FRP-Reinforced Concrete-Steel Double-Skin Tubular Coupling Beam Subjected to Reversed Cyclic Loading

A fiber-reinforced polymer (FRP)-reinforced concrete-steel (FRCS) double-skin tube was developed for use as a new type of coupling beam, and its hysteretic shear performance was investigated. Reversed cyclic loading experiments were performed using five full-sized coupling beams. The FRCS coupling beams had high shear capacities and energy dissipation capabilities, which were attributed to the confining effects of the FRP and steel tubes. Steel stirrups contributed negligible shear capacity. Most increases in the ductility and shear capacity were contributed by the FRP and steel tubes, respectively. The double-skin tube and dual arrangement of the coupling beam decreased the shear deformation and changed the failure mode from brittle shear to ductile concrete crushing. A finite-element model was developed based on the open system for earthquake engineering simulation system. The results of the validation indicate that the model can accurately predict the hysteretic behavior of the FRCS coupling beam. Results of a subsequent parametric study indicate that by increasing the FRP and steel tube thicknesses it is possible to postpone the decrease in shear capacity effectively.