Why did the Genoa bridge collapse? Engineering experts weigh in on disaster that left 35 dead

Many other bridges across the world use similar designs

It is too soon to know why a bridge in Genoa collapsed in a horrifying disaster – but the same problems could potentially afflict other bridges, experts have warned.

Respected experts are clear that it is far too early to speculate on the cause of the bridge's collapse. But they said that a thorough investigation will be required to ensure that the full causes of the incident are known – and any similar incidents in the future are prevented.

“At this stage it is very difficult to make a solid judgement on the cause of this catastrophic collapse," said Mehdi Kashani, associate professor in structural mechanics at the University of Southampton.

But Dr Kashani said that there are a range of bridges across the world that use many of the same techniques.

"The bridge was constructed using reinforced and pre-stressed concrete about 50 years ago. There are a large number of reinforced concrete bridges in Italy, Europe, USA, and Canada with the same age, which are suffering from corrosion of reinforcement and or pre-stressing tendon."

Further investigation will be needed to know whether that helped contribute to the bridge's collapse, or if those similar bridges could ever suffer the same fate. There are a whole host of issues that could potentially be involved – from corrosion of the reinforcement in the bridge; the loads they undergo from traffic, wind and earthquakes that can gradually put fatigue on the structure; the effects of the storm that was happening at the time of the collapse; as well as work that was reportedly ongoing on the bridge.

"However, there is need for further detailed investigation to fully understand the cause of failure," he said. "The bridge engineering research community should take this seriously in their future research to improve the resilience of our infrastructure under extreme loading.”

While some of the materials and techniques used in the bridge's building are very common the design itself is relatively strange. That might limit the applicability of the dangers in this case to other bridges across the world, experts said.

“The bridge is a very unusual design, very similar to its much larger cousin, the Lake Maracaibo bridge in Venezuela, also designed by Riccardo Morandi and completed 6 years earlier in 1962," said Ian Firth a past president of The Institution of Structural Engineers, and a structural engineer specialising in bridges.

"The A-frame towers which support the concrete-encased stay cables combine with V-shaped supports below the deck to create a stiff arrangement which is not common in cable stayed bridges. This deals with potential unbalanced loads which arise due to the multi-span nature of the structure.

Some online reports have suggested that the collapse could have been caused by a strike from lightning. Such impacts can be devastating – but not enough to cause such problems by themselves, experts said.

"Whilst it is perhaps not impossible to think that a lightning strike makes a contribution to such a collapse, it is probably very unlikely to happen," said Martin Fullekrug, reader in the University of Bath’s Department of Electronic & Electrical Engineering.

"Lightning could potentially contribute to a critical fatigue of material. For example, the lightning generated heat could result in evaporating water to very high pressure and produce a subsequent crack or burst of critical support material, similar to the bark of a tree disintegrating after a lightning strike."