Response and fatigue performance modeling of ALF pavements using 3-D finite element analysis and a simplified viscoelastic continuum damage model

This paper presents results from a study that uses an in-house developed finite element analysis program, FEP++, and a simplification of the viscoelastic continuum damage model to help determine the response and fatigue performance of asphalt pavements. Finite element analysis yields ultimate flexibility for the inclusion of viscoelasticity, stress-state dependence of unbound paving layers, damage or any other processes or mechanisms that are known to affect the behavior of asphalt concrete pavements. The in-house developed software mitigates the need to use expensive commercial packages, such as ABAQUS or ANSYS. In this work, the asphalt concrete layers are considered as linear viscoelastic and the unbound layers as linear elastic. The advantage of using this level of complexity is that it offers an improved representation of asphalt concrete pavements while using the same inputs that are required for the NCHRP 1-37A Mechanistic Empirical Pavement Design Guide. After using the finite element package to assess the impacts of wheel speed, temperature gradient, and material type on pavement response, attention turns towards an advanced mechanistic material model for predicting the fatigue response of asphalt concrete, the viscoelastic continuum damage model. This model is characterized with mixtures from the Federal Highway Administration Accelerated Load Facility and is found to capture an underlying material property, the damage characteristic relationship. Finally, results from finite element simulations of these pavements are combined with the advanced material model in a simplified modeling scheme to predict the fatigue performance of these pavements.