SAPSI-M: Computer Program for Analyzing Asphalt Concrete Pavements under Moving Arbitrary Loads

Abstract

A new solution for the dynamic analysis of asphalt concrete pavements subjected to moving fluctuating loads has been developed. The method builds on an existing model for stationary loads, SAPSI, which uses the complex response method of transient analysis with a continuum solution in the horizontal direction and a finite-element solution in the vertical direction. The structural model is an n-layered damped-elastic medium. The subgrade can be modeled as either a rigid base or a semi-infinite half space. The loads are surface pressure loads, and the analysis is under axisymmetric conditions. The moving loads are modeled as a series of pulses with a duration equal to the time required for the wheel to pass a fixed point in the pavement. The proposed method of analysis in the new version of the program, SAPSI-M, is an improvement over the existing methods because (a) it treats moving fluctuating loads on an n-layered damped-elastic system; (b) it incorporates such important factors as wave propagation, inertia, and damping effects of the medium, as well as frequency-dependent asphalt concrete properties; and (c) it can handle any load configuration, thus making possible the modeling of multiple wheel configurations of truck axles and airplane landing gears. Theoretical results have shown that the effect of vehicle speed is significant, in part due to the frequency-dependent properties of the asphalt concrete. Comparison with field strain data from full-scale pavement tests has shown excellent agreement.