Bond behaviour between externally bonded Fiber Reinforced Polymer (FRP) strengthening and concrete supports is essential in shear and flexural applications, in order to transfer stress between concrete and external reinforcement, and influences the nominal capacity of the structural element. In the majority of cases, constitutive models τ- s (shear/bond stress-slip) available in the literature, are not directly calibrated with experimental results, partly due to the difficulty of obtaining τ- s diagrams experimentally. This paper aims at improving knowledge of bond behaviour between FRP and concrete, and presents a critical review of the principal bond-slip models currently available in the literature and a new proposal calibrated on the basis of experimental τ- s diagrams, taking into account the influence of FRP strengthening rigidity. A new expression for interfacial fracture energy is also proposed and validated with experimental results.
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