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NCHRP National cooperative Highway Research Program Synthesis 381 Falling Weight Deflectometer Usage A Synthesis of Highway Practice

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TRANSPORTATION RESEARCH BOARD 2008 EXECUTIVE COMMITTEE* OFFICERS Chair: Debra L. Miller, Secretary, Kansas DOT, Topeka Vice Chair: Adib K. Kanafani, Cahill Professor of Civil Engineering, University of California, Berkeley Executive Director: Robert E. Skinner, Jr., Transportation Research Board MEMBERS J. BARRY BARKER, Executive Director, Transit Authority of River City, Louisville, KY ALLEN D. BIEHLER, Secretary, Pennsylvania DOT, Harrisburg JOHN D. BOWE, President, Americas Region, APL Limited, Oakland, CA LARRY L. BROWN, SR., Executive Director, Mississippi DOT, Jackson DEBORAH H. BUTLER, Executive Vice President, Planning, and CIO, Norfolk Southern Corporation, Norfolk, VA WILLIAM A.V. CLARK, Professor, Department of Geography, University of California, Los Angeles DAVID S. EKERN, Commissioner, Virginia DOT, Richmond NICHOLAS J. GARBER, Henry L. Kinnier Professor, Department of Civil Engineering, University of Virginia, Charlottesville JEFFREY W. HAMIEL, Executive Director, Metropolitan Airports Commission, Minneapolis, MN EDWARD A. (NED) HELME, President, Center for Clean Air Policy, Washington, DC WILL KEMPTON, Director, California DOT, Sacramento SUSAN MARTINOVICH, Director, Nevada DOT, Carson City MICHAEL D. MEYER, Professor, School of Civil and Environmental Engineering, Georgia Institute of Technology, Atlanta MICHAEL R. MORRIS, Director of Transportation, North Central Texas Council of Governments, Arlington NEIL J. PEDERSEN, Administrator, Maryland State Highway Administration, Baltimore PETE K. RAHN, Director, Missouri DOT, Jefferson City SANDRA ROSENBLOOM, Professor of Planning, University of Arizona, Tucson TRACY L. ROSSER, Vice President, Corporate Traffic, Wal-Mart Stores, Inc., Bentonville, AR ROSA CLAUSELL ROUNTREE, Executive Director, Georgia State Road and Tollway Authority, Atlanta HENRY G. (GERRY) SCHWARTZ, JR., Chairman (retired), Jacobs/Sverdrup Civil, Inc., St. Louis, MO C. MICHAEL WALTON, Ernest H. Cockrell Centennial Chair in Engineering, University of Texas, Austin LINDA S. WATSON, CEO, LYNXCentral Florida Regional Transportation Authority, Orlando STEVE WILLIAMS, Chairman and CEO, Maverick Transportation, Inc., Little Rock, AR EX OFFICIO MEMBERS THAD ALLEN (Adm., U.S. Coast Guard), Commandant, U.S. Coast Guard, Washington, DC JOSEPH H. BOARDMAN, Federal Railroad Administrator, U.S.DOT REBECCA M. BREWSTER, President and COO, American Transportation Research Institute, Smyrna, GA PAUL R. BRUBAKER, Research and Innovative Technology Administrator, U.S.DOT GEORGE BUGLIARELLO, Chancellor, Polytechnic University of New York, Brooklyn, and Foreign Secretary, National Academy of Engineering, Washington, DC SEAN T. CONNAUGHTON, Maritime Administrator, U.S.DOT LEROY GISHI, Chief, Division of Transportation, Bureau of Indian Affairs, U.S. Department of the Interior, Washington, DC EDWARD R. HAMBERGER, President and CEO, Association of American Railroads, Washington, DC JOHN H. HILL, Federal Motor Carrier Safety Administrator, U.S.DOT JOHN C. HORSLEY, Executive Director, American Association of State Highway and Transportation Officials, Washington, DC CARL T. JOHNSON, Pipeline and Hazardous Materials Safety Administrator, U.S.DOT J. EDWARD JOHNSON, Director, Applied Science Directorate, National Aeronautics and Space Administration, John C. Stennis Space Center, MS WILLIAM W. MILLAR, President, American Public Transportation Association, Washington, DC NICOLE R. NASON, National Highway Traffic Safety Administrator, U.S.DOT JAMES RAY, Acting Administrator, Federal Highway Administration, U.S.DOT JAMES S. SIMPSON, Federal Transit Administrator, U.S.DOT ROBERT A. STURGELL, Acting Administrator, Federal Aviation Administration, U.S.DOT ROBERT L. VAN ANTWERP (Lt. Gen., U.S. Army), Chief of Engineers and Commanding General, U.S. Army Corps of Engineers, Washington, DC *Membership as of May 2008.

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National cooperative Highway Research Program NCHRP Synthesis 381 Falling Weight Deflectometer Usage A Synthesis of Highway Practice Consultants Sirous Alavi Jeffrey F. Lecates And Michael P. Tavares Sierra Transportation Engineers, Inc. Reno, Nevada S ubject A reas Pavement Design, Management and Performance, and Materials and Construction Research Sponsored by the American Association of State Highway and Transportation Officials in Cooperation with the Federal Highway Administration Transportation Research Board Washington, D.C. 2008 www.TRB.org

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NATIONAL COOPERATIVE HIGHWAY RESEARCH PROGRAM NCHRP SYNTHESIS 381 Systematic, well-designed research provides the most effective Project 20-5 (Topic 38-15) approach to the solution of many problems facing highway ad ISSN 0547-5570 ministrators and engineers. Often, highway problems are of local ISBN 978-0-309-09810-6 Library of Congress Control No. 2008906007 interest and can best be studied by highway departments indi- vidually or in cooperation with their state universities and others. 2008 Transportation Research Board However, the accelerating growth of highway transportation devel- ops increasingly complex problems of wide interest to highway authorities. These problems are best studied through a coordinated program of cooperative research. COPYRIGHT PERMISSION In recognition of these needs, the highway administrators of the American Association of State Highway and Transportation Authors herein are responsible for the authenticity of their manuscripts Officials initiated in 1962 an objective national highway research and for obtaining written permissions from publishers or persons who own the copyright to any previously published or copyrighted material program employing modern scientific techniques. This program used herein. is supported on a continuing basis by funds from participating Cooperative Research Programs (CRP) grants permission to reproduce member states of the Association and it receives the full coopera- material in this publication for classroom and not-for-profit purposes. Per- tion and support of the Federal Highway Administration, United mission is given with the understanding that none of the material will be States Department of Transportation. used to imply TRB, AASHTO, FAA, FHWA, FMSCA, FTA, or Transit Development Corporation endorsement of a particular product, method, The Transportation Research Board of the National Research or practice. It is expected that those reproducing the material in this docu- Council was requested by the Association to administer the ment for educational and not-for-profit uses will give appropriate ac- research program because of the Board's recognized objectiv- knowledgment of the source of any development or reproduced material. ity and understanding of modern research practices. The Board For other uses of the material, request permission from CRP. is uniquely suited for this purpose as it maintains an extensive committee structure from which authorities on any highway NOTICE transportation subject may be drawn; it possesses avenues of communication and cooperation with federal, state, and local The project that is the subject of this report was a part of the National governmental agencies, universities, and industry; its relationship Cooperative Highway Research Program conducted by the Transpor- tation Research Board with the approval of the Governing Board of the to the National Research Council is an insurance of objectivity; National Research Council. Such approval reflects the Governing Board's it maintains a full-time research correlation staff of specialists in judgment that the program concerned is of national importance and appro- highway transportation matters to bring the findings of research priate with respect to both the purposes and resources of the National directly to those who are in a position to use them. Research Council. The members of the technical committee selected to monitor this proj- The program is developed on the basis of research needs iden- ect and to review this report were chosen for recognized scholarly compe- tified by chief administrators of the highway and transportation tence and with due consideration for the balance of disciplines appropri- departments and by committees of AASHTO. Each year, specific ate to the project. The opinions and conclusions expressed or implied are areas of research needs to be included in the program are proposed those of the research agency that performed the research, and, while they to the National Research Council and the Board by the Ameri- have been accepted as appropriate by the technical committee, they are not necessarily those of the Transportation Research Board, the National can Association of State Highway and Transportation Officials. Research Council, the American Association of State Highway and Transpor- Research projects to fulfill these needs are defined by the Board, tation Officials, or the Federal Highway Administration of the U.S. Depart- and qualified research agencies are selected from those that have ment of Transportation. submitted proposals. Administration and surveillance of research Each report is reviewed and accepted for publication by the techni- cal committee according to procedures established and monitored by the contracts are the responsibilities of the National Research Council Transportation Research Board Executive Committee and the Governing and the Transportation Research Board. Board of the National Research Council. 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 NOTE: The Transportation Research Board of the National Academies, Washington, DC 20001 the National Research Council, the Federal Highway Administration, the American Association of State Highway and Transportation Officials, and and can be ordered through the Internet at: the individual states participating in the National Cooperative Highway http://www.national-academies.org/trb/bookstore Research Program do not endorse products or manufacturers. Trade or manufacturers' names appear herein solely because they are considered essential to the object of this report. Printed in the United States of America

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The National Academy of Sciences is a private, nonprofit, self-perpetuating society of distinguished schol- ars engaged in scientific and engineering research, dedicated to the furtherance of science and technology and to their use for the general welfare. On 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 Acad- emy 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. Charles M. Vest 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, on its own initia- tive, to identify issues of medical care, research, and education. Dr. Harvey V. Fineberg 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 Academy's 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 Sci- ences 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. Charles M. Vest 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 Transportation Research Board is to provide leadership in transportation innovation and prog- ress through research and information exchange, conducted within a setting that is objective, interdis- ciplinary, and multimodal. The Board's 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 depart- ments, federal agencies including the component administrations of the U.S. Department of Transportation, and other organizations and individuals interested in the development of transportation. www.TRB.org www.national-academies.org

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NCHRP COMMITTEE FOR PROJECT 20-5 COOPERATIVE RESEARCH PROGRAMS STAFF CHRISTOPHER W. JENKS, Director, Cooperative Research CHAIR Programs GARY D. TAYLOR, CTE Engineers Crawford F. JENCKS, Deputy Director, Cooperative Research Programs MEMBERS EILEEN DELANEY, Director of Publications THOMAS R. BOHUSLAV, Texas DOT DWIGHT HORNE, Federal Highway Administration NCHRP SYNTHESIS STAFF YSELA LLORT, Florida DOT STEPHEN R. GODWIN, Director for Studies and Special Pro- WESLEY S.C. LUM, California DOT grams JAMES W. MARCH, Federal Highway Administration JON M. WILLIAMS, Associate Director, IDEA and Synthesis JOHN M. MASON, JR., Pennsylvania State University Studies CATHERINE NELSON, Oregon DOT GAIL STABA, Senior Program Officer LARRY VELASQUEZ, New Mexico DOT DONNA L. VLASAK, Senior Program Officer PAUL T. WELLS, New York State DOT DON TIPPMAN, Editor CHERYL KEITH, Senior Program Assistant FHWA LIAISON TOPIC PANEL WILLIAM ZACCAGNINO DAVID BULLOCK, Minnesota Department of Transportation STEVE COLSON, Maine Department of Transportation TRB LIAISON CHARLES S. HOLZSCHUHER, III, Florida Department of STEPHEN F. MAHER Transportation ROGER M. LARSON, Applied Pavement Technology, Inc. STEPHEN F. MAHER, Transportation Research Board CHARLES SCHWARTZ, University of Maryland ALBERT VASQUEZ, California Department of Transportation LESLIE ANN McCarthy, Federal Highway Administration (Liaison) ERIC WEAVER, Federal Highway Administration (Liaison)

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FOREWORD Highway administrators, engineers, and researchers often face problems for which infor- By Donna Vlasak mation already exists, either in documented form or as undocumented experience and prac- Senior Program Officer tice. This information may be fragmented, scattered, and unevaluated. As a consequence, full knowledge of what has been learned about a problem may not be brought to bear on its Transportation solution. Costly research findings may go unused, valuable experience may be overlooked, Research Board and due consideration may not be given to recommended practices for solving or alleviating the problem. There is information on nearly every subject of concern to highway administrators and engineers. Much of it derives from research or from the work of practitioners faced with problems in their day-to-day work. To provide a systematic means for assembling and evaluating such useful information and to make it available to the entire highway commu- nity, the American Association of State Highway and Transportation Officials--through the mechanism of the National Cooperative Highway Research Program--authorized the Transportation Research Board to undertake a continuing study. This study, NCHRP Project 20-5, "Synthesis of Information Related to Highway Problems," searches out and synthesizes useful knowledge from all available sources and prepares concise, documented reports on specific topics. Reports from this endeavor constitute an NCHRP report series, Synthesis of Highway Practice. This synthesis series reports on current knowledge and practice, in a compact format, without the detailed directions usually found in handbooks or design manuals. Each report in the series provides a compendium of the best knowledge available on those measures found to be the most successful in resolving specific problems. PREFACE This synthesis reports on the state of the practice of falling weight deflectometer (FWD) usage as it involves state departments of transportation (DOTs) using these devices to mea- sure pavement deflections in response to a stationary dynamic load, similar to a passing wheel load. The data obtained are used to evaluate the structural capacity of pavements for research, design, rehabilitation, and pavement management practices. It is anticipated that this synthesis will provide useful information to support guidelines, advancing the state of the practice for state DOTs and other FWD users, as well as equipment manufacturers and other involved in pavement research, design, rehabilitation, and management. Based on a survey conducted for this report, 45 state highway agencies (SHAs) reported using 82 FWDs, produced by 3 different manufacturers. The importance of FWDs among SHAs appears to be reflected in the survey results, as it was noted that SHAs conduct FWD tests on up to 24 100 lane-km (15,000 lane-miles) annually. Survey information presented in this report is supplemented by an extensive literature search, as well as communication with FWD calibration centers and FWD manufacturers. Individual SHA websites were also searched. Although current practice was limited to the United States, research published internationally was considered for historical context and for potential future research topics. A series of case studies share lessons learned from utilizing FWDs. Sirous Alavi, Sierra Transportation Engineers, Reno, Nevada, collected and synthesized the information and wrote the report. The members of the topic panel are acknowledged on the preceding page. This synthesis is an immediately useful document that records the practices that were acceptable within the limitations of the knowledge available at the time of its preparation. As progress in research and practice continues, new knowledge will be added to that now at hand.

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Contents 1 Summary 3 CHAPTER ONE Introduction Purpose, 3 Research Methodology, 4 Scope, 4 Organization of Report, 5 Definitions, 5 7chapter two Falling Weight Deflectometer Equipment Falling Weight Deflectometer Ownership, 7 Falling Weight Deflectometer Types and Configurations, 7 Falling Weight Deflectometer Manufacturers, 8 Maintenance Practices, 10 12 CHAPTER THREE Falling Weight Deflectometer Calibration Calibration Types, 12 Calibration Procedures, 12 Calibration Requirements, 13 Calibration Centers, 14 15 CHAPTER FOUR Data Collection, Management, and Storage Data Collection Guidelines, 15 Data Management, 20 Data Storage, 20 21 CHAPTER FIVE Data Analysis Data Analysis Methods, 21 Data Analysis Software, 22 Analysis Output File Types, 23 24 CHAPTER SIX Personnel Training Qualifications, 24 Training Certifications, 25 Additional Training Opportunities, 25 27 CHAPTER SEVEN Falling Weight Deflectometer Program Administration Annual Budgeting, 27 Outsourcing Requirements, 27

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29 CHAPTER EIGHT Applications of Falling Weight Deflectometer Data--Case Studies CASE 1. Data Collection and Analysis Refinement, 29 CASE 2. Pavement Rehabilitation and Overlay, 29 CASE 3. Joint Sealing Evaluation, 30 CASE 4. Pavement Management Systems, 30 CASE 5. Load Transfer Efficiency, 31 CASE 6. Void Detection, 31 CASE 7. Spring Load Restrictions, 31 CASE 8. Nonresilient Pavement Layer Behavior, 32 CASE 9. Utility Cuts, 32 CASE 10. Experimental Paving Materials, 32 CASE 11. Project Acceptance and Evaluation, 32 CASE 12. Conversion of Data From Other Nondestructive Testing Devices, 33 CASE 13. International Practices, 34 35 CHAPTER NINE Current Research In-Motion Deflection Testing, 35 Portable Falling Weight Deflectometer, 35 Ground-Penetrating Radar Integration, 36 Network-Level Testing, 36 Mechanistic-Empirical Pavement Design, 36 37 CHAPTER TEN Conclusions 39 References 43bibliography 44 Abbreviations 45 Appendix A Survey Questionnaire 68 Appendix B Summary of Survey Results Part 1: Background Information, 68 Part 2: FWD Equipment Types, 69 Part 3: FWD Equipment Maintenance, 70 Part 4: FWD Equipment Calibration, 74 Part 5: General FWD Testing Procedures, 80 Part 6: FWD Field Testing--Flexible Pavements, 84 Part 7: FWD Field Testing--Rigid Pavements, 93 Part 8: FWD Computers, 103 Part 9: Data Analysis, 105 Part 10: Data Management and Storage, 108 Part 11: Personnel Training, 110 Part 12: FWD Program Administration--Part 1 of 2, 116 Part 13: FWD Program Administration--Part 2 of 2, 118