Residual Load-Carrying Capacity of Hybrid FRP-UHPC-Steel Double-Skin Tubular Column after Lateral Impact

The hybrid fiber-reinforced polymer (FRP)-concrete-steel double-skin tubular column (DSTC) is an innovative composite member consisting of an outer FRP tube and an inner steel tube, with the space between them filled with concrete. The incorporation of ultrahigh-performance concrete (UHPC) in the DSTC yields numerous advantages over the DSTC with normal-strength concrete, particularly in terms of enhanced impact resistance. While the lateral impact behavior of UHPC DSTC has been investigated, its residual performance after lateral impact remains unexplored. To comprehend the postimpact behavior of UHPC DSTC, a series of specimens underwent lateral impact, followed by static axial compression. Additionally, intact specimens were subjected to static axial compression for comparative analysis. Subsequently, refined numerical models were developed and validated using the obtained test data. Detailed parametric studies were carried out to investigate the influences of key variables on the postimpact behavior of UHPC DSTCs. Finally, based on the ratio of residual midheight deflection to the column height, a prediction formula was proposed for the rapid damage evaluation of impacted UHPC DSTCs, and threshold values for different damage levels were suggested based on a defined damage index.