Effect of Construction Details on the Bond Performance of NSM FRP Bars in Concrete

Abstract

Near-surface mounted (NSM) fiber-reinforced polymer (FRP) reinforcement has proven effective for strengthening reinforced concrete structures and is gaining increasing attention. The NSM reinforcement is installed by grooving the surface of the member to be strengthened and embedding FRP bars or strips in the grooves with an appropriate binder. This paper reports the results of an investigation designed to evaluate the influence of some construction parameters on the bond performance of NSM FRP round bars. These parameters include the groove depth and width-to-depth ratio, the groove distance from the edge of the member, the mechanical properties of the groove-filling epoxy, and the use of transverse FRP sheets for confinement of the joint. During the tests, conducted with a direct shear setup, the loaded-end and free-end slips and the strain distributions along the reinforcement and in the transverse plane were monitored. Tests were conducted on both short and long NSM bar anchorages. Results are here reported and analyzed to determine the effect of the test variables on local bond-slip behavior and development capacity. The local bond-slip curves obtained from the tests with short bond length are modelled analytically and used to predict the capacity of the specimens having long bond length and the same other test variables.