| Case Name |
The result in the execution of the bridge development project which abutments, etc. became an unstable condition, since the design was not appropriate. |
| Pictograph |
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| Date |
1992 |
| Place |
The Hokkaido Tokoro District Oketo town. |
| Location |
The town office. |
| Overview |
When the prestressed concrete highway bridge is set up, the bar arrangement drawing was made erring in the diameter of reinforcing steel placed in heel board in the right bank side abutment. Therefore, since it was constructed based on this design, abutment and digit constructed temporarily on it became unstable without ensuring the stability of the right bank side abutment in the earthquake. Therefore, government subsidy equivalent which concerns this \ 30453,600 was considered unreasonable. |
| Incident |
On the reinforcing steel of heel board in the right bank side abutment, reinforcing steel of 22 mm in diameter should have been placed for the upper part plane as the main reinforcement in the 25 cm interval in order to be safe in stress calculation, according to design calculation book which is a base of the design. However, in erring, when the bar arrangement drawing was made, the reinforcing steel of 16 mm in diameter should be used. As a result, in the reinforcing steel of 16 mm in diameter, the degree of tensile stress ( in the earthquake ) in the joint between heel board and length wall in main reinforcement in the upper surface side became the 3856.3 kilogram par square centimeter while it would be 2020.1 kilogram par square centimeter, in case of reinforcing steel 22 mm in diameter. It drastically surpasses allowable tensile unit stress 2700 kilogram par square centimeter of the reinforcing steel, and it has exceeded the safe range in the stress calculation. Therefore, the abutment and prestressed concrete digit constructed on it became an unstable condition without ensuring the stability in the earthquake, since the design of the right bank side abutment of this case was not appropriate. |
| Sequence |
* The assistant industry to produce 2 abutments and prestressed concrete digit was carried out at \ 59740,000 ( government subsidies \ 35844,000 ) construction expenses to set up prestressed concrete highway bridge.
* Reinforcing steel of 22 mm in diameter should have been placed for the upper part plane as the main reinforcement in the 25 cm interval in order to be safe in stress calculation, according to design calculation book.
* When the bar arrangement drawing in the right bank side abutment was made, it was written that the reinforcing steel of 16 millimeters in diameter should be used instead of 22 millimeters in error.
* Based on the design, the heel board was constructed.
* Abutment and prestressed concrete digit constructed on it became an unstable condition.
* Government subsidy equivakent \ 30453,600 which concerned this was considered unreasonable. |
| Cause |
This is mainly due to the mistakes by the designers individual. This in the typical example, there is the numeral mistake. That is because 16 millimeters had been used in the case of the similar construction before, and seems to be biased by such fact to cause mistake ( convincement ). And, it is also considered that the organization couldn't notice the failure without reviewing the specification thoroughly. |
| Countermeasures |
This failure ( erring in the diameter of the reinforcing steel, ) is frequently happening, and it is important most of all that the designer recognizes the fact. It is considered that, it is necessary to systematically establish staffs in the section of the review separate from the designer. Since the bias is also applied on the designer. |
| Knowledge Comment |
It is very abounding to err in the diameter of using reinforcing steel, when the bar arrangement drawing is made. The design calculation book should be read again many times by warning! |
| Scenario |
| Primary Scenario
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Misjudgment, Misperception, Planning and Design, Poor Planning, Malfunction, Specifications Not Met, Possible Damage, Potential Hazard
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| Sources |
The 1992 fiscal year settlement inspection report ( Board of Audit ).
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| Financial Cost |
Government subsidy delivery amount considered unreasonable \ 30453,600. |
| Multimedia Files |
Fig2.Right side shore side bridge stand concept chart
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| Field |
Civil Engineering
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| Author |
MIYAKI, Yuya (The University of Tokyo)
KUNISHIMA, Masahiko (The University of Tokyo)
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