Effect of fire insulation delamination on structural performance of steel structures during fire following an earthquake or an explosion

In this article a numerical model is presented for simulating fire performance of steel structures following an earthquake or an explosion event. In particular, effect of fire insulation delamination during seismic and blast loading on fire performance of structural members is studied. The extent of delamination of fire insulation over the structural elements is adopted from previous fracture mechanics-based studies. A sequential thermal-structural analysis is carried out to trace the fire performance of beam-column assembly in a moment-resisting frame and a beam-column member supporting heavy axial loads. Results from the analyses clearly show that consequence of delamination of fire insulation from plastic hinge region developed in the beam near the column can be quite substantial.As such, 25% delamination of fire insulation can reduce failure time from 100 min to 64 min. The lack of full fire insulation over this region can significantly accelerate the progressive collapse of the moment-resisting frame due to development of flexural and shear failure in beams adjacent to columns. Also, results from post-explosion fire analysis demonstrate that detachment of fire insulation from a steel column under blast overpressure can significantly impair structural stability of columns during fire following blast.The beam-column that undergoes fire insulation delamination up to 25%, experiences earlier loss of capacity around 85 min as compared to 120 min achieved in case of no delamination of fire insulation.