Behavior of a 60-year-old Reinforced Concrete Box Beam Strengthened with Basalt Fiber-reinforced Polymers Using Steel Plate Anchorage

In the past twenty years, fiber-reinforced polymer (FRP) has been utilized broadly to strengthen concrete structures for its superiority. The influence of FRP and end anchorage with FRP U-strips or grooving on the behaviors of reinforced concrete (RC) beams has been investigated. However, investigations on the influence of basalt FRP (BFRP) and steel plates on the behaviors of strengthened RC beams remain lacking, especially under the circumstances that the RC beams are full-scale and cracked. The present study investigated the influence of BFRP and steel plates on the behaviors of full-scale cracked RC beams including failure mode, load-carrying capacity, stress-strain relationship and stiffness. Test results demonstrated that: (1) BFRP improved the behaviors of full-scale cracked RC beams from multiple angles; (2) the steel plates had a better effect on restricting the development of cracks and increasing the load-carrying capacity of full-scale cracked RC beams than FRP U-strips; (3) the calculation method considering the influence of FRP debonding was proved effectively to obtain the theoretical load-carrying capacity of BFRP-strengthened RC beams anchoring with steel plates; (4) the steel plates could postpone the development of BFRP debonding at the initial stage, and delay the further propagation of the debonding.