Post-tension near-surface mounted strengthening system for reinforced concrete beams with changes in concrete condition

The concrete capacity of bridges gradually decreases due to the external environment and aging of the structure. Recently, near-surface mounted (NSM) systems have been studied to reinforce concrete bridges. The NSM system can reinforce existing concrete structures with less labor and without changing its dimensions. The post-tension NSM system was applied to improve the flexural capacity of concrete structures that are damaged due to aging or by the external environment. In this study, 6.4-m reinforced concrete (RC) beam strengthened with a post tension NSM system was fabricated, and a four-point loading experiment was performed. The strengthening effect of the RC beam was investigated experimentally with respect to the initial concrete strength, bonded and unbonded fiber reinforced polymer (FRP) bar, and RC beam damage conditions. This study proposed a finite element (FE) analysis model by simulating the bond behavior of FRP bars and the filler. Parametric study was performed on the bond length of the FRP bar, and pre-stressing was performed using the proposed FE model.