Evaluating the effect of 3D sandwich infill panels on the progressive collapse potential of steel structures with extensive initial damage

Studying the potential of progressive collapse in structures is a new topic in the field of passive defense and has attracted the attention of many researchers, recently. This research investigates the behavior of steel structures with 3D sandwich infill panels after extensive damage. For this purpose, several moment resisting steel frames with different numbers of stories and span length to story height ratios are investigated. The steel frames have infill panels with 30, 50 and 100% of openings, and the initial widespread damage scenarios are consisted of removing 2 and 3 columns with their adjacent infill panels. The results show that the presence of the infill panel reduces the ductility of the structure by increasing the stiffness and prevents the extra rotation of the structural elements, significantly. On the other hand, infill panels can reduce the potential of progressive collapse by increasing the continuity and participating in transferring the extra load. According to the results, the frames without infill panels do not withstand the scenario of progressive collapse in extensive initial damage, however, infill panels help the 6 and 9-story studied structures survive regardless of their span length to story height ratios.