Reinforced concrete beams externally strengthened by CFRP rods with steel plate, anchorage bolts, and concrete jacketing

Abstract

This study proposed a new scheme for the retrofitting of Reinforced Concrete (RC) beams using Carbon Fiber Reinforced (CFRP) rods restrained using steel plates and anchorage bolts called the mechanical anchorage system (MAS). This system also employed an external concrete jacket to cover the MAS and CFRP rods. The performance of the proposed technique was experimentally assessed using the four-point flexural testing of retrofitted beams under incremental cyclic load using a dynamic actuator. A total of eight beams were cast and tested in different configurations to determine the effectiveness of the design parameters including the number of CFRP rods, the contribution of MAS, and concrete jacketing (CJ) in terms of load capacity, cracking, failure mode, and ductility. The results revealed that the efficiency of the proposed retrofitting system was achieved by increasing the load capacity of retrofitted beams and preventing the premature debonding failure of CFRP rods. Although de-bonding can occur on the surface between the old and new concrete, the utilization of a perfect adhesive epoxy on the concrete contact surface led to sufficient bonding between the two surfaces. Therefore, overall, the proposed strengthening technique can be considered a reliable method to enhance the performance of RC beams without the risk of de-bonding.