Fire-induced Progressive Collapse of 3D Steel Portal Frames

This paper presents experimental and numerical investigations on progressive collapse of 3D steel portal frames exposed to fire. A natural fire test was carried out on a 36m×12m full-scale steel portal frame. A finite element model is established and validated against the test results. The experimental results show that the frame collapses after 15 mins of heating due to the buckling of the heated columns. It is found that the adjacent frame column at mid-span moves outward, compared to the inward movement of columns at corner. The numerical results show that the fire protection had significant effect on the collapse mode. The protected portal frames show a lateral drift collapse mode, compared to a downward collapse mode for unprotected frames. A higher level of fire protection leads to longer buffer time to delay the collapse of frames.