Fire endurance and residual strength of insulated concrete beams strengthened with near surface mounted reinforcement

The comparatively weak performance of fiber-reinforced polymer (FRP) strengthened members under fire exposure is a primary factor hindering the application of FRP strengthening in buildings in which fire risk is not negligible. As part of a larger ongoing study investigating the behavior of FRP strengthening systems under fire exposure, an investigation was set up to examine and document the performance of six full-scale near-surface mounted (NSM) FRP-reinforced concrete beams exposed to 1h of fire. All the specimens were preloaded to the service load of the strengthened member. Tests results indicated that, if appropriately insulated, the NSM FRP-strengthened beams can achieve a satisfactory fire endurance of 1h as per fire resistance test specifications. Moreover, this paper also presents a study on the residual performance of fire-tested beams. Results of this study suggest that if the insulation system is able to maintain the adhesive temperature at relatively low value ( for the beam configuration in this test program), the FRP concrete bond degradation under fire is limited, and the FRP-strengthened beam can retain a large part (up to 92% in this test program) of its original strength