1Cop

yrig

ht P

rofe

sor N

. Kris

hnam

urth

y ::

ww

w.p

rofk

rishn

a.co

m

1/48

15 Nov. 2012

N. KRISHNAMURTHYSAFETY CONSULTANT AND TRAINER

Website: www.profkrishna.com

Safety Aspects of Formwork

Cop

yrig

ht P

rofe

sor N

. Kris

hnam

urth

y ::

ww

w.p

rofk

rishn

a.co

m

2/48

Case Studies

2Cop

yrig

ht P

rofe

sor N

. Kris

hnam

urth

y ::

ww

w.p

rofk

rishn

a.co

m

3/48

New York Coliseum on May 9, 1955 The main exhibition floor of the New York Coliseum

collapsed when concrete was being placed. 8 motorised buggies with concrete ran at 12 mph (19

kmph) each weighing 3000lb (13kN) Rapid delivery Inadequate resista-

nce to lateral forces. If there had been

sufficient bracing, collapse could have been prevented entirely "

https://failures.wikispaces.com/Concrete+System+Collapses+%26+Failures+During+ConstructionSecond time!

Cop

yrig

ht P

rofe

sor N

. Kris

hnam

urth

y ::

ww

w.p

rofk

rishn

a.co

m

4/48

2000 Commonwealth Avenue: January 5, 1971 a Progressive collapse

of a cast-in-place R.C. flat-slab structure due to punching shear as triggering mechanism.

Real problem was in numerous errors and omissions by every party involved in project.

If construction had had proper building permit and had followed codes, failure could have been avoided.

https://failures.wikispaces.com/Concrete+System+Collapses+%26+Failures+During+Construction

3Cop

yrig

ht P

rofe

sor N

. Kris

hnam

urth

y ::

ww

w.p

rofk

rishn

a.co

m

5/48

2000 Commonwealth Avenue: January 5, 1971 b Not following structural engineers specifications for

shoring and formwork Lack of concrete design strength Lack of shoring or removed too soon Improper placement of reinforcement Little construction control on site Owner changed hands many times Almost all jobs were sub-contracted No architectural or engineering inspection done Inadequate inspection by the city of Boston General contractors representative was not a licensed

builder Construction was based on arrangements done by the

sub-contractors No direct supervision of sub-contractors

Cop

yrig

ht P

rofe

sor N

. Kris

hnam

urth

y ::

ww

w.p

rofk

rishn

a.co

m

6/48

Skyline Plaza: March 2,1973 a Catastrophic collapse of 30 storey cast-in-place R.C.

also a flat-plate design structure failing in punching shear on 23rd floor resulting in progressive collapse.

Forms were supported by floors 7-days old or older.

Failure occurred on the 24th floor, where it was shored to the 5-day-old 23rd floor.

Causes of failure:1) Premature removal of shores

and reshores, 2) Insufficient concrete stength, 3) No plans of casting, form-

work erection or, removal, or reshoring

4Cop

yrig

ht P

rofe

sor N

. Kris

hnam

urth

y ::

ww

w.p

rofk

rishn

a.co

m

7/48

Skyline Plaza: March 2,1973 b Lessons Learned

1) Contractor should prepare formwork drawings showing details of formwork, shores, and reshores.

2) Contractor should prepare detailed concrete testing programme, to include cylinder testing, before stripping forms.

3) Engineer of record should ascertain that the contractor has all the pertinent design data (such as live loads, superimposed dead loads, and any other information which is unique to the project).

4) Inspectors and other quality control agencies should verify that items 1 and 2 above are being adhered to.

5) Uncontrolled acceleration of formwork removal may lead to serious consquences.

6) Top and bottom rebars running continuously within he column periphery must be incorporated in the design.

Cop

yrig

ht P

rofe

sor N

. Kris

hnam

urth

y ::

ww

w.p

rofk

rishn

a.co

m

8/48

Tropicana Casino parking garage in Atlantic City, N.J.: October 30, 2003

The structure collapsed during construction killing four construction workers and leaving more than 30 injured.

Floors were not connec-ted to walls with required reinforcing steel.

Built without necessary steel, it is no wonder it collapsed like a house of cards.

https://failures.wikispaces.com/Concrete+System+Collapses+%26+Failures+During+Construction

5Cop

yrig

ht P

rofe

sor N

. Kris

hnam

urth

y ::

ww

w.p

rofk

rishn

a.co

m

9/48

Spore Worker falls with toppled formwork, 2006 On 3 Aug 2006, toppling formwork

resulted in tragic death of a young construction worker.

While setting up barricades at edge of a table formwork on third storey, worker fell to ground as formwork collapsed.

LESSONS LEARNED:1. Prior to work commencement, risk

assessment should be conducted.2. SWP and PTW to be implemented and communicated3. Formwork must be stable during all stages. 4. No person should work on table form during adjustment. 5. If possible installation of barricades at height should be

eliminated by installing barricades in building or at G.L. If unavoidable, proper PPE for work at height given

6. Workers should be instructed and closely supervised.

Cop

yrig

ht P

rofe

sor N

. Kris

hnam

urth

y ::

ww

w.p

rofk

rishn

a.co

m

10/48

S. Construction Worker Died of Heat Stroke, 200716 Apr 2007 A construction worker, collapsed while dismantling the

timber formwork at a construction worksite under the hot sun.

He came from a temperate country and had started work two days after arrival.

He was admitted to hospital and died of complications from heat stroke the following day. ?

6Cop

yrig

ht P

rofe

sor N

. Kris

hnam

urth

y ::

ww

w.p

rofk

rishn

a.co

m

11/48

Singapore Worker Falls from Formwork, 20083 Nov 2008 A worker was working on the formwork of a 2-storey

detached house. While receiving a reinforcement bar from another

worker, he lost his balance and fell off the formwork to the ground 9.8m below. He died.

Cop

yrig

ht P

rofe

sor N

. Kris

hnam

urth

y ::

ww

w.p

rofk

rishn

a.co

m

12/48

Singapore Worker Falls from Formwork, 2009 On 13 Feb 2009, a worker fell to his death when he was

using a chain block to lift a wall formwork into position. During the lifting, he was standing on top of formwork to

operate chain block. At the time of the

accident, one of the wire sling ropes used for rigging gave way, causing both the formwork and worker to fall.

He fell 3m onto the floor slab below and died.

7Cop

yrig

ht P

rofe

sor N

. Kris

hnam

urth

y ::

ww

w.p

rofk

rishn

a.co

m

13/48

Singapore Case StudyC

opyr

ight

Pro

feso

r N. K

rishn

amur

thy

:: w

ww

.pro

fkris

hna.

com

14/48

Spore FormworkShoring Toppled toGround 6.4m formwork shoring being relocated with tower crane Worker had climbed up formwork shoring to attach the

hook of the crane to it when formwork shoring toppled. The worker fell together with the formwork shoring. Investigations revealed: Worker not provided work platform or safe access. Formwork shoring was not temporarily tied to a fixed

structure or building, nor provided with outrigger.Lapses: No risk assessment Failure to provide safe

means of access Lack of SWP and

hazard analysis No fall prevention

systems were used

8Cop

yrig

ht P

rofe

sor N

. Kris

hnam

urth

y ::

ww

w.p

rofk

rishn

a.co

m

15/48

Spore Downtown Line Collapse 18 July 2012 Two construction workers died after an underground

scaffolding collapsed at the construction site for the Downtown Line at the junction of Victoria Street and Rochor Road. Eight workers suffered minor injuries.

SCDF found both bodies one metre apart from eachother, sub-merged in wet cement and pinned under planks of wood and scaffolding.

http://sg.news.yahoo.com/underground-scaffolding-

collapses-at-bugis-downtown-line-construction-

site.html

Cop

yrig

ht P

rofe

sor N

. Kris

hnam

urth

y ::

ww

w.p

rofk

rishn

a.co

m

16/48

New Code of Practice

9Cop

yrig

ht P

rofe

sor N

. Kris

hnam

urth

y ::

ww

w.p

rofk

rishn

a.co

m

17/48

(CP23) New Formwork Code of PracticeContents Page

Foreword 7CODE OF PRACTICE

1 Scope 82 Normative reference 83 Definitions 84 Materials and formwork systems 11

4.1 Materials & accessories 4.2 Formwork systems4.3 Metal formwork 4.4 Precast formwork

5 Design 125.1 Application of section 5.2 Design considerations5.3 Loads 5.4 Analysis & design methods

6 Drawings 266.1 Information on drawings

7 Erection and use 297.1 Tolerances 7.2 Conditions of formwork & bracing7.3 Shoring 7.4 Bracing of shores7.5 Adjustment of formwork 7.6 Curing7.7 Inspection and supervision

Cop

yrig

ht P

rofe

sor N

. Kris

hnam

urth

y ::

ww

w.p

rofk

rishn

a.co

m

18/48

New Formwork Code of Practice Design Aids

10

Cop

yrig

ht P

rofe

sor N

. Kris

hnam

urth

y ::

ww

w.p

rofk

rishn

a.co

m

19/48

(CP23) New Formwork Code of PracticeContents

8 Dismantling 338.1 General8.2 Formwork removal periods for cast in-situ concrete8.3 Removal period for special conditions8.4 Cracking control

9 Safety 349.1 Risk assessment9.2 Safety precautions9.3 Work at Height9.4 Permit-to-work9.5 Lifting9.6 Modular and system formwork9.7 Safe formwork construction practice related to design

Cop

yrig

ht P

rofe

sor N

. Kris

hnam

urth

y ::

ww

w.p

rofk

rishn

a.co

m

20/48

Formwork Hazards

11

Cop

yrig

ht P

rofe

sor N

. Kris

hnam

urth

y ::

ww

w.p

rofk

rishn

a.co

m

21/48

Safety and Risk Management WSH Act of 2006 imposes performance-based and pro-

active criteria for safety, requiring: Detailed identification of various hazards

involved in all phases of formwork fabri-cation and installation,

Assessment of consequent risks, and, Implementation of required control measures,

according to a hierarchy, i.e. a preferred order of effectiveness.

Formwork Code CP 23 affirms: In addition to fulfilling the very real moral and legal

responsibility to maintain safe conditions for workmen and public, safe construction is the final goal, irrespective of any short-term cost savings from cutting corners on safety provisions.

Cop

yrig

ht P

rofe

sor N

. Kris

hnam

urth

y ::

ww

w.p

rofk

rishn

a.co

m

22/48

Inspection and Supervision The goal of inspection or quality-control programs is: to ensure that contract documents and building

codes are fully and faithfully followed, and to ensure structural safety and architectural

aesthetic compliance. Mistakes can and will often happen, but an inspector is

expected to find them and have them corrected. A quality control program by the contractor helps

reduce errors and makes final inspection easier. 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.

12

Cop

yrig

ht P

rofe

sor N

. Kris

hnam

urth

y ::

ww

w.p

rofk

rishn

a.co

m

23/48

Basic problems with formwork Similar to scaffolds in

erection, use, and dismantling

Common problems:Structural deficienciesConnection deficienciesSharp edges:9Cuts and bruises

Trips and fallsWorking at HeightSun, rain, dust, noiseErgonomics MSD:9Awkward posture9Manual handling

Additional unique problems: From concrete9Weight of wet concrete9 Fluidity of wet concrete9Chemical effects9Vibration 9Uneven loading 9Casting speed9Casting depth9Setting & curing effects

From rebars9Weight of rebars9 Length and sharp ends9 Impalement hazard

Cop

yrig

ht P

rofe

sor N

. Kris

hnam

urth

y ::

ww

w.p

rofk

rishn

a.co

m

24/48

Hazards in Formwork Fabrication & Installation - a(a) In all activities: Physical, ergonomic, mechanical, electrical, and

psycho-social hazards. In physical 9 Manual lifting and ergonomics hazards9 Striking or being struck by objects9 Working at height

(b) Fabrication off-site/on-site, use, and dismantling: Factory floor or site hazards Crane and fork-lift hazards Impalement on projecting rebars Collapse of partial or finished formwork Bad design or planning Overloading or wrong sequence of loading Wrong sequence to add or remove components

Will be covered in

another talk

13

Cop

yrig

ht P

rofe

sor N

. Kris

hnam

urth

y ::

ww

w.p

rofk

rishn

a.co

m

25/48

Hazards in Formwork Fabrication & Installation -b(c) Transportation to and on site: Vehicular hazards

(d) Material handling: Hazardous material cement chemical Heavy and sharp steel physical

Most failures are caused by: Poor planning, Poor design, Inadequate inspection, or The human element.

Almost all failures occur at the time when concrete placement adds considerable weight and pressure on the formwork.

Cop

yrig

ht P

rofe

sor N

. Kris

hnam

urth

y ::

ww

w.p

rofk

rishn

a.co

m

26/48

Collapse of formwork a In theory, formwork must be designed so that they will

be strong and stable under construction loads, which should include delivery of concrete and rebar bundles. Heavy loads must be placed only at specially

designed, designated zones, spread over a wide area by means of planks, placed on or close to extra supports underneath.

In practice, due to lack of clear instructions, design may not cover construction loads.

At site, Safe Work Procedure (SWP) may not cover alternative means to keep loads within safe bounds. Arrangements made to open bundles at ground level

or on strong bases and distribute them on formwork, may not always be followed.

Formwork is most unstable during concrete casting and early stages of hardening and curing, and at its weakest.

14

Cop

yrig

ht P

rofe

sor N

. Kris

hnam

urth

y ::

ww

w.p

rofk

rishn

a.co

m

27/48

Collapse of formwork b A bundle of 20 numbers of 15m long 32mm rebars weig-

hing about 19kN may be placed on formwork designed for 1.5kN per sq.m plus a concentrated load of 2kN.

Crane cannot place rebar bundle on formwork precisely flat so as to ensure a uniform distribution of total load. At least half the weight amounting to about 10kN will

be delivered as concentrated load to formwork, over-loading the temporary structure by about three times.

To prevent this, design (and related SWP) must specifi-cally cover placement of heavy loads on formwork. There are rules for placement of concrete on form-

work, for height of drop, and spread area. Multi-storey work has additional danger of shoring of

new work on to recently completed work which may not have attained adequate strength, or which may not itself be adequately shored Engineer shall be consulted.

Cop

yrig

ht P

rofe

sor N

. Kris

hnam

urth

y ::

ww

w.p

rofk

rishn

a.co

m

28/48

Striking against objects With many loose/heavy materials/objects moving around

under mechanical, electrical and human power over a restricted area, with many workers focussing on indivi-dual or small team work, even with supervision, there would be occasions for workers to strike against objects.

Common situations are: Rear worker in two-worker operation does not stop

when forward worker stops, and this pushes latter against some sharp/hard object;

Worker is dragging something and moving backwards in a bent position, and then straightens up without checking if he is under something.

Impalement on projecting rebars Supervisors must take special care to ensure workers

are alert in their work and vehicle drivers extra cautious.

15

Cop

yrig

ht P

rofe

sor N

. Kris

hnam

urth

y ::

ww

w.p

rofk

rishn

a.co

m

29/48

Struck by objects a Even if workers are trained, given PPE, and supervised,

chances of their being struck by objects are high. During loading or unloading, or when moving formwork

components, often small items get dropped, and impact on lower limbs of persons at same level or on torso of persons at lower levels can be very traumatic.

Apart from helmets, use of chin-straps must be insisted. All other PPE such as steel-toed shoes, gloves, etc.

are essential. Problem is worse because of large weight of concrete

and steel, and high hardness of steel being moved. E.g. Crane or forklift loads hitting workers.

Though velocity may be low, due to large weight, momentum is high and movement cannot be stopped even if operator sees the danger.

Cop

yrig

ht P

rofe

sor N

. Kris

hnam

urth

y ::

ww

w.p

rofk

rishn

a.co

m

30/48

Struck by objects b

Sudden stopping of truck with long rebars will make them fly like javelins into objects & people in front, and/or, impale riders at back.

Crane signallers and forklift supervisors must be specially alertin guiding the loads in their movement.

Rebar movement is such a hazardous operation that continuous supervison would be a must.

Icons-land

Crane signallers and forklift supervisors must be alert in guiding loads in their movement continuous supervison would be essential.

16

Cop

yrig

ht P

rofe

sor N

. Kris

hnam

urth

y ::

ww

w.p

rofk

rishn

a.co

m

31/48

Impalement on projecting rebars a Due to medium likelihood of occurrence & high severity

of consequence, specific SWPs & safety devices against impalement on rebars are in use in many countries. In Singapore, it is neither required nor standard prac-

tice to provide safety cover for exposed rebar ends. Inclined or even horizontal rebars are a threat for

impalement, because if a worker bumps into exposed sharp end of rebar with sufficient force to puncture his

Fig. 9.2. Uncapped Rebars

skin, and momentum can cause heavy internal damage.

Careless handling of (or being near) rebars pro-jecting from pre-cast or already cast members can cut & mutilate hands.

Cop

yrig

ht P

rofe

sor N

. Kris

hnam

urth

y ::

ww

w.p

rofk

rishn

a.co

m

32/48

Impalement on projecting rebars b Figure shows common practice to cover rebar ends by

rounded (mushroom) or flat-topped plastic caps. But these are only scrach and cut protectors and will

not protect worker from serious injury if falling >2m.

Fig. Rebar caps or guards Fig. Rebar and cover Caps with large contact area and sufficiently strong to

resist impact from large heights may be approved. For real protection, line of exposed rebars should be:

(i) Covered by a protective shield (2 by 4 or plank); or,(ii) Bent so sharp ends are pointing down or back.

17

Cop

yrig

ht P

rofe

sor N

. Kris

hnam

urth

y ::

ww

w.p

rofk

rishn

a.co

m

33/48

Tripping and falling Common hazards are: Tripping on formwork projections or depressions and

falling Tripping on rebars and falling Abrasions and cuts during

handling of rebars, wood or steel components, some of which may slice through palm to the bone;

Pinching and crushing of fingers, toes, hands, wrists, some of which may necessitate amputation.

Steel-toed shoes, thick gloves, and thick full body clothing are essential to prevent consequences.

Cop

yrig

ht P

rofe

sor N

. Kris

hnam

urth

y ::

ww

w.p

rofk

rishn

a.co

m

34/48

Mechanical hazards In formwork, receiving, storing, handling, cutting,

bending, and moving timber and steel components are quite common. Hazards can range from cuts, bruises, and pinched

limbs, to eye inuries, amputations, fractures etc. Conrols must follow usual hierarchy for these hazards: Machine guards, Safety interlocks for machine operation, Up-to-date training, Appropriate PPE, and Strict maintenance, inspection,

and supervision regime.

18

Cop

yrig

ht P

rofe

sor N

. Kris

hnam

urth

y ::

ww

w.p

rofk

rishn

a.co

m

35/48

Electrical hazards Formwork involves more mechanical and manual

operations than electrical. However, as electrically operated hand tools are

involved, or night work has to be done, electricity becomes an additional source of danger to workers.

Possible consequences of frayed insulations, contact with water, ungrounded circuits, etc. could range from simple electric shock to fatal electrocution.

Shock may not injure worker but instantaneous jerk may throw him off balance and make him and/or co-worker on whom he may bump, fall and get hurt.

Electric shorts can result in fires & explosions. Hand tools running on 110v safer than 220v. All normal precautions, as well as strict maintenance,

inspection, and supervision regime must be observed.

Cop

yrig

ht P

rofe

sor N

. Kris

hnam

urth

y ::

ww

w.p

rofk

rishn

a.co

m

36/48

Noise Noise is a common hazard in construction sites,

including formwork. Noise-induced hearing loss or deafness (NIHL or NID) is

fully preventable but once acquired, hearing loss is permanent and irreversible.

Use of earplugs, and isolation of noisy equipment must be ensured.

The problem, is now addressed by authorities. Construction industry should proactively control.

19

Cop

yrig

ht P

rofe

sor N

. Kris

hnam

urth

y ::

ww

w.p

rofk

rishn

a.co

m

37/48

Psychological hazards Psychological hazards have not been a serious problem

in Singapore, if only because it has not been reported. However, the largely immigrant workforce suffers under

communication and cultural handicaps Heavy manual / mechanical handling, and highly

repetitive nature of formwork tasks can induce a lot of mental stress and loss of concentration on top of major physical labour.

It is worth relieving psychological stress by providing good site facilities and rest breaks.

Chemical hazards Skin Contact burns, rashes, and skin irritations. Eye Contact irritation, to painful chemical burns. Inhalation Nose, throat irritation; lung disease silicosis.

Cop

yrig

ht P

rofe

sor N

. Kris

hnam

urth

y ::

ww

w.p

rofk

rishn

a.co

m

38/48

Chemical Hazards

http://www.usmra.com/repository/search_category.asp?category=construction

20

Cop

yrig

ht P

rofe

sor N

. Kris

hnam

urth

y ::

ww

w.p

rofk

rishn

a.co

m

39/48

Ergonomic Hazards

Cop

yrig

ht P

rofe

sor N

. Kris

hnam

urth

y ::

ww

w.p

rofk

rishn

a.co

m

40/48

Awkward posture a Even without overload, many tasks in formwork fabrica-

tion and erection involve bending and twisting postures, which if continued for too long without sufficient rest and compensatory exercise, could affect the workers health. Lifting and arranging formwork planks, cutting and

connecting components, etc. are common examples. Most common consequence of such bad work posture is

MSD, short for musculo-skeletal disorder, over-straining various muscles. If not relieved by rest, medi-

cation, physio-therapy etc., it may result in permanent muscle and nerve damage leading to paralysis, gang-rene, etc.

Carpentry work

21

Cop

yrig

ht P

rofe

sor N

. Kris

hnam

urth

y ::

ww

w.p

rofk

rishn

a.co

m

41/48

Awkward posture b In USA MSDs are most common injuries in construction

industry, accounting for over one-third of all lost workday injuries and about half of all compensation claims. Situation in other advanced countries is also critical.

In Asia the problem has not made itself felt, mainly because culturally Asians are more used to bending and squatting than Westerners. But habits & lifestyles have been changing & Asians

too may become more vulnerable to MSD.

Singapore authorities are promoting awareness of this recently recognised hazard & its consequen-ces to improve safety.

Cop

yrig

ht P

rofe

sor N

. Kris

hnam

urth

y ::

ww

w.p

rofk

rishn

a.co

m

42/48

Awkward posture c MSD can be taken care of with various safeguards: Raising job to a level not requiring bending back; Providing lighter tools, with easier controls; Replacing hand tools with mechanical tools; Planning work and arranging materials to avoid

unnecessary movement; Giving workers more breaks during task; Increasing number of workers9 they dont cost that much, but in Singapore,

availability may be a problem; Rotating workers in such tasks; Decreasing speed/rate of work; Changing posture frequently; Minimising the amount of such work by substitution,

pre-fabrication;

OR

?

22

Cop

yrig

ht P

rofe

sor N

. Kris

hnam

urth

y ::

ww

w.p

rofk

rishn

a.co

m

43/48

Repetitive work a Formwork fabrication will involve thousands of opera-

tions of same kind, each of which requires concentration and physical effort of same kind.

In concreting, vibration of cast concrete is a common example.

In rebar work, a typical reinforcement cage will involve thousands of operations of the same kind, such as: Arranging bar chairs under rebars, Tying rebars with binding wire.

Limbs involved are fingers, wrist, hand, and elbow. Repetitive use of these muscles and nerves will lead

to disabling conditions as carpel tunnel syndrome. These may be relieved by worker-related safeguards

from list presented under (b) Awkward posture.

Cop

yrig

ht P

rofe

sor N

. Kris

hnam

urth

y ::

ww

w.p

rofk

rishn

a.co

m

44/48

Repetitive work b Much of bending and doing

repetitive work has been replaced in Western countries with mechanical aids such as automatic rebar tying device.

Fig. Rebar tying

device with extendable

handle

Fig. Rebar work in bent position

Fig. Rebar tying

device

23

Cop

yrig

ht P

rofe

sor N

. Kris

hnam

urth

y ::

ww

w.p

rofk

rishn

a.co

m

45/48

Manual handling a For every kg we pick up from our foot level, our back-

bone is subject to about 12kg force. So, if a worker picks up a cement bag, or steel decking

2m long and 200mm wide of 4.8mm thick metal, both of which weigh 50kg, it puts a force of 600kg on backbone.

In addition, if he weighs 70kg, bending forward puts weight of upper half of his body, that is an additional 35kg acting at half distance from the arm, with effective-ly half magnification effect, i.e. 6 times, or 210kg force on his backbone.

Total force on backbone = 810kg

Cop

yrig

ht P

rofe

sor N

. Kris

hnam

urth

y ::

ww

w.p

rofk

rishn

a.co

m

46/48

Manual handling b Most Asian backbones are designed (by nature) to take

safely about 500kg on a regular basis, with an occasio-nal overload of 50% and a limit of another 50% before permanent damage sets in. Working backwards, we can show that worker can

carry (500-210)/12 i.e. 24.2, or about 25 kg routinely. Unfortunately, overload effects on backbone cannot be

Fig. Form plank lifting

reversed after a time, and victim is destined to endure pain and a stiff back for rest of his life.

Hence workers carrying more than about 25kg on a regular basis are putting abnormal strain on their backbones, which in a couple of years, can lead to permanent spine damage.

24

Cop

yrig

ht P

rofe

sor N

. Kris

hnam

urth

y ::

ww

w.p

rofk

rishn

a.co

m

47/48

Manual handling c This is not as well known as other dangers such as fal-

ling from height, & many workers overstress their back. This situation can easily be handled by one or more of: Wherever possible, dividing loads into parcels of

25kg or less; Assigning more workers to share the load; Providing mechanised aids such as dollies (carts); & Training and insisting on workers to squat and

carry instead of bend and lift.How to lift a weight

Cop

yrig

ht P

rofe

sor N

. Kris

hnam

urth

y ::

ww

w.p

rofk

rishn

a.co

m

48/48

The End