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Project Information
Project ID:   FHWA-PROJ-11-0066
Project Name:   Backcalculation of the Long-Term Pavement Performance Program Deflection Data
Project Status:   Completed
Start Date:  September 30, 2011
End Date:  December 29, 2015
Contact Information
Last Name:  Jiang
First Name:  Yan (Jane)
Telephone:  202-493-3149
E-mail:  jane.jiang@dot.gov
Office:   Office of Infrastructure Research and Development
Team:   Long-Term Pavement Performance Team [HRDI-30]
Program:   Long-Term Pavement Performance
Project detail
Project Description:   This study shall first evaluate and decide on the most appropriate method(s) for backcalculation of the Long-Term Pavement Performance (LTPP) deflection data for different pavement types. Using the selected method(s), backcalculated moduli and related parameters shall be derived and integrated into the LTPP database.The research shall consist of two phases. The goal of phase I is to evaluate and select appropriate methodology for backcalculation of the LTPP deflection data, covering both flexible and rigid pavement structures. The process shall include literature and LTPP data reviews, and case studies on selected LTPP sections using candidate backcalculation methods. The contractor shall submit an interim report, including a detailed phase II work plan.
Background Information:   The Federal Highway Administration (FHWA) intends to sponsor a research project to perform backcalculation of the deflection data collected by the Long-Term Pavement Performance (LTPP) program.  Characterization of in situ pavement layer moduli through nondestructive testing is an essential part of the pavement structural monitoring as well as rehabilitation evaluation and design. The need to accurately characterize the structural condition of the pavement has increased with the implementation of the Mechanistic-Empirical Pavement Design Guide (MEPDG). The LTPP program has been collecting pavement deflection data using Falling Weight Deflectometers (FWDs) for more than 20 years on its 2,400+ test sections. This deflection-testing program is being conducted periodically to ascertain the change in load-response characteristics of the pavement structure and subgrade over time, on both flexible and rigid pavements.  The LTPP Database contains both large amounts of FWD measurements and pavement layer material characteristics necessary to derive backcalculated pavement layer moduli. The first round of the LTPP backcalculation study was conducted in 1999. The research approach and results are documented in the following reports: Backcalculation of Layer Parameters for LTPP Test Sections, Volume I (FHWA-RD-00-086) and Volume II (FHWA-RD-01-113). A followup study was conducted to review the LTPP backcalculation results (FHWA-HRT-05-150). The current version of the LTPP Database standard data release (SDR), as well as the resulting analysis datasets from the first round backcalculation study, are available through the LTPP Customer Support Services Center at 202–493–3035 or ltppinfo@dot.gov. Since the first round LTPP backcalculation study based on FWD deflection data collected through 1999, much more FWD deflection data have been collected and added into the LTPP database. In addition, the LTPP program recently finished an extensive and focused review of the materials characterization data in the LTPP database, and made significant improvements in terms of data availability and quality in the latest LTPP standard data release (SDR #25). Furthermore, the backcalculation methods have continued to advance in the past decade. There is a need to not only conduct backcalculation on all the LTPP deflection data using the latest dataset, but also to revisit the backcalculation methods used in the first round of the LTPP backcalculation.
Field Test:   Falling weight deflectometer
Product Type:   Data
Research report
Technical report
Test Methodology:   Falling weight deflectometer deflection measurements.
Other Information:   LTPP Analysis Plan | Objective 2 | Outcome B | Project 7 | Priority Very High | Sequence 1
Expected Benefits:   The results from this study will be of significant interest and use to the pavement community. Backcalculated moduli are key inputs in pavement structural evaluation and rehabilitation or reconstruction design. Both the pavement design engineers and researchers need the backcalculated moduli for characterization of the in situ pavement layers as well as for pavement structural monitoring and remaining life estimation.
Deliverables: 1. Name: Final report and related documents.
Product Type(s): Research report, Data
Description: The contractor shall prepare a final report documenting the work performed, findings from investigations performed, results, and suggestions for future research. In addition, the contractor shall prepare and submit a Long-Term Pavement Performance (LTPP) TechBrief. Feedback reports will also be submitted by the contractor to the Federal Highway Administration documenting any questionable data, discrepancies, or other data problems that need to be explained or corrected.
Publication URL(s):
2. Name: Backcalculation and data processing software developed.
Product Type(s): Data, Software
Description: The contractor shall, with the final report, deliver the source, executable code, and a list of any third party off the shelf components used, and required Federal Highway Administration documentation for preprocessing and postprocessing of Long-Term Pavement Performance data and other software developed under this contract.
3. Name: Long-Term Pavement Performance computed parameter tables.
Product Type(s): Data, Technical report
Description: Analysis datasets developed for conducting backcalculation.Backcalculated computed parameter tables data, and related documentation.
Related URL(s):   http://www.fhwa.dot.gov/publications/research/infrastructure/pavements/ltpp/15036/15036.pdf
FHWA Topics:   Research/Technologies--Turner-Fairbank Highway Research Center (TFHRC)
TRT Terms:   Pavement Performance
Falling Weight Deflectometers
FHWA Disciplines:   Pavement and Materials
Subject Areas:   Highways


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