Abstract: A bilinear damage cohesive zone model is used to simulate Mode-I fracture of FRP-concrete bonded interfaces in three-point bending beam (3PBB) specimens. The relationships among the interface cohesive strength, the concrete tensile strength and the fracture energy are discussed in detail through a numerical finite element (FE) parametric study. The results of FE simulations show that there is a transition in the failure mechanism between the debonding of the FRP-concrete interface and the cracking in the interfacial concrete layer near the interface. Such a transition cannot be explained by a fracture-mechanics approach to the crack propagation which only uses an energy criterion for fracture. By combining a damage cohesive law model for the interface and a plastic-damage model for the concrete, the essential features of the transition in failure mechanism are captured. The cohesive damage models for the interface and the concrete combined with the numerical finite element simulation presented in this study can be used to analyze the interface fracture process, predict the load-carrying capacity and ductility, and optimize the interface design.