Seismic Performance of Steel Tube-Reinforced Concrete Columns after Exposure to Fire on Two Adjacent Sides

A nonlinear finite element model has been developed to numerically simulate the hysteretic behavior of steel tube-reinforced concrete columns after exposure to fire on two adjacent faces under reciprocating loads. This model considers various parameters, including fire duration, slenderness ratio, section size, core area ratio, external concrete strength, and reinforcement ratio. The study systematically investigates and analyzes characteristics such as the skeleton curve, ductility coefficient, stiffness degradation, and hysteretic energy dissipation of columns post-fire. Results indicate that member stiffness decreases with increasing displacement loading, and the equivalent viscous damping coefficient of the member escalates with increased horizontal displacement. Moreover, as fire duration and slenderness ratio increase, there is a corresponding decrease in member stiffness, leading to a reduction in the equivalent viscous damping coefficient. In contrast, increases in section size and core area ratio enhance member stiffness and decrease the equivalent viscous damping coefficient. Furthermore, enhancements in external concrete strength and reinforcement ratio elevate member stiffness, which subsequently increases the equivalent viscous damping coefficient.