Impact resistance and simplified evaluation method for square CFST members subjected to transverse impact

Abstract

Recently, the impact behavior and anti-impact design of concrete-filled steel tubes (CFSTs) have attracted increasing attention; the existing analytical theories have mainly focused on equivalent static methods. Thus, this study presents numerical and analytical analyses of simplified evaluation methods for square CFST members subjected to transverse impacts, by adopting dynamic impact action (i.e., impact mass and impact velocity) to evaluate the impact resistance. A finite element model was first established and benchmarked based on 38 test results collected from existing studies with a wide range of test parameters. The impact process, distribution and development of the internal force, and development of the stress, strain, and strain rate were comprehensively analyzed. The dynamic overall buckling of the CFST members under coupling actions of the axial load and transverse impact was investigated and compared with the control groups for CFST members without an axial load. Based on the parametric analyses, the yield strength of steel, section width, steel ratio, and axial load level (n) are important factors affecting the impact resistance. A simplified formula was therefore proposed to evaluate the impact resistance of CFST members with n ≤ 0.5. A machine learning method was also employed to predict the impact resistance of CFST members covering a wider range of axial load levels (n ≤ 0.9).