Application of viscoelastic continuum damage model based finite element analysis to predict the fatigue performance of asphalt pavements

The Viscoelastic Continuum Damage (VECD) model has been implemented into a finite element package (FEP++) to predict the fatigue performance of asphalt concrete (AC) mixtures tested at the Federal Highway Administration Accelerated Load Facility (FHWA ALF) and the Korea Expressway Corporation (KEC) test road project sites. Both the VECD model and the FEP++ were developed at North Carolina State University. The conceptual approach taken for this research is to separate the characteristics of the pavement system that are related to the material from those related to the boundary conditions. It is believed that this study is the first application of an integrated structural/material mechanistic model for the fatigue performance prediction of AC pavements where damage in the asphalt layers is considered for the full time history and where the change in stiffness due to damage evolution is captured in the subsequent calculation of damage. The VECD model accounts for the viscoelastic nature of AC mixtures with growing damage, whereas the finite element model accounts for other important characteristics, such as temperature, layer thickness, stiffness gradient, etc. The controlled FHWA ALF experiment allows a direct comparison between observed and modeled fatigue performance. Because the KEC test road experiment is subjected to real and variable traffic and environmental factors, the finite element simulation results are used to examine the effects of specific parameters in the pavement system on fatigue performance. In this regard, the model is found to effectively capture the effects of changes in layer thickness, layer material, and layer type. The need to develop transfer functions for true field performance prediction is also shown, and a simple example function is developed as proof of this concept.