Concrete filled double skin steel tubular columns subjected to non-uniform heating

The concrete filled double skin steel tubular (CFDST) columns have been widely used due to their high strength and good deformability. In the past decade, research was performed on the reliability of CFDST columns subjected to standard heating condition, however, only limited works were conducted on the fire resistance of CFDST columns under non-uniform heating. In the current study, a sequentially coupled thermal-stress finite element analysis was performed and the fire resistance of CFDST columns subjected to non-uniform heating was analyzed. Parametric study was performed on the effects of key engineering parameters affecting the column reliability. An extended Rankine approach was developed to predict the ultimate bearing capacity of CFDST columns under non-uniform heating. The theoretical predictions were compared with the numerical analysis, which shows the proposed interaction approach can predict the fire resistance of CFDST columns subjected to non-uniform heating with reasonable accuracy.