A robust and efficient 3D mixed-mode cohesive interface model for predicting the debonding failure in FRP strengthened concrete structures

Abstract

A new and practical cohesive zone model (CZM) considering the coupling between damage mechanics and plasticity is proposed to facilitate structural-scale finite-element (FE) simulations for concrete members strengthened with fiber-reinforced polymer (FRP). The model dwells on an adaptive sub-stepping technique to overcome common convergence difficulties during mixed-mode debonding between FRP and concrete. Additionally, it automatically adjusts the computational time increment based on the convergence performance of Newton-Raphson iterations, ensuring efficiency by applying time stepping selectively to critical integration points with diverging problems. Moreover, the model introduces a transformation between effective stress and nominal stress to enhance numerical stability when dealing with complex interfacial behaviors like stiffness degradation, plastic deformation, dilation effects, and mixed-mode failure. Thus, the paper’s novelty lies in the development of a stable and versatile 3D interface model achieved through advanced numerical optimization techniques. The resulting FE models have accurately reproduced various failure modes, such as FRP-concrete debonding and local buckling of FRP plates, demonstrating a high level of reliability and computational efficiency.