DEVELOPMENT OF A SIMPLIFIED FATIGUE TEST AND ANALYSIS PROCEDURE USING A VISCOELASTIC, CONTINUUM DAMAGE MODEL (WITH DISCUSSION)

This paper presents a methodology by which the material response under various uniaxial tensile testing conditions (type of loading and temperature) can be predicted from the material response obtained from a single testing condition. The methodology makes use of a uniaxial constitutive model for asphalt concrete that is based upon the elastic-viscoelastic correspondence principle and work potential theory, a continuum damage theory based on the thermodynamics of irreversible processes. Uniaxial tensile testing is performed under a controlled crosshead mode for both cyclic and constant rate to failure tests. Various strain amplitudes, frequencies, and rates are applied at several test temperatures. A single characteristic curve can be found that describes the reduction in material integrity as damage grows in the specimen, regardless of the applied loading conditions (cyclic versus monotonic, amplitude/rate, frequency). The characteristic curve at any temperature below 20 deg C can be found by utilizing the time-temperature superposition principle and the concept of reduced time. In this study, eight WesTrack mixtures were tested and the methodology was applied to successfully predict the fatigue damage at different testing conditions from a single condition. A test and analysis procedure for the fatigue characterization of asphalt mixtures based on this methodology is proposed and potential applications are discussed.