Strengthening RC beams using externally bonded CFRP sheets with end self-locking

When laminates of fiber reinforced polymer (FRP) are just bonded on the substrate of reinforced concrete (RC) members for strengthening, debonding failure often happens prematurely and suddenly on the FRP-concrete joints. It is unbeneficial to efficient employment of FRP and reliable service of the structures. This paper introduces a mixed anchoring technique for FRP sheets that combines external bonding (EB) and a novel type of end anchorage. FRP sheets are self-locked at ends by wrapping about a slotted plate in a specified way. Experiments on four concrete beams demonstrated that adding end self-locking to EB can effectively solve the serious problems of usual debonding. End debonding was simply prohibited and intermediate crack debonding was substantially restricted despite occurrence. As a result, not only ultimate strength but also failure ductility of the strengthened specimens was greatly enhanced. The final failure featured by either FRP rupture or concrete crush regardless of debonding degree. Finite element models are then established to simulate the responses of the strengthened beams with hybrid anchored FRP. The numerical results show good agreements with the test observations including debonding process and failure modes. It proves capability and accuracy of the modeling as a useful tool for further research.