Debonding failures in RC beams strengthened in flexure with near-surface mounted (NSM) CFRP strips
The method of strengthening reinforced concrete (RC) structures using near-surface mounted (NSM) FRP reinforcement has attracted increasing attention in recent years as a promising alternative to externally bonded FRP reinforcement. In the NSM FRP method, grooves are cut into the concrete cover of RC members for the embedding of FRP bars using an adhesive. Compared to the externally bonded FRP method, the NSM FRP method has a number of advantages including improved bond efficiency and better protection of the FRP reinforcement. Despite the improved bond performance, debonding failures of various forms are still likely to occur in RC members strengthened with NSM FRP bars. This paper presents a summary of a major recent study undertaken by the authors on such debonding failures in RC beams strengthened in flexure with NSM CFRP strips (i.e. bars of narrow rectangular section). CFRP strips were focused on in the study because they possess a larger perimeter-to-cross-sectional area ratio than bars of other shapes, and thus offer the best bond efficiency with the RC member being strengthened.