Demolition of Buildings-av

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Demolition of Structures


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Contents

1. Demolition of buildings: IS 4130

1.1 Planning

1.2 Precautions before starting

the work

1.3 Protection of the public

1.4 Sequence of demolition operations1.5 Removal of materials

1.6 Demolition of walls

1.7 Demolition of floors

1.8 Recommendations for demolition

of particular elements

2.Government Clearances

3. Demolition Methods


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Why?


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Demolition of buildings: IS 4130


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1.2.PRECAUTIONS BEFORE STARTING THE WORK

Danger signs shall be conspicuously posted all around the structure and

all doors and openings into it shall be barricaded or manned. However

provision for at least two independent exits for workmen to be given

During nights, red lights are to be placed on all barricades

Possibilities of any danger to adjacent structure shall require the people

to be vacate for the safety

The power lines, gas and water supply shall be cut off

All the mains and meters of the building are to be removed or protected

from damage

1.3.PROTECTION OF THE PUBLIC

Sidewalks and roads adjacent to the work likely to be affected are to be

closed or protected

A side walk shed is to constructed along the entire length of the sidewalk

if the distance horizontal is 4.5m or less and building is 7.5m or high. The

roof of the shed should be able to sustain a load of 73N/mm sq.


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1.4.SEQUENCE OF DEMOLITION OPERATIONS

All glazed ,sash, glazed doors and windows etc shall be

removed

All loose plaster is stripped off to reduce dust production All floor openings and shafts shall be floored over and

enclosed with guard rails

Demolition shall always proceed systematically storey by

storey in a descending order

1.5.REMOVAL OF MATERIALS

Dismantled materials may be thrown to the ground only after

taking adequate precautions. The serviceable and unserviceable

materials are separated in heaps. It should be lowered to theground through:

Chutes-wooden or metal chutes for the removal-at the centre

of the building for efficient building

Holes in the Floor-without the use of chutes-size should not

exceed 25 per cent of floor area


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1.6 DEMOLITION OF WALLS

Overloading of floors shall be prevented by removing the

accumulating debris

Walls shall be removed part by part

Structural or load bearing members on any floor shall not be cut

or removed until all the storeys above that floor have been

demolished and removed

In framed structures, the steel frame is left in place during the

demolition of masonry work


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1.7 DEMOLITION OF FLOORS

In cutting holes in a floor which spans in one direction, a slit of width not exceeding

300mm shall be cut at the first stage for the entire length of the slab along the way it

spans.

The demolition shall be started only after the floor in question and the surrounding

floor area for a distance of 6m have been cleared of people and debris.

Firm Planks given for the workmen to stand on to guard any unexpected floor collapse


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1.8 RECOMMENDATIONS FOR DEMOLITION OF

PARTICULAR ELEMENTS

Precast Reinforced Concrete - avoid toppling

Suspended floors-floors cut parallel to main

reinforcement

Reinforced Columns-reinforcement exposed at thebase

Reinforced Beams-Support ropes-concrete removed

from both ends by pneumatic drill

Cantilevers-supported or demolished first

Roof Trusses-If a pitched roof-the roof structure to

be removed to wall plate level by hands


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2. Government Clearances

1.1 PLANNING

A careful study of the structure which is to be

pulled down-the manner in which the variousparts of the building to be demolished are

supported and how far the demolition will

effect the adjacent buildings.

A definite plan for the demolition stage wise-

depending on the way the loads are supported


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Demolition Methods


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Oldest Method where a ball weighing up to 13,500

pounds is either dropped or swung into the element to

be demolished. Concrete may be demolished butsecondary cutting may be required.

3.1 BALL & CRANE METHOD


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3.2 DISMANTLING

Cutting elements and then removing with a crane is possible.The

cutting process may be sawing,water jetting or thermic lance.

Because the surface of cut concrete is almost smooth it is useful

when partial demolition required.

3.3 WATER JETS

Water jets reduce dust and eliminates vibration and fire hazardsUsed to cut straight lines and contours and access manholes.

1 inch penetration per minute is possible for RCC slabs.

3.4 THERMIC LANCE

Thermic Lance is created by packing a seamless mild steel tube with

low carbon rods and passing oxygen through the tube.Fusion creating

about 4000 to 7000degree Farenhiet can burn through 12 feet

thick.Rate of 2 to 3 inch per minute.

Vibration and dust reduced but smoke and fire hazards


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3.5 PNEUMATIC AND HYDRAULIC BREAKERS

Used for demolishing bridge decks,foundations and

pavements.

Hand operated and machine mounted types.

Underwater Demolition possible.

Remote controlled machines

Noisy,generate dust and vibrations

Sele ti e Dismantlin of RCC str t re


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Selective Dismantling of RCC structure

using Diamond Cutting Technology

Diamond Cutting technology is over five

decades old.What started as a simple device for the

marble industry in Italy has been perfected

to cut heavily reinforced concrete

structures.

The power of diamond cutting technologyis unlimited and unparalleled.

Diamond Cutting Machineries

Diamond Techniques

1) Flat Sawing

2) Wall Sawing

3) Core Drilling

4) Wire Sawing
http://www.cedima.de/engl/werkz/seil.htmhttp://www.cedima.de/engl/wand/301.htm


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Circular and rectangular openings in RCC

Wall saw being set-up


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3.6 PRESSURE BURSTING

Mechanical and Chemical methods

Mechanical- in expensive, quiet and no

vibration

Chemicals used which cause expansion

internally

3.7 EXPLOSIVES-Implosion

Efficient means to remove large volumes of

deteriorated concrete

Dangerous and hence computer modeling

done to study the failure

Nitroglycerin, dynamite


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In most cases, blowing the support structures on the lower floors is sufficient for collapsing

the building, but loading columns on upper floors helps break the building material into

smaller pieces as it falls. This makes for easier clean-up following the blast.

Implosion of the Athlone Power Stationcooling towers on 22

August 2010.

The basic idea of explosive demolition is quite simple: If you remove the support structure of a

building at a certain point, the section of the building above that point will fall down on the part of

the building below that point. If this upper section is heavy enough, it will collide with the lower

part with sufficient force to cause significant damage.


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REFERENCES

IS CODE 4030 : Demolition of Buildings

Demolition of Concrete Structures by Hal Hudgins, Demolition Specialist

Demolition of Buildings-av

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