Nonlinear Viscoelastic Behavior of Asphalt Concrete and its Implication on Fatigue Modeling

摘要

Mechanistic models for asphalt concrete (AC) can consider many different physical mechanisms.However, as more mechanisms are considered, the complexity increases, and it becomesimportant to balance accuracy and complexity to create a model that can be used by theengineering community. In some cases, the material response is dominated by the effects of onlysome key processes and smearing the effects of the minor ones is acceptable. In other cases,many different processes are important and need to be considered. In this paper, the importanceof modeling the nonlinear viscoelasticity (NLVE) of AC for fatigue response prediction isassessed. Two mechanistic hypotheses are considered for describing this phenomenon; 1) linearviscoelastic with damage and 2) NLVE with damage. The importance of explicitly consideringNLVE effects under fatigue loading is evaluated by using laboratory tests, the simplifiedviscoelastic continuum damage (S-VECD) model, and a NLVE form of the S-VECD model.These two models are characterized and used to simulate and compare AC fatigue responseunder constant and random controlled stress and strain conditions. It is found that while theNLVE based formulation better represents the material response in random loading and suggestsless overall damage accumulation during fatigue, that the two models predict very similaramounts of modulus reduction. The primary conclusion from this study is that since the goal forfatigue assessment is to find the change in modulus over a long period of time, fatigue responsemodeling of AC does not need to explicitly consider NLVE.