The analysis on fire-resistance design of concrete filled double skin steel tubes column section

Comprehensively considering boundary conditions of heat conduction and different thermal properties of steel and normal concrete,the two-dimensional analysis-calculation model of concrete filled double skin steel tubes column section is established with the finite element method and the temperature of different node every moment was obtained.The stress of steel and concrete in certain temperatures can be concluded by using constitutive relation between steel and concrete on high temperature and the internal forces of CFDST(concrete filled double skin steel tubes) combination structure column section can be concluded by using superposition principle.The results show that the fire resistance of components would be good by using this kind of steel.The concrete composite structure column section whose temperature of external steel tube is higher than concrete and inernal steel tube and the primary influencing factors of fire resistance are slenderness ratio,strength of internal and external steel tubes and concrete and hollow ratio.