TECHNIQUES BEHIND DEMOLITION OF STRUCTURES

Shubhajit DuaCivil Engineering 3rd YearRoll-1358029University Roll-12601313047

INDEXI. IntroductionII. ObjectivesIII. Steps before DemolitionIV. Demolition sequenceV. Methods of Demolition

I. INTRODUCTION In general, demolition can be defined as wrecking or

taking out of any loadsupporting structural element of a building (houses, commercial establishments, and office buildings) or non-building facility (highways, streets, and other non-inhabitable construction projects).

It's a popular misconception that demolition is nothing more than knocking down a structure and hauling the debris to a landfill. That assumption is wrong on many counts, especially: First, the process of planning for and completing a demolition project is far more thorough and complex than simple knockdown. Second, demolition contractors are master of recovering valuable materials and minimizing need for disposal. Almost of the structure is salvaged for reuse and recycling then make the cost saved and bring more profit for the owner

II.OBJECTIVES Old and damaged buildings ( due to

earthquake & other various reasons) which are prone to fall down completely or partially must be demolished before any fatal accident.

When the important structural components like beams and columns become absolutely insufficient for service then there is no option other than demolishing the building.

When a new structure need to be constructed on the site the old structure is demolished.

For safety of neighbouring area a deteriorated building is often demolished.

III. STEPS BEFORE DEMOLITION

1. Surveying

2. Removal of hazardous materials

3. Preparation of plan

4. Safety measures

1. Surveying:

The building survey should cover following: The construction materials.  The existing use and, if possible, the past uses of the building prior to

demolition.  Adjoining pedestrian and vehicular traffic conditions.  The sensitivity of neighbourhood with respect to noise, dust, vibration

and traffic impact.  Available site area to allow on-site sorting of building debris.

2. Removal of hazardous materials:

Asbestos Containing Material In the case when asbestos

containing material are discovered, specialist contractor shall be employed to remove such asbestos containing material. The asbestos waste should be handled, stored and disposed of as chemical waste in accordance with the Waste Disposal Regulation.

Soil Contamination Material In the case when possible soil

contamination material is present, specialist shall be employed to prepare soil contamination test proposal and submit such proposal to the Environmental Protection Department for comment.

Asbestos Material

Soil Contamination

3. Preparation of plan:

A plan showing location of the building to be demolished, sections of the slopes with ground level contours and detailed topography, ground removal and backfilling, distances of adjacent structures from the building to be demolished.

A layout plan of all floors of the building to be demolished, with adequate sections.

A plan showing the procedure for the demolition of the building.

A plan showing the proposed shoring and temporary support to be provided to the building to be demolished.

In the case when powered mechanical plants and equipment are used, a plan showing the route of movement of powered mechanical plants and equipment.

4. Safety measures:

Training and Communication: Demolition workers, including

plant or equipment operators, shall go through proper job safety training and be informed of the potential hazards by attending training sessions as well as on-the-job training.

Equipment Maintenance:  All equipment shall be tested

and examined before use. They shall be properly stored and maintained. The equipment shall be inspected daily and results of the inspection shall be recorded accordingly.

Electrical Safety A properly connected power source from a local electric utility

supplier or a mobile electricity generator shall be utilized in demolition sites.

Fire All flammable goods shall be removed from site unless they

are necessary for the works involved. Any remaining flammable goods shall be stored in proper storage facilities. All furniture, timber, doors, etc. shall be removed before any welding work is performed. Fire fighting appliances shall be provided and maintained in working conditions.

V. METHODS OF DEMOLITION:

A. Ball and craneB. DismantlingC. Pneumatic and hydraulic breakerD. Explosives

A. Ball and crane .A crane uses a

wrecking ball, weighing up to 6120 kg, which is either dropped onto or swung into the element to be demolished.

Swinging the wrecking ballB. Dismantling

Selective or complete demolition of concrete structures is possible by cutting elements and then removing them with a crane.

The cutting process may be by sawing, water jetting or thermal lance.

Dismantling a beam

C. Pneumatic and hydraulic breaker A common piece of equipment used for demolishing bridge decks, foundations and pavements is a hydraulically or pneumatically operated, boom-mounted breaker.

A jackhammer is a pneumatic or electro-mechanical tool that combines a hammer directly with a chisel.

Jack hammer

A hydraulic breaker is a powerful percussion hammerfitted to an excavator for demolishing concrete structures or rocks. It is powered by an auxiliary hydraulic system from the excavator, which is fitted with a foot-operated valve for this purpose.

Hydraulic breaker

E. Implosion

In the controlled demolition industry, building implosion is the strategic placing of explosive material and timing of its detonation so that a structure collapses on itself in a matter of seconds, minimizing the physical damage to its immediate surroundings. RDX-based explosive

compounds expand at a very high rate ofspeed, up to 27,000 feet per second (8,230 meters per second)

Building Implosion

IMPLOSION OF OCEAN TOWER , TEXAS

In December,2008 the developers cracks in the columns of parking garage.The parking garage and the tower were mistakenly built connected, forcing the weight down upon the garage instead of on more solid “expansion joints”. The use of expandable clay, which compresses when weight is applied to it, compounded the issue and allowed the parking garage to remain relatively unsettled compared to the tower itself. Preliminary evaluation showed that the tower’s core had sunk 14 to 16 inches, while the attached parking lot had shifted less than half that distance.

 The 376-foot unfinished skyscraper was brought down with a controlled implosion on December 13, 2009. At 55,000 tons, it is claimed that it was the largest implosion of a reinforced concrete structure in the world.

Implosion of Ocean Tower , Texas

Process of Implosion

CONCLUSION It can be concluded that

demolishing/imploding the building structure will prove very useful, economical and quickest for reconstruction.

Leads to a safe and controlled demolition for the occupants and neighbourhood.

Development in techniques allows rapid demolition with no harm to the environment.

REFERENCES http://www.implosionworld.com/history.html www.wikipedia.com http://archsd.gov.hk/media/11640/

demolition_e2004.pdf http://wiki.iricen.gov.in/doku/lib/exe/

fetch.php?media=m%E0%A4%BEr%E0%A5%8Dc_march_2013:achuta_rao.pdf

http://www.concreteconstruction.net/Images/Demolition%20of%20Concrete%20Structures_tcm45-341335.pdf