Static Equivalent Model for Progressive Collapse Analysis of Concrete Frame Structures

Progressive collapse is not a new issue to the structural engineering community. Progressive collapse is generated by localized failure of one or two major structural elements following a severe blast or impact loading on the structure. Significant load transfers could take place. The structure is likely to suffer progressive collapse when the transferred loads exceed the capacity of the elements remaining in the structure following initial damage. The Ronan Point apartment building in London 1968 collapsed following a gas explosion on the 18th floor of the 22-storey pre-cast concrete building. The dramatic partial collapse of the building caused widespread concern for potential collapse of high-rise buildings in a chain-reaction-mode triggered by localized failures. The collapse of Murrah Federal Building, Oklahoma City in 1995, following a major bomb attack is another example of progressive collapse. The well publicized collapse of the World Trade Centre in New York in 2001 is yet another classical example of progressive collapse. It is evident from the cited examples that progressive collapse is not a new issue, and yet, there is no formal regulatory document around the world that give complete guidance for designing against progressive collapse, except for some general guidance (eg. ASCE 7-98) forming part of a multi-hazard analysis document. The response of a structure under progressive collapse is dynamic and nonlinear, both in terms of geometry and material behaviour (Smilowitz, 2002). This paper considers the analysis for progressive collapse of a beam when a supporting column has been removed suddenly by an explosion.