Comparison of progressive collapse resistance capacities of steel ordinary and intermediate moment frames considering different connection details

In this study, the progressive collapse resistance capacities of steel ordinary moment frames (OMFs) and intermediate moment frames (IMFs) with different connection details were numerically evaluated and compared. Three prototype buildings with typical configurations were designed in accordance with Korean building code (KBC). OMFs with welded unreinforced flange-bolted web (WUF-B) connections, OMFs with reduced beam section (RBS) ones, and IMFs with RBS ones were deployed for each building. Beams, columns, connections, and composite slabs were modeled using reduced models of 1-D and 2-D elements for efficient analyses. With respect to progressive collapse analyses, 1- and 2-column removal scenarios were firstly performed through non-linear static analyses and then the numerical results were employed for the energy-based approximate analyses, resulting in load-displacement relationships reflecting dynamic effects due to the sudden column removals without highly time-consuming dynamic analyses. The comparison of progressive collapse resistance capacities was based on the U.S. general services administration (GSA), structural robustness index, and sensitivity index. As a result, all the three buildings met the chord rotation criterion of GSA and indicated enough resistance capacities in the 1-column removal scenario, but not in the 2-column removal scenario. For the OMFs, it was found that the RBS connection showed better resistance capacity than the WUF-B one. Furthermore, the OMFs were superior to the IMFs from the standpoint of resistance capacity. The results can be utilized to predict progressive collapse resistance capacities of similar types of structures.