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8/10/2019 NPCA Stormwater Presentation Draft

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Underground Precast Concrete Structures

Benefits, Loads and Codes

Presented by: Franklin J. Conklin PE,

Gary K. Munkelt & Associates



WELCOME

Benefits of Precast Concrete

Design, Construction & Performance

Overview of Loads & Codes for Concrete

Structural Design Highway, Railroad & Airport




-Design-

• Proven / Predictable / Available Materials

• Research Well Funded & Accepted

• Manufacturer & Component Certifications

• Mature Codes



Availability



Modular Assembly



Large Single Components



Specialty Process Component



Variable Geotech. Requirements




-Performance-• Flexible Geometry

• Conveyance or Retention/Detention

• Direct Loading or Deep Structures

• Resist Buoyancy

• Custom Finishes

• Durable / Sustainable



Large Conveyance Volumes



Long Conveyance Runs



Large Retention Assemblies



Shallow / Wide- Detention

PROJECT TOTAL - 250,000 CU FT STORAGE



Direct Loading



Deep Burial



Buoyancy Protection



Custom Finishes




-Questions-

?



CONCRETE LOADS & CODES

OVERVIEW



Bookshelf

ACI ASTM

AASHTOSTATE SPECS

AREMA

FAA



AMERICAN CONCRETE INSTITUTE ACI 318 – 11

Building Code Requirements for Structural Concrete

General Code For Concrete Construction

Code formulated with load and strength reduction factors

such that members can be proportioned for adequate

strength & serviceability

GENERAL SPECIFICATION ACI MANUAL OF CONCRETE PRACTICE



GENERAL SPECIFICATION

ACI MANUAL OF CONCRETE PRACTICE

AMERICAN CONCRETE INSTITUTE ACI 350 – 06

Code Requirements for Environmental Engineering

Concrete Structures

“…precast concrete environmental structures designed and

constructed in accordance with ASTM or AWWA are not

covered in this code.”



ASTM - WET

• C913-08 Standard Specification for Precast ConcreteWater and Wastewater Structures

• C890-13 Standard Practice for Minimum Structural

Design Loading for Monolithic or Sectional PrecastConcrete Water and Wastewater Structures

Live Loads follow/refer to AASHTO Standard Specs

Default minimum lateral loads coefficients are given

Actual coefficient depend on soil properties



ASTM - DRY• C858-10e1Standard Specification for Underground

Precast Concrete Utility Structures

• C857-13 Standard Practice for Minimum Structural

Design Loading for Underground Precast ConcreteUtility Structures

Live Loads follow/refer to AASHTO Standard Specs

Default minimum lateral loads coefficients are given

Actual coefficient depend on soil properties



ASTM – BOX CULVERT

• C1433-13b Standard Specification for Precast

Reinforced Concrete Monolithic Box Sections for

Culverts, Storm Drains, and Sewers

• C1577-13a Standard Specification for Precast

Reinforced Concrete Monolithic Box Sections for

Culverts, Storm Drains, and Sewers Designed

According to AASHTO LRFD

Be careful, some of these structures will not have Bridge Rating >1.0



ASTM – BOX CULVERT

Gives wall thickness and reinforcing for standard

single cell box culvert sections for highway & various

soil cover loading

1433 AASHTO Standard Specs HS-20 or Interstate Truck

1577 AASHTO LRFD HL-93

Be careful, these designs do not consider special state defined trucks &

some of these structures may not have Bridge Rating >1.0



HIGHWAY

AASHTO - American Association of State

Highway and Transportation Officials

Standard Specifications for Highway Bridges, 17th Edition

(Interims through 2003)

AASHTO LRFD Bridge Design Specifications, 6th Edition,

(2013 Interim)



HIGHWAY

AASHTO - American Association of State

Highway and Transportation Officials

June 28th, 2000 FHWA Memo

All new culverts, retaining walls, and other standard structures on which

States initiate preliminary engineering after October 1, 2010, shall be

designed by LRFD Specifications, with the assumption that thespecifications and software for these structures are "mature" at this

time.



HIGHWAY – Live Loads

Standard Specifications for Highway Bridges, 17th Edition


(Standard Specs.)

HS-20 Truck Loading



HIGHWAY – Live Loads

AASHTO LRFD Bridge Design Specifications, 6th Edition


(LRFD)

HL93Truck Loading



HS-20 Vs. HL-93



Standard Specs (SS) Vs.

Load & Resistance Factor Design(LRFD)

Design Load Factors – Top Slabs

Standard Specification LRFD[Table 3.22.1-A Group 1(g x b)] [Table3.4.1-1 Strength 1]

Live1.3x1.67=2.17 Max = 1.75 x 1.2 MP=2.1

Dead1.3x1.0=1.3 Max = 1.25

Vertical Earth1.3x1.0=1.3 Max = 1.35





Live Load Impact Factor

SS [Table 3.22.1-A Group 1(g x b)] LRFD [Table3.4.1-1 Strength 1]

1.3@ grade 1+0.33(1.0-0.125DE

)

1.0 > 3 ft cover 1.21 at 3 ft cover

Live Load Distribution Rate Through Soil

SS [Table 3.22.1-A Group 1(g x b)] LRFD [Table3.4.1-1 Strength 1]

1.75 to 1 1.15 to 1 or 1 to 1





Distribution Steel

Same for Standard Specs(3.24.10.2) & LRFD (9.7.3.2)

In bottom of top slab percentage of main positive moment

reinforcement = 100/S1/2

• S = span in feet

• Need not be more than 50 percent

• In top of top slab As6 = 0.002 x Ag (min T&S Steel)





Lateral Loads – Load Factors

Standard Specification LRFD[Table 3.22.1-A Group 1(g x b)] [Table3.4.1-1 Strength 1]

Live1.3x1.67=2.17 Max = 1.75

Horizontal Earth1.3x1.0=1.3 Max = 1.35





Lateral Loads – Soil structure Interaction Factor

Same for Both Standard Specs & LRFD

WE = Fe W Bc H

• Fe = 1 + 0.20(H/Bc)

• Fe shall not exceed 1.15 for installations with compacted fill along the sides

of the box section, or 1.40 for installations with un-compacted fill





Presumptive Dead Loads (EFP)

Standard Spec(6.2.1 Reinforced Concrete Boxes)Vertical Earth Pressure = 120 pcf

Horizontal Earth Pressure = 60 pcf

Add Bedding Factor (Soil / Structure Interaction) =1.15

Cant tell if this is supposed to be saturated soil

EFP =60 x 1.16 = 69 pcf





Presumptive Dead Loads (EFP)

LRFD (T 3.11.5.5.1 Active)Earth Pressure = 30 – 40 PCFDepends on soil type

Assumes free draining (water is prevented from creating

hydrostatic pressure)

EFP = 40 pcf + 62.4 (hydrostatic) = 102.4 pcf





Lateral Live Loads

Standard Spec heq = 2.0 ft

LRFD (3.11.6.4)

Δp = K γs heq

• H < 5 ft – heq = 4 ft

• H < 10 ft – heq = 3 ft

• H < 20 ft – heq = 2 ft





Distribution Width(Main Reinforcing Parallel To Traffic)

LRFD (4.6.2.10)

• E = 96 + 1.44S (for axle)

• E in inches and S in feet

Standard Specs(3.24.3.2)• E = 4 + 0.06S (for wheel)

• E in feet and S in feet





Other Considerations

LRFD Load Modifiers Ductility, Redundancy & Importance

LRFD Crack Control Criteria vs. SS Service Load Stress

Shear Calculations Different



RAILROAD

AREMA - American Railway Engineering

and Maintenance-of-Way Association

2013 Manual for Railway Engineering

Ch. 8 - Concrete Structures & Foundations



RAILROAD

Anything within 25 ft of track centerline should be designed

for railroad loads

Design follows ACI318 design method

Cooper E80 live loads, load factors & impact factors all

unique to this code



AIRPORTS

FAA – Federal Aviation Administration

Series 150 Advisory Circulars (ACs) for

Airport Projects



Current Advisory Circular

Cancelled - FAA - AC 150 5320-6D

New - FAA - AC 150 5320-6E

AC150 gives guidance for live loads

applied to structures by heavy airplanes



FAA -AC150/5320 Appendix 3DESIGN OF STRUCTURES FOR HEAVY AIRPLANES

For many structures the design is highly dependent upon the

airplane landing gear configuration. Our assessment indicates that

three basic configurations… will, if all are considered in the design

of the bridge components, provide sufficient support for any airplane

which may be forthcoming. These consist of two areas enclosingeight wheels each, or 16 wheels per airplane comprising the main

gear. Nose gears, as such, are not considered, except as they

occur in the static load. The “area” dimensions are 6 to 8 feet by 20

feet each supporting half of the airplane gross weight. Wheel prints

are uniformly spaced within their respective areas.




Direct Loading. Decks and covers subject to direct heavy airplane loadings such as

manhole covers, inlet grates, utility tunnel roofs, bridges, etc., should be designed for

the following loadings:

• Manhole covers for 100,000 lb. wheel loads with 250 psi tire pressure.

• For spans of 2 feet or less in the least direction, a uniform live load of 250 psi.

• For spans of 2 feet or greater in the least direction, the design will be based on

the number of wheels which will fit the span. Wheel loads of 50,000 to 75,000

pounds should be considered.

• Special consideration will be given to structures that will be required to support both

in-line and diagonal traffic lanes, such as diagonal taxiways or apron taxi routes. If

structures require expansion joints, load transfer may not be possible.




Actual Wheel Configurations from pavement design

documents provided to FAA by airplane Manufacturers

Consider wheel/gear load & geometry give & use ACI 318

design methods to proportion members



CONCRETE LOADS & CODES

Questions

?



Loads and Codes

Design of Underground Precast Concrete

StructuresPresented by: Franklin J. Conklin PE,

Gary K. Munkelt & Associates

npca stormwater presentation draft

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