Italy’s road operator Autostrade has said that “work to shore up the foundations” was underway at the Morandi Bridge at the time of its collapse earlier today.
At least 39 people were killed when the deck and one of the towers on the A10 motorway bridge in Genoa suddenly failed at around 11.30am local time but the death toll is expected to rise.
The failure caused a 100m to 150m section of the concrete deck on the bridge, which opened in 1967, to fall around 45m onto railway tracks and a factory below.
Autostrade has confirmed that foundation work to “consolidate the slab” was currently being carried out but said that the bridge was being constantly monitored by Direzione di Tronco di Genova.
The failure occurred after a period of heavy rainfall but there is no evidence that the weather or the foundation works were a contributory factor at this stage.
Former president of the Institution of Structural Engineers Ian Firth said that the bridge was “an unusual design”.
According to Firth, it is too early to say what caused the tragic collapse, but as this reinforced and pre-stressed concrete bridge has been there for 50 years, it is possible that corrosion of tendons or reinforcement may be a contributory factor.
He added that the storm taking place at the time and the ongoing work on the foundations may or may not be relevant. “We simply do not know yet,” he said.
Sydney Lenssen, who was founding editor on GE’s sister title NCE, told NCE that he believes that there may be other factors at play.
Lenssen said that he obtained a report on the design during a visit to the Morandi bridge mid-construction in April 1965, in an organised tour promoting the use of concrete in long-span bridge construction. Lenssen said that there were several “unusual” structural design elements which may have contributed to the bridge’s collapse.
“At first look it doesn’t look like a fault in the foundations,” Lenssen told NCE. “It appears to me that the structure has fallen down from above. So it looks like the structure has collapsed around the foundations, rather than the foundations causing the collapse.
“I suspect that one of the supports from underneath has given away. That or the cables above have suffered from corrosion.”
Lenssen, who previously worked as a structural engineer, also told NCE: “Morandi was convinced that covering the steel cables would protect them but it looked very strange. The concrete casing was also built in two or three sections and I was straight away concerned how this would protect the cables from corrosion.
“All suspension bridge cables suffer from corrosion, regardless of whether or not they are covered in concrete.”