Impact resistance of concrete-filled steel tubular members under long-term loading

In order to study the influence of long-term loading on the impact resistance of concrete-filled steel tubular (CFST) members, a finite element analysis (FEA) model was developed by using the software ABAQUS, which embeds the coupling analysis of long-term loading and lateral impact loading, along with the calculation of the residual compressive strength after impacting. The developed FEA models were verified by three tests. Based on the proposed method, the dynamic response of the CFST members under long-term loading was compared with that under primary loading. The residual compressive strength coefficient was used to quantitatively compare the residual compressive strength of the CFST members under those two loading modes and the influences of the steel ratio, steel yield strength, concrete strength, long-term loading ratio, slenderness ratio on the residual compressive strength coefficient were investigated as well. The results from the FEA show that compared with the primary loading mode, when considering the long-term loading, the peak and plateau values of the impact force decrease, the mid-span displacement increases, but the works done by the impact forces under two circumstances are equal. The work done by the axial load is more than that of the primary loading mode when the long-term loading is included, the excess work is mainly dissipated due to plastic deformation of the steel and the concrete has little contribution to the energy dissipation. At the same condition, the members that can continue to bear loads under the primary loading may lose their bearing capacity when considering the long-term loading. According to the parametric analysis, increasing the steel ratio and steel yield strength, and reducing the long-term loading ratio can effectively reduce the adverse effects of the long-term loading on the anti-impact performance of the members, with the increase of the slenderness ratio, the long-term loading will bring more adverse effects on the anti-impact performance of the members, the concrete strength has little effects on the impact resistance of the CFST members. © 2021, Editorial Staff of EXPLOSION AND SHOCK WAVES. All right reserved.