Fire Resistance Performance of Concrete-Filled Steel Tube RC Square Columns under Axial Loading

In order to research the fire resistance performance of concrete-filled steel tube reinforced concrete (CFSTRC) square columns under axial loading, fire resistance tests of four CFSTRC square columns subjected to axial load were conducted. The effects of axial loading level, steel tube area ratio and side length of cross section on the fire resistance performance were discussed by numerical simulations. The research results show that axial expansion deformations of CFSTRC square columns increase and their axial compression deformations decrease with minishing of axial loading level and raisings of steel tube area ratio and side length of cross section under fire exposure. Under the same elevated temperature curve and fire exposure time, a large side length of cross section will result in low temperature inside the square columns, and steel tube area ratio has a slight influence on the temperature distribution of CFSTRC square columns. Axial loading level, side length of cross section and slenderness ratio have great effects on the fire resistance performance of CFSTRC square columns under axial loading, while steel tube area ratio, reinforcement ratio and material strength have a slight influence on the fire resistance performance.