AbstractFiber-reinforced polymer (FRP) composites are widely employed as externally bonded reinforcement (EBR) systems for strengthening reinforced concrete members. More recently, a new technique, referred to as externally bonded reinforcement on grooves (EBROG), has been proposed, which is based on using a number of grooves throughout the concrete substrate to enhance the bond strength between the FRP composite and concrete. This study investigates the influence of groove depth on the resulting debonding process that can be observed in prestressed carbon FRP strips. To do so, prestressing force release tests were conducted on a series of EBR and EBROG FRP strips bonded to concrete specimens. Test results demonstrated that the fracture process leading to debonding of the EBROG specimens developed in a significantly different manner with respect to the case of EBR specimens. Specifically, fractures ran through deeper layers of concrete as the grooves became deeper. Numerical analyses are also proposed to scrutinize the actual bond–slip law characterizing both EBR and EBROG specimens. It was shown that a trilinear bond–slip law is appropriate for simulating the interface behavior in EBROG specimens.

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