CHAN KH Assessing the Effectiveness of Temporary Works for Hong Kong Construction (6954) FIG Congress 2014 Engaging the Challenges, Enhancing the Relevance Kuala Lumpur, Malaysia, 16 – 21 June 2014 1 Assessing the Effectiveness of Temporary Works for Hong Kong Construction Chan KH, Hksar, CHINA Key words: Temporary Works, Bamboo Scaffolding, Metal Scaffolding, Suspended Working Platform, Tower Working Platform. Summary Bamboo Scaffolding (BS) is opined as less safe, highly flexible, lower cost and less durable; whilst possessing fewer established rules to follow or to be controlled in comparing with Metal Scaffolding (MS), Suspended Working Platform (SWP) and Tower Working Platform (TWP). BS may consist of hidden defects that exist in its traditional design and structural form; while the other systems are contended as more rigid/controllable and thus results with lower accidental rate; which may be more adopted by major stakeholders. The central aim of this research is to study the various Temporary Works commonly adopted for alteration and addition projects in Hong Kong; and details the comparison between BS, MS, SWP and TWP in respect of their design, statutory requirements, capacity, material properties, construction method, cost, safety, durability, effectiveness, and security to the building occupiers. Quantitative approach by means of questionnaires is adopted, which will be dispatched to major stakeholders like facilities managers, owners, occupiers, contractors, subcontractors, consultants, and relevant professionals. Collected data will be analysed and cross examined to justify the effectiveness of these systems in view of the critical factors like design, statutory requirements, capacity, material properties, construction method, cost, safety, and durability. Thus, a more precise picture would be drawn to gauge the appropriateness of using each system considering its uniqueness, application, special feature and value for money; for further reference by the industry and academia.
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CHAN KH
Assessing the Effectiveness of Temporary Works for Hong Kong Construction (6954)
FIG Congress 2014
Engaging the Challenges, Enhancing the Relevance
Kuala Lumpur, Malaysia, 16 – 21 June 2014
1
Assessing the Effectiveness of Temporary Works for Hong Kong
Construction Chan KH, Hksar, CHINA
Key words: Temporary Works, Bamboo Scaffolding, Metal Scaffolding, Suspended
Working Platform, Tower Working Platform.
Summary
Bamboo Scaffolding (BS) is opined as less safe, highly flexible, lower cost and less
durable; whilst possessing fewer established rules to follow or to be controlled in
comparing with Metal Scaffolding (MS), Suspended Working Platform (SWP) and
Tower Working Platform (TWP). BS may consist of hidden defects that exist in its
traditional design and structural form; while the other systems are contended as more
rigid/controllable and thus results with lower accidental rate; which may be more
adopted by major stakeholders.
The central aim of this research is to study the various Temporary Works commonly
adopted for alteration and addition projects in Hong Kong; and details the
comparison between BS, MS, SWP and TWP in respect of their design, statutory
requirements, capacity, material properties, construction method, cost, safety,
durability, effectiveness, and security to the building occupiers.
Quantitative approach by means of questionnaires is adopted, which will be
dispatched to major stakeholders like facilities managers, owners, occupiers,
contractors, subcontractors, consultants, and relevant professionals. Collected data
will be analysed and cross examined to justify the effectiveness of these systems in
view of the critical factors like design, statutory requirements, capacity, material
properties, construction method, cost, safety, and durability. Thus, a more precise
picture would be drawn to gauge the appropriateness of using each system
considering its uniqueness, application, special feature and value for money; for
further reference by the industry and academia.
CHAN KH
Assessing the Effectiveness of Temporary Works for Hong Kong Construction (6954)
FIG Congress 2014
Engaging the Challenges, Enhancing the Relevance
Kuala Lumpur, Malaysia, 16 – 21 June 2014
2
Assessing the Effectiveness of Temporary Works for Hong Kong
Construction
CHAN KH, HKSAR, CHINA
1. Introduction
In Hong Kong, most buildings are constructed with reinforced concrete structural
frames, using homogenous tiles for external wall finishing; and resulting in cracking,
debonding, spalling and delamination. During such renovation at building façade,
temporary work such as BS, MS, SWP or TWP are required to provide safe access
for carrying out repair, maintenance, demolition and refurbishment works. BS is
commonly used in Hong Kong, yet its accidental rate is high. The Labour
Department (HKSARLD, 2012) summarizes that 31 fatal accidents relate to the
adoption of BS in recent years. Regarding the high fatality rate of “Person Fell From
Height”, proper selection of temporary works and safety set-up should be considered
at the out-set. The possible causes of accidents will be examined hereof, with respect
to the common practice, construction, cost, safety level and statutory requirements of
these temporary works.
Fig. 1 A Double-row bamboo scaffolding with recommended erection standard
CHAN KH
Assessing the Effectiveness of Temporary Works for Hong Kong Construction (6954)
FIG Congress 2014
Engaging the Challenges, Enhancing the Relevance
Kuala Lumpur, Malaysia, 16 – 21 June 2014
3
Fig. 2 Proper working platform of a double-row bamboo scaffolding
Fig. 3 A Metal Scaffolding
CHAN KH
Assessing the Effectiveness of Temporary Works for Hong Kong Construction (6954)
FIG Congress 2014
Engaging the Challenges, Enhancing the Relevance
Kuala Lumpur, Malaysia, 16 – 21 June 2014
4
Fig. 4 Various types of SWP
Fig. 5 Safety eyebolt of SWP
CHAN KH
Assessing the Effectiveness of Temporary Works for Hong Kong Construction (6954)
FIG Congress 2014
Engaging the Challenges, Enhancing the Relevance
Kuala Lumpur, Malaysia, 16 – 21 June 2014
5
Fig. 6 A typical layout of TWP of fixed type
Fig. 7 A Typical layout of TWP of mobile type
CHAN KH
Assessing the Effectiveness of Temporary Works for Hong Kong Construction (6954)
FIG Congress 2014
Engaging the Challenges, Enhancing the Relevance
Kuala Lumpur, Malaysia, 16 – 21 June 2014
6
2. Literature review
Limited researches have been conducted locally regarding how temporary works are
selected in building renovation. Most studies only stress on technical, material
properties, computer modelling and analysis; but seldom on comparing BS, MS,
SWP and TWP. It is crucial to assess the choice of access equipment, statutory
requirement, common practice, application, construction, installation cost, and safety
levels.
BS is one of China’s oldest construction craft skills created some 5,000 years ago. It
is widely used in the construction industry; reasons being economical, convenient for
erection to accommodate in different locations, and facilitate various construction
processes. For renovation works, a double-row BS is commonly adopted. This
scaffolding consists of 2 layers, with the inner layer at 150-300 mm from building
façade (known as finishing scaffolding) while the outer layer at 700 mm from inner
layer (known as working scaffolding). Working platforms are erected between them.
BS scaffolders always start to erect the two main vertical posts. The vertical member
would be tied by 7 mm-wide plastic tapes with horizontal ledgers. Three standards
(vertical members overhung by ledgers not resting on ground or brackets) will be
erected between the main vertical posts. Standards are tied to building facade by 6
mm mild steel bars. Thus a typical bamboo scaffold in 3m lengths with five bamboo
poles is erected with 750 mm spacing between two adjacent standards.
MS works with the same functions as BS. MS is initially used 90 years ago in
London to support the big tents in circus by SGB – Scaffolding Great Britain in 1913,
which are the originators of steel scaffoldings. In Hong Kong, SGB was operating
since 1981 and had supplied and designed formwork and falsework to some
construction projects. MS are normally designed by a structural engineer, based on
the manufacturer’s specifications and complied with BS5973 and BS1139. To ensure
the quality and safety are fully complied with the requirement and standards, an
Independent Checking Engineer is employed to check the design and site control.
SWP is widely used in Hong Kong as gondolas, to carry site personnel or engineers
for working at height during installation of curtain walls and windows, window
cleaning, façade treatment, bridges chimneys, silos and other structures, etc. It can be
classified as permanent or temporary. The COP covers the safety requirements of
these working platforms suspended by ropes, chains, or lifting gear and capable to
the use and operation of the suspended working platforms as well as the related
supporting activities such as test and examination of the suspended working
platforms.
TWP is a rising and descending platform which is mechanically driven along a lattice
mast made of steel. It is not primarily designed for conveyance of persons. TWP is
used as a temporary working place for supporting workers, materials, tools and
equipment for building refurbishment, renovation, repairs and other construction
CHAN KH
Assessing the Effectiveness of Temporary Works for Hong Kong Construction (6954)
FIG Congress 2014
Engaging the Challenges, Enhancing the Relevance
Kuala Lumpur, Malaysia, 16 – 21 June 2014
7
works. It is designed by a structural engineer, constructed by a registered contractor
and examined by a registered examiner per statutory requirements. The installation
of TWP depends on site situations. The mast section will be rested on ground or sit
on steels to support brackets and secured by wall-tie anchorage. The delivery of
materials on the TWP is carried out at ground level. The material is often placed at
table level with a TWP platform. The material can be loaded to the platform with the
assistance of lifting equipment fixed to platform, this procedure permits short
transport distance of heavy material, which means that the body avoids a long and
static loading per COP on Design and Construction of Tower Working Platforms
(HKSARLD, 2012).
In 2011, totally 28,518 industrial accidents are recorded, including 34 fatal cases. Of
these, 9,026 injuries and 28 deaths happen in construction sites. There is a drop of
22.8% in accident figure and 23.5% in accident rate for the year of 2012 (HKSARLD,
2012). In the first three quarters of 2012, a total of 4900 accidents are recorded,
representing a significant drop of 32% when compared with 7200 in the same period
of 2011 (HKSARLD, 2013).
CHAN KH
Assessing the Effectiveness of Temporary Works for Hong Kong Construction (6954)
FIG Congress 2014
Engaging the Challenges, Enhancing the Relevance
Kuala Lumpur, Malaysia, 16 – 21 June 2014
8
2011
9206
28
80302
114.6
4
0.3
49
2010
11925
29
79599
149.8
1
0.3
64
2009
14078
47
70941
198.4
5
0.6
63
2008
19588
56
79007
247.9
3
0.7
09
2007
18559
41
81629
227.3
6
0.5
02
2006
16469
51
76907
219.8
6
0.6
81
2005
15268
63
65611
232.7
0
0.9
60
2004
16422
51
59710
275.0
3
0.8
54
2003
16573
80
56226
294.7
6
1.4
23
2002
18815
48
62232
302.3
4
0.7
71
No. of
Acc
iden
ts
No. of
Fat
alit
ies
*E
mplo
ym
ent
Acc
.rat
e/1000
Work
ers
Fat
alit
y
rate
/1000
Work
ers
*T
he
emp
loym
ent
size
only
cover
s m
anual
work
ers
on c
onst
ruct
ion s
ites
.
Ta
ble
1 In
du
stri
al
Acc
iden
ts i
n C
on
stru
ctio
n I
nd
ust
ry (
2002 –
2011)
CHAN KH
Assessing the Effectiveness of Temporary Works for Hong Kong Construction (6954)
FIG Congress 2014
Engaging the Challenges, Enhancing the Relevance
Kuala Lumpur, Malaysia, 16 – 21 June 2014
9
Over the past 10 years (2002 – 2011), there has been a very significant reduction in
the number of industrial accidents. However, the accidents toll of working-at-height
is still high. In 2011, 9 out of 28 fatal accidents are identified as “person fell from
height” and over 32% construction fatalities occur by such causes. Furthermore, in
2012, 15 out of 24 fatal accidents are caused by falling from height, with 6 cases
involving BS work, being the highest among recent years. When comparing with the
fatality rate in 2011, it rises sharply from 32.1% to 62.5%; which trigger for a
detailed engineering study for BS towards improving the safety.
Type of Accident No. of
Injury
No. of
Fatalities
Fatality
Rate
Trapped in or between objects 175
Injured whilst lifting or carrying 1350
Slip, trip or fall on same level 1741
Fall of person from height 771 9 (15)* 32.1%
(62.5%)*
Striking against fixed or stationary object 1140
Striking against or struck by moving object 2162 2 7.1%
Stepping on object 123
Exposure to or contact with harmful
substance
77
Contact with electricity or electric discharge 29 4 14.3%
Trapped by collapsing or overturning object 36 9 32.1%
Struck by falling object 346 3 10.7%
Struck by moving vehicle 46 1 3.6%
Contact with moving machinery or object
being machined
621
Drowning 1
Exposure to fire 24
Exposure to explosion 6
Injured by hand tool 420
Injured by fall of ground 5
Asphyxiation 0
Contact with hot surface or substance 94
Injured by animal 0
Injured in workplace violence 0
Others 39
TOTAL 9206 28 (24)* 100%
*figures in 2012
Table 2 Industrial Accident in Construction in 2011
In recent years, tragic accidents relate to temporary works, resulting in horrifying
causalities and fatality. There have been 24 fatal accidents in the industry in 2012.
CHAN KH
Assessing the Effectiveness of Temporary Works for Hong Kong Construction (6954)
FIG Congress 2014
Engaging the Challenges, Enhancing the Relevance
Kuala Lumpur, Malaysia, 16 – 21 June 2014
10
Of them, 15 were caused by falling from height, with 6 involving BS. This is the
highest in recent years. Serious accidents may lead to permanent incapacity or even
death of employees. In addition, most temporary works exist for a long period
without any maintenance. The reasons for such failure are:
General design fault.
Lake of proper inspection.
Workers do not follow the rules of safety.
Insufficient knowledge to refusal of safety equipment.
Lack of proper and regular repair and maintenance.
Existence of unauthorized alteration and/or addition.
Turning to legislation, the relationship between legislation, accident rate and
Temporary Works will be examined. Here below is a summary of relevant COP and
Ordinance.
Hong Kong Regulation, Ordinance and
Code of Practice
Areas of Relevance to Temporary
Works
The Construction Site (Safety) Regulations Bamboo Scaffolding, Metal
Scaffolding, Suspended Working
Platform and Tower Working
Platform
The Factories and Industrial Undertakings
Ordinance
Bamboo Scaffolding, Metal
Scaffolding, Suspended Working
Platform and Tower Working
Platform
Code of Practice on Wind Effects, Hong
Kong, 1983
Bamboo Scaffolding, Metal
Scaffolding, Suspended Working
Platform and Tower Working
Platform
The Factories and Industrial Undertakings
(Safety Management) Regulation;
Bamboo Scaffolding, Metal
Scaffolding,
The Occupation Safety and Health
Ordinance
Bamboo Scaffolding, Metal
Scaffolding,
Code of Practice for Metal Scaffolding
Safety
Metal Scaffolding
Code of Practice for Bamboo Scaffolding
Safety
Bamboo Scaffolding
The Factories and Industrial Undertakings
(Suspended Working Platforms)
Regulation
Suspended Working Platform
Code of Practice for the Safe Use of
Suspended Working Platform
Suspended Working Platform
The Building Ordinance Chapter 123 Suspended Working Platform
Factories and Industrial Undertakings Suspended Working Platform
CHAN KH
Assessing the Effectiveness of Temporary Works for Hong Kong Construction (6954)
FIG Congress 2014
Engaging the Challenges, Enhancing the Relevance
Kuala Lumpur, Malaysia, 16 – 21 June 2014
11
(Lifting Appliances and Lifting Gear)
Regulations
Engineers Registration Ordinance
(Cap.409)
Suspended Working Platform
The Builders’ Lifts and Tower Working
Platforms (Safety) Ordinance
Tower Working Platform and
Builders’ Lift
Code of Practice on the Design and
Construction of Tower Working Platform.
Tower Working Platform
Table 3 Ordinance and COP for Temporary Works in Hong Kong
These regulations are established to protect the construction workers; to ensure
minimum standard of health and safety can be kept. Generally, the statutory
requirements of BS are similar to MS which are monitored/supervised by the
HKSAR Labour Department. In respect of its safety standard, contractors must
comply with Construction Site (Safety) Regulation, Occupational Safety and Health
Ordinance, COP for Bamboo Scaffolding Safety, and COP for Metal Scaffolding
Safety.
The Construction Sites (Safety) Regulations (HKSAR, 2012) mainly regulates the
construction and maintenance of scaffolds; erection, alteration and dismantling of
scaffolds by competent workman under the immediate supervision of a competent
person; the inspection of scaffold by competent persons both periodically and after
exposure to weather conditions likely to have altered the strength or stability of the
scaffold; the provisions of safe access to or egress from the scaffolds and the
precautions for preventing falls from the scaffolds. The general duties imposed by
Section 6A of the Factories and industrial Undertaking Ordinance (HKSAR, 2012)
are also important control measures.
3. Research Methodology
Questionnaire is well prepared to collect relevant primary data for critical analysis,
which will be dispatched to major stakeholders like consultants, contractors,
subcontractors, owners, occupiers and facilities managers to solicit their views of
using temporary works regarding:
The degree of acceptance of temporary works, such as BS, MS, SWP and TWP.
The major considerations in selection of temporary works.
The characteristic of various types of temporary works.
How temporary works are adopted in building renovations.
The scores/points given by respondents will be analysed and tabulated to formulate
consolidated opinions/statement respectively.
4. Findings and analysis of questionnaire
CHAN KH
Assessing the Effectiveness of Temporary Works for Hong Kong Construction (6954)
FIG Congress 2014
Engaging the Challenges, Enhancing the Relevance
Kuala Lumpur, Malaysia, 16 – 21 June 2014
12
62 out of 105 number of questionnaires have been received – a 59% response rate, as
tabulated below.
Category of organisation No. of
responses
% of
responses
Facilities Management & Maintenance 28 45%
Building Contractor 13 21%
Plant & Machinery 8 13%
Safety Consultant 4 6.5%
Government Department 4 6.5%
Others 5 8%
Total 62 100%
Table 4 No. of responses to questionnaire
Most respondents have a high recognition towards BS and SWP; moderate to high
recognition for MS; and less recognition to TWP, especially from facilities
management and maintenance (even 18 out of 28, i.e. 64.3% consider low to
moderate recognition for TWP).
1 To what degree you recognize/accept Temporary Works for external wall
renovation?
Highe
st
High Moderat
e
Lo
w
Lowes
t
Points
1.1 Recognition/acceptance of
Bamboo Scaffolding
21 21 15 5 307
1.2 Recognition/acceptance of Metal
Scaffolding
26 26 10 228
1.3 Recognition/acceptance of
Suspended Working Platform
(Gondola)
12 20 25 5 264
1.4 Recognition/acceptance of Tower
Working Platform
7 32 16 7 170
Table 5 Degree of Recognition of Various Temporary Works
According to the survey, the major considerations for external wall renovation are
level of safety to construction workers, installation cost, effectiveness, statutory
requirements, local control and strengths of materials. Less concerned issues are
security to building occupiers, aesthetic, design and construction method.
2 Major considerations for external wall renovation
Strongl
y
Agre
e
Disagr
ee
Strongl
y
Neithe
r
Point
s
CHAN KH
Assessing the Effectiveness of Temporary Works for Hong Kong Construction (6954)
FIG Congress 2014
Engaging the Challenges, Enhancing the Relevance
Kuala Lumpur, Malaysia, 16 – 21 June 2014
13
Agree Disagr
ee
Agree
Nor
Disagr
ee
2.1 INSTALLATION COST 27 25 5 5 334
2.2 LEVEL OF SAFETY 40 20 2 386
2.3 CAPACITY (e.g. Maximum SWL
& Maximum No. of Persons)
15 25 5 12 257
2.4 EFFECTIVENESS 8 52 2 322
2.5 Adequate STATUTOARY
REQUIREMENT OR LOCAL
CONTROL.
10 45 2 5 311
2.6 STRENGTHS of material. 5 53 4 304
2.7 Degree of SOUND DESIGN AND
CONSTRUCTION METHOD.
35 10 1 16 223
2.8 ABILITY to last for a long time
without deformation (e.g. over 6
months)
4 42 6 4 6 270
2.9 AESTHETIC of Temporary Works
in façade
5 24 16 6 11 226
2.1
0
SECURITY to building occupiers 34 12 12 218
Table 6 Major Considerations for Various Temporary Works
Regarding the merits of adopting Bamboo Scaffolding, there are high scores i.e. 270
points in possibility of reducing installation cost and 302 points in effectiveness in
application, which imply that these 2 considerations are crucial for major
stakeholders; as illustrated below.
1 Advantages of using BAMBOO SCAFFOLDING in external wall
renovation
Highes
t
High Modera
te
Low Lowes
t
Point
s
1.1 Possibility of reducing
installation cost
42 20 270
1.2 Level of safety in application 5 16 26 15 223
1.3 Capacity of such temporary
works (e.g. Maximum SWL &
Maximum No. of Persons)
25 26 11 225
1.4 Effectiveness in application 58 4 302
1.5 Adequacy of statutory 5 15 33 10 229
CHAN KH
Assessing the Effectiveness of Temporary Works for Hong Kong Construction (6954)
FIG Congress 2014
Engaging the Challenges, Enhancing the Relevance
Kuala Lumpur, Malaysia, 16 – 21 June 2014
14
requirement or local control.
1.6 Strength of material 11 36 9 5 186
1.7 Degree of sound design and
construction method
23 20 8 10 201
1.8 Ability for extended use without
deformation (e.g. over 6 months)
10 16 14 15 141
1.9 Aesthetic over façade 9 10 20 15 130
1.1
0
Security to building occupiers 4 22 32 4 154
TOTAL 2061
Table 7 Merits of Adopting Bamboo Scaffolding
Six considerations achieve high score (above 254 points), i.e. level of safety in
application, capacity of Temporary Works, adequacy of statutory requirement or
local control, strength of material, degree of sound design & construction method,
and ability for extended use without deformation; which imply that these 6
considerations are crucial in adopting Metal Scaffolding for major stakeholders; as
illustrated below.
2 Advantages of using METAL SCAFFOLDING in external wall renovation