Vulnerability of Three-Dimensional Semirigid Composite Frame Subjected to Progressive Collapse

AbstractLimited studies have investigated the progressive collapse of three-dimensional (3D) semirigid steel–concrete frames due to the complexity of modeling techniques, intensive computational time involved in the analysis, and lack of experimental work. A simplified numerical model was developed using nonlinear dynamic analysis procedures. Single column removal cases were considered in different story levels and at various locations. Results of three different types of connections—double web angle (DWA), top and seat angle with double web angle (TSD), and double-tee angle (T-stub) were compared with those having a rigid joint to highlight the effect of connection rigidity. The analysis results showed that the vulnerability of progressive collapse in the corner column removal scenario on the ground floor for DWA connections is higher than that of other removal situations. Three-dimensional skeleton frames and two-dimensional (2D) frames cannot capture the realistic behavior of the structure under progressive collapse. In consecutive column removal cases, the vulnerability of progressive collapse drastically increases. Finally, the paper presented new retrofitting schemes to improve collapse resistance, which will be useful for researchers and structural designers.