Seismic degradation behavior of steel-FRP composite bar reinforced concrete beams in marine environment based on experimental and numerical investigation

This study investigated the seismic behavior of seawater sea sand concrete (SWSSC, which is made of seawater, sea sand, ordinary aggregate and cement) beams reinforced with steel bars in a marine environment. To improve the durability of the specimens, different types of reinforcements, namely fiber reinforced polymer (FRP), steel -FRP composite bars (SFCBs), and macro basalt fibers, were introduced to replace steel bars owing to their su-perior durability and high strength. The failure mode, hysteretic response, energy dissipation capacity, and curvature of the pedestal were analyzed. Furthermore, a long-term performance prediction method based on finite element (FE) modeling was proposed. Results showed that the bond between the longitudinal re-inforcements and SWSSC in steel and SFCB reinforced concrete (RC) beams degraded significantly after corro-sion. Additionally, slips were observed during reciprocating loading. The total cumulative dissipated energy of the SFCB RC beam was approximately the same as that of the steel RC beam. Moreover, the corresponding value of SFCB and macro basalt fiber hybrid reinforced concrete specimen was almost twice that of the steel RC beam owing to a stable confinement of fibers on concrete. After corrosion, steel and SFCB RC beams exhibited a decrease in the lateral displacement at the top and a larger curvature at the pedestal, indicating that the rotation of the corroded specimens mainly occurred at the beam-column joint. The accuracy of the FE model was verified by comparing the obtained results with the experimental results. The prediction results revealed that the seismic performance of SFCB RC beams in the marine environment declined in the first three years and then stabilized gradually.which is made of seawater, sea sand, ordinary stone and cement.