Pressure-sensitive bond fatigue model with damage evolution driven by cumulative slip: Thermodynamic formulation and applications to steel- and FRP-concrete bond

In this paper we introduce a thermodynamically consistent bond-interface pressure-sensitive damage model with cumulative sliding strain measure as a fundamental source of fatigue damage. The modeling approach provides a clear physical interpretation of the dissipative mechanisms governing the propagation of fatigue damage within the concrete-steel/FRP interface so that it is possible to reproduce both the monotonic and the cyclic behavior of the bond with a consistent set of material parameters. The model has been applied for simulation of the degradation process in the bond between concrete and reinforcement bars and between concrete and FRP sheets under pullout fatigue loading. The paper presents numerical studies of the fatigue pullout behavior with detailed analysis of the damage propagation during loading and unloading stages, and at different levels of imposed lateral pressure. To validate the ability of the model, simulations of pullout tests published in the literature have been conducted.