Investigating Progressive Collapse Resistance of Setback Irregular Steel Frames Designed for Different Seismic Hazard Levels

Abstract

Column removal in structures can rapidly result in progressive collapse. While the progressive collapse response of regular structures has received much attention in the current literature, relatively, rare studies has been performed on the response of setback irregular structures under column removal scenarios. In this vein, this study analyzes 60 setback steel moment resisting frames, considering ductility levels, design earthquake level, and number of stories. First, structures are subjected to gravity loading and column removal scenarios leading to damage percentage calculation and categorization into different groups from almost fully progressive collapse resistant to highly vulnerable. Results indicate a significant impact of the ductility level and design earthquake level on the probability of progressive collapse. The results also indicate that an increase in the irregularity of the structures will reduce progressive collapse resistance. Yet, the irregular structures with low setback irregularity perform better than regular structures. As well, the results indicate that column removal scenarios in upper stories can increase the risk of progressive collapse due to weak design regulations. To mitigate the risk of progressive collapse in setback irregular structures, it is then suggested that the design parameters such as minimum beam dimensions, minimum base shear, the ductility level and design earthquake level should be changed as per the damage percentage.