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Federal Highway Administration Research and Technology
Coordinating, Developing, and Delivering Highway Transportation Innovations
| REPORT |
| This report is an archived publication and may contain dated technical, contact, and link information |
 |
| Publication Number: FHWA-HRT-15-036 Date: December 2015 |
Publication Number: FHWA-HRT-15-036 Date: December 2015 |
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The Long-Term Pavement Performance (LTPP) database includes deflection basins measured on thousands of test sections across the United States. These deflection data were used to backcalculate the elastic layer modulus of both flexible and rigid pavements. This report documents the tools, data analyses, backcalculation and forward calculation packages, and procedures used to calculate the in-place elastic layer modulus of the LTPP test sections. It summarizes the backcalculated elastic layered modulus of both new and rehabilitated flexible and rigid pavements in the LTPP program and demonstrates their use in day-to-day practice for pavement design, rehabilitation, and management. Many agencies have used the LTPP deflection data for calibrating mechanistic-empirical distress transfer functions, including those in the Mechanistic-Empirical Pavement Design Guide.(1)
An important outcome presented in this report is the documentation of methods and procedures for calculating in-place elastic layer modulus, including the pre- and post-processing tools so the results can be recreated by others to make the process less user-dependent. In addition, the elastic modulus computed parameter tables included in the LTPP database (Standard Data Release 27.0 released in 2013) are defined and explained in this report so agencies can use these results in multiple areas.(2) This final report is intended for use by pavement researchers as well as by practicing engineers involved in rehabilitation design and management of agencies’ pavements.
Jorge E. Pagán-Ortiz
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.
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.
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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.
| 1. Report No. FHWA-HRT-15-036 |
2. Government Accession No. | 3 Recipient's Catalog No. | ||
| 4. Title and Subtitle Long-Term Pavement Performance Program Determination of In-Place Elastic Layer Modulus: Backcalculation Methodology and Procedures |
5. Report Date December 2015 | |||
| 6. Performing Organization Code | ||||
| 7. Author(s) Harold L. Von Quintus, P.E., Chetana Rao, and Lynne Irwin |
8. Performing Organization Report No.
| |||
9. Performing Organization Name and Address Applied Research Associates, Inc. |
10. Work Unit No. (TRAIS) | |||
| 11. Contract or Grant No. DTFH61-11-C-00051 | ||||
| 12. Sponsoring Agency Name and Address Office of Infrastructure Research and Development |
13. Type of Report and Period Covered Draft Final Report | |||
14. Sponsoring Agency Code
| ||||
| 15. Supplementary Notes The Contracting Officer’s Technical Representative (COTR) was Ms. Yan "Jane" Jiang. | ||||
| 16. Abstract Deflection data have been measured at periodic intervals with a falling weight deflectometer on all rigid, flexible, semirigid, and rehabilitated pavement test sections included in the Long-Term Pavement Performance (LTPP) program. A common use of deflection data is to backcalculate in-place layered elastic modulus values. The Federal Highway Administration sponsored earlier studies to backcalculate elastic layer modulus values from deflection basins measured on all LTPP test sections and included those computed values in the LTPP database.(3–5) While the earlier studies focus on the use of nonlinear methods and were considered to have minimal success, Some of the methods used have advanced within the past decade. As such, there was a need to revisit the methods used to improve on the results. This report summarizes all activities completed to backcalculate the elastic layered modulus from deflection basins measured on all test sections included in the LTPP program. Specifically, the report documents the tools, data analyses, backcalculation and forward calculation packages, and procedures used to calculate, on a production basis, the in-place elastic layer modulus of the LTPP test sections. Multiple packages (including BAKFAA, EVERCALC©, MICHBACK©, MODULUS, MODCOMP©, and the area and best fit methods) were considered and evaluated for estimating layered elastic modulus values on a production basis. (See references 6–10.) The methods used in production for backcalculating elastic layer moduli include a combination of EVERCALC© and MODCOMP© for all types of pavements and the best fit method for rigid pavements. The methods and procedures, including the pre- and post-processing tools, have been automated so the results can be recreated by others not directly involved in development of the tools and procedures. The report also summarizes the results from the production runs to calculate the elastic layered modulus of flexible and rigid pavements (new construction and rehabilitation) as well as demonstrate the application and use of the results. | ||||
| 17. Key Words Backcalculation, Deflection data, Elastic modulus, EVERCALC©, Falling weight deflectometer, Long-Term Pavement Performance, LTPP, MODCOMP©, MODTAG©, Modulus, Mechanistic-Empirical Pavement Design Guide, Pavement evaluation |
18. Distribution Statement No restrictions. This document is available to the public through the National Technical Information Service, Springfield, VA 22161. | |||
19. Security Classification Unclassified |
20. Security Classification Unclassified |
21. No. of Pages 177 |
22. Price | |
| Form DOT F 1700.7 (8-72) | Reproduction of completed page authorized |
SI* (Modern Metric) Conversion Factors
Chapter 2. Backcalculation Methodology and Packages
Chapter 4. Backcalculation Process
Chapter 5. Backcalculation Results
Chapter 6. Application and Use of Backcalculation Results
Appendix A: Best Fit Method—Calculating PCC Elastic Layer Moduli
Appendix B: LTPP Test Sections with a Moderate and High Percentage of Errors
Appendix C: Development of the Simulated Layer Structure for the Backcalculation Process Using Evercalc© and Modcomp©
References
| AASHTO | American Association of State Highway and Transportation Officials |
| AC | asphalt concrete |
| ANN | artificial neural network |
| ATB | asphalt-treated base |
| CPT | computed parameter table |
| CRCP | continuously reinforced concrete pavement |
| FHWA | Federal Highway Administration |
| FWD | falling weight deflectometer |
| GB | granular base |
| GPR | ground-penetrating radar |
| GPS | General Pavement Studies |
| GS | granular subbase |
| HMA | hot mix asphalt |
| JPCP | jointed plain concrete pavement |
| JRCP | jointed reinforced concrete pavement |
| LTE | load transfer efficiency |
| LTPP | Long-Term Pavement Performance |
| MEPDG | Mechanistic-Empirical Pavement Design Guide |
| PCC | portland cement concrete |
| RAP | reclaimed asphalt pavement |
| RMSE | root mean squared error |
| SDR | Standard Data Release |
| SHRP | Strategic Highway Research Program |
| SLIC | Sensor Location Independent Check |
| SMP | Seasonal Monitoring Program |
| SPS | Specific Pavement Studies |
| SS | subgrade soil |
| TB | treated base |
| TS | treated subgrade |
