Building implosion

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June 2006 demolition of the 12-story Tencza Apartment building in Arlington, Virginia. (See video)

Building implosion is a term in use in the controlled demolition industry. It refers to strategically placing explosive material and timing its detonation so that a structure collapses on itself in a matter of seconds minimizing the physical damage to its immediate surroundings.

Building implosions (which reduces to seconds a process which could take months or years to achieve by conventional methods) typically occurs in urban areas and often involves large landmark structures.

1 Disambiguation
2 Historical overview
3 Footnotes
4 External links

[edit] Disambiguation

The term Building Implosion can be misleading to laymen. Although its name includes the word implosion, it is not an implosion phenomenon. Implosion occurs when the difference between internal to external pressure is such that a structure collapses on itself. When external pressure on a structure is greater than its internal pressure, the structure implodes. The building implosion technique does not rely on the difference between internal and external pressure to collapse the building, but simply on the effect of gravity. Numerous small explosions are used to catalyze the collapse, having been strategically planned within the structure and timed to occur in concert, often detonating within milliseconds of one another. Days or even weeks of preparation frequently precede such an event. The explosions blow the air out of the building along with the support structures thus leaving a "vacuum" which has the effect of bringing the building down at rapid speeds.

[edit] Historical overview

Building implosion is part of the demolition industry history which itself depends directly on explosives history.

Earliest documented attempt to a "building implosion" demolition is the razing of Holy Trinity Cathedral in Waterford Ireland. This 1773 event involved 150 pounds of gunpowder, a low velocity explosive. Although it is not clear to which extent this attempt was successful in lowering collateral damage, the demolition was a success^[1]

With the first skyscrapers being built and Dynamite, which is a high-velocity explosive, being made available in the 1900s, other considerations for the use of explosive demolition of building emerged: the safety of workers and spectators and limiting collateral damage to surroundings. This is the starting point of experimental research that will eventually lead to building implosion technique being developed. Profiting from dynamite advantages and borrowing from techniques used in rock-blasting such as delaying detonation and use of several smaller charges instead of a massive one, demolition moved towards more and more efficient building implosion results.

Soon after the end of World War II European military experts had gathered enough practical knowledge and experience in demolition to be able to bring down large structures in dense urban area with no harm to adjacent properties. ^[2]

The post-WW2 period saw the emerging of a demolition industry, which grew during the second half of the twentieth century to come to maturation, in the meantime research conducted to improve high explosives efficiency ^[3] and non-electrical firing systems were developed. These combined to make this period of time an extensive use of the building implosion technique.

This evolution in mastering controlled demolition lead to the world record ^[4] demolition of the Seattle Kingdome on March 26 2000 ^[5]

In 1997, a building implosion in Canberra, Australia, went badly wrong. The main building did not fully disintegrate and had to be manually demolished. But far worse, the explosion was not contained on the site and large pieces of debris were projected towards spectators situated 500 metres away, in a location that nobody considered unsafe or inappropriate. A twelve year old girl was killed instantly, and nine other people were injured. Large fragments of masonry and metal were found 650 metres from the demolition site.^[6]

[edit] Footnotes

^ The Irish Times reported that the structure "succumbed to a deafening boom, and was instantly reduced to rubble." quoted from "A History of Structural Demolition in America" by author Brent L. Blanchard
^ A History of Structural Demolition in America" by author Brent L. Blanchard"
^ see RDX for more details
^ Seattle Kingdome is the world's largest structure by volume to have been demolished by explosives.[1]
^ details and video available on www.controlled-demolition.com website
^ Madden (ACT Coroner), Shane G. (1999). General Chronology and Overview. The Bender Coronial Decision. ACT Magistrates Court and Tribunals (Coroner's Court). Retrieved on 2007-03-07.