Concrete Cover Failure in FRP Reinforced Beams under Thermal Loading

The use of fiber reinforced polymer (FRP) rebars as a substitute for traditional steel rebars represents a very effective solution for reinforced concrete structures in corrosive environments. However, a better understanding of the mechanical behavior of reinforced concrete structures with FRP rebars is needed in order to use them for constructional purposes. As a consequence, some mechanical aspects, especially those related to the interaction between concrete and nonmetallic rebars, have to be correctly examined. In particular, the low thermal compatibility between concrete and FRP materials involves the occurrence of the splitting phenomenon under thermal loading when the confining action is inadequate; as a consequence, the failure of the concrete cover and a sudden drop of bond strength can take place. In the present paper, an analysis of possible failure mechanisms of the concrete cover under thermal loading is performed. An analytical model, able to evaluate the critical concrete cover and the minimum amount of the transversal reinforcement in order to avoid the concrete cover failure caused by the splitting, is described. Theoretical results are thus compared with experimental ones with reference to aramidic FRP reinforced concrete members.