Bond enhancement for NSM FRP bars in concrete using different anchorage systems

Studies have shown that the near-surface mounted (NSM) FRP technique provides better bond performance than the externally bonded (EB) FRP method in strengthening applications. However, undesirable intermediate crack-induced debonding failures and end debonding failures are still frequently observed in NSM FRP reinforcements. In this study, the additional ribs (ARs) anchorage system and the wire mesh mortar protection layer (WML) anchorage system were proposed in an attempt to eliminate such premature debonding failures in NSM FRP strengthening system. The testing results of 20 direct pull-out specimens were used to verify the feasibility of the two proposed anchorage systems in improving the bond behaviour of NSM FRP bars. The individual use of the ARs anchorage system and WML anchorage system enhanced the bond strength of the NSM FRP bars up to 40.7% and 69.7%, respectively. The combined use of the two developed anchorage systems was found to be the most effective in increasing the bond performance of the NSM FRP bars, providing a maximum bond enhancement of 114.3%. (C) 2020 Elsevier Ltd. All rights reserved.