Leading engineers have expressed concerns about Autostrade’s plan to rebuild the collapsed Polcevera viaduct within eight months.
Following the fatal collapse which killed 43 people, highways operator Autostrade has vowed to rebuild the bridge, known locally as the Morandi bridge, in eight months and has set aside €500M (£450M) to do so.
But leading bridge experts have questioned the plan’s feasibility. Speaking to New Civil Engineer, Tony Gee & Partners group director Akram Malik and independent bridge consultant Simon Bourne agreed that £450M would be a big enough budget to construct a new bridge with similar spans. However, both have questioned how it could be built in such a short timeframe.
Malik said to build a new bridge would take at least 18 months on an extremely accelerated programme with no allowance for complications or logistical issues.
“I think it would take around six to nine months to do a proper design rather than the three they’ve suggested, then around nine to 12 months for construction if there were no complications,” he said.
“You could do it in 18 months if you started the construction of the foundations during the design period and use off-the-shelf designs which have already been approved elsewhere to save time. But even then, 18 months is a super accelerated programme.”
He added: “In this situation, any new structure they build, there’s going be close scrutiny, so how can you fast track the approvals in such a scenario?” he said. “In the UK there would be a Category 3 check which would take time to complete.
“I think the message should be we’re rebuilding this and we’re going to do it right.”
Malik also suggested that time could be saved by reusing the existing foundations, but questioned whether a designer would be willing to absorb the risk of such a tainted structure.
“I would really hesitate to reuse any of the structure as you’ve got no idea what else might be hidden in there,” said Malik. “I would shy away from it and produce my own design which I have control over. You know what the inspection process is, and there will be controls put in during construction.”
Bourne agreed, saying that to do justice to the design and to the bridge’s legacy, it would take a number of years to build a new bridge.
“I think a bridge of that size, assuming the planning was pushed through, then you could have planning and design done in 12 months and then the construction done in around two and a half to three years, that’s getting on for about five years,” said Bourne.
However, Bourne suggested that Autostrade’s eight-month timeframe could be plausible if the operator is planning on “plugging the gap” rather than building a new bridge.
He said a new bridge could then be built alongside it, but warned this would have its own challenges with having to realign the approach roads and convincing people the existing bridge was safe to use.
“In this situation, you’d build a brand new bridge so it would be the same challenges as doing it anywhere in the world, but it would be about restoring the confidence of the people in the existing bridge for the time when the other one was being built, which would be difficult,” he said.
However, simply building a section to connect the two collapsed sections and reusing the remaining bridge, either temporarily and permanently, is not an option according to University of Genoa professor Antonio Brencich.
“The big problem is what to do now,” said Brencich. “They were sure that according to the measurements that the [collapsed] tower was safe, and the measurements also say that the middle tower is safe, and it must be better because it didn’t collapse.
“But since the inspection failed on the western tower, you’re not sure of the results in the surviving tower.”
Brencich – who is involved in the ongoing investigation into why the bridge collapsed – said that the existing bridge should be completely demolished and rebuilt.
“I think one possibility is, the buildings below are not very good quality buildings or historical buildings, one solution is to not allow people to re-enter and to pay them for the buildings and then use explosives to demolish the existing bridge and then rebuild it,” he said.
Bourne also said another quicker option for the company might be to build a full temporary bridge, adjacent to the existing alignment. This could provide a quick but more utilitarian solution which would be acceptable in the short term while a more permanent structure was being built.
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