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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 REPORT 782 Proposed Guideline for Reliability-Based Bridge Inspection Practices Glenn Washer Massoud Nasrollahi Christopher Applebury University of MissoUri Columbia, MO Robert Connor PUrdUe University West Lafayette, IN Adrian Ciolko KPff ConsUlting engineers Evanston, IL Robert Kogler raMPart, llC Arlington, VA Philip Fish fish and assoCiates, inC. Middleton, WI David Forsyth tri/aUstin Austin, TX Subscriber Categories Bridges and Other Structures TRANSPORTAT ION RESEARCH BOARD WASHINGTON, D.C. 2014 www.TRB.org 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 provides the most effective approach to the solution of 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 develops increasingly complex problems of wide interest to highway authorities. These problems are best studied through a coordinated program of cooperative research. In recognition of these needs, the highway administrators of the American Association of State Highway and Transportation Officials initiated in 1962 an objective national highway research program employing modern scientific techniques. This program is supported on a continuing basis by funds from participating member states of the Association and it receives the full cooperation and support of the Federal Highway Administration, United States Department of Transportation. The Transportation Research Board of the National Academies was requested by the Association to administer the research program because of the Boardâs recognized objectivity and understanding of modern research practices. The Board is uniquely suited for this purpose as it maintains an extensive committee structure from which authorities on any highway transportation subject may be drawn; it possesses avenues of communications and cooperation with federal, state and local governmental agencies, universities, and industry; its relationship to the National Research Council is an insurance of objectivity; it maintains a full-time research correlation staff of specialists in highway transportation matters to bring the findings of research directly to those who are in a position to use them. The program is developed on the basis of research needs identified by chief administrators of the highway and transportation departments and by committees of AASHTO. Each year, specific areas of research needs to be included in the program are proposed to the National Research Council and the Board by the American Association of State Highway and Transportation Officials. Research projects to fulfill these needs are defined by the Board, and qualified research agencies are selected from those that have submitted proposals. Administration and surveillance of research contracts are the responsibilities of the National Research Council and the Transportation Research Board. The needs for highway research are many, and the National Cooperative Highway Research Program can make significant contributions to the solution of 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 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 at: http://www.national-academies.org/trb/bookstore Printed in the United States of America NCHRP REPORT 782 Project 12-82(01) ISSN 0077-5614 ISBN 978-0-309-30791-8 Library of Congress Control Number 2014946785 Â© 2014 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, FTA, or Transit Development Corporation 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 project that is the subject of this report was a part of the National Cooperative Highway Research Program, conducted by the Transportation Research Board with the approval of the Governing Board of the National Research Council. The members of the technical panel selected to monitor this project and to review this report were chosen for their special competencies and with regard for appropriate balance. The 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 Governing Board of the National Research Council. 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 Research Council, or the program sponsors. The Transportation Research Board of the National Academies, the National Research Council, 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 is a private, nonprofit, self-perpetuating society of distinguished scholars engaged in scientific and engineering research, dedicated to the furtherance of science and technology and to their use for the general welfare. Upon the authority of the charter granted to it by the Congress in 1863, the Academy has a mandate that requires it to advise the federal government on scientific and technical matters. Dr. Ralph J. Cicerone is president of the National Academy of Sciences. The National Academy of Engineering was established in 1964, under the charter of the National Academy of Sciences, as a parallel organization of outstanding engineers. It is autonomous in its administration and in the selection of its members, sharing with the National Academy of Sciences the responsibility for advising the federal government. The National Academy of Engineering also sponsors engineering programs aimed at meeting national needs, encourages education and research, and recognizes the superior achievements of engineers. Dr. C. D. Mote, Jr., is president of the National Academy of Engineering. The Institute of Medicine was established in 1970 by the National Academy of Sciences to secure the services of eminent members of appropriate professions in the examination of policy matters pertaining to the health of the public. The Institute acts under the responsibility given to the National Academy of Sciences by its congressional charter to be an adviser to the federal government and, upon its own initiative, to identify issues of medical care, research, and education. Dr. Victor J. Dzau is president of the Institute of Medicine. The National Research Council was organized by the National Academy of Sciences in 1916 to associate the broad community of science and technology with the Academyâs purposes of furthering knowledge and advising the federal government. Functioning in accordance with general policies determined by the Academy, the Council has become the principal operating agency of both the National Academy of Sciences and the National Academy of Engineering in providing services to the government, the public, and the scientific and engineering communities. The Council is administered jointly by both Academies and the Institute of Medicine. Dr. Ralph J. Cicerone and Dr. C. D. Mote, Jr., are chair and vice chair, respectively, of the National Research Council. The Transportation Research Board is one of six major divisions of the National Research Council. The mission of the Transporta- tion Research Board is to provide leadership in transportation innovation and progress through research and information exchange, conducted within a setting that is objective, interdisciplinary, and multimodal. The Boardâs varied activities 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 individu- als interested in the development of transportation. www.TRB.org www.national-academies.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 reported herein was performed under NCHRP Project 12-82 by the Department of Civil and Environmental Engineering at the University of Missouri (MU). The University of Missouri was the Contractor for this study. Dr. Glenn Washer, Associate Professor of Civil Engineering at MU, was the Principal Investigator. Dr. Robert Connor, Associate Professor of Civil Engineering at Purdue University, was the Co-Principal Investigator. The other authors of this report are Adrian Ciolko, Group Managerâ Bridges & Infrastructure at KPFF Consulting Engineers; Robert Kogler, Principal at Rampart, LLC.; Philip Fish, Founder and Chairman at Fish and Associates, Inc.; David Forsyth, NDE Division Manager at TRI/ Austin; Christopher Applebury, Research Assistant and M.S. Candidate at MU; and Massoud Nasrollahi, Research Assistant and Ph.D. Candidate at MU. The Research Team gratefully acknowledges the helpful insights and comments provided by the project panel during the course of the research. The Research Team would also like to acknowledge the assistance provided by the Texas and Oregon Departments of Transportation during the execution of the case study portions of the research. CRP STAFF FOR NCHRP REPORT 782 Christopher W. Jenks, Director, Cooperative Research Programs Christopher Hedges, Manager, National Cooperative Highway Research Program Waseem Dekelbab, Senior Program Officer Danna Powell, Senior Program Assistant Eileen P. Delaney, Director of Publications Scott E. Hitchcock, Editor NCHRP PROJECT 12-82(01) PANEL Field of DesignâArea of Bridges Matthew Farrar, Idaho Transportation Department, Boise, ID (Chair) Laura M. Amundson, Parsons Brinckerhoff, Minneapolis, MN William R. âRandyâ Cox, American Segmental Bridge Institute, Driftwood, TX Arthur W. DâAndrea, Louisiana DOTD, Baton Rouge, LA David A. Juntunen, Michigan DOT, Lansing, MI Peter C. McCowan, New York State DOT, Albany, NY Barton J. Newton, California DOT, Sacramento, CA Andre V. Pavlov, Florida DOT, Tallahassee, FL Lance D. Savant, AECOM, Mechanicsburg, PA Thomas D. Everett, FHWA Liaison James W. Bryant, Jr., TRB Liaison
F O R E W O R D By Waseem Dekelbab Staff Officer Transportation Research Board This report presents a proposed Guideline for reliability-based bridge inspection prac- tices and provides two case studies of the application of the proposed Guideline. The Guide- line describes a methodology to develop a risk-based approach for determining the bridge inspection interval according to the requirements in the âMoving Ahead for Progress in the 21st Century Act (MAP-21)â legislation. The goal of the methodology is to improve the safety and reliability of bridges by focusing inspection efforts where most needed and optimizing the use of resources. The material in this report will be of immediate interest to bridge engineers. The National Bridge Inspection Standards (NBIS) mandate the frequency and methods used for the safety inspection of highway bridges. The inspection intervals specified in the NBIS require routine inspections to be conducted every 24 months, and that interval may be extended to 4 years for bridges that meet certain criteria and are approved by FHWA. For bridges with fracture-critical elements, hands-on inspections are required every 2 years. The specified intervals are generally not based on performance of bridge materials or designs, but rather on experience from managing almost 600,000 bridges in the National Bridge Inventory. These inspection intervals are applied to the entire bridge inventory, but they may not be appropriate for all bridges. For example, recently constructed bridges typically experience few problems during their first decade of service and those problems are typically minor. Under the present requirements, these bridges must have the same inspection frequency and intensity as a 50-year-old bridge that is reaching the end of its service life. In the case of bridges with fracture-critical elements, newer bridges with improved fabrication processes and designs that mitigate the effects of fatigue are inspected on the same interval and to the same intensity as older bridges that do not share these characteristics. A more rational approach to determining appropriate inspection practices for bridges would consider the structure type, age, condition, importance, environment, loading, prior problems, and other characteristics of the bridge. There is a growing consensus that these inspection practices should meet two goals: (1) improving the safety and reliability of bridges and (2) optimizing resources for bridge inspection. These goals can be accom- plished through the application of reliability theory. Research was performed under NCHRP Projects 12-82 and 12-82(01) by the University of Missouri to develop a proposed bridge inspection practice for consideration for adoption by AASHTO. The methodology developed is based on rational methods to ensure bridge safety, serviceability, and effective use of resources. The report includes two parts: Part IâProposed Guideline for Reliability-Based Bridge Inspection Practices and Part IIâFinal Research Report: Developing Reliability-Based Inspection Practices that documents the entire research effort.
C O N T E N T S P A R T I Proposed Guideline for Reliability-Based Bridge Inspection Practices 3 Summary 4 Definitions 6 Chapter 1 Introduction 7 1.1 Process 7 1.1.1 Scope 8 1.1.2 Purpose 8 1.2 Background 10 1.2.1 Reliability and Probability 11 1.2.2 Consequences 12 Chapter 2 Reliability Assessment of Bridge Elements 12 2.1 Definition of Failure 13 2.2 Occurrence Factors 14 2.3 Assessment of Consequences 15 2.4 The Reliability Assessment Panel 17 Chapter 3 Determination of Inspection Interval and Scope 17 3.1 Inspection Interval 18 3.1.1 Inspection Scope 19 3.1.2 Sampling 19 3.1.3 Maintenance Inspections 19 3.1.4 Initial Inspections 19 3.1.5 Start-Up Inspections 20 3.1.6 Quality Control/Quality Assurance 21 Chapter 4 Establishing an RBI Program 21 4.1 Overview of Process 21 4.2 Setting the Scope of the Analysis 23 4.3 Training Requirements 23 4.3.1 Training for RAP Members 23 4.3.2 Training of Inspectors 24 4.4 Software Development and Integration 25 References 26 Appendix A Guideline for Evaluating the Occurrence Factor 39 Appendix B Guideline for Evaluating the Consequence Factor 51 Appendix C Guideline for Determining the Inspection Interval
54 Appendix D Inspection Technologies 59 Appendix E Attribute Index and Commentary 97 Appendix F Illustrative Examples P A R T I I Final Research Report: Developing Reliability-Based Inspection Practices 131 Summary 135 Chapter 1 Background 137 Chapter 2 Research Approach 139 Chapter 3 Findings and Applications 139 3.1 Introduction 140 3.2 Overview of Methodology 141 3.3 Reliability 142 3.3.1 Reliability Theory 143 3.3.2 Failure 144 3.3.3 Damage Modes and Deterioration Mechanisms 144 3.3.4 Lifetime Performance Characteristics 146 3.4 Key Elements of RBI 146 3.4.1 The OF 150 3.4.2 CFs 151 3.4.3 Inspection Procedures in RBI 153 3.4.4 RAP 159 3.5 Data to Support RBI Analysis 159 3.5.1 Quantitative vs. Qualitative Analysis 160 3.5.2 Data Needed for Assessment 161 3.5.3 Industry Data 164 3.6 Case Studies of the Methodology 164 3.6.1 Summary Overview of RAP Meeting 164 3.6.2 RAP Meeting Attendees 164 3.6.3 Schedule and Agenda 167 3.6.4 Back-Casting Procedure 169 3.6.5 Statistical Analysis of NBI Data 170 3.6.6 Bridge Inventories in Texas and Oregon 170 3.6.7 Time-in-Condition Rating 173 3.6.8 Overview of Case Study Results 175 3.6.9 CFs 176 3.7 Back-Casting Results for Oregon 176 3.7.1 Environments 176 3.7.2 CFs 177 3.7.3 Back-Casting Results for Oregon 182 3.8 Back-Casting Results for Texas 183 3.8.1 Environments 183 3.8.2 CFs 184 3.8.3 Back-Casting Results for Texas 188 3.9 Discussion of the Case Studies in Texas and Oregon 188 3.9.1 Back-Casting Results
189 Chapter 4 Conclusions, Recommendations, and Suggested Research 189 4.1 Recommendations 190 4.2 Suggested Research 190 4.2.1 Implementation Strategy 195 References 197 Abbreviations 198 Appendix A Developing Reliability-Based Inspection Practices: Oregon Pre-Stressed Bridges 204 Appendix B Texas Steel Bridge Attributes Summary 210 Appendix C Controlling Damage Modes for Sample Bridges Note: Many of the photographs, figures, and tables in this report 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.