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Suggested Citation:"Front Matter." National Academies of Sciences, Engineering, and Medicine. 2018. Fracture-Critical System Analysis for Steel Bridges. Washington, DC: The National Academies Press. doi: 10.17226/25230.
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Suggested Citation:"Front Matter." National Academies of Sciences, Engineering, and Medicine. 2018. Fracture-Critical System Analysis for Steel Bridges. Washington, DC: The National Academies Press. doi: 10.17226/25230.
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Suggested Citation:"Front Matter." National Academies of Sciences, Engineering, and Medicine. 2018. Fracture-Critical System Analysis for Steel Bridges. Washington, DC: The National Academies Press. doi: 10.17226/25230.
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Suggested Citation:"Front Matter." National Academies of Sciences, Engineering, and Medicine. 2018. Fracture-Critical System Analysis for Steel Bridges. Washington, DC: The National Academies Press. doi: 10.17226/25230.
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Suggested Citation:"Front Matter." National Academies of Sciences, Engineering, and Medicine. 2018. Fracture-Critical System Analysis for Steel Bridges. Washington, DC: The National Academies Press. doi: 10.17226/25230.
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Suggested Citation:"Front Matter." National Academies of Sciences, Engineering, and Medicine. 2018. Fracture-Critical System Analysis for Steel Bridges. Washington, DC: The National Academies Press. doi: 10.17226/25230.
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Suggested Citation:"Front Matter." National Academies of Sciences, Engineering, and Medicine. 2018. Fracture-Critical System Analysis for Steel Bridges. Washington, DC: The National Academies Press. doi: 10.17226/25230.
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Suggested Citation:"Front Matter." National Academies of Sciences, Engineering, and Medicine. 2018. Fracture-Critical System Analysis for Steel Bridges. Washington, DC: The National Academies Press. doi: 10.17226/25230.
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2018 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 883 Fracture-Critical System Analysis for Steel Bridges Robert J. Connor Francisco J. Bonachera Martín Amit Varma Zhichao Lai Cem Korkmaz Purdue university West Lafayette, IN Subscriber Category Bridges 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 techniques—the 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 TRB’s 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; TRB’s 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 transportation departments, by committees of AASHTO, and by the Federal Highway Administration. Topics of the highest merit are selected by the AASHTO Special Committee on Research and Innovation (R&I), and each year R&I’s recommendations are proposed to the AASHTO Board of Direc- tors and the National Academies. Research projects to address these topics are defined by NCHRP, and qualified research agencies are selected from submitted proposals. Administration 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 883 Project 12-87A ISSN 2572-3766 (Print) ISSN 2572-3774 (Online) ISBN 978-0-309-39054-5 Library of Congress Control Number 2018950182 © 2018 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 manufacturers’ 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 Board’s 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 documented in this report was performed under NCHRP 12-87A by the Lyles School of Civil and Environmental Engineering at Purdue University in West Lafayette, Indiana. Purdue University is the prime contractor for this study with Robert J. Connor, professor of Civil Engineering at the Lyles School of Civil Engineering, as the project director and principal investigator. The co-principal investiga- tor of this report is Amit Varma, also professor of Civil Engineering at the Lyles School of Civil Engineer- ing. The other authors of this report are research engineers Francisco J. Bonachera Martín and Zhichao Lai; and PhD candidate Cem Korkmaz, at the Robert L. and Terry L. Bowen Laboratory for Large-Scale Civil Engineering Research at Purdue University. The authors also acknowledge the guidance and input from the project panel. CRP STAFF FOR NCHRP RESEARCH REPORT 883 Christopher J. Hedges, Director, Cooperative Research Programs Lori L. Sundstrom, Deputy Director, Cooperative Research Programs Waseem Dekelbab, Senior Program Officer Megan Chamberlain, Senior Program Assistant Eileen P. Delaney, Director of Publications Natalie Barnes, Associate Director of Publications NCHRP PROJECT 12-87A PANEL Field of Design—Area of Bridges Hussam Z. “Sam” Fallaha, Florida DOT, Tallahassee, FL (Chair) Xiaohua Hannah Cheng, New Jersey DOT, Trenton, NJ Lian Duan, California DOT, Sacramento, CA Christopher Hahin, Illinois DOT, Springfield, IL Carlos Gustavo Matos, Jacobs Engineering Group, Saint Louis, MO Gregory R. Perfetti, North Carolina DOT, Raleigh, NC Hormoz Seradj, Salem, OR Justin M. Ocel, FHWA Liaison Stephen F. Maher, P.E., TRB Liaison

F O R E W O R D By Waseem Dekelbab Staff Officer Transportation Research Board NCHRP Research Report 883 presents a proposed AASHTO guide specification for the analysis and identification of fracture-critical members and system-redundant members. The report describes the analysis methodology and provides application examples. The analysis methodology is based on comprehensive 3-D finite element analyses (FEA) and case studies to evaluate the redundancy of new and existing steel bridges with mem- bers traditionally designated as fracture-critical members (FCMs) including simple- and continuous-span I-girder and tub-girder, through-girder, truss, and tied-arch steel bridges. The material in this report will be of immediate interest to steel bridge engineers. Advances in new materials analytical tools have brought about renewed discussion of the traditional definition of what constitutes a fracture-critical (FC) steel bridge. For example, modern steel bridges are often built of high-performance steel and fabricated using higher quality welding procedures with a composite deck slab and, therefore, are inherently more capable of carrying redistributed loads through alternate paths. Cur- rently, the stringent fabrication and in-service inspection requirements for FC bridges steer owners and designers away from building new FC bridges although they are allowed by the AASHTO bridge specifications with the appropriate design, construction, and inspection procedures. The increased maintenance inspection costs are also a concern of existing FC bridges. These additional costs, and any structural concerns, could be elimi- nated or minimized by re-examining the FC designation and reclassifying bridges where justified by evaluating the consequence should a member be assumed to fail rather than by simply considering the number of girders, for example. At present, designers and owners often have different opinions on the definition of an FC bridge. The AASHTO bridge specifications do not give guidance on the appropriate level of analysis needed, load combinations, or failure criteria for establishing if a member is or is not fracture critical. Although individual designers have developed methods to address this issue, there is no consensus on the loadings and the approach to be used and what constitutes failure. Under NCHRP Project 12-87A, Purdue University was asked to (1) develop a methodol- ogy to quantify when a steel bridge system is considered FC based on loads, existing condi- tions, material properties, and bridge configurations; and (2) propose a new standalone AASHTO guide specification for the evaluation of existing and design of new steel bridges with FCMs.

A number of deliverables, provided as appendices, are not published but are available on the TRB website at https://apps.trb.org/cmsfeed/TRBNetProjectDisplay.asp?ProjectID=3808. The appendices include the following: • Appendix A: Shear Stud Modeling Study and Recommendations • Appendix B: Summaries of Analyses of Case-Study Bridges • Appendix C: Eligibility Screening Criteria for System Analysis • Appendix D: FEA Requirements for System Analysis • Appendix E: Proposed Guide Specification • Appendix F: Proposed Guide Specification Application Examples

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. 1 Summary 4 Chapter 1 Background 4 1.1 Problem Statement and Research Objective 5 1.2 Scope of Study 6 Chapter 2 Research Approach 6 2.1 Summary of the State of the Practice 10 2.2 Research Methodology 13 Chapter 3 Findings and Application 13 3.1 Finite Element Analysis Procedures, Techniques, and Inputs 30 3.2 Proposed Load Model 38 3.3 Minimum Performance Requirements in the Faulted State 43 3.4 Dynamic Load Amplification Requirements 43 3.5 Detailing for New Bridges 44 3.6 Limitations of Finite Element Analysis Methodology 45 3.7 Application of Research to Bridge Engineering Practice 46 Chapter 4 Conclusions and Suggested Research 46 4.1 Conclusions 46 4.2 Suggested Research 48 References 50 Appendices A–F

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TRB's National Cooperative Highway Research Program (NCHRP) Research Report 883: Fracture-Critical System Analysis for Steel Bridges presents a proposed specification for the analysis and identification of fracture-critical members and system-redundant members. The report describes the analysis methodology and provides application examples. The analysis methodology is based on comprehensive 3-D finite element analyses (FEA) and case studies to evaluate the redundancy of new and existing steel bridges with members traditionally designated as fracture-critical members (FCMs), including simple- and continuous-span I-girder and tub-girder, through-girder, truss, and tied-arch steel bridges.

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