Fires being the cause of collapse of steel frame office buildings

The purpose of our submission is to investigate the extent to which present-day design of steel framed buildings are susceptible to total collapse when subjected to extreme fire events. We select a 50 storey structure in which 2 and 4 adjacent storeys located at different above-ground heights are, in separate scenarios, engulfed in raging fires. A total of 8 scenarios are analyzed, employing Newtonian mechanics and realistic energy dissipating properties of H-shaped columns and normal concrete floor slabs possessing secondary (shrinkage and temperature) reinforcement alone. The present Canadian building code is the basis for our column designs under loading conditions for which gravity loads control. Other attributes which would in practice participate in absorbing the kinetic energy of a crush-down upper block are excluded. Despite such conservative assumptions, it is shown that while partial collapse might indeed occur, there is no scenario that predicts a total collapse. These results should provide some comfort to code writers that present requirements to prevent the most catastrophic of failures due to fires, and might indeed suggest to fleeing occupants alternative routes to safety instead of the desperation cases of window jumpers noted during the WTC fire events 16+ years ago.