Experimental and numerical studies of CFRP tube and steel spiral dual-confined concrete composite columns under axial impact loading

Compared with conventional steel spiral reinforced concrete (SRC) or concrete filled fiber reinforced polymer tube (CFFT) columns, the fiber reinforced polymer (FRP) tube and inner steel spiral reinforcement (SR) dual-confined concrete hybrid columns (shortened as FRP-SR-concrete) showed higher load-bearing capacity and ductility in static compressive loading. In literature, very few studies have considered the dynamic behavior of FRP-SR-concrete columns under impact loading when using such hybrid structures under seismic-induced axial dynamic loading. This study investigated the axial impact behavior of carbon FRP-SR-concrete (CFRP-SR-concrete) columns subjected to a drop-weight impact test. The experimental parameters considered were CFRP tube thickness, the SR volumetric ratio, height and the weight of the impact hammer of the drop-weight test. The axial impact resistance of conventional CFFT and SRC columns was further used for a comparison. The test results showed that the CFRP-SR-concrete had higher dynamic impact load and better cracking resistance compared with the SRC or CFFT counterparts. The impact resistance of the CFRP-SR-concrete columns was enhanced with an increase in the CFRP tube thickness and the volumetric ratio of the SR. Additionally, numerical simulation was performed to predict the failure process and the impact resistance of the CFRP-SR-concrete columns.