Assessment of Dynamic Increase Factor after Column Removal by Pulldown and Finite Element Analysis

Progressive collapse is defined as a phenomenon with spread of an initial local failure from an element to another and leads to collapse of an entire structure or a disproportionately large part of it. To assess structures against progressive collapse, using linear and nonlinear static analyses and nonlinear dynamic analysis based on permitted guidelines. Performing nonlinear static analysis with proper Dynamic Increase Factor (DIF) can be a suitable method of approach as opposed to nonlinear dynamic analysis to predict structural response. Therefore, guidelines suggest various formulas to calculate DIF for different kinds of structures. These formulas depend only on maximum acceptable ductility of the critical member and to obtain these, some approximations due to regression and analysis type occur. In this research, three dimensional structures and all the rigid connection details of beam to column and pinned connection details of beam to beam were modeled in Abaqus. The real DIFs were obtained for three locations of corner, perimeter and middle column removal using pulldown method and compared to the ones suggested by the guidelines. The results revealed that there were differences between obtained DIFs from dynamic pulldown analysis and suggested guideline DIFs and these differences were more in specific ratio of plastic to yield rotations.