| Case Name |
The floor was cracked by the omission concrete work in the erection |
| Pictograph |
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| Date |
November 2000 |
| Place |
Bangkok City, Thailand |
| Location |
Building construction field in the suburb in Bangkok City. |
| Overview |
In concrete cast construction of building construction field in the suburb in Thailand Bangkok City, the crack was soon generated in the floor after the casting , because the quality management was not sufficiently carried out. One of the main causes of the cracking seems to have been carrying out curing from the day of the concrete cast and only over 2 days. |
| Incident |
In concrete cast construction of building construction field in the suburb in Thailand Bangkok City, the crack was soon generated in the floor after the installation, because the quality management was not sufficiently carried out. |
| Sequence |
It is desirable for Bangkok City in Thailand that the concrete cast construction of the slab of the wide area starts from the evening and ends at night.
Reason:
1 It is necessary for the consultants to confirm the preparation of the concrete cast construction.
2 The crack of the surface is difficult to be generated, since the temperature becomes lower in the night.
3 Since the traffic volume of civic center section is decreased at night, the possibility that the ready-mixed concrete car is involved in a traffic jam is small. However, many business persons think that it is possible to carry out casting concrete in the daytime and curing from the next day in order to regain the delay of the process.
This time, the price of the concrete work from main contractor company to subcontractor company was determined only by the contract paid in proportion to the casting quantity, without completely considering other conditions. The subcontractor company agreed with the proposal of the main contractor company that it carry out the construction in the daytime and curing from the next day because overtime allowance to the workers must be borne by the subcontractor in the night and the profit decreases.
Though this concrete work was the construction which required the curing for 7 days according to the standard of Thailand, in this field, curing was carried out for only 2 days. In addition, the temperature is high and the evaporation rate of the moisture is also high in Thailand. Though the necessity of the cost curing has also been recognized, there is no field which adopts it actually because it becomes more expensive. It was not adopted even in this field. |
| Cause |
One of the main reasons of generating the crack is that the curing was retarded and that the period was not sufficient. |
| Countermeasures |
For the perspective of mid-and-long time, technology and skill courses etc. are frequently held. It is necessary to make workers understand the necessity of observance of the performance standard while raising the level of technology and skill. As a countermeasure to be carried out immediately, the main contractor company prepares the operation standard and the observance of it in the field is thorough. It is also important that each field organization regulates each role and responsibility in allocated clearly. In this field, the feed water pump was broken down while curing and the work had to be interrupted.
In another field, it rained heavily as soon as casting finished. The field became water-logged immediately because of neglecting the preparation for rainfall.
Needless to say, it is important to make the scrupulous construction plan in order to deal with the unexpected incident immediately. |
| Knowledge Comment |
It is necessary to carry out the curing sufficiently in order to prevent the crack of the concrete work. In Thailand, knowledge and interest for the quality management of concrete work of persons engaged in business are insufficient. For the perspective of mid-and-long time, it is essential that technology and skill courses are held, and raising the level of technology and skill of the engineers in the field is attempted. As a countermeasure to be carried out immediately, the main contractor company prepares the operation standard and the observance of it in the field is thorough. It is also important that the each field organization regulates each role and responsibility in allocated clearly. |
| Background |
Hearing the investigation carried out were the following people engaged in business: the orderer, the concrete manufacturer, the consultant, the main contractor company and the subcontractor company. As the result, the fundamental causes were following.
1 Knowledge and interest of people engaged in business for the quality management of concrete work
2 The problems in the quality management: a)Planning, b)Organizing, c)Leading, d)Controling
1 Knowledge and interest of persons engaged in business for the quality management of concrete work
There are many persons engaged in business who do not sufficiently understand the importance of curing. To the concrete manufacturer, the consultant, the main contractor company, the enginners and foremen of subcontractor company, whether they had the experience participating in the technology lectures or training formally of concrete work was agreed. In fact, there were only about 1/3 persons who had experience. Many foremen think it is difficult to carry out work by confirming performance standard because the cost, work time and even a risk of work are increased by the observance of guidelines for work. More than a few foremen replied that they carry out work "flexibly" based on the experience themselves.
2 The problems in the quality management
a) Planning : main contractor company did not prepare the operation standard for the construction. And, there was a matter that in this field, the feed water pump was broken down under curing, and the work must have been interrupted for a long time.
b) Organizing : There was no organization which regulated each role and responsibility in this field clearly. The usual foreman in the field in Thailand instruct the workers on the execution of the curing work. However, the foremen sometimes forget to instruct because they have other work. This field was not the exception,either.
c) Leading : Though the security of the construction quality was very important for the orderer and the consultant, the reduction for construction expenses was the largest factor for the main contractor company and the subcontractor company in this field. Therefore, being combined with the reason that main contractor company did not prepare the operation standard, "superexpress" curing for only two days and "the omission construction" that water sprinkling was insufficient were carried out.
d) Controling
Each sharing of roles was not always cleared in this field. Therefore, there was no person who inspected whether the actual curing work was carried out sufficiently and took the remedial actions in the insufficient case. |
| Account of Concerned Parties |
Many main contractor companies and subcontractor companies regard the most important purpose of the field management as not security of the construction quality but the reduction of construction expenses. In the background, Thailand still cannot escape from the economic depression, and there may still be small construction quantities. However, as various cases in recent Japan show, such a neglect of construction quality brings about shortening the in-service period of the structures and increases the maintenance and repair costs. In the worst case, the parts of the structure may be damaged in service and there is a danger that the major accident might occur. |
| Reason for Adding to DB |
It seems to be an example of the failures which highlight the importance of quality control and the need for clarification of role and responsibility on each subject, and necessity of the practice again. |
| Scenario |
| Primary Scenario
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Poor Response to Change in Environment, Change in Economic Factors, Organizational Problems, Inflexible Management Structure, Production, Hardware Production, Non-Regular Action, Change, Failure, Fracture/Damage
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| Sources |
The failure knowledge database development project: construction field research council fourth research council announcement material.
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| Field |
Civil Engineering
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| Author |
WATANABE, Tsunemi (Kochi University of Technology)
KUNISHIMA, Masahiko (The University of Tokyo)
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