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2017 N A T I O N A L C O O P E R A T I V E H I G H W A Y R E S E A R C H P R O G R A M NCHRP RESEARCH REPORT 851 Proposed AASHTO LRFD Bridge Design Specifications for Light Rail Transit Loads Yail Jimmy Kim Department of Civil engineering University of Colorado Denver Denver, CO Subscriber Categories Bridges and Other Structures Research sponsored by the American Association of State Highway and Transportation Officials in cooperation with the Federal Highway Administration
NATIONAL COOPERATIVE HIGHWAY RESEARCH PROGRAM Systematic, well-designed research is the most effective way to solve many problems facing highway administrators and engineers. Often, highway problems are of local interest and can best be studied by highway departments individually or in cooperation with their state universities and others. However, the accelerating growth of highway transportation results in increasingly complex problems of wide inter- est to highway authorities. These problems are best studied through a coordinated program of cooperative research. Recognizing this need, the leadership of the American Association of State Highway and Transportation Officials (AASHTO) in 1962 ini- tiated an objective national highway research program using modern scientific techniquesâthe National Cooperative Highway Research Program (NCHRP). NCHRP is supported on a continuing basis by funds from participating member states of AASHTO and receives the full cooperation and support of the Federal Highway Administration, United States Department of Transportation. The Transportation Research Board (TRB) of the National Academies of Sciences, Engineering, and Medicine was requested by AASHTO to administer the research program because of TRBâs recognized objectivity and understanding of modern research practices. TRB is uniquely suited for this purpose for many reasons: TRB maintains an extensive com- mittee structure from which authorities on any highway transportation subject may be drawn; TRB possesses avenues of communications and cooperation with federal, state, and local governmental agencies, univer- sities, and industry; TRBâs relationship to the National Academies is an insurance of objectivity; and TRB maintains a full-time staff of special- ists in highway transportation matters to bring the findings of research directly to those in a position to use them. The program is developed on the basis of research needs identified by chief administrators and other staff of the highway and transporta- tion departments and by committees of AASHTO. Topics of the highest merit are selected by the AASHTO Standing Committee on Research (SCOR), and each year SCORâs recommendations are proposed to the AASHTO Board of Directors and the National Academies. Research projects to address these topics are defined by NCHRP, and qualified research agencies are selected from submitted proposals. Administra- tion and surveillance of research contracts are the responsibilities of the National Academies and TRB. The needs for highway research are many, and NCHRP can make significant contributions to solving highway transportation problems of mutual concern to many responsible groups. The program, however, is intended to complement, rather than to substitute for or duplicate, other highway research programs. Published research reports of the NATIONAL COOPERATIVE HIGHWAY RESEARCH PROGRAM are available from Transportation Research Board Business Office 500 Fifth Street, NW Washington, DC 20001 and can be ordered through the Internet by going to http://www.national-academies.org and then searching for TRB Printed in the United States of America NCHRP RESEARCH REPORT 851 Project 12-92 ISSN 2572-3766 (Print) ISSN 2572-3774 (Online) ISBN 978-0-309-44645-7 Library of Congress Control Number 2017944785 Â© 2017 National Academy of Sciences. All rights reserved. COPYRIGHT INFORMATION Authors herein are responsible for the authenticity of their materials and for obtaining written permissions from publishers or persons who own the copyright to any previously published or copyrighted material used herein. Cooperative Research Programs (CRP) grants permission to reproduce material in this publication for classroom and not-for-profit purposes. Permission is given with the understanding that none of the material will be used to imply TRB, AASHTO, FAA, FHWA, FMCSA, FRA, FTA, Office of the Assistant Secretary for Research and Technology, PHMSA, or TDC endorsement of a particular product, method, or practice. It is expected that those reproducing the material in this document for educational and not-for-profit uses will give appropriate acknowledgment of the source of any reprinted or reproduced material. For other uses of the material, request permission from CRP. NOTICE The research report was reviewed by the technical panel and accepted for publication according to procedures established and overseen by the Transportation Research Board and approved by the National Academies of Sciences, Engineering, and Medicine. The opinions and conclusions expressed or implied in this report are those of the researchers who performed the research and are not necessarily those of the Transportation Research Board; the National Academies of Sciences, Engineering, and Medicine; or the program sponsors. The Transportation Research Board; the National Academies of Sciences, Engineering, and Medicine; and the sponsors of the National Cooperative Highway Research Program do not endorse products or manufacturers. Trade or manufacturersâ names appear herein solely because they are considered essential to the object of the report.
The National Academy of Sciences was established in 1863 by an Act of Congress, signed by President Lincoln, as a private, non- governmental institution to advise the nation on issues related to science and technology. Members are elected by their peers for outstanding contributions to research. Dr. Marcia McNutt is president. The National Academy of Engineering was established in 1964 under the charter of the National Academy of Sciences to bring the practices of engineering to advising the nation. Members are elected by their peers for extraordinary contributions to engineering. Dr. C. D. Mote, Jr., is president. The National Academy of Medicine (formerly the Institute of Medicine) was established in 1970 under the charter of the National Academy of Sciences to advise the nation on medical and health issues. Members are elected by their peers for distinguished contributions to medicine and health. Dr. Victor J. Dzau is president. The three Academies work together as the National Academies of Sciences, Engineering, and Medicine to provide independent, objective analysis and advice to the nation and conduct other activities to solve complex problems and inform public policy decisions. The National Academies also encourage education and research, recognize outstanding contributions to knowledge, and increase public understanding in matters of science, engineering, and medicine. Learn more about the National Academies of Sciences, Engineering, and Medicine at www.national-academies.org. The Transportation Research Board is one of seven major programs of the National Academies of Sciences, Engineering, and Medicine. The mission of the Transportation Research Board is to increase the benefits that transportation contributes to society by providing leadership in transportation innovation and progress through research and information exchange, conducted within a setting that is objective, interdisciplinary, and multimodal. The Boardâs varied committees, task forces, and panels annually engage about 7,000 engineers, scientists, and other transportation researchers and practitioners from the public and private sectors and academia, all of whom contribute their expertise in the public interest. The program is supported by state transportation departments, federal agencies including the component administrations of the U.S. Department of Transportation, and other organizations and individuals interested in the development of transportation. Learn more about the Transportation Research Board at www.TRB.org.
C O O P E R A T I V E R E S E A R C H P R O G R A M S AuTHOR ACkNOWLEDGMENTS The research team gratefully acknowledges all individuals who participated in this project, particu- larly the graduate research assistants, consulting members (Dr. Daniel Tobias, Dr. Trever Wang, and Mr. Ken Fleck), and the panel of NCHRP Project 12-92. The Regional Transportation District (RTD) in Denver, Colorado, has offered significant assistance for the field monitoring of constructed light rail bridges. The AASHTO Subcommittee T-5 (Loads and Load Distribution) provided technical insights when developing design specifications. The support from AASHTO is appreciated. CRP STAFF FOR NCHRP RESEARCH REPORT 851 Christopher J. Hedges, Director, Cooperative Research Programs Lori L. Sundstrom, Deputy Director, Cooperative Research Programs Waseem Dekelbab, Senior Program Officer Gary A. Jenkins, Senior Program Assistant Eileen P. Delaney, Director of Publications Margaret B. Hagood, Editor NCHRP PROjECT 12-92 PANEL Field of DesignâArea of Bridges William M. âBillâ DuVall, Georgia DOT, Atlanta, GA (Chair) Xiaohua Hannah Cheng, New Jersey DOT, Trenton, NJ Siamak Khajehpour, Veresk, Inc., Toronto, ON Andy Ko, STV Incorporated, New York, NY Hani H. Nassif, Rutgers, The State University of New Jersey, Piscataway, NJ Duane Otter, Transportation Technology Center, Inc., Pueblo, CO Johnathan A. Terrazas, Lockwood, Andrews & Newnam, Inc., Austin, TX Wagdy G. Wassef, AECOM, Mechanicsburg, PA Berhanu Woldemichael, Alabama DOT, Montgomery, AL Lloyd M. Wolf, Walter P. Moore, Austin, TX Brian Michael Kozy, FHWA Liaison Stephen F. Maher, TRB Liaison
This report provides proposed AASHTO LRFD Bridge Design Specifications for bridges carry- ing light rail transit loading, including those subjected to both light rail and highway traffic load- ings. The proposed specifications and design examples are based on comprehensive response monitoring of five bridges carrying light rail transit vehicles in Denver, Colorado, and analytical programs for investigating the behavior of light rail bridges, live loads and associated forces, railâtrainâstructure interaction, and load factor calibration to implement the Load and Resis- tance Factor Design (LRFD) method. A standard live load model was developed to generate uniform design outcomes, regardless of transit agency. Load factors are calibrated, particularly for the strength and fatigue limit states of light rail bridges. The material in this report will be of immediate interest to bridge engineers. Bridges carrying or anticipated to carry railâtransit vehicles have become more common- place in crowded metropolitan areas as an alternative to relieve traffic congestion and provide additional transportation choices. In many cases, bridges are designed to carry the railâtransit vehicles only, but there are instances where rail transit is designed to occupy a dedicated lane or perhaps mix with regular highway traffic. While there is a wide spectrum of railway systems, light rail transit is distinct from heavy rail (i.e., metro rail systems, commuter rail, and railroad freight systems). Heavy rail entirely operates in exclusive rights-of-way while light rail transit can operate in shared rights-of-way (i.e., mixed with traffic). The American Public Transportation Association (APTA) defines light rail transit as an electric railway system characterized by its ability to operate single or multiple car consists (trains) along exclusive rights-of-way at ground level, on aerial structures, in subways or in streets, able to board and discharge passengers at station platforms or at street, track, or car-floor level and normally powered by overhead electrical wires. For bridges designed for light rail transit systems, the responsible agency often requires that such bridges be designed to satisfy owner-specific and local design codes, various AASHTO bridge specifications, and the Manual for Railway Engineering (MRE) by the American Rail- way Engineering and Maintenance of Way Association (AREMA). However, neither AASHTO bridge specifications nor the AREMA manual specifies the light rail transit loads. In addition, designing bridges for light rail transit systems involves a number of additional conditions that affect bridge design and may not be familiar to highway bridge engineers such as the details of the trackwork design and the interaction between the rails and structure. State DOTs have an immediate need for commonly accepted design procedures for bridges carrying light rail transit systems. Research was performed under NCHRP Project 12-92 by University of Colorado Den- ver to develop proposed AASHTO LRFD Bridge Design Specifications for bridges carrying F O R E W O R D By Waseem Dekelbab Staff Officer Transportation Research Board
only light rail transit vehicles and bridges carrying both light rail transit vehicles and regular highway traffic. The proposed specifications specify transit load characteristics (e.g., loads and forces, load distribution, load frequency, dynamic allowance, and dimen- sional requirements), load factors and combinations, analysis requirements, and detailing requirements. The proposed AASHTO LRFD Bridge Design Specifications for bridges carrying only light rail transit vehicles and bridges carrying both light rail transit vehicles and regular highway traffic will be published by AASHTO if the AASHTO Subcommittee on Bridges and Structures approves them. The Design Examples are available on the TRB project website.
1 Summary 2 Chapter 1 Introduction 2 1.1 Background 4 1.2 Research Objectives 5 1.3 Research Approach 5 1.4 Organization of the Report 6 Chapter 2 State of the Art Review 6 2.1 Light Rail Trains, Tracks, and Decks 7 2.2 Use of a Mixed Load Configuration for Bridges or Functional Changes 7 2.3 In Situ Response of Bridges Subjected to Rail Load 9 2.4 Live Load and Associated Effects 12 2.5 Train-Structure Interaction 18 2.6 Load and Resistance Factors for Rail Transit 19 2.7 Summary and Challenges 21 Chapter 3 Research Program 21 3.1 Response Monitoring of Constructed Bridges 26 3.2 Finite Element Modeling 31 3.3 Development of a Standard Live Load Model for Light Rail Transit 40 3.4 Characterization of Live Load Effects 44 3.5 RailâTrainâStructure Interaction and Associated Forces 50 3.6 A Unified Approach for Designing Bridges Carrying Light Rail and Highway Traffic Loads 52 3.7 Proposal of Load Factors 55 3.8 Chapter 3 Tables 78 3.9 Chapter 3 Figures 191 Chapter 4 LRFD Guide Specifications for Bridges Carrying Light Rail Transit Loads 191 4.1 General 191 4.2 Design Philosophy 191 4.3 Loads 191 4.4 Structural Analysis 192 4.5 Design Examples 193 Chapter 5 Summary and Conclusions 193 State of the Art Review 194 Research Program 195 References C O N T E N T S Note: Photographs, figures, and tables in this report may have been converted from color to grayscale for printing. The electronic version of the report (posted on the web at www.trb.org) retains the color versions.