Unit 4 ( Demolishing Works )

C3001 / UNIT 4 / 1DEMOLITION WORKS

General Objective : To understand demolition works in a safe and

economical manner

Specific Objectives :

At the end of this unit you should be able to:

understand demolition processes.

explain demolition methods.

describe safety precautions taken in demolition of building.

recognize machineries used in demolition.


4.0 INTRODUCTION

DO YOU KNOW?

With the increased number of fatal accidents caused by demolition of high rise

buildings, safety in demolition works becomes a great concern to both the Government

and the public. The reasons leading to such horrible accidents are many, of which the lack

of planning and supervision are the major ones.

Following the issuance of various practice notes to Authorized Persons,

Registered Structural Engineers and Contractors, regarding the safety measures for

demolition works for the protection of the Public, the Building Department has recently

prepared a draft of the Code of Practice for Demolition of Building.


It is intended to be followed by specialist demolition contractors for the

demolition of various building works in Malaysia, aiming at minimizing the risks of

injury to persons and damage to properties, the risks of endangering the health and safety

of site personnel and damage to the environment in the vicinity.

The Code sets out the guidelines for demolition of the buildings from roof level to

ground level and the demolition of basement, underground tanks, as well ascertain

common civil engineering structures, but not major civil engineering works such as

underpinning, excavation, highway bridges, dams and nuclear reactors.

General guidelines are also given for the design of temporary works and checking of

temporary structures. The code covers common methods typically used in the demolition

of buildings in Malaysia, but exhaustive guidelines for all methods are not given. The

code does not intend to discourage any other demolition methods, which may be used

subject to approval. The content of the unit includes the following topics:

Demolition Processes

Demolition Methods

Machinery used in demolition


4.1 Demolition Tariffs And Reasons For Demolition

Rina , what is the meaning of “Demolition” ?

Based on the Oxford Fajar dictionary demolition means to “ pull to or knock down a building ”, and another meaning for demolition is a “ highly skilled and dangerous activity in terms of damage to life and property”.


Does anybody know the causes of

demolition?

4.2 Causes Of Demolition

No…sir

??????

It’s ok, let me tell you about the causes

of demolition, the example are:

Commercials

Aesthetic

Human health

Human safety

Building new buildings

Renovation

Structure problems

Environment ( near slopes )

Population density

Adjacent buildings

Traffic


Demolition Processes

1. Before demolition

a. identify site locations, special site restrictions and impact of special

buildings

b. identify buildings/structures to be demolished

c. verify dimensions of site and building

d. identify hoardings requirements

e. verify building construction, types of materials

f. verify existing fixtures

g. verify the building use

h. verify utilities location

i. prepare demolition schedule

j. test and remove hazardous materials

Let us list together the demolition processes


k. identify the safety measures for protection of the public

l. arrange for debris handling

m. prepare demolition plan

n. prepare stability report with calculations

o. apply consent (also submit supervision plan, names and details of

Technically Competent Persons.

2. During demolition

a. install site precautionary measures

b. remove hazardous materials

c. inform site personnel the specifics and precautionary measures

d. establish emergency access

e. establish line of communication to supervisor

f. progress work in accordance with method statements approved.

g. remove debris to avoid accumulation

h. control dust emission

i. adequate supervision

j. protect party walls

k. ensure workers follow safety procedures

l. ensure machines and equipment are well maintained.

m. provide security

n. schedule regular inspection and maintenance of scaffolding.


3. After demolition

a. clear debris and level site

b. secure boundaries

c. protect all excavations

d. for sloping site and/or site with retaining wall

i. seal ground surface

ii. provide surface drainage

iii.provide demolition plan to the foundation contractor for

maintaining the supports.

Let’s answer the questions in the next activity to test

our knowledge.


State whether the following questions are

True or False.

1. Commercials, aesthetic, human

health, human safety, build new

building are the example of the

causes of demolition.

2. Demolition processes have 3

situations; it is before, during and

after.

3. Demolition means to “ pull to or

knock down a building ”, and

another meaning for demolition is

a “ highly skilled and dangerous

activity in terms of damage to life

and property”.


4.2 Types And Ways Of Demolition

In many circumstances, buildings and structures should be demolished in the

reverse order to their erection; although where partial demolition is involved a more

careful evaluation of the nature of the effects of the demolition is necessary.

Normally, the demolition contractor is able to adopt a method of work which:-

1. True

2. True

3. True


gradually reduces the height of the building; or arranges the deliberate controlled

collapse of the building or structure so that work can be completed at ground

level.

The choice of demolition technique will depend on the nature of the building or

structure and its environment. Risks to the public, operatives involved in the demolition

process and adjacent structures and buildings should be considered.

Demolition techniques may be categorized as:-

Piecemeal demolition, using hand-held tools or machines, to reduce the height of

the building or structure gradually;

Deliberate controlled collapse, demolition to be completed at ground level.

4.2.1 Manual

Demolition of buildings or structure by hand-held tools such as electric or

pneumatic breakers, sometimes as a preliminary to using other methods, should be

carried out, where practicable, in the reverse order to the original construction sequence.

Lifting appliances may be necessary to hold larger structural members during cutting and

for lowering severed structural members and other debris. Chutes may be used to


discharge debris into a vehicle or hopper. Foundations would normally be grubbed up by

excavation machines.

Figure 4.1 demolition by hand

4.2.2 Machinery’s Components

Simple roof structures supported on wall plates should normally be demolished to

the level of wall plates by hand, but if this may involve unsafe working, then demolition

totally by machine may be appropriate.


Where a building that is to be demolished by machine is attached to another

structure, the two properties should be separated by the use of hand methods before the

main demolition process begins.

When any part of a building is being demolished by a balling machine, pusher

arm or similar equipment, only the machine operator and banks man should be allowed

close to the working area. The cabs of all machines should be strong enough to protect

the operator against the fall of debris. In particular, the windscreen and roof light should

be of shatterproof material and guarded by a grille of steel bars or a substantial mesh.

Figure 4.2 Demolition by machinery’s components

4.3.2.1 Balling machine

Balling machines generally comprise a drag-line type crawler chassis fitted with a

lattice crane jib. The demolition ball, with a steel anti-spin device, is suspended from the

lifting rope and swung by the drag rope.


Balling should only be carried out by skilled operatives under the control of

experienced supervisors using well maintained machines adequate for the proposed duty

and standing on a firm, level base.

The manufacturer should be consulted before a machine is used for balling to

establish any restrictions on the type or length of jib or the weight of the ball.

Balling operations subject cranes to dynamic stresses and wear, and the ball

chosen should have the minimum weight necessary for effective use. In many cases,

demolition balls of quite light weight will be adequate.

Floors should be demolished by dropping the ball on the highest remaining floor

and allowing the debris to fall inside the building. The debris should be removed

regularly to prevent excessive weight accumulating on the lower floors.

Walls or columns can be demolished either by swinging the ball in line with the

stationary jib, using the drag rope, or by slewing the jib. The ball should not swing by

derricking the jib.


Figure 4.3 Demolition ball

Figure 4.4 Demolition ball


Figure 4.5 Ball crane




4.3.2.2 Hydraulic pusher arm

Articulated, hydraulically-powered pusher-arm machines are normally mounted

on a tracked or wheeled chassis, and have a toothed plate or hook for applying for

applying a horizontal force to a wall. The machine should stand on a firm level base and

apply force by a controlled movement of the pusher arm.

Figure 4.8 Hydraulic Breaker

Figure 4.9 Mini Hydraulic Breaker Figure 4.10 Hydraulic Mobile crane

( 20 T - 200 T )


4.3.2.3 Long arm excavator

Figure 4.11 Long Arm Excavator

Figure 4.12 Long Arm Excavator


4.3.2.4 Dynamite

If explosives are to be used for demolition, the planning and execution, include

pre-weakening, should be under the control of a person competent in these techniques.

For large demolition, the competent person is likely to be an experienced explosive

engineer; for smaller work, a shot-firer may be sufficient.

When the use of explosives is contemplated, it is usual to employ a technique that

will ensure the total demolition of the whole building by staging a controlled collapse.

The explosive charges are set and fired in a sequence that will weaken the structure in

such a way that the building collapses in upon itself.

Although we tend to think of explosives as devices producing spectacular bomb-

like explosions, the use of non-explosive "explosives" is now at an advanced stage. These

non-explosive techniques are essentially expanding charges that achieve the same results

as explosives but without the noise and initial devastating blast.

“Did you understand all the information in this

unit? If you have difficulties go through the notes

again. Now let us answer the question in the next

activity”.


Complete the sentences below by providing the correct answers.

1. Demolition means…………………..

2. Demolition techniques may be

categorized as ………………

3. Manual and Machinery components are

………………………

4. List the machinery’s components.

Write your answers in the space below.

a) ………………………….

b) ………………………….

c) …………………………..

d) …………………………..

5. Who should be allowed close to the

working area?


1. Based on the Oxford Fajar dictionary Demolition means to “pull or knock down a building”, and another meaning for demolition is a “highly skilled and dangerous activity in terms of damage to life and property”.

2. Demolition techniques may be categorized as:- Piecemeal demolition, using hand-held tools or

machines, to reduce the height of the building or structure gradually;

Deliberate controlled collapse, demolition to be completed at ground level.


3. Manual and machinery components are ways of

demolition

4. a) balling machine

b) hydraulic pusher arm

c) long arm excavator

d) dynamite

5. The machine operator and banks man should

be allowed closed to the working area


Answer the following questions:

1. Give FIVE of the most important safety precautions which must be

taken into account before starting a demolition project to prevent your

actions from undermining the structural integrity of the building?

2. Give THREE proper attire and tools needed to ensure a safe

environment in a demolition project?

3. Give FIVE steps that need to be taken to ensure the homeowner’s

safety.

4. Explain how to schedule the best time to start a demolition project.

5. List three examples of Machinery’s Components.


ANSWER NO. 1

Always know exactly what it is you're about to remove. Before you move or

remove anything, always check to see what's behind it, below it and what it might

support.

Never assume that a structural member you're about to remove doesn't support

anything

When removing framing that is near electrical wiring, shut off the electricity, even

if you're not removing the wiring. Do the same for any plumbing or gas lines. A

single nick with a saw blade or a drill can cause disastrous results.

When removing electrical wiring, turn off the circuit breaker or remove the fuse

controlling the circuit you're working on, and then post a note on the electrical

panel warning others not to turn it back on.

Never attempt to work on a gas or water line without first making certain it has

been shut off. Also, do not assume that a shutoff valve works - after closing the

valve, test the line to be absolutely sure it's off.


ANSWER NO. 2

Use only the proper tool that is designed for a particular task - don't improvise. If

you are prying up a board, use a heavy pry, not a big screwdriver. On the other

hand, use a screwdriver to remove a screw; don't yank it out with a pry bar.

If you don't have the proper tool for the job, don't proceed until you are able to

buy or rent one. If you need a jack to lift a heavy beam, get one - don't try to rig

up a couple of 2 X 4 as a lever. If scaffolding is required to work safely at a given

height, get some and take the time to set it up correctly - balancing a 2 X 12 on a

couple of ladders is an invitation for disaster.

Wear the appropriate clothings. Demolition work requires long pants, a heavy

shirt, and solid shoes - allowing your crew to work in shorts and tennis hoes can

net you a serious fine. Wear gloves, and always wear eye protection. If anyone is

working above you, or if there is any potential for falling objects, make hard hats

mandatory.


ANSWER NO. 3

Secure all tools at lunchtime, at the end of the day, and during absence from the

job site, cords need to be unplugged and sharp tools placed in a safe and secure

enclosure. Remember that children are fascinated with construction sites, and this

curiosity can lead to serious injuries.

Motorized equipment needs to be securely locked and the keys placed in a safe

locked area.

Take down ladders at the end of the day. This includes covering holes in the floor

and placing temporary barricades over window and door openings.

If you cannot cover or otherwise close off an area - such as an open trench that is

still in use - ring the area with caution tape and place lighted barricades at regular

intervals as a warning.

Cover holes and other danger spots.


ANSWER NO. 4

In most cases, demolition work is best left until the last possible moment in order

to help avoid weather and security problems. The addition should be completely

framed, roofed, and enclosed with siding, and exterior windows and doors should

be installed, before the walls connecting the addition with the existing house

should be removed.

Try to work in stages as much as possible, again doing only as much demolition

work as necessary for a particular phase of the construction. You may, for

example, need to remove a small section of siding at the base of the wall in order

to align the new foundation with the old one, or perhaps take down some drywall

to line up the new ceiling joints.

Even if it's all coming down eventually, it's best to remove only what you need to

accomplish the task you are working on at the moment.

ANSWER NO. 5

Long arm excavator

Hydraulic pusher arm

Balling machine

Unit 4 ( Demolishing Works )

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