Damage-Based Analysis to Guide the Development of MEPDG Axle Load Distribution Factors and Clustering for North Carolina.

This paper shows ways that the Mechanistic-Empirical Pavement Design Guide (MEPDG) can be utilized to develop damage factors to guide the development of MEPDG Axle Load Distribution Factor (ALDF) clusters. Pavement designers using the MEPDG must select the most appropriate ALDF clusters, in addition to other traffic data, for a particular project location before they can run any trial design. The MEPDG considers four axle types in ALDF input: single, tandem, tridem, and quad. A total of 140 axle type-load combinations are associated with these four axle types. In this paper, damage factors are developed for each of these combinations based on bottom-up fatigue damage as the failure criterion. Furthermore, bilinear functions are developed to enable partial factorial runs using the MEPDG to save time and effort. In this study, the MEPDG traffic input tables are adjusted to force the MEPDG to apply a certain axle type-load combination. Results show that the 82-kip tandem axle has the highest damage factor among the axles. Based on the damage-based analysis, tridem and quad axles, in addition to some heavy single and tandem axles, are excluded from the ALDF clustering process because these axle type-load combinations do not significantly affect pavement performance but can bias the results of ALDF clusters because of the infrequent occurrence of these axles.