Behavior of concrete filled tubes and confined concrete filled tubes under high speed impact

Concrete filled tubular (CFT) columns are being more and more utilized in construction of tall buildings and bridges. Xiao recently developed a new CFT column system, named as confined concrete filled tubes (CCFT), and validated its excellent load carrying capacity and ductility, by static and simulated seismic loading tests. This paper reports the impact behavior of CFT and CCFT stub columns. The impact responses of concrete filled steel tubes (CFT) and the confined concrete filled steel tubes (CCFT) were investigated using a high-speed gas gun. Experimental parameters included the confinement details and impact speed. Dynamic strains and the failure patterns are discussed. The test results demonstrate the effectiveness of lateral confinement to improve the dynamic impact behavior of CFT columns. Comparisons were also made between the test results and the analytical results using LS-DYNA. The trend of the stress wave propagation in the CFT specimen was reasonably well predicted.