Flexural behavior of RC beams strengthened with NSM GFRP strips after exposed to high temperatures

The present study investigated the flexural behavior after exposure to high temperature of reinforced concrete beams strengthened with glass fiber reinforced polymer (GFRP) strips. To strengthen the beams, the near surface mounted (NSM) method was used to install the GFRP strips inside concrete substrate. Two different adhesive materials of epoxy and mortar were used to bond the GFRP strips inside the concrete substrate. Two strengthened specimens using the mortar and epoxy, respectively, as adhesive materials were first exposed to fire, and then flexural test was performed. The test results showed that after exposure to high temperature, the GFRP strips using epoxy technique could be beneficial to retaining the flexural strength of the concrete beams. In contrast, after exposure to high temperature, the GFRP strips using mortar technique was beneficial to deformability, rather than flexural strength. Finally, analytical study was performed to predict the failure mode, strength, and deformation of the concrete beams after experiencing high temperature, and the analysis results showed good agreement with the test results.