Creep model for the long-term behaviour of combined cohesive-bridging model of FRP–concrete interface debonding under axial loading

External bonding of fibre-reinforced polymer (FRP) plates has emerged as a method for strengthening reinforced concrete structures. The creep of the concrete, adhesive and FRP can accelerate debonding along with the interface. In this paper, an original creep model is developed to study the long-term behaviour of combined cohesive-bridging model of an FRP–concrete interface, debonding under axial loading. A combined cohesive-bridging zone model is presented to simulate long-term debonding between the FRP plate and concrete beam interface. Four zones are distinguished and thoroughly analysed: elastic, softening, bridging and debonding. An original behaviour law is proposed, combining the creep modelling of the various materials. A new analytical model of the long-term shear stress distribution along the interface is developed. For application data, the bond-slip parameters for a real-time combined cohesive-bridging model along the FRP–concrete interface are determined by calibration based on the experimental and analytical data in the pre-existing literature. The simulation of the long-term bond-slip law of the FRP–concrete interface is based on the constant fracture energy Gf and shearing rigidity of the interface. The parametric study suggests that to extend the durability of an FRP–concrete interface, loads should be in the elastic stage, and thick, highly rigid FRP plates should be used.