Demolition
Introduction
Demolition or demolition is the opposite of construction: the destruction of buildings and other structures. The tallest building demolished was the 47-story Singer Building in New York City, which was built in 1908 and torn down between 1967 and 1968 to be replaced by One Liberty Plaza.
For most buildings, such as houses, that are only two or three stories high, demolition is a simpler process. The building is demolished either manually or mechanically using numerous hydraulic equipment: elevated work platforms, cranes, excavators and bulldozers.
Larger buildings may require the use of a wrecking ball, a heavy weight suspended from a cable that is swung by a crane (machine) toward the buildings facade. Wrecking balls are especially effective against masonry, but are more difficult to control and often less efficient than other methods. New methods may use rotary hydraulic shears and silent stone crushers in conjunction with excavators to cut or break through wood, steel and concrete. The use of shears is especially common when torch cutting would be dangerous.
Building implosion
Tall buildings and chimneys and increasingly some smaller structures can be destroyed by imploding buildings using explosives. Imploding a building is very fast—the collapse itself only takes seconds—and an expert can ensure that the building falls within its own perimeter, so as not to damage nearby structures. This is essential for tall structures in densely built-up areas. The biggest danger is flying debris which can kill spectators if prepared incorrectly. Even more dangerous is the partial failure of an implosion attempt. When a building does not completely collapse, the structure may be unstable, leaning at a dangerous angle, and filled with undetonated explosives, but still in perfect condition, making it difficult and unsafe for workers to approach.
It takes several weeks to prepare a building for an implosion. All valuables, such as copper wiring, are removed from the building. Some materials must be removed, such as glass that can form deadly projectiles and insulation that can be spread over a wide area. Some selected columns are drilled and an explosive with high breaking power, such as Rionel or Goma 2, is placed in their holes. Supports and load-bearing walls can be eliminated with detonating cord. The goal is to use the smallest amount of explosive possible; only a few plants are loaded with explosives. Areas with explosives are covered with wide plastic and fencing to absorb flying debris. Much longer than the demolition itself is the clearing of the site, as the debris is loaded onto trucks and transported to another location. The destruction of large buildings has become increasingly common due to the massive housing projects of the 1960s and 1970s that are collapsing around the world. With 133.8 m and 204,000 square meters, the J.L. Hudson Department Store and Addition is the tallest steel-framed building and the largest structure ever to implode.