DEMOLITION WORKS

WHAT IS DEMOLITION ?

"demolition" means the complete or partial demolition of a building or structure by pre-

planned and controlled methods or procedures”.

“Demolition means dismantling, destroying or wrecking any building or structure or any part thereof by pre-planned and controlled

methods”

CAUSES OF DEMOLITION

BUILD NEW BUILDING

AESTHETIC

STRUCTURE PROBLEM

POPULATION DENSITY

AGING BUILDING

DEMOLITION SEQUENCESDemolition sequence shall be determined based on Actual site conditions, Restraints, The building layout, The Structural layout and its construction.

In general, the following sequence shall apply:1) UTILITIES disconnection Electricity ,plumbing water lines drainage connections etc.2) All cantilevered structures, canopies, verandahs and features

attached to the external walls shall first be demolished prior to demolition of main building and its internal structures on each floor

3) When demolishing the roof structure, all lift machine rooms and water tanks at high level shall be demolished in “top down” sequence to the main roof level

DEMOLITION PROCESS (Pre-demolition)

Site survey

Site preparation

and mobilization

Identify safety

measure

Arrange debris

handling

DEMOLITION PROCESS( Demolition Phase )

Demolition

Ensure workers follow

safety procedures

Ensure machines well

maintain

DEMOLITION PROCESS( Post Demolition )

Site clearance

METHOD OFDEMOLITION

Demolition methods can vary depending on the following :

• The area where it will be held on• Time available• The building material• The purpose of the demolition and • The way that debris is going to be disposed.

Time saving methods are more expensive than the slower ones. If noise, dust, and vibrations are to be restricted, it will add to the cost of demolition.

i) MANUAL DEMOLITION

Manual methods are carried out top down, proceeding, in general,

from the roof to ground.

For reinforced concrete buildings, jack hammers are commonly used

to break down the concrete.

Where concrete members are being demolished manually, the reinforcement shall not be cut while breaking of the concrete.

Manual demolition has many of hazards : unexpected collapse,

falls, falling object

In congested areas, these features could have critical impact on the

safety of the public.

Areas where debris will fall should be

barricaded off and sign erected to prevent

person from entering before demolition

starts.

MANUAL DEMOLITION

ii) MECHANICAL DEMOLITION• The sequence of demolition by machine is

typically the same as the top down manual method, except that most of the demolition is done by mechanical plant.

• Mechanical demolition generally involves the use of large machinery with attachment to dismantle the building from outside.

• The common mechanical method : pusher arm, wrecking ball, pneumatic impact tools and explosive

CRANE AND WRECKING BALL

• The wrecking ball application consists of a crane equipped with a steel ball.

• The destruction of the building is by the impact energy of the steel ball suspended from the crawler crane. The wrecking ball operates outside the building.

• This method is suitable for dilapidated buildings, silos and other industrial facilities.

• However, the operation requires substantial clear space. The application also demands high level skill operators and well-maintained equipment.

The balling of each section of the structure shall proceed from top to bottom.

VERTICAL DROP SWING IN-LINE

Free falling of the wrecking ball onto the structure

Swinging of the ball in-line with the jib.

The ball shall be swung into the building.

The ball shall strike at the top of the member so as to avoid

the member from falling outside the building.

PUSHER MECHANICAL ARM

• The crusher attachment breaks the concrete and the reinforcement by the hydraulic thrust through the long boom arm system.

• The hydraulic crusher can be operated from the ground outside the building. This method is also suitable for dangerous buildings, silos and other industrial facilities.

• The excavator shall operate on firm ground that can support the machine during the crusher operation.

The operation shall have a minimum clear space of ½ the building height as a safety zone for the falling debris. Each section of the structure shall be demolished in a top down sequence to ensure stability of the structure.

EXPLOSION

The explosive chargers are set and fired in a sequence that will weaken the structure in such a way that the

building collapse in upon itself.

Use non-explosive : without noise and initial devastating blast.

Competent explosive specialist is required when demolition is to be

done by using explosive

BLASTING ME

CHINES

• Traditional rack-bar and

• Modern electronic control box

PNEUMATIC IMPACT TOOLS

Pneumatic tool or air tool is a tool driven by a gas, usually

compressed air supplied by a gas compressor.

Pneumatic tools are commonly cheaper and safer to run and maintain than their electrical

power tool.

SPECIAL SAFETY CONSIDERATION

•Workers shall go to proper job safety training

•Regular safety meeting

Training and communication

•Equipment shall be tested and examined before use.

Equipment maintenance

•A properly connected power source from a local electric utility supplier or a mobile electricity generator shall be utilized in demolition sites

Electrical safety

•All flammable goods shall be removed from site

•Fire fighting appliances shall be provided

Fire

•Emergency exits shall be provided during building demolition.

Emergency Exit

•Demolition work will cause vibration to neighboring buildings or structures to various extent, depending on the method of demolition, which should be controlled by suitable monitoring. The most serious vibration is caused by implosion.

Vibration

ENVIRONMENTAL PRECAUTIONS

Air pollution- dust mitigation measure

Noise - Silent type of mechanical equipment

Hazardous material have to be properly handled