SEISMIC PROGRESSIVE COLLAPSE ANALYSIS OF CONTROLLED STEEL FRAME STRUCTURES

Any element loss in the concentrically-braced frames (CBF) system significantly affects its seismic performance. The research presented in this paper aimed to understand the behavior of this system against seismic progressive collapse due to the failure of a column. A collapse of this magnitude may lead to the entire collapse of the structure, or else it could avoid or even localize the disaster by redistributing the released load to the surrounding structure. The progressive collapse phenomenon was investigated through analyzing a building equipped with CBF system during a seismic event. Four cases of failed beams were considered, depending on the location of the column loss and the configuration of the braces surrounding them. Through OpenSees simulation, the results showed the seismic and gravity loads increased and rapidly reached the ultimate state of the structure from 0.6 sec after the time of failure. The model for each scenario, regardless of the direct collapse of the structure due to the column loss, indicated the CBF system limited the plastic hinge formation around the failed element. Finally, the results showed the braces working in tensile are more reliable in terms of collapse resistance than those working in compression.