Preliminary Study to Enhance Ductility of CFRP-Strengthened RC Beam

Fiber-reinforced polymer (FRP) strengthening systems are widely accepted in engineering practice as means to enhance the flexural strength of RC members, but resulting in decreased ductility. Brittle failure, i.e., FRP rupture, FRP delamination, or concrete cover separation, impairs the reliability of FRP strengthening system. A near surface-mounted (NSM) FRP strengthening system has similar drawbacks. As a possible solution, a design philosophy is proposed to enhance the ductility of the NSM-FRP system by triggering a global slip at the FRP-adhesive interface. The corresponding design method is developed to induce the ductile failure and predict the ultimate strength of NSM FRP-strengthened RC member in flexure. A series of experimental tests were conducted to verify the effectiveness of the proposed method. The designed RC beams strengthened with NSM-carbon FRP (CFRP) outperformed the externally bonded CFRP systems both in ductility and flexural strength. Additionally, the proposed design method was experimentally validated by precisely predicting the ultimate strength of tested specimens. (c) 2016 American Society of Civil Engineers.