Majid Mohammadi - IIEES
Nima Nasirzadeh - Ayandegan College of Tonekabon
Bahram Kordbagh - IIEES

Progressive collapse is defined as the expansion of local failure which damages the entire structure or a big part of it. The failure created is very widespread compared with the initial event. The effect of debris, which is normally produced during a progressive collapse, has not been studied yet sufficiently. Despite, it is very important in the progressive collapse, based on experimental accidents. In this paper, the response of a building structure is investigated to consider the influence of separation of debris from one story and falling on the bottom floor. Nonlinear dynamic analyses have been performed on a four-story, four-span steel frame. A sensitivity analysis on the debris amount and its detachment time is carried out by OpenSEES. The obtained results indicate that the greater amount of debris leads to more intensive progressive collapse. In the case of detachment time, the most damaging effect occurs if debris is separated at the same moment when the top point of the removed column experiences its most vertical displacement. Debris amplifies the maximum and residual displacement of the top point of the deleted column up to ۳.۶۵ and ۴ times, respectively. This shows that debris has a considerable effect and cannot be ignored in progressive collapse analyses.

Progressive Collapse, Debris, Collision, Moment-resisting frame