PROGRESSIVE COLLAPSE ANALYSIS of REINFORCED CONCRETE BUILDING SUBJECTED to SEISMIC ACTION

Abstract

A progressive collapse is a phenomenon where localized failure(s) propagates to collapse an entire multi-story structure or a significant portion thereof. A building undergoes Progressive collapse when a primary structural element fails, failing adjoining structural elements, which in turn causes further structural failure. This accidental action may be due to design deficiencies or errors, material failure, an act of terrorism, or natural phenomena like an earthquake. Most of the structures in the country are designed and constructed only to resist gravity load and seismic action according to the location of the structure so it is difficult to know the response of those structures to such types of extreme loading. To study the effect of seismically designed structures on the resisting capacity of Progressive collapse it is necessary to analyze and investigate those structures using different techniques. This may help us to improve the capacity of the existing structure as well as to improve the design and detailing of the newly designed structure. So that in this study the PC due to failure of the load-bearing element was conducted. A non-linear dynamic time-history analysis was performed in correspondence with a guideline of the General service administration. A six-story reinforced concrete structure was designed and detailed for low, medium, and high ductility classes with 0.15g ground acceleration, and ground type c was considered in seismic design. For progressive collapse analysis, a total of 24 models were modeled based on the result found from seismic design. A non linear dynamic time-history analysis was performed by using ETABS 20 and the result shows that a structure that is designed with a low ductility class has less displacement in comparison with the other ductility classes and a structure designed for high ductility classes shows greater vertical displacement above the failed column. Based on it can be concluded as a structure with low ductility class had higher Progressive collapse resistance from the other types of ductility classes. In the same manner, a building designed for a deficient structure with improper and insufficient seismic provision fails in the transferring of loads to the adjacent elements, and the rotation was under the collapse limit. Another structure was designed and modeled with no slab for analyzing the effects of slab stiffness on the progressive resistance of structures. From non-linear dynamic time history analysis, it is found that the structures without slab face greater vertical displacement and horizontal displacement from that of a structure that considered the stiffness of the slab.