Fire Endurance and Residual Strength of Insulated Concrete Beams Strengthened with Near-Surface Mounted Reinforcement

Abstract

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 1 h 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 1 h 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 (tadhesive≤1.6tg 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.