Seismic Performance and Buckling Length Calculation Method of Concrete-Filled Steel Tube Columns

This study establishes a refined numerical model of circular concrete-filled steel tube (CFST) columns using finite element software, and its effectiveness was verified through simulation of low-cycle reciprocating load tests. Based on this, a systematic analysis was conducted to investigate the effects of three key parameters—axial compression ratio (0.1–0.3), slenderness ratio (22.2–46.8), and confinement coefficient (0.65–1.56)—on the seismic performance of CFST columns, including failure modes, hysteretic behavior, skeleton curves, ductility, and energy dissipation capacity. The local buckling behavior was also studied. The results indicate that increasing the axial compression ratio slightly enhances the bearing capacity but reduces ductility, increasing the slenderness ratio significantly reduces the bearing capacity but improves ductility, and increasing the confinement coefficient substantially improves the bearing capacity, ductility, and energy dissipation capacity simultaneously. Based on the parametric analysis, the existing calculation formula for the local buckling length of circular CFST columns was modified. The average error between the predicted and simulated values is only 10%, demonstrating high engineering applicability. This research provides a theoretical basis and a practical calculation method for the seismic design and performance evaluation of CFST building and bridge columns.