Experimental and Analytical Study on Concrete Beams Reinforced with Hybrid Reinforcement under Static and Impact Loads

Traditional steel-reinforced concrete structures face steel corrosion problems in marine and offshore environments, which deteriorate the safety and durability of concrete structures. Stainless steel and fiber-reinforced polymer (FRP) bars are corrosion resistant and are promising in application in coastal and offshore engineering. This combination addresses two critical challenges in marine engineering, namely the chloride-induced corrosion of conventional steel in seawater–sea sand concrete (SSC), and the low ductility and energy dissipation of FRP solely reinforced systems under impact loads. This study aims to systematically investigate the dynamic impact resistance of stainless steel and glass fiber–reinforced polymer (GFRP) hybrid reinforcement in SSC. Twelve beams were fabricated for testing, including two beams reinforced solely with GFRP rebars and ten beams with hybrid reinforcement of stainless steel and GFRP bars. Research findings indicate that the impact resistance of hybrid-reinforced beams is superior to that of GFRP-reinforced beams. This study systematically analyzes the effects of impact velocity, impact energy, and reinforcement area ratio Af/As on failure modes, peak impact force, peak reaction force, maximum midspan deflection, residual deflection, deformation energy dissipation capacity of hybrid-reinforced beams. It employs two energy dissipation metrics (Wf/Wt and Wf/EI) to systematically reveal the deformation energy dissipation mechanisms of stainless steel-GFRP hybrid-reinforced beams under impact loading and their quantitative relationship with the reinforcement area ratio (Af/As). This study provides experimental data and reference for the impact resistance design of concrete beams with hybrid corrosion resistant reinforcement.