Experimental study on seismic performance of GFRP and highly ductile stainless steel hybrid reinforced concrete columns

Abstract

To enhance the deformation and energy dissipation capacities of FRP-reinforced concrete structures, this study explores the seismic behavior of seawater and sea sand concrete (SSC) columns reinforced hybrid with GFRP and high ductile stainless steel. It involved designing seven hybrid-reinforced column specimens and one GFRP-reinforced specimen, followed by low-cycle reversed loading tests. This study analyzed the impact of the reinforcement ratio of stainless steel (SS) bars to GFRP bars (ρss/ρGFRP) and the axial compression ratio (μN) on the seismic performances including failure modes, hysteresis curves, load-lateral drift ratio envelope curves, ductility, energy dissipation, residual displacement, and stiffness degradation. Experimental findings indicated that at an axial compression ratio of 0.1, the failure mode of the hybrid-reinforced specimens was primarily governed by flexural-shear behavior. Initially, the specimens exhibited a flexural response up to the yielding displacement but ultimately failed in shear. Compared to columns reinforced only with GFRP, the hysteresis curves of the hybrid-reinforced specimens were significantly fuller, suggesting superior ductility and energy dissipation capacities of the latter. As the ratio of stainless steel to GFRP reinforcement decreased and the axial compression ratio increased, the specimens displayed more pronounced shear failure characteristics. Additionally, the results showed that GFRP longitudinal reinforcement underwent shear fracture or partial fiber rupture due to the combined effects of shear deformation within the core concrete and the confinement provided by stirrups, leading to shear failure of the core concrete. Overall, the findings demonstrate that hybrid-reinforced concrete columns possess enhanced seismic performance relative to those reinforced only with GFRP bars.