A CASE STUDY ON PROGRESSIVE COLLAPSE OF BUILDINGS

Abstract

Progressive collapse has become a hot topic of interest and has led to a huge focus on safety of structures. The spread of a local failure has shown to cause catastrophic consequences like building destruction and a lot of deaths. These collapses happened in mid- and high-rise buildings under accidential or intentional circumstances for example the terrorist attack in World Trade Center. The huge consequences of progressive collapse forced researchers to study and improve methods to prevent it. Progressive collapse is a collapse where local failure leads to a disproportionate collapse. Due to improvement of technology and increase of threats in the construction process and more and more optimization of design through advanced analysis techniques buildings are believed to have become more vulnerable to loads outside the design envelope over the past decades and are thus more vulnerable to progressive collapse. Historical overview of previous and most famous cases of progressive collapse shows that this phenomenon is likely to happen in high structures where this research is going to be focused. In some of the cases structures that were marked as the safest have collapsed. The reasons were abnormal loading conditions outside design predictions or explosions which lead to major damages in structural elements. There are several types of collapses zipper, pancake instability and domino. Each of them starts with the damage in a column and the damage is spread in the whole building. In this study 3 design approaches are explained and compared: event control approach aimed at improving the level of protection of a building, the specific local resistance approach aimed at increasing the hardness of a building and alternate load path approach which aims at improving robustness of building by allowing local failure but creating altearnate paths that redistribute loads until structure is stabilized. The purpose of this research is to investigate structural non-linear behavior of building structures by checking their behavior in damaged conditions and develop design strategies in order to have safer structures that can resist the potential threat of progressive collapse. Three types of structures are going to be studied based on their results of period vibration and resistance when facing column removal. After the column removal the plastic hinges will be studied based on their number and performance level. In this way the safest structures can be selected and important conclusions are defined. Practical part of this study will be modelling with SAP2000 different metallic frame models. The results of SAP2000 will be the base of the study where all the conclusions will be refered to. Based on them it will be defined the comparison of structures. The best methods that are used to check the resistance of the structure are nonlinear static and dynamic as they offer the more accurate results than linear ones.