Design of ductile H-anchorage for strengthening reinforced concrete beams with prestressed FRP

Abstract Most FRP strengthening methods increased load capacity at the cost of decreased ductility. A review of 551 specimens from 64 literatures shows that the ductility of FRP strengthened RC beams experienced an average decrease of ductility by 37.2%. To achieve balanced improvement of ductility and load capacity, a previously proposed H-anchorage is adopted to prestress FRP laminates and to strengthen reinforced concrete (RC) beams in flexure. A total of ten specimens were cast and tested under four-point bending, the test results are presented and discussed. The effects of concrete strength, bond scheme, and prestress level of FRP were investigated. The H-anchorage was found to improve the utilization of FRP in tension, achieve great increase of load capacity, and maintain satisfactory ductility. Partial bonding of prestressed FRP effectively improved the flexural performance within the elastic range, and the load capacity generally increased with increasing prestress level of FRP laminates. The increase of ductility was more prominent in the specimens using high-strength concrete than those using low-strength concrete. During the loading process, the deformed concrete section remained planar. Based on this observation, an analytical model is proposed to estimate the load capacity, reaching good agreement with the experimental results. Finally, a design method is proposed for optimizing the configuration of H-anchorage to ensure optimum performance in terms of load capacity and ductility.