Research On Impact Resistant Behavior Of Concrete Filled Steel Tube And Confined Concrete Filled Steel Tube Short Columns

Concrete filled steel tube (CFT) are wide used in high-rise and super high-rise buildings because of a series of superior properties. However, research on its impact resistant behavior is still at the beginning stage. In recent years, building structures damaged by the impact occur frequently. Therefore, research on the impact resistance of CFT structures become very necessary. In this paper, the dynamic response and the failure characteristics of CFT and confined concrete filled tube (CCFT) were studied by means of experiments and numerical simulation to fully understand the basic performance and influencing factors.Firstly, CFT and CCFT short columns with two kinds of steel tube wall thickness and layers of carbon fiber were tested under series of height in the axial direction, impact force history, axial deformation history, axial and circumferential strain history of measuring points on steel tube surface and residual deformation of the specimen were measured and obtained final deformation patterns of specimens, a high speed camera was used to record the whole damage process of specimens as well. The relationship between the average axial residual strain and impact energy was obtained. The characteristics of damage occurred in the specimens was analyzed by comparing the final deformation patterns of specimens and failure patterns of core concrete. The effectiveness of steel tube wall thickness, impact energy and carbon fiber constraint to the maximum impact force, axial deformation and strain of steel was discussed. The maximum impact force and average axial residual strain can be caculated by a simplified formula.Secondly, numerical simulation was conducted on the test using finite element analysis software ANSYS/LS-DYNA. The simulated results with experimental results were compared and found good agreement between the two. It verified the simulation results and pointed out the deficiencies in the test, the system energy transfer rules and energy absorption situation of all kinds of materials in the impact process were also discussed in the end.