Eccentric compression behaviour of circular steel tube confined steel-reinforced concrete columns exposed to fire

Steel tube confined steel-reinforced concrete (STCSRC) columns have been used in high-rise and large-span structures. However, current research on the mechanical behaviour of STCSRC columns under fire conditions is still scarce, and the stress distribution and failure mechanisms of the column exposed to fire remain inadequately unclear. Consequently, a sequentially coupled thermal stress analysis model was developed in this study, and two specimens with different load eccentricities were tested to validate the reliability of the finite element (FE) model. Related fire resistance tests conducted by other researchers were also used to verify that the created FE analysis model can precisely simulate the fire performance of circular STCSRC columns subjected to eccentric loads. Subsequently, the mechanism analysis of columns was carried out, including the load sharing ratio of each component, the stress distribution of concrete, and the axial stress development of the steel section. Then, an extensive parametric analysis of the fire resistance of circular steel tube confined steel-reinforced concrete columns subjected to eccentric loads was conducted. Finally, calculation formulas for assessing the high-temperature load-bearing capability of STCSRC columns under eccentric compression were proposed.