The load bearing capacity, global ductility and overall stability of steel frame can be improved significantly through the use of buckling-restrained braces (BRBs). Based on the open resource platform OpenSees, finite element models of two types of steel frame buildings, one is nine story steel frame (SF) building and another is buckling-restrained braced steel frames (BRBFs) buildings are developed. The structures were analyzed using both deterministic and probability analysis approach. No component-removal random incremental dynamic analysis (IDA) and component-removal random IDA are used to analyze collapse resistance of the buildings under seismic load. The collapse modes of SF and BRBFs under earthquakes are discovered. The nonlinear dynamic responses of SF and BRBFs are analyzed before and after the removal of certain critical components using the alternative path method (APM) approach stipulated by GSA and vertical IDA method respectively. Correspondently, the probabilistic fragility function of collapse likelihood of SF and BRBFs are also derived based on random vertical incremental dynamics analysis approach. The analytical results show that the use of buckling-restrained braces ensures alternative load path, therefore changes the failure modes and improve collapse resistance of structures.
