A novel damage model integrated into the elastoplastic constitutive model and numerical simulations of reinforced concrete structures under cyclic loading

To develop an advanced predictive finite element (FE) model for accurately 3D simulating reinforced concrete (RC) structures under cyclic loading, a novel damage model, known as the Zhang-Hou damage model, has been developed. This model is integrated into the elastoplastic constitutive model, and subsequently implemented in the FE software ABAQUS. Unlike the conventional Barcelona damage model, this novel model employs the concept of plastic degradation to describe concrete damage. Notably, it is capable of characterizing concrete damage throughout the entire plastic deformation process rather than merely addressing the softening regime. This is accomplished by modelling damage effects through strain variables as opposed to stress variables. To improve accuracy in describing the unloading-reloading stiffness, the damage effect coefficients are calibrated using the cyclic test results. Furthermore, the model's ability to capture the behaviour of the RC structure is assessed by simulating a cyclic laboratory test on an RC frame structure. The FE predictions achieve the mesh convergence and agree well with the test data, thereby validating the developed model. Following this validation, simulations of three additional experiments involving RC structures under cyclic loads are conducted, and the Barcelona damage model and the Birtel & Mark damage model as well as bond-slip modelling approaches are investigated. The results reveal that the developed model outperforms the others in accurately predicting load capacity and energy dissipation. Also, the FE models incorporating the developed model can effectively capture both crack progression and cyclic damage evolution under different loading cycles.