Design of Building Structures to Improve their Resistance to Progressive Collapse

It is rare nowadays for a “new topic” to emerge within the relatively mature field of Structural Engineering. Progressive collapse – or, more particularly, understanding the mechanics of the phenomenon and developing suitable ways to accommodate its consideration within our normal frameworks for structural design – can be so regarded. Beginning with illustrations drawn from around the world over several decades and culminating in the highly public WTC collapses, those features essential for a representative treatment are identified and early design approaches are reviewed. More recent work is then reported, concentrating on developments of the past seven years at Imperial College London, where a comprehensive approach capable of being implemented on a variety of levels and suitable for direct use by designers has been under development. Illustrative results are used to assist in identifying some of the key governing features, to show how quantitative comparisons between different arrangements may now be made and to illustrate the inappropriateness of some previous design concepts as a way of directly improving resistance to progressive collapse.