Dynamic progressive collapse of steel moment frames under different fire scenarios

Dynamic mechanisms for progressive collapse of steel moment-resisting frames are studied under different durations of a column removal due to different fire scenarios. Development process of natural fire and gas temperature are modeled and predicted by software fire dynamics simulator (FDS). The steel temperature is then predicted reliably using the method recommended by EN19993–1-2 incorporating the predicted gas temperature by FDS. Steel frames and columns exposed to fire are simulated by BEAM188 in ANSYS with APDL and then validated against experimental data obtained from other researchers. It can be found that the failure duration of a column is different under standard and natural fire conditions, similarly under different boundary conditions, namely, axial load, initial imperfection, axial restraint stiffness ratio and rotational restraint stiffness. Finally, a step-by-step analysis procedure is established using SAP2000 API with Excel VBA to determine structural response versus duration of a column failure. The decay trend of maximum displacement can be described quantitatively by a one-phase exponential decay function, which is drawn after extensive analysis of dynamic response for different structures with various spans, member sections, loads, levels of a building and total number of floors