Capacity assessment of 2 Dimensional structural steel frames subjected to localized fire
In the analysis of progressive collapse, the design is chosen as an event independent. The progressive collapse condition may occur due to removal or damage of vertical load bearing members by factors like fire, vehicle impacts, faulty constructions etc. This study specifies the comparative structural response of two dimensional three bayed Steel Moment Resisting Frame (SMRF) prone to localized fire. Nonlinear analysis is carried out in the steel frame subjected to localized fire with a function of time. General Service Administration (GSA) guidelines are adopted for load assigns. As per the GSA, corner and intermediate columns are chosen and are prone to thermal loading to a maximum of about 800̊ C which are linearly incremented with respect to time. Here the alternate load path method is followed, thus increasing the redundancy of the structure would stabilize it against the progressive collapse. Initially the comparative assessment is done between the corner and intermediate columns where their displacements, axial force, shear force and equivalent stress are assessed. Based on this initial study, the key vulnerable members are spotted and strengthened by varied bracings. Diverse bracings incorporated in the structure taken under consideration are like X, Diagonal and Inverted V. Then the overall performance of the bracing incorporated frames namely X Braced Steel Frames (XBSF), Diagonal Braced Steel Frames (DBSF) and Inverted V Braced Steel Frames (IVBSF) are evaluated for their structural performance as before.
Keywords: Localized fire, Structural Steel failure, transient thermal loading, progressive collapse, alternate load path.