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Morandi Bridge: A Risk Thinking Example

Posted in on
March 30, 2021

Author: Ron Dembo

Sitting behind the wheel of his green and blue Basko Supermercati delivery truck on August 14, 2018, Luigi Fiorillo looked up at a darkening sky. The weather had worsened throughout the morning, and as he completed his deliveries around the Mediterranean port city of Genoa, Italy, a torrential thunderstorm had broken across the Liguria region.

He flicked the windshield wipers up a notch and peered ahead. The Morandi Bridge loomed.

Designing a Concrete Behemoth

Named after its designer, Italian architect Riccardo Morandi, the kilometer-long bridge had been an architectural landmark since its construction in 1967. One of the designer’s innovations was to use pre-stressed rather than regular concrete to cover the individual cables. This was specifically designed to resist traction, and, as a result, the bridge was stronger, lighter, and used less steel than any other design at the time, helping to earn Italy its reputation as the nation that could bend concrete.

“The bridge’s structure won’t need any maintenance”, forecast an article in La Stampa newspaper before the opening. “Neither will its stayed cables, which are protected from atmospheric agents by their concrete vest.”

It was a bold prediction. But little was known in the 1960s about the effects of pollution and climate on corrosion.

Early Warnings Go Unheeded

Morandi, however, had been surprised upon a visit to his bridge in 1979 to find that pollution from the factories nearby and the salty sea air were aging the structure faster than he had expected. We must “remove all traces of rust on the exposure of the reinforcements, fill the patches with epoxy resin, and cover everything up with elastomer of very high chemical resistance”, he wrote urgently in a report.

Yet Morandi was ignored. The state-owned Autostrade per l’Italia opted for the cheap route, adding extra cables around the corroded ones rather than replacing them while failing to retrofit the others.

Scoffing at claims from experts about the bridge’s status in 2012, the soon-to-be Italian transport minister Danilo Toninelli said the warnings were just a fairy tale because a recent assessment by Autostrade said that the bridge “could last for another hundred years”.

Calamity Strikes

Luigi was thinking about none of this, however, as he drove around Genoa that morning. By the time it got to 11:30am, the storm was at its height and a thick mist had descended around the bridge, obscuring the towers and their corroded cables in the distance.

He pressed on. Ahead, the highway was busy. A few cars in front of him, battered by the wind and lashings of rain, had slowed to a crawl and were approaching the crossing hesitantly. On his left, a car overtook him and sped off into the mist.

“It was raining very hard and it wasn’t possible to go very fast,” he later informed the Corriere della Sera. “When [the] car overtook me, I slowed down… [then] at a certain moment everything shook. The car in front of me disappeared and seemed to be swallowed up by the clouds. I looked up and saw the bridge pylon fall,” he said. “Instinctively, finding myself in front of the void, I put the van into reverse to escape this hell”.

He didn’t get far before abandoning his vehicle and fleeing on foot.

Hundreds of others had not been so fortunate. Halfway over the bridge when the cables gave way, they, and a 200-metre section of concrete, had been plunged into the valley below.

Was Prevention Possible?

Luigi could never have known the exact moment in its decades-long lifespan that the bridge would collapse – it was an extreme event, the result of a non-stationary stochastic variable (radical uncertainty).

Neither could Autostrade have known. And yet both were given the opportunity for risk management – one on a short-term individual scale, the other on a long-term corporate governance scale. Only Luigi risk-thought successfully, however. He did not know what radically uncertain event might occur on a bridge covered in fog with rain pouring down, so he hedged by slowing to a crawl. It was a hedge that ultimately saved his life.

Autostrade, on the other hand, failed to risk think appropriately. They had ignored the advice of experts, boldly forecast that the bridge would last for another one hundred years, and bet that they would not need to undertake the more expensive maintenance options. Did they really appreciate the downside of that bet? Ultimately, it cost 43 people their lives, put their company under investigation for culpable homicide, and catalyzed its nationalization.

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