Experimental and numerical study of strengthening of heat-damaged RC beams using NSM CFRP strips

An experimental and numerical study of eight reinforced concrete beams is reported in this paper. In the experiments, two beams were normal temperature controls, and the other six beams were heated under the ISO-834 standard fire curve. All beams had the same geometrical dimensions, reinforcement and loading and support arrangements. The flexural behaviour was studied after exposure to 600 and 700 °C for two hours. Two beams were un-strengthened fire-damaged control beams and the other four beams were strengthened with carbon fibre-reinforced polymer (CFRP) laminates after exposure to heating. The results showed that the mid-span ultimate load, stiffness, and ductility of the heat-damaged beams decreased compared with those of the normal-temperature control beam. Although the ultimate load and stiffness decreased, repair with near-surface mounted (NSM) systems to the CFRP laminate using an epoxy- or cement-based adhesive in grooves cut into the concrete surface was found to increase the load capacity and stiffness of the beams. The finite element models (FEMs) were able to predict the experimental behaviour reasonably well.