Failure Knowledge Database / 100 Selected Cases

Crash disaster of a construction site - the accident which originated frominappropriate use of a safety belt
[On a certain day in August, 2003, Kanagawa Prefecture]
Masahiko KUNISHIMA・Yukihiro ISHIHARA (Note)

On a certain day in August, 2003, in a construction site of 12-story condominium, whenbolting work on the steel beam of the sixth floor was done during steel erection of thesteel column, the ring of the safety belt (spring hook) which the worker used came off,
and the worker fell about 17 meters down to the ground. He was taken to the hospital,and he died soon after. Besides this accident, a succession of crash disasters which were
thought to originate from the inappropriate use of safety belts has occurred in recent
years. And, while the low consciousness of safety of the worker in the construction site
was recognized, it became an opportunity to improve the way of safety education in aninterested concern.
１．Event
In August, 2003, in a construction site of 12-story condominium, in Kanagawa
Prefecture, the accident occurred. When bolting work on the steel beam of the sixth floor
was done during steel erection of the steel column, the ring of the safety belt (springhook) which the worker used came off, and the worker fell to the ground, and he diedsoon. Besides this accident, a succession of crash disasters which were thought tooriginate from the inappropriate use of safety belts has occurred in recent years, andthe effective deterrence measures have been fumbled about and examined.
２．Course
It was the new construction of a condominium involving steel-framed reinforced
concrete construction, and the foundation work had already ended by the previous dayof the accident. The steel frame of the body part stood to 4 knot part (the 12th floor), thesteel frame of central part stood to 2 knot part(the fourth〜sixth floor), and the steel
frame of the remainder had not yet been assembled. The steel erection work on the dayof the accident was the work which assembled the steel of 3 knot part(the seventh〜
ninth floor) of the central part, which was assembled to 2 knot part. The work wasadvanced by the method that the steel of this part was lifted by the transportable crane,
and workers A and B did temporary tightening of the steel column of 3 knot part and the1Failure Knowledge Database / 100 Selected Cases

steel column of 2 knot part with an attached board and bolt while lifted by atransportable crane.
From the morning, the work proceeded as planned,
and workers attached the safety belt to the main ropeand gangway for going up and down on the steel beamof the sixth floor, and did the temporary tightening of
the steel column of 3 knot part and the steel column of
2 knot part with attached board and bolt while liftedby transportable crane. A worker A stood on the steel
beam of the sixth floor, attached his safety belt to thestretched main rope, and carried out the temporary

Figure 1.

tightening work. Meanwhile, because there was no(Source: Japan Construction Safety andappropriate scaffold, a worker B passed the rope of

Health Association"The cases andhis safety through the gangway of the steel column,

countermeasuresofput his weight on the rope of his safety belt in theaccidents in construction<6conditionofU-hanging,andcarriedout

The sketch in the disasterworkmen’s
volume>")thework.(Figure1.)
Then, the worker B gave a shout, and he fell about 17 meters down to the ground. He
was taken to the hospital, and he died of the blood loss from the thorax bruise after 2hours.
３．CauseThe direct cause of this case was that the worker B did not use the safety belt
appropriately. The safety belt the worker B used was generally for single-hook hanging
which was the type not used for U-hanging.（ The explanation of safety belt for
single-hook hanging and for U-hanging is described later.） Also, a ring for hanging
tools (spring hook), which the worker B used as U-hanging and was attached to the hookof the safety belt, was not originally the thing installed as a part of the safety belt, but
the thing which the worker installed to hang tools, etc. after he had purchased thesafety belt individually, and it deviated from the standard as directed in "standard forthe safety belt".
From a different viewpoint, this case was caused by a management element of the
management side, such as the overly optimistic work plan of the original contractor andthe careless safety management in the site. In this case, though the work was done
where there was the possibility of crash, the treatment of the crash prevention such as
the installation of work floors and handrails had not been made. And, it was also a2

Failure Knowledge Database / 100 Selected Cases

problem that the chief worker in the site did not watch inspection of the function ofsafety belts and their use.
It can be said that low consciousness for the way of safety management in high-place
work on the part of the worker and the manager was the fundamental factor whichcaused this case.
The safety belt for single-hook

The safety belt for U-hanging

hanging is used at the work

can be used when the worker

place with a stable scaffold bywants to put his weight onwhich worker may not support

the safety belt during work.

his body. It is dangerous to do

Therefore,

U-hanging with a safety belt

performancefor single-hook hanging.

thicker rope than the safety

it

has

higher

such

as

a

belt for single-hook hanging.

single-hook hanging

U-hanging

Figure 2. 2 kinds of safety belt
(Source:

Home page of "What’s safety belt?")

About safety belt
The safety belt is used for the crash prevention, when a worker works in a high place.
"Labor Safety and Health Regulation" states that the entrepreneur must make workers
to use safety belts when the work floor can not be established at the point higher than2m in height (Section 2 of Article 528), and that the worker must not use the safety belt
which does not meet "standard for safety belt", which was established according to theprovisions of Article 42 of "Labor Safety and Health Law" (Article 27).
As an explanation edition of "standard for safety belt", there is a technical guide "thestructural guideline of safety belt" issued by the independent administrative institution"National Institute of Industrial Safety", and it explains type, name, and usage of safety
belts.
The difference between the safety belt for single-hook hanging and the safety belt for
U-hanging (Figure 2.)
The safety belt for single-hook hanging is the safety belt for the crash prevention, andis used at the work place with a scaffold by which worker may not support his body. On
the other hand the performance requirement of the safety belt for U-hanging is that it
can be used with the worker putting his weight on the safety belt during work.
Therefore, the rope is thick, and a telescopic motion regulator which can adjust thelength has been added. For this reason, U-hanging using a safety belt for single-hook

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Failure Knowledge Database / 100 Selected Cases

hanging is dangerous because it means requiring the performance which exceeds theoriginally assumed ability for the single-hook hanging.
The standard for spring hook
There seems to be an experiment which shows that the substandard spring hook likethe one used in this accident is damaged with the mouth of spring hook coming undone
even by putting one’s weight on the U-hanging rope. In the "standard for safety belt",
the thing like the following has be made to be an appropriate spring hook.
（１）④ of Article 1 of standard for safety belt (definition)"the ringed instrument for connecting ropes of the lanyard, etc. and attachments, etc.
or the ring"（２）About strength of spring hook, on industrial safety norm regulation of ILO(strength of parts),
It has been prescribed that the belt and ropes of the safety belt must have 1150kgf
breaking strength at least.
（３）Article 5 of standard for safety belt (shape of parts, etc.)"It must be equipped with miss stop equipment which does not come undone unlessthere are more than 2 consecutive operations".

The left figure is an example of a springhook.

It is used daily even outside

construction sites, and it is possible topurchase freely.

The right figure shows

the aspect in which the mouth of spring
hook comes off.

Figure 3. Example of spring hook and its damage(Source: Kanagawa Labor Bureau, Ministry of Health, Labour and Welfare)

４．Immediate Action
From Labor Standards Inspection Office in Kanagawa Prefect., where the accident
arose, leaflets which appealed for appropriate management and use of the safety belt
were distributed to the builders. Also from the Safety Division in Kanagawa Labor
Bureau, the leaflets which drew their attention were distributed. And, major
constructors carried out general inspections of the field, responding to the improper useof spring hook.

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Failure Knowledge Database / 100 Selected Cases

The actual conditions about safety belts known by the general inspection
In the inspection which each field independently did, 20%〜40% of safety belts had
imperfections. It included things in surprising condition like the following.
・The safety belt whose rope and belt were ragged
・The safety belt which has the belt for work with plastic buckle
・The safety belt which only wound a lanyard round body belt
・The safety belt with 2 of 3 strands cut off which are hidden by taping
５．Countermeasure
In September, 2003, "a national campaign for proper use of the safety belt "under thesponsorship of Japan Rodo Press was held in Yokohama. Including the movement like
this, the trial which improves the attention of the party concerned by taking up the
problem of the safety belts in magazines articles, etc. has been made.
Most of discussions in the campaign and those which are reported in the magazines
discuss the proper use of safety belts from the worker’s side and provide guidance andeducation for and management of the worker by the original contractor and thespecialty contractor (in short, the management side). It seems to take much time for thecountermeasures in such soft component side to move to the execution from the proposal,
and moreover to be established widely. At present, there are few things to be concretely
visible as a countermeasures under the present conditions.
６．Generalization
Crash disasters, including this accident, occupy near half of all fatal accidents in theconstruction industry. At present, the parties concerned in the field have low
consciousness of the safety management, even though high-place work is dangerous.
This fact has been realized again since the time in which this accident arose, and the
movement for the improvement in the consciousness of the field in terms of the safety
would energetically be sought. The crash accident has the property of some kind ofinternal completeness, and it is the problem that fundamentally troubled only theparties concerned in the field, and it does not affect the public citizen. Therefore, it
seems that it has the property that it is difficult to be utilized as failure knowledge
because of not causing the public opinion, even if it happens.
７．Knowledge
The matter of work planning
１．In the steel assembly work of buildings, etc. work plans that show methods and5Failure Knowledge Database / 100 Selected Cases

procedures of the work and installation methods of the crash prevention facility, etc.
Beforehand are determined, and it is necessary to carry out the work based on thosework plans.
２．When the work is done in the position with a danger of crash, it is necessary torealize again that crash prevention measures such as making work floors and handrails
are taken first of all, and in the unavoidable case, safety belts and safety nets are
installed.
The matter of guidance and management of use of the safety belt (manager)
１．With the safety belts, periodic general inspections, general exchanges, and blanket
purchases by the field are desirable. In terms of the expenses, paying not by theindividual but by the company is desirable.
２．The strand of safety belt becomes weak in ultraviolet rays, and its strength reducesby half after about 2 years, even if there is not so much damage to the surface. Writing
the beginning of use date on the safety belt, and management checking the period arenecessary.
３．It is necessary that the chief worker of steel assembly of the building, etc. checks thefunction of safety belts before the work starts and watches their use.
４．It does not become the essential solution that the use of inappropriate safety belt byworkers is unconditionally prohibited. Daily attention to directing and education ofknowledge, skill, and attitude about safety are necessary.
The matter of the use of the safety belt (worker)
１．It is necessary to use the safety belt which has an appropriate structure for use with
U-hanging, when the work is carried out, requiring a safety belt with U-hanging.
２．It is realized again that conscience reform about safety leads to protecting one’s own
life, and workers try to improve the safety of the whole field by calling out to each other,etc. with voluntarily learning and practicing about safety.
８．BackgroundThough usage rate of safety belt is 100% in the construction site of major construction
companies, more and more accidents involving safety belts ironically occur with theincrease in their use.
One of the causes is that until now, the safety belt was a fact of a passport of the field
entrance, and workers had only to wrap the safety belt around their waist. Though
there are use and inspection and disposal standards in all companies, there seem to be

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Failure Knowledge Database / 100 Selected Cases

no precedents for putting these standards into practice. Under the actual situations, theimportance of safety belts is downplayed in the sites, and they are not perfectly used forthe reasons including the work takes a little time, or that it is troublesome. It can besaid that such low consciousness for safety has induced the unsafe action on the sites.
On the expenses of safety belt, the companies in the manufacturing industry and theconstruction industry pay the expenses, but workers of many cooperation companies
pay their own expenses, and the replacement period, type and management of safety
belts, etc. is left to the workers. Therefore, some workers personally purchase safety belt
at do-it-yourself stores, etc. on a holiday. When the safety belt purchased in such store isa name-brand item which is "standard for safety belt", is no problem. But in many cases,
goods (spring hook, body belt, etc.) are sold as an accessory at the same place as that ofsafety belts without enough explanation, so though they don’t suit the standard, andthere is a possibility of misunderstanding over whether they are safe to use.
９．On the Side
The present state of the problem of the safety consciousness in the organization is thateach organization is entrusted with the education and management of it and it is notstrange that the accidents like this have been occurring one after another. Especiallyabout crash disasters in construction sites, since the victims of the accidents are limited
to a worker himself, the occurrence of the accidents does not cause large public outcry,
and the problem tends not to come to the surface, even though the accidents occupy
nearly half of all fatal accidents in the construction industry. It is not easy to find thebasic solution, but for example, it may be necessary for Labor Standards Bureau to havethings like surprise inspections which have legal force. Or, it may be effective to give thesocial discipline (suspension of a business license and tender exclusion, etc.) to theorganizations which pay lip service to safety by merely making rules and laws and not
applying them. After all, it should be known that the times that the constructionindustry itself is not permitted, if the idea of the compliance is not urgently adopted,
has come.
＜Reference＞
Anzen staff 2004.2.15
Anzen staff 2004.10.15"What’s safety belt?" http://www.fujii-denko.co.jp/anzenn_what.html
Japan Construction Safety and Health Association
workmen’s accidents in construction<6volume>"7"The cases and countermeasures ofFailure Knowledge Database / 100 Selected Cases

Japan Construction Safety and Health Association"Statistics of workmen’s disasterby looking graphs"
Kanagawa Labor Bureau, Ministry of Health, Labour and Welfare
http://www.kana-rou.go.jp/index.html
Safety Division, Industrial Safety and Health Dept., Labor Standards Bureau, Ministryof Health, Labour and Welfare "The situation of workmen’s disaster in 2004(newsflash)"(Note) Department of Civil Engineering, Faculty of Engineering, the Univ. of Tokyo

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