Dynamic analysis of multi-layered pavement systems under moving arbitrary loads

A new solution for the dynamic analysis of multi-layered asphalt concrete pavement systems under moving arbitrary 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 a n-layered damped-elastic medium. The subgrade can be modeled as either a rigid base or a semi-infinite halfspace. The loads are surface circular loads which may be constant in magnitude or may vibrate as an arbitrary time function, 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 by 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: (1) it treats moving arbitrary loads on a n-layered damped-elastic system; (2) it incorporates such important factors as wave propagation, inertia and damping effects of the medium as well as frequency-dependent asphalt concrete properties; (3) it can handle any load configurations, thus making it possible to model multiple wheel configurations of truck axles and airplane landing gears.;The moving load solution of the developed program SAPSI-M has been validated with the PACCAR full-scale field truck tests, which was conducted on an instrumented asphalt concrete section on a test track at the PACCAR Technical Center in Mount Vernon, Washington. The transient analysis of the original SAPSI program has been validated using the PACCAR's results for Falling Weight Deflectometer (FWD) tests. Further, an approach based on energy dissipation and visco-elastic properties of an asphalt concrete pavement for predicting the fatigue life of asphalt concrete pavements has been presented using the moving load solution in SAPSI-M computer program. The effect of truck speed on the response of asphalt concrete pavements is significant, and the frequency-dependent properties of the asphalt are a major contributor to the speed effect. A simplified solution where the moving loads are assumed to be non-vibrating seems to be sufficient for accurately predicting the pavement response. Static analysis using statically back-calculated layer moduli seems to be sufficient in analyzing FWD field tests.