Micro-To-Meso Scale Mechanisms for Modelling the Fatigue Response of Cohesive Frictional Materials

This work deals with a research study on the fatigue behavior of cohesive frictional materials like concrete or mortars. A two-scale approach will be proposed for analyzing concrete specimens subjected to either low- or high-cycle fatigue actions. The multiscale technique is based on a combination of a micro-scale procedure, to describe the microstructural defects affecting the cyclic response, which is subsequently homogenized to the upper meso- and macroscopic failure. More specifically, projected microscopic representative volume elements, equipped with a fracture-based model and combined with a continuous inelastic constitutive law that accumulates damages induced by cycle behaviors, represents the lower scale. A plastic-damage based model, for concrete subjected to cyclic loading, is developed combining the concept of fracture-energy theories (within the family of fictitious crack approaches) with stiffness degradation, the latter representing the key phenomenon occurring in concrete under cyclic responses. The work will numerically explore the potential of the various techniques for assessing the fatigue formation and growth of (micro-, meso- and macro-) cracks, and their influence on the macroscale behavior.