A new design method of the equivalent stress-strain relationship for hybrid (FRP bar and steel bar) reinforced concrete beams

Abstract Hybrid reinforced concrete (hybrid-RC) beams consisting of fiber-reinforced polymer (FRP) bars and steel bars can provide high strength, serviceability, and durability. However, based on a review of the literature, the design methods for hybrid-RC beams fail to effectively predict the flexural failure mode of these structures. Therefore, an equivalent constitutive relationship is proposed, which considers the FRP bar and steel bar as a new material with a bilinear constitutive relationship. Two balanced reinforcement ratios were introduced in the design method, which can accurately predict the failure mode of both the hybrid-RC structure and FRP strengthened RC structure. The feasibility of the proposed method was then confirmed by experimental testing.