A Unified concrete damage model for monotonic loading and fatigue loading

In this work, a unified damage model is proposed for describing the mechanical behavior of concrete under monotonic loading and fatigue loading. Based on the micro‐meso stochastic fracture model (MMSF), the multiscale energy dissipation within the microspring is investigated. The rate process theory and a crack hierarchy model are employed to describe the nanocrack growth rate and crack number, respectively. It is found out that the fracture strain of the microspring can be derived from the energy dissipation analysis. The expression of the stochastic damage evolution law is changed to “energy dissipation threshold” instead of “fracture strain.” The new model can describe different damage evolution forms under monotonic and fatigue loading with the same parameters. The mechanisms of different damage evolution laws under different loading modes are analyzed in detail. Finally, a numerical example is presented to verify the proposed model.