| Case Name |
Unilateral arch member ( 41m length, 100t weight ) in the middle point fell in the valley during 50m erection |
| Pictograph |
|
| Date |
December 4, 1992 |
| Place |
The Hiroshima Prefect. Onomichi City |
| Location |
The bridge erection field of the expressway |
| Overview |
The unilateral arch member suddenly fell in the valley below about 50m, during the erection of the arch part of the reverse Lohse bridge of the expressway by the cable election suspension method. 3 workers on the bridge fell down with a member and avoided falling into the valley, but received the serious or slight injury. There were same 2 bridges, and one line erectionwas finished. |
| Incident |
At around 14 o'clock, on December fourth, 1992, 3 workers on the bridge fell down with a member and avoided falling into the valley, but received the serious or slight injury. |
| Sequence |
* It occures during the erection work which the arch members jettyed from both sides of the valley by the each 1 block with supporting by the wire from the upper of the steel tower .
* The overhang of the 4 block from both sides was finished by the day, and they worked to change the suspension wire of the left arch member from second panel point to fourth panel point.
* Changing the eastern wire was finished in the morning and they tried to remove the west wire from the second panel point, then the suspension steel tower suddenly leaned toward the front and collapsed with the arch member. |
| Cause |
* The distance of each 8 wire clips of rear cable for the fixation of edge of the wire became narrower than 30cm(at the beginning) after the accident.
* The tightening of the wire clip of the rear cable was insufficient, because it was expanded for about 5m by the slip. |
| Countermeasures |
The fallen member of the arch was newly manufactured, and the erection was carried out by the same construction method.
The prevention of recurrence countermeasure:
* At the rear cord they increased the number of tightening wire clips, and the supervisor carried out the visual observation inspection management for the work of tightening, etc. at every erection stage.
* For the management of the tensile force of the suspension steel tower, the adjusting device was installed at the rear cord.
* They changed the frontsuspension wire to the multipoint suspension structure which did not need the spare height.
* The edge of the front cord wire which was difficult to be tightened was stopped by the alloy socket stop after fitting the wire clip.
* They stationed persons with the sufficient experience and technology and skill as both the management supervisor and workers, and the perfect management system was laid. |
| Knowledge Comment |
* The tightening of the wire clip is carefully executed in loading because the cross section of the cable decreases by the tension.
* The management supervisor should see the tightening and confirms it directly.
* The scaffold for the tightening work is considered from the plan stage and always available. |
| Background |
* With the expressway bridging work in the mountainous area, they should not adopt "the truck crane method" which was a general method because of the problem of the landform, and adopted difficult "the suspension cable election method. "
* Their carelessness was produced, because they finished the erection of the up lane in the similar method, and the thoughtless management was carried out.
* Though the field deputy was a veteran with experience of 20 years, he used this method for the first time. |
| Sequel |
3 construction chief directors of the principal contractor, 1 person of first supplier company, and 4 of secondary supplier company were sent the report of professional negligence, and the supplier company and the field operator of this company which let cable crane run in the disqualification were sent on suspicion of Industrial Safety and Health Law contravention. |
| Incidental Discussion |
On the cable election method, the consciousness of all workers is apt to be concentrated. Then, the managers should confirm backward. |
| Account of Concerned Parties |
The manegement of the facility, the machine, and the workers had been entrusted to the subcontract. They should strengthen their technical strength and field management system as the principal contractor. |
| Scenario |
| Primary Scenario
|
Ignorance, Insufficient Knowledge, Carelessness, Insufficient Precaution, Poor Value Perception, Poor Safety Awareness, Organizational Problems, Poor Staff, Regular Operation, Erroneous Operation, Regular Movement, Careless Movement, Failure, Large-Scale Damage, Bodily Harm, Harm to Physical Well-being, Bodily Harm, Injury, Loss to Organization, Social Loss
|
|
| Sources |
* Nikkei construction, 70 examples of significant construction accident, p28.
* Failure knowledge DB promotion committee construction field research council, Japan Bridge construction association presentation material
|
| Number of Deaths |
0 |
| Number of Injuries |
3 |
| Field |
Civil Engineering
|
| Author |
NABESHIMA, Hajime (Japan Bridge Association)
|
