Bond strength of near surface-mounted FRP plate for retrofit of concrete structures

Recently, Fiber Reinforced Polymer (FRP) has been widely applied in retrofit of concrete member owing to its ease construction and high structural capacity compared to other materials. Externally Bonded Retrofit (EBR) using FRP sheet or plate is most popular method for flexural retrofit of concrete member. In strengthened concrete member using this method, however, problems such as dismantling of FRP were founded after retrofit. This causes a strength reduction of the retrofitted member. To resolve this problem, Near Surface-Mounted Retrofit (NSMR) method was developed and has been being studied. In this paper, bond capacities of EBR and NSMR using FRP plate were studied experimentally and results were compared each other. Also the variation of bond strength of NSM FRP plate was evaluated according to bonded length as well as number of shear key. From the test results, it was found that the member strengthened by NSMR had almost 1.5 times higher bond strength than that by EBR. The contribution of shear key was not observed when the split failure of concrete governed.