Long-Term Pavement Performance Program Determination of In-Place Elastic Layer Modulus: Backcalculation Methodology and Procedures

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.

The full report is available online at http://www.fhwa.dot.gov/publications/research/infrastructure/pavements/ltpp/15036/index.cfm