| Case Name |
A 60m long, 60 ton steel box girder fell 10m onto a prefectural roadway below |
| Pictograph |
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| Date |
March 14, 1991 |
| Place |
Hiroshima, Hiroshima |
| Location |
Hiroshima elevated rail track "New Transportation System" construction site |
| Overview |
At the Hiroshima City "New Tranportation System" construction site, in the course of lowering a box-type bridge girder using the "side-loading and lowering construction method", the jack and its mount supporting the main girder slipped out of place, allowing the girder to fall onto the prefectural road below. As a result, eleven mortor vehicles waiting for the traffic signal to change were crushed, injuring and killing a total of twenty-three persons. |
| Incident |
At around 14:05 on March 14, 1991, at the Hiroshima City elevated rail track "New transportation System" construction site, a steel box girder 63.4 meters long and weighing 60 tons fell to the prefectural roadway below, tregically killing fifteen people (including ten citizens unrelated to the construction) and injuring eight others. |
| Sequence |
* The jack mount had a triple tier of steel H-beams stacked in the same direction (normally each tier would cross the previous one at a right angle). The H-beams also lacked reinforced ribs.
*The girder deformed since a non-reinforced section was in direct contact with the jacks.
* Two of the three jacks supporting the main girder experienced a change of fulcrum force, and at that instant, one of those two was loaded beyond its ability to withsatnd the weight.
* The remaining jack could not support the reaction, so that two jacks collapsed at virtually the same instant.
* While executing a half turn around the bridge axis, the girder fell to the prefectural road below, crushing eleven motor vehicles that were waiting for the traffic signal to change. |
| Cause |
* Three tiers of steel H-beams stacked in the same direction were used as temporary jack mounts.(Fatal cause)
* Materials where load force was concentrated were not reinforced with shear reinforcement ribs, and jacks abutted sections that were not reinforced with shear reinforcement ribs.
* Wires were attached to prevent the girder from falling during side-loading; however, this countermeasure was not in place during the lowering operation.
* The root cause was construction management system of the prime contractor. |
| Countermeasures |
* Do not stack steel H-beams in the same direction for the supporting load.
* Install shear reinforcement ribs on components bearing concentrated loads.
* Attach wires to prevent girders from falling. |
| Knowledge Comment |
* Never stack H-beams in the same direction.
* However, the same mistake will probably be repeated.
* The construction industry faces a challenge concerning how seriously it will take this situation.
* Safety is "culture".
* Safety is the result of daily attention to details. |
| Background |
Sloppy safety management is seen as a crucial problem behind this accident.
* First, the selection and oversight of the subcontractors were sloppy. The first subcontractor had never contracted for construction of elevated structures, and although almost half of the workers on this project were veterans with twenty years or more experience, despite having virtually no prior experience in construction of an elevated bridge, no advance instructions were given by the prime contractor.
* Among the problems with the construction management system, no employees of the prime contractor were providing supervision atop the bridge pillars, and the overall supervisor was a clerical employee of the first subcontractor. Also, according to the construction plan prepared by the prime contractor, insufficient deliberation of work procedures was carried out, and concerning the "side-loading and lowering method" there was merely the inscription "3(d) Side-loading" in the "Election Guidelines" of the attached diagrams.
* Employees of the secondary subcontractor that installed four of the five jack mounts
in this accident had more than thirty years' experience as scaffolding men; however,
they had no prior experience with assemblage of mounts in high places.
* This construction work began on February 20,1991; however, until March 1st the scaffolding
men scheduled to work either arrived late, or failed to show up at all on consecutive days,
and as a result the work was behind schedule. After March 2nd, the workforce was mostly
stabilized; however, many of the workers had no prior experience working in high places.
At other work sites, in the morning meeting prior to commencement of the day's work,
the day's work was reviewed and explained, and through danger forecasting activities the
key points for danger forecasting activities were conducted other than an explanation of
work procedures immediately prior to the side-loading of March 13. Also, morning meetings
were never held. |
| Sequel |
Since the roads around the site carried traffic of 15,000 vehicles per day, construction was being carried out without the total interruption of traffic; however, after the accident a detour was arranged and the prefectual road at erection point was totally closed to traffic, with guard rails installed to create an exclusive truck lane.
- Litigation concerning indemnification to the families of the victims saw the prime contractor, the first subcontractor and the owner of the construction project (Hiroshima City) admit their negligence in the Hiroshima District Court on March 24, 1998, and the court ordered payment of damages. In the judges' decision, the Hiroshima District Court affirmed both foreseeability and precautionary obligations on the part of the Hiroshima City, and awarded damages on the basis of negligence of precautionary obligations.
- In addition, in criminal proceedings, prime contractor's site manager was sentenced to two years and six month's imprisonment, while director of bridge construction division and site manager's assistant were given two years' imprisonment with probation of four years, respectively.
- The prime contractor was banned from government contracts as an administrative
penalty, and ordered to suspend business. |
| Incidental Discussion |
After the accident occured, the safety and health related laws were ammended as a part
of the countermeasure to prevent the same accident reoccurrence. The main content of
these changes was the addition of requirements that a person in charge be appointed for
dangerous elevated erections, and advance notification be given of construction plans. |
| Reason for Adding to DB |
To stop repeating the same mistake over and over again. |
| Scenario |
| Primary Scenario
|
Poor Value Perception, Poor Safety Awareness, Organizational Problems, Poor Management, Insufficient Analysis or Research, Insufficient Prior Research, Regular Operation, Erroneous Operation, Regular Operation, Erroneous Operation, Failure, Deformation, Bodily Harm, Death
|
|
| Sources |
Judicial Precedent Times, Vol. 988, page 215.
Nikkei Construction ed., Construction accidents - Learning from 70 cases of major disasters to prevent them from repeating pp 14-19.
Data submitted to Failure Knowledge Database Construction Business, Civil Engineering Research Committee handouts.
|
| Number of Deaths |
15 |
| Number of Injuries |
8 |
| Physical Damage |
11 vehicles crushed |
| Consequences |
This accident was broadcast on the TV to reveal the sloppy management at construction sites, and the impact on the society was huge. |
| Notes |
Hiroshima City appealed the Hiroshima District Court decision; however, the families of the victims dropped all claims against Hiroshima City, hoping for an early resolution after having obtained a complete award of all claims against the prime contractor, so the appeal never went into actual deliberation. Through the abandonment of claims, the part of Hiroshima City in the lower court decision is lost its effect. |
| Field |
Civil Engineering
|
| Author |
KUNISHIMA, Masahiko (The University of Tokyo)
SONG, Hubin (The University of Tokyo)
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