A proposal for modeling debonding of NSM FRP strips for shear strengthening of RC beams

Abstract

Gluing of FRP strips within thin shallow slits cut in the concrete cover of RC beams is a strengthening technique that is gaining increasing attention in the FRP community. It has proven to be effective for both shear and flexural strengthening of existing RC structures that need a retrofitting intervention. Recent findings have highlighted that such near surface mounted (NSM) strips may fail due to: debonding, concrete semi-conical tensile fracture and strip tensile rupture. The necessity to improve an analytical model for predicting the NSM FRP strips shear strength contribution led to further address issues related to bond mechanism through which force in the strip is transferred to the surrounding concrete. A new local bond stress-slip relationship is proposed and closed-form equations to be implemented in that analytical model are derived and appraised on the basis of some of the most recent experimental results.