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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
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DAVID S. EKERN, Commissioner, Virginia DOT, Richmond
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EX OFFICIO MEMBERS
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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
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Space Center, MS
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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
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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-
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States Department of Transportation. used to imply TRB, AASHTO, FAA, FHWA, FMSCA, FTA, or Transit
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The Transportation Research Board of the National Research or practice. It is expected that those reproducing the material in this docu-
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The National Academy of Sciences is a private, nonprofit, self-perpetuating society of distinguished schol-
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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
