Evaluation of Some Key Assumptions of Mechanistic-Empirical Pavement Design Guide and Quantification of Its Impact on Prediction Accuracy

completed

This is a continuation of fiscal year 2009 activity DTFH61-08-D-00001-T005. As part of a graduate research fellowship project in fiscal year 2008 and the ongoing fiscal year 2009 activity, a stand-alone application incorporating relevant portions of Mechanistic-Empirical Pavement Design Guide flexible pavement analysis procedures was developed to conduct independent evaluations of some of the key Mechanistic-Empirical Pavement Design Guide assumptions. Fiscal Year 2009 efforts evaluated the effect of loading frequency computation on Mechanistic-Empirical Pavement Design Guide rutting and bottom-up fatigue cracking predictions for flexible pavements. A draft report of this evaluation has been developed and is being reviewed. Efforts are continuing on evaluating the effect of change in layer moduli due to accumulated damage on the predicted pavement performance. The Mechanistic-Empirical Pavement Design Guide currently accounts for aging effects but not for accumulated damage and resulting weakening of the pavement structure. Fiscal Year 2010 activities will continue this evaluation and will also explore other recursive algorithms to account for damage accumulation on predicted distress. In addition, efforts will focus on evaluating the effect of level 1 versus level 3 inputs on design reliability using the simulation-based reliability approach that was developed. The current reliability procedure in the Mechanistic-Empirical Pavement Design Guide is not capable of accounting for the improved reliability of inputs in the predicted output. This hinders a more reliable design through accurate input parameter estimation and quality control efforts and relies on the thickening of pavement structure.