| Case Name |
The result in the execution of the bridge development project which the bridge pier becomes an unstable condition, since the design was not appropriate. |
| Pictograph |
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| Date |
1992 |
| Place |
The Toyota City, Aichi Prefecture. |
| Location |
The city office. |
| Overview |
When steel highway bridge ( 474.5m length, 20.0m width ) of the arch style is set up, in erring in the interval of reinforcing steels as the main reinforcement placed in length ( water flow ) direction in undersurface of the deck slab base of 2 bridge piers, the bar arrangement drawing was made. Therefore, the bridge became an unstable condition, when it was constructed based on this design. Therefore, \ 17358,000 of government subsidy equivalent which concerned this was considered unreasonable. |
| Incident |
For the main reinforcement placed in length ( water flow ) direction in undersurface of the deck slab of 2 bridge piers, reinforcing steel of 32 mm in diameter shall be placed in 12.5 cm interval in lower step, and reinforcing steel of 29 mm in diameter shall be placed in 12.5 cm interval in upper step, in order to be safe in stress calculation, according to the design calculation book which was the base of the design. However, when the bar arrangement drawing was made, the reinforcing steel of upper step have been designed to be placed in 25cm interval, in erring. As this result, the degree of tensile stress in vertical main reinforcement placed in length ( water flow ) direction in undersurface of the deck slab became 1943kg/cm2 ( always ), 2764kg/cm2 ( in earthquake ) in the upstream bridge pier and 1864kg/cm2 ( always ), 2913kg/cm2 ( in earthquake ) in the downstream bridge pier. These drastically surpass 1600kg/cm2 ( always ) and 2700kg/cm2 ( in earthquake ) which is the allowable tensile stress, and it has exceeded the safe range in the stress calculation. Therefore, 2 bridge piers of this case became an unstable condition, since the design was not appropriate. |
| Sequence |
Assistant industries for construction of 2 bridge piers, 1 abutment and pier foundation for setting up arch style steel highway bridge was carried out at \ 700651,320 ( government subsidy object amount \ 247000,000 and government subsidies \ 135850,000 for this ) of construction expenses.
Reinforcing steel of 32 mm in diameter should have been placed in 12.5 cm interval in lower step, and reinforcing steel of 29 mm in diameter should have been placed in 12.5 cm interval in upper step, in order to be safe in stress calculation, according to the design calculation book.
For the main reinforcement placed in length ( water flow ) direction in undersurface of the deck slab, when the bar arrangement drawing of 2 bridge piers was made, the reinforcing steel of upper step, which should have been placed in 12.5cm interval, have been designed to be placed in 25cm interval, in erring.
When it was constructed based on this, degree of tensile stress in the reinforcing steel had exceeded the safe range in the stress calculation, and it became an unstable condition.
Government subsidy equivalent \ 17358,000 which concerned this was considered unreasonable. |
| Cause |
This is mainly due to the errors by the designers individual. In this case, it is the numeral mistake, but the interval had been made to be 25cm in case of the previous similar construction, and it is guessed that that the bias by it occured a mistake ( convincement ). And, it is also considered that they couldn't systematically realize the failure without reviewing the specification thoroughly. |
| Countermeasures |
This kind of failure ( erring in the interval between the reinforcing steels ) is frequently happening, and it is necesssary that the designer recognizes the fact. And it is also necessary to systematically establish staffs for the review separalety from the designer. |
| Knowledge Comment |
It is very abounding to err in the interval between the reinforcing steel, when the bar arrangement drawing is made. Read the design calculation book many times with attention. |
| 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 : \ 17358,000. |
| Multimedia Files |
Fig2.Bridge pier conceptual scheme
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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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