Post-earthquake progressive collapse behavior of steel frames with reduced beam section connections

Beam-to-column seismic moment connections play an important role in the stability of structures during events such as earthquakes or progressive collapse. A key strategy for preventing brittle fractures in these connections is the use of seismic fuses, such as the reduced beam section connection (RBS). While investigating the progressive collapse strength of these connections has been a demanding subject for many years, few studies have been performed on the post-earthquake progressive collapse behaviors of these connections. Therefore, this study investigates the behavior of steel moment frame structures with RBS connections against post-earthquake collapse. To evaluate, 17 structures with rigid and RBS connections are considered, in compliance with seismic design principles, the number of floors, behavior factors, and different seismicity levels. Following the application of 11 records with varying specifications, the behavior of structures subjected to column removal is analyzed. The evaluation of the structure's behavior is based on the nodal vertical displacement of the removed column and the ductility demand of the connections. The structures with RBS connections show a maximum performance level of IO-LS in the plastic hinges, meeting the acceptance criteria of regulations, despite the higher demands. In the seismic design of structures, the type of connection, seismicity of the area, and ductility level of the moment frame play a crucial role in enhancing resistance against post-earthquake progressive collapse. Implementing ductile detailing, like a special moment frame with RBS connections in high seismicity areas, activates the highest robustness of structures in post-earthquake column removal scenarios. However, using precise seismic detailing in structures located in moderate seismicity increased the ductility demands and nodal vertical displacements by up to around 60 and 3.0 times, respectively.