Modeling of CFRP-concrete interface subjected to coupled pull-out and push-off actions

This paper presents a finite element (FE) modeling method for predicting the IC debonding failure when the FRP/concrete interface is subjected to coupled pull-out (shear) and push-off (dowel) actions. Damaged plasticity model was used to simulate the behavior of concrete close to FRP/concrete interface. A thin damage band exposed to mixed-mode loading condition was modeled separately along the FRP-concrete interface. Cohesive elements were used to model the FRP/concrete interface. A sensitivity analysis was performed to find the appropriate damaged band dimensions, bending stiffness of FRP, and tensile strength of concrete for the model. The numerical results were validated by the experimental data. It was found in this research that the thickness of damage band was not a key parameter when Mode I loading dominated the debonding failure, FRP flexural stiffness had significant effect on behaviors of the strengthened beams, and the concrete tensile strength itself cannot be used as the unique failure criterion for predicting debonding failure.