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Report
This report is an archived publication and may contain dated technical, contact, and link information
Publication Number: FHWA-RD-03-093
Date: August 2006

Study of Long-Term Pavement Performance (LTPP): Pavement Deflections

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FOREWORD

Falling weight deflectometer (FWD) load-deflection data generally are used to characterize the tested pavement by an analysis of the applied load and the magnitudes (or shape) of the measured deflection basin. Often, these data are used to backcalculate layered elastic stiffnesses or moduli. The analysis results give the pavement researcher a measure of the pavement’s bearing capacity, which can in turn be linked to future pavement performance.

The primary objective of this study was to identify data errors or anomalies in the Long-Term Pavement Performance (LTPP) load-deflection database that were not identified during routine screening required to reach level E. Routine screening applies more general procedures, such as broad range checks, to the data. The intent of this study was to review the level E deflection data and ancillary information, looking for data discrepancies and errors that routing screening may not have identified. The overall objective of the postscreening final data check was to assure that good quality load-deflection and ancillary data are available for researchers and highway engineers.

Gary L. Henderson
Director, Office of Infrastructure
Research and Development

NOTICE

This document is disseminated under the sponsorship of the U.S. Department of Transportation in the interest of information exchange. The U.S. Government assumes no liability for the use of the information contained in this document. This report does not constitute a standard, specification, or regulation.

The U.S. Government does not endorse products or manufacturers. Trademarks or manufacturers’ names appear in this report only because they are considered essential to the objective of the document.

QUALITY ASSURANCE STATEMENT

The Federal Highway Administration (FHWA) provides high-quality information to serve Government, industry, and the public in a manner that promotes public understanding. Standards and policies are used to ensure and maximize the quality, objectivity, utility, and integrity of its information. FHWA periodically reviews quality issues and adjusts its programs and processes to ensure continuous quality improvement.

Technical Report Documentation Page

 

1. Report No.

FHWA-RD-03-093

2. Government Accession No.

3. Recipient's Catalog No.

4. Title and Subtitle

Study of Long-Term Pavement Performance (LTPP): Pavement Deflections

5. Report Date

August 2006

6. Performing Organization Code

7. Author(s)

Richard Stubstad, Erland Lukanen, and Lawrence Clevenson

8. Performing Organization Report No.

9. Performing Organization Name and Address

Consulpav International
P.O. Box 700
Oak View, CA 93022-0700

10. Work Unit No. (TRAIS)

11. Contract or Grant No.

DTFH61–01–P–00144

12. Sponsoring Agency's Name and Address

Federal Highway Administration
LTPP Division, HNR–40
Turner-Fairbank Highway Research Center
6300 Georgetown Pike
McLean, VA 22101-2296

13. Type of Report and Period Covered

Final Report
April 2001–September 2001

14. Sponsoring Agency's Code

15. Supplementary Notes

Contracting Officer’s Technical Representative—Cheryl Allen Richter, HRDI–13
This work was conducted under direct contract with the Federal Highway Administration

16. Abstract

This report presents the results of a study of pavement deflections. The study covered all level E falling weight deflectometer (FWD) deflections and associated data in LTPP’s database from Data Release 9.0, November 23, 1998. Although the limited amount of data from unbound material testing was also provided, these data were not screened due to the large variations in the recorded deflections in comparison with bound layer tests.

The report covers the screening techniques developed and used to identify data errors and anomalies in the FWD load-deflection database, along with a description of each category of data errors identified. Contrary to prior expectations, the vast majority of these data errors were related to manually input data elements, not the deflections themselves. Approximately 8 percent of the 4.4 million lines, or records, in the pre-autumn 1998 load-deflection database were affected by manual input data errors alone, while less than 0.2 percent appear to be affected by actual load-deflection data anomalies generated by the FWD. Out of the approximately 8 percent of manual input data errors found, around 7 percent were associated with nonprotocol and unreported placement of the deflection sensors along the FWD’s raise-lower bar. Other types of manual data entry errors, each occurring at a rate of less than 1 percent, included incorrect lane designation, station number, date- or time-stamp, test site, drop height, and configuration of the sensors for joint testing on portland cement concrete (PCC) pavements. Deflection reading data errors included deflection basin anomalies and sensor malfunctioning errors. A universally applicable deflection basin screening tool called SLIC was also developed for use on select FWD data file formats.

The overall quality of the pre-autumn 1998 FWD database can be characterized as good to excellent.

17. Key Words

Long-Term Pavement Performance, LTPP, falling weight deflectometer, FWD, load-deflection data, deflection basin, deflection sensors, pavement deflection testing

18. Distribution Statement

No restrictions.

19. Security Classif. (of this report)

Unclassified

20. Security Classif. (of this page)

Unclassified

21. No. of Pages

103

22. Price

Form DOT F 1700.7 (8-72) Reproduction of completed page authorized

SI (Modern Metric) Conversion Factors

Table of Contents

  1. Introduction
  2. LTPP Data Screened and Reviewed
  3. Inconsistent FWD Deflection Basins
  4. Other Load-Deflection Data Errors
  5. Data Entry Errors
  6. Noted Anomalies and Other Potential Data Problems
  7. Suggested Computed Parameters and FWD Testing Protocols
  8. Summary and Conclusions

Appendix A. Various Feedback Reports Submitted to FHWA

Appendix B. Semiautomatic SLIC Procedure for FWD Data Screening

Appendix C. FWD SN #129, November 3, 1995–April 14, 1996

Appendix D. FWD SN #129, April 15, 1997–May 21, 1997

Appendix E. FWD SN #058, October 15, 1997–March 5, 1998

Appendix F. FWD SN #061, February 26, 1989–September 8, 1989

Appendix G. FWD SN #130, August 25, 1994–September 7, 1994

Appendix H. FWD SN #075, January 17, 1990–January 22, 1990

Appendix I. FWD SN #132, July 29, 1996–October 25, 1996

Appendix J. FWD SN #061, July 17, 1995–October 31, 1995

Appendix K. FWD SN #131, May 24, 1994–April 30, 1996

Appendix L. FWD SN #131, December 16, 1997–January 20, 1998

Appendix M. The Generalized Likelihood Ratio for H48 Over H60

References

List of Figures

  1. Graph. Frequency distribution of standard deviations for repeated deflections.
  2. Graph. Sensor 5 deflection readings for one LTPP section.
  3. Graph. Sample deflection basins transformed with SLIC (input protocol positions).
  4. Graph. Sample deflection basins transformed with SLIC (input actual positions).
  5. Equation. AREA.
  6. Equation. AREA (@ 20 ºC).
  7. Equation. Offset, with exponents d and e.
  8. Chart. Average deflections, FWD #131, August 12, 1998.
  9. Equation. y, x1, x2.
  10. Equation. a, b, c.
  11. Equation. Offset, sensor 2.
  12. Graph. Predicted position of d7, unit #129, 1995–96.
  13. Graph. Same section data for d7 position, two different FWDs.
  14. Graph. SLIC plots for section 34–0503 including unit #129, November 1995.
  15. Graph. SLIC plots for section 34–0507 including unit #129, November 1995.
  16. Graph. Predicted position of d7, unit #129, 1997–98.
  17. Graph. Same section data for d7 position, two different FWDs.
  18. Graph. SLIC plots for section 24–0509 including unit #129, May 1997.
  19. Graph. SLIC plots for section 36–4017 including unit #129, April 1997.
  20. Graph. Predicted position of d2, unit #058, 1997–98.
  21. Graph. Same section data for d2 position, two different FWDs.
  22. Graph. SLIC plots for section 10–0102 including unit #058, November–December 1997.
  23. Graph. R2 model for d2 prediction, unit #061, 1989–90.
  24. Graph. R2 model for d7 prediction, unit #061, 1989–90.
  25. Graph. SLIC plots for section 04–1017 including unit #061, April 1989.
  26. Graph. SLIC plots for section 08–9020 including unit #061, June 1989.
  27. Graph. SLIC plots for section 32–1030 including unit #061, February 1989.
  28. Graph. SLIC plots for section 49–1017 including unit #061, April 1989.
  29. Graph. SLIC plots for section 56–7773 including unit #061, June 1989.
  30. Graph. R2 model for d7 prediction, unit #130, 1994–96.
  31. Graph. Predicted position of d7, unit #130, 1994–96.
  32. Graph. SLIC plots for section 20–0101 including unit #130, August 1994.
  33. Graph. SLIC plots for section 20–0111 including unit #130, August 1994.
  34. Graph. SLIC plots for section 20–3060 including unit #061, September 1994.
  35. Graph. R2 model for d2 and d7 predictions, unit #075, 1990–97.
  36. Graph. SLIC plots for section 72–1003 including unit #075, January 1990.
  37. Graph. SLIC plots for section 72–4122 including unit #075, January 1990.
  38. Graph. Predicted position of d7, unit #132, 1995.
  39. Graph. Predicted position of d7, unit #132, 1996.
  40. Graph. Predicted position of d7, unit #132, 1997.
  41. Graph. Same section data for d7 position, three different FWDs.
  42. Graph. SLIC plots for section 48–k310 including unit #132, July 1996.
  43. Graph. SLIC plots for section 48–k350 including unit #132, August 1996.
  44. Graph. Predicted position of d7, unit #061, 1994–97.
  45. Graph. Same section data for d7 position, three different FWDs.
  46. Graph. SLIC plots for section 04–A310 including unit #061, July 1995.
  47. Graph. SLIC plots for section 32–7000 including unit #061, September 1995.
  48. Graph. Predicted position of d7, unit #131, 1994–97.
  49. Graph. Same section data for d7 position, four different FWDs.
  50. Graph. SLIC plots for section 08–6002 including unit #131, May 1995 and April 1996.
  51. Graph. SLIC plots for section 30–0805 including unit #131, August 1994.
  52. Graph. R-squared model for d2 prediction, unit #131, 1997–98.
  53. Graph. R-squared model for d7 prediction, unit #131, 1997–98.
  54. Graph. SLIC plots for section 41–7019 including unit #131, January 1998.
  55. Graph. SLIC plots for section 04–1065 including unit #131, January 1998.
  56. Graph. SLIC plots for section 06–3042 including unit #131, December 1997.
  57. Equation. Maximum likelihood estimate.
  58. Equation. The likelihood.
  59. Equation. Maximum likelihood estimate, sH = 48.

List of Tables

  1. Format of FWD load-deflection records from the pre-autumn 1998 database.
  2. Marked or flagged autoidentification criteria for various lanes.
  3. Autoidentification example of a marked FWD data record.
  4. FWD records identified for flagging in the pre-autumn 1998 database.
  5. FWD unit- and time-specific sensor positioning errors in the database.
  6. Likelihood ratios for protocol versus nonprotocol sensor positions for d7.
  7. General data anomaly notes of unchanged records or files.
  8. Deflection testing frequency analysis data.
  9. Initial SLIC procedure calculations for sensor 7.
  10. Final SLIC procedure calculations for sensor 7.
  11. Regression results, sensor 7.
  12. Likelihood ratio stats for protocol versus nonprotocol d7 sensor positions.

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