Progressive Collapse—An Implosion Contractor’s Stock in Trade

When designing a building intended to be resistant to progressive collapse, it is instructive to consider this problem from the point of view of an implosion contractor who regularly demolishes buildings through explosives-induced progressive failure. All buildings want to fall down, but are prevented from doing so through their structural columns, walls and transfer girders. Innumerable ergs of potential energy are just waiting to be released. The implosion contractor creates a progressive collapse by releasing this energy through the sequential explosive removal of key structural supports, allowing gravity to do the remaining work, simultaneously using the minimum amount of explosives, creating the maximum amount of fragmentation, and minimizing the potential fly of debris. In this paper, we will explore several building structural systems and how their implosion has historically been achieved, comparing the amount of effort required in each system to affect an implosion as related to the susceptibility of that type of building to progressive collapse and identifying those types that lend themselves to it. The building structural systems described represent actual case studies. By comparison of different systems from the implosion contractor’s perspective, the design engineer will gain unique knowledge about systems that are inherently resistant to progressive collapse.