Failure modes and failure mechanisms of RC members strengthened by NSM CFRP composites – Analysis of pull-out failure mode

Abstract

The aim of the experimental programme developed in this work was to study the failure modes and the pull-out failure mechanism of RC members strengthened by Near Surface Mounted reinforcement (NSM) technique. The global behaviour of reinforced concrete beams strengthened by NSM and subjected to flexure was investigated. The rods were 6- and 12-mm-diameter carbon–epoxy pultruded FRP. Two vibrated concrete compositions were tested: conventional (VC30) and high-strength (VC60), and one filling material: epoxy resin. The study was carried out up to the failure load, and focused on the failure modes of the beams. The experimental results were compared with the analytical model for the pull-out failure mode of FRP rods. Based on the concept of the anchorage length beyond the last crack, the calculation gives a good approximation of the ultimate bond stress in the cross-section located at the last crack.