnical foundation recommendations as transmitted in the final geotechnical report. From this,the bridge design and final PS&E would be completed.



July 2000 9.9-3

Overall Design Process for LRFD Foundation DesignFigure 9.9.1-1

Bridge and Structures Office(BO) requests conceptual

foundation recommendationsfrom Geotechnical Branch (GB)

BO obtains site data fromregion, develops draft

preliminary bridge plan,and provides initial foundation

needs input to GB

BO performs structural analysisand modeling, and providesfeedback to GB regarding

foundation loads, type, size,depth, and configuration needed

for structural purposes

GB provides preliminaryfoundation designrecommendations

GB performs final geotechnicaldesign as needed and providesfinal geotechnical report for

the structure

▼

▼▼

▼

▼

▼

GB provides conceptualfoundation recommendations

to BO

BO performs final structural modeling (if necessary)and develops final PS&E for structure

▼



9.9-4 July 2000

9.9.2 Definitions and Geometry

Use Figure 9.9.2-1 below to provide a common basis of understanding for loading locations and direc-tions for substructure design. This figure also describes the geometric data required for abutment andsubstructure design. Note that for shaft and some pile foundation designs, the shaft or pile may form thecolumn as well as the foundation element, thereby eliminating the footing element shown in the figure.

Template for Foundation Site Data and Loading Direction DefinitionsFigure 9.9.2-1

Note that in the guidelines which follow, where reference is made to an article or table in the AASHTOspecifications, the article can be found in the 1998 AASHTO LRFD specifications, Second Edition,with Interims.



July 2000 9.9-5

Load Combinations and Load Factors (from AASHTO LRFD Specifications Table 3.4.1-1)Table 9.2.3-1

Load DC LL WA WS WL FR TU TG SE Use One of TheseCombination DD IM CR at a Time

DW CE SH EQ IC CT CVEH BR ELEV PL

Limit State ES LS

Strength-I γp 1.75 1.00 – – 1.00 0.50/1.20 γTG

γSE

– – – –

Strength-II γp 1.35 1.00 – – 1.00 0.50/1.20 γTG

γSE

– – – –

Strength-III γp – 1.00 1.40 – 1.00 0.50/1.20 γTG

γSE

– – – –

Strength-IVEH, EV, ES, DW γp – 1.00 – – 1.00 0.50/1.20 – – – – – –DC only 1.5

Strength-V γp 1.35 1.00 0.40 0.40 1.00 0.50/1.20 γTG

γSE

– – – –

Extreme Event-I γp γEQ

1.00 – – 1.00 – – – 1.00 – – –

Extreme Event-II γp 0.50 1.00 – – 1.00 – – – – 1.00 1.00 1.00

Service-I 1.00 1.00 1.00 0.30 0.30 1.00 0.50/1.20 γTG

γSE

– – – –

Service-II 1.00 1.30 1.00 – – 1.00 0.50/1.20 – – – – – –

Service-III 1.00 0.80 1.00 – – 1.00 0.50/1.20 γTG

γSE

– – – –

Fatigue-LL, IMand CE only – 0.75 – – – – – – – – – – –

9.9.3 Load Factors

The load combinations and factors to be used for foundation design are provided in Table 9.9.3-1 andTable 9.9.3-2. These have been adapted from Table 3.4.1-2 of the 1998 AASHTO LRFD specifications,Second Edition and have been reproduced from the AASHTO LRFD Bridge Design Specifications. Notethat these tables are reproduced from the AASHTO specifications in their entirety for convenience only.Consult the most recent publication of the AASHTO LRFD Bridge Design Specifications to determinethe current load factors for design, with the exception of load factors which are identified herein asspecific to WSDOT practice.



9.9-6 July 2000

Load Factors for Permanent Loads, γp(Adapted from Table 3.4.1-2 of the AASHTO LRFD Specifications, but modified as shown below)

Table 9.9.3-2

Load Factor

Type of Load Maximum Minimum

DC: Components and Attachments 1.25 0.9

DD: Downdrag 1.00* 1.00*

DW: Wearing Surfaces and Utilities 1.50 0.65

EH: Horizontal Earth Pressure• Active 1.50 0.90• At-Rest 1.35 0.90

EV: Vertical Earth Pressure• Retaining Structure 1.35 1.00• Rigid Buried Structure 1.30 0.90• Rigid Frames 1.35 0.90• Flexible Buried Structures other than

Metal Box Culverts 1.95 0.90• Flexible Metal Box Culverts 1.50 0.90

ES: Earth Surcharge .50 0.75

*DD was reduced to 1.00 to reflect current WSDOT and national practice.

Permanent Load FactorsDC = dead load of structural components and non structural attachmentsDD = downdragDW = dead load of wearing services and utilitiesEH = horizontal earth pressure loadEV = vertical pressure from dead load of earth fillES = earth surcharge loadEL = accumulated locked-in force effects resulting from the construction processVarious Transient Load FactorsBR = vehicular braking forceCE = vehicular centrifugal forceCR = creepCT = vehicular collision forceCV = vessel collision forceEQ = earthquakeFR = frictionIC = ice loadIM = vehicular dynamic load allowanceLL = vehicular live load

LS = live load surchargePL = pedestrian live loadSE = settlementSH = shrinkageTG = temperature gradientTU = uniform temperatureWA = water load and stream pressureWL = wind on live loadWS = wind load on structure

The load factors γTG and γSE are to be determined on a project specific basis in accordance withArticles 3.4.1 and 3.12 of the AASHTO LRFD Specifications.



July 2000 9.9-7

9.9.4 LRFD Load Combinations, Basic Equation, and Characteristic Soil/Rock Properties

The controlling load combinations for WSDOT projects for Super and Substructure Design are as follows:

Strength I Relating to the normal vehicular useStrength III Relating to the bridge exposed to windStrength IV Relating to temperature fluctuations, creep, and shrinkageStrength V Relating to the normal vehicular use and windExtreme-Event I Relating to earthquakeService I Relating to normal operational use and wind

In general, for Extreme Event I, set γEQ, the earthquake load factor, equal to 0 (note that γEQ up to 0.5should be considered on a project specific basis to account for potential partial live loads during a seismicevent). For eccentrically loaded footings and abutment wall footings, use γEQ = 0.0 or 1.0, depending onthe maximum resultant force eccentricity allowed (see “Overturning Stability for Footings — Strengthand Extreme Event Limit States”).

A. LRFD Basic Equation

The basic equation for load and resistance factor design (LRFD) states that the loads multiplied byfactors to account for uncertainty, ductility, importance, and redundancy must be less than or equalto the available resistance multiplied by factors to account for variability and uncertainty per theAASHTO LRFD specifications. The basic equation, therefore, is as follows:

Σηiγi Qi ≤ φRn

ηi = Factor for ductility, redundancy, and importance of structureγi = Load factorQi = Load (i.e., dead load, live load, seismic load, etc.)φ = Resistance factorRn = Nominal or ultimate resistance

For typical WSDOT practice, ηi should be set equal to 1.0 for use of both minimum and maximumload factors.

B. Characteristic Soil/Rock Properties and Their Use in LRFD

Load and resistance factors are based on a combination of the following:

• design model uncertainty,

• soil/rock property uncertainty,

• unknown uncertainty inherited from allowable stress and load factor design practices includedin previous AASHTO design specifications.

Therefore, uncertainty in the soil parameters only amounts for a part of each of the load andresistance factors.



9.9-8 July 2000

Assume that the characteristic soil/rock properties used in conjunction with the load and resistancefactors provided herein are average values obtained from laboratory test results or from correlatedfield in-situ test results. Note that use of lower bound soil/rock properties could result in overlyconservative foundation designs. No specific guidance is available regarding the extent of subsurfacecharacterization and the number of soil/rock property tests required to justify use of the load andresistance factors provided herein. Geotechnical engineering judgment is required.

No adequate documentation exists regarding the derivation of load factors for soil loads to have anybasis for adjusting the load factors for site specific considerations, or for regional practice. However,there is some documentation available regarding the derivation of resistance factors for foundations.This makes it possible to adjust the resistance factors for site specific considerations and regionalpractices. See the Federal Highway Administration manual FHWA HI-98-032 “Load and ResistanceFactor Design (LRFD) for Highway Bridge Substructures,” 1998, for the necessary statistical infor-mation and procedures for making such an adjustment. Appendix A of this section has an exampleof resistance factor adjustment as applied to a pile foundation design. Adjustments to soil resistancefactors, where warranted, will be made by the Geotechnical Branch if adequate data is available todo so.



July 2000 9.9-9

9.9.5 Spread Footing Design

Figure 9.9.5-1 provides a flowchart which illustrates the design process and the interaction between thestructural geotechnical engineers needed for footing design.

Design Flowchart for Spread Footing DesignFigure 9.9.5-1

1(ST). Determine bridge geometry and pier locations

8(GT). Checknominal footingresistance at alllimit states, andoverall stability

in light ofnew footingdimensions,

depth, and loads

1(GT). Determine depth offooting based on geometry

and bearing material

▼

2(ST). Determine loads applied tofooting, including lateral earthpressure loads for abutments

▼

1(GT). Determine depth offooting for scour, if present (with

help of Hydraulic Engineer)

▼

3(GT). Determine soil propertiesfor foundation design, and resistance

factors in consideration of thesoil property uncertainty and themethod selected for calculating

nominal resistance

3(ST). Design the footingat the service limit state

▼

4(ST). Check the bearing pressure ofthe footing at the strength limit state

▼

5(ST). Check the eccentricity of thefooting at the strength limit state

▼

6(ST). Check the sliding resistance ofthe footing at the strength limit state

▼

7(ST). Check the bearing pressure ofthe footing at the extreme limit state

▼

8(ST). Check the eccentricity ofthe footing at the extreme limit state

▼

9(ST). Check sliding resistance ofthe footing at the extreme limit state

▼

10(ST). Design the footing (andwalls for abutment) according to theconcrete section of the Specification

▼

4(GT). Determine active, passive,and seismic earth pressure parameters

as needed for abutments

▼

5(GT). Determine nominal footingresistance at the strengthand extreme limit states

▼

6(ST). Determine nominal footingresistance at the service limit state

▼

7(GT). Check overall stability,determining max. feasible bearingload to maintain adequate stability

▼▼

▼

▼

GT: Geotechnical EngineerST: Bridge Engineer



9.9-10 July 2000

A. Loads and Load Factor Application to Spread Footings

Figures 9.9.5-2 and 9.9.5-3 provides definitions and locations of the forces and moments which acton structural footings. Table 9.9.5-1 identifies when to use maximum or minimum load factors forthe various modes of failure for the footing (sliding, overturning, bearing capacity) for each force.Note that the eccentricity used to calculate the bearing stress is referenced to point C, whereas theeccentricity used to evaluate overturning is referenced to point O. It is important to not change frommaximum to minimum load factors in consideration of the force location relative to the referencepoint used (“C” or “O”), as doing so will cause basic statics to no longer apply, and one will notget the same resultant location when the moments are summed at different reference points. Alsonote that the loads are factored after they are distributed to the foundation through structural analysisand modeling.

Definition and Location of Forces and Moments for Cantilever (or Overhanging) AbutmentsFigure 9.9.5-2



July 2000 9.9-11

Definition and Location of Forces and Moments for L-abutments and Interior FootingsFigure 9.9.5-3



9.9-12 July 2000

The variables shown above in Figures 9.9.4-1 and 9.9.4-2 are defined as follows:

DLv, LLv, EQv = vertical structural loads applied to footing/wall (dead load, transient load, EQ load,respectively)

τp or τt = structural static shear loads transmitted through bearing at wall top (parallel toabutment wall or transverse to bridge, respectively)

τn or τl = structural static shear loads transmitted through bearing at wall top (normal toabutment wall or longitudinal to bridge, respectively)

τEQp or τEQt = structural seismic shear loads transmitted through bearing at wall top (parallel toabutment wall or transverse to bridge, respectively)

τEQn or τEQl = structural seismic shear loads transmitted through bearing at wall top (normal toabutment wall or longitudinal to bridge, respectively)

Ws = weight of soil above abutment wall heel

Wtoe = weight of soil above footing toe

WC = weight of footing and column/wall

Ft = soil active force behind abutment wall (use at rest earth pressure if have anintegral abutment)

Fq = traffic surcharge force behind abutment wall

PAE = dynamic horizontal thrust due to seismic loading

PIR = soil and wall mass inertial force due to seismic loading

QEP = ultimate soil passive resistance (note: height of pressure distribution triangle isdetermined by the geotechnical engineer and is project specific)

Qτ = soil shear resistance along footing base at soil-concrete interface

sv = resultant vertical bearing stress at base of footing

R = resultant force at base of footing

eC = eccentricity calculated about point C (center of footing), to be used for bearingstress calculations

eO = eccentricity calculated about point O (toe of footing), to be used for overturningcalculations

B = footing width

L = footing length

q = traffic live load surcharge pressure



July 2000 9.9-13

Selection of Maximum or Minimum Spread Footing Foundation Load Factorsfor Various Modes of Failure for the Strength and Extreme Event Limit States

Table 9.9.5-1

Load Factor

Load Sliding Overturning, eo Bearing Stress (ec, sv)

DLv DCmin, DWmin DCmin, DWmin DCmax, DWmax

LLv Use transient load Use transient load Use transient loadfactor (e.g., LL) factor (e.g., LL) factor (e.g., LL)

τp, τt, τn τ1 Use DCmax, DWmax Use DCmax, DWmax Use DCmax, DWmaxfor causing forces, for causing forces, for causing forces,DCmin, DWmin for DCmin, DWmin for DCmin, DWmin forresisting forces resisting forces resisting forces

Ws, Wtoe EVmin EVmin EVmax

Wc DCmin DCmin DCmax

Ft EHmax EHmax EHmax

Fq LS LS LS

q Set = 0 Set = 0 Use transient loadfactor (e.g., LL)

Note that the dead load, DLv, as used herein typically includes the load due to structural componentsand non-structural attachments (i.e., DC), and the dead load of wearing surfaces and utilities (i.e., DW).The live load, LLv, as used herein for foundation design can include any of the transient loads identifiedpreviously except vehicular dynamic load allowance, IM, and loads due to earthquake, EQ.

B. Footing Bearing Stress and Capacity — Strength and Extreme Event Limit States

For geotechnical and structural design of eccentrically loaded footings on soil, calculate thebearing stress based on a uniform bearing pressure distribution using the Meyerhof approach.For geotechnical and structural design of eccentrically loaded spread footings on rock, calculatethe bearing stress based on a triangular or trapezoidal bearing pressure distribution.

The Meyerhof method is summarized as follows:

Step 1: Calculate eccentricity, ec, about Point C in Figure 9.9.5-2 or Figure 9.9.5-3, with the appliedloads already factored.

ec = (summation of factored moments acting on footing and wall)/(summation of factoredvertical forces acting on footing and wall)



9.9-14 July 2000

Step 2: Calculate the factored vertical stress based on a uniform pressure distribution acting on thebase of footing, σv as illustrated in Figure 9.9.5-2 or Figure 9.9.5-3. Note that this calculation methodapplies in both directions for biaxially loaded footings (see Article 10.6.3.1.5 in the AASHTO LRFDspecifications for guidance on biaxial loading).

σv = (summation of factored vertical forces acting on footing and wall per unit footinglength)/(B-2ec)

Use the appropriate maximum or minimum load factors as shown in Table 9.9.5-2 when calculatingsv. Note that B - 2ec is considered to be the effective footing width B′.

If a triangular distribution is used for the footing contact pressure (applies to footings on rock only):

σvmax = V/B ( 1+ 6 ec / B )

“V” is the sum of the factored vertical forces on the footing.

Step 3: Compare σv, or σvmax, which already has the load factors included, to the factored bearingcapacity of the soil (i.e., the ultimate bearing capacity for the soil/rock multiplied by an appropriateresistance factor). The factored bearing capacity (resistance) should be greater than or equal to thefactored bearing stress. That is:

σv < φbcqult

where, qult is the unfactored ultimate bearing capacity for the appropriate limit state and φbc is theresistance factor. Note that qult will be the same for the strength and extreme event limit states. Ingeneral, a resistance factor of 1.0 should be used for bearing capacity at the extreme event limit state.See Table 9.9.5-2 for resistance factors for the strength limit state.

Bearing capacity for the strength and extreme event limit states should be calculated considering theeffects of soil frictional and cohesive resistance, footing dimensions and shape, footing embedment,and slope of the ground in front of the footing. The Geotechnical Branch will calculate the footingbearing capacity using either the AASHTO LRFD specifications, Article 10.6.3.1, or other widelyaccepted methods provided in the literature. Load inclination factors will not, in general, be consid-ered in the determination of bearing capacity. The Geotechnical Branch may limit the ultimatebearing capacity based on the geotechnical engineering experience available for the givengeological formation.

C. Sliding Stability for Footings — Strength and Extreme Event Limit States

The factored sliding resistance is comprised of a frictional component (φτ Qτ) and a passive earthpressure component (φep Qep). The frictional component acts along the base of the footing, and thepassive component acts on the vertical face of the buried footing element.

Factored Sliding Resistance, QR = φτ Qτ + φep Qep

The Strength Limit State, φτ and φep are determined from Table 9.9.5-2. For the Extreme EventLimit State, φτ = 1.0 and φep = 1.0. If passive resistance in front of footing is not dependable due topotential for erosion, scour, or future excavation in front of footing, use φep = 0.0 for the strength andextreme event limit states, and for temperature/shrinkage loads. The Geotechnical Branch shouldbe contacted for assistance to determine if passive resistance should be considered for analysis ofsliding stability.



July 2000 9.9-15

Qτ = (V)tan δδ = friction angle between the footing base and the soilδ = tan φ for cast-in-place concrete against soilδ = (0.8)tan φ for precast concreteV = total vertical force on footingφ = angle of internal friction for soil

The factored sliding resistance should be greater than or equal to the factored horizontalapplied loads.

D. Overturning Stability for Footings — Strength and Extreme Event Limit States

Calculate the eccentricity about Point O in Figure 9.9.5-2 or Figure 9.9.5-3 to locate the resultantforce, R. Forces and moments resisting overturning are to be considered negative, and minimumload factors should be used (see Table 9.9.5-1). Forces and moments causing overturning are to beconsidered positive, and maximum load factors should be used for those forces (see Table 9.9.5-1).

For strength limit state, keep the resultant force at the base of the footing within the middle 1/2 of thefooting dimensions for soil and the middle 3/4 of the footing dimensions for rock. For extreme eventlimit state and with γEQ = 0, keep the resultant force at the base of footing within the middle 2/3 of thefooting dimensions for soil and rock. If γEQ = 1.0, keep the resultant force at the base of the footingwithin the middle 3/4 of the footing dimensions for soil and rock. Note that for footings subjected tobiaxial loading, these eccentricity requirements apply in both directions.

E. Overall Stability for Footings — Service and Extreme Event Limit States

The Geotechnical branch will evaluate overall stability using modified Bishop, Janbu, Spencer,or other widely accepted slope stability analysis methods. Article 10.5.2 recommends that overallstability be evaluated at the Service I limit state (i.e., a load factor of 1.0) and a resistance factor,φos of 0.65 for slopes which support a structural element.

Available slope stability programs produce a single factor of safety, FS. The Geotechnical Branchwill continue its past practice of checking overall slope stability to insure that footings designed fora maximum bearing stress equal to the specified service limit state bearing capacity will not cause theslope stability factor of safety to fall below 1.5 (1.1 for extreme event limit state, with service loadsand a horizontal acceleration kh equal to 0.5 A). This practice will essentially produce the same resultas specified in Article 10.5.2 of the AASHTO LRFD Specifications.

The footing loads should be as specified for the Service I limit state for this analysis. If the footingis located on the slope such that the footing load increases slope stability, the Geotechnical Branchwill not establish a maximum footing load which is acceptable for insuring overall slope stability(see Figure 9.9.4-3 for example), but will instead ignore the presence of the footing to evaluateoverall stability.

Example Where Footing Contributes to Instability of Slope (left figure) vs.Example Where Footing Contributes to Stability of Slope (right figure)

Figure 9.9.5-4



9.9-16 July 2000

A resistance factor of 0.9, which is equivalent to a factor of safety of 1.1 in current WSDOT practice,should in general be used for overall stability for the extreme event limit state.

F. Resistance Factors for Footing Design — Strength Limit State

Resistance Factors for Strength Limit State for Shallow Foundations(adapted from Table 10.5.5-1 of the AASHTO LRFD Specifications)

Table 9.9.5-2

Type of ResistanceResistance Method/Soil/Condition Factor

Bearing Capacity φbc Sand- Semi-empirical procedures using SPT data 0.45- Semi-empirical procedure using CPT data 0.55- Rational Method

using φ estimated from SPT data 0.35using φ estimated from CPT data 0.45

Clay- Semi-empirical procedure using CPT data 0.50- Rational Method

using shear resistance measured in lab tests 0.60using shear resistance measured in field vane tests 0.60using shear resistance estimated from CPT data 0.50

Rock- Semi-empirical procedure, Carter and Kulhawy (1988) 0.60

Plate Load Test 0.55

Sliding φτ Precast concrete placed on sand- using φ estimated from SPT data 0.90- using φ estimated from CPT data 0.90

Concrete cast-in-place on sand- using φ estimated from SPT data 0.80- using φ estimated from CPT data 0.80

Sliding on clay is controlled by the strength of the clay when theclay shear strength is less than 0.5 times the normal stress, and iscontrolled by the normal stress when the clay shear strength isgreater than 0.5 times the normal stress (see Figure 10.6.3.3-1 inAASHTO LRFD specifications, which is developed for the casein which there is at least 150 mm of compacted granular materialbelow the footing).

Clay (where shear resistance is less than 0.5 times normal pressure)- Using shear resistance measured in lab tests 0.85- Using shear resistance measured in field tests 0.85- Using shear resistance estimated from CPT data 0.80Clay (where the resistance is greater than 0.5 times normal pressure) 0.85

Soil on soil 1.00

φep Passive earth pressure component of sliding resistance 0.50



July 2000 9.9-17

G. Design of Footings at the Service Limit State

The service limit state bearing capacity, qserv, will be a settlement limited value (typically 1 inch,but may be greater for long spans, simple spans, or relatively flexible structures). The method usedto determine the service limit state bearing capacity will depend on the soil type. The GeotechnicalBranch will use the AASHTO specifications or an appropriate textbook to select a settlement estimat-ing method. The Meyerhof approach (see discussion under “Footing Bearing Stress and Capacity —Strength and Extreme Limit States”) should be used to calculate the footing bearing stress, except thatservice limit state load factors should be used. For immediate settlement (not time dependent), bothpermanent dead load and live load should be considered for sizing footings for the service limit state.For time dependent settlement (e.g., on clays), only the permanent dead loads should be considered.

σv < φqserv, where qserv is the unfactored service limit state bearing capacity and φ is the resistancefactor. In general, a resistance factor of 1.0 should be applied to the bearing capacity at the servicelimit state.

Design of a footing for overall slope stability at the service limit state was covered previously.

H. What the Geotechnical Branch Will Provide to the Bridge Office for LRFD Footing Design

To evaluate bearing capacity, the Geotechnical Branch will provide qult and qserv for various effectivefooting widths likely to be used, and resistance factors for each limit state. The amount of settlementon which qserv is based will be stated. The calculations will assume that qult and qserv are uniformloads applied over effective footing dimensions B’ and L’ (i.e., effective footing width and length((B or L) - 2e) as determined using the Meyerhof method, at least for soil. For footings on rock, thecalculations will assume that qult and qserv are peak loads and that the stress distribution is triangularor trapezoidal rather than uniform. The Geotechnical Branch will also provide embedment depthrequirements or footing elevations to obtain the recommended bearing capacity.

To evaluate sliding stability and eccentricity, the Geotechnical Branch will provide the followinginformation:

• resistance factors for both the strength and extreme event limit states for calculating Qt and Qep

• soil parameters of φ, Kp, γ and depth of soil in front of footing to ignore in calculating Qep

• φ, Ka, and γ for calculating active force behind footing (abutments only)

To evaluate soil response and development of forces in foundations for the extreme event limit state,the Geotechnical Branch will provide foundation soil/rock shear modulus and Poissons ratio (G andµ). These values will typically be determined for shear strain levels of 0.02 to 0.2%, which span thestrain levels for typical large magnitude earthquakes.

The Geotechnical Branch will evaluate overall stability and provide the maximum (unfactored)footing load which can be applied to the design slope and still maintain an acceptable safety factor(typically 1.5 for the strength and 1.1 for the extreme event limit states, which is the inverse of theresistance factor). A uniform bearing stress as calculated by the Meyerhof method will be assumedfor this analysis. An example presentation of the LRFD footing design recommendations to beprovided by the Geotechnical Branch is as shown in Tables 9.9.5-3 and 9.9.5-4, and Figure 9.9.5-5.



9.9-18 July 2000

Example Presentation of Soil Design Parameters for Sliding and Eccentricity CalculationsTable 9.9.5-3

Parameter Abutment Piers Interior Piers

Soil Unit Weight, γ (soil above footing base level) X X

Soil Friction Angle, φ (soil above footing base level) X X

Active Earth Pressure Coefficient, Ka X X

Passive Earth Pressure Coefficient, Kp X X

Coefficient of Sliding, Tan δ X X

Example Presentation of Resistance Factors for Footing DesignTable 9.9.5-4

Resistance Factor, φ

Shear Resistance Passive PressureLimit State Bearing to Sliding Resistance to Sliding

Strength X X X

Service X

Extreme Event X X X

Example Presentation of Bearing Capacity RecommendationsFigure 9.9.5-5

Effective Footing Width, B’

Service limit state at ___ mm

of settlement

Unfactored strength and extreme

event limit states

Bea

ring

Cap

acit

y



July 2000 9.9-19

9.9.6 Loads and Load Factor Application to Deep Foundation Design

Figures 9.9.6-1 and 9.9.6-2 provide definitions and typical locations of the forces and moments whichact on deep foundations. Table 9.9.6-1 identifies when to use maximum or minimum load factors for thevarious modes of failure for the shaft or pile (bearing capacity, uplift, and lateral loading) for each force.

Definition and Location of Forces and Moments for Integral Shaft Column or Pile BentFigure 9.9.6-1



9.9-20 July 2000

Definition and Location of Forces and Moments for Pile or Shaft Supported FootingFigure 9.9.6-2

where,

qp

= ultimate end bearing resistance at base of shaft or pile (unit resistance)q

s= ultimate side resistance on shaft or pile (unit resistance)

qDD

= ultimate down drag load on shaft or pile (unit load)Q

DD= ultimate down drag load on shaft or pile (total load)

Wnet

= unit weight of concrete in shaft minus unit weight of soil times the shaft volume below thegroundline (may include part of the column if the top of the shaft is deep due to scour or forother reasons

Mp or M

t= structural static moments applied to footing, calculated at bottom of column (parallel or

transverse to pier orientation, respectively)M

n or M

l= structural static moments applied to footing, calculated at bottom of column (normal or

longitudinal to bridge, respectively)M

EQp or M

EQt= structural seismic moments applied to footing, calculated at bottom of column (parallel or

transverse to pier orientation, respectively)M

EQn or M

EQl= structural seismic moments applied to footing, calculated at bottom of column (normal or

longitudinal to bridge, respectively)

All other forces are as defined for Figures 9.9.5-2 and 9.9.5-4 for footings.



July 2000 9.9-21

Selection of Maximum or Minimum Deep Foundation Load Factorsfor Various Modes of Failure for the Strength Limit State

Table 9.9.6-1

Load Factor

Load Bearing Stress (ec, s

v) Uplift *Lateral Loading

DLv DCmax, DWmax DCmin, DWmin DCmax, DWmax

LLv Use transient load Use transient load Use transient loadfactor (e.g., LL) factor (e.g., LL) factor (e.g., LL)

tp, tt, tn t1 Use DCmax, DWmax for Use DCmax, DWmax for DCmax, DWmaxcausing forces, DCmin, causing forcesDWmin for resisting forces

Mp, Mt, Mn, M1 Use DCmax, DWmax for Use DCmax, DWmax for Use DCmax, DWmax forcausing moments, causing moments causing momentsDCmin, DWmin forresisting moments

Ws, W

toeEVmax EVmin EVmax

Wnet

DCmax DCmin N/A

QDD

DDmax Treat as resistance, N/Aand use appropriateresistance factor

Ft

EHmax Use EHmax if causes uplift EHmax

Fq LS Use LS if Fq causes uplift LS

q Use transient load Set = 0 Use transient loadfactor (e.g., LL) factor (e.g., LL)

Use unfactored loads to get force distribution in structure, then factor the resulting forces for final structuraldesign. All forces and load factors are as defined previously.



9.9-22 July 2000

9.9.7 Drilled Shaft Design

Figure 9.9.7-1 provides a flowchart which illustrates the design process and the interaction between thestructural and geotechnical engineers needed for shaft design.

Design Flowchart for Shaft Foundation DesignFigure 9.9.7-1

1(GT). Determine depth ofscour, if present (with help

of Hydraulic Engineer)

▼

2(ST). Determine loads applied tofoundation top, including lateral earthpressure loads for abutments, through

structural analysis and modeling aswell as shaft lateral load analysis

▼2(GT). Determine soil propertiesfor foundation design, liquefactionpotential, and resistance factors inconsideration of the soil property

uncertainty and the method selectedfor calculating nominal resistance



3(ST). Determine depth, diameter,and nominal shaft resistance needed

to support the unfactored appliedloads at the strength limit state

▼3(ST). Determine depth, diameter,and nominal shaft resistance needed

to support the unfactored appliedloads at the strength limit state

▼

5(ST). Reevaluate foundationstiffnesses, and rerun structural

modeling to get new load distributionfor foundations. Reiterate if loadsfrom lateral shaft analysis do notmatch foundation top loads fromstructural modeling within 5%

▼6(ST). Factor the loads, and adjust

the shaft size or depth as neededto resist applied factor loads,

both lateral and vertical

▼7(ST). Check the minimum shaftdepth required to resist factored

uplift loads and to resist lateral loadswithin acceptable deformations

▼8(ST). Design the foundation

(and walls for abutment)

▼

9(ST). Develop contractspecifications

▼

4(GT). Determine nominal singleshaft resistance at the strength andextreme limit states as function ofdepth, for likely shaft diameters

needed, considering shaftconstructability

▼

5(GT). Estimate downdragloads, if present

▼

6(ST). Provide estimate of settlementlimited resistance (service state)

for shaft/shaft group, or foundationdepth required to precludeunacceptable settlement

▼

7(GT). Determine nominaluplift resistance for shafts

as function of depth

▼


9(GT). Evaluatethe shaft/shaft

group for nominalresistance at the

strength andextreme limit states,

and settlement/resistance at the

service limit state

▼

1(ST). Determine bridge geometry, pierlocations, column diameter, and foundation top

10(GT). Verifyestimated tip

elevation and shaftnominal resistancefrom Step 6(ST),

as well as thespecified tip

elevation from thegreatest depth

required to meetuplift, lateral load,and serviceability

requirements;if significantly

different than whatwas provided inStep 6(ST), havestructural modeland foundation

design reevaluated

▼

▼

8(GT). Determine P-Y curveparameters for shaftlateral load analysis

▼

▼

▼▼



July 2000 9.9-23

A. Drilled Shaft Capacity — Strength and Extreme Event Limit States

The factored capacity must be greater than the total factored vertical load applied to the shaft.

Factored capacity, QR = φqp Qp + φqs Qs (strength and extreme event limit states)

where,Qp = qp

ApQs = qs

AsAp = end bearing areaAs = side area

The unit shaft end bearing and skin friction resistance will be determined by the Geotechnical Branchusing an appropriate static analysis method, such as provided in the AASHTO LRFD specifications,Article 10.8.3, or determined from load test results. φqp and φqs are determined from Table 9.9.7-1 forstrength limit state conditions. φqp and φqs are equal to 0.90 to 1.0 for the extreme event limit state,depending on the confidence in the soil parameters (typically, a resistance factor of 0.9 for φqp willtypically be used where a column is supported by a single shaft). Qp and Qs are the same for both thestrength and extreme event limit states.

Note that Qs is a total nominal resistance. The AASHTO LRFD specifications treats this net shaftweight, which is the weight of the average minus the weight of the soil volume removed to constructthe shaft, as a dead load, in which a load factor of 1.25 is applied. Past WSDOT practice has been tosubtract the net shaft weight directly from the shaft capacity. To correctly apply the AASHTO LRFDspecifications, this past practice will not be used. Therefore, for LRFD, the structural designer mustcalculate the net shaft weight (typically, a unit net weight of 50 pcf is sufficiently conservative) andadd that net weight to the applied foundation dead load.

Articles 10.8.3.3.2 and 10.8.3.4.3 in the current AASHTO specifications require Qp to be reduced forshaft diameters greater than 1.91 m (6.25 ft) in clay and 1.27 m (4.17 ft) in sand, respectively. Sincethe intent of this correction is to crudely account for settlement, this correction for shaft diametershould not be used if a more detailed analysis of settlement is conducted (see “Service Limit StateDesign for Drilled Shafts”). Furthermore, it should be noted that qp as determined in Article10.8.3.4.3 of the AASHTO LRFD specifications, even without this settlement correction factor forshaft diameter, is to some extent settlement limited for shafts in sand and is not a true ultimate value.The reason for this is that a true bearing capacity failure is typically not observed for shafts in sand,but instead deformation simply continues to increase with load. Therefore, the transition from astrength or extreme event limit state to a serviceability limit state is not well defined for shafts insand. This issue will be evaluated on a case by case basis by the Geotechnical Branch when provid-ing shaft capacity information for all limit states.

If downdrag exists, the downdrag force QDD (qDD As) shall be considered as a load rather than anegative resistance for shaft capacity calculations. The downdrag force QDD will be determined bythe Geotechnical Branch using an appropriate static shaft skin friction analysis method (seeAASHTO LRFD Article 10.8.3.3.1 for a method which can be used). Per Table 9.9.3-2, use a loadfactor applied to the downdrag force of 1.0. This factored downdrag force, in combination with theother factored applied loads, should be less than or equal to the factored strength and service limitstate resistances.



9.9-24 July 2000

Transient loads should not be considered when downdrag forces are included in the factored loadapplied to the shaft. Shaft skin friction in the downdrag zone should not be included in the shaftcapacity. If downdrag forces are induced by settlement due to liquefaction, downdrag forces shall beconsidered in the extreme event limit state design of the shaft. Note that the downdrag force duringliquefaction may be different than the downdrag force which is applicable during the strength andserviceability limit states, as liquefaction can cause the strength of the soil to change. The downdragforces calculated for static conditions should not be combined with the downdrag forces resultingfrom liquefaction when evaluating the extreme event limit state.

B. Uplift for Drilled Shafts

Factored uplift capacity, Quf = φup qup As = φup Qup

where, qup = ultimate unit uplift resistance, φup is as determined from Table 9.9.7-1 for strength limitstate conditions, and Qup is the unfactored ultimate uplift capacity.

The unit uplift resistance, qup is usually set equal to the unit side friction resistance, qs, for LRFDfoundation design, as the resistance factors for uplift in Table 9.9.7-1 already account for the poten-tial for side resistance in uplift being less than the side resistance in compression. If downdrag islikely to occur, either due to long-term settlement or due to liquefaction, the skin friction causingdowndrag is considered to be fully available to resist uplift forces. However, the downdrag force isnot subtracted from the uplift force.

C. Lateral Load Analysis for Drilled Shafts

In general, P-Y curves are used for lateral load analysis in the bridge design model to iterativelymatch deflections and load distributions between the various bridge components, considering thesoil response, to insure stability of the bridge. The maximum lateral deflection which is consideredacceptable may vary from structure to structure. Even though deflections are calculated, service limitstate load groups are usually not used for this analysis.

In general, only the extreme event load groups are used for lateral load analysis, and a φlat of 1.0 isused. However, strength limit state load groups are sometimes used for this analysis. For the strengthlimit state, a resistance factor of 1.0 is recommended at this time. Note that in some cases the depthrequired for shaft fixity based on lateral load analysis may control the shaft depth required rather thanbearing capacity or uplift; for example where soft or liquefiable soils are present.

Normally, both static and dynamic P-Y curve parameters are provided in the Geotechnical Report.The static parameters represent the soil behavior for short-term transient loads such as wind, ice,temperature, and vessel impact. For earthquake loads, the dynamic and static P-Y curve parameterswill be the same if the soils present have a stiffness which does not degrade with time during shaking,such as would occur during liquefaction.

If liquefaction can occur, two P-Y analyses for the extreme event limit state should be conducted,one analysis using the static P-Y parameters and the other analysis using the dynamic P-Y param-eters. The intent here is to bracket the structure response. Often, the highest acceleration the bridgesees is in the first cycles of the earthquake, and liquefaction tends to occur toward the middle orend of the earthquake. Therefore, early in the earthquake, loads are high, soil-structure stiffness ishigh, and deflections are low. Later in the earthquake, the soil-structure stiffness is lower anddeflections higher.

D. Group Effects for Bearing Capacity

AASHTO Article 10.8.3.9 applies.



July 2000 9.9-25

Resistance Factors for Drilled Shaft DesignResistance Factors for Strength Limit State for Drilled Shaft Foundations

(adapted from Table 10.5.5-3 in AASHTO)Table 9.9.7-1

Type of ResistanceResistance Method/Soil/Condition Factor

Bearing Capacity φqp Base Resistance in Clay:of Single Drilled - Total stress (Reese and O’Niel, 1988) 0.55Shafts Base Resistance in Sand:

- SPT method (Reese and O’Niel, 1988) *0.50

Base Resistance in Rock:- Canadian Geotechnical Society (1985) 0.50

φqs Side Resistance in Clay:- α-method (Reese and O’Niel, 1988) 0.65

Side Resistance in Sand:- β-method (Reese and O’Niel, 1988) *0.65

Side Resistance in Rock:- Carter and Kulhawy (1988) 0.55- Horvath and Kinney (1979) 0.65

Side and Base Resistance:- Load test +0.70-0.80

Uplift Resistance φup Clay:of Single Drilled - α-method (Reese and O’Niel, 1988) 0.55Shafts - Belled shafts (Reese and O’Niel, 1988) 0.50

Sand:- β-method (Reese and O’Niel, 1988) *0.55

Rock:- Carter and Kulhawy (1988) 0.45- Horvath and Kinney (1979) 0.55

Load Test: +0.70-0.80

Group Bearing φqgr Clay: 0.65Capacity (blockfailure)

Group Uplift φupgr Clay: 0.55

Resistance Sand: 0.55

Lateral Resistance φlat Clay, sand, and rock: *1.0of Shafts andShaft Groups

*The AASHTO specifications currently do not provide bearing capacity resistance factors in sand and factors for lateral loading. For φlat

,the value used will depend on the confidence in the soil parameters. These resistance factors should be considered to be tentative untiladditional research and comparative designs are accomplished.+For shaft load tests, the number of load tests required will depend on the uniformity of the soil/rock conditions and whether or not a welldefined bearing stratum is present. Assuming that an appropriate number of load tests are conducted, use the largest resistance factor in thespecified range for very uniform conditions or for a well defined and highly resistant bearing stratum, and use the lowest resistance factor

in the range for nonuniform conditions or a poorly defined bearing stratum.



9.9-26 July 2000

E. Group Effects for Uplift

AASHTO Article 10.7.3.7.3 applies.

F. Group Effects for Lateral Loads

P-Y curves are usually derived considering only a single foundation element. To account for groupeffects, multiply the modulus of subgrade reaction, k, by the appropriate efficiency factor as providedin Table 9.9.7-2, or as specified in the Geotechnical Report. Loading direction and spacing are asdefined in Figure 9.9.7-2.

Group Efficiency Reduction Factors for Foundation Element Groups Subjected to Lateral LoadTable 9.9.7-2

Foundation Element Efficiency Reduction Efficiency ReductionSpacing, Center-to- Factor for Multiple Row Factor for Single Row

Center, in Direction of Groups, or in Direction Groups for Loading DirectionApplied Loading Parallel to Single Row Perpendicular to Row

8b 1.0 1.0

6b 0.9 1.0

5b 0.8 1.0

4b 0.65 0.9

3b 0.5 0.8

2b 0.4 0.6

Definition of Loading Direction and Spacing for Group EffectsFigure 9.9.7-2



July 2000 9.9-27

The soil strength parameters are also reduced to account for group effects. For cohesive soils,multiply the soil cohesion, C, directly by the appropriate group reduction factor from Table 9.9.7-2 oras specified in the Geotechnical Report. For granular soils (sands, gravels), multiply the normalizedresistance identified in Figure 9.9.7-3 by the appropriate group reduction factor to determine thereduced friction angle. Use the following steps to accomplish this:

1. Determine the normalized resistance for each soil layer at the friction angle for that soil layerprovided in the Geotechnical Report (e.g., for φ = 36o, normalized resistance = 61).

2. Multiply the normalized resistance determined in Step 1 by the group efficiency reduction factorbased on the foundation element spacing (e.g., if the spacing is 3b, the reduction factor is 0.5 andthe normalized resistance accounting for group effects is 32).

3. Based on the reduced normalized resistance, determine the soil friction angle accounting forgroup effects (e.g., at a normalized resistance of 32, the soil friction angle is 31o).

4. Use this reduced φ, in combination with the reduced modulus of subgrade reaction, k, to deter-mine the P-Y curve accounting for group effects.

Normalized Resistance as a Function of Soil Friction Angle for Lateral Capacity DeterminationFigure 9.9.7-3

where,

Normalized Resistance = Ps/bγX = Ka(tan8B - 1) + Ko(tan4B)(tanφ)

φ = Soil friction angle

Ps = Soil resistance on section of foundation element

b = Foundation element diameter

γ = Soil unit weight

X = Depth to section of foundation element

B = 45o + φ/2

Ka = tan2 (45o-φ/2)

Ko = 1 - sin φ



9.9-28 July 2000

G. Service Limit State Design for Drilled Shafts

The service limit state shaft capacity, Qserv, will be a settlement limited value (typically 0.5 to 1 inch,but may be greater for long spans, simple spans, or relatively flexible structures). See the AASHTOLRFD specifications, Article 10.8.2.3, which provides the method published by Reese and O’Neill,1988, to estimate the side friction and end bearing mobilized for a specified total settlement for asingle shaft. Typically, the Geotechnical Branch will be using this method to estimate verticaldeflection of shafts, where applicable. For immediate settlement (not time dependent), which is thetype of settlement addressed by the Reese and O’Neill method, both permanent dead load and liveload should be considered.

For time dependent settlement (e.g., on clays for analysis of shaft groups which are primarilyfrictional in nature), only the permanent dead loads should be considered. Note that this methodwas developed for predicting immediate settlement for shafts in clay or in sand. This method maybe overly conservative for the very dense glacially consolidated soils often encountered in WSDOTshaft installations, since this method was based on settlement limited behavior in soils which were notas dense as state of Washington glacially overridden soils. The Geotechnical Branch will evaluate thesettlement potential of drilled shafts considering the amount of skin friction and end bearingmobilized for service limit state design.

Factored bearing capacity at a specified settlement, QRserv = φservp Qpserv + φservs Qsserv (service limitstate), where,

Qpserv = qpserv Ap

Qsserv = qsserv As

qpserv = end bearing resistance at base of shaft (unit resistance) for a specified settlement

qsser = side resistance on shaft (unit resistance) for a specified settlement

Ap = end bearing area,

As = side area,

In general, a resistance factor of 1.0 should be used for shaft capacity at the service limit state(φservb and φservs).

H. What Geotechnical Branch Will Provide to Bridge Office for LRFD Shaft Design

To evaluate bearing capacity, the Geotechnical Branch will provide as a function of depth and atvarious shaft diameters the unfactored ultimate bearing capacity for end bearing, Qp, and side friction,Qs, used to calculate QR, for strength and extreme event limit state calculations (see example figuresbelow). For the service limit state, the unfactored bearing capacity at a specified settlement, typically0.5 or 1.0 inch, Qpserv (mobilized end bearing) and Qsserv (mobilized side friction) will be provided asa function of depth and shaft diameter. See Figure 9.9.7-4 for an example of the capacity informationthat would be provided. A similar set of curves, for the strength and extreme event limit states, willalso be provided for uplift capacity, Qup. Qup will be reduced to account for scour or liquefaction/weakening.



July 2000 9.9-29

In most cases, Qult and Qup for the strength, extreme event II and extreme event I limit states will bethe same, as loss of skin friction due to liquefaction downdrag will be taken into account separately.However, if soils are present which weaken but do not liquefy during an earthquake, a separate curvefor the extreme event I limit state may be needed.

Note that the side friction bearing capacities provided in these figures will be a total nominalresistance, in that the net weight of the shaft below the final groundline will not already be subtractedout of the side friction capacity. Resistance factors for bearing capacity for all limit states will also beprovided, as illustrated in Table 9.9.7-3.

If downdrag is an issue, the ultimate downdrag load, QDD, as a function of shaft diameter will beprovided, as well as the depth zone of the shaft which is affected by downdrag, the downdrag loadfactor, and the cause of the downdrag (settlement due to vertical stress increase, liquefaction, etc.).If liquefaction occurs, the reduction in side friction resistance, Qs, to be subtracted off of the ultimateside friction capacity plots will be provided. See example tables below.

Example Presentation of Resistance Factors for Shaft DesignTable 9.9.7-3

Resistance Factor

Limit State Skin Friction, Qs End bearing, Qp Uplift, Qup

Strength X X X

Service X X

Extreme Event X X X

If lateral loads imposed by special soil loading conditions such as landslide forces are present, theultimate lateral soil force or stress distribution, and the load factors to be applied to that force orstress, will be provided.

The Geotechnical Branch will also provide group reduction factors for bearing capacity and uplift ifnecessary, as well as the associated resistance factors.

The Geotechnical Branch will continue to provide P-Y curve data as a function of depth as has beendone in the past. Resistance factors for lateral load analysis will not be provided, as the lateral loadresistance factors will typically be 1.0.



9.9-30 July 2000

Example Presentation of Downdrag LoadsTable 9.9.7-4

QDDs, Static Conditions QDDliq Due to Liquefaction

Pier No. Shaft Dia = __ Shaft Dia = __ Shaft Dia = __ Shaft Dia = __

X X X X X

X X X X X

X X X X X

Example Presentation of Skin Friction Loss Due to Downdrag or ScourTable 9.9.7-5

Qs Loss to be Applied to Figure 9.9.6-3 Qs Loss to be Applied to Figure 9.9.6-3Due to Static Downdrag or Scour Due to Liquefaction Downdrag

for Strength Limit Qult for Extreme Event Limit Qult

Pier No. Shaft Dia = __ Shaft Dia = __ Shaft Dia = __ Shaft Dia = __

X X X X X

X X X X X

X X X X X



July 2000 9.9-31

9.9.8 Pile Foundation Design

The objective of pile foundation design is to determine the following:

• pile capacity,

• pile size,

• pile type,

• size of the pile group required to resist the structural loads,

• estimated pile quantity needed,

• minimum tip elevation required, and

• driveability of the piles to meet the design requirements.

The pile foundation design should also include characterization of the pile foundation for purposes ofmodeling the overall structure, especially for seismic design.

Qs (unfactored) Qb (unfactored)

Strength and

Extreme

Limit States Strength and

Extreme

Limit States

Service Limit

State at ___

of

Service Limit

State at ___

of

Shaft Diameter = ___ Shaft Diameter = ___

Ele

vati

on o

r D

epth

Ele

vati

on o

r D

epth

Typical Shaft Total Bearing Capacity Plots (All Limit States)Figure 9.9.7-4

Service LimitState at ___ (in.)of Settlement

(a separate curvemay be needed forthe extreme event Ilimit state in somecases)

Service LimitState at ___ (in.)of Settlement

Qp



9.9-32 July 2000

Figure 9.9.8-1 provides a flowchart which illustrates the design process and the interaction between thestructural and geotechnical engineers needed for pile foundation design.

Design Flowchart for Pile Foundation DesignFigure 9.9.8-1

1(GT). Determine depth ofscour, if present (with help

of Hydraulic Engineer)

▼

2(ST). Determine loads applied tofoundation top, including lateral earthpressure loads for abutments, through

structural analysis and modeling aswell as pile lateral load analysis

▼2(GT). Determine soil propertiesfor foundation design, liquefactionpotential, and resistance factors inconsideration of the soil property

uncertainty and the method selectedfor calculating nominal resistance



3(ST). Determine the number of pilesrequired to support the unfactoredapplied loads at the strength limitstate, and their estimated depth

▼3(ST). Determine the number of piles

required to support the unfactoredapplied loads at the extreme event

limit state, and their estimated depth

▼

5(ST). Reevaluate foundationstiffnesses, and rerun structural

modeling to get new load distributionfor foundations. Reiterate if loadsfrom lateral pile analysis do notmatch foundation top loads fromstructural modeling within 5%

▼6(ST). Factor the loads, and adjust

size of pile group or the pile capacitiesand estimated depths as needed to

resist applied factored loads

▼7(ST). Check the minimum piledepth required to resist factored

uplift loads and to resist lateral loadswithin acceptable deformations

▼8(ST). Design the foundation

(and walls for abutment)

▼

9(ST). Develop contract specifications,obtaining pile quantities from estimated

pile depths, minimum pile capacityrequired, minimum tip elevations, and

overdriving required from design

▼

4(GT). Select best pile types, anddetermine nominal single pile

resistance at the strength and extremelimit states as function of depth,

estimating pile sizes likely needed,and establishing maximum

acceptable pile nominal resistance

▼

5(GT). Estimate downdragloads, if present

▼

6(ST). Provide estimate of settlementfor pile/pile group, or foundation

depth required to precludeunacceptable settlement

▼

7(GT). Determine nominaluplift resistance for piles

as function of depth

▼


9(GT). Evaluatethe pile group fornominal resistanceat the strength and

extreme limit states,and settlement/resistance at the

service limit state

▼

1(ST). Determine bridge geometry,pier locations, and foundation top

10(GT). Verifyestimated tip

elevation and pilenominal resistancefrom Step 6(ST),

as well as minimumtip elevation fromthe greatest depthrequired to meet

uplift, lateral load,and serviceability

requirements

▼

▼

8(GT). Determine P-Y curveparameters for pilelateral load analysis

▼▼

▼▼

11(GT). Based onminimum tip

elevation and pilediameter needed,

determine need foroverdriving anddriveability of

pile as designed;if not driveable,reevaluate pile

foundation designand structural

model

▼



July 2000 9.9-33

A. Pile Type, Pile Size, Bearing Capacity, and Estimated Tip Elevation — Strength and ExtremeEvent Limit States

First, determine the feasible ultimate pile capacity, Qult, for the soil at the site, and determinethe desired pile type and diameter. This ultimate capacity should be unfactored and based onstatic capacity calculations or experience with a given soil deposit. See the Federal HighwayAdministration manual FHWA-HI-97-013 “Design and Construction of Driven pile Foundations,”1997, for examples of static analysis methods for piles.

The feasible ultimate pile capacity may also be controlled by the structural capacity of the pile,especially if the pile will be driven to a very hard bearing stratum (e.g., driven to refusal). Determinethe structural capacity of the pile per Article 10.7.4 in the AASHTO specifications. In lieu of moredetailed structural analysis, the general guidance on pile types, sizes, and ultimate capacities providedin Table 9.9.8-1 can be used to select pile sizes and types for analysis. The Geotechnical Branch mayalso limit the ultimate pile capacity for a given pile size and type driven to a given soil/rock bearingunit based on experience with the given soil/rock unit. The maximum capacity allowed in that givensoil/rock unit may be increased by the Geotechnical Branch per mutual agreement with the Bridgeand Structures Office if a pile load test is performed.

Typical Pile Types and Sizes for Various Ultimate Pile CapacitiesTable 9.9.8-1

Pile Type and Diameter, in in.

Ultimate Pile Closed End Steel *Precast,Capacity Pipe/Cast-in-Place Prestressedin tons Concrete Piles Concrete Piles Steel H-Piles Timber Piles

60 tons - - - See WSDOTStandard Specs.

120 tons - - - See WSDOTStandard Specs.

165 tons 12 in. 13 in. - -

210 tons 14 in. 16 in. 12 in. -

300 tons 18 in. 18 in. 14 in. -nonseismic areas

(Category A),24 in. seismic areas

(Category B,C, and D)

450 tons 24 in. Project Specific Project Specific -

*Precast, prestressed concrete piles are generally not used for highway bridges, but are more commonly used formarine work.



9.9-34 July 2000

Select the construction quality control method to be used (e.g., driving formula, wave equation,Pile Driving Analyzer, etc.), and the resistance factors associated with the selected method, φdyn.

Determine the total factored load to be applied to the pier in question (strength and extreme eventlimit states). Note that the actual distribution of that load to the piles will depend on the number ofpiles in the group as well as where they are located within the group geometry.

The factored load per pile, Loadp, is determined as follows:

Loadp = +

where,

Mi

= the moment at the base of the column resulting from the forces applied to the column(i.e., dead load, live load, seismic load, etc.)

C = the distance between the centroid of the pile group and the center of the pile underconsideration

I = moment of inertia of the pile group

N = number of piles in the pile group

Other variables are as defined previously.

Determine the number of piles required in the pile group such that the factored load in any pile inthe group is not greater than the factored resistance. Use the resistance factor for the constructionquality control method selected previously, that is, QR = φdyn x Qult. Qult is the feasible ultimatepile capacity.

Do not use the above method if the pile is being driven to a specified tip elevation and the pilecapacity is not being determined in the field using a driving criteria which is based on a pile penetra-tion resistance (i.e., any dynamic method). In this case use the resistance factor for the static analysismethod used to determine the pile capacity. In this case, QR = φqp Qp + φqs Qs (strength and extremeevent limit states). Check all limit states, and determine the pile group size using the limit state whichrequires the most piles for the specified ultimate capacity. Note that φdyn, φqp, and φqs are all equalto 0.9 to 1.0 for the extreme event limit state, depending on the confidence in the soil parameters(AASHTO specifications recommend that 1.0 be used). The pile weight will be neglected in mostcases, but if it is to be considered, it is to be treated as a load as is done for safts (see Section 9.9.7A).Qp and Qs are the same for both the strength and extreme event limit states.

If downdrag exists, the downdrag force QDD (qDD As) shall be considered as a load rather than anegative resistance for pile capacity calculations. The downdrag force QDD will be determined bythe Geotechnical Branch using an appropriate static pile skin friction analysis method (see FHWAmanual on the design of driven pile foundations mentioned previously).

Per Table 9.9.3-2, use a load factor applied to the downdrag force of 1.0. This factored downdragforce, in combination with the other factored applied loads, should be less than or equal to thefactored strength and service limit state resistances. Transient loads should not be consideredwhen downdrag forces are included in the factored load applied to the pile for service and strengthlimit state calculations. Pile skin friction in the downdrag zone should not be included in the pileultimate capacity.

ΣγiQi (ΣγiMi)c n I



July 2000 9.9-35

If downdrag forces are induced by settlement due to liquefaction, downdrag forces shall be consid-ered in the extreme event limit state design of the pile. Note that the downdrag force during lique-faction may be different than the downdrag force which is applicable during the strength andserviceability limit states, as liquefaction can cause the strength of the soil to change. The downdragforces calculated for static conditions should not be combined with the downdrag forces resultingfrom liquefaction when evaluating the extreme event limit state. Figure 9.9.8-2 illustrates howdowndrag loads and loss of resistance is to be handled. When downdrag occurs (see Figure 9.9.7-1),the ultimate pile capacity needed is determined as follows: Qult = Loadp/φdyn + QDD + Qsdd

For the strength and extreme event limit states, if the soil is characterized as cohesive, the pilegroup capacity should also be checked for the potential for a “block” failure. Article 10.7.3.10 in theAASHTO specifications applies. See Table 9.9.8-2 to determine the appropriate resistance factor forthe strength limit state. Use a resistance factor of 0.9 to 1.0 for the extreme event limit state. Comparethe factored loads for each limit state to the factored block resistance. If a block failure appears likely,increase the group size so that a block failure is prevented.

For estimating pile quantities, develop unfactored, ultimate pile capacity versus estimated depthcurves using a static analysis method (see Figure 9.9.8-2 for example). The Geotechnical Branchmay adjust the estimated depth for a given pile capacity based on experience with the soil/rockdeposit in question and professional judgment. Determine the estimated pile length, Dest., for thedesired ultimate capacity, Qult, from this pile capacity versus depth curve for the purpose ofestimating pile quantities. Make sure that Qult is greater than or equal to the factored load per piledivided by the appropriate resistance factor, that is: Qult ≥ Loadp/φdyn + QDD + Qsdd

For the construction specifications, use the estimated pile length determined as illustrated in Figure9.9.7-1 for the contract pile quantity, and use Qult (unfactored) for the pile capacity which is insertedinto the driving formula, wave equation, etc., to determine the penetration resistance required toaccept the pile.

Note: The estimated pile length will be reasonably accurate if the bias, λR, for the static analysismethod used to estimate pile lengths and the feasible ultimate pile capacity is approximately thesame as the bias, λR, for the dynamic analysis method used to determine the factored pile capacity.If the biases for the two methods are not the same, the estimated pile length could be in error for agiven level of risk. If the coefficients of variation for the two methods are also significantly differentfor the two methods, this could accentuate the possible error for a given level of risk.

For example, if the dynamic formula tends to predict an average capacity which is approximatelythe same as the capacity measured from a pile load test, but the static analysis method tends tounder-predict the pile capacity measured from a pile load test, the pile depth predicted using thestatic analysis method illustrated in Figure 9.9.8-2 is likely to be too deep. Note that this is not likelyto be an issue when driving the pile to a well defined very dense stratum such as glacially loaded tillor bedrock. This pile length prediction accuracy is mainly a concern for friction piles. Therefore,some engineering judgment based on experience may be needed to estimate pile quantities withreasonable accuracy.



9.9-36 July 2000

Example Ultimate Pile Capacity Versus Depth Curve for Estimating Pile LengthsFigure 9.9.8-2

QSdd

= skin friction which must be overcome during driving through downdrag/liquefaction/scour zone

+ QDD

= ultimate pile capacity needed to resist all applied axial loads per pile, including downdrag

Loadp = factored load per pile, not including downdrag

QDD

= downdrag load per pile

n = number of piles in pile group for pier

Dest.

= estimated pile length needed to obtain desired ultimate capacity

Loadp φdyn

Loadp φdyn

Loadp φdyn



July 2000 9.9-37

B. Determination of Minimum Pile Tip Elevations

Determine the minimum pile depth required to meet settlement, lateral deflection/capacity, anduplift requirements. This would become the minimum pile tip elevation requirement for the contractspecifications. Note that lateral loading and uplift requirements may influence (possibly increase) thenumber of piles required in the group if the capacity available at a reasonable minimum tip elevationis not adequate. This will depend on the soil conditions and the loading requirements. For example,if the upper soil is very soft or will liquefy, making the minimum tip elevation deeper is unlikely toimprove the lateral response of the piles enough to be adequate. Adding more piles to the group orusing a larger pile diameter to increase the pile stiffness may be the only solution.

The various analyses required to establish the minimum tip elevations needed (if minimum tipelevations are in fact needed), are as follows:

1. Uplift for Piles

For the strength and extreme limit states, for the pile group size and geometry alreadydetermined, calculate for the structure the uplift capacity per pile needed using factored loads.Calculate the uplift resistance available using static analysis methods and using resistance factorsappropriate for the static analysis method used, for both limit states. Do this as a function of piledepth. Therefore,

Factored uplift capacity, Quf

= φup

qup

As

= φup

Qup

where, qup

= ultimate unit uplift resistance, As is the pile side area, φ

up is as determined from

Table 9.9.7-2 for strength limit state conditions, and Qup

is the unfactored ultimate uplift capacity.

The unit uplift resistance, qup

is usually set equal to the unit side friction resistance, qs, for LRFD

foundation design, as the resistance factors for uplift in Table 9.9.7-2 already account for thepotential for side resistance in uplift being less than the side resistance in compression. Ifdowndrag is likely to occur, either due to long-term settlement or due to liquefaction, the skinfriction causing downdrag should be considered to be fully available to resist uplift forces.However, the downdrag force is not subtracted from the uplift force.

From these calculations, determine the depth required to obtain the required factored upliftcapacity.

2. Lateral Load Analysis for Piles

“Lateral Load Analysis for Drilled Shafts” applies.

3. Pile Group Bearing Capacity and Settlement (Service Limit State)

For the service limit state, compare the factored load to the maximum group capacity perAASHTO Articles 10.7.2.1 and 10.7.2.3 to determine the pile depth which will result in thedesired maximum settlement. Treat the pile group as an equivalent footing as described inArticles 10.7.2.1 and 10.7.2.3 in the AASHTO Specifications, and calculate the settlement ofthe group. Do this to get the minimum depth required to prevent the settlement criteria frombeing exceeded.

4. Group Effects for Uplift

AASHTO Article 10.7.3.7.3 applies.

5. Group Effects for Lateral Loads

“Group Effects for Lateral Loads” under “Shaft Design” applies.



9.9-38 July 2000

C. Resistance Factors for Pile Foundation Design

Resistance Factors for Strength Limit State for Pile Foundations(adapted from Table 10.5.5-2 in AASHTO LRFD specifications)

Table 9.9.8-2Type of ResistanceResistance Method/Soil/Condition Factor

Bearing Capacity φqs Skin Friction in Clay:of Single Piles - α-method (Tomlinson, 1987) 0.70(static analysis - β-method (Esrig and Kirby, 1979) 0.50methods) - λ-method (Vijayvergiya and Focht, 1972) 0.55

Skin Friction in Sand:- SPT Method (Meyerhof) 0.45- CPT Method 0.55- Nordlund Method +0.55

φqp End Bearing in Clay and Rock:- Clay (Skempton, 1951) 0.70- Rock (Canadian Geotechnical Society, 1985) 0.50

End Bearing in Sand:- SPT Method (Meyerhof) 0.45- CPT Method 0.55- Thurman’s Method +0.55

φqs, Side and Base Resistance:φqp - Load test *0.70-0.80

Bearing Capacity φdyn Side Resistance and End Bearing, All Soils:of Single Piles - WSDOT driving formula, per Standard Specifications 0.50(dynamic analysis - ENR driving formula 0.25methods) - Wave Equation, without PDA ‡0.50

- Wave Equation with PDA (PDA used on one pile/ pier and 2 to 5% of the piles) ‡0.60- PDA with CAPWAP (min. one pile/pier and 2 to 5% of the piles) ‡0.60-0.75

Uplift Resistance φup a-method (clay) 0.60of Single Piles b-method (clay) 0.40

l-method (clay) 0.45SPT-method (Meyerhof method for sand) 0.35CPT-method (sand) 0.45Nordlund Method (sand) +0.45CAPWAP ?Uplift Load Test *0.70-0.80

Block Failure φqgr Clay 0.65

Group Uplift φupgr Sand 0.55Resistance Clay 0.55

Lateral Pile φlat Clay, sand, and rock (single piles and groups): # 1.0

Resistance

*For the load test resistance factor, the values shown are more conservative than as provided in the AASHTO specifications. They have been adjusted based oncalibration to current WSDOT practice (FS = 2 if load test is conducted). Note that the number of load tests required will depend on the uniformity of the soil/rockconditions and whether or not a well defined bearing stratum is present. Assuming that an appropriate number of load tests are conducted, use the largest resistance factorin the specified range for very uniform conditions or for a well defined and highly resistant bearing stratum, and use the lowest resistance factor in the range fornonuniform conditions or a poorly defined bearing stratum.

‡For the wave equation and PDA resistance factors, the values shown are more conservative than as provided in the AASHTO specifications. They have been adjustedbased on calibration to current WSDOT practice (FS = 2.25 if wave equation and PDA are conducted, and FS = 2.75 if wave equation without PDA is used). For PDAwith CAPWAP, calibration of CAPWAP results to pile load test results indicate that a resistance factor as high as 0.75 to 0.8 could be used. However, that calibrationassumes that a CAPWAP is performed on every pile, or the soil/rock conditions are perfectly uniform, which in actual applications is never the case. Assuming that thenumber of piles as specified in the table are tested using a PDA/CAPWAP, use the largest resistance factor in the specified range for very uniform conditions or for a welldefined and highly resistant bearing stratum, and use the lowest resistance factor in the range for nonuniform conditions or a poorly defined bearing stratum. Theseresistance factors for pile capacity should be considered to be tentative until additional research and comparative designs are accomplished+The approach defined above for the use of load test data or PDA/wave equation was also used to determine resistance factors for the Nordlund and Thurman pile capacitymethods (current WSDOT practice is to use FS = 2.5 with these methods). Furthermore, statistical analysis provided by the FHWA course manual “Load and ResistanceFactor Design (LRFD) for Highway Bridge Substructures,” 1998, for the Nordlund method confirms that resistance factors for this method should be on the order of 0.55to 0.6.#For φ

lat, the value used will depend on the confidence in the soil parameters.



July 2000 9.9-39

D. Determination of Pile Driveability

If the required minimum tip elevation is deeper than the penetration depth estimated to obtain thedesired pile capacity (Qult), the pile will need to be overdriven. Estimate the amount of overdrive(i.e., maximum driving capacity) required using the unfactored pile capacity versus depth curve asillustrated in Figure 9.9.7-3, but instead using the minimum tip elevation to determine the ultimatepile capacity at the minimum tip elevation. This will yield the maximum driving resistance per theWSDOT Standard Specifications to be used to size the pile hammer and to determine the minimumpile wall thickness. The pile hammer and minimum pile wall thickness are sized so that maximumdriving stresses are not exceeded, and pile damage during driving is prevented. In this case, a pre-liminary wave equation analysis should be conducted during design by the Geotechnical Branch toevaluate potential pile driveability, and to set minimum pile wall thickness and minimum hammerenergy requirements for the contract specifications as appropriate.

E. What Geotechnical Branch Will Provide to Bridge Office for LRFD Pile Design

To evaluate pile capacity, the Geotechnical Branch will provide information regarding pile capacityusing one of the following two approaches:

1. A plot of the unfactored ultimate bearing capacity (Qult) as a function of depth for various piletypes and sizes for strength and extreme event limit state calculations would be provided. Thisdesign data would be used to determine the feasible ultimate pile capacity, the estimated depthfor pile quantity determination, and the maximum driving resistance required to reach theminimum tip elevation. If scour and/or liquefaction is likely to occur, separate tables willusually be provided which summarize the estimated downdrag loads and capacity losses.Such assumptions/special considerations will also be identified on the plots. See Figure 9.9.8-3for example of pile data presentation.

2. Only Qult and the estimated depth at which it could be obtained, and tabulated capacityreductions necessary to account for the effects of scour and/or liquefaction, would be providedfor one or more selected pile types and sizes.

In most cases, Qult and Qup for the strength, extreme event II, and extreme event I limit states will bethe same, as loss of skin friction due to liquefaction downdrag will be taken into account separately.However, if soils are present which weaken but do not liquefy during an earthquake, a separate curvefor the extreme event I limit state may be needed.

For evaluating uplift, the Geotechnical Branch will provide, as a function of depth, the ultimateunfactored uplift capacity, Qup. This will be provided as a function of depth, or as a single value fora given minimum tip elevation, depending on the project needs, and will be reduced to account forscour and/or liquefaction. Resistance factors will also be provided for strength and extreme eventlimit states.

Resistance factors for bearing capacity for all limit states will also be provided (see Table 9.9.8-2for an example).

If downdrag is an issue, the ultimate downdrag load, QDD, as a function of pile diameter will beprovided, as well as the depth zone of the pile which is affected by downdrag, the downdrag loadfactor, and the cause of the downdrag (settlement due to vertical stress increase, liquefaction, etc.).If liquefaction occurs, the reduction in side friction resistance, Qs, to be subtracted off of the ultimatecapacity plots will be provided.



9.9-40 July 2000

If lateral loads imposed by special soil loading conditions such as landslide forces are present, theultimate lateral soil force or stress distribution, and the load factors to be applied to that force orstress, will be provided.

The Geotechnical Branch will also provide group reduction factors for bearing capacity and uplift ifnecessary, as well as the associated resistance factors, but these will be rarely needed.

The Geotechnical Branch will continue to provide P-Y curve data as a function of depth as has beendone in the past. Two separate tables will typically be provided, one for static properties and one fordynamic properties (see Section 9.9.6C for an explanation on how they are to be used.) Resistancefactors for lateral load analysis will not be provided, as the lateral load resistance factors willtypically be 1.0.

Minimum tip elevations for the pile foundations will be provided as appropriate. Minimum tipelevations will be based on pile foundation settlement, and, if uplift loads are available, the depthrequired to provide adequate uplift capacity. Minimum pile tip elevations provided in theGeotechnical Report may need to be adjusted depending on the results of the lateral load and upliftload evaluation performed by the Bridge and Structures Office. If adjustment in the minimum tipelevations is necessary, or if the pile diameter needed is different than what was assumed by theGeotechnical Branch for pile capacity design, the Geotechnical Branch should be informed so thatpile driveability, as discussed below, can be re-evaluated.

Pile driveability will be evaluated at least conceptually for each project, and if appropriate, a waveequation analysis will be performed and the results of the analysis provided in terms of specialrequirements for hammer size and pile wall thickness, etc. The maximum driving resistance requiredto reach the minimum tip elevation will also be provided. Note that it will not be possible to obtainthe maximum driving resistance from the pile bearing capacity plots mentioned previously if the pilebearing capacities provided in the plots have been reduced to account for scour and/or liquefaction.A separate determination is required to estimate the maximum driving resistance if the pile capacityversus depth plots include the effects of scour or liquefaction. Once the pile analysis and design arecompleted in the Bridge and Structures Office, the Geotechnical Branch is to be contacted forfinal reivew ad comment.

Example Presentation of Resistance Factors for Pile DesignTable 9.9.8-3

Resistance Factor

Limit State Bearing Capacity, Qult Uplift, Qup

Strength X X

Service X —

Extreme Event X X



July 2000 9.9-41

Example Presentation of Downdrag LoadsTable 9.9.8-4

QDDs

Static Conditions QDDliq

Due to Liquefaction

Pier No. Pile Dia = __ Pile Dia = __ Pile Dia = __ Pile Dia = __

X X X X X

X X X X X

X X X X X

Example Presentation of Skin Friction Loss Due to Downdrag or ScourTable 9.9.8-5

Qs Loss to be Applied to Figure 9.9.8-2 Qs Loss to be Applied to Figure 9.9.8-2Due to Static Downdrag or Scour Due to Liquefaction Downdrag

for Strength Limit Qult for Extreme Event Limit Qult

Pier No. Pile Dia = __ Pile Dia = __ Pile Dia = __ Pile Dia = __

X X X X X

X X X X X

X X X X X



9.9-42 July 2000

Example Presentation of Pile Bearing Capacity and UpliftFigure 9.9.8-3

Ele

vati

on o

r D

epth

Ele

vati

on o

r D

epth

Bearing Capacity, Qult (unfactored) Uplift Capacity, Qup (unfactored)

Strength

Dia. = _____

Assumptions: Strength

Dia. = ____ mm

Assumptions:

Extreme event

(assumes for this example

that liquefaction

Dia. = _____

Extreme event

(assumes for this example

that liquefaction

Dia. = _____

P65:DP/BDM9

Extreme Event I limitDia. = ___

Extreme Event I limitDia. = ___

Strength and ExtremeEvent II limit,Dia. = ___Assumptions:

Strength and ExtremeEvent II limit,Dia. = ___Assumptions:

▲


Substructure Design Bibliography

9.99 Bibliography

1. W. T. Moody, “Moments and Reactions for Rectangular Plates,” U.S. Dept. of the Interior, Bureau ofReclamation, 1970.

2. Richard Bares, “Tables for the Analysis of Plates, Slabs, and Diaphragms Based on the ElasticTheory,” Wiesbaden, 1971.

3. Peck, Hansen, Thornburn, “Foundation Engineering,” John Wiley & Sons, Inc., 1967.

4. Ultimate Strength Design Handbook, Volume 1, ACI Special Publication No. 17, American ConcreteInstitute, Detroit, 1967.

5. S. Timoshenko, “Theory of Elastic Stability,” McGraw Hill.

6. G. A. Leonards, Ed. “Foundation Engineering,” McGraw Hill, 1962. 624.15 L553f

7. W. C. Huntington, “Earth Pressures and Retaining Walls,” Wiley, 1957.

8. Wayne C. Teng, “Foundation Design,” Prentice-Hall, Inc., 1962.

9. C. W. Dunham, “The Theory and Practice of Reinforced Concrete,” McGraw Hill, 1953.

10. Association of Drilled Shaft Contractors, Inc., 6060 N. Central Expressway, Dallas, TX 75206,“Standards and Specifications for the Drilled Shaft Industry,” Revised July 15, 1979.

11. L. C. Reese and S. J. Wright, “Drilled Shaft Manual, Volume I, Construction Procedures and Design forAxial Loading,” U.S. Department of Transportation, Office of Research and Development,Implementation Division, HDV-22, Washington, DC 20590, July 1977.

12. L. C. Reese and J. D. Allen, “Drilled Shaft Manual, Volume II, Structural Analysis and Design forLateral Loading,” U.S. Department of Transportation, Office of Research and Development,Implementation Division, HDV-22, Washington, DC 20590, July 1977.

13. L. C. Reese, “Analysis of Laterally Loaded Piles, Software Documentation,” Department of CivilEngineering, University of Texas at Austin, Austin, TX 78712, July 1997.

14. Washington State DOT, Olympia, Washington, “Instructions to Engineers Structural ApplicationsComputer Manual.”

15. McDonnell Douglas Automation Company, Box 516, St. Louis, MO 63166, “ICES STRUDL UserManual,” April 19890.

16. Noel J. Everard and Edward Cohen, “Ultimate Strength Design of Reinforced Concrete Columns,”ACI Publication SP-7.

17. R. J. Woodward, W. S. Gardner and D. M. Greer, “Drilled Pier Foundation.”

18. Karl Terzaghi, “Evaluation of Coefficient of Subgrade Reaction,” Geothechnique, Volume V, 1955.

19. Prakash S., “Behavior of Pile Groups Subject to Lateral Loads,” Ph.D. Thesis, University of Illinois,1962.

9-99:WORK:BDM3

January 1991 9.99 - 1

January 1991 9.2 - A1


Substructure Design Design Aids

24-Inch Diameter Round Column Section Capacity Chart



9.2 - A2 January 1991


January 1991 9.2 - A3






9.2 - A4 January 1991


January 1991 9.2 - A5






9.2 - A6 January 1991

Column Design Flow Chart

January 1991 9.2 - A7



Column Design Effective Length Factors



9.2 - A8 January 1991

Buckling Load — Round Columns

January 1991 9.2 - A9



Factor Charts



9.2 - A10 January 1991

Moment Magnification Factor

January 1991 9.2 - A11



Column Design Example

July 2000 9.9-A-1


Simplified Example for Pile Foundation Design,Appendix A Including Resistance Factor Calibration

1. Consider the following soil profile for a bridge pier:

A pipe pile, closed end, will be used for this example. Assume that the pile supported footing has no bendingmoments applied to it to keep the example simple. Structural analysis of potential pile options (see AASHTOcode for maximum loading allowed for pile stresses and to prevent buckling or crushing) and WSDOT policyindicates that a minimum 18 inch diameter is required for a 300 ton pile and 24 inch diameter is required fora 450 ton pile. Static analysis and previous experience with this bearing stratum indicates that the feasibleultimate pile capacity for the bearing stratum is 300 tons for an 18 inch diameter pipe pile (this is Q

ult,

unfactored).

2. Using a static analysis method (assume SPT method is used), the unfactored ultimate pile capacity versusdepth curve is as follows:

Loose SAND

Dense SAND

30 ft

Factored Load = 900 tons for Strength I

Factored Load = 2100 tons for Extreme

Depth (ft)

Ultimate Pile Capacity (tons)

50

100 200 300

40

30

20

10

I



9.9-A-2 July 2000

3. The WSDOT driving formula will be used as the quality control method for pile capacity in the field. Forthis method, φ

dyn = 0.5 for Strength I (see calibration in Steps 3.a to 3.d below), and φ

dyn = 1.0 for Extreme I.

a. Pile capacity data which illustrates accuracy of WSDOT formula:

b. Parameters for calibration to determine resistance factor:

Parameter Definition Value

Bias Factor for Ratio of measured to predicted resistance, 0.97Resistance, λ

Rusing log normal mean values

COVR

Log normal coefficient of variation for 0.356resistance prediction

QD/Q

LDead load to live load ratio Typical value is 3.0

λQD

Bias factor for structure dead load, using log 1.05 (assume CIPnormal mean values concrete structure)

COVQD

Log normal coefficient of variation for 0.10 (assume CIPstructure dead load concrete structure)

λQL

Bias factor for structure live load, 1.15using log normal mean values

COVQL

Log normal coefficient of variation for 0.18structure live load

βT

Target reliability index 2 to 2.5 for pile groups

FS ASD factor of safety typically used in practice 2.5 to 3.0

New (1998) Standard Specifications Equation - End

of Driving Data - Ultimate Capacity

0

500

1000

1500

2000

2500

3000

3500

0 500 1000 1500 2000 2500 3000 3500

Load Test Rult - Davisson's Criteria (kips)

Spe

Steam

Hammers

OE Diesel

Hammers

CE Diesel

Hammer

Rult = FE Ln 10N

F = 3.3 (steam)

F = 3.1 (OE Diesel)

F = 2.4 (CE Diesel)

95%

Confidence

Pre

dic

ted

Ult

. Cap

acit

y, 2

000

Sta

nd

ard

Sp

ec. E

qu

. (ki

ps)

July 2000 9.9-A-3



c. Check β implied by current ASD design safety factor:

For FS = 3.0, β = 2.39

(Note: The FS of 3.0 was used when our standard specifications specified the use of the ENR equation,which has a much higher coefficient of variation and tended to over-predict capacity (bias of 0.8, COV

R

of 0.61, implying a β = 1.11 for FS = 3.0) than our current driving formula. We now use FS = 2.5 with ourcurrent driving formula.)

In conclusion, a β = 2.0 appears adequate for this analysis considering previous practice.

d. Check φR implied by current ASD safety factor:

For FS = 3.0, φR = 0.46

e. Calculate the resistance factor, φdyn

, for the strength limit state:

γD = LRFD specified load factor for dead load = 1.25

γL = LRFD specified load factor for live load = 1.75

β

λ

λ λ=

+

+

+ ++

+( ) + +( )[ ]

ln

ln

RD

L

QDD

LQL

QD QL

R

R QD QL

FS QQ

QD

COV COV

COV

COV COV COV

1 1

1

1 1

2 2

2

2 2 2

β =

( ) +( )( ) +

+ ++

+( ) + +( )[ ]=

ln. . .

. . .

. .

.

ln . . ..

0 97 2 5 3 0 1

1 05 3 0 1 15

1 0 1 0 18

1 0 356

1 0 356 1 0 1 0 181 93

2 2

2

2 2 2

φγ γ

R

DD

LL

D

L

QQ

FS QQ

=

+

+

= ( ) ++( )

=1

1 25 3 0 1 75

2 5 3 0 10 55

. . .

. ..

φλ γ γ

λ λ βdyn

R DD

LL

QD QL

R

QDD

LQL T R QD QL

QQ

COV COV

COV

QQ COV COV COV

=

+

+ ++

+

+( ) + +( )[ ]

1

1

1 1

2 2

2

2 2 2exp ln

φdyn =( ) +( ) + +

+

( ) +( ) +( ) + +( )[ ]

=0 97 1 25 3 0 1 75

1 0 1 0 18

1 0 356

1 05 3 0 1 15 2 0 1 0 356 1 0 1 0 180 535

2 2

2

2 2 2

. . . .. .

.

. . . exp . ln . . ..



9.9-A-4 July 2000

If use a βT = 2.5, get φ

dyn = 0.44.

In conclusion, recommend a φdyn

= 0.50 for design, based on the use of the WSDOT driving formula.

(Note: If use the ENR equation, which has a bias of 0.80 and a coeff. of variation of 0.61, for a βT = 2.0,

would need a φR = 0.27. If a CAPWAP is used to determine pile capacity, a bias of 1.45 and a coeff. of

variation of 0.44 was obtained for end of driving conditions, resulting in a φR = 0.68 for a β

T = 2.0. For

a CAPWAP at beginning of redrive conditions, a bias of 1.61 and a coefficient of variation of 0.42 wasobtained, resulting in a φ

R = 0.79 for a β

T = 2.0.)

4. The total factored load for the pier is as shown in the figure in Step 1.

5. Determine the number of piles to required to support the pier load, using a feasible ultimate pile capacityQ

ult = 300 tons from Steps 1 and 2. Assume all piles have the same load for this simplified example.

(Note that we have not considered a pier loading scenario where the corner piles are more heavily loadedthan the interior piles, which would more normally be the case. This simplified uniform loading case wasselected to keep this example simple.)

For the Strength I limit state: Factored pier load = 900 tonsResistance/pile = φ

dynQ

ult = 0.5(300 tons) = 150 tons

No. of piles = 900/150 = 6 piles

For the Extreme Event I limit state: Factored pier load = 2100 tonsResistance/pile = φ

dynQ

ult =1.0(300 tons) = 300 tons

No. of piles = 2100/300 = 7 piles

6. Determining the estimated pile length from the figure in step 2, Dest.

= 50 ft.

7. For the contract, the pile quantities will be based on an estimated pile length of 50 ft, and the pile capacityshown in the plans will be 300 tons ultimate. The pier will have a seven pile group, because the extremeevent limit state controls design in this case.

8. A pile group settlement analysis was performed with the tips up in the loose sand (depth of 25 ft) and withthe pile tips 5 ft into the dense sand (depth of 35 ft). Group settlement in the first case was determined tobe 1.5 inches, and in the second case was just below 1 inch. Therefore, minimum pile tips will be speci-fied in the contract, but must check lateral load capacity and deflection, and uplift requirements beforeselecting a final minimum tip elevation.

9. The uplift load per pile based on factored loads was determined to be 30 tons from the structural analysisfor the strength limit state. For the extreme event limit state, the uplift load per pile was determined to be100 tons.

10. Calculate the depth required to obtained the required uplift capacity, using static analysis methods. Theresistance factor from the AASHTO LRFD design specifications, using the SPT method, φ

static, is 0.35 for

the strength limit state and 1.0 for the extreme event limit state.

July 2000 9.9-A-5



From this figure, the minimum depth required is 31 ft for the strength limit state and 35 ft for the extremeevent limit state.

11. Lateral load analysis for deflection and fixity indicates that the pile tips must be at least 27 ft deep. Upliftrequirements for the extreme event limit state appears to control the minimum depth required, consideringsettlement, uplift, and lateral load requirements. Therefore, select a minimum tip elevation based on aminimum pile depth of 35 ft.

12. Based on the pile capacity vs. depth plot and a required minimum penetration of 35 ft, which is less thanthe estimated tip elevation, overdriving will not be required. Therefore, use a pile capacity of 300 tonsultimate for sizing the pile hammer and pile wall thickness required for constructability.

Factored Pile Uplift Capacity (tons)

1.0Qult for extreme event

limit state

50

50 100 150

40

30

20

10

Depth (ft)

30

0.35Qult for strength

limit state


Detailing Practice Contents

Page

10 Detailing Practice . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10.1-1

10.1 Drawings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

10.1.1 Standard Office Practices . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1A. Purpose . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1B. Planning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1C. Drawing Orientation and Layout Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2D. Lettering . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2E. Line Work . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5F. Scale . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5G. Grpahic Symbols . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6H. Structural/Architectural Section, Views, and Details . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6I. Revisions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6J. Care of Original Manual Drawings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

10.1.2 Final Layout . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

10.1.3 Bar Lists . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

10.1.4 Bridge Standard Plans and Office Standards . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

10.1.5 Plotting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12


10.1-A1-1 through 7 Abbreviations10.1-A2 Structural Steel

10.1-A3 Footing Layout

Appendix B — Examples

10.1-B1 Footing Layout

10-CON:V:BDM10

October 1993 10.0 - i


Detailing Practice Drawings

10.0 Detailing Practice

10.1 Drawings

The following is to provide the novice with basic information on computer drafting and the fundamentalsof file management, and plotting for this activity.

Drafting and plotting of drawings is done from BREWS (BRidge Engineers WorkStation) terminals.These terminals operate on the VMS operating system, and GDS is the drafting software used by theBridge Division. GDS is designed with built-in macros that retrieve information based on filenames thatyou select from menus or input in batch mode.

STDROOT:[FGB]TBFF.FGB is an example of a filename, where:

STD: is the root directory where all the files for the STD job are kept. A job is generallydefined as the work to be done for a particular L-XXXX (where L = Location andXXXX = the accounting number assigned to the job)

[FGB] is the subdirectory where all drawing files are kept.

TBFF is the user's name for the file. This has a 32 character limit and the first 8 charactersmust be unique.

.FGB is the file extension. FBG is always the GDS extension for all drawings.

Please note that all colons, brackets and periods must be used as shown in the example.

Directories provide a convenient way to keep job files together, but only if they are used with consistencyand updated regularly (clean out obsolete files etc.). Users should choose directory names that are relativeto the job they are working on (State Route numbers, bridge numbers, ramp designations, acronyms). Thismakes it easier for someone to find files that pertain to your job should you be unavailable. Using directo-ries is also important in terms of achieving job files. It is easy to transfer all files that pertain to a job(and only those files that pertain to the job) to a tape when these files are consolidated in one directory.

A user can have personal directories or the computer support personnel can set up a job directory to beused by a group of users.

To call up a CAD sheet, first select the job directory listing menu in the lower left of the GDS window. Alisting of job directories appear on the screen; choose the proper job and then, from the next menu, theCAD sheet file you want.

10.1.1 Standard Office Practices

A. Purpose

The purpose of these standards is to enable the Bridge Branch to produce consistent and effectiveplan sheets which will have uniform appearance and information. Engineers and detailers areresponsible for ensuring that these criteria are implemented.

B. Planning

The engineer coordinates with the structural detailer the scope of the detailing work involved. Similarbridge plans and details should be reviewed and kept as examples for maintaining consistent detailingpractices. These examples should not be older than three years.

October 1993 10.1 - 1



C. Drawing Orientation and Layout Control

1. Standard bridge sheet format is 331/2 inches x 221/2 inches with the bottom 2 inches used for titleblock and related information.

2. Regular graphite lead or ink shall be used on vellum drawings. Ink or plastic lead only shall beused on mylar drafting film.

3. Drawings shall be carefully organized so the intent of the drawing can be read easily. Northarrows shall be placed on layouts and footing layouts. (See Chapter 2 and 10.1.2 for specialrequirements for preliminary plan and layout sheets.) Related details shall be grouped together inan orderly arrangemnet. Do not overcrowd the drawing with details. The following is a standardsheet configuration when plan, elevation, and sectional views are required.

D. Lettering

1. General

a. Text # 4 Ames Lettering Guide Manual, CBR 35 CADD.

Titles #6 Ames Lettering Guide Manual, CBR 70 CADD.

Underline all titles with a single line having the same weight as the lettering used. Use "basTITLE".

b. Lettering shall be upper case only, slanted at approximately 68 degrees angle on the AmesLettering Guide and of uniform height.

c. Lettering shall be oriented so as to be read from the bottom right edge of the sheet.

2. Dimensioning

a. A dimension shall be shown once on a drawing, unless repeating it is necessary for clarity.Duplication and unnecessary dimensions should be avoided. All dimension figures shall beplaced above the dimension line, and so that they may be read from the bottom of the rightedge of the sheet, as shown in the following detail:

10.1 - 2 October 1993

PLAN

SECTIONS&

DETAILS

ELEVATION



b. Reinforcing bar clearances need not be specified on plans unless different from the “generalNotes.”

c. When details or structural elements are complex, utilize two drawings. One for dimensionsand the other for reinforcing bar details.

d. Dimensions 12 inches or more shall be given in feet and inches unless the item dimensionedis conventionally designated in inches (for example, 16′ pipe).

e. In dimensions more than 1 foot, fractions less than 1 inch shall be proceeded by 0 (forexample, 3′-03/4″.

f. Placement of dimensions outside the view, preferably to the right or below, is desirable.However, in the interest of clarity and simplicity it may be necessary to place themotherwise. Examples of dimensioning placement are shown on Figure 10.1.1-1.

October 1993 10.1 - 3



Figure 10.1.1-1

10.1 - 4 October 1993



E. Line Work

1. All line work must be of sufficient size, weight, and clarity so that it can be easily read from aprint that has been reduced to one-half the size of the original drawing. The line style used for aparticular structural outline, centerline, etc., shall be kept consistent wherever that line is shownwithin a set of bridge plans.

2. Linework shall have appropriate gradations of width to give line contrast as shown below. Careshall be taken that the thin lines are dense enough to show clearly when reproduced.

3. When drawing structural sections showing reinforcing steel, the outline of the section shall be aheavier line weight than the rebar.

The Mark No. “bubble” for reinforcing steel shall be a rectangle. use “[” “]” to create textrectangles.

Epoxy coated reinforcement shall be denoted by a triangle in the following manner.

42 E #6F. Scale

When selecting a scale, it should be kept in mind that the drawing will be reduced. Generally, theminimum scale for a section detail with rebars is 3/8 inch = 1 foot. The scale used on steel bridgeplans will be 3/4 inch = 1 foot minimum.

October 1993 10.1 - 5



10.1 - 6 October 1993

Sections and views may be enlarged to show more detail, but the number of different scales usedshould be kept to a minimum.

G. Graphic Symbols

1. Graphic symbols shall be in accordance with the following:

a. Structural Steel Detailing: AISC Steel Construction Manual see structural steel chart.

b. Welding symbols: See Lincoln Welding Chart.

2. Symbols for hatching different material is shown on Figure 10.1.1-2.

H. Structural/Architectural Sections, Views, and Details

1. A section cuts through the structure; a view is from outside the structure; a detail shows astructural element in more detail — usually a larger scale.

2. Whenever possible, sections and views shall be taken looking to the right ahead on station ordown. Care shall be taken to ensure that the orientation of a detail drawing is identical to that ofthe plan, elevation, etc., from which it is taken.

3. On plan and elevation drawings where it is impossible to show cut sections and details, thesection and detail drawing should immediately follow the plan and elevation drawing unless thereare a series of related plans. If it is impractical to show details on a section drawing, a detailsheet should immediately follow the section drawing. In other words, the order should be fromgeneral plan to more minute detail.

4. Structural and architectural sections, views, and details shall be identified by a circle divided intoupper and lower halves.

Examples are shown in Figure 10.1.1-3.

5. Breaks are allowable in lines provided that their intent is clear.

6. Each pier shall be detailed separately as a general rule. If the intermediate piers are identicalexcept for height, then they can be shown together.

I. Revisions

1. Manual Techniques

a. Pencil on paper can simply be erased and done over.

b. Ink on film can be washed off with plain water. Older drawings may need to soak awhile oruse rubbing alcohol, but this is preferable to erasing, which will remove the matte finish andmake the area difficult to draw on.

c. Photo lines can usually be eradicated using chemical eradicators (Solutions A and B)available from the vault. This preserves the surface finish. If the chemical is ineffective,check to see if the print is reverse reading in which case the eradicator must be applied tothe back. (Reverse reading film positives are actually preferable so that changes are notmade on the same surface from which the lines are removed.) Erasing on the front of amylar sheet should be a last resort as it removes the surface finish.



October 1993 10.1 - 7

Figure 10.1.1-2



10.1 - 8 October 1993

Figure 10.1.1-3



d. Plastic lead on film must be erased with a soft eraser, taking care to avoid removing thesurface finish.

e. Film surface damaged by erasing may be restored by careful roughening with a hand eraser.

f. A chemical solution called sepia eradicator can be used to eradicate lines on sepias. TheBridge Branch seldom uses sepias, but if needed, this solution may be obtained from thestockroom if no one in Bridge has a bottle.

2. Cadd sheets shall be changed on the cadd film and replotted.

3. Plan Revisions Versus Addendums

a. All changes to plans require initials of the Bridge Engineer or the Unit Design SupervisingEngineer. The locations of all changes (except deletions) shall be shaded so they can beeasily found. Shading on preliminary plans is removed before printing the ad copies. The oldmethod of using a number enclosed in a circle enclosed in a triangle is no longer acceptable.

b. Use the revision block in the left margin to record changes, including the due date anddescription of each change, made after the preliminary plan is signed by the Bridge Engi-neer, but before the ad copy. This left margin block is also removed before printing the adcopies.

c. The Olympia Service Center Plans Branch places a border along the bottom of the plansheets. This border contains blocks where the Plans Branch assigns sheet numbers, a contractnumber, a title, and a revision block for the contract plans. For changes made after the adcopy is mailed out (addendum) fill in the revision block, including the due date and descrip-tion of each addendum. Also, include the contract title, contract number, and sheet numberassigned by the Plans Branch (e.g., if bridge sheet number 4 of 7 was assigned plan sheetnumber 18 or 30 by the Plans Branch, it must remain plan sheet 18 of 30 if revised).

J. Care of Original Manual Drawings

1. Original manual drawings should be handled with care to avoid damaging them in any way.

2. Original manual drawings should be stored flat, either in a designated file or in the drafter’s desk.

3. If it is necessary to leave an original manual drawing out overnight, it should be covered toreduce exposure to mishap.

4. An original manual drawing shall not be used for review or checking. All review or checkingshall be done from prints.

May 1995 10.1 - 9



10.1 - 10 May 1995



10.1.2 Final Layout

a. General — The original preliminary plan will be used to create the final layout. Views, data, andnotes may be repositioned to improve the final product.

b. Items on the preliminary plan which should not appear on the final layout are as follows:

1. Typical roadway sections.

2. Notes to the district.

3. Vertical curve, superelevation, and curve data for other than main line.

4. Other information that was preliminary or that will be found elsewhere in the plans.

c. Items not normally on the preliminary plan which should be added are as follows:

1. Test hole locations (designated by 3/16 inch circles, quartered) to plan view.

2. Elevation view of footings, seals, piles, etc. Show elevation at bottom of footing and, ifapplicable, the type and size of piling.

3. General notes above legend in upper right-hand corner usually in place of the typical section.

4. Title “LAYOUT” in the title block and sheet number in the space provided.

5. Other features, such as lighting, conduit, signs, excavation, riprap, etc., as determined by thedesigner.

6. The layout check list can be used for reference. See Chapter 2.

October 1993 10.1 - 11



10.1.3 Bar Lists

Barlist files are different from regular drawing files in that they consist of nine sheets (or windows). Inorder to view the various sheets type in DR SHEETn where n is a number from 1 to 9. All special bendtypes must be drawn in the SPECIAL window (DR SPECIAL). If the special bends are drawn in any ofSheets 1 through 9 they will be erased when the BARLIST program is rerun. Special bend types drawnin the SPECIAL window will appear on all sheets and will not be erased when BARLIST is rerun.

Barlists have a different set of menus in GDS. While you are in GDS make the following selections:

DWG MGTFILESMENU PERSBARLIST

This will get you into the special menus to put page numbers on the sheets and plot bar lists.

To create page (or plan sheet) numbers for bar list sheets, select the First Sheet No. option in the NAMESmenu then enter the value of the first page number. All subsequent sheets will be numbered automatically.If the page number is alphanumeric (that is, it contains both letter and number parts) then choose theSheet No. Prefix(Letter) option in the NAMES menu. Do not use this option if there is no letter in thepage number.

There are three ways to plot barlist sheets. Plotting can be done interactively in a GDS session by typingDR SHEETn then using PLOT NOW, or by using the F9 AND F10 function keys (F9 will plot fullsizeand F10 halfsize), or by using batch procedures as described in section 10.1.5. The batch routine will askyou how many sheets there are to the barlist and will plot them all whereas PLOTNOW and the functionkeys will plot only one sheet at a time.

Barlist sheets do not require an engineers stamp.

10.1.4 Bridge Standard Plans and Office Standards

a. New standards and revisions to existing Standard Plans are made according to the same standardoffice practices as plan sheets.

b. Use of standard sheets for contract plans from the CADD office.

1. Copy the standard file to your directory and rename the new file by picking “Copy STD file”from the FILES menu.

2. A plot should be made on which the designer marks the required changes.

3. Using the marked plot as a guide, the structural detailer makes changes and requests new plots.

4. SR number, job number, sheet number, and title should be added on layout sheet only.

c. Changes are made to the master CADD standard file upon the receipt of the revision from the BDMcoordinator with his signature/initials and current date of the new revision.

10.1.5 Plotting

The user can plot either interactively in GDS or use the SPLOT command after a VMS prompt. Plottingmay take as long as 20 minutes, so be patient. It depends on how many plots are already waiting. To see alisting of plot files waiting type PLIST at the VMS prompt. See section 10.1.3 for plotting bar lists.

10.1 - 12 October 1993



October 1993 10.1 - 13

Interactive Plotting

There are two interactive ways to plot in GDS. The user can make menu selections, or can use functionkeys.

PLOT NOW is a menu pick that will plot what is on the screen. Depending on your selection, you can getfull size, half size or laser printer plots on the screen.

Functions Keys are a short cut method to menu selections. Function key F9 plots a full size sheet and F10plots halfsize.

Batch Plotting

Using SPLOT (to Plot a Single Sheet)

A drawing may be requested at any terminal by the commands given in the example below. You willneed to know the filename, which is shown above the WSDOT logo on every sheet.

The procedures would be as shown below for file, NRUP116ROOT:[FGB]LAYOUT.FGB. (begin-ning at the VMS prompt):

VS15A>SPLOT(EXIT or Ctrl/Z to quit)FILENAME: LAYOUTPLOT SIZE: Large OR [Small], or 3 for Laser print:

Hit the Return key for the default smal or enter ‘L’ for large.

NUMBER OF COPIES [1]:Hit the Return key for the default 1 or enter the number of copies you want.

Using MPLOT (to Plot Multiple Sheets)Please note that this routine can tie up a plotter for hours.

First, create a data file that includes all the filenames for the sheets you want to plot. In thefollowing example the data file PLOTLIST is set up to plot: NEBAR, JUNKTST, andLAYOUT. The routine begins at the VMS prompt (this is not in the menus).

VS15A>MPLOTPLOT LIST INPUT FILE: PLOTLISTDIRECTORY NAME (NO FGB):NRUP116PLOT SIZE: Large OR [Small]:

Hit the Return key for the default small or enter large

NOW SUBMITTING PLOT OF NRUP116FGB:NEBAR, TO BATCHJob SINGLE_BATCH_PLOT (queue VS15A_BATCH, entry 20) started onVS15A_BATCH

ERROR IN LOCATING NRUP116FGB:JUNKTST.FGB

NRUP116FGB:LAYOUT.FGB IS LOCKED BY [RUDEEN]UNABLE TO PLOT

As you can see, only one file, NEBAR, was actually plotted. JUNKTST does not exist, and LAYOUT iscurrently being used by Jeff Rudeen.

10-1:V:BDM10


Detailing Practice Design Aids

April 1991 10.1 - A1 - 1

AbbreviationsA. General

1. Because different words sometimes have identical abbreviations, the word should be spelled out where themeaning may be in doubt.

2. A few standard signs are in common use in the office of Bridge and Structures. These are listed with theabbreviations.

3. A period should be placed after all abbreviations, except as listed below.

4. Apostrophes are usually not used. Exceptions: pav’t., req’d., r’dway.

5. Abbreviations for plurals are usually the same as the singular. Exceptions: figs., no., ctrs., pp.

6. Abbreviations in titles should be avoided if possible.

B. List of abbreviations commonly used on bridge plan sheets:

A

about abt.abutment abut.adjust, adjacent adj.aggregate agg.alternate alt.ahead ahd.aluminum al.Americal Society for Testing and Materials ASTMAmerican Association of State Highway and AASHTO

Transportation Officialsand &angle point A.P.approved apprd.approximate approx.area Aasbestos cement pipe Asb. Cpasphalt concrete ACAsphalt concrete pavement ACPasphalt treated base ATBat @ (used only to indicate spacing

or pricing, otherwise spell out).avenue Ave.average avg.

B

back bk.back of pavement seat B.P.S.bearing Brg.begin horizontal curve (Point of Curvature) P.C.begin vertical curve BVCbench mark BMbetween betw. or btwn.bituminous surface treatment BSTbottom bot.boulevard Blvd.bridge Br.bridge drain Br. Dr.



10.1 - A1 - 2 April 1991

building bldg.buried cable BC

C

cast-in-place CIPcast iron pipe (C.I.P.)center, centers ctr., ctrs.centerlinecenter of gravity CGcenter to center ctr. to ctr., c/cCelsius (formerly Centrigrade) Ccement treated base CTBcentimeters cm.class Cl.clearance, clear clr.compression, compressive comp.column col.concrete conc.conduit cond.concrete pavement (Portland Cement Concrete Pavement) PCCPconstruction const. or constr.continuous cont. or contin.corrugated corr.corrugated metal CMcorrugated steel pipe CSPcountersink csk.county Co.creek Cr.cross beam X-Bm.crossing Xingcross section X-Sect.cubic feet CF or cu. ft. or ft.3

cubic inch cu. in. or in.3

cubic yard CY or cu. yd. or yd.3

culvert culv.

D

degrees, angular ° or deg.degrees, thermal C or Fdiagonal(s) diag.diameter diam. ordiaphragm diaph.dimension dim.district Dist.double dbl.drive Dr.

E

each ea.each face E.F.easement ease., esmt.East E.edge of pavement EPedge of shoulder ES



April 1991 10.1 - A1 - 3

endwall EWelectric elect.elevation el. or elev.embankment emb.end horizontal curve (Point of Tangency) P.T.end vertical curve EVCEngineer Engr.equal(s) eq. (as in eq. spaces) or =

(mathematical result)estimate(d) est.excavation exc.excluding excl.expansion exp., expan.existing exist.exterior ext.

F

Fahrenheit Ffar face FFfar side FSfeet (foot) ft. or ’feet per foot ft./ft or ’/’ or ’/ft.field splice F.S.figure, figures fig., figs.flat head F.H.foot kips ft-kipsfoot pounds ft-lbfooting Ftg.forward fwd.freeway Fwy.

G

gallon(s) gal.galvanized galv.galvanized steel pipe GSPgauge ga.General Special Provisions GSPgirder gir.ground gr.guard railing GR

H

hanger hgr.height ht.height (retaining wall) Hhexagonal hex.high strength H.S.high water H.W.high water mark H.W.M.highway Hwy.horizontal horiz.hour(s) hr.hundred(s) hund.



10.1 - A1 - 4 April 1991

I

included. including incl.inch(es) in. or ”inside diameter I.D.inside face I.F.interior int.intermediate interm.invert inv.

J

joint jt.junction jct.

K

kilometer(s) km.kilopounds kips, K.

L

layout LOleft lt.length of curve L.C.linear feet L.F.longitudinal longit.lump sum L.S.

M

maintenance maint.malleable mall.manhole MHmanufacturer mfr.maximum max.mean high water MHWmean higher high water MHHWmean low water MLWmean lower low water MLLWmeters m.mile(s) mi.miles per hour mphmillimeters mm.minimum min.minute(s) min. or ’miscellaneous misc.modified mod.monument Mon.

N

National Geodetic Vertical Datum N.G.V.D.near face NFnear side NSNorth N.Northbound NBnot to scale NTSnumber; numbers #, No.; Nos.



April 1991 10.1 - A1 - 5

O

original ground O.G.ounce(s) oz.outside diameter O.D.outside face O.F.out to out O to Oovercrossing O-Xingoverhead OH

P

page; pages p.; pp.pavement pav’t.pedestrian Ped.per cent %pivot point PPPlans, Specifications and Estimates PS&Eplate or PLpoint pt.point of compound curve PCCpoint of curvature P.C.point of intersection P.I.point of reverse curve PRCpoint of tangency P.T.point of vertical curve PVCpoint of horizontal curve POCpoint of tangent POTpolyvinyl chloride PVCportland cement concrete PCCpound, pounds lb., lbs., #pounds per square foot psf, lbs./ft.2,lbs./ ’,#/ ’pounds per square inch psi, lbs./in.2, lbs./ ”,#/ ”power pole PPprecast P.C.pressure pres.prestressed P.S.prestressed concrete pipe P.C.P.Puget Sound Power and Light P.S.P.&L.

Q

quantity quant.quart qt.

R

radius R.railroad RRrailway Rwy.Range R.regulator reg.reinforced, reinforcing reinf.reinforced concrete RCreinforced concrete box RCBreinforced concrete pipe RCPrequired req’d.retaining wall Ret. Wall



10.1 - A1 - 6 April 1991

revised (date) rev.right rt.right of way R/Wroad Rd.roadway rdwy.route Rte.

S

seconds sec. or ”Section (map location) Sec.Section (of drawing) Sect.sheet sht.shoulder shldr., shld. or sh.sidewalk SW, sdwkSouth S.southbound SBspace(s) spa.splice spl.specification spec.square foot (feet) sq. ft. or ft.2

square inch sq. in. or in.2

square yard SY, sq. yd. or yd.2

station Sta.standard std.stiffener stiff.stirrup stirr.street St.structure, structural str.support supp.surface, surfacing surf.symmetrical symm.

T

tangent Tan. or T.telephone Tel.temporary temp.test hole T. H.thick(ness) th.thousand Mthousand feet board measure MBMton(s) T.total tot.township T.transition trans.transportation transp.transverse transv.treatment tr.typical typ.

U

ultimate ult.undercrossing U-Xing



April 1991 10.1 - A1 - 7

V

variable, varies var.vertical vert.vertical curve BVvitrified clay pipe VCPvolume vol. or V

W

water surface W.S.weight(s) wt.welded steel pipe WSPswelded wire fabric W.W.F.West W.Willamette Meridian W.M.wing wall W.W.with w/without w/o

Y

yard, yards yd., yds.year(s) yr.

10-1-A1:V:BDM10



April 1991 10.1 - A2

Structural SteelFlat pieces of steel are termed plates, bars, sheets, or strips, depending on their dimensions. Barsand plates aregenerally classified as follows:

Bars: up to 6 inches wide, .203 in. (3/16 inch) and over in thickness6 inches to 8 inches wide, .230 in. (7/32 inch) and over in thickness

Plates: over 8 inches wide, .230 in. (7/32 inch) and over in thicknessover 48 inches wide, .180 in. (11/64 inch) and over in thickness

Thinner pieces up to 12 inches wide are strips and over 12 inches are sheets. A complete table of clasificationmay be found in the AISC Manual of Steel Construction, 8th Ed. page 6-3.

The following table shows the usual method of labeling some of the most frequently used structural steel shapes.Note that the inches symbol (″) is omitted, but the foot symbol (′) is used.



April 1991 10.1 - A3

Footing LayoutThe Footing Layout is a plan of the bridge limiting the details shown to those needed to locate the footings. Theintent of the footing layout is to minimize the possibility of error at this initial stage of construction. Other relatedinformation and/or details such as pile locations, pedestal sizes, and column sizes are considered part of the pierdrawing and should not be included in the footing layout.

The Footing Layout should be shown on the layout sheet if room allows. It need not be in the same scale. Whenthe general notes and footing layout cannot be included on the first (layout) sheet, the footing layout should thenbe included on the second sheet.

Longitudinally, footings should be located using the survey line to reference such items as the footing, centerlinepier, centerline column, or centerline bearing, etc., as shown on the pier details sheet.

Appendix 10.5-B1-1 is an example of a footing layout showing:

The basic information needed.

The method of detailing from the survey line.

Notes:

1. When seals are required, their locations and sizes should be clearly indicated on the footing layout.

2. This example shows a complicated geometry as the result of the combined efforts of a horizontal curve andthe presence of the sharp skew. This is the reason for the odd dimensions shown in factuions of an inch. Inmost designs the footing layout would be much simpler.

10-1-A3:V:BDM10

August 1998 11.0-i


Quantities Contents

Page

11.1 General Considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11.1-1

11.1.1 Cost Estimating Quantities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1A. Conceptual Stage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1B. Preliminary Plan Stage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1C. Design Stage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1D. Final Contract Quantities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

11.1.2 Not Included in Bridge Quantities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

11.2 Computation of Quantities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11.2-1

11.2.1 Responsibilities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1A. Design Unit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1B. Bridge Projects Unit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

11.2.2 Procedure for Computation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

11.2.3 Data Source . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

11.2.4 Accuracy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1A. Preliminary Quantities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1B. Final Quantities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

11.2.5 Excavation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2A. Structure Excavation, Class A . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2B. Special Excavation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5C. Shaft Excavation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

11.2.6 Shoring or Extra Excavation, Class A . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

11.2.7 Piling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

Appendix A11.2-A1 Not Included in Bridge Quantities List11.2-A2 Bridge Quantities Form

P:DP/BDM11

August 1998 11.1-1


Quantities General Considerations


The quantities of the various materials involved in the construction of a project are needed for determiningthe estimated cost of the project and for establishing a base for the contractor’s bid and payment.

11.1.1 Cost Estimating Quantities

Quantities for determining cost estimates are often necessary during various stages of project developmentand required at the completion of the Contract Plans. These quantities are calculated from the bestinformation available at the time (see Chapter 11.2.3). The policy regarding the preparation of quantitycalculations is as follows:

A. Conceptual Stage

During the conceptual stage of a project, estimated quantities may be required to arrive at anestimated cost. The need for quantities will be determined by the Bridge Projects Unit.

B. Preliminary Plan Stage

Upon completion of the preliminary plan, estimated quantities may be required to arrive at anestimated cost. The need for quantities will be determined by the Bridge Projects Unit.

C. Design Stage

If requested, quantity calculations shall be made, reviewed, and submitted to the Bridge Projects Unitby the Bridge Design Unit as the design progresses. The first submittal of estimated quantities shallbe made as soon as the major dimensions of the structure are determined. As refinements in thedesign are made, quantities varying more than 10 percent from those previously submitted shall beresubmitted.

D. Final Contract Quantities

Upon completion of structural design and plans, the quantities of materials involved in theconstruction of the project shall be computed.

11.1.2 Not Included in Bridge Quantities

Items of work which appear in the bridge plan sheets, but for which details, specifications, and quantitiesare supplied by the district, shall be listed in the “Not Included in Bridge Quantities List” (Form 230-038).This list is required for every bridge, even if no items of work are in the Plans that are in this category.(In this case, fill out the bridge information at the top of the form and write “NONE” across the form.)This form is transmitted to other agencies for further processing. Particular care shall be taken in thepreparation of this list as omissions result in inaccurate quantities and frequently necessitate constructionchange orders.

11-1:P:BDM11

August 1998 11.2-1


Quantities Computation of Quantities

11.2 Computation of Quantities

11.2.1 Responsibilities

A. Design Unit

The Design Unit is responsible for alerting the Bridge Projects Unit when alterations are made afterturn-in to the design features and quantities which will affect the cost of the structure.

B. Bridge Projects Unit

The Bridge Projects Unit will not be responsible for computing quantities. However, they will beresponsible for ensuring that the quantities listed in the Bid Proposal correspond to those receivedfrom the Design Unit.

11.2.2 Procedure for Computation

Quantities are to be computed and checked independently. The originator and checker shall separatelysummarize their results on Form 230-031 “Bridge Quantities” in the units shown thereon. The twosummaries shall be submitted to the Design Unit Supervisor for comparison. The originator and checkershall use identical breakdowns for each quantity. For example, the originator’s figures for excavation foreach of Piers 1, 2, and 3 should be compared separately against the corresponding figures made by thechecker. When the desired accuracy is achieved, a Supervisor’s Bridge Quantities form shall be prepared.(This form is the same as previously mentioned except that it is labeled “Supervisor’s Bridge Quantities”and is completed by the supervisor or his designee. If the supervisor elects, the originator’s or thechecker’s Bridge Quantities form may be designated as “Supervisor’s Bridge Quantities.”) This form isused by the Bridge Projects Unit to prepare the final bridge cost estimate.

All quantity calculations and bridge quantities forms are to be filed in the job file. All subsequentrevisions shall be handled in the same manner as the original quantities. On the “Bridge Quantities” form,any revision to the original figure should not be erased but crossed out and replaced by the new figureusing a different colored pencil. If there are too many revisions, the old summary sheet should be markedvoid, left in the file, and a new sheet made out, marked “Revised,” dated, and the original forwarded to theBridge Projects Unit.

Mistakes in quantities can be very costly to the department. The originator and checker must account forall items of work on the “Bridge Quantities” form but must also be careful to enter an item of work onlyonce (e.g., concrete or steel rebar in the superstructure should not be entered both in the lump sumsuperstructure breakdown and in the unit bid item quantity).

11.2.3 Data Source

Quantities of materials for use in preliminary cost estimates can often be obtained from the materialscalculated for previous similar designs. This information is available from the Bridge Projcts Unit.

11.2.4 Accuracy

A. Preliminary Quantities

Quantities used for cost estimates during the conceptual stage of the design are expected to havean accuracy of ±10 percent. The first iteration of quantities, after the preliminary plan has beencompleted, is expected to have an accuracy of ±5 percent.

11.2-2 August 1998



B. Final Quantities

Final quantities to be listed in the Special Provisions and Bid Proposal sheet are to be calculated tohave an accuracy of ±1 percent, including bar list.

11.2.5 Excavation

A. Structure Excavation, Class A

Excavation necessary for the construction of bridge piers and reinforced concrete retaining walls isclassified as Structure Excavation, Class A. Payment for such excavation is generally at the unitcontract price per cubic yard. The quantity of excavation to be paid for is measured as outlined inSection 209.4 of the Standard Specifications. Computation of the quantity shall follow the sameprovisions. Designers shall familiarize themselves with this section of the Standard Specifications.Any limits for structure excavation not conforming to the limits specified in the StandardSpecifications shall be shown in the Plans.

Structure excavation for footings and seals shall be computed using a horizontal limit of 1 foot0 inches outside and parallel to the neat lines of the footing or seal or as shown in the Plans. Theupper limit shall be the ground surface or stream bed as it exists at the time the excavation is started.See Figure 11.2.6-1(A), (B), and (C).

Figure 11.2.6-1

August 1998 11.2-3



Structure excavation for the construction of wing walls shall be computed using limits shown inFigure 11.2.6-2.

Figure 11.2.6-2

Figure 11.2.6-3

11.2-4 August 1998



When bridge approach fills are to be constructed in the same contract as the bridge and the foundationconditions do not require full height fills to be placed prior to the construction of the pier, the approach fillis constructed in two stages, i.e., constructed up to the bottom of footing or 1 foot above the bottom offooting and then completed after the bridge construction. (The Materials Laboratory shall be consulted onthe staging method.) The structure excavation shall be computed from the top of the first stage fill.

The bottom of a spread footing will be placed 1 foot 0 inches below the top of the first stage fill. SeeFigure 11.2.6-4(A). The bottom of footings supported on piling will be placed at the top of the first stagefill; therefore, no structure excavation is required (see Figure 11.2.6-4(B)).

The limits for stage fills shall be shown in the Plans with the structure excavation, if any.

Figure 11.2.6-4

Prior to pier construction, when (1) a full height fill with or without surcharge is required for settlement,or (2) the original ground line is above the finish grade line, structure excavation shall be computed to1 foot 0 inches below the finish grade (pavement) line (see Figure 11.2.6-5).

Figure 11.2.6-5

August 1998 11.2-5



B. Special Excavation

The excavation necessary for placement of riprap around bridge piers is called Special Excavation(see Figure 11.2.6-6).

Special excavation shall be computed from the top of the seal to the existing stream bed or groundline along the slopes indicated in the Plans. Special excavation will only include excavation outsidethe limits of structure excavation.

The limits for special excavation shall be shown in the Plans.

Figure 11.2.6-6

C. Shaft Excavation

Excavation necessary for the construction of shaft foundations is generally measured by the cubicyard and paid for at the unit contract price per cubic yard for “Soil Excavation for Shaft IncludingHaul.”

The usual limits for computing shaft excavation shall be the neat lines of the shaft diameter and fromthe bottom elevation of the shaft as shown in the Plans to the ground surface as it exists at the time ofshaft excavation.

The methods of measurement and payment and the limits for shaft excavation shall be specified in theSpecial Provisions.

11.2.6 Shoring or Extra Excavation, Class A

All excavation in the dry which requires workmen to enter the excavated area and which has a depth of4 feet or more is required to be shored, unless the earth face is excavated at its angle of repose (ExtraExcavation).

All excavation which is 15 feet or less from the edge of a traveled pavement is also required to be shored.All excavation adjacent to railroad tracks shall also be shored.

Cofferdams are required for all underwater excavation or excavation affected by ground water.

Shoring, cofferdams, or caissons or extra excavation required for the construction of bridge footings andreinforced concrete retaining walls constructed in the wet or dry is classified as Shoring or ExtraExcavation, Class A.

11.2-6 August 1998



For the purpose of estimating the cost for cofferdams or for shoring or extra excavation, Class A, it isnecessary to compute the peripheral area of an assumed sheet pile enclosure of the excavated area.

While payment for Shoring or Extra Excavation, Class A, is made at a lump sum contract price, the costsare a function of overall height of excavation. In general, each side of the excavation for each pier shall becategorized into an average overall height range as shown on Form 230-031 (i.e., less than 6 feet, 6 to 10feet, 10 to 20 feet, or greater than 20 feet), the area for the side computed using the appropriate widthtimes the average overall height, the overall area for the side shall be entered in the category that matchesthe side’s average overall height. These calculations are required for each pier of the bridge as applicable.See accompanying Figure 11.2.6-7 and sample calculation.

For excavation in the dry, the peripheral area shall be the perimeter of the horizontal limits of structureexcavation times the height from the bottom of the footing to the ground surface at the time of excavation.

For excavation in water, the peripheral area shall be the perimeter of the horizontal limits of structureexcavation times the height from the bottom of the seal to 2 feet above the seal vent elevation.

For shaft-type foundations, it is not necessary to compute the area for shoring because the cost for shoringis normally included in the contract price for shaft excavation.

Figure 11.2.6-7

August 1998 11.2-7



Sample Calculation:

For this pier (Figure 11.2.6-7):

Side A: average height = (4 + 6)/2 = 5 feetwidth = 15 feetarea = 5 × 15 = 75 square feet

Side B: average height = (6 + 15)/2 = 10.5 feetwidth = 20 feetarea = 10.5 × 20 = 210 square feet

Side C: average height = (10 + 15)/2 = 12.5 feetwidth = 15 feetarea = 12.5 × 15 = 187.5 square feet

Side D: average height = (4 + 10)/2 = 7 feetwidth = 20 feetarea = 7 × 20 = 140 square feet

For this example

height category area

less than 6 feet 75 square feet

6 feet to 10 feet 140 square feet

10 feet to 20 feet 210 + 188 = 398 square feet

greater than 20 feet N.A.

These numbers would be entered on Form 230-031 as follows:

Std. UnitItem Item Item ofNo. Use Description Quant. Meas.

4012 Std. Item Shoring or (Enter Total L.S.Extra Excavation, for Bridge Here)

Class ADry:

Average Overall Height

6 ft. 10 ft.*Pier 6 ft. to 10 ft. to 20 ft. 20 ft.*

__Example_ _ 75 _ S.F. _ 140 _ S.F. _398(11.5*) S.F. __ — _ S.F.

__________ __________ S.F. __________ S.F. __________ S.F.__________ S.F.

__________ __________ S.F. __________ S.F. __________ S.F.__________ S.F.

__________ __________ S.F. __________ S.F. __________ S.F.__________ S.F.

*Indicate Average Height

11.2-8 August 1998



11.2.7 Piling

The piling quantities are to be measured and paid for as outlined in Section 6-05.3(1)D Test Piles, andmeasurement and payment Sections 605.4 and 6-05.5 of the Standard Specifications. Computation ofpiling quantities shall follow the same provisions. Designers shall familiarize themselves with thesesections of the Standard Specifications.

Timber test piles are driven outside the structure limits and are extra or additional piling beyond therequired number of production piling.

Concrete or steel test piles are driven within the structure limits and take the place of production piling.In this case, the number of production piling is reduced by the number of test piling.

The quantity for “Furnishing _____ Piling _____” is the linear feet of production piling below cut-off tothe “estimated” pile tip (not “minimum” tip) shown in the soils report. (Does not include test piles.)

The quantity for “Driving _____ Piling _____” is the number of production piling driven. (Does notinclude test piles.)

Pile tips are required if so stated in the soils report. The tips on the test piles are incidental to the test pile;therefore, the number of pile tips reported on the Bridge Quantities Form 230-031 should not include thenumber of pile tips required on the test piles.

DP:BDM11

August 1998 11.2-A1


Quantities Not Included in Bridge Quantities List


Not Included InBridge Quantities List

Environmental And Engineering Service CenterBridge and Structures Office

SR Job Number Project Title

Designed By Checked By Date Supervisor

Type of Structure

The following is a list of items for which the Bridge and Structures Office is relying on the Region to furnishplans, specifications and estimates.

1.

2.

3.

4.

5.

6.

7.

8.

9.

10.

11.

12.

13.

14.

15.

16.

17.

11.2-A1 Not Included in Bridge Quantities Form

August 2000 11.2-A2-1


Quantities Bridge Quantities Form

11.2-A2 Bridge Quantities Form

Bridge and StructuresEnglish Metric

St. Item No. Item Use Item Description Quantity Unit ofMeasure

0001(E)0001(M)

Std. Item Mobilization

L.S.

L.S.

00610061

GSP Item Removing Portion of Existing Bridge

Type Area

Less than 12”/305 mm long: Greater than 12”/305 mm long:

Number Diameter Number Diameter Length

Number

Inch/mm

Inch/mm

Inch/mm

Inch/mm

Inch/mm

Inch/mm

Inch/mm

Inch/mm

Inch/mm

Inch/mm

Inch/mm

Inch/mm

Less than 12”/305 mm long: Greater than 12”/305 mm long:

Length

LF/M

LF/M

LF/M

LF/M

LF/M

LF/M

Drilled Holes:

Diameter Number Diameter

Core Drilled Holes:

Type Area

SF/SM

SF/SM

00710071 GSP Item Removing Existing Bridge

L.S.

L.S.

Sp. Prov. Removing Temporary Structure

Type Area SF/SM

CY/CM4006/8331 Std. Item Structure Excavation Class A Incl. HaulUnsuitable:

Pier Soil

CY/CM

CY/CM

CY/CM

CY/CM

Cofferdam:Pier Soil

CY/CM

CY/CM

CY/CM

CY/CM

CY/CM

CY/CM

CY/CM

CY/CM

Rock

4010/8835 GSP Item Special Excavation CY/CMPier Soil

CY/CM

CY/CM

CY/CM

CY/CM

Page 1 of 6

Indicate Unit of Measure:


Bridge Quantities

11.2-A2-2 August 2000



SF/SM

SF/SM

SF/SM

SF/SM

SF/SM

SF/SM

SF/SM

SF/SM

SF/SM

SF/SM

SF/SM

SF/SM

SF/SM

SF/SM

SF/SM

SF/SM

SF/SM

SF/SM

SF/SM

SF/SM

SF/SM

SF/SM

SF/SM

SF/SM

SF/SM

SF/SM

SF/SM

SF/SM

SF/SM

SF/SM

SF/SM

SF/SM

Sp. Prov. Soil Excavation For Shaft Including Haul


4013/4013 Std. Item Shoring or Extra Excavation Class A L.S.

Pier <6 ft./2 m6 ft./2 m to10 ft./3 m

10 ft./3 m to20 ft./6 m >20 ft./6 m

Dry:AVERAGE OVERALL HEIGHT

Pier <6 ft./2 m6 ft./2 m to10 ft./3 m

10 ft./3 m to20 ft./6 m >20 ft./6 m

Cofferdam:AVERAGE OVERALL HEIGHT

*INDICATE AVERAGE HEIGHT

Each

CY/CM

4030 GSP Item Rock Bolt

Sp. Prov. Rock Excavation For Shaft Including Haul

Sp. Prov. Furnishing and Placing Temp. Casing For

Sp. Prov. Furnishing Permanent Casing For

Sp. Prov. Placing Permanent Casing For

Sp. Prov. CSL Access Tube

CY/CM

LF/M

LF/M

Each

LF/M

LB/KG

CY/CM

LF/M

4151/8426 Std. Item St. Reinf. Bar For Shaft

Sp. Prov. Conc. Class 4000P For Shaft

GSP Item Excavation For Piling

4055/8355 Std. Item Preboring For Pile

4060/4060 Std. Item Furnishing and Driving Concrete Test Pile

4070/8363 Std. Item Furnishing Concrete Piling -

LF/M

Each

LF/M

4080/4080 Std. Item Driving Concrete Pile -

4085/4085 Std. Item Furnishing and Driving Steel Test Pile

Each

4090/8373 Std. Item Furnishing Steel Piling

Each

4095/4095 Std. Item Driving Steel Pile

LF/M

4100/4100 Std. Item Furnishing and Driving Timber Test Pile

Each

4105/8381 Std. Item Furnishing Timber Piling - Untreated

Each

4106/8383 Std. Item Furnishing Timber Piling - Creosote Treated

LF/M

LF/M

Page 2 of 6

Diameter

Diameter

*

**

*

--

--

--

--

--

----

Each4108/4108 Std. Item Driving Timber Pile - Untreated

Each4110/4110 Std. Item Driving Timber Pile - Creosote Treated

Each4116/4116 Std. Item Pile Splice - Timber

EachSp. Prov. Pile Tip--

--


Diam. Shaft

Diam. Shaft

Diam. Shaft

August 2000 11.2-A2-3



Page 3 of 6


LF/M4120/8393 Std. Item Furnishing Prestressed Hollow Concrete Piling

Each4130/4130 Std. Item Placing Prestressed Hollow Concrete Pile

Each4140/4140 Std. Item Driving Prestressed Hollow Concrete Pile

LF/M4145/4145 Sp. Prov. Pile Loading Test

LB/KG4147/8410 Std. Item Epoxy-Coated St. Reinf. Bar For

No. of Tests Pile SizeEach Ton/Tonne

LB/KG4147/8410 Std. Item Epoxy-Coated St. Reinf. Bar For Traffic Barrier

LB/KG4148/8412 Std. Item Epoxy-Coated St. Reinf. Bar For Bridge

LB/KG4149/8420 Std. Item St. Reinf. Bar For Bridge

LB/KG4151/8426 Std. Item St. Reinf. Bar For Traffic Barrier

LB/KG4151/8426 Std. Item St. Reinf. Bar For

SY/SM4165/8428 Std. Item Wire Mesh

CY/CMGSP Item Conc. Class

CY/CM4322/8452 Std. Item Conc. Class 4000/28 for Bridge

CY/CM4202/8442 Std. Item Conc. Class 4000/28 for Traffic Barrier

CY/CM4202/8442 Std. Item Conc. Class 4000/28 for





CY/CM4324/8468 Std. Item Conc. Class 4000W/28W for Bridge

CY/CM4204/8466 Std. Item Conc. Class 4000W/28W for

CY/CM4183/4183 GSP Item Conc. Class EA

CY/CM4185/4185 GSP Item Conc. Class HE

CY/CMStd. Item Conc. Class

CY/CM4184/4184 GSP Item Cylinder Concrete

LS

SY/SM4188/4188 GSP Item Fractured Fin Finish

LB/KG4230/4230 Std. Item Structural Carbon Steel

LB/KG4235/4235 Std. Item Structural Low Alloy Steel

LB/KG4240/4240 Std. Item Structural High Strength Steel

LB/KG4246/4536 Std. Item Cast Steel

LB/KG4251/8540 Std. Item Forged Steel

--

--

LB/KG4256/8546 Std. Item Cast Iron

LB/KG4261/8549 Std. Item Malleable Iron

LB/KG4267/8552 Std. Item Ductile Iron

LB/KG4271/8555 Std. Item Cast Bronze

CY/CM4166/8430 Std. Item Lean Concrete


11.2-A2-4 August 2000




MBM/M34280/8560 Std. Item Timber and Lumber - Untreated

MBM/M34282/8582 Std. Item Timber and Lumber - Creosote Treated

MBM/M34284/8584 Std. Item Timber and Lumber - Salts Treated

LS4300/4300 Std. Item Superstructure

LF/M4311/4311 Std. Item Roadway Deck

LF/M4390/8595 GSP Item Electrical Conduit

Bridge Plan Area SF/SM

Bridge Plan Area SF/SM

Diameter Inch Length LF/M

LF/M4400/8600 GSP Item Steel Handrail

LF/M4405 GSP Item Bridge Rail - Low Fence Type

LF/M4406 GSP Item Bridge Rail - High Fence Type

LF/M4410/8605 GSP Item Bridge Railing Type

Each4420 GSP Item Bridge Grate Inlet

SY/SM4453/4453 GSP Item Pigmented Sealer

SF/SM7169/9572 Sp. Prov. Structural Earth Wall

Sp. Prov.

Sp. Prov.

Page 4 of 6

--

--


August 2000 11.2-A2-5




LB/KGStd. Item Epoxy-Coated Steel Reinforcing Bar

Breakdown of Items for Superstructure or Roadway Deck

LB/KGStd. Item Epoxy-Coated Steel Reinforcing Bar (Traffic Barrier)

LB/KGStd. Item Steel Reinforcing Bar

LB/KGStd. Item Steel Reinforcing Bar (Traffic Barrier)

CY/CMGSP Item Conc. Class

CY/CMStd. Item Conc. Class 4000/28

CY/CMStd. Item Conc. Class 4000/28 (Traffic Barrier)

CY/CMStd. Item Conc. Class 5000/35

CY/CMStd. Item Conc. Class

SY/SMGSP Item Fractured Fin Finish

LB/KGStd. Item Structural Carbon Steel

LB/KGStd. Item Structural Low Alloy Steel

LB/KGStd. Item Structural High Strength Steel

LB/KGStd. Item Cast Steel

LB/KGStd. Item Forged Steel

LB/KGStd. Item Cast Iron

LS

LB/KGStd. Item Malleable Iron

LB/KGStd. Item Ductile Iron

LB/KGStd. Item Cast Bronze

MBM/M3Std. Item Timber and Lumber - Untreated

MBM/M3Std. Item Timber and Lumber - Creosote Treated

MBM/M3Std. Item Timber and Lumber - Salts Treated

MBM/M3Sp. Prov. Glulam Deck Panels

LF/MStd. Item Electrical Conduit

Diameter Inch Length LF/M

LF/MGSP Item Steel Handrail

LF/MGSP Item

LF/MGSP Item

Bridge Rail - Low Fence Type

LF/MStd. Item

Bridge Rail - High Fence Type

LF/MGSP Item

Bridge Railing Type

Each4430/4430 GSP Item

Each4433/4433 Sp. Prov.

Each4434/4434 Sp. Prov.

Each4420/4420 GSP Item

Special Bridge Drain

Modify Bridge Drain

Plugging Existing Bridge Drain

Bridge Grate Inlet

Traffic Barrier

Page 5 of 6

--

--

--

--

--

--

--

--

--

--

--

--

--

--

--

--

--

--

--

--

--

--

--

--

--

--

--

--

--

--

CY/CMStd. Item Conc. Class 4000D/28D


11.2-A2-6 August 2000




LF/MGSP Item Expansion Joint System

Page 6 of 6

Type Length LF/M

Type Length LF/M

Type Length LF/M

LF/M4444/8634 Sp. Prov. Expansion Joint Modification

Type Length LF/M

SY/SMSp. Prov. Polymer Concrete Overlay

L.S.Sp. Prov. Further Deck PreparationVolume CF/CM Avg. Depth Inch/mm

Volume CF/CM Avg. Depth Inch/mm

L.S.4445/4445 GSP Item Bridge Deck Repair

--

--

--

--

--

EachSp. Prov. Pot Bearing

EachSp. Prov. Disc Bearing

EachSp. Prov. Spherical Bearing

EachSp. Prov. Cylindrical Bearing

EachStd. Item Elastomeric Bearing Pad

EachGSP Item Fabric Pad Bearing--

LF/MStd. Item Prestressed Conc. Girder Series W42G/W42MG--




LB/KGStd. Item Prestressing--


SF/SMSp. Prov. Precast Prestressed Slab--

Volume CF/CM Length LF/M



SF/SMSp. Prov. Precast Prestressed Tri Beam--

SF/SMSp. Prov. Precast Prestressed Double Tee Beam--

LF/MSp. Prov. Precast Segment--

Volume CY/CM

Sp. Prov.--

Sp. Prov.--

--

-- SY/SMGSP Item Pigment Sealer

SY/SM4455/8643 GSP Item Membrane Waterproofing (Deck Seal)


CF/M34232/8515 Sp. Prov. Modified Concrete Overlay

SY/SM4233/8516 Sp. Prov. Finishing and Curing Modified Concrete Overlay

SY/SM4456/8644 Sp. Prov. Scarifying Concrete Surface


August 1998 12.0-i


Construction Costs Contents

Page

12.0 Construction Costs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12.1-1

12.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

12.2 Factors Affecting Costs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12.2-1

12.2.1 Type of Structure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

12.2.2 Location of Project Site . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

12.2.3 Size of Project Contract . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

12.2.4 Foundation Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

12.2.5 Sequencing of Project . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

12.3 Development of Cost Estimates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12.3-1

12.3.1 Types . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1A. Prospectus and Design Report Estimates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1B. Preliminary Design Estimates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1C. Estimate Updates During Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1D. Contract Estimates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

12.3.2 Responsibilities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1A. Bridge Projects Unit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

12.3.3 Documentation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

12.3.4 Cost Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2A. General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2B. Square Foot Area . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

Appendix A12.3-A1 Bridge and Structures Estimating Aids12.3-A2 Substructure Estimating Aids12.3-A3 Superstructure Estimating Aids12.3-A4 Miscellaneous Estimating Aids

P:DP/BDM12

August 1998 12.1-1


Construction Costs Introduction

12.0 Construction Costs

12.1 Introduction

The construction costs itemized in Appendix A are to aid the user in estimating the cost of bridge projects.The costs are based on historical data retrieved from recent WSDOT Contracts.

Requests for cost estimates from outside offices should be submitted in writing to the Bridge Projects Unitand a written response will be sent within a reasonable time. Estimates requiring input from the BridgeDesign Section will take longer due to project schedule priorities.

Telephone requests for cost estimates from outside the Bridge and Structures Office shall be referred tothe Bridge Projects Unit.

All cost estimates prepared by the Bridge and Structures Office should have the concurrence of the BridgeProjects Engineer.

12-1:P:BDM12

August 1998 12.2-1


Construction Costs Factors Affecting Costs

12.2 Factors Affecting Costs

12.2.1 Type of Structure

Many factors, as outlined in Section 2.2.3, must be considered in the selection of the type, size, andlocation of a bridge or wall.

Common structures with normal detail will be on the low end and mid-range of costs. Unique or complexstructures will be on the high end.

12.2.2 Location of Project Site

Projects in remote areas or with difficult access will generally be on the high end of the cost range, andsometimes beyond.

12.2.3 Size of Project Contract

Small projects tend to be on the high end of the cost range while large projects tend to be on the low endof the cost range.

12.2.4 Foundation Requirements

Foundation requirements greatly affect costs. Water crossings requiring seals and piles are generally veryexpensive. Scour requirements can push the costs even higher. The earlier foundation information can bemade available the more accurate the cost estimate will be. The Bridge Projects Unit should be madeaware of unusual foundation requirements or changes to foundation type as soon as possible for updatingof the estimate.

12.2.5 Sequencing of Project

Projects with stage construction, detours, temporary construction, etc., will be more expensive.

12-2:P:BDM12

August 1998 12.3-1


Construction Costs Development of Cost Estimates

12.3 Development of Cost Estimates

Estimates prepared by the Bridge and Structures Office shall include mobilization but not sales tax,engineering, construction contingencies, or inflation.

12.3.1 Types

A. Prospectus and Project Summary Estimates

Conceptual cost estimates are prepared when little information about the project is available. Use theconstruction costs in Appendix A, assuming the worst case conditions, unless actual conditions areknown. An example of a worst case condition is pile supported footings. In remote areas, or for smallprojects, use the high end of the cost range. Use mid-range costs for usual conditions.

To cover unforeseen project modifications, add a 20 percent estimate contingency to a prospectusestimate and a 10ˇpercent estimate contingency to a project summary estimate. These contingenciescan be adjusted depending on the preliminary information available.

B. Preliminary Design Estimates

Preliminary design estimates are prepared during the preliminary design stage when the type andsize of bridge is known. Limited foundation information is sometimes available at this stage. Theconstruction costs in Appendix A shall be used with an appropriate inflation factor, assuming theworst case conditions, unless foundation conditions are known, along with a minimum of 10 percentcontingency to cover scope creep.

For bridge rehabilitation projects, add a minimum 20 percent contingency amount to specific items,such as mechancical rehabilitation and structural steel repair, to cover potential increases in costs thatoften surface after indepth inspections are completed.

C. Estimate Updates During Design

During the design period, the designer should keep the Bridge Projects Unit informed of significantchanges to the design that might affect the cost. Examples of significant changes are: deeper thanexpected footing and seals, use of piles when none were expected, change of substructure types, andchanges to superstructure. This is a critical element in the project budgeting process.

D. Contract Estimates

The contract estimate is prepared by the Bridge Projects Unit after the Plans and Final Quantitieshave been submitted to the Bridge Projects Unit for final processing. The contract estimate is pre-pared using the quantities furnished by the Design Section, unit bid prices from Appendix A, otherhistorical data, and the judgment of the engineer preparing the estimate. Unique, one-of-a-kindprojects require special consideration and should include an appropriate construction costcontingency.

12.3.2 Responsibilities

A. Bridge Projects Unit

The Bridge Projects Unit is responsible for preparing the prospectus, project summary, preliminary,and final contract estimates and updating the preliminary estimate as needed during the design phaseof the project.

The Bridge Projects Unit assists the regions and outside agencies, such as counties and cities, toprepare conceptual design report and preliminary estimates when requested in writing.

12.3-2 August 1998



B. Designer

The designer is responsible for providing preliminary quantities and final quantities to the BridgeProjects Unit to aid in the updating of preliminary estimates and the preparation of contract estimates.

12.3.3 Documentation

Whenever a cost estimate is prepared by the Bridge and Structures Office for an outside office, a CostEstimate Summary sheet (Form 230-040) shall be filled out by the engineer preparing the estimate. TheCost Estimate Summary shall be maintained in the Job File. During the design stage, the summary sheetshall be maintained by the Structural Design Unit. It is the design unit supervisor’s responsibility toensure the summary sheet is up to date when the job file is submitted to the Bridge Projects Unit.

12.3.4 Cost Data

A. General

The bridge costs summarized in Appendix A represent common highway, railroad, and watercrossings. Consult the Bridge Projects Engineer for structures spanning across large rivers or canyonsand other structures requiring high clearances or special design and construction features.

The square foot costs are useful in the conceptual and preliminary design stages when details orquantities are not available. The various factors affecting costs as outlined in Section 12.2 must beconsidered in selecting the square foot cost for a particular project. As a general rule, projectsincluding none or few of the high-cost factors will be close to the mid-range of the cost figures.Projects including many of the cost factors will be on the high side. The user must exercise goodjudgment to determine reasonable costs. During the preliminary stage, it is better to be on the conser-vative side for budgeting purposes.

B. Square Foot Area

Compute the square foot area to be used with the square foot cost shall be computed as follows:

Bridge Widenings and New Bridges

The area of bridges is based on the actual width of the new portion of the roadway slab constructed(measured to the outside edge of the roadway slab) times the length, measured from end of wingwallto end of wingwall, end of curtain wall to end of curtain wall, or back to back of pavement seat ifthere are no wingwalls or curtain walls. Wingwalls are defined as walls without footings which arecast monolithically with the bridge abutment wall and may extend past the abutment footing. Curtainwalls are defined as walls that are cast monolithically with the bridge abutment wall and footing andonly extend to the edge of footing.

Bridge Rail Replacement

The bridge rail and curb removal is based on the total length of the rail and curb removed.

Bridge Lengths With Unequal Wingwalls

If a bridge has wingwalls or curtain walls of unequal length on opposite sides at a bridge end orwingwalls or curtain walls on one side of a pier only, the length used in computing the square footarea is the average length of the walls. If the wingwalls are not parallel to the centerline of the bridge,the measurement is taken from a projected line from the end of the wingwall normal to the centerlineof the roadway.

August 1998 12.3-3



Retaining Walls

If retaining walls (walls that are not monolithic with the abutment) extend from the end of the bridge,the cost of these walls is computed separately. The area of the wall is based on the height from the topof footing to the top of the wall.

DP:BDM12

July 2000 12.3-A1-1


Construction Costs Bridge and Structures Estimating Aids

BRIDGE AND STRUCTURES

(Note: Unit struture costs include mobilizationbut do not include sales tax, engineering, or contingency)

LOW AVERAGE HIGH ∆∆

PRESTRESSED CONCRETE GIRDERSSPAN 50-140 FT.

Water Crossing w/piling SF $ 75.00 $ 90.00 $ 110.00

Water Crossing w/spread SF 70.00 80.00 100.00footings

Dry Crossing w/piling SF 75.00 85.00 100.00

Dry Crossing w/spread SF 60.00 70.00 90.00footings

REINFORCED CONCRETE ANDPOST-TENSIONED CONCRETE BOXGIRDER-SPAN 50-200 FT.

Water Crossing w/piling SF 80.00 100.00 130.00

Water Crossing w/spread SF 75.00 95.00 120.00footings

Dry Crossing w/piling SF 80.00 100.00 120.00

Dry Crossing w/spread SF 65.00 90.00 110.00footings

REINFORCED CONCRETE FLAT SLAB SF 45.00 60.00 80.00SPAN 20-60 FT.

PRESTRESSED CONCRETE SLABS SF 50.00 70.00 95.00SPAN 13-69 FT.

PRESTRESSED CONCRETE DECKED SF 80.00 90.00 115.00BULB-TEE GIRDERSPAN 40-115 FT.

STEEL GIRDER — SPAN 60-400 FT. SF 105.00 125.00 160.00

STEEL TRUSS — SPAN 300-700 FT. SF 135.00*

STEEL ARCH — SPAN 30-400 FT. SF 145.00*

CONCRETE BRIDGE REMOVAL SF 10.00 25.00 40.00

WIDENING EXISTING CONCRETE SF 100.00 130.00 185.00BRIDGES (Including Removal)

RAILROAD UNDERCROSSING LF $7,000.00*(Steel Underdeck Girder)— SINGLE TRACK $8,000.00*(Steel Thru-Girder)

RAILROAD UNDERCROSSING LF $11,000.00*— DOUBLE TRACK

12.3-A1-2 July 2000


Construction Costs Bridge and Structures Estimating Aids

BRIDGE AND STRUCTURES

(Continued)

LOW AVERAGE HIGH ∆∆PEDESTRIAN BRIDGE SF $ 70.00 $ 80.00 $ 90.00— REINFORCED CONCRETE

REINFORCED CONCRETE RIGID SF 80.00*FRAME (TUNNEL)

REPLACING EXISTING CURBS & LF 100.00 150.00 200.00BARRIER WITH NEW JERSEYBARRIER (INCLUDING REMOVAL)

REINFORCED CONCRETE SF 35.00 50.00 65.00RETAINING WALL(EXPOSED AREA)

SOLDIER PILE TIEBACK WALL SF 100.00 120.00 150.00(EXPOSED AREA)

MSE WALLPRECAST CONCRETE PANELS SF 13 24 35

MSE WALLWELDED WIRE SF 11 18 25

MSE WALLCIP CONCRETE FACE SF 30 35 40

SOIL NAIL WALL SF 20 30 40

CONCRETE FACINGPERMANENT GEOSYNTHETIC WALL SF 11 15 30

CONCRETE CRIB WALLCONCRETE HEADERS SF 20 30 40

*Based on limited cost data. Check with the Bridge Support Engineer.

Bridge areas are computed as follows:

Typical Bridges: Width x Length

Width: Total width of deck, including portion under the barrier.

Length: Distance between back of pavement seats, or for a bridge having wingwalls, 3″-0″behind the top of the embankment slope; typically end of wingwall to end of wingwall,reference Standard Plans H9.

Special Cases:

Widenings — Actual area of new construction.

Tunnel — Outside dimension from top of footing to top of footing over the tunnel roof,i.e., including walls and top width.

∆∆ For small jobs (less than $100,000), use the high end of the cost range as a starting point.

P65:DP/BDM12

July 2000 12.3-A2-1


Construction Costs Substructure Estimating Aids

SUBSTRUCTURE

BID ITEMS UNIT COST/UNIT ∆∆

Structure Excavation Class A Incl. HaulEarth Cu. Yd. $ 10.00 — $ 25.00Rock Cu. Yd. 100.00 — 200.00Inside Cofferdam — Earth Cu. Yd. 20.00 — 30.00

— Rock Cu. Yd. 100.00 — 175.00

Shoring Extra Excavation Class ADry — Depth under 6′ Sq. Ft. 2.00 — 6.00Dry — 6′ - 10′ Sq. Ft. 6.00 — 10.00Dry — 10′ - 20′ Sq. Ft. 10.00 — 20.00

Cofferdam Sq. Ft. 20.00 — 30.00

Preboring For Standard Piles Lin. Ft. 25.00 — 45.00

Furnishing & Driving Test Piles

Concrete Each 3,000.00 — 5,000.00Steel Each 3,000.00 — 4,000.00Timber Each 1,500.00 — 2,500.00

Furnishing PilingConc. _____ Diam. Lin. Ft. 30.00 — 40.00Steel — TYP HP 12x53 Lin. Ft. 25.00 — 30.00Timber — Creosote Treated Lin. Ft. 8.00 — 10.00Timber — Untreated Lin. Ft. 7.00 — 9.00

Pile TipCIP Concrete (Steel Casing — Short Tip) Each 150.00 — 200.00CIP Concrete (Steel Casing — 10 Stinger) Each 4,000.00 — 5,000.00Steel (H-Pile) Each 100.00 — 200.00Timber (Arrow Tip) Each 20.00 — 40.00

Driving Piles (40′ - 70′ Lengths)Concrete _____ Diam. Each 400.00 — 800.00Steel Each 300.00 — 700.00Timber Each 200.00 — 400.00

ShaftsSoil Excavtion For Shaft Including Haul Cu. Yd. 200.00 450.00Rock Excavation For Shaft Including Haul Cu. Yd. 350.00 650.00Furnishing and Placing Temp. Casing For Shaft Lin. Ft. 100.00 300.00Furnishing Permanent Steel Casing For Shaft Lin. Ft. 100.00 600.00Placing Permanent Steel Casing For Shaft Each 1,000.00 1,500.00Shoring or Extra Excavation cl. A — Shaft Est. 10,000.00 25,000.00Conc. Class 4000P For Shaft Cu. Yd. 125.00 200.00

12.3-A2-2 July 2000


Construction Costs Substructure Estimating Aids

St. Reinf. Bar For Shaft Lb. 40.00 50.00CSL Access Tubes Lin. Ft. 1.50 3.50Force Account Remvoing Obstrucitons For Shaft Est. 10% of all of above shaft ______

St. Reinf. Bar For Bridge Lbs. 0.45 — 0.60

Epoxy-Coated St. Reinf. Bar For Bridge Lbs. 0.60 — 0.80

Conc. Class 4000W Cu. Yd. 100.00 — 150.00

Conc. Class 4000P Cu. Yd. 100.00 — 150.00

Conc. Class 4000 (Footings) Cu. Yd. 300.00 — 400.00

Conc. Class 4000 (Abut. & Ret. Walls) Cu. Yd. 300.00 — 400.00

Conc. Class 5000 Cu. Yd. 350.00 — 450.00

Lean Concrete Cu. Yd. 100.00 — 130.00

Concrete Class 4000 P (CIP Piling) Cu. Yd. 100.00 — 175.00

P65:DP/BDM12

July 2000 12.3-A3-1


Construction Costs Superstructure Estimating Aids

SUPERSTRUCTURE


Elastomeric Bearing PadsGirder Seat Each $ 80.00 — $ 100.00Girder Stop Each 50.00 — 70.00

Spherical and Disc, Bearings Kip 7.00 — 10.00(In place with plates)

Fabric Pad Bearing Each 1,000.00 — 2,000.00(In place, including all plates, TFE, etc.)

Prestressed Concrete GirderW42G (Series 6) Lin. Ft. 85.00W50G (Series 8) Lin. Ft. 90.00W58G (Series 10) Lin. Ft. 100.00W74G (Series 14) Lin. Ft. 110.00W83G Lin. Ft. 130.00W95G Lin. Ft. 140.00

Structural Carbon Steel (Steelgirder, etc. when largeamount of steel is involved) Lbs. 0.80 — 1.35

Structural Low Alloy Steel (Steelgirder, etc. when large amountof steel is involved) Lbs. 1.00 — 1.40

Structural Steel (Sign supports, etc.when small amounts of steel are involved) Lbs. 2.00 — 4.00

Timber & LumberCreosote Treated MBM 1,500.00 — 2,000.00Salts Treated MBM 1,800.00 — 2,500.00Untreated MBM 1,000.00 — 1,500.00Lagging (in place) Untreated MBM 1,400.00 — 1,800.00Lagging (in place) Creosote Treated MBM 1,900.00 — 2,500.00

Expansion Joint Modification Lin. Ft. 250.00 — 350.00

Expansion Joint SystemCompression Seal Lin. Ft. 20.00 — 50.00Modular (Approx. $100 per inch of movement) Lin. Ft. 500.00 — 2,000.00Strip Seal Lin. Ft. 100.00 — 200.00

Bridge Drains Each 250.00 — 500.00

Bridge Grate Inlets Each 1,200.00 — 1,500.00

Conc. Class 5000 Cu. Yd. 500.00 — 600.00

Con. Class 5000 (Segmental Constr.) Cu. Yd. 600.00 — 700.00

Con. Class 4000D (Deck Only) Cu. Yd. 450.00 550.00

Conc. Class 4000 Cu. Yd. 400.00 — 500.00

12.3-A3-2 July 2000


Construction Costs Superstructure Estimating Aids

SUPERSTRUCTURE

(Continued)


Concrete Class EA(Exposed Aggregate) Cu. Yd. 350.00 — 500.00

Concrete Class 4000 LS(Low Shrinkage) Cu. Yd. $300.00 — $400.00

Concrete Class 5000 LS Cu. Yd. 400.00 — 500.00

St. Reinf. Bar Lb. 0.40 — 0.55

Epoxy-Coated Steel Reinforcing Bar Lb. 0.50 — 0.75

Post-tensioningPrestressing Steel (Includes Anchorages) Lbs. 1.50 — 2.50

Traffic Barrier Lin. Ft. 55.00 — 75.00

Metal Railing (Type BP & BP-B) Lin. Ft. 35.00 — 55.00

Metal Railing (Thrie Beam) Lin. Ft. 40.00 — 65.00

Modified Conc. Overlay C.F. 25.00 — 60.00

Furnishing and Curing Modified Conc. Overlay Sq. Yd. 40.00 — 70.00

Scarifying Conc. Overlay Sq. Yd. 8.00 — 12.00

Polymer Concrete Sq. Yd. 45.00 — 100.00

P65:DP/BDM12

July 2000 12.3-A4


Construction Costs Miscellaneous Estimating Aids

Miscellaneous


Electrical Conduit, metal 2≤ Lin. Ft. $ 8.00 — $ 15.00

Sign Support (Brackets, Mono,or Truss Sign Bridges) Lbs. 2.00 — 4.00

Concrete Surface FinishesFractured Fin Finish Sq. Yd. 17.00 — 28.00Exposed Aggregate Finish* Sq. Yd. 17.00 — 22.00Pigmented Sealer Sq. Yd. 5.00 — 8.00

ˇ *Requires the use ofconcrete Class EA

Painting Existing Steel Bridges(Lead Base) Ton. (Steel) 500.00 — 700.00

Painting New Steel Bridges Lb. (Steel) .08 — .10

Mobilization Sum of Items 10%

Masonry Drilling ∆Holes up to 1 foot deep1″ diameter 24.0011

2 ″ 25.002″ 28.002 1

2 ″ 30.003″ 32.503 1

2 ″ 42.504″ 47.505″ 53.006″ 60.007″ 77.00

∆ For holes greater than 1-foot deep up to 20 feet deep, use 1.5 × above prices.If drilling through steel reinforcing, add $16.00 per lineal inch of steel drilled.

Removal of Rails and Curbs Lin. Ft. $ 80.00 — $130.00

Removal of Rails, Curbs, and Slab Sq. Ft. 25.00 — 50.00

Further Deck Preparation Cu. Ft. 100.00 — 150.00

Bridge Deck Repair Cu. Ft. 110.00 — 160.00

Removing ACP from bridge deck Sq. Yd. 6.00 — 10.00

P65:DP/BDM12

August 1998 13.0-i


Construction Specifications and Estimates Contents

Page

13.0 Construction Specifications and Estimates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

13.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

13.2 Definitions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1A. Standard Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1B. Amendments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1C. Special Provisions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1D. Addendum . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1E. AD Copy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

13.3 Reviewing a Project . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1A. Job File . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1B. Bridge Rating Form . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1C. PS&E Check List (Form 230-037) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2D. Summary of Quantities (Form 230-031) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2E. Plans . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2F. Not Included in Bridge Quantities (Form 230-038) (see example 13.0 B-3) . . . . . . . . . . . . . . 2G. Foundation Report . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

13.4 Preparing the Cost Estimates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2A. General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2B. Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

13.5 Preparing the Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3A. General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3B. Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

13.6 Preparing the Working Day Schedule . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3A. General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3B. Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

13.7 Reviewing Projects Prepared by Consultants . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4A. General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4B. Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

13.8 Submitting the PS&E Package . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4A. General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4B. Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

13.9 Office Copy Review . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5A. Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5B. Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

Appendix A — Design Aids and Forms13.6-A1 Construction Time Rates

Appendix B — Design Examples13.0-B1 Construction Working Day Schedule13.0-B2 Cost Estimate Summary13.0-B3 Project Cost vs. Time Chart

P:DP/BDM13

August 1998 13-1


Construction Specifications and Estimates

13.0 Construction Specifications and Estimates

13.1 General

Introduction

The Bridge Projects Unit prepares the specifications and estimates (S&E) for all structural projectsdesigned or reviewed by the Bridge and Structures Office. The preparation includes reviewing the jobfile, plans, PS&E check list, “Not Included in Bridge Quantities List,” foundation report, and prepar-ing the cost estimates, specifications, and working day schedules; and submitting the PS&E packageto the Region or Plans Branch.

For projects designed by a Bridge Design Unit, the Bridge Projects Unit normally has three weeks toprepare the S&E package and submit it to the Bridge and Structures Engineer and another week tosubmit it to the Region or Plans Branch.

For projects designed by a consultant, the Bridge Projects Unit normally has three weeks to reviewand comment on the 90 percent design package. After the consultant submits the 100 percent designpackage, the Bridge Projects Unit has three weeks to prepare the S&E package and submit it to theBridge and Structures Engineer and another week to submit it to the Region or Plans Branch.

13.2 Definitions

A. Standard Specifications

Standard Specifications for Road, Bridge, and Municipal Construction, provisions and requirementsfor the prescribed work.

B. Amendments

Approved revisions or supplements to specific sections of the standard specifications.

C. Special Provisions

Supplemental specifications and modifications to the standard specifications and the amendments tothe standard specifications that apply to an individual project.

D. Addendum

A written or graphic document issued to all bidders and identified as an addendum prior to bidopening, which modifies or supplements the bid documents and becomes a part of the contract.

E. AD Copy

The AD copy is the contract document advertised to prospective bidders.

F. The governing order is as follows: Special Provisions, Contract Plans, then Standard Specificationsfor Road, Bridge, and Municipal Construction.

13.3 Reviewing a Project

A. Job File

Check for the items of work that need to be included in the PS&E; items that need special provisionsor cost estimates; and items that require additional research and information. Check that the job filefly leaf information has been completed by the designer (Form 221-076).

13-2 August 1998



B. Bridge Rating Form

Bridge rating forms are prepared by the designer and submitted as part of the design package to theBridge Projects Unit which are then forwarded to the Bridge Preservation Unit.

C. PS&E Check List (Form 230-037)

Check for special materials, construction requirements, permits, etc., that may need SpecialProvisions such as:

• Permits: United States Coast Guard

• Agreements: utilities on bridge, etc.

• Materials: structural steel, etc.

• Construction Requirements: temporary access, stage construction, or construction over railroad

• Special Items: modified concrete overlay or architectural treatment

D. Summary of Quantities (Form 230-031)

Verify that the Summary of Quantities is labeled as “Supervisor’s Bridge Quantities.” That is, thesupervisor shall summarize the quantities and resolve all discrepencies between the designer andchecker.

E. Plans

Check the plans for materials, special items, stage construction, standard notes and consistentterminology, etc.

F. Not Included in Bridge Quantities (Form 230-038) (see example 13.0 B-3)

Check for items shown on the plans that will be included in region’s PS&E work such as itemsoutside the structure limits. These shall be listed on the Not Included in Bridge Quantities List. Forexample: temporary traffic barrier, gravel backfill for walls, etc.

G. Foundation Report

Check that recommended foundation types and elevations are shown on the plans. Obtain a copy ofthe final Foundation Report for the S&E file. Check for settlement period of embankment, specialexcavation, etc., that need special provisions and/or cost estimates. Check for the number of test holesand the locations listed on the layout sheet against the final Foundation Report.

13.4 Preparing the Cost Estimates

A. General

Preparing the Bridge Cost Estimate consists of listing the standard and nonstandard bid items. Thesoftware Excel is used to prepare the Cost Estimate. The Bridge Projects Unit uses a standard outputformat for Cost Estimates. This output includes the tabulation of all items, a breakdown for each lumpsum item, and square foot cost of the structure.

B. Procedure

Pricing for the bid items above can be based on the Construction Cost Estimating Aids listed inAppendix A of Chapter 12, bid tabulations from previous contracts, and the Unit Bid Average listingfrom the Plan Branch Office. The engineer needs to make adjustments for inflation, site location,quantities involved, total of the work involved, etc.

August 1998 13-3



Each standard item has a corresponding code number. Both the item and code number are stored onthe Excel worksheet. The nonstandard unit contract items do not have standard item numbers forcoding.

All estimates shall include mobilization, but do not include sales tax, engineering, or contingencies.

13.5 Preparing the Specifications

A. General

There are three types of specifications: (1) Standard Specifications and Amendments to the StandardSpecifications, (2) General Special Provisions (GSP), and (3) Bridge Special Provisions (BSP).

All of the Amendments, GSP’s, and BSP’s texts are stored in the computer system and can beretrieved from the Plans Branch Text Processing. The texts are divided into topic documents.Each document is named under a coded name list under the Amendments, GSP, or BSP indexes.

If any modifications are made to a GSP, then the date must be dropped and the document code mustbe changed.

B. Procedure

In preparation of the bridge specifications, all of the applicable documents of the Amendments,GSPs, and BSPs are each listed in numerical order, and required fill-ins are provided, then these aresubmitted to text processing. The Plans Branch Text Processing will process the requested list usingstandard Form 220-013A (Appendix 13.5-A1.)

For special provisions not covered by a GSP or BSP, appropriate documents must be written inthe standard format including description, materials, construction requirements, measurement, andpayment. These documents are coded and placed on the appropriate order of the listing and are sentto the Plans Branch Text Processing for text processing.

The completed text of the bridge specifications shall be checked for typing errors, contents of thetexts, consistent terminology for materials called for in the plans, and pay items called for in theestimates. They shall be revised and reviewed as necessary before the final office copy is printed forthe S&E package.

13.6 Preparing the Working Day Schedule

A. General

The Bridge Projects Unit calculates the number of the working days necessary to construct thebridge portion of the contract, and enters the time in the special provision “Time for Completion.”The working days are defined in the Section 1-08.5 of the Standard Specifications.

B. Procedure

The first task of estimating the number of working days is to list all the construction activitiesinvolved in the project. These include all actual construction activities such as excavation, forming,concrete placement, and curing; and the nonconstruction activities such as mobilization, material andshop plan approval. Special conditions such as staging, limited access near wetlands, limited con-struction windows for work in rivers and streams, limited working hours due to traffic and noiserestrictions, require additional time.

13-4 August 1998



The second task is to assign the number of working days to each construction activity above (seeAppendix 13.6-A1). “Construction Time Rate” can be used as a guide to estimate construction timerequired. This table shows the average rate of output for a single shift, work day only. Adjustment tothe rates of this table should be made based on the project size, type of work involved, location of theproject, etc. In general, larger project will have higher production rates than smaller projects, newconstruction will have higher production rates than widening, and unstaged work will have higherproduction rates than staged work.

The last step is to arrange construction activities, with corresponding working days, into aconstruction schedule on a bar chart, either by hand on the Construction Working Day Schedule Form230-041 (see Appendix 13.0 B7) or by computer on the Microsoft Project Program. List the activitiesin a logical construction sequence, starting from the substructure to the superstructure. Items shalloverlap where practical and the critical path shall be identified.

13.7 Reviewing Projects Prepared by Consultants

A. General

Consultants are required to submit the 90 percent complete design package to the Bridge andStructures Office for review and comment three weeks prior to submiting the 100 percent completedesign package.

The package shall be in the same format as those prepared by the Bridge and Structures Office.

B. Procedure

The Bridge Projects Unit reviews and comments on the 90 percent complete design package. Afterthe consultant makes corrections and resubmits the package as 100 percent complete, the BridgeProjects Unit prepares and forwards the PS&E package to the Plans Branch.

13.8 Submitting the PS&E Package

A. General

The PS&E package includes:

1. Cover letter to the Bridge and Structures Engineer

2. Cover letter to the Region or Plans Branch.

For Region Ad and Award projects, the paragraph regarding “As Constructed Plans” and thecc: to “Construction Support Unit Technician” are only used when work related to a bridgeis part of the project, not for retaining walls, signs, etc. away from a bridge.

3. Bridge Construction Cost Estimate

4. Not Included in Bridge Quantity List

5. Special Provisions

6. Log of Test Borings

7. One Reduced Xerox Set of Plans

8. Cost Estimate Summary (see Appendix 13.0-B2)

9. Construction Working Day Schedule

August 1998 13-5



B. Procedure

Check with a resident specification and estimate engineer for the latest and most current acceptabledistribution list for the region in question.

13.9 Office Copy Review

A. Description

The Office Copy Review is a set of plans and special provisions to be reviewed before the AD Copyis printed. Normally, the Office Copy is received for reviewing two weeks prior to the AD date.

B. Procedure

The review of the Office Copy is to make sure the Bridge PS&E and Log of Test Boring have beenproperly incorporated before the printing of the AD Copy; and to check the coordination between theregion’s plans and Bridge Office’s plans.

Revisions, changes, additions, deletions shall be submitted to the regions or the Plans Branch by theSpecifications and Estimate Engineer.

P:DP/BDM13

August 1998 13.6-A1


Construction Specifications and Estimates Construction Time Rates

Construction Time Rates

Minimum Maximum AverageOperation Units** Output Output Output

SubstructureStructure Exc. & Shoring C.Y./Day 20 150 80

*Seals C.Y./Day 10 20 15*Footings C.Y./Day 6 14 10*Abutment Walls C.Y./Day 4 19 7*Wingwalls C.Y./Day 1 2 1.5*Retaining Walls with Footings C.Y./Day 4 17 11*Columns C.Y./Day 3 8 4Falsework for X-beams C.Y./Day 13 4 10

*X-beams C.Y./Day 16 20 18Driving Test Piles Each/Day 1 2 1Furnishing PilesPrecast Concrete Days 40 20 30Cast-in-Place Concrete Days 15 2 5Steel Days 30 2 10Timber Days 20 2 5Driving PilesConcrete L.F./Day 100 200 150Steel L.F./Day 100 200 150Timber L.F./Day 100 200 150Prestressed GirdersGirder Fabrication Days 70 35 45Set Girders L.F./Day 200 1,450 550

*Slab & Diaphragms C.Y./Day 6 18 11Box GirdersSpan Falsework S.F./Day 150 900 700

*Bottom Slab C.Y./Day 3 11 8*Webs, Diaphragms, and X-beams C.Y./Day 5 25 18*Top Slab C.Y./Day 7 12 9Stress and Grout Strands LBS/Day 4,500 8,000 6,000Strip Falsework S.F./Day 1,500 3,000 2,200T-BeamSpan Falsework S.F./Day 500 1,000 700

*Girders, Diaphragms, and Slab C.Y./Day 6 15 10Strip Falsework S.F./Day 1,000 2,000 1,500Flat SlabSpan Falsework S.F./Day 100 600 250

*Slab and X-beams C.Y./Day 6 15 10Strip Falsework S.F./Day 300 1,000 500Steel GirderGirder Fabrication Days 200 110 150Girder Erection L.F./Day 50 200 100

*Slab C.Y./Day 6 15 10Painting S.F./Day 1,000 3,000 2,000Miscellaneous

*Traffic Barrier L.F./Day 20 80 40*Traffic Railing & Sidewalk L.F./Day 15 60 35*Concrete Overlay S.Y./Day 200 300 250Expansion Joint Replacement Days/Lane 4 6 8

Closure * Concrete** All times are based on 8-hour work days

13-6A:P:BDM13

August 1998 13.0-B2


Construction Specifications and Estimates Cost Estimate Summary

P:DP/BDM13

August 1998 13.0-B3


Construction Specifications Project Cost vs. Time Chart

P:DP/BDM13


Bridge Rating Contents

Page

14.0 Bridge Rating . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14.1-1

14.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

14.1.1 Rating Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

14.1.1.1 Load Resistance Factor Rating (LRFR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

14.1.1.2 Load Factor Design Rating (LFDR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

14.1.2 Live Loads . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3


14.1.2.2 Load Factor Design Rating (LFDR) for National Bridge Inventory (NBI) . . . . . . . . . . . . . . . . . 3

14.1.3 Dead Loads . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

14.1.4 Load Factors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4


14.1.4.2 Load Factor Design Rating (LFDR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

14.1.5 Load Capacity Reduction Factors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

14.1.6 Impact . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7


14.1.6.2 Load Factor Rating (LFDR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

14.1.7 Reduction Factors (for both LRFR and LFDR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

14.1.8 Ratings for Overloads (LRFR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

14.2 Special Rating Criteria . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14.2-1

14.2.1 Prestressed Concrete Bridges . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1


14.2.1.2 Load Factor Design (LFD) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

14.2.2 Reinforced Concrete Structures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

14.2.2.1 Concrete Decks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

14.2.2.2 Concrete Crossbeams . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

14.2.2.3 In-Span Hinges . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

14.2.3 Concrete Box Girder Structures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

14.2.4 Concrete T-Beam Structures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

14.2.5 Concrete Flat Slab Structures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

14.2.6 Steel Structures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

14.2.6.1 Steel Floor Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

14.2.6.2 Steel Truss Structures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

14.2.7 Timber Structures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

14.2.8 Widened or Rehabilitated Structures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

14.2.9 Other Special Cases . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

14.3 Load Rating Software . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14.3-1

14.4 Load Rating Reports . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14.4-1

14.99 Bibliography . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

August 1998 14.0-i


Bridge Rating Contents

Appendix A — Design Aids14.0-A1 Load Rating Flow Chart14.0-A2 Source of Rating Factors14.0-A3 Bridge Inspection Report Condition Codes14.0-A4 Span Type Abbreviations14.0-A5 Bridge Rating Summary14.0-A6 Load Rating Flow Chart14.0-A7 3D Live Load Modeling Guidelines for Truss Bridges

P:DP/BDM149807-0802

14.0-ii August 1998


Bridge Rating General

14.0 Bridge Rating

14.1 General

Bridge Rating is a procedure to evaluate the adequacy of various structural components to carrypredetermined applied loads. The WSDOT Bridge Preservation Section is responsible for the bridgeinventory and load rating of existing and new bridges in accordance with the NBIS and the AASHTOManual for Condition Evaluation of Bridges, latest edition. As presently required, only elements of thesuperstructure will be rated. Generally, superstructure shall be defined as all structural elements abovethe column tops including drop cross-beams.

Load rating shall be part of structural design for all, widened (one lane width or more throughout thelength of the bridge), or rehabilitated bridges where the rehabilitation alters the load carrying capacityof the structure. The carrying capacity of a widened or rehabilitated structure shall equal or exceed thecapacity of the existing structure. The Bridge Design Section generally will not be required to load ratenew bridges/designs. However, for the more complex structures where computer models are used in thedesign/analysis, a copy of the computer models shall be made and submitted to the Bridge Load RatingEngineer in the Bridge Preservation Section.

In order to provide a baseline rating for new bridges, the bridge designer shall make rating calculationsand complete a Bridge Rating Summary (see Appendix 14.0-A5) as part of the design process. Thedesigner shall place the original rating calculations and report and a copy of the bridge plans in anAccopress-type binder (see Section 14.4). When the bridge design is complete, the designer shallforward the completed bridge rating package to the Bridge Projects Unit, then the Bridge ProjectsUnit will forward the rating package to the Bridge Preservation Section. The bridge rating will gointo service at the completion of bridge construction. The Bridge Preservation Section shall thenbe responsible to maintain an updated bridge load rating throughout the life of the bridge based oncurrent bridge condition (see Appendix 14.0-A1).

Conditions of existing bridges change resulting in the need for reevaluation of their load rating. Suchchanges may be caused by damage to structural elements, extensive maintenance or rehabilitativework, or any other deterioration identified by the Bridge Preservation Section through their regularinspection program.

This criteria applies only to concrete and steel bridges. For timber bridges, rating procedure shall beas per Chapters 6 and 7 of the 1994 AASHTO Manual for Condition Evaluation of Bridges.

14.1.1 Rating Procedure

Structural elements as defined above shall be evaluated for flexural, vertical shear, and torsionalcapacities based on Load Resistance Factor Design (LRFD) as outlined in the AASHTO 1989 GuideSpecifications for Strength Evaluation of Existing Steel and Concrete Bridges and Load Factor Design(LFD) as outlined in the 1994 AASHTO Manual for Condition Evaluation of Bridges. Consider allreinforcing, including temperature/distribution reinforcing, in the rating analysis.

By definition, the adequacy or inadequacy of a structural element to carry a specified truck load will beindicated by the value of its rating factor (RF); that is, whether it is greater or smaller than 1.0. For aspecific loading, the lowest RF value of the structural elements will be the overall rating of the bridge.

August 1998 14.1-1



14.1.1.1 Load Resistance Factor Rating (LRFR)

For HS-20, AASHTO-1, AASHTO-2, and AASHO-3 trucks, the basic rating equation shall be:

R.F. = (for flexure)φM M M

MCAP D DL P P

L L I

− ±

+( )γ γ

γ

R.F. = (for vertical shear)φV V V

VCAP D DL P P

L L I

− ±

+( )γ γ

γ

For Overload (OL)-1 and Overload-2 trucks, the basic rating equation shall be:

R.F. = (for flexure)

φM M M M

M

CAP D D P P L L I

L L I

− ± − ( )( )

+( )

+( )

γ γ γ

γ

AASHTO - Truck

OL - Truck

R.F. = (for vertical shear)

φV V V V

V

CAP D D P P L L I

L L I

− ± − ( )( )

+( )

+( )

γ γ γ

γ

AASHTO - Truck

OL - Truck

Where:

R.F. = Rating Factor (Ratio of Capacity to Demand)

MCAP = Ultimate Bending Moment Capacity

* MDL = Calculated Dead Load Bending Moment

MP = Secondary Bending Moment Due to Prestressing

* M(L+I) = Calculated Live Load and Impact Bending Moment

f = Resistance Factor (Capacity Reduction Factor)

γD = Dead Load Factor

γL = Live Load Factor

γP = Prestress Factor

I = Impact

VCAP = Ultimate Shear Capacity

VDL = Calculated Dead Load Shear Force

VP = Calculated Prestressing Shear Force

V(L+I) = Calculated Live Load Plus Impact Shear Force

*For continuous structures, a one-half support width moment increase is to be used.

14.1-2 August 1998



14.1.1.2 Load Factor Design Rating (LFDR)

For HS-20 Inventory and HS-20 Operating Ratings, the basic equation shall be:

R.F. = φR A D S

A L In

− ±+( )

1

2 1

Where:


φRn = Nominal Capacity of the Member

D = Unfactored Dead Load Moment or Shear

L = Unfactored Live Load Moment or Shear

S = Unfactored Prestress Secondary Moment or Shear

I = Impact Factor to Be Used With the Live Load Effect

A1 = Factor for Dead Load (see Section 14.1.4.2)

A2 = Factor for Live Load (see section 14.1.4.2)

Additional rating consideration shall be given to prestressed and post-tensioned members and isdiscussed in further detail in Section 14.2.1.2.

14.1.2 Live Loads

The vehicles specified in the AASHTO Guide Specifications for Strength Evaluation of Existing Steeland Concrete Bridges represent legal weights and are to be used to determine posting limits. The twooverload vehicles represent extremes in the limits of permitted vehicles in Washington State. TheHS-20 vehicle and lane load as specified in the AASHTO Manual for Condition Evaluation of Bridgesare to be used in reporting the inventory and operating ratings to the National Bridge Inventory.

For new designs, the number of lanes shall be the actual designated lanes as shown on the bridge layout(not the number of lanes as per AASHTO Specification 3.6). For existing bridges, the number of lanesshall be the actual striped lanes at the time of rating.

When multiple lanes are considered, apply the appropriate multilane reduction factor given in Section14.1.7. Load distribution methods are discussed under specific bridge types. Do not consider sidewalklive loads in rating analysis.


The six moving loads for the initial rating shall be the HS-20 truck loading (Figure 14.1.2-4), threeAASHTO vehicles and two overload trucks (Figure 14.1.2-1). In addition, use the lane loading asshown on Figure 14.1.2-2 to rate structures with spans over 200 feet. For the two overload trucks(OL-1 and OL-2), use only one overload truck occupying one lane in combination with one of theAASHTO trucks in each of the remaining lanes.

14.1.2.2 Load Factor Design Rating (LFDR) for National Bridge Inventory (NBI)

The live load to be used in the basic rating equation should be the HS-20 truck (Figure 14.1.2-4) orlane loading (Figure 14.1.2-3) as defined in the AASHTO Design Specifications. Where the effectsare greater than those produced by HS-20 truck, the bridge should also be rated using the lane loading.

August 1998 14.1-3



14.1.3 Dead Loads

Dead Loads shall be as defined in the AASHTO Standard Specifications for Highway Bridges, exceptfor concrete weight shall be 155 pcf. Dead Load shall include weight of any existing bridge deckoverlay. When overlay depth is not known, allowance shall be as per Section 3.3.2.1 of the AASHTOGuide Specifications.

14.1.4 Load Factors


Dead Load γD = 1.20

Prestress Load γP = 1.00

Live Load*

1. Low volume roadways (ADTT less than 1,000), significant sourcesof over weight trucks without effective enforcement. γL = 1.65

2. Heavy volume roadways (ADTT greater than 1,000), significant sourcesof over weight trucks without effective enforcement. γL = 1.80

3. OL-1 and OL-2 (or other permit vehicles). γL = 1.30

14.1-4 August 1998



*Notes:

If unavailable from traffic data, ADTT may be estimated as 20 percent of ADT.

The listed factors are essentially the same as Table 2 of AASHTO Guide Specifications except thatLive Load Category 1 and 2 have been eliminated based on the assumption that Washington State doesnot have fully effective enforcement or control of overloads.

Trucks for Rating (for LRFR)

Figure 14.1.2-1

August 1998 14.1-5



Lane Load Rating (for LRFR)

Figure 14.1.2-2

Lane Load Rating (for LFDR)

Figure 14.1.2-3

HS-20 Truck (for both LRFR and LFDR)

Figure 14.1.2-4

14.1-6 August 1998



14.1.4.2 Load Factor Design Rating (LFDR)

Dead Load A1 = 1.30

Live Load Operating A2 = 1.30

Inventory A2 = 2.17

14.1.5 Load Capacity Reduction Factors

Use the evaluating procedures and equations found in the AASHTO Standard Specifications forHighway Bridges under the section on load factor design to determine nominal resistance. Thefollowing resistance factors (capacity reduction) apply only to structural members in good condition.Generally, condition of the structure and other pertinent information are listed on the Bridge InspectionReport and rating information sheets. The engineer should use this data to make adjustments to theresistance factors. For deck rating, the condition code found in field 8 (visual) of the old BridgeInspection Report or 507 of the new Bridge Management Inspection Report should be used to adjustresistance factors. For superstructure rating, the lowest code of fields 14-19 of the old InspectionReport or fields 38 through 156 of the new Bridge Management Inspection Report should be used.Normally, adjustments can be made based on the AASHTO Guide Specifications Tables 3(a) and3(b). Questions regarding interpretation of these tables should be directed to the Bridge LoadRating Engineer.

For new designs, all ratable elements shall be considered an “8” for new condition.

Resistance Factors:

Redundant Steel Members: φ0.95Nonredundant Steel Members:φ0.80Prestressed Concrete Elements:φ0.95 flexure

φ0.90 shearReinforced Concrete Elements:φ0.90 flexure

φ0.85 shear

14.1.6 Impact


For new designs, impact shall be 10 percent (0.1).

For existing bridges, the impact shall be determined by the approach roadway condition (field 33) andthe amount of severe scaling on the bridge (field 12) as shown on the old Bridge Inspection Reportor (field 533) and (field 512) respectively on the current Bridge Management Inspection Report. Forapproach roadway condition codes 6 or greater, assume 10 percent impact; for codes 5 or less, assume20 percent impact. If the bridge has 0 to 4 percent severe scaling (S00 to S04 for the first three entriesin field 12 or 512), assume 10 impact; if between 5 and 15 percent severe scaling, assume 20 percentimpact; if greater than 15 percent severe scaling, assume 30 percent impact.

February 2000 14.1-7



14.1.6.2 Load Factor Rating (LFDR)

Impact is expressed as a fraction of the live load stress, and shall be determined by the followingformula:

*I = 50

125L +

Where:

I = Impact Fraction (maximum 30%)

L = Length in Feet of the Portion of the Span That is Loaded to Produce the Maximum Stress inthe Member.

*AASHTO Standard Specifications for Highway Bridges 3.8.2.1.

14.1.7 Reduction Factors (for both LRFR and LFDR)

Number of Loaded Lanes Reduction Factor

One or two lanes 1.0Three lanes 0.8Four lanes or more 0.7

14.1.8 Ratings for Overloads (LRFR)

The OL-1 and OL-2 truck loads listed in Section 14.1.2 are considered to be overloads.

Due to the infrequent nature of the overloads, it is more reasonable to use reduced live load factors forrating rather than those specified for design. For special cases, such as checking prestressed concretemembers by the service load method, the rating factors should be established by using higher allowablestresses (see Section 14.2, Special Rating Criteria).

For overload ratings, the load factors to be used in the basic rating equation shall be:

γD = 1.2

γL = 1.3

γP = 1.0

P:DP/BDM149807-0802

14.1-8 August 1998



14.2 Special Rating Criteria

14.2.1 Prestressed Concrete Bridges


For prestressed concrete members, rating is to be determined by the service load method for bendingmoments.*

For prestressed girders designed for continuous of live load and impact, rate the negative moment zoneat interior supports as a conventional reinforced concrete member, considering only the deck reinforce-ment (by load factor method). For loading conditions that produce positive moment at the supports, theprestressed girders extended strands can be considered as positive reinforcement.

Rating for shear in the girder shall begin at a distance h/2 from the centerline of the pier (h = overallgirder depth).

When rating for AASHTO vehicles, allowable stresses shall be:

Tensile stress for top and bottom = 6(f′c)1/2

Compressive stress = 0.4 f′c

When rating for overload trucks (OL-1 and OL-2), allowable stresses shall be:

Tensile stress for top and bottom = 1.15 [6(f′c)1/2]

Compressive stress = 0.53 (1.3 f′c)

For all loadings, prestress losses shall be as per design or current AASHTO Design Specifications.

*When the rating for the overload vehicles is less than 1.0, a check by the ultimate load method shallalso be made. The rating recorded on the summary sheet shall be the value determined by the ultimateload method divided by 1.30 but no greater than 1.0.

14.2.1.2 Load Factor Design (LFD)

The rating of prestressed concrete members at both Inventory and Operating level should beestablished in accordance with the strength requirements of Article 9.17 of the AASHTO DesignSpecifications. Additionally at Inventory level, the rating must consider the allowable stresses atservice load as specified in Article 9.15.2.2 of the AASHTO Design Specifications. In situations ofunusual design with wide dispersion of the tendons, the operating rating might further be controlledby stresses not to exceed 0.90 of the yield point stresses in the prestressing steel nearest the extremetendon fiber of the member.

Typically, prestressed concrete members used in bridge structures will meet the minimumreinforcement requirements of Article 9.18.2.1 of the AASHTO Design Specifications. While thereis no reduction in the flexural strength of the member and, in the event that these provisions are notsatisfied, the Bridge and Structures office, may choose, as part of the flexural rating, to limit live loadsto preserve the relationship between φM

n and 1.2M

cr that is prescribed for a new design. The use of this

option necessitates an adjustment to the value of the nominal moment capacity φMn, used in the

flexural strength rating equations. Thus when φMn < 1.2M

cr, the nominal moment capacity becomes

(k)φ(Mn),

k = φM

Mn

cr1 2.

August 1998 14.2-1



Inventory Rating

To establish the Inventory rating for Prestressed Concrete, use the lowest rating factor from the basicrating equation, shown in Section 14.1.1.2, and the following equations:

R.F. = (Concrete Tension)6 1 2

1

f F F F

Fc d p s′( ) − + ±

R.F. = (Concrete Compression)0 6

1

. f F F F

Fc d p s′ − − ±

R.F. = (Concrete Compression)0 4 1

2

1

. f F F F

F

c d p s′ − − ±( )

R.F. = (Prestressing Steel Tension)0 8

1

. f y F F F

F

d p s∗ − + ±( )

Operating Rating

To establish the operating rating for Prestressed Concrete, use the lowest rating factor, from the basicrating equation, shown in Section 14.1.1.2, and the following equation should be used:

R.F. = (Prestressing Steel Tension)0 9

1

. f y F F F

F

d p s∗ − + ±( )

Where:


f′c = Concrete Compressive Strength

Fd = Unfactored Dead Load Stress

Fp = Unfactored Stress Due to Prestress Forces After All Losses

Fs = Unfactored Stress Due to Secondary Prestress Forces

Fl = Unfactored Live Load Stress Including Impact

f*y = Prestress Steel Yield Stress (per AASHTO 9.1.2)

14.2.2 Reinforced Concrete Structures

For conventional reinforced concrete members of existing bridges, checking of serviceability shall notbe part of the rating evaluation.

Rating for shear in the longitudinal direction shall begin at a distance h/2 from the centerline of the pier(h = total depth).

14.2.2.1 Concrete Decks

For all concrete roadway deck slabs, except flat slab bridges, that are designed per current AASHTOcriteria for HS-20 loading or heavier, loading will be considered structurally sufficient and need notbe rated. However, for existing roadway slabs having any of the following conditions, rating willbe required:

1. Slab was designed for live loads lighter than HS-20.

2. Slab overhang is more than half the girder spacing.

3. Bridge Inspection Report Code is below 4 (field 8 or 508 — visual deck condition).

14.2-2 August 1998



4. When the original traffic barrier(s) or rail have been replaced by heavier barrier.

When rating of the slab is required, live load shall include all vehicular loads as specified inSection 14.1.2 and load distribution shall be per current AASHTO Standard Specifications forHighway Bridges.

14.2.2.2 Concrete Crossbeams

For concrete crossbeams integral with the superstructure (raised crossbeam) on new bridges, ratingwill be for the number of designated lanes (see 14.1.2). For existing structures, ratings will be forthe number of striped lanes. Live loads conforming to these lane configurations can be applied to thecrossbeam as moving point loads at any location between curbs which produce the maximum effect.

When rating for shear in crossbeams, current AASHTO Design Specifications requires shear design tobe at the face of support if there is a concentrated load within a distance “d” from the face of support.This requirement is new relative to earlier editions of AASHTO Design Specifications which allowedshear reinforcement design to be at a distance “d” from the face of support. When rating existingcrossbeams which show no indication of distress on the latest inspection report, but have a ratingfactor of less than one (1.0), a more detailed/accurate shear analysis should be performed. One accept-able method is the “truss analogy” as published in Bibliography 14.99-1(1). For existing box girderand integral T-beam crossbeams, in lieu of this detailed analysis, dead and live loads can be assumedas uniformly distributed and the shear rating performed at a distance “d” from the face of support.

14.2.2.3 In-Span Hinges

For in-span hinges, rating for shear and bending moment should be performed based on the reducedcross-sections at the hinge seat. Diagonal hairpin bars are part of this rating as they provide primaryreinforcement through the shear plane.

14.2.3 Concrete Box Girder Structures

Rating shall be on the per bridge basis for all applied loads. This is consistent with the current designprocedures regarding live load applications.

14.2.4 Concrete T-Beam Structures

Rate on a per member basis, except for precast girder units, which are to be rated per unit.

14.2.5 Concrete Flat Slab Structures

Rate cast-in-place solid slabs on a per foot of width basis. Rate precast panels on a per panel basis.Rate cast-in-place voided slabs based on a width of slab equal to the predominant center-to-centerspacing of voids.

Load distribution shall be per current AASHTO Standard Specifications for Highway Bridges.

When rating flat slabs on concrete piling, assume pin-supports at the slab/pile interface of interior piersand the slab continuous over the supports. If ratings using this assumption are less than 1.0, the pilesshould be modeled as columns with fixity assumed at 10 feet below the ground surface.

Pile caps are to be rated if deemed critical by the engineer.

14.2.6 Steel Structures

On existing bridges, checking of fatigue and servicability shall not be part of the rating evaluation.

August 1998 14.2-3



14.2.6.1 Steel Floor Systems

Floorbeams and stringers shall be rated as if they are simply supported. Assume the distance fromoutside face to outside face of end connections as the lengths for the analysis. For steel floorbeamson new bridges, rate for the number of designated lanes (see 14.1.2). For existing structures, rate forthe number of striped lanes. Live loads conforming to these lane configurations can be applied to thefloorbeam as moving point loads at any location between curbs which produce the maximum effect.

The end connections for stringers and floorbeams shall be rated.

Do not rate connections unless there is evidence of deterioration.

14.2.6.2 Steel Truss Structures

The capacity of steel truss spans, regardless of length, shall follow the AASHTO Guide Specificationsfor Strength Design of Truss Bridges (load factor design) and the AASHTO Standard DesignSpecifications. In the event the two specifications are contradictory, the guide specification is tobe followed.

Rate on a per truss basis using either 3-D analysis or simplified distribution methods. Assumenonredundancy of truss members and pinned connections.

In general, rate chords, diagonals, verticals, end posts, stringers, and floorbeams. Do not rateconnections unless there is evidence of deterioration, except for pinned connections with trusses.For pin-connected trusses, also analyze pins for shear, and the side plates for bearing capacity.

For truss members that have been heat-straightened three or more times, deduct 0.1 from φ(Phi).

14.2.7 Timber Structures

Unless the species and grade is known, assume Douglas fir, select structural for members installedprior to 1955 and Douglas fir, No. 1 after 1955. The allowable stresses for beams and stringers, aslisted in the AASHTO Standard Design Specifications, should be used.

The inventory rating for HS-20 vehicle is calculated using allowable stresses as directed in theAASHTO Standard Design Specifications. For calculating the operating rating for the HS-20 vehicle,the 3 AASHTO, and two overload vehicles, use 133 percent of the inventory allowable stress.

The nominal dimensions should be used to calculate deadload, and the net dimensions to calculatesection modulus. If the member is charred, it may be assumed the 1/4-inch of material is lost on allsurfaces. Unless the member is notched or otherwise suspect, shear need not be calculated.

When calculating loads, no impact is assumed and distribution factors are selected assuming one trafficlane where the roadway is less than 20 feet wide or two or more traffic lanes where the roadway is20 feet or wider.

14.2.8 Widened or Rehabilitated Structures

For widened bridges, rate crossbeams in all cases.

Since the longitudinal capacity of the widened portion of the structure will equal or exceed the capacityof the existing structure, a longitudinal rating for the widened portion will be required only when thewidth of the widened portion on one side of the structure is greater than or equal to 12′-0″ or morethroughout the length of the structure.

For rehabilitated bridges, a load rating will be required if the load carrying capacity of the structure isaltered by the rehabilitation.

14.2-4 August 1998



14.2.9 Other Special Cases

For nonredundant structures such as through girder, arches, and/or any superstructure with less thanthree main load carrying members, rating shall be on the per member basis.

P:DP/BDM149807-0802

August 1998 14.2-5



14.2-6 August 1998



14.3 Load Rating Software

Use the current version of BRIDG for Windows software for all applicable ratings. The capabilities andrelease dates of the BRIDG software are as follows:

Release Version Release Date Rating Capabilities

BRIDG v.105. July 1996 LRFD and LF of concrete bridges.

BRIDG v.11.0. December 1995 LRFD and LF of steel girder bridges.

BRIDG v.97 September 1997 LRFD and LF of concrete, steelgirder, and steel truss bridges.

*Tenative release dates.

P:DP/BDM149807-0802

August 1998 14.3-1



14.4 Load Rating Reports

Rating reports shall consist of:

1. A Bridge Rating summary sheet as shown on Appendix 14.0-A5 reflecting the lowest rating factor,including superstructure components not analyzed by BRIDG, for each loading condition.

2. A brief report of any anomalies in the ratings and an explanation of the cause of any rating factorbelow 1.0.

3. Hard copy of computer output files (RPT files) used for rating, and any other calculations orspecial analysis required.

4. A complete set of plans for the bridge.

5. Two 3.5-inch data diskettes which contains the final versions of all input files (BDF files) createdin performing the load rating.

All reports shall be bound in Accopress-type binders.

When the load rating calculations are produced as part of a design project (new, widening, orrehabilitation,) the load rating report and design calculations shall be bound separately.

Any questions on the BRIDG Program or load rating can be directed to the bridge Load RatingEngineer.

14.99 Bibliography

1. Manual for Condition Evaluation of Bridges (1994) AASHTO, 444 North Capitol Street NW,Suite 249, Washington, D.C. 20001.

P:DP/BDM149807-0802

August 1998 14.4-1

Bridge Designer complete LoadRating as part of Design Project

Load Rating turned into BridgeProject Unit

Load Rating sent to LoadRating Engineer

Load Rating Engineertracks Load Ratings

Load Rating Engineer UpdateDatabase and File Load Rating

Complete

S&E schedule distributed monthlyto Load Rating Engineer

List of missing Load RatingsDistributed quarterly to the Bridge

Design Engineer

No

yes

14.0-A1 Load Rating Flow Chart


Bridge Rating Load Rating Flow Chart

August 1998 14.0-A1

14.0-A2 Source of Rating Factors


Bridge Rating Source of Rating Factors

14.0-A2 August 1998

Bridge Inspection Report Condition Codes

9 Not applicable.

8 Very good condition. No defects. Bridge can carry normal traffic levels. No action required to monitoror repair.

7 Good condition. Minor defects with potential for minor repair. Bridge can carry normal traffic levels.Record and monitor bridge conditions.

6 Satisfactory condition. Moderate defects with potential for major repair. Bridge is adequate for normaltraffic levels. Record and monitor bridge conditions and/or add to repair schedule.

5 Fair condition. Moderate defects with potential for minor rehabilitation. Bridge is minimally adequate forhighway traffic. Monitor bridge conditions and/or add to repair schedule.

4 Poor Condition. Major defects requiring major repair. Bridge is marginally adequate for truck traffic.Make repairs as soon as possible.

3* Serious condition. Major defects. Member is failing. Bridge is inadequate for truck traffic. Repair bridgeimmediately or restrict truck traffic.

2* Critical condition. Major defects. Member has failed. Bridge is inadequate for all highway traffic.Repair bridge immediately or close bridge.

1* Imminent failure. Bridge is closed and inadequate for all highway traffic. Bridge cannot be rehabilitated.

0* Failed. Bridge is closed and inadequate for all highway traffic. Bridge is beyond repair.

*These codes are used to rate the condition of primary bridge members only (i.e., trusses, beams, abutments, etc.).

For changing values in the rating factor equation, a condition code of 7 or 8 corresponds to good or fair condition.A condition code of 5 or 6 corresponds to a deteriorated condition; generally the report would identify the deficientstructural elements with specifics such as section loss.

A condition code of 4 or less corresponds to a heavily deteriorated condition. The report should state the specificelement with its section loss.

Inspection is considered to be estimated except in a specific case associated with identifiable deteriorated and/ordeteriorating structures.

Maintenance is considered intermittent unless specifically directed in unusual circumstances.


Bridge Rating Bridge Inspection Report Condition Codes

August 1998 14.0-A3

Span Type Abbreviations

BAS Bascule Lift Span

CA Concrete Arch

CBOX Concrete Box Girder

CFP Concrete Floating Pontoon

CG Concrete Girder

CS Concrete Slab

CST Concrete Slab on Timber Piling

CTB Concrete T-Beam

CTRU Concrete Truss

CTUN Concrete Lined Tunnel

CCULV Concrete Culvert

ESB Encased Steel Beam

PCB Pretensioned Concrete Beam

PCS Pretensioned Concrete Slab

PCTB Pretensioned Concrete T-Beam

POB Post-tensioned Concrete Beam

POTB Post-tensioned Concrete T-Beam

PTBX Post-tensioned Box Girder

PRC Precast Reinforced Concrete Beam

PRPOB Pretensioned and Post-tensioned Beam

SA Steel Arch

SB Steel Beam

SBOX Steel Box Girder

SCULV Steel Culvert

SFP Steel Floating Pontoon

SG Steel Girder

SL Steel Lift Span

SS Steel Swing Span

ST Steel Truss

SUSP Steel Suspension Span

TCULV Timber Culvert

TTLB Treated Timber Laminated Beam

TTLL Treated Timber Longitudinal Laminated

TTRU Treated Timber Truss

TTS Salts-Treated Timber Trestle

TTT Creosote-Treated Timber Trestle

TTUN Timber-Lined Tunnel

TUN Tunnel

UTL Untreated Log

UTRU Untreated Timber Truss

UTT Untreated Timber Trestle

UTLB Untreated Timber Laminated Beam


Bridge Rating Span Type Abbreviations

14.0-A4 August 1998

Bridge Rating Summary

Bridge Name: _________________________________________________________________________________

Bridge Number: _______________________________________________________________________________

Span Types: __________________________________________________________________________________

Bridge Length: ________________________________________________________________________________

Design Load: _________________________________________________________________________________

Rating By: ___________________________________________________________________________________

Checked By: __________________________________________________________________________________

Date: ________________________________________________________________________________________

Truck RF γ Controlling Point

HS-20 _________________ _________________ _____________________________

AASHTO 1 _________________ _________________ _____________________________

AASHTO 2 _________________ _________________ _____________________________

AASHTO 3 _________________ _________________ _____________________________

OL-1 _________________ _________________ _____________________________

OL-2 _________________ _________________ _____________________________

NBIS Rating

Inventory _________________ _________________ _____________________________

Operations _________________ _________________ _____________________________

Remarks:_____________________________________________________________________________________

____________________________________________________________________________________________

____________________________________________________________________________________________

____________________________________________________________________________________________

____________________________________________________________________________________________

____________________________________________________________________________________________

____________________________________________________________________________________________

____________________________________________________________________________________________


Bridge Rating Bridge Rating Summary

August 1998 14.0-A5

3D Live Load Modeling Guidelines for Truss Bridges

Live Load Criteria

The live loads to be considered and the application thereof, shall be consistent with those described in theAASHTO Guide Specifications for Strength Evaluation of Existing Steel and concrete Bridges and the WSDOTBridge Design Manual. To summarize the criteria:

• In computing load effects, one vehicle shall be considered present in each rating lane.

• The positioning of the vehicle in each rating lane shall be according to AASHTO specifications. Thesespecifications require the vehicle to be positioned in such a way as to produce the extreme structural responseunder consideration.

• For the purpose of load rating, the number of rating lanes shall be considered the number of striped lanes.

• The rating lanes shall be positioned between the curbs in accordance with the AASHTO specifications.

Live Load Modeling Guidelines

The purpose of these guidelines is to provide the rating engineer with a live load modeling scheme that will capturethe significant load effects for typical, well conditioned truss bridges, while reducing the time required to performa detailed live load analysis. Typical truss bridges are symmetrical about their longitudinal axes, with paralleltrusses, straight members, and uniform spacing of floor beams. It is ultimately the responsibility of the ratingengineer to determine the minimum rating factor for the structure. For unique and/or poorly conditioned structures,this may require a more detailed evaluation of the live load effects.

BRIDG™ for Windows® implements a brute force live load analysis method. To improve live load analysisperformance, the generation of live load cases must be reduced. These guidelines describe live load generation interms of longitudinal step sizes for the movement of the trucks along the bridge and transverse lane positionsbetween the curb lines.

Minimum Longitudinal Step Size

Longitudinal step shall not be less than the distance between floor beams.

Transverse Placement of Rating Lanes

The transverse placement of rating lanes is guided by the Lane Shift Sensitivity Factor (LSSF). This factor is usedto determine if the response of the structure is sensitive to lane positioning. The Lane Shift Sensitivity Factor iscomputed by:

LSSF = (# of Design Lens - # of Rating Lanes) / # of Rating Lanes

Where:

Number of rating Lanes is the equal to the number of lanes currently striped on the bridge.

Number of Design Lanes is as specified by the AASHTO Standard Specification for Bridges.


Bridge Rating Load Rating Flow Chart

14.0-A6 August 1998

The position of rating lanes is described in the following table:

Sensitivity LSSF Lane Group Positioning

Insensitive LSSF < 0.25 Center of the bridge

Sensitive 0.25 ≤ LSSF ≤ 1.0 Left Edge, Center, Right Edge

Hypersensitive LSSF > 1.0 Left Edge, Left Quarter Point, Center, Right QuarterPoint, Right Edge

This method of transverse placement will be used to determine the Inventory and Operating Ratings for reportingto the National Bridge Inventory. This method will also be used to determine if the bridge needs further investiga-tion by the WSDOT Bridge Preservation office. This investigation will determine the need for posting, restrictionto permit (a.k.a. overload) vehicles, and need for retrofit or rehabilitation.

P:DP/DM149807-0802


3D Live Load ModelingBridge Rating Guidelines for Truss Bridges

August 1998 14.0-A7

civil engineering bridge engineering - bridge design manual.pdf

Documents