The Direct Structural Capacity Method as described in the AASHTO Guide for the Design of Pavement Structures provides a quick and simple method for analysing pavement deflections that are collected from nondestructive testing. However, results taken from 13 sites tested bimonthly during an 18-month period showed considerable variation with temperature even after the recommended AASHTO temperature correction procedures were applied. An alternative temperature correction procedure is derived from asphalt cement (AC) concrete temperature-modulus relationships and elasticity equations used to calculate composite pavement modulus. The alternative correction procedure requires knowledge of the ratio of AC bound layer thickness to non-AC bound layer thickness, the estimated average pavement temperature, and the ratio of AC bound layer stiffness to non-AC bound layer stiffness. Although the stiffness ratio is not known before temperature correction in a Direct Structural Capacity Method analysis, it is shown that the correction procedure is relatively insensitive to errors in the estimated stiffness ratio. Therefore, an estimate of the stiffness ratio is sufficiently precise for most pavement analyses. When the alternative procedure is applied to the data from the 13 test sites, it is shown to provide more uniform results with varying temperature. (Author/publisher)
Abstract