Experimental investigation on cantilever square CFST columns under lateral continuous impact loads

Concrete-filled steel tube (CFST) columns can be used in passive flexible protective engineering to improve the bearing capacity of the overall protective system. This paper conducted the lateral continuous impact resistance of cantilever square weathering concrete-filled steel tube (WCFST) columns and compared it with that of the normal CFST. Considering the effect of steel tube wall thickness and prestress on the lateral impact resistance of such components, a total of 10 specimens were subjected to impact tests. The damage form and failure mode of each member were studied in detail, and the effects of the different impact mass and the height of the impact point were considered. The dynamic strain, displacement, and acceleration of each member under different impact loads were analyzed and compared. It was found that tested members show local damage at the impact point, bent failure through whole members, and bulged or fractured at the root. Slippage occurs between the internal concrete and the steel pipe wall of the member without prestressing, and this phenomenon always occurred at the second impact. Results show that when the height of the impact point of members is 0.30 h, the position of the peak displacement point is 0.76 h, where h stands for column height. The application of prestressing can significantly reduce the dynamic strain, displacement, and acceleration of members. Under the same circumstances, applying to the prestress of cantilever members can control the final deformation of it more than increasing the wall thickness. Moreover, the smaller the wall thickness of the component, the better the effect of applying to prestress to control the plastic displacement. The final cumulative plastic displacement of the member is positively correlated with its stiffness degradation after each impact.