Mechanical Model to simulate the NSM FRP strips shear strength contribution to RC beams

A three dimensional mechanical model has been recently developed to simulate the Near Surface Mounted (NSM) Fibre Reinforced Polymer (FRP) strips shear strength contribution to Reinforced Concrete (RC) beams throughout the entire loading process, as function of the Critical Diagonal Crack (CDC) opening angle. It was developed by fulfilling equilibrium, kinematic compatibility and constitutive laws of both intervening materials and bond between them. It takes into consideration all of possible failure modes that can affect the behaviour, at ultimate, of a single NSM strip, namely: loss of bond (debonding), semiconical concrete tensile fracture, rupture of the strip itself and a mixed shallow-semi-cone-plus-debonding failure. Besides, it allows the interaction among adjacent strips to be accounted for. The numerical results, in terms of both shear strength contribution and predicted cracking scenario are presented and compared with experimental evidence regarding some of the most recent experimental programs. From that comparison, a satisfactory level of prediction accuracy, regardless of the main parameters such as concrete mechanical properties, amount and inclination of strips, arises. The main findings, as well as the influence of some of the main intervening parameters, are shown.