If you buy into the picture of industrial demolition contractors as doing little more than hitting buildings haphazardly with wrecking balls, think again. Modern demolition isn’t some clumsy, chaotic affair. Each demolition project requires a slew of computed calculations; a consideration of physics and building dynamics; and a good deal of prior experience to avoid potential pitfalls. This is especially true for implosion jobs, in which explosive charges are placed throughout the structure and carefully timed to pull down the structure all at once. The explosives destroy the building’s support at a certain point, then the top stories fall into the bottom stories, and the building is ultimately destroyed by gravity; it succumbs to its own weight.
The major advantage of an implosion is its speed – in a matter of seconds, a building falls in upon itself. This way, the majority of the dust expulsion and sound pollution occurs all at once, at a pre-determined time.
However, it’s not easy to cause the near-instant demise of a building. And the stakes are huge. In addition to financial rewards for involved companies, a demolition job naturally impacts nearby neighbors. Dust and noise are the more benign outcomes – falling debris and crushed structures are the more extreme possibilities. For instance, during demolition of the Mad River Power Plant in Ohio in 2011, a toppling tower fell the wrong way and took out a few power lines. What caused this miscalculation? An unobserved crack along one side of the tower. This is only one of thousands of considerations that go into a building implosion.
Mark Loiseaux is one of the world’s experts in demolition; he has pulled down decommissioned nuclear towers as well as the unstable remnants of buildings on the 9/11 explosion site. Speaking to The Independent, Loiseaux said that industrial demolition is “50 percent joining the dots and 50 percent creativity, because you’re dealing with a structure that’s full of unknowns.”
When completing an implosion, or “blow-down,” industrial demolition firms must consider many elements, including:
- The amount of debris.
- Current weather conditions.
- The type of materials involved.
- The mass of the building and other physics.
- How the building is “reposing”; how it has settled onto the site.
- How to avoid damaging nearby buildings.
- How to avoid putting onlookers at risk.
In addition to these observable variables, an industrial demolition contractor must also make use of creativity while placing and timing explosives. It is a task that requires such finesse that there are special systems, such as the HotShot, for precisely calibrating the timing between “kicking” explosives (for blowing up support columns and determining the direction of fall) and “cutting” explosives (for burning through the building’s structure). There are even special explosives for cutting through steel supports. Because the placement of different explosives is so crucial for an implosion’s success, it can take a contractor as much as six months to prepare.
Ultimately, today’s demolition is a science as much as an art. As John Woodward, president of the Institute of Demolition Engineers puts it, “Anyone who thinks they can just hit a building with a big hammer and it falls down is misled.”
[Photo by: David Hilowitz, via CC License]