Finite element analysis of intermediate crack debonding in fibre reinforced polymer strengthened reinforced concrete beams

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The performance of the fibre reinforced polymer (FRP) to reinforced concrete (RC) interface is vital to ensure desired design capacity. Without proper understanding of the interfacial behaviour it is impossible to develop an effective, efficient, and rational bonding technique. This paper presents the results of a comprehensive numerical investigation aimed to assess and better understand the debonding behaviour caused by different types of intermediate flexural crack distributions in FRP–RC strengthened beams. The model is based on damage mechanics modelling of concrete, a bilinear bond–slip relationship with softening to represent the interface, and a discrete crack approach to simulate crack propagation. The model also highlights how crack propagation and debonding is affected by the rate of change of moment. It is shown that the variation of crack spacing and rate of change of moment can significantly affect debonding crack propagation and strain development in the internal and external reinforcement, which directly influences debonding load.