Lateral impact test and inertial force of concrete-filled steel tube column

The mechanical behavior of concrete-filled steel tube (CFST) subjected to lateral impact was studied by drop hammer test and finite element method (FEM). Lateral deformation occurred when the midspan of CFST was impacted by a drop weight. Two plastic hinges were formed in the mid-span and near the fixed support, respectively. The numerical and experimental results were compared to ensure that the numerical model was reasonable for investigating the stress development, damage, and inertial force of the CFST column. The effects of the impact velocity, impact mass, cross-sectional steel ratio, and boundary conditions on the inertial force of the CFST column were analyzed. During the impact process, the maximum stress was at the steel tube part of the impact location and the fixed support, while the other parts were still in the elastic or elastoplastic stages. The region under restraint at the fixed end of the CFST column exhibited the first signs of concrete core damage under tension, followed by the region near the location of the impact at midspan. At the peak impact force (Fp), the impact velocity had a considerable influence on the distribution of inertial force of CFST, while the impact mass and cross-sectional steel ratio had no discernible impact on the inertial force at the Fp, and boundary conditions had little impact on the distribution of inertial force. Based on a research of the inertial force at the Fp, a simple mechanical model of the inertial force was built.