A competitive mechanism driven damage-plasticity model for fatigue behavior of concrete

In this paper, an innovative three-dimensional plastic-damage model is proposed to describe the behavior of concrete material under fatigue loading. In the proposed model, two damage variables are defined to describe the fatigue degradation of the mechanical properties of concrete under tension and shear, respectively. Meanwhile, by adopting the elastoplastic damage energy release rates, which are derived from the elastoplastic Helmholtz free energy potentials, a novel fatigue damage evolution law is developed. Specifically, the damage evolution process is governed by the competition between the damage healing effect and the damage driving effect induced by the propagation and closure of micro cracks under fatigue loading. The proposed model also allows the accumulation of fatigue damage within the classical damage surface by adopting the loading/unloading irreversibility concept. Moreover, the evolution of plastic strains is considered within the framework of the effective stress space plasticity. In the end, a set of numerical tests is presented, and the validity and effectiveness of the proposed model are illustrated according to the simulated results and the comparisons with the experimental data in literatures.