A damning Italian transport ministry report has blamed bridge operator Autostrade for the collapse of the Polcevera viaduct in August.
The report slams the highways operator for lacking the analytical expertise to inspect the bridge, claiming that Autostrade missed “warning signs” about the bridge’s condition.
The report lists a series of failings by the operator including a lack of sufficient analytical inspections and a failure to provide health and safety assessments. It also highlights discrepancies between statements released by the company and those examined by the government commission investigating the collapse.
The report says that Autostrade – which took private ownership of the bridge in 1999 – periodically monitored the bridge’s condition, carrying out “limited” investigations of a substantially qualitative type.
It says this meant Autostrade was able to grasp the evolution of problems but with “enormous uncertainties”. The report adds that these measures were “inappropriate and insufficient” considering the severity of the problems affecting the bridge.
“The presence, verified in the visual inspections [before the collapse], of some broken cables on the gaps of the buffer slabs, indicated that there was corrosion exposure.
“However, this unequivocal warning signal, did not result in the inspection of the cables being followed up on nor did the inspector make appropriate and adequate prudential provisions,” says the report.
“The ratio between the bridge’s load capacity and the actual loading (defined as the safety factor in the project documents) shows a decrease.”
Investigators also found that the inspection procedures applied to the bridge were still being applied to the rest of the Autostrade network.
The report details inspection and repair work undertaken on the bridge over its recent lifespan concluding that there was never an objective assessment of the degree of decay of the bridge’s materials and of their performance.
The report states that on 13 December 2016 Autostrade declared that after its inspections, none of its infrastructure was in a critical condition. It also says that on 23 June 2017, the company declared it had finished all evaluations regarding safety condition of its infrastructures without specifying if there were issues.
It also found a health and safety report due to have been completed in March 2013, was not done, as priority was given to infrastructure in higher risk seismic zones.
The investigation concluded that the bridge’s collapse was not caused by natural events, giving four possible hypotheses, including a collapse starting on the tower on the southern side of the bridge; a collapse starting on the west side of the “balanced system”; a collapse starting on the south-west side of the “balanced system” and a combination of deficient structural elements.
The report also says the difficulties assessing the structural elements that had collapsed was making it difficult to know if problems with materials were exacerbated by a “lack or wrong execution” of maintenance works or by structural problems due to transformation works done over the years.
In response Autostrade said the report did not clarify the causes of the collapse or how it happened. It said the charges laid against Autostrade had to be considered “mere hypotheses that need to be verified.”
The bridge operator has recently put forward plans to rebuild the bridge in eight months.
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