Experimental study on the seismic behavior of seawater sea sand concrete beams reinforced with steel-FRP composite bars

This study offers a new solution to improve the durability of steel-reinforced seawater sea sand concrete (SWSSC) beams without reducing their energy-dissipation capacity under seismic loads. Thus, an investigation of beams reinforced with steel-FRP composite bars (SFCBs), hybrid reinforced with SFCB bars and basalt fiber reinforced polymer (BFRP) bars was conducted. The effects of incorporating 1% minibar in concrete on the seismic behavior of reinforced concrete (RC) beams were also studied. These behaviors included the failure mode, hysteretic response, stiffness degradation, energy-dissipation capacity, strain variation, and curvature of the pedestal. Results showed that chloride ions in seawater and sea sand concrete caused steel bars to corrode and adversely affected the seismic response of RC beams. In addition, the SFCB bars and hybrid RC beams exhibited a more pronounced pinching effect and smaller residual displacement as compared with the steel RC beams. The total cumulative dissipated energy of the SFCB RC beams was approximately the same as that of the steel bar RC beams due to increased deformation. The seismic behaviors of the SFCB bar reinforced minibar-concrete beams were significantly improved under low cyclic loads due to a stable confinement of minibar on concrete. Their load-carrying capacity and energy consumption increased by 27.0% and 36.5%, respectively, as compared with those of the steel RC beams. Similar improvements could be observed in the response of the lateral load versus curvature in the pedestal relationship. Based on these seismic behaviors, structures reinforced by SFCB bars and hybrid reinforced by SFCB and BFRP bars are recommended as means of reinforcement for seawater and sea sand concrete structures.