Progressive Collapse Case Study

CHAPTER-1

INTRODUCTION

1.1. GENERAL

The term “progressive collapse” has been used to describe the spread of an initial local failure in a manner similar to a chain reaction that leads to partial or total collapse of a building. The fundamental characteristic of progressive collapse is that the final state of failure is disproportionately greater than the failure that originated the collapse. Progressive collapse as “the spread of an initial local failure from element to element resulting, finally in the collapse of an entire structure or a disproportionately large part of it”. The disproportionality refers to the condition in which failure of one member causes a major collapse, with an amount disproportionate to the original event. Thus, “progressive

The design of a building to resist progressive collapse may involve analytical methods that are not used in predictable design. The purpose of this project is to offer few concepts for design professionals to decrease the probability of progressive collapse of buildings in the event of irregular loading. It is not proposed as a design standard.

The partial collapse of the 22-storey Ronan Point apartment tower in Newham (east London) in 1968 illustrated the interest of the research community towards this phenomenon for the first time. A gas explosion in a corner of the 18th floor blew out a load-bearing wall, which in turn caused the collapse of the upper floors due to the loss of support. The impact of the upper floors on the lower ones led to a consecutive failure all the way down to the ground level. As a result, the entire corner of the building collapsed, as can be observed in Figure 1.1. This partial collapse was recognized to the failure of the structure to redirect loads after the loss of a load-carrying member. It is a predominantly illustrative example since the magnitude of the collapse

The issue of progressive collapse was conveyed to the front again after the attacks against the World Trade Centre towers in New York City in September 11, 2001. The large number of victims and the economic loss that convoyed this multiple collapse brought a transformed interest in the subject among other federal institutions of the United States, such as the General Services Administration (GSA) and the Department of Defence (DoD), which released their Progressive collapse analysis and design guidelines for new federal office buildings and major transformation projects and Unified Facilities Criteria (UFC): Design of buildings to resist progressive collapse individually[4].

1.2. Types of Progressive Collapse

Even though progressive collapse is achieved in the design rules and standards as one event it can be divided into several parts depending on the reason for the progressivity. The reason that causes the progressive collapse depends on the type of structure and the beginning event. Below five types of progressive collapse will be described. The presented collapse modes are

a. Pancake

b. Zipper

c. Domino

d. instability and

e. section-type