Demolition
Demolition (also known as razing, cartage, and wrecking) is the science and engineering in safely and efficiently tearing down of buildings and other artificial structures. Demolition contrasts with deconstruction, which involves taking a building apart while carefully preserving valuable elements for reuse purposes.
For small buildings, such as houses, that are only two or three stories high, demolition is a rather simple process. The building is pulled down either manually or mechanically using large hydraulic equipment: elevated work platforms, cranes, excavators or bulldozers. Larger buildings may require the use of a wrecking ball, a heavy weight on a cable that is swung by a crane into the side of the buildings. Wrecking balls are especially effective against masonry, but are less easily controlled and often less efficient than other methods. Newer methods may use rotational hydraulic shears and silenced rockbreakers attached to excavators to cut or break through wood, steel, and concrete. The use of shears is especially common when flame cutting would be dangerous.
The tallest planned demolition of a building was the 52-storey 270 Park Avenue in New York City, which was built in 1960 and torn down in 2019–2021 to be replaced by 270 Park Avenue.[1]
Manual
Before any demolition activities can take place, there are many steps that must be carried out beforehand, including performing asbestos abatement, removing hazardous or regulated materials, obtaining necessary permits, submitting necessary notifications, disconnecting utilities, rodent baiting and the development of site-specific safety and work plans.
The typical razing of a building is accomplished as follows:
- Hydraulic excavators may be used to topple one- or two-story buildings by an undermining process. The strategy is to undermine the building while controlling the manner and direction in which it falls.
- The demolition project manager/supervisor will determine where undermining is necessary so that a building is pulled in the desired manner and direction.
- The walls are typically undermined at a building's base, but this is not always the case if the building design dictates otherwise. Safety and cleanup considerations are also taken into account in determining how the building is undermined and ultimately demolished.
In some cases a crane with a wrecking ball is used to demolish the structure down to a certain manageable height. At that point undermining takes place as described above. However, crane mounted demolition balls are rarely used within demolition due to the uncontrollable nature of the swinging ball and the safety implications associated.
High reach demolition excavators are more often used for tall buildings where explosive demolition is not appropriate or possible. Excavators with shear attachments are typically used to dismantle steel structural elements. Hydraulic hammers are often used for concrete structures and concrete processing attachments are used to crush concrete to a manageable size, and to remove reinforcing steel. For tall concrete buildings, where neither explosive nor high reach demolition with an excavator is safe or practical, the "inside-out" method is used, whereby remotely operated mini-excavators demolish the building from the inside, whilst maintaining the outer walls of the building as a scaffolding, as each floor is demolished.
To control dust, fire hoses are used to maintain a wet demolition. Hoses may be held by workers, secured in fixed location, or attached to lifts to gain elevation.
Loaders or bulldozers may also be used to demolish a building. They are typically equipped with "rakes" (thick pieces of steel that could be an I-beam or tube) that are used to ram building walls. Skid loaders and loaders will also be used to take materials out and sort steel.
The technique of Vérinage is used in France to weaken and buckle the supports of central floors promoting the collapse of the top part of a building onto the bottom resulting in a rapid, symmetrical, collapse.[2]
The Japanese company
To demolish bridges,
Fred Dibnah used a manual method of demolition to remove industrial chimneys in Great Britain. He cut an ingress at the base of the chimney—supporting the brickwork with wooden props—and then burning away the props so that the chimney fell, using no explosives and usually hand-operated power tools.[4]
Building implosion
Large buildings, tall
Any error can be disastrous, however, and some demolitions have failed, severely damaging neighboring structures. One significant danger is from flying debris, which, when improperly prepared for, can kill onlookers.
Another dangerous scenario is the partial failure of an attempted implosion. When a building fails to collapse completely the structure may be unstable, tilting at a dangerous angle, and filled with un-detonated but still primed explosives, making it difficult for workers to approach safely.
A third danger comes from air overpressure that occurs during the implosion. If the sky is clear, the shock wave, a wave of energy and sound, travels upwards and disperses, but if cloud coverage is low, the shock wave can travel outwards, breaking windows or causing other damage to surrounding buildings.[5]
Controlled implosion, being spectacular, is the method that the general public often thinks of when discussing demolition; however, it can be dangerous and is only used as a last resort when other methods are impractical or too costly. The destruction of large buildings has become increasingly common as the massive
Preparation
This section may require cleanup to meet Wikipedia's quality standards. The specific problem is: Phrased as facts but not necessarily true in all cases of implosion. Some information not specific to implosion. (November 2023) |
It takes several weeks or months to prepare a building for implosion. All items of value, such as copper wiring, are stripped from a building. Some materials must be removed, such as
Deconstruction
An alternative approach to demolition is the deconstruction of a building with the goal of minimizing the amount of materials going to
The development of plant and equipment has allowed for the easier segregation of demolition waste types on site and the reuse within the construction of the replacement building. On site crushers allow the demolished concrete to be reused as type 1 crushed aggregate either as a piling mat for ground stabilization or as aggregate in the mixing of concrete.
Timber waste can be shredded using specialist timber shredders and composted, or used to form manufactured timber boards, such as MDF or chipboard.
Safety is paramount; a site safety officer is usually assigned to each project to enforce all safety rules and regulations.
See also
- Construction waste – Unwanted material produced directly or incidentally by the construction industries
- Demolition waste – Waste debris from destruction of buildings, roads, bridges, or other structures
- Excavator Ram guard (Protection of excavators used for demolition)
- House demolition – Military tactic (military tactic)
- ICE demolition protocol
- List of demolished buildings and structures in London
- National Federation of Demolition Contractors (UK)
- Slighting – A type of destruction
- Teardown (real estate) – Process of replacing an old building with a new one
- Urban renewal – Land redevelopment in cities
References
- ^ https://www.newyorkyimby.com/2017/09/270-park-avenues-shrouded-demolition-making-progress-in-midtown-east.html [dead link]
- ^ "HD_20h_20070822_chunk_2 – Vidéo Dailymotion". Dailymotion.com. 23 August 2007. Retrieved 6 May 2012.
- ^ "Kajima Demolition Tech". Popular Science. December 2008. Retrieved 18 November 2008.
- ISBN 0-593-05664-7.
- ^ Cultice, Curtice (1997). "Blasting a path to world markets". BNET Business Network. Retrieved 19 May 2008.
- ^ "J.L. Hudson Department Store". Controlled Demolition, Inc. Archived from the original on 20 December 2008. Retrieved 20 October 2006.
- ^ Public Broadcasting Service. Retrieved 29 April 2009.
She learned the fine art of demolition from her father, Mark Loizeaux, and her uncle, Doug Loizeaux—president and vice-president of the company. NOVA spoke with Ms. Loizeaux a few days before Christmas, 1996.
- ^ "Taisei Corporation's Tecorep reducing CO2 emissions by 85%". Archived from the original on 15 April 2016. Retrieved 26 August 2017.
External links
Media related to Demolition at Wikimedia Commons