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MINNESOTA DEPARTMENT OF TRANSPORTATION Bridge Office

LRFD Bridge Design Manual

MANUAL

5-392

ii

Mn/DOT BRIDGE OFFICE

LRFD Bridge Design Manual

Minnesota Department of Transportation 3485 Hadley Avenue North Mail Stop 610

Oakdale, MN 55128-3307 Phone: (651) 747-2100 Fax: (651) 747-2108

JULY 2003 OCTOBER 2003 JANUARY 2004 APRIL 2004 OCTOBER 2004 DECEMBER 2004 FEBRUARY 2005 MARCH 2005

OCTOBER 2004 LRFD BRIDGE DESIGN i

TABLE OF CONTENTS

1. INTRODUCTION..................................................................................... 1-1

1.1 Overview Of Manual 5-392 ............................................................... 1-1

1.1.1 Chronology Of Manual 5-392 ................................................... 1-1

1.1.2 Material Contained In Manual 5-392 ......................................... 1-1

1.1.3 Updates To Manual 5-392 ....................................................... 1-2

1.1.4 Format Of Manual References .................................................. 1-2

1.2 General Bridge Information .............................................................. 1-2

1.2.1 Bridge Office ......................................................................... 1-2

1.2.2 Highway Systems................................................................... 1-8

1.2.3 Bridge Numbers..................................................................... 1-8

1.2.4 Limit States To Consider In Design ......................................... 1-10

1.2.5 Ductility, Redundancy, Operational Importance ........................ 1-10

1.3 Procedures................................................................................... 1-10

1.3.1 Checking Of Mn/DOT Prepared Bridge Plans ............................. 1-10

1.3.2 Checking Of Consultant Prepared Bridge Plans ......................... 1-12

1.3.3 Schedule For Processing Construction Lettings ......................... 1-15

1.3.4 Bridge Project Tracking System.............................................. 1-16

1.3.5 Approval Process For Standards ............................................. 1-18

2. GENERAL DESIGN AND LOCATION FEATURES........................................ 2-1

2.1 Geometrics .................................................................................... 2-1

2.1.1 Bridge Geometrics.................................................................. 2-1

2.1.2 Bridge Deck Requirements ...................................................... 2-2

2.1.3 Bridge Undercrossing Geometrics ............................................. 2-7

2.1.4 Geometric Details ................................................................ 2-15

2.1.5 Bridge Railings .................................................................... 2-27

2.2 Bridge Aesthetics .......................................................................... 2-27

2.3 Preliminary Bridge Plans ................................................................ 2-27

2.3.1 General .............................................................................. 2-27

2.3.2 Bridge Type Selection ........................................................... 2-37

OCTOBER 2004 LRFD BRIDGE DESIGN ii

2.4 Final Bridge Plans and Special Provisions .......................................... 2-42

2.4.1 Final Design Instructions....................................................... 2-44

2.4.1.1 Superstructure ................................................................ 2-44

2.4.1.1.1 Framing Plan ..................................................... 2-44

2.4.1.1.2 Concrete Wearing Course .................................... 2-45

2.4.1.1.3 Diaphragms and Cross-frames ............................. 2-45

2.4.1.2 Pedestrian Bridges........................................................... 2-46

2.4.1.3 Temporary Bridges and Widenings ..................................... 2-48

2.4.1.4 Bridge Approaches........................................................... 2-49

2.4.1.5 Survey........................................................................... 2-50

2.4.1.6 Utilities .......................................................................... 2-50

2.4.1.7 Precedence of Construction Documents............................... 2-51

2.4.1.8 Design Calculation Requirements ....................................... 2-51

2.4.2 Final Plans .......................................................................... 2-52

2.4.2.1 Drafting Standards .......................................................... 2-53

2.4.2.2 Drafting Guidelines .......................................................... 2-53

2.4.2.3 General Plan and Elevation ............................................... 2-55

2.4.2.4 Bridge Layout and Staking Plan ......................................... 2-60

2.4.2.5 Standard Abbreviations .................................................... 2-63

2.4.2.6 Inclusion of Standard Bridge Details in Plan Sets.................. 2-63

2.4.2.7 Use of Bridge Standard Plans ............................................ 2-63

2.4.2.8 Standard Plan Notes ........................................................ 2-63

2.4.2.9 Quantity Notes and Pay Items ........................................... 2-64

2.4.3 Revised Sheets .................................................................... 2-65

2.5 Reconstruction Guidelines and Details .............................................. 2-66

2.5.1 Superstructure .................................................................... 2-66

2.5.1.1 Railings.......................................................................... 2-66

2.5.1.2 Wearing Course............................................................... 2-68

2.5.1.3 Expansion/Fixed Joints ..................................................... 2-68

2.5.2 Substructure ....................................................................... 2-80

2.5.2.1 Abutments...................................................................... 2-80

2.5.2.2 Piers.............................................................................. 2-80

2.5.3 Pavement ........................................................................... 2-80

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2.6 Construction Requirements............................................................. 2-86

Appendix 2-A: Bridge Type Numbers ....................................................... 2-87

Appendix 2-B: Bridge Special Provisions................................................... 2-88

Appendix 2-C: Standard Abbreviations..................................................... 2-92

Appendix 2-D: Bridge Details Part I (B-Details) ......................................... 2-94

Appendix 2-E: Bridge Details Part II ........................................................ 2-96

Appendix 2-F: Bridge Standard Plans: Culverts ......................................... 2-98

Appendix 2-G: Bridge Standard Plans: Retaining Walls ............................... 2-99

Appendix 2-H: Standard Plan Notes ....................................................... 2-100

Appendix 2-I: Standard Summary Of Quantities Notes ............................. 2-109

Appendix 2-J: Bridge Pay Items ............................................................ 2-111

Appendix 2-K: Conversion From Inches To Decimals Of A Foot .................. 2-115

3. LOADS AND LOAD FACTORS .................................................................. 3-1

3.1 Load Factors And Combinations ........................................................ 3-1

3.2 Load Modifiers ................................................................................ 3-3

3.3 Permanent Loads (Dead And Earth) ................................................... 3-3

3.4 Live Loads ..................................................................................... 3-4

3.4.1 HL-93 Live Load, LL................................................................ 3-4

3.4.2 Multiple Presence Factor, MPF .................................................. 3-4

3.4.3 Dynamic Load Allowance, IM ................................................... 3-4

3.4.4 Pedestrian Live Load, PL ......................................................... 3-4

3.4.5 Braking Force, BR .................................................................. 3-5

3.4.6 Centrifugal Force, CE.............................................................. 3-5

3.4.7 Live Load Application To Buried Structures ................................ 3-5

3.4.8 Live Load Surcharge, LS.......................................................... 3-5

3.5 Water Loads, WA ............................................................................ 3-5

3.6 Wind Loads, WS.............................................................................. 3-5

3.7 Wind on Live Load, WL .................................................................... 3-6

3.8 Earthquake Effects, EQ .................................................................... 3-6

3.9 Ice Load, IC ................................................................................... 3-6

3.10 Earth Pressure, EV, EH, Or ES........................................................... 3-6

3.11 Temperature, Shrinkage, Creep, Settlement, TU, SH, CR And SE ........... 3-7

OCTOBER 2004 LRFD BRIDGE DESIGN iv

3.11.1 General ................................................................................ 3-7

3.12 Pile Downdrag, DD .......................................................................... 3-7

3.13 Friction Forces, FR .......................................................................... 3-7

3.13.1 Sliding Bearings..................................................................... 3-7

3.13.2 Soil/Backwall Interface And Soil/Footing Interface ...................... 3-7

3.14 Extreme Event................................................................................ 3-8

3.14.1 Vehicle Collision, CT ............................................................... 3-8

3.14.2 Vessel Collision, CV ................................................................ 3-8

3.15 Uplift............................................................................................. 3-8

3.15.1 Deck Pours............................................................................ 3-9

3.16 Construction Loads.......................................................................... 3-9

3.17 Deflections..................................................................................... 3-9

4. STRUCTURAL ANALYSIS AND EVALUATION........................................... 4-1

4.1 Computer Programs ........................................................................ 4-1

4.2 Load Distribution ............................................................................ 4-2

4.2.1 Dead Load Distribution ........................................................... 4-2

4.2.2 Live Load Distribution ............................................................. 4-2

4.2.2.1 Steel And Prestressed Concrete Beams ................................. 4-3

4.2.2.2 Slab Spans And Timber Decks ............................................. 4-3

4.2.3 Sidewalk Pedestrian Live Load ................................................. 4-3

4.2.4 Pedestrian Bridge Live Load..................................................... 4-4

4.3 Load Rating.................................................................................... 4-4

4.4 Substructure Fixity.......................................................................... 4-8

4.5 Structural Models............................................................................ 4-8

4.6 LRFD Exceptions ............................................................................. 4-8

4.6.1 Curved Bridges ...................................................................... 4-9

4.6.2 Rehabilitation Projects ............................................................ 4-9

4.6.3 Railroad Bridges, And Bridges Or Structures Near Railroads ......... 4-9

5. CONCRETE STRUCTURES ....................................................................... 5-1

5.1 Materials ....................................................................................... 5-1

5.1.1 Concrete............................................................................... 5-1

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5.1.2 Reinforcing Steel.................................................................... 5-4

5.1.3 Reinforcement Bar Couplers .................................................... 5-4

5.1.4 Prestressing Steel .................................................................. 5-4

5.1.5 Post-tensioning Hardware ....................................................... 5-5

5.2 Reinforcement Details...................................................................... 5-5

5.2.1 Minimum Clear Cover and Clear Spacing ................................... 5-5

5.2.2 Reinforcing Bar Lists............................................................... 5-7

5.2.3 General Reinforcement Practices ............................................ 5-14

5.2.4 Reinforcement Bar Couplers .................................................. 5-14

5.2.5 Adhesive Anchors................................................................. 5-14

5.2.6 Shrinkage and Temperature Reinforcement ............................. 5-15

5.3 Concrete Slabs ............................................................................. 5-17

5.3.1 Geometry ........................................................................... 5-17

5.3.2 Design/Analysis ................................................................... 5-17

5.3.3 Exterior Strip....................................................................... 5-18

5.3.4 Reinforcement Layout........................................................... 5-18

5.3.5 Camber and Deflections ........................................................ 5-21

5.4 Pretensioned Concrete ................................................................... 5-21

5.4.1 Geometry ........................................................................... 5-22

5.4.2 Stress Limits ....................................................................... 5-24

5.4.3 Design/Analysis ................................................................... 5-24

5.4.4 Detailing/Reinforcement........................................................ 5-27

5.4.5 Camber and Deflection ......................................................... 5-27

5.4.6 Standard I-Beams................................................................ 5-28

5.4.7 Rectangular Beams .............................................................. 5-28

5.4.8 Double-Tee Beams ............................................................... 5-31

5.5 Post-Tensioned Concrete................................................................ 5-36

5.5.1 PT Slab Bridges ................................................................... 5-36

5.5.2 PT I-Girders ........................................................................ 5-36

5.5.3 PT Precast or Cast-In-Place Box Girders .................................. 5-36

5.6 Concrete Finishes and Coatings....................................................... 5-36

5.7 Design Examples .......................................................................... 5-37

5.7.1 Three-Span Haunched Reinforced Concrete Slab....................... 5-39

OCTOBER 2004 LRFD BRIDGE DESIGN vi

5.7.2 Prestressed I-Beam Design Example....................................... 5-71

5.7.3 Three-Span Haunched Post-Tensioned Concrete Slab Design Example ................................................................. 5-101

6. STEEL STRUCTURES............................................................................... 6-1

6.1 Materials ....................................................................................... 6-1

6.2 General Dimensions And Details........................................................ 6-3

6.3 General Design Philosophy ............................................................... 6-7

6.3.1 Shear Connectors .................................................................. 6-9

6.3.2 Fatigue................................................................................. 6-9

6.3.3 Deflections............................................................................ 6-9

6.3.4 Camber .............................................................................. 6-10

6.4 Rolled Beams ............................................................................... 6-13

6.5 Plate Girders ................................................................................ 6-13

6.5.1 High Performance Steel Girders.............................................. 6-14

6.6 Curved Girders ............................................................................. 6-14

6.7 Box Or Tub Girders ....................................................................... 6-15

6.8 Bolted Connections And Splices....................................................... 6-15

6.9 Two-Span Plate Girder Design Example............................................ 6-16

7. RESERVED

8. WOOD STRUCTURES.............................................................................. 8-1

8.1 Materials ....................................................................................... 8-1

8.1.1 Wood Products ...................................................................... 8-1

8.1.2 Fasteners And Hardware ......................................................... 8-2

8.1.3 Wood Preservatives................................................................ 8-2

8.2 Timber Bridge Decks ....................................................................... 8-3

8.2.1 General ................................................................................ 8-3

8.2.2 Geometry ............................................................................. 8-5

8.2.3 Design/Analysis ..................................................................... 8-5

8.2.4 Detailing............................................................................... 8-6

8.2.5 Camber/Deflections................................................................ 8-6

DECEMBER 2004 LRFD BRIDGE DESIGN vii

8.3 Timber Pile Caps ............................................................................. 8-6

8.3.1 Geometry ............................................................................. 8-7

8.3.2 Design/Analysis ..................................................................... 8-7

8.3.3 Detailing............................................................................... 8-7

8.3.4 Camber/Deflections................................................................ 8-7

8.4 Additional References ...................................................................... 8-7

8.5 Design Examples ............................................................................ 8-8

8.5.1 Longitudinally Laminated Timber Deck Design Example ............... 8-8

8.5.2 Design Example: Timber Pile Cap ........................................... 8-26

9. DECKS AND DECK SYSTEMS................................................................... 9-1

9.1 General ......................................................................................... 9-1

9.1.1 Deck Drainage....................................................................... 9-2

9.2 Concrete Deck on Beams ................................................................. 9-2

9.2.1 Deck Design and Detailing....................................................... 9-4

9.3 Reinforced Concrete Deck Design Example ....................................... 9-17

10. FOUNDATIONS .................................................................................... 10-1

10.1 Determination of Foundation Type and Capacity ................................ 10-1

10.1.1 Foundation Report................................................................ 10-1

10.1.2 Foundation Recommendations ............................................... 10-1

10.2 Piles............................................................................................ 10-3

10.3 Drilled Shafts ............................................................................... 10-5

10.4 Footings ...................................................................................... 10-8

10.4.1 General .............................................................................. 10-8

10.4.2 Footing Supported on Piling or Drilled Shafts............................ 10-9

10.4.3 Spread Footings................................................................. 10-10

10.5 Pile Bent Piers and Abutments ...................................................... 10-11

10.6 Evaluation of Existing Pile Foundations when Exposed by Scour ......... 10-11

10.7 Structure Excavation and Backfill .................................................. 10-13

OCTOBER 2004 LRFD BRIDGE DESIGN viii

Appendix 10-A: Sample Bridge Construction Unit Recommendations (Future Content) .......................................................... 10-14

11. ABUTMENTS, PIERS, AND WALLS ....................................................... 11-1

11.1 Abutments ................................................................................... 11-1

11.1.1 Integral or Contraction Abutments.......................................... 11-3

11.1.2 Parapet Abutments............................................................... 11-6

11.1.2.1 Low Abutments ............................................................... 11-9

11.1.2.2 High Abutments .............................................................. 11-9

11.1.3 Wingwalls ......................................................................... 11-12

11.1.4 Approach Panels ................................................................ 11-20

11.2 Piers ......................................................................................... 11-21

11.2.1 Geometrics ....................................................................... 11-21

11.2.2 Columns ........................................................................... 11-21

11.2.3 Cap.................................................................................. 11-21

11.2.4 Crash Walls....................................................................... 11-22

11.2.5 Design and Reinforcement................................................... 11-23

11.2.6 Miscellaneous .................................................................... 11-24

11.2.6.1 Pile Bent ...................................................................... 11-25

11.3 Retaining Walls........................................................................... 11-25

11.3.1 Cantilever Retaining Walls ................................................... 11-25

11.3.2 Counterfort Retaining Walls ................................................. 11-25

11.3.3 Anchored Walls.................................................................. 11-26

11.3.4 Mechanically Stabilized Earth Walls....................................... 11-26

11.3.5 Prefabricated Modular Walls................................................. 11-28

11.3.6 Timber Noise Walls on Retaining Walls .................................. 11-28

11.3.7 Cantilevered Sheet Pile Walls............................................... 11-28

11.3.8 Design Charts of Cantilevered Sheet Pile Soil Retention Walls for Temporary Applications.......................................... 11-29

11.4 Design Examples ........................................................................ 11-39

11.4.1 High Parapet Abutment Design Example................................ 11-39

11.4.2 Retaining Wall Design Example ............................................ 11-71

11.4.3 Three-Column Pier Design Example ...................................... 11-93

OCTOBER 2004 LRFD BRIDGE DESIGN ix

12. BURIED STRUCTURES.......................................................................... 12-1

12.1 Geotechnical Properties ................................................................. 12-1

12.2 Box Culverts ................................................................................ 12-2

12.2.1 Precast ............................................................................... 12-2

12.2.2 Cast-In-Place ...................................................................... 12-4

12.3 Design Guidance........................................................................... 12-4

12.4 Arch Or 3-Sided Structure Design Data ............................................ 12-6

12.5 Design Criteria for Long-Span Corrugated Steel Structures ............... 12-14

12.6 10' x 10' Precast Concrete Box Culvert Design Example.................... 12-18

13. RAILINGS ........................................................................................... 13-1

13.1 Materials ..................................................................................... 13-1

13.2 Design Requirements..................................................................... 13-1

13.2.1 Traffic Railing ..................................................................... 13-8

13.2.2 Pedestrian/Bicycle Railing...................................................... 13-9

13.2.3 Combination Railing ........................................................... 13-10

13.2.4 Protective Screening........................................................... 13-10

13.2.5 Architectural/Ornamental Railings ........................................ 13-11

13.3 Design Examples ........................................................................ 13-12

13.3.1 F Rail Design Example ..................................................... 13-12

13.3.2 Adhesive Anchor Design Example ......................................... 13-27

14. JOINTS AND BEARINGS ...................................................................... 14-1

14.1 Bridge Movements and Fixity .......................................................... 14-1

14.2 Expansion Joints .......................................................................... 14-2

14.2.1 Thermal Movements ............................................................. 14-2

14.2.2 Expansion Joint Opening ....................................................... 14-2

14.2.3 Expansion Joint Detailing ...................................................... 14-3

14.2.4 Modular Expansion Joints ...................................................... 14-3

14.3 Bearings ...................................................................................... 14-4

14.3.1 Loads and Movements .......................................................... 14-4

14.3.2 Bearing Details .................................................................... 14-4

14.3.3 Elastomeric Bearings ............................................................ 14-5

FEBRUARY 2005 LRFD BRIDGE DESIGN x

14.3.3.1 Design ........................................................................... 14-6

14.3.3.1.1 Size and Stability ............................................... 14-6

14.3.3.1.2 Minimum Compressive Load ................................ 14-7

14.3.3.2 Fixed Bearings ................................................................ 14-7

14.3.3.3 Expansion Bearings.......................................................... 14-8

14.3.4 Pot Bearings........................................................................ 14-8

14.3.5 Other Types of Bearings ....................................................... 14-8

14.4 Curved Plate Design ...................................................................... 14-9

14.5 Bearing Plate Design ................................................................... 14-10

14.6 Sole Plate Design (Steel Beams) ................................................... 14-10

14.7 Tables ....................................................................................... 14-11

14.8 Design Examples ........................................................................ 14-17

14.8.1 Fixed Elastomeric Bearing Design Example ............................ 14-17

14.8.2 Expansion Elastomeric Bearing Design Example...................... 14-25

A. MEMOS

#2005-01 LRFD and Bridge Load Rating Issues ...................(dated February 14, 2005)

JULY 2003 LRFD BRIDGE DESIGN 1-1

This section contains general information about the manual along with a general description of the Bridge Office and its procedures. It also includes guidance on use of the ductility, redundancy, and operational importance factors given in LRFD 1.3.3 through 1.3.5. Mn/DOT utilizes a decimal numbering system to classify documents. The 5 before the hyphen represents a publication related to engineering functions. The 300 series of documents is assigned to the Bridge Office; the 90 series indicates that this is a Manual. The last digit 2 specifies that the subject matter of the document is Design. The original bridge design manual, numbered 5-392, provided guidance for the design of highway structures in Minnesota in accordance with allowable stress design methods. Subsequently, it has received periodic updates as design methods have changed. This version of the Bridge Design Manual contains significant changes. It presents Mn/DOTs design practices in conformance with a new design methodology, Load and Resistance Factor Design (LRFD), and also contains fifteen comprehensive design examples. Use of this manual does not relieve the design engineer of responsibility for the design of a bridge or structural component. Although Bridge Office policy is presented here for numerous situations, content of the manual is not intended to be exhaustive. Therefore, use of this manual must be tempered with sound engineering judgement. After the introductory material provided in this section, the manual contains material arranged around the following section headings. To simplify locating material, section numbers correspond to those used in the LRFD specifications:

1. Introduction 2. General Design and Location Features 3. Loads and Load Factors 4. Structural Analysis and Evaluation 5. Concrete Structures 6. Steel Structures 7. Reserved 8. Wood Structures 9. Decks and Deck Systems 10. Foundations 11. Abutments, Piers, and Walls 12. Buried Structures

1. INTRODUCTION

1.1 Overview of Manual 5-392

1.1.1 Chronology of Manual 5-392

1.1.2 Material Contained in Manual 5-392

JULY 2003 LRFD BRIDGE DESIGN 1-2

13. Railings 14. Joints and Bearings Memos

This manual will be updated multiple times each year as procedures are updated and new information becomes available. Current files for each section of the manual are available on the Bridge Office Web site [http://www.dot.state.mn.us/bridge/]. Each section of the manual contains general information at the start of the section. Design examples (if appropriate) are located at the end of each section. The general content is divided into subsections that are identified with numerical section labels in the left margin. Labels for design example subsections are identified with alphanumeric labels in the left hand margin. The left hand margin also contains references to LRFD Design Specification Articles, Equations, and Tables. These references are enclosed in square brackets. Within the body of the text, references to other sections of this manual are directly cited (e.g. Section 10.1). References to the LRFD Specifications within the main body of the text contain a prefix of: LRFD. A bridge is defined under Minnesota Rule 8810.8000 as a structure having an opening measured horizontally along the center of the roadway of ten feet or more between undercopings of abutments, between spring line of arches, or between extreme ends of openings for multiple boxes. Bridge also includes multiple pipes where the clear distance between openings is less than half of the smaller contiguous opening. In accordance with Minnesota Statute 15.06 Subd. 6, the Commissioner of Transportation has delegated approval authority for State Preliminary Bridge Plans, and State, County and City Final Bridge Plans to the State Bridge Engineer. Plans for all bridge construction or reconstruction projects located on the Trunk Highway System, and plans on County or City highways funded fully or in part by state funds shall be approved by the State Bridge Engineer. The Bridge Office is responsible for conducting all bridge and structural design activities and for providing direction, advice, and services for all

1.1.3 Updates to Manual 5-392

1.2 General BridgeInformation

1.2.1 Bridge Office

1.1.4 Format ofManual References

JULY 2003 LRFD BRIDGE DESIGN 1-3

bridge construction and maintenance activities. The responsibilities include:

Providing overall administrative and technical direction for the office.

Reviewing and approving all preliminary and final bridge plans prepared by the office and consultants.

Representing the Department in bridge design, construction and maintenance matters with other agencies.

The office is under the direction of the State Bridge Engineer. It is composed of sections and units as shown on the organizational chart (Figure 1.2.1.1). Each of these subdivisions with their principal functions is listed as follows:

A. Bridge Design Section Responsible for the design, plans, and special provisions activities for bridges, and miscellaneous transportation structures. 1. Design Unit

a. Designs and drafts bridge plans. b. Reviews bridge plans prepared by consulting engineers. c. Prepares special provisions for bridge plans. d. Designs and drafts plans for miscellaneous highway structures. e. Provides technical assistance, designs, and plans for special

bridge and structural problems. 2. Bridge Standards and Research Unit

a. Provides design aids and standards for the office and for consultants, counties, and cities.

b. Coordinates the development and users of computer programs with data processing systems.

c. Supports computer users throughout the office and manages the local area network.

d. Provides oversight for research projects, which involve the Office of Bridges and Structures.

3. Design/Build Unit a. Provides oversight of design/build projects.

4. LRFD Implementation a. Maintains LRFD Bridge Design Manual. b. Provides support to office and consulting engineers concerning

LRFD issues.

B. Bridge Planning Section Responsible for program, cost estimates, preliminary bridge plan activities for Trunk Highways and review of state aid bridges.

JULY 2003 LRFD BRIDGE DESIGN 1-4

1. Bridge Agreements and Estimates Unit a. Selects and negotiates with consulting engineers and

administers engineering agreements for the preparation of bridge plans.

b. Provides liaison between the office and the consulting engineer retained to prepare bridge plans.

c. Coordinates public and private utility requirements for bridges. d. Prepares preliminary, comparative and final cost estimates. e. Maintains and provides current program and plan status

records. 2. Preliminary Plans

a. Conducts preliminary studies from layouts and develops preliminary bridge plans.

b. Provides liaison with district and central office road design through the design stage.

c. Obtains required permits from other agencies for bridges. 3. State Aid Bridge Unit

a. Reviews bridge plans and special provisions for county and municipal state aid projects.

b. Provides technical assistance to counties and municipalities, when requested, for nonparticipating projects.

C. Bridge Construction and Maintenance Section

Responsible for bridge construction and maintenance specifications, and bridge construction and maintenance advisory service activities to the office and to the job site. 1. Construction and Maintenance Unit; North, Metro and South

Regions a. Provides construction and maintenance advisory service to

bridge construction and maintenance engineers in the field. b. Writes bridge construction and maintenance specifications,

manuals and bulletins. c. Writes and maintains the file of current special provisions for

bridge construction and maintenance. d. Performs preliminary, periodic and final review of bridge

construction and maintenance projects and makes recommendations.

e. Reviews bridge plans and special provisions prior to lettings and makes recommendations.

f. Aids municipal and county engineers with bridge construction and maintenance problems, upon request.

g. Provides foundation design including selection of pile type, length, design load, and foundation preparation.

JULY 2003 LRFD BRIDGE DESIGN 1-5

h. Reviews bridge improvement projects and prepares recommendations for scope of work.

2. Bridge Ratings Unit a. Makes bridge ratings and load postings analysis for existing

bridges and maintains the records. b. Reviews and approves special load permit requests.

3. Structural Metals Inspection Unit a. Provides inspection services for structural metals, fabrication

and assembly to ensure conformity with plans and specifications.

4. Fabrication Methods Unit a. Reviews and approves structural metals shop drawings

submitted by fabricators. b. Provides fabrication advisory service to designers, fabricators

and field construction and maintenance personnel. c. Provides overhead sign design services to the Office of Traffic

Engineering, including the design of bridge-mounted sign trusses.

5. Bridge Management Unit a. Maintains inventory and inspection data for the 19,600 bridges

in Minnesota. Works with all agencies to make certain appropriate data is collected.

b. Responsible for implementing bridge management systems to provide information on bridges for maintenance, repair, rehabilitation and replacement.

6. Bridge Inspection Unit a. Provides expert assistance to the Districts in organizing and

conducting inspections of complex bridges, special features, and fracture critical bridges.

b. Conducts quality assurance inspections of all agencies responsible for bridge inspections in Minnesota.

c. Reviews, recommends and provides bridge inspection training for District, county, and municipal bridge inspectors.

D. Hydraulic Engineering Section

Responsible for providing statewide hydraulic engineering services that include design, construction and maintenance activities. In addition, the section provides leadership in the development and implementation of hydraulic automation technology, establishes policy pertaining to hydrology and hydraulics, prepares design aids, provides client training, participates in research projects, and represents the department on state and national committees. 1. Bridge Design Hydraulics Unit

JULY 2003 LRFD BRIDGE DESIGN 1-6

a. Provides bridge and culvert waterway designs for trunk highway, county, city and township projects.

b. Analyzes and evaluates inplace bridges for scour. c. Provides technical assistance to counties and municipalities

upon request. d. Provides training in hydrology and hydraulics.

2. Road Design Hydraulics Unit a. Evaluates and codes all bridges over water for scour. b. Provides technical assistance to Districts on all aspects of

drainage design. c. Reviews and cost prorates storm drains on the municipal and

county state aid system. d. Coordinates the review of new products and development of

specifications and policies pertaining to their use. 3. Hydraulics Automation Unit

a. Provides leadership and technical direction for managing the statewide hydraulic automation effort.

b. Develops and implements the means to integrate the hydraulic design process with the road design process.

c. Develops, implements, and supports a hydraulic information system to facilitate the sharing of hydraulic data among all users and stakeholders.

e. Provides statewide training and support in the implementation and use of hydraulic automation techniques.

JULY 2003 LRFD BRIDGE DESIGN 1-7

JULY 2003 LRFD BRIDGE DESIGN 1-8

Highways throughout the nation are divided into systems. These system designations are important to know because design standards can vary between the systems. The various highway systems are classified according to the Agency that has responsibility for their improvement, maintenance and traffic regulation enforcement. Listed below are the jurisdictional divisions in Minnesota: 1. Trunk Highway System

The Trunk Highway System consists of all highways, including the Interstate routes, under the jurisdiction of the State of Minnesota. These routes generally are the most important in the state, carry the greatest traffic volumes, and operate at the highest speeds.

2. County Highway System

The County Highway System is made up of those roads established and designated under the authority of the county board. They generally are the more important routes within a county that are not on the Trunk Highway System.

3. Township Road System

The Township Road System is made up of the roads established under the authority of the town board. They generally are of local importance.

4. Municipal Street System

The Municipal Street System is all roads within a municipality not designated as a trunk highway or county road. They are generally of local importance.

All publicly owned bridges either on or over a trunk highway and over 10 feet in length measured along the centerline of the highway are assigned a number for identification and cost accounting purposes. The numbering scheme followed in assigning bridge numbers depends on the time of construction. With few exceptions, the numbering procedure is as follows: 1. Prior to about 1950, all bridges were numbered consecutively from 1

to 9999 as they were constructed. The 8000 series was used for culverts over 10 feet in length (measured along the centerline of the highway). The 7000 series was reserved for county bridges at trunk highway intersections. Five-digit bridge numbers beginning with L or R designate bridges in local bridge systems.

1.2.2 Highway Systems

1.2.3 Bridge Numbers

JULY 2003 LRFD BRIDGE DESIGN 1-9

2. Since about 1950, a five-digit number has been assigned to each

bridge as it was constructed. The first two digits coincide with the county number (01-87) in which the bridge is located (99 refers to temporary bridges). The last three digits are assigned consecutively using the following guidelines:

a. 001-499 are used for regular trunk highway bridges. b. 500-699 are used for county bridges. c. 700-999 are used for interstate bridges (any bridge on or

over the interstate system). 3. In 1991, additional numbers were required for bridges on the state

aid system in Hennepin County and for interstate bridges in Hennepin County. To allocate more numbers for bridges on the local system an alpha character is used as the third character of the bridge number. For example, the next bridge number after Bridge No. 27699 will be Bridge No. 27A00. Note that this happens only after 500 and 600 series have been exhausted.

To allocate more numbers on the Interstate road system, the 400 series of numbers will be used along with the 700, 800, 900's presently used. For a bridge number XXYZZ, the following now applies: XX = county number (99 = Temporary Bridge) Y = 0, 1, 2, 3, or R, T, U (for Trunk Highway Bridges) Y = 4, 7, 8, 9, or V, or W (for Interstate Bridges) Y = X and Y (Trunk Highway or Interstate Culverts) Y = 5 or 6 or A through H (for non-trunk highway Bridges) Y = J through N, and P, Q (for non-trunk highway Culverts) ZZ = Sequence number (00 through 99)

4. In cases of twin bridges, a westbound or southbound lane bridge is

generally assigned a lower number than an eastbound or northbound lane bridge.

All bridge numbers are assigned by the Bridge Office (phone 651-747-2122). A complete listing of all numbered bridges is available in computer printout form entitled Minnesota Trunk Highway Bridge Log- Statewide Listing.

JULY 2003 LRFD BRIDGE DESIGN 1-10

Bridge designs shall typically consider Strength, Service, Extreme Event, and Fatigue limit states. The limit state checks will vary with the component under consideration. Not all elements will require consideration of all limit states. For example, the fatigue limit state need not be considered for fully prestressed pretensioned elements. For most structures and structural elements the load modifiers for ductility, redundancy, and operational importance shall be 1.00. Exceptions are noted below: 1. The ductility factor shall be 1.05 for prestressed concrete through-

girder pedestrian bridges when they are over-reinforced. 2. The importance factor shall be 1.05 for a bridge which satisfies any

one of the following three criteria: 1) it is a major river crossing, 2) its ADT is greater than or equal to 40,000, or 3) it is a new mainline interstate bridge.

3. The importance factor shall be 0.95 for bridges with an ADT less than 500.

This section covers the Bridge Office procedures for checking of bridge plans, scheduling of projects, and revising or creating standards. The general practice of most engineering offices is to require that designs they produce be checked before they are reviewed and certified by the Engineer in Responsible Charge. Although this practice has always been required for structures designed for Mn/DOT, it is recognized that the quality of the checking process often varies according to time restraints, confidence in the designer, and the instructions given to the checker. Therefore, in order to maintain a consistent design checking process the following guidance is given for routine bridge designs. For more complex or unusual designs, the checker is advised to discuss additional requirements with the design unit leader. Also, the checking process described is not meant to apply to the check or review functions required for Mn/DOT review of consultant plans (see Section 1.3.2.) or for construction false work reviews. (See the Bridge Construction Manual.) Three types of design checking will apply: a. An independent analysis of the completed design. b. A check of original design computations for mathematical accuracy,

application of code, and accepted engineering practice, and

1.2.5 Ductility, Redundancy, Operational Importance [1.3.3] [1.3.4] [1.3.5]

1.3 Procedures

1.3.1 Checking of Mn/DOT Prepared Bridge Plans

1.2.4 Limit States to Consider in Design

JULY 2003 LRFD BRIDGE DESIGN 1-11

c. A review of drafted details for constructibility, and accepted engineering practice.

Generally, an independent analysis to confirm the adequacy of the complete design is preferred. Significant differences should be discussed and resolved before the plan is certified. The separate set of calculations should be included with the design file as a record of the completed design check. When circumstances prevent a complete independent analysis, as a minimum, an independent analysis shall be completed for the following: a. Live and dead loads b. Critical beam lines c. A pier cap d. A pier footing e. Main reinforcement for high abutments f. An abutment footing However, for the elements not independently analyzed, the original computations should be checked for mathematical accuracy of original design computations, applications of code, and accepted engineering practice. Checked computations should be initialed by the checker, and the independent analysis should be included in the design file. When doing a separate analysis, the checker may make simplifying assumptions to streamline the checking process. However, when major differences are found, results must be discussed and resolved with the designer. For instance, for normal piers, piling might be analyzed for dead and live loads only if lateral loads appear to have been reasonably applied in the original computations or the AISC Beam Diagram and Formula Tables may be used to approximate pier cap moment and shear. Whether the check is a completely independent analysis or a minimal analysis combined with a computations check, some details, such as the reinforcing details in a wall corner, also require review by the checker. Often referencing old bridge plans with similar details allows the checker to compare the current design to details that have performed well in the past.

JULY 2003 LRFD BRIDGE DESIGN 1-12

Consultant prepared bridge plans are created by private engineering firms through contracts with the Department. The finished plans are complete to the extent that they can be used for construction.

Since these plans receive final approval of the State Bridge Engineer, there must be assurance that the plans are geometrically accurate and buildable; structural design is adequate and design codes have been correctly applied; proper direction is given to the construction contractor; and all construction costs are accounted for. Plan errors may cause costly construction delays or safety may be compromised by an inadequate design. To keep consultant plan reviews consistent and timely, a procedure was developed as a guide that assigns priority to specific items in the plans. The overall review includes a Thorough Check and Cursory Review of various items. The distinction between Thorough Check and Cursory Review is as follows: Thorough Check refers to performing complete mathematical computations in order to identify discrepancies in the plans, or conducting careful comparisons of known data and standards of the Project with values given in the plan. Cursory Review refers to a comparative analysis for agreement with standard practice and consistency with similar structures, all with application of engineering judgment. Mathematical analysis is not required, but may be deemed necessary to identify the extent of a discrepancy. The review procedure is listed on the CONSULTANT BRIDGE PLAN REVIEW form following this section. Headings on this list are defined as follows: PARTIAL PLAN: In order to assure that the consultant is proceeding in the right direction, an early submittal of the plan is required. This submittal usually consists of the General Plan and Elevation sheet showing the overall geometry of the structure and the proposed beam type and spacing; the Bridge Layout Sheet; the Framing Plan sheet; and the Bridge Survey sheets. Errors and inconsistencies found in this phase can be corrected before the entire plan is completed. For example, a framing plan, including the proposed beams, must be assured as workable on the partial plan before the consultant gets deep into the design of the remainder of the bridge.

1.3.2 Checking of Consultant Prepared Bridge Plans

JULY 2003 LRFD BRIDGE DESIGN 1-13

FINAL PLAN: A final plan should be complete in all areas to the extent that it can be certified by the designer, although a certification signature is not required for this phase. THOROUGH CHECK: Items indicated for checking on the consultants partial plan must be correct. Given geometry must fit the roadway layout. Most of this information can be checked using data from the approved preliminary plan. Approval of the partial plan will indicate that Mn/DOT is satisfied with the geometry and proposed structure, and the consultant may proceed with further development of the plan. For the final plan, obvious drafting and numerical errors should be marked to point out the errors to the consultant, however, the reviewer should not provide corrections to errors in the consultants numerical computations. Checking on the final plan should be thorough to eliminate possible errors that may occur, such as the pay items in the Schedule of Quantities. Plan notes and pay items can be difficult for a consultant to anticipate because of frequent changes by Mn/DOT. Pay items must be correct because these are carried throughout the entire accounting system for the Project. Plan (P) quantities must also be correctly indicated. CURSORY REVIEW: Normally, a cursory review would not require numerical calculations. This type of review can be conducted by reading and observing the contents of the plan in order to assure the completeness of the work. The reviewer should be observant to recognize what looks right and what doesnt look right. Obvious errors or inconsistencies on any parts of the plan should be marked for correction. Although structural design is usually the major focus of any plan, most consultants are well versed in design procedures and should need only minimal assistance from our office. A comparison of the consultants calculations with the plan details should be performed to assure that the plans reflect their design and that the applicable codes are followed. An independent design by our office is time consuming and is not recommended unless there is a reasonable doubt as to the adequacy of the consultants design. NO REVIEW: A thorough review of these items would be time-consuming and may not produce corrections that are vital to construction; therefore, it is recommended that little or no time be spent on the listed items. Numerous errors can occur in the Bills of Reinforcement and quantity values. However, checking this information is also time-consuming, hence the burden of providing correct data should be placed on the consultant.

JULY 2003 LRFD BRIDGE DESIGN 1-14

CONSULTANT BRIDGE PLAN REVIEW Br. No. ________ RTE ____ DATE: PARTIAL PLAN REC'D. _____ DATE FINAL PLAN REC'D. ______

DESIGN GROUP _______________________ CONSULTANT ______________________________

No. OF SHEETS IN PLAN ______ DESCRIBE COMPLEXITY_________________________________

EST. REVIEW TIME BY DESIGN GROUP ________(hrs.) ACTUAL REVIEW TIME __________(hrs) PARTIAL PLAN FINAL PLAN

THOROUGH CHECK THOROUGH CHECK

Horizontal and vertical clearances Pay items and plan quantities

Stations and elevations on survey line Project numbers

Deck and seat elevations at working points Design data block & Rating on GP&E sheet

Deck cross-section dimensions Job number

Working line location and data Certification block

Coordinates at working points and key stations Standard plan notes

Substructure locations by station Concrete mix numbers

Framing Plan Construction joint locations

Conformance to preliminary plan Prestressed beam design if inadequate design is suspected

Design loads Bridge seat elevations at working points

Utilities on bridge

Existing major utilities near bridge

CURSORY REVIEW

Steel beam splice locations and diaphragm spacing; flange plate thickness increments (enough to save 800+ # of steel)

Abutment and Pier design to be checked against consultants calculations Conformance to foundation recommendations.

Pile loads and earth pressures. Check against consultants calculations. CURSORY REVIEW Rebar series increments (min. 3)

Proposed precast beams [per 5-393.509(2)] Interior beam seat elevations

Precast conformance to industry standards Bottom-of-footing elevations (for adequate cover)

Proposed steel beam sections Railing lengths and metal post spacing (check for fit)

Use of B-details and standard plan sheets

Conformance to aesthetic requirements

Notes General, construction, reference, etc.

Quantity items on tabulations

Precast beam design (Check against consultants calculations) NO CHECK OR REVIEW REQUIRED

Diagonals on Layout sheet

Figures in Bills of Reinforcement

Bar shapes and dimensions

Rebar placement dimensions

Bar marks on details against listed bars

Quantity values (including total of tabulations)

JULY 2003 LRFD BRIDGE DESIGN 1-15

To meet the Departments schedule requirements for construction lettings, the following schedule for processing bridge plans, special provisions and estimates must be followed. This schedule applies to all projects: Federal Aid, State Funds and Maintenance. In general, processing of bridge plans, special provisions and estimates for lettings shall be given priority over all other work, and every effort must be made to complete the processing in advance of the times shown, which are deadlines.

SCHEDULE AND REMARKS

DEADLINE TIME BEFORE LETTING DATE

Federal Project State Project

Bridge plans complete to the extent that processing can be completed on schedule.

14 Weeks (Friday)

12 Weeks (Friday)

Preliminary bridge pay items and quantities for estimate (to Estimating Unit Design Services)

13 Weeks (Friday)

11 Weeks (Friday)

Bridge plan and special provisions review Complete (by Bridge Construction Unit)

13 Weeks (Friday)

11 Weeks (Friday)

Bridge special provisions complete, other Information or material for inclusion in Roadway Special Provisions complete (to Special Provisions & Final Processing Unit Design Services)

12 Weeks (Friday)

10 Weeks (Friday)

Bridge plans complete, approved and dated (to Office Management Unit)

12 Weeks (Friday)

10 Weeks (Friday)

Final bridge pay items and quantities for estimate (to estimating Unit - Design Services)

12 Weeks (Friday)

10 Weeks (Friday)

Final computer runs for bridge estimate during 9th week during 8th week

Office copy and final bridge plans (Bridge plans to Special & Final Processing Unit - Design Services for submittal to FHWA)

8 1/2 weeks (Tuesday)

7 weeks (Friday)

Federal Project to FHWA 7 1/2 weeks (Tuesday)

7 weeks (Friday)

Preliminary advertisement 6 1/2 weeks (Tuesday)

6 weeks (Friday)

Final advertisement 5 1/2 weeks (Tuesday)

5 weeks (Friday)

Sale of plans and proposals 5 weeks (Friday) 5 weeks (Friday)

Last date for mailing letter addendums by Special Provisions & Final Processing Unit Design Services

10 days (Wednesday)

10 days (Wednesday)

1.3.3 Schedule for Processing Construction Lettings

JULY 2003 LRFD BRIDGE DESIGN 1-16

Completing a bridge design project for contract letting is a multiple step process that involves input from a variety of work units and personnel. To follow the process of these projects, the following major milestones shown in Tables 1.3.4.1 and 1.3.4.2 are tracked in the Bridge Program and Project Management System (PPMS). The project typically begins in the Preliminary Plan Unit, continues through a Bridge Final Design Unit, and is completed with the Engineers Estimate. The progress and activities completed on active bridge projects are updated monthly.

Table 1.3.4.1 PPMS Activities for Mn/DOT Prepared Bridge Plans

PPMS ACTIVITY NO.

COMPLETED ACTIVITY

% PROJECT COMPLETED

0012 0020 0022 0023 0025 0030 0031 0035 0040 0045 0050

0076 0080 0085 0090

Program Estimate Bridge Survey Bridge Hydraulics Bridge Grades (Packet) Bridge Foundations Bridge Construction Foundation Review Bridge Aesthetics Recommendation Bridge Preliminary Plan District Letter & Prelim. Bridge Estimate Bridge FHWA Approval Final Bridge Plan

Designed: Drawn: Checked:

Bridge Plan Specifications Bridge Plan Review by Bridge Construction Bridge Plan Signed Bridge Engineers Estimate

0 % 5 % 6 % 8 %

13 % 14 % 14 % 15 % 20 % 20 %

20 - 40 % 40 - 65 % 65 - 85 %

90 % 90 % 95 %

100 %

1.3.4 Bridge Project Tracking System

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Table 1.3.4.2 PPMS Activities for Consultant Prepared Bridge Plans

PPMS ACTIVITY NO.

COMPLETED ACTIVITY

% PROJECT COMPLETED

0012 0019 0020 0022 0023 0025 0030 0031 0035 0040 0045 0060 0062 0064 0066 0068 0070 0075 0076 0080 0085 0090

Program Estimate Bridge Consultant Pre Design Start Bridge Survey Bridge Hydraulics Bridge Grades (Packet) Bridge Foundations Bridge Construction Foundation Review Bridge Aesthetics Recommendation Preliminary Plan District Letter & Bridge Prelim. Estimate Bridge FHWA Approval Bridge Consultant Start Consultant Partial Plan Delivery Mn/DOT Review Partial Plan Consultant Final Plan Delivery Mn/DOT Review Final Plan Consultant Final Plan In Tracing Backcheck Bridge Plan Specifications Bridge Plan Review by Bridge Construction Bridge Plan Signed Engineers Estimate

0 % 3 % 5 % 6 % 8 %

13 % 14 % 14 % 15 % 20 % 20 % 20 % 25 % 30 %

30 - 80 % 85 % 88 % 88 % 90 % 90 %

100 % 100 %

JULY 2003 LRFD BRIDGE DESIGN 1-18

1.3.5 Approval Process for Standards

NEED FOR NEW ORREVISED STANDARD

INPUT FROM S.S .R.C . INPUT FROM BRIDGEDESIG N ENG INEER

INPUT FROMCON SU LTANTS,INDUSTRY, ANDOTHER M n/DOT

OFFICES

INPUT FROM BRIDGESTANDARDSENG INEER

INPUT FROM BRIDG EDESIGN UN ITS

R. & D . COM MITTEEFOR POLICY AND APPROVAL

TO M AKE CHANGES TOSTANDARD OR DEVELOP

A N EW STANDARD

IDEA IS SCRAPPED NO

NEWSTAN DARD

DEVELOPED BYSTANDARDS

UNIT , DESIG NUN IT OR

CONSULTANT

S.S.R .C ., W ITHSTANDARDSUNIT, M AKESCHANGES TOSTAN DARD

STANDARDGOES TOR. & D .

COMM ITTEE FORAPPROVAL

THE W ORDM ODIFIED AND AREVISION DATE IS

ADDED TOSTANDARD.

STAN DARD IS M ADEAVAILABLE.

COMM ENTS RESOLVED ANDCHANGES M ADE.

STANDARD IS SEN T TOSTATE BRIDGE EN GINEER

FOR APPROVAL. A COPY ISSENT TO THE STANDARDS

UNIT .

YELLOWROUTIN GSH EET IS

DEVELOPED BYBRIDG E

STANDARDSENG INEER

REVISEDSTANDARD

AFFECTS ONLYBRIDGEOFFICE

NO

YES

M ODIFY

ACCEPT

APPROVALDATE AN D

SIGNATU READDED TO

STANDARD.

TRANSM ITTAL LETTERDEVELOPED BY

BRIDGE STANDARDSENG INEER AND

SIG NED BY STATEBRIDGE ENGIN EER.

TRANSM ITTAL LETTERAND STANDARD SENTTO PRINTER. COPIES

ENTERED INTOSTANDARDS UNIT

FILE .

ARCH IVE OLDSTANDARD

W ITHBACKG ROUNDOF CHANG ES

M AN UAL INSERTSRECEIVED BY U SERS

FOR PLACEM ENTINTO M ANUALS.

STAN DARD IS SENT OUT ONYELLOW TO OTHER OFFICES

W ITHIN M n/DOT AND TO BRIDGEOFFICE PERSONNEL. THE W ORDM ODIFIED AN D REVISION DATE

IS REM OVED BEFOREDISTRIBU TION .

CHANGESREQUESTED BYBRIDG E OFFICE

AND OTHEROFFICES ARE

M ADE.

M INOREDITORIALCHANGESM ADE TO

STANDARD

N O

REVISIONDATE IS M ORE

TH AN ON EYEAR OLD

YES

M ODIFY

YES

APRIL 2004 LRFD BRIDGE DESIGN 2-1

2. GENERAL DESIGN AND LOCATION FEATURES

2.1 Geometrics

2.1.1 Bridge Geometrics

The design of a bridge typically takes place in two major phases of work: preliminary design and final design. During preliminary design, the structure type, the foundation type, the aesthetics, and the primary geometry for the bridge are determined. During final design, specific details for all of the elements of the bridge are developed and presented in the plan set. These details include material descriptions, quantities, and geometric information. Final plan sets are typically assembled in an order that roughly follows the order of construction: from the ground up. This section of the manual contains a large amount of information useful for the preparation and assembly of plans for a project. To facilitate the production of plans and standardize the content of bridge plan sets, special provisions, B-Details, standard plans, standard plan notes, and standard pay items have been prepared by the Bridge Office. Appendices to Section 2 identify the material available. As the name of the section implies, content for this section is general in nature. Guidance for the design of specific structural elements (e.g. decks, retaining walls, etc.) is provided elsewhere in the manual. Definitions For discussion of bridge geometrics in this section, roadways are classified as Mainline Highways, Ramps, Local Roads, and Local Streets. Each of these four groups is further classified under either Urban or Rural Design. The following definitions apply: Mainline Highways Roadways that carry through traffic lanes for

freeways, expressways, and primary and secondary highways. Local Roads Rural roads off the trunk highway system. Local Streets Urban roads off the state trunk highway system. Ramps Segments of roadway connecting two or more legs at an

interchange. Urban Design Roadways with curbs on the right and/or left sides. Rural Design Roadways without curbs. Median Width The distance between the edges of opposing through

traffic lanes. Auxiliary Lane A lane adjoining a through traffic lane for a purpose

supplementary to through traffic movement such as truck climbing, weaving, speed change or turning.

APRIL 2004 LRFD BRIDGE DESIGN 2-2

2.1.2 Bridge Deck Requirements

General Criteria The width of the bridge deck and the typical section at the bridge undercrossing are determined by the classification and geometrics of the approaching roadway. The geometrics of the approaching roadway are to be carried over and under the bridge to the maximum extent practicable. Rural design is considered the desirable design and will be used in all rural areas and in urban areas where sufficient right of way is available or can be obtained. Urban design geometrics (curbed roadways) are slightly more restrictive and are therefore used at locations where extensive right-of-way cost or other unusual conditions are controlling factors. The discussion of geometric details included in this section describes bridge deck geometrics separately from bridge undercrossing geometrics. For side clearances at certain undercrossing situations, both a desirable and a minimum section are shown. Incorporation of the desirable section at undercrossings is mandatory unless approved by the Preliminary Bridge Plans Engineer. Application of Standards The geometrics shown apply specifically to new work. However, use of these geometrics is also highly desirable when upgrading or widening existing facilities and should be incorporated in these situations. Bridge deck geometrics on the local road system must also comply with State-Aid for Local Transportation Operations Rules, Chapter 8820. Responsibility The Preliminary Bridge Plans Engineer will be responsible for assuring that the geometric standards in this section are followed. Where a deviation from the standard is necessary, a written description of the deviation shall be prepared by the Preliminary Bridge Plans Engineer and submitted to the State Bridge Engineer when submitting the Preliminary Bridge Plan for acceptance. Bridge Width Criteria Roadway cross sections that approach bridges will normally provide a clear zone recovery area beside the travel lane for the benefit of out-of-control vehicles. It is not economical or practical to carry these full clear zone widths across bridges. Standard widths for bridge shoulders have been set to balance costs and safety. Since the railing is located within the clear zone it is considered a hazard and guardrail protection is required in the approach area.

APRIL 2004 LRFD BRIDGE DESIGN 2-3

Functions of the shoulder include: Recovery area to regain control of a vehicle. Emergency parking area for stalled vehicles and escape route for

stranded motorists. Passageway for bicycles and occasional pedestrians. Passageway for emergency vehicles. Parking area for bridge maintenance and inspection vehicle (snooper). Temporary traffic lane during deck repairs or overlay construction. Area for deck drainage and snow storage. Accommodates passing of wide oversize loads, especially farm

machinery. On two-lane highways, the shoulders provide an escape area to avoid

a head-on collision with an oncoming passing vehicle. The following shoulder widths for both rural and urban design apply to trunk highway bridges. In addition, these standards apply to bridges on local roads at a trunk highway freeway interchange. For local roads and streets, the bridge roadway widths are given in the State Aid Manual, Section 5-892.210 and the State Aid Operations Rules, Chapter 8820. Exceptionally long bridges or bridges with a high cost per square foot should be evaluated on an individual basis and modifications to these standards are allowed based on judgment. In addition to these values, the bridge roadway width shall meet the additional requirements for sight distance and sharp curvature as specified in Part 3 below. 1) Rural Design

a) Two-Lane Rural Design Shoulder widths are given in the table on Figure 2.1.4.1 and are dependent on the functional classification of the roadway and traffic volumes.

b) Four-Lane Rural Design i) Right Shoulder 12'-0" ii) Left Shoulder 6'-0"

c) Six- or Eight-Lane Rural Divided Highway i) Right Shoulder 12'-0" ii) Left Shoulder 12'-0"

The full inside shoulder allows disabled vehicles in the left lane to stop on the inside shoulder rather than try to cross two or three lanes of traffic to get to the outside shoulder.

d) Mainline Rural Bridge with Auxiliary Lane i) Right Shoulder 8'-0"

e) Mainline Rural Bridge with Entrance or Exit Ramps i) Right Shoulder 8'-0"

MARCH 2005 LRFD BRIDGE DESIGN 2-4

f) Rural Bridges with Turn Lanes i) Right Turn Lane

(1) Right shoulder 6'-0" ii) Left Turn Lanes

(1) Adjacent to a barrier railing: 4'-0" minimum shoulder, 6'-0" desirable.

g) Rural Ramp Bridges (one 16'-0" lane, one-way) i) Right Shoulder 6'-0" ii) Left Shoulder 4'-0"

On ramp bridges the dimension from edge of lane to gutter is reduced to prevent the appearance of a two-lane bridge on a one-lane ramp. The roadway width is 26'-0", which allows traffic to pass a stalled vehicle. With a 16'-0" lane the outside 2'-0" could, in effect, be considered as part of the shoulder for a 12'-0" lane.

2) Urban Design (Approach Curbs) For urban designs the bridge gutter lines shall be aligned with the curb line on the approaching roadway with the following exceptions: a) On four-lane divided highways where there are no median curbs,

the left shoulder shall be 6'-0". b) On six- and eight-lane divided highways where there are no

median curbs, the left shoulder shall be 10'-0" minimum. c) On one-lane urban ramps (16'-0" approach roadway), both right

and left shoulders shall be 4'-0" (provides a 24'-0" roadway). d) Where an auxiliary lane, ramp, or taper extends onto a mainline

bridge, the right shoulder shall be 6'-0". e) The minimum distance to a barrier railing is 6'-0" desired, 4'-0"

minimum. Urban shoulder widths will vary according to functional class, traffic volumes, scope of work, and quality of pavement surface. Typical values are shown in the Road Design Manual, Tables 4-4.01A, 4-4.01B, and 4-4.01C. Provide a 2'-0" reaction distance to a raised island type median or sidewalk curb where vehicle speeds are 40 mph and under. For design speeds 45 mph and higher, provide a 4'-0" reaction distance.

3) Bus Shoulders Where the right shoulder has been designated as a bus shoulder a 12'-0" width shall be provided across bridges. See Road Design Manual 4-4.03 and Table 4-4.03A.

MARCH 2005 LRFD BRIDGE DESIGN 2-5

4) Additional Width Criteria a) Where a ramp (loop) bridge is on a radius of 190'-0" or less, or

when the volume of trucks is 10% or greater, the effective traffic lane is increased from 16'-0" to 18'-0" in width to accommodate truck turning movements. Increase the width of the ramp bridge accordingly.

b) For curved bridges longer than 100 feet, check the horizontal stopping sight distance and increase the inside shoulder width up to a maximum of 10'-0". See Road Design Manual, Chapter 3 for calculation of this distance. The 2001 edition of the AASHTO book, A Policy on Geometric Design of Highways and Streets, changed the height of object from 6" (muffler) to 2'-0" (tail light). Table 2.1.2.1 gives widths required for a continuously curving bridge for various design speeds and curvature, and applies only where the line of sight is blocked by the railing.

Table 3.1.2.1 Shoulder Width Requirements for Curved Bridges

SHOULDER WIDTH FOR DEGREE OF CURVATURE LISTED DESIGN

SPEED 6 FT. 8 FT. 10 FT.

70 mph to 0o 45 > 0o 45 to 1o > 1o

60 mph to 1o 15 > 1o 15 to 2o > 2o

50 mph to 2o 30 > 2o 30 to 3o 15 > 3o 15

40 mph to 5o 30 > 5o 30 to 7o > 7o

c) For bridges on tapers, the taper should begin or end at a pier or

an abutment, or continue across the entire length of the bridge. Extra width to eliminate or simplify a taper or curvature is permissible where justified by simplified design and construction.

Cross Slopes on Bridges 1) The cross slope on bridge traffic lanes is the same as the approaching

roadway lanes, normally 0.02 ft./ft. The shoulder cross slope on the bridge may continue at 0.02 ft./ft. or, if better drainage is desired, may be 0.005 ft./ft. greater than the adjacent lane, with a maximum cross slope of 0.04 ft./ft. When the bridge deck is superelevated, the shoulders shall have the same slopes as the adjacent bridge traffic lanes. Keep superelevation transitions off bridges. In instances where they are unavoidable, it is preferable for ease of deck pouring to maintain

MARCH 2005 LRFD BRIDGE DESIGN 2-6

a straight line across the deck at all locations (allows a straight screed between paving rails placed at both sides of the deck.)

2) Ramp cross slopes shall be uniform between the bridge curbs with a slope of 0.02 ft./ft. to the right unless superelevated.

Bridge Median On divided highways with a separate bridge for each roadway, the openings between bridges must be a minimum of 8'-0" wide if access for bridge inspection vehicles (snoopers) is required. Longitudinal joints along the median of bridges should be used only for bridge roadways wider than about 100 feet or for other special cases. By eliminating this joint on bridges with medians, simpler detailing and simpler construction can be used. Bridge Sidewalks and Bikeways Bridge sidewalks of 6'-0" minimum widths are to be provided where justified by pedestrian traffic. When bicycle traffic is expected, the width should be 8'-0" minimum and 10'-0" desirable. Where an off road bikeway is to be carried across a bridge, the full width of the approach bikeway may be continued across the bridge up to a maximum width of 12'-0". Widths beyond 12'-0" are considered excessive. When the shoulders of the bikeway cannot be carried over bridges, provide lead-in guardrail. The curb height for sidewalks adjacent to the roadway is 8". When the design speed on the street is over 40 mph, a concrete barrier is required between the roadway and the sidewalk (or bikeway). In addition, a pedestrian (or bikeway) railing is required on the outside. When a barrier is provided between the traffic lanes and the sidewalk, use the bridge slab for the walkway (i.e., do not require an additional pour for sidewalk). Advise the road plans designer to provide for any necessary sidewalk ramping off the bridge. Sidewalks and bikeways shall have a minimum cross slope of 0.01 ft./ft. Protective Rails at Bridge Approaches The ends of bridge railings must be protected from being impacted (except on low speed roads such as city streets). For design speeds over 40 mph, a crash tested guardrail transition (normally plate beam guardrail) is required.

MARCH 2005 LRFD BRIDGE DESIGN 2-7

2.1.3 Bridge Undercrossing Geometrics

Refer to State-Aid Operation Rules, Chapter 8820 for guardrail requirements on local bridges. General Criteria for Lateral Clearance Bridge undercrossing geometrics must rationalize safety requirements with costs and physical controls such as span length and permissible depth of structure. The following guidelines apply in establishing these geometrics: 1) Safety

Piers, abutments, side slopes and back slopes steeper than 1:3, and guardrails can all be hazards to an out of control vehicle. It is desirable at all bridge undercrossings to provide a clear zone recovery area beside the roadway that is free from these hazards. This clear zone is given in the Road Design Manual, Section 4-6.0 and is a function of the roadway curvature, design speed, ADT, and ground slope. For the area under bridges a practical maximum clear zone of 30 feet may be used as permitted in the 2002 AASHTO Roadside Design Guide, Table 3.1 based on consistent use and satisfactory performance. Eliminate side piers from the roadside area wherever possible. The desirable bridge undercrossing will satisfy the above safety criteria. For those locations where it is totally impractical to provide a full clear zone recovery area at an undercrossing (as at some railroad underpasses and in certain urban situations), lesser side clearances are permitted. Where the full recovery areas must be infringed upon, the greatest side clearances that circumstances will permit shall be used. A side clearance of 20 feet is not as desirable as 30 feet but is still better than the absolute minimum clearance. Minimum lateral clearances are specified under the section for Lateral Clearance for Mainline Highways. Where drainage must be carried along the roadway passing under a bridge, either a culvert must be provided at the approach fill or the ditch section must be carried through at the toe of the bridge approach fill. The use of a culvert will often permit more desirable bridge geometrics, but the culvert openings can also introduce a roadside hazard. A determination regarding drainage (need for culverts, size of a culvert, and assessment of possible hazard) will be a controlling factor in deciding geometrics of the bridge for the site.

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2) Economics Prestressed concrete beam spans (in length up to about 145 feet) are normally the most economical type of construction for grade separations. In addition, there will usually be greater economy in constructing grade separations using two long spans rather than constructing four shorter spans, provided that a concrete superstructure can be used.

3) Aesthetics The use of longer spans will necessitate a deeper superstructure and higher approach fills. Consideration must be given to the effect of the depth of structure on the overall appearance and design of the undercrossing. For rough calculations during preliminary planning, the depth of highway bridge superstructures can be assumed to be about 1/20 of the length of the longest span. (Depth of superstructure refers to the dimension from top of slab to bottom of beam.) Contact the Preliminary Bridge Plans Engineer for the exact dimensions to be used in final planning. Contact the Preliminary Bridge Plans Engineer for depth of structure on railroad bridges.

Lateral Clearance for Mainline Highways 1) The desirable lateral clearance right and left from the edge of through

traffic lanes to any hazard (as described above) is the full clear zone. 30'-0" may be used as a practical maximum. Side piers shall be eliminated entirely wherever feasible.

2) The details for rural design provide for selection of geometrics that

carry the ditch section through the bridge (Alternate B), and also geometrics that have a filled ditch (Alternate A). (See Figures 2.1.4.1 and 2.1.4.3.) Alternate A permits a shorter bridge superstructure and thereby improves the economics and the chance of eliminating side piers and is used almost exclusively. However, Alternate A can only be used where ditch culverts will be deleted or used without introducing a significant safety hazard.

3) Where the roadway ditch section (rural design) is modified at the

bridge (Alternate A), a longitudinal transition from the ditch section to the 0.04 ft./ft. side slope under the bridge must be provided. Use a maximum longitudinal slope of 1:20.

4) For an auxiliary lane, the clear zone must be maintained from both

the through traffic lane and the auxiliary lane.

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5) For ramps and tapers adjacent to the mainline highway, the clear zone must be maintained from both the through lane and the taper. A reduced design speed, usually 50 mph, is assumed for the taper.

6) Minimum Lateral Clearances

The following paragraphs list those instances where less than desirable geometrics can be considered and describes the minimum values that will apply. Where geometrics less than desirable are to be used, approval of the State Bridge Engineer and State Design Engineer must be obtained. For plate beam guardrail with standard 6'-3" post spacing, a minimum of 3'-0" is required between the face of the guardrail and the face of the pier or abutment to allow room for the guardrail to deflect. (See Road Design Manual 10-7.02.01.) a) Through Traffic Lanes Right Side

For urban design, the lateral clearance on the right measured from the edge of the through lane shall be not less than 10'-0" width for an approaching shoulder plus the minimum width of approaching berm. This will result in minimum dimension of 16'-0" from the edge of a lane to face of substructure unit. For auxiliary lanes, tapers, and ramps along urban mainline highways, the minimum lateral clearance from the edge of a lane to face of pier or abutment on the right is 10'-0". This provides room to construct the standard 6'-0" ramp shoulder plus providing an additional 4'-0" of space for guardrail. However, in no event shall the distance from the edge of a through lane to the face of a pier be less than 16'-0". For rural design, the lateral clearance on the right may be reduced from the full clear zone distance at railroad overpasses. At these locations the minimum clearance on the right shall be as described above for urban designs.

b) Through Traffic Lanes Left Side of Divided Highways i) Urban Highways with Continuous Median Barriers

The minimum clearances at continuous median barriers are based on the use of a concrete barrier between the roadways. (See Std. Plate 8322.) For urban design, four-lane divided roadways, the minimum clearance on the left will be based on providing an 8'-0" wide shoulder from the edge of a through lane to median gutter line away from the bridge. The 8'-0" wide shoulder may be

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infringed upon as necessary to carry the median barrier around a bridge pier. At normal grade separations, using 3'-0" thick piers, the 8'-0" shoulder may be reduced to 6'-2" at the pier. (See Figure 2.1.4.11.) For urban design, six- and eight-lane divided roadways, the minimum clearance on the left is based on providing a 10'-0" minimum wide shoulder from the edge of a through lane to median gutter line outside of the bridge. As described above for four-lane divided roadways, this dimension may be infringed upon as necessary to carry the median barrier around a bridge pier. This may result in reducing the shoulder width from 10'-0" to 8'-2" at normal grade separations (assuming 3'-0" thick pier). (See Figure 2.1.4.11.)

ii) Urban Highways without Continuous Median Barriers The warrant requiring a median barrier is based on the median width and the ADT. (See Road Design Manual.) At those locations where the clear distance to a center pier is less than the clear zone distance from the edge of a lane, but where a continuous barrier will not be provided, a plate beam barrier will normally be required at the pier. The pier with plate beam guardrail protection can be used only in medians that are 18'-6" or wider for four-lane divided highways, and 22'-6" or wider for six- and eight-lane divided highways. (Dimensions are from the edge of lane to edge of lane.) Piers on high speed roadways should not be placed in medians narrower than 18'-6" (four- lane) or 22'-6" (six- or eight-lane). The face of the plate beam will be located 2'-0" from the face of the pier. At normal grade separations (with 3'-0" pier thickness) this will result in a dimension of 5'-6" from the edge of lane to face of the guardrail on four-lane divided roads, and a dimension of 7'-6" from the edge of lane to face of the guardrail on six- and eight-lane divided roads.

iii) Rail Overpasses Using Rural Design For rural design, the median width (edge of lane to edge of lane) for roadways passing under railroads may be considered for a reduction. Where a reduced width is used, the distance from the edge of lane to face of pier should be not less than 20'-0".

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Lateral Clearances for Ramps When rural or urban ramps pass under a bridge independently, piers should be eliminated and the approaching typical section should be carried through the bridge. On extremely skewed bridges where piers are necessary, place the face of pier 2'-0" further from roadway than toe of back slope. (See Figure 2.1.4.8.) Lateral Clearances for Local Roads Lateral clearances for local roads are dependent on ADT. The applicable values are shown on Figure 2.1.4.9. Lateral Clearance for Local Streets Locate the face of piers or abutments on or beyond the property line. This will provide for the ultimate development of the section by local authorities. A minimum distance of 6'-0" from the face of a curb to the face of pier or abutment must be provided. Lateral Clearance for Railroads Lateral clearances at railroads are to be determined as follows: 1) The statutory clearances diagram shown on Figure 2.1.4.10

represents the absolute minimums that must be adhered to. For design, a minimum horizontal clearance of 9'-0" to a pier or abutment is to be used (8'-6" legal).

2) Side piers are placed 4'-0" in from the back slope contro