STRUCTURAL INVESTIGATION OF HEIGHT - IRREGULAR- STEEL BRACED STRUCTURES AGAINST PROGRESSIVE COLLAPSE

Considering failure scenarios caused by a progressive collapse of structural systems subjected to special loadings such as explosion, impact, fire, design error and excessive unexpected loads is one of the main challenges that nowadays structural engineers encounter. Progressive collapse is defined as propagation of local failure of a structural member to other members that ultimately leads to failure of the whole structure or a portion of it. The effect of irregularities and the use of viscous damper in structural behavior of steel braced buildings against progressive collapse is the spotlight of this study. Three different steel buildings (5, 9 and 13 stories) with vertical irregularities are considered and analyzed with PERFORM 3D software. In the first part of this study, different scenarios for a sudden elimination of columns are modeled and the effect of irregularities on the pattern of collapse is studied. Then viscous dampers are used in the model to study whether they are able to prevent or mitigate the dynamic effects caused by the progressive collapse. The results show that the corner columns of the buildings are more sensitive than side columns. In addition, installing viscous dampers in the structure can improve its dynamic behavior to some extent