Calibration of Mechanistic–Empirical Pavement Design Guide Permanent Deformation Models

Abstract

The performance models in the Mechanistic–Empirical Pavement Design Guide (MEPDG), developed under NCHRP 1-37A and 1-40D, are calibrated with sections throughout the United States. Hence, it is necessary to calibrate these models for specific states and regional conditions because of the differences in materials, environmental conditions, and construction practices. In general, a pavement design based on the nationally calibrated MEPDG will result in either an overestimate or underestimate of the pavement layer thicknesses because of systematic errors arising from local differences. This deficiency calls for local calibration of the performance models in the MEPDG so that they can be used to design pavements at a regional level. The calibration procedure described in this paper concentrates on finding two bias correction factors for the asphalt concrete (AC) permanent deformation performance model after values derived from expert knowledge have been assumed for the subgrade permanent deformation calibration factors. Pavement data from the Texas Specific Pavement Study (SPS)-1 and SPS-3 experiments of the Long-Term Pavement Performance database were used to run the MEPDG and calibrate the guide to Texas conditions. The regional calibration factors were obtained by minimizing the sum of squared errors between the observed and predicted surface permanent deformation. In this case, a simultaneous joint optimization routine was applied because it was theoretically sound. Finally, an average of the regional calibration coefficients for AC and subgrade permanent deformation was computed to obtain the set of state-default calibration coefficients for Texas.