Safety and Risk Management in Scaffolds and

Transcription

Copyright Profesor N. Krishnam
murthy :: www.profkrishna.com
Coverage of Talk
N. KRISHNAMURTHY
27 Mar.
2014
SAFETY CONSULTANT AND TRAINER
Website: www.profkrishna.com
1
1.Similarities and differences between scaffolds and
formwork structures
2.Why temporary structures are more critical than
permanent structures
3.Case studies of scaffold and formwork structure accidents
4.How risk management can be used to reduce scaffold
and formwork failures
Acknowledgements and References
1. Mr. Tan Kai Hong for certain information and pictures of workplace
accidents.
2. “Case Studies of Construction Industry”, WSH Council, Singapore, June
2008, 116p.
3. “Formwork and Scaffolding Collapses”, IMIA Working Group Paper
WGP 80 (13), IMIA Conference, New Delhi, India, 21-25 Sept. 2013.
“It is better to be careful a hundred times
than to get killed once.” – Mark Twain
2
Scaffold and Formwork Structure
 Scaffold & falsework are similar, structurally & functionally
1.
Similarities and Differences
between Scaffolds and
Formwork Structures
Formwork Structure (=Formwork + Falsework) 3
4
Scaffold & Formwork Structure Differences
 If we consider the pure formwork part as mould for wet
Scaffold & Formwork Structure Similarities
concrete until it hardens, the comparison may be limited
to scaffolds and falsework, i.e. the support for formwork.
 Similarities:
 Both are temporary structures
 Both bear loads during construction of permanent
structures
 Both will be reused a number of times for short periods
 Both are susceptible to incidents and accidents
 Both involve working at height
 Both are given the same secondary importance
compared to permanent structures
 Both need special design, fabrication, inspection,
maintenance and supervision to be safe
5
 Scaffolds bear weight of persons and tools (and
occasional supplies), while falsework must bear the
much heavier weight of wet concrete and its formwork.
 Scaffolds bear mostly static loads, while falsework must
bear widely variable dynamic loads in addition.
 Scaffold is
dry work
while form
formwork is wet
work.
 Rescues
must be
made
before
concrete
sets.
6
1
Permanent vs. Temporary Structures
2.
Why temporary structures
are more critical than
permanent structures
Permanent vs. Temporary Structures
 Are not used – or even seen – by the ultimate customer
 Have often built-in compromises in quality and strength
 Are put together at site from numerous components
 Most components
p
are already
y used and some damaged
g
 Are erected generally by less skilled temporary workers
 Are not checked as rigorously or as frequently
 Are not inspected as meticulously
 Are not supervised as strictly
 Are not maintained as well
 Do not have their faults rectified as promptly or fully
 Are the first to compromise on safety when time or
8
The handicaps of being ‘temporary’
 Unlike permanent structures, temporary structures …
 Do not have assured or well-prepared foundations
 Are not designed as well or in as much detail
budget presses hard
7
 Do not have assured or well-prepared foundations
 Are not designed as well or in as much detail
 Are not used – or even seen – by the ultimate customer
 Have often built-in compromises in quality and strength
 Are put together at site from numerous components
 Most components
p
are already
y used and some damaged
g
 Are erected generally by less skilled temporary workers
 Are not checked as rigorously or as frequently
 Are not inspected as meticulously
 Are not supervised as strictly
 Are not maintained as well
 Do not have their faults rectified as promptly or fully
 Are the first to compromise on safety when time or
budget presses hard
 Unlike permanent structures, temporary structures …
9
 Temporary structures cannot be a line-item to customer.
 The word ‘temporary’ suggests that:
 We can get by with compromises, deficiencies, and
even occasional violations
 Fact: As the ultimate user is not around and the public
does not see temporary structures, accidents are
more likely to happen, and any flaws may have farreaching adverse effects
effects.
 We can occasionally subject the structure to temporary
over-loads.
 Fact: This implies over-stressing the material which
may not be put together in the correct fashion, and
which may already be damaged or yielded in even
hidden locations.
 Inexperienced people can design and erect them.
 Fact: Temporary structures need more expertise!
10
and falsework in particular – are as follows:
 Design by site staff who may not have the necessary
design background to be doing it;
 A general view that temporary work should be designed
by the more junior staff (such structures not deserving
the serious attention of 'real' structural engineers);
 ‘Design-in-a-hurry’
‘Design-by-guess’;
‘D i i
h
’ or ‘D
i b
’
 Insufficient consideration of possible accidental loads;
 Careless assembly;
 Lack of proper quality control, or quality control by
personnel with insufficient experience of temporary
work and the realities of site operations;
 Overloading of temporary work by personnel who do
not understand these matters.
 Adapted from: http://www.eng-tips.com/viewthread.cfm?qid=22666
11
Increased Risks in Temporary Structures
 The increased risks in temporary structures – formwork
3.
Case studies of scaffold
and formwork structure
accidents
12
2
Fall from Mobile Scaffold, 2/7/2002
Fall from Scaffold, 21/4/2001
 Two workers were wet-
ting 4th storey RC beam
for skim coat, with one of
them walking backwards
on the work platform.
 Either the worker fell
while working or while
climbing
li bi d
down.
 Guardrails at the two
ends were only secured
on one side to allow
access from the ends.
 No access ladder.
 Subcontractor’s partner
fined $9000, and occupier
fined $5000
Fall from scaffold, 18/4/2004
fallen with the mobile
tower from 4th storey to
the ground floor and died.
 Mobile tower’s
Height/Width ratio = 4.3
(>3)*, not tied, legs on
uneven floor, hence
unstable.
 No supervision during
erection** and use
 Occupier fined $18,000
for*, and $15,000 for **.
14
 3 workers dismantling
external scaffolding
 When leaving for lunch
break, one fell from scaffold, hitting worker already
on the ground, and died.
 Safety
y harness worn but
had been disconnected
from lifeline for descent.
 Supervisor not present.
 Deceased and one other
worker had no work at
height training, and were
not certified for rigging.
 A worker tidying up metal scaffolds fell down and died.
 He had safety belt on, but had no anchor of lifeline to
clamp it to. None of them was trained.
15
16
10th
storey worker
fell on to scaffold platform through openings on all floors.
 Supervisor did not actually check work area for hazards.
 Worker not wearing safety
harness; not attended SCOC*
 Occupier & Site Mgr., $18K
for no SWP+Occ.$2K for no*
17
Scaffold Collapse – 23/10/2004
Fall from Height, 3/7/2004
 He appeared to have
13
Fall from Scaffold, 6/6/2003
 While getting ready for painting work at
 Worker instructed to install ‘bonding bars’ at duct area
 One worker killed.
 No supervision
 Design flaw – inadequate training – no Risk Assessment
 A simple tie would have been enough to prevent the fall
18
3
 Worker fell 9
storeys & died.
 He was not
wearing safety
belt or harness.
 Scaffold had not
been checked
and
d certified
tifi d for
f
3 years.
 No Risk Assess.
 No SWP
 No safe access
plan
 Inadequate
safety training
 Fines: $25K & $40K
Table Form Mishandling, 15/5/2005
Fall from Scaffold – 9/5/2005
 While workers were shif-
ting table form from Floor
15 to Floor 18, obstructed by overhead beam.
 Worker separated table
form into two parts and
started pushing it.
 It hit some planks,
toppled and killed the
worker.
 Did not follow safe work
procedure
 No guidance at site
 No supervision
19
20
Fall from Scaffold
Mobile Scaffold Collapse – 7/2006
 Mobile scaffold fell over
worker during shifting
 Worker killed
 Scaffold may have
struck obstruction
during shifting, and
pp
it.
momentum toppled
 No proper planning
 No RA
 No supervision
 Worker tasked to paint
roof elements under
roof of 6-storey building
 He fell off the scaffold
work platform and died.
 No guardrails around
p
work platform
 No proper access to
working platform
21
22
Fall from Suspended Scaffold
Fall from Scaffold
 Worker tasked to dis-
mantle metal platform
fell 4.5m to the ground
and died.
 No proper access
 No risk assessment
 Required PPE not
provided
23
 Worker intending to paint walls adjacent to a ledge tried to
climb out of a suspended scaffold onto the building ledge
but lost his footing and fell from the 9th storey, died.
 No RA, no PPE
 No supervision
24
4
 Scaffolds are generally for workers and tools while
falsework is for formwork, and concrete casting loads
 Scaffold live loads are of the order of 1.5 to 2kN/m2, while
falsework live load is mainly concrete weighing 25kN/m3,
which even for 300mm depth slab is 7.5kN/m3.
 Scaffold work is generally dry, static work, while falsework
wet dynamic work of concrete casting and
is subject to wet,
vibration, with very hazardous materials which will set
hard within a short time.
 Scaffold erection is relatively better organised and more
visible at all times than falsework which involves more
components and variable sizes, and more adjustments
and actions.
 Scaffold failures may generally be localised while formwork/falsework collapse can be massive and progressive 25
Formwork Failure, 7/1/1999
Why must we be stricter with
formwork/falsework than with scaffolds?
assessment
done
27
 Compassvale Primary School
 Seven workers injured
 Overloading during concreting
 Inadequate supervision
Formwork Failure, 23/4/2001
29
 There were inadequate bracing in shoring system
28
Demarcation of heavy loading zones
 Zones designed for heavy loading must be demarcated.
 The formwork structure was not designed by PE
Formwork Collapse – 15/6/1999
supervision
 No risk
 Dead load of collapsed beam in excess of 2160Kg/m2
26
Formwork Collapse – 15/5/1999
 NIE Complex, collapsed Saturday
 Not scaffold as reported but formwork
 Five workers fell 8m, badly injured but survived
 Rush job, at night and during weekend
 Not enough
 Condominium transfer beam collapsed while being cast
 Vehicular ramp for a 6-storey industrial building collapsed
at the sloped portion. Ramp was supported with conventional steel frames.
 Lack of diagonal bracing
 Defective & deformed members reduced loading capacity
30
5
 Formwork panel fixed at
16th storey, fell to ground,
killing site supervisor and
worker on it.
 It had just been shifted
from 15th storey by tower
crane.
 Bracket not secured to
support.
 No RA or SWP for the
modified system.
 No safety training record
 Subcontractor fined
$160,000
Fall from Formwork – 11/2005
Formwork Collapse, 19/11/2004
 No proper supervision
 No RA
Viaduct, Portugal, 2010
 No edge protection
32
Bridge Formwork Collapse, Poland, 2009
buting to collapse:
 The main cause was
 Whole length of fresh concreted section of deck, together
with supporting structure collapsed at once during pouring
 One dead, 8 injured
 Uneven load distribution during pouring of the concrete
33
34
Formwork Panel Failure
BUGIS MRT Incident, 19/7/2013
 Fell 8m
31
 Two factors contri-
lack of bracing to
adequately counter
lateral forces.
 Large quantities of
reinforcing bars were
temporarily stored on
the bridge deck.
 These bars
imposed a load not
considered in the
falsework design.
 Collapse similar to
Fusionpolis in S’pore
 Worker plunged to death through opening in formwork
 Formwork collapse
 2 dead, 9 injured
 The company allegedly failed:
 To ensure that the formwork
structures were inspected
and certified by a
professional engineer
before the placement of
concrete, and,
 To ensure a formwork
supervisor regularly
inspected the structures.
35
 Formwork wall panel gave
way; worker fell 6m, and
panel fell on him, killing him.
 Foreman knew top tie rods of
panel had been removed but
did nothing about it.
36
6




control lever for hopper to dump concrete in formwork.
Cage caught on a re-bar, dislodged and hit another rebar,
and fell 20m with worker, killing him instantly.
No securing device to prevent accidental dislodgement.
No risk assessment
No proper SWP
Bracing, a most critical element
Fall from Concrete Hopper
 Worker was riding cage attached to hopper to release
37
 Many scaffold and falsework failures are due to missing
or inadequate
bracing.
 Mere horizontal bracing
completely
useless to
prevent sway
 Unless one or
both ends are
prevented
from moving
 Buckling will
reduce capacity
to a fraction of
designed value!
?
Is this unsafe act
by worker
or unsafe
condition
by management?
THE RIGHT WAY
Ladder and
Fall
Prevention
by Travel
Restraint
No need
for body
harness
Give Everybody Body Harness?
Unsafe Act or Unsafe Condition?
38
39
1. As PPE, it is the least effective control, to be chosen after all
other controls have been explored & exhausted
Cannot be used below about 5.5m (‘Fall Clearance’)
Need well-designed anchors, and correct anchoring.
Must fit the user, and must be stocked in various sizes
Must be worn correctly, if loosely worn, can be injurious
Must be used correctly, with 100% tie-off
Much more costly than other PPE
Needs more training,
training better maintenance
maintenance, and more
supervision, than other PPE
9. Introduces fresh hazards like hitting objects during fall
10. Needs a prompt and proper on-site rescue system
 Otherwise, death by suspension trauma likely
11. Make the all-day wearer very uncomfortable
 Causing him to make mistakes, and/or
 Reducing productivity (– will discard!)
2.
3.
4.
5.
6.
7.
8
8.
USE ONLY WHEN AND WHERE REQUIRED BY CODE!
 More in author’s paper on body harness in his website
40
4.
How risk management can
b used
be
d tto reduce
d
scaffold
ff ld
and formwork failures
41
Causes of Scaffold/Formwork Failures
 No or improper risk assessment
 Inadequate or incomplete design for the actual loading
 No or inadequate bracing
 Inadequate implementation of design in erection
 Loading of unstable structure
 Overloading of structure
 Lack of training of supervisor/worker and/or SWP
 Worker not following SWP (i
(i.e.
e Supervisor
Almost
all
Al
ll
not ensuring that SWP is followed)
these are
 No proper access/egress
failures of
 Work platform not provided guardrails
existing
 Worker not given proper PPE
controls!
 Worker not wearing or correctly using PPE
 Worker not given proper anchorage for harness
 Worker not anchoring harness to available anchor
 No or inadequate supervision
42
7
appointed in writing with a detailed work scope;
 PE shall comply with Part IX of the WSH (Construction)
Regulations 2007, and make reference to the Singapore
Standard 580:2012 (or any revision thereafter) and the
various formwork guidelines published by WSH Council;
 All formwork structures shall be capable of sustaining the
total dead load
load, live load and impact load imposed on the
formwork structures with a minimum safety factor of 2;
 PE shall ensure that his design can be executed safely by
any person who constructs or uses the formwork struct.;
 PE should ensure that he is competent in the use of any
proprietary formwork system used in his design; and
 Mix-and-match of formwork systems and components
should be avoided. If unavoidable, PEs shall ensure that
overall strength & integrity of such systems are retained.
SS580:2012 – 9.1 Risk assessment
Design of Formwork Str. (MOM – 18/1/2014)
 PE appointed to design any formwork structure should be
 A risk assessment specific to the project shall be
conducted to identify hazards prior to commencement of
the formwork activity.
 By assessing the risks that may occur, appropriate risk
control measures can be undertaken so that reasonably
practicable measures can be taken to eliminate or control
the risks arising from such hazard.
 The risk assessment and control measures shall be
documented in a risk register and the information made
available.
 Other vital information on safety, design, erection,
transfer, alteration and dismantling shall be included in
the risk register to ensure complete documentation and
enable effective communication of the risks and controls
to parties involved, and for inspection by authorities.
43
44
 Risk management, to eliminate risks or mitigate their
effects, consists of three steps:
 Hazard identification
 Assessment of risk from likelihood
and severity, by risk matrix
 Risk control according to recommended hierarchy
 Most of the accidents in Singapore have been declared to
be due to lack of an adequate risk assessment
assessment, meaning
the safety team had not identified or controlled some risk.
 Use risk management principles to cover hazards beyond
conventional harm to health, such as the ones listed:
 Structural weaknesses
Almost all
 Construction flaws
these are
 Worker behaviour errors
failures of
existing
 Supervision deficiencies
controls!
 Safety violations
45
Risk Management in Practice
Risk Management
 We know the hazards in scaffold and formwork accidents
 We know the existing controls to eliminate these hazards
or to mitigate their effects.
 We provide enough safeguards, PPE, and training to
implement the controls.
 What we lack is supervision to ensure that these
are actually
and followed by
safeguards
g
y implemented
p
y all
concerned, at all times the work is taking place.
 Increased and tighter supervision is the key to improved
safety – more than new rules. (Means more inspection!)
 Supervisor should be alert to any deviations from
standard practice and specs, and report any significant or
potentially dangerous problems when he finds them.
 Incident reporting is now mandatory, as per the WSH Act
(2006), Incident Reporting Regulations.
46
Almost all
scaffold
and
formwork
accidents
are
failures
of
existing
controls!
CoP Appendix C. Risk Assessment Form
SOLUTION?
1. Tighten up existing
controls through normal
compliance regime of
inspection, maintenance,
and supervision.
2. In recognition of special
problems with immigrant
labour, provide additional
continuous supervision
47
The End
48
8

Safety and Risk Management in Scaffolds and

Transcription

Similar documents

Big River Formwork Brochure

formwork

BIRAMAX Catalogue, Adjustable circular formwork

Formwork for Concrete - American Concrete Institute

FRENOS Y EMBRAGUES

Homebuilder Scaffold Catalog

Kaloyana Kostova MEng CEng MICE Department of Architecture