Novel FRP-UHPC-steel double-skin tubular columns subjected to horizontal impact loading: Experimental study and FE modelling

This study explores the impact performance of a novel structural member—FRP-UHPC-steel double-skin tubular columns (U-DSTCs)—which integrates an outer fiber-reinforced polymer (FRP) tube, an inner hollow steel tube, and an ultra-high-performance concrete (UHPC) interlayer. This composite configuration leverages the high corrosion resistance of FRP, the excellent impermeability and high strength of UHPC, and the ductility of steel to produce a resilient structural member suitable for applications such as wind turbine towers and bridge piers in harsh environments. Considering the vulnerability of such infrastructure to accidental impacts from vehicles or vessels, this study investigates the horizontal impact performance of large-scale U-DSTC specimens ( D f = 300 mm, H = 1500 mm) with substantial void ratios ( φ = 0.73 and 0.82) through both experimental testing and finite element (FE) modelling. Results reveal that U-DSTCs predominantly exhibit flexural failure modes, with plastic hinge formation near the fixed base. Peak impact force, average force, and lateral displacement increase with impact velocity, reflecting enhanced energy absorption capacity under more severe loading. Increasing the void ratio reduces local stiffness but enhances global stiffness, improving overall impact resistance. Effects of FRP fiber winding angle and thickness on impact response were found to be limited. Parametric finite element analyses further revealed that impact-induced displacement is more sensitive to impact velocity than to impact height. Among the studied parameters, the influence on impact performance decreases in the order of void ratio, steel yield strength, and FRP tube thickness. • FRP-UHPC-steel double-skin tubular columns (U-DSTCs) were tested under lateral impact loading. • U-DSTC columns show excellent flexural performance and minimal local damage under impact. • A validated finite element model was developed to capture the dynamic response and failure mechanism. • The influence on impact performance decreases in the order of void ratio, steel yield strength, and FRP tube thickness.