Building implosion

AfE-Turmbuilding demolition slow motion video

Implosion of theAthlone Power Stationcooling towers

Blasting of a highway bridge inAachen,Germany

In thecontrolled demolitionindustry,building implosionis the strategic placing ofexplosive materialand timing of its detonation so that a structure collapses on itself in a matter of seconds, minimizing the physical damage to its immediate surroundings. Despite its terminology, building implosion also includes the controlled demolition of other structures, likebridges,smokestacks,towers,andtunnels.This is typically done to save time and money of what would otherwise be an extensive demolition process with construction equipment, as well as to reduce construction workers exposure to infrastructure that is in severe disrepair.

Building implosion, which reduces to seconds a process which could take months or years to achieve by other methods, typically occurs in urban areasand often involves large landmark structures.

The actual use of the term "implosion" to refer to the destruction of a building is amisnomer.This had been stated of the destruction of1515 TowerinWest Palm Beach, Florida."What happens is, you use explosive materials in critical structural connections to allow gravity to bring it down."

Terminology

Implosion of Radio Network House, damaged by the2011 Christchurch earthquake,in theChristchurch Central City

The term "implosion" was coined by my grandmother back in, I guess, the '60s. It's a more descriptive way to explain what we do than "explosion". Therearea series of small explosions, but the building itself isn't erupting outward. It's actually being pulled in on top of itself. What we're really doing is removing specific support columns within the structure and then cajoling the building in one direction or another, or straight down.

— Stacy Loizeaux,NOVA,December 1996

The termbuilding implosioncan be misleading to a layperson: The technique is not a trueimplosionphenomenon. A true implosion usually involves a difference between internal (lower) and external (higher) pressure, or inward and outward forces, that is so large that the structure collapses inward into itself.

In contrast, building implosion techniques do not rely on the difference between internal and external pressure to collapse a structure. Instead, the goal is to induce aprogressive collapseby weakening or removing critical supports; therefore, the building can no longer withstand gravity loads and will fail under its own weight.

Numerous small explosives, strategically placed within the structure, are used to catalyze the collapse.Nitroglycerin,dynamite,or other explosives are used to shatter reinforced concrete supports.Linear shaped chargesare used to sever steel supports. These explosives are progressively detonated on supports throughout the structure. Then, explosives on the lower floors initiate the controlled collapse.

A simple structure like a chimney can be prepared for demolition in less than a day. Larger or more complex structures can take up to six months of preparation to remove internal walls and wrap columns with fabric and fencing before firing the explosives.

Historical overview

Demolition by controlled explosion inBuffalo, New York

The demolition of theNew Haven ColiseuminNew Haven, Connecticut

As part of thedemolitionindustry, the history of building implosion is tied to the development ofexplosivestechnology.

One of the earliest documented attempts at building implosion was the 1773 razing of Holy Trinity Cathedral inWaterford,Irelandwith 150 lb (68.04 kg; 10.71 st) ofgunpowder,a huge amount of explosives at the time. The use oflow velocity explosiveproduced a deafening explosion that instantly reduced the building to rubble.

The late 19th century saw the erection of—and ultimately the need to demolish—the firstskyscrapers,which had more complicated structures, allowing greater heights. This led to other considerations in the explosive demolition of buildings, such as worker and spectator safety and limiting collateral damage. Benefiting from the availability ofdynamite,a high-velocity explosive based on a stabilized form ofnitroglycerine,and borrowing from techniques used in rock-blasting, such as staggered detonation of several small charges, the process of building implosion gradually became more efficient.

FollowingWorld War II,European demolition experts, faced with huge reconstruction projects in dense urban areas, gathered practical knowledge and experience for bringing down large structures without harming adjacent properties.This led to the emergence of a demolition industry that grew and matured during the latter half of the twentieth century. At the same time, the development of more efficient high-velocity explosives, such asRDX,and non-electrical firing systems combined to make this a period of time in which the building implosion technique was extensively used.

Meanwhile, public interest in the spectacle of controlled building explosion also grew. The October 1994 demolition of the Sears Merchandise Center inPhiladelphia, Pennsylvaniadrew a cheering crowd of 50,000, as well as protesters, bands, and street vendors selling building implosion memorabilia.Evolution in the mastery of controlled demolition led to the world recorddemolition of theSeattle Kingdomeon March 26, 2000.

In 1997, theRoyal Canberra Hospitalin Canberra, Australia, was demolished. The main building did not fully disintegrate and had to be manually demolished. The explosion during the initial demolition attempt was not contained on the site and large pieces of debris were projected towards spectators 500 m (546.81 yd) away, in a location considered safe for viewing. A twelve-year-old girl was killed instantly, and nine others were injured. Large fragments of masonry and metal were found 650 m (710.85 yd) from the demolition site.

On October 24, 1998, theJ. L. Hudson Department Store and AdditioninDetroit, Michiganbecame the tallest, and the largest, building ever imploded.

On December 13, 2009, an unfinished 31-story condominium tower, known as theOcean Tower,was imploded inSouth Padre Island, Texas.Construction on the new tower had begun in 2006, but it had been sinking unevenly during construction, which halted in 2008, and could not be saved. It is believed to be one of the tallest reinforced concrete structures ever imploded.

Building implosion has been successfully used at Department of Energy sites such as the Savannah River Site (SRS) in South Carolina and the Hanford Site in Washington. The SRS 185-3K or "K" Area Cooling Tower, built in 1992 to cool the water from the K Reactor, was no longer needed when the Cold War ended and was safely demolished by explosive demolition on May 25, 2010.

The Hanford Site Buildings 337, 337B, and the 309 Exhaust Stack, built in the early 1970s and vacated in the mid-2000s due to deteriorating physical condition, were safely razed by explosive demolition on October 9, 2010.

Gallery

• 
  Demolition of a chimney at the former "Henninger Brewery"inFrankfurt am Main,Germany, on 2 December 2006
• 
  June 2006 demolition of the 12-story Tencza Apartment building inArlington, Virginia.(Seevideo)
• Tappan Zee Bridge explosive demolition in slow motion

See also

• Controlled Demolition, Inc.
• List of tallest voluntarily demolished buildings

External links

• Demolition SimulationAdvanced structural analysis for predicting demolitions.
• A History of Structural Demolition in Americaby Brent L. Blanchard
• How Building Implosions Workby Tom Harris onwww.howstuffworks.com
• Building ImplosionsVideos
• Bank Implosion Videos and PhotosVideos