Flexural Behavior of Innovative Hybrid GFRP-Reinforced Concrete Beams

Fiber-reinforced polymer (FRP) bars are emerging as a competitive option for replacing steel bars as reinforcement in various concrete structures exposed to aggressive environments. However, the low elastic modulus and brittleness of FRP bars significantly reduce the stiffness and the ductility of FRP-reinforced concrete (FRP-RC) members. In order to improve the flexural behavior of FRP-RC members and meanwhile ensure their satisfactory corrosion-resistant performance, an innovative FRP-reinforced concrete encased steel composite (FRP-RCS) member, which consists of ductile structural steel shapes in combination with corrosion-resistant FRPreinforced.concrete, was conceived and studied. An experimental investigation on the flexural behavior of the proposed FRP-RCS beams was conducted by testing a total of five large-scale simply supported beam specimens subjected to four-point bending loads. The test specimens included one FRP-RC beam reinforced with GFRP bars only and four FRP-RCS beams reinforced with both GFRP bars and encased structural steel shapes. The main parameters considered in this study were concrete compressive strength and amounts of GFRP reinforcement. The test results indicated that using encased steel shapes provided a significant enhancement in load carrying capacity, stiffness, ductility and energy absorption capacity of test beams. The tested FRP-RC beam suffered a brittle failure caused by sudden fracture of tensile GFRP bars whereas the proposed FRP-RCS beams behaved in a ductile manner due to the beneficial residual strength of encased steel shapes following concrete crushing. In addition, the experimental results also demonstrated that the concrete compressive strength had little effect on load carrying capacity of FRP-RCS beams whereas the load carrying capacity can be enhanced by increasing the reinforcement ratio. Analytical methods were also constructed using OpenSEES2.2.2 to simulate the load-deflection response of tested beams..