Fire resistance of concrete filled steel tube columns subjected to non-uniform heating

Concrete filled steel tube columns have been widely applied in modern construction. However, limited work has been done on the resistance of concrete filled steel tube columns subjected to non-uniform fire conditions, and a calculation method with clear physical meanings is useful to structural engineers. Columns are usually exposed to 1-, 2-, 3-face heating under real fire scenarios. In the current work, a 3D finite element model was developed to simulate the concrete filled steel tube columns exposed to non-uniform fire conditions. After validating the proposed FE model, the failure mechanism of concrete filled steel tube columns under non-uniform fire was discussed. Parametric studies were conducted to investigate the influence of critical structural parameters. A theoretical approach was proposed to calculate the fire resistance of concrete filled steel tube columns exposed to non-uniform heating. By comparing the experimental data and numerical simulations, the developed approach was validated to be sufficiently accurate to predict the ultimate load capacity of concrete filled steel tube columns under 1-, 2-, 3-face heating scenarios.