Mitigation of Progressive Collapse of Multi-Storey Steel Building by Providing Chevron Bracings

Abstract

AbstractProgressive collapse of any structure causes disastrous failure of structure and significant loss of human lives as well as natural resources. Therefore, it is important to reduce the risk of progressive collapse of structure using various mitigation approaches to avoid disastrous consequences and economic & human losses. In the present study, the effectiveness of chevron bracing is evaluated for mitigation of progressive collapse of 9-storey regular steel moment resisting building. The bracings are provided in the alternate bays of the top storey. The progressive collapse potential of steel buildings is evaluated by following the Alternate Path Method (APM) as specified by U. S. General Services Administration (GSA 2016) guidelines. Linear static, nonlinear static and nonlinear dynamic analyses are performed using SAP2000 software under the middle column removal scenario from the ground floor of the perimeter frame in the longitudinal direction. The demand Capacity Ratio (DCR) of the beams and columns adjoining to the removed column are calculated by using linear static analysis. Nonlinear analyses are carried out to understand the failure mechanism of steel building and to obtain vertical displacement time history at the column removal location. From the results of linear static analysis, it is observed that the presence of bracing members significantly reduces the DCR of beams and columns and thus increases the progressive collapse resistance of the building structure. From nonlinear analyses, it is observed that the provision of bracings contributes to the redistribution of forces and effectively transfers the unbalanced vertical load developed due to the removed column to the adjoining structural members.KeywordsProgressive collapse mitigationSteel chevron braced frameMiddle column removal