PROGRESSIVE COLLAPSE ANALYSIS OF REINFORCED CONCRETE FRAMED STRUCTURE

Abstract

Progressive collapse is a chain reaction of failures that propagates either throughout or a portion of the structure disproportionate to the original local failure. The progressive collapse of building structure is initiated when one or more vertical load carrying members are removed. Once a column is removed or made weak, due to man-made or natural hazards, load carried by column removed is transferred to neighbouring columns in the structure, if the neighbouring column is incapable of withstanding the extra load, leads to the progressive failure of adjoining members and finally to the failure of partial or whole structure. The collapsing system continually seeks alternative load paths in order to survive. One of the important characteristics of progressive collapse is that the final damage is not proportional to the initial damage. The research material available for progressive collapse failure of structures suggests that buildings designed to resist seismic actions have good robustness against progressive collapse. However, no detailed investigations have been conducted so far to assess this robustness. Hence this study is made to examine the potential ability of seismically designed building against progressive collapse. A twelve storey reinforced concrete framed structure was considered in the study to evaluate the Demand Capacity Ratio (DCR), the ratio of the member force and the member strength as per U.S. General Services Administration (GSA) guidelines. The Linear static analysis is carried out using software, ETABS according to Indian Standard codes. Analysis and design is carried out to get the final output of design details. To study the collapse, typical columns are removed one at a time, and continued with analysis and design. Many such columns are removed in different trials to know the effects of progressive analysis. Member forces and reinforcement details are calculated. From the analysis, DCR values of columns and beams are calculated.