Flexural Performance and Deflection Prediction of Rectangular FRP-Tube Beams Fully or Partially Filled with Reinforced Concrete

Sixteen full-scale concrete-filled fiber-reinforced polymer (FRP) tube (CFFT) rectangular beams, 3,200 mm long and $305\times 406{\mathrm{mm}}^2$ cross section, with steel reinforcement at the tension side have been tested under a four-point bending load. Some CFFT beams were partially filled with concrete by providing inner hollow FRP tubes inside the section at the tension zone. Several test parameters were studied such as the tube thickness, fiber laminates, and section configurations. The experimental results indicate outstanding performance of the steel-reinforced CFFT rectangular beams in terms of strength and deformability compared to conventional reinforced concrete (RC) beams. The inner hollow FRP tubes inside the CFFT beams acted positively in reinforcing the section and confining the concrete in the compression zone. Theoretical analysis was developed based on the experimental results to verify the applicability of North American codes to predict the deflection of rectangular CFFT beams. Based on this study, new equations and assumptions were introduced to Branson’s equation to predict accurately the effective moment of inertia of steel-reinforced CFFT rectangular beams at the preyielding stage as well as the postyielding stage.