Performance analysis and macromodel simulation of steel frame structures with beam-column joints using cast steel stiffeners for progressive collapse prevention

Progressive collapse is an important failure mechanism that must be considered in the design of critical and essential buildings. For steel moment structures, beam-column joints, which act as transportation hubs of forces, are crucial members to resist progressive collapse. This research investigated the effectiveness of beam-column joints with cast steel stiffeners (CSS) in steel moment frames for progressive collapse resistance. A computationally efficient macromodel that can be used for routine design of steel moment frame buildings with CSS was developed in this paper. The developed model, which considers the deformation of joints with CSS and the catenary action effects during progressive collapse, was validated using a 3D solid finite-element model. Subsequently, the macromodel was utilized to calculate the proper dynamic increase factor for steel moment frame structures with beam-column joints using CSS. The results show that the frame with CSS is less vulnerable to gravity-induced progressive collapse than frames with welded beam-column joints without stiffeners. The proposed macromodel is effective and a dynamic increase factor of 1.6 is suitable for dynamic progressive collapse analysis of steel moment frame structures using beam-column joints with CSS.