Theoretical and numerical analysis to concrete filled double skin steel tubular columns under fire conditions

• A 3D finite element model was developed to simulate the fire performance of CFDST columns.
• Failure mechanism of the CFDST columns was studied based on the developed numerical model.
• Engineering design recommendations were proposed to promote the fire resistance of CFDST columns.
• The conventional Rankine approach was extended to predict the fire resistance of CFDST columns subjected to an axial load.

As one of the recently developed steel–concrete composite structural members, concrete filled double skin tubular (CFDST) columns have been used in current construction industry due to its good structural performance. However, CFDST columns could be vulnerable under fire attack. In the current work, the fire resistance of CFDST columns has been studied. Finite element analysis (FEA) models were developed to investigate the fire resistance of unprotected CFDST columns. The FEA models were verified with experimental data from literature. Based on the developed numerical model, the failure mechanism of CFDST columns under fire conditions were studied and a parameter study was performed on the fire resistance design for CFDST columns. Based on the computational analysis, the conventional Rankine approach was extended to predict fire resistance of CFDST columns. Experimental data were used to validate the accuracy of the proposed method; it shows that the proposed method can predict the fire resistance of CFDST columns with reasonable accuracy compared with experimental data.