Fire performance of concrete-filled steel tubular column with encased profile steel under axial compression

The incased profiled steel can effectively improve the bear-capacity and fire performance of the concretefilled steel tubular( CFST) members. This paper presents a thermodynamic coupling finite element( FE) model of concrete-filled steel tubular( CFST) column with encased profiled steel to study the fire performance under axial compression using the ABAQUS software. The numerical results of steel reinforce concrete( SRC) and CFST members match well with the other researchers' experimental results. Based on the FE model,the relationships of axial displacement to time and mid-span deflection to time of the mombers were calculated when they expose to fire. The whole fire stage includes three phases according to the failure modes,such as initial expending stage,compression stage and failure stage. The fire resistance limit of the CFST columns with encased profiled steel was calculated for ISO834 standard fire. Finally the interaction forces between the components were calculated and the paramenter analyses were carried out. The results show that the contact stresses between steel column and concrete and between concret and profile steel decrease with increase of temperature. The fire load ratio,slenderness ratio of column,the steel rate of tube and thickness of fire protection layer have more significant effects on the fire resistance limit.