A finite element method for the performance analysis of flexible pavements

Abstract

The purpose of this study is to present a computer program, named FEPASS, to predict the performance of asphaltic concrete pavements. Methods have been developed that predict the rutting, the fatigue cracking, and the slope variance of the pavement with time in service. The framework for the development of the prediction models is based on the stress, strain, and deformation within the pavement by the finite element method, on the mechanistic methods, and on the material characterization of each pavement component. Rutting is calculated as the integration of the resilient vertical strains multiplied by the fractional increase of total strains for each material layer of the pavement. The resilient strains of pavement structures under traffic loadings are calculated using a finite element structural analysis. The fractional increase of total strain is related to three parameters which characterize the permanent deformation relations which are measured in the laboratory. Regression equations are developed for these parameters for each type of material. The most important terms in the equations are the asphalt content, temperature, resilient modulus, and stress state for asphalt concrete material, and the water content, resilient modulus, and stress state for base and subgrade soils. The fatigue characterization of the asphaltic concrete mix is based on the fatigue crack growth rate which, in turn, is related to the phenomenological fatigue equation derived from laboratory fatigue tests. A mechanistic-empirical shift factor has also been developed for translating the predictions to approximate fatigue life actually measured in the field. The cracked surface area caused by the traffic load applications is evaluated by using a stochastic version of Miner's law. The prediction of the slope variance is based on the stochastic variation of the rutting and on the assumption that the spatial autocorrelation function is related to the variability of deflections along the length of the pavement. A comprehensive study of the predicted and measured performance of selected AASHO Road Test sections is made using the FEPASS program. The method of calibration of all of the distress models to the AASHO Road Test is described...