Dynamic responses and residual capacity of high-strength CFST members subjected to axial impact

Impact is one of the main accidental actions that should be considered; high-strength concrete-filled steel tubular (HSCFST) members are mainly served as the main piers of high-rise buildings, large-span bridges, and defense structures. Hence, this study systematically investigated dynamic responses and residual capacity of HSCFST members subjected to axial impact. A total of six square HSCFST columns were tested, including testing groups with high-strength steel Q690 and a control group using normal-strength steel Q355. Results showed that as the impact energy increased, the local buckling of the steel tube became more severe, and the impact force, time duration, maximum axial displacement, and residual deformation were also enlarged; the residual capacity and residual rate were reduced. High-strength steel significantly improves the axial impact resistance and residual capacity. However, the increment of residual capacity by using high-strength steel was relatively small owing to the severe local buckling of steel tubes. Furthermore, the application range of developed equations for predicting maximum displacement of CFST members subjected to axial impact has been extended to high-strength steels (i. e., up to Q690), and together with the axial displacement limits (i.e., 1/100 L), these equations can be employed as a simplified method for anti-impact design.