NCHRP 12-92 Proposed LRFD Bridge Design Specifications …sp.bridges.transportation.org/Documents/2016...• To characterize light rail transit load effects on the behavior of bridge

NCHRP 12-92

Proposed LRFD Bridge Design Specifications for Light Rail Transit LoadsYail Jimmy Kim, Ph.D., P.Eng. FACI

Chengyu Li, Ph.D, PE, SEAssociate Professor, Department of Civil Engineering

University of Colorado DenverSenior Group Manager, Structures Group

Atkins North America

Contents

1. Introduction (Overview of Research)

2. Phase III (Guide Specifications)

3. Phases III (Design Examples)

4. Summary

5. Acknowledgments

Introduction

II IVIIIII V

Introduction

The objectives of NCHRP 12-92 are:

• To characterize light rail transit load effects on the behavior of bridge superstructure (e.g., standard train load, dynamic load allowance, load distribution, and design factors for LRFD)

• To examine the interaction between the light rail load and supporting structures, which can generate various forces to consider in design and practice

• To propose guide specifications about bridges carrying light rail loading and light rail/highway traffic loadings, including design examples for practitioners

Introduction

Overview of Research

Phase I(Planning)

• Literature review (155 papers)• Research methodologies• Outline of specifications• Interim report 1

Phase II(Implementation)

• Site work and FE modeling• Standard light rail load model• Load effects and forces/load factors• Interim report 2

Phase III(Specifications)

• Guide specifications proposed• Design examples• Interim report 3

Phase IV(Final product)

• Update of specifications• Ballot items• Final report

Completed Completed

6 months(3-month review)

Completed

Introduction

Research TasksTask 1: A critical literature reviewTask 2: A methodology specifying the light rail transit load characteristics Task 3: A detailed outline with annotated description for the developed

specificationsTask 4: Preparation of interim report No. 1Task 5: Execution of the approved work to develop the proposed

methodologyTask 6: Preparation of interim report No. 2Task 7: Development of proposed AASHTO LRFD design specifications

and commentaryTask 8: Development of design examplesTask 9: Preparation of interim report No. 3 (we are here now)Task 10: Update of proposed development to the AASHTO LRFD

SpecificationsTask 11: Preparation of a final report

Phase II (Task 5)

Overview of Technical Subtasks of NCHRP 12-92

Response monitoring of constructed bridges

Finite element modeling and field verification

Development of a standard light rail live load model

Characterization of live load effects

Rail-train-structure interaction and associated forces

A unified approach for bridges carrying light rail or/and highway

traffic loads

Proposal of load factors

Field Testing

Strain gage calibration to measure train loadEmpty train (laboratory)

Empty train (site)

Five light rail bridges in Denver

Broadway Bridge

Wheel load distribution

Typical girder strain

Finite Element Modeling

Validation of Modeling Approach (5 bridges in Denver, CO)

Indiana Bridge

Two articulated trains on Indiana Bridge

Dynamic response

Live load distribution

Finite Element Modeling

Design of Benchmark Bridges4.719.254.71 9.254.71 4.71 4.714.71 9.25

32

9.254.71 4.71

6 4 44 4 4 4 632 32 32

4 6 6 6 6 4 4 8 8 8 6 10 10 6Steel plate girder

4 6 6 66 4

4.71 9.25 4.71

4 4

9.254.71 4.71

32

6

4.714.71 9.25

8 8 8 10 10 6

3232

Steel box girder

4.719.254.71 4.719.254.71 4.71 4.71 9.25 9.254.71 4.71

644444632

6101068884466664 4

32 32 32

PC I girder

4

32

84 88

4.714.71 9.25

32

6 1010 6

4.719.254.71

32

4 4

4.714.71 9.25

12 12

PC box girder

4.714.71 9.25 4.719.254.71 4.71 9.254.71 9.254.71 4.71

6 4 4 4 4 4 632

4 6 6 6 6 4 4 8 8 8 6 10 10 632 32 32

4

RC girder girder

Phase III (Guide Specifications)

I IVIIIII VII

Phase III

Phase III: Specifications

• Objectives of Phase III are:

• To propose guide specifications that complement AASHTO LRFD BDS (Art. 3.6.1.5: ‘Where a bridge also carries rail-transit vehicles, the owner shall specify the transit load characteristics and the expected interaction between transit and highway traffic’)

• To develop design examples using the specifications

• To submit Interim Report No. 3

Phase III (Task 7)

Task 7: Development of proposed AASHTO LRFD designspecifications and commentary

• Proposed contents

1. General2. Design Philosophy3. Loads4. Structural Analysis5. References

Phase III (Task 7)


1. General• ScopeThese guide specifications (LRT Guide Specifications) are asupplement to the AASHTO LRFD Bridge Design Specifications(AASHTO LRFD BDS) that address the design of bridges subjectedto light rail transit (LRT) loadings or LRT and conventional highwaytraffic loadings.

• Notations: AASHTO LRFD BDS

• Definitions: AASHTO LRFD BDS

Phase III (Task 7)


2. Design Philosophy• General (in conformance with Art. 2.5 of BDS)

• Limit States • Service I, II, III, and IV (2016 interim used)• Strength I, III, IV, and V (2016 interim used)• Extreme Event I and II• Fatigue I and II

Phase III (Task 7)


2. Design Philosophy• Load factors and combinations (light rail only; light rail/highway)

Phase III (Task 7)


2. Design Philosophy• User comfort criteria

• Bridge deflection: deflection vs frequency (CHBDC)• Pedestrian and passenger comfort (UIC- Int. Union of Railways)

UIC Code 776-2 (Art. 5.2)

CHBDC (Art. 3.4.4)

Phase III (Task 7)


3. Loads• Permanent loads (DC, DW, and EV based on BDS)• Earth loads (EH, ES, and DD based on BDS)• Live loads (LL and PL)

• Number of design tracks• Multiple presence of live load• Design light rail transit load (LRT-16):

LRT-16

• 48,256 models• 4 probability levels• 660 load enveloping cases with 33 trains operated in the nation

30 ft to 160 ft (initial)HL-93 up to 150 ft30 ft to 300 ft (T-5)

Phase III (Task 7)


3. Loads• Dynamic load allowance (IM): 30% (25% plus 5% margin)• Derailment load (DE): 100% vertical and 40% horizontal• Centrifugal force (CE):

• Braking force (BR)28 percent of the axle weights of light rail design train or5 percent of the axle weights plus lane load

• Wind loads: WS (on structure) and WL (on trains)• Earthquake effects (EQ): Art. 3.10 of BDS

( )4.12.034 2

+−= ngRvC

Phase III (Task 7)


4. Structural Analysis• Acceptable method of structural analysis (Arts. 4.4/4.5 of BDS)• Structural material behavior (Arts. 4.5.2.2/4.5.2.3 of BDS)• Modeling geometry and boundary conditions (Art. 4.5.3 of BDS)• Influence of plan geometry (Art. 4.6.1 of BDS) • Distribution factor method for moment and shear

• PC box, PC I, Steel box, Steel plate, and RC

• Skewed bridges

Phase III (Design Examples)

I IVIIIII VIII

Phase III (Task 8)

Task 8: Development of design examples: Dr. Tobias/Dr. Wang

1. Simple span composite steel plate girder

Phase III (Task 8)

2. Continuous span composite steel plate girder


Phase III (Task 8)

3. Simple span composite prestressed concrete girder


Summary

I IVIIIII VIII

Summary

• Tasks 7-9 were completed

• Task 7: guide specifications were proposed in conjunction with BDS to meet the objectives of NCHRP 12-92

• Task 8: comprehensive design examples were developed based on the guide specifications and BDS

• Task 9: Interim Report No. 3 was submitted

• Tasks 10-11 will be completed by Feb. 2017 (6 mths after approval)

• Task 10: Update of proposed guide specifications• Task 11: Preparation of a final report

Phase III (Specifications)

Acknowledgments

• AASHTO

• Transportation Research Board (TRB) and NAS

• Dr. Waseem Dekelbab

• NCHRP 12-92 Panel Members

• AASHTO Sub T-5 (S. Hida and J. Robert)

• Regional Transportation District (RTD) in Denver, CO

• RT Members (Consultants: Dr. Tobias and Dr. Wang)

• Graduate Students Participating in NCHRP 12-92

- Thank-you to: I IVIIIII VV