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Engineering Experts Knew Italian Bridge Had Corrosion Problems Before It Collapsed, Report Says (apnews.com)
McGruber shares a report: Engineering experts determined in February that corrosion of the metal cables supporting the Genoa highway bridge had reduced the bridge's strength by 20 percent -- a finding that came months before it collapsed last week, Italian media reported Monday. Despite the findings, newsmagazine Espresso wrote that "neither the ministry, nor the highway company, ever considered it necessary to limit traffic, divert heavy trucks, reduce the roadway from two to one lanes or reduce the speed" of vehicles on the key artery for the northern port city. A large section of the Morandi Bridge collapsed Aug. 14 during a heavy downpour, killing 43 people and forcing the evacuation of more than 600 people living in apartment buildings beneath another section of the bridge.
If corrosion weekend the cables by 20% of so, it seems like the original design didn't leave nearly enough margin for error!
I imagine they were not as concerned with 20% weakening thinking they had much more leeway.
It’s not just that, the bridge was hopelessly overloaded by traffic. There is a longstanding bypass project which has been fiercely opposed by the Five Star Movement for years. The Five Star Movement’s leaders, who now run Italy, actually cracked jokes about warnings that this bridge might collapse at regular intervals since the first warnings in 2012 or 2013. They are now trying to blame the EU (which gave them money for infrastructure sanitation) for the whole ugly mess.
It's been a lot of years since engineering school, but I seem to recall the recommended safety margins for most things were 100%-500%, so yes, a 20% weakening causing collapse would be a symptom of serious under-engineering.
However, Wikipedia says this bridge is 51 years old, and that engineers have been expressing concern over its safety since the early 90s, with numerous other static and dynamic weaknesses being uncovered over the years, due to both degredation, and weakness in available computer modeling in the 60s.
Apparently traffic has quadrupled since it was built as well, so it's probably been under a lot more stress than it was really designed for. And to top it all off, eye witnesses say it was struck by lightning just before the collapse - and I would imagine conducting that kind of amperage (~30kA typical) could heat a cable enough to weaken it considerably. You'd think good engineering would factor in lightning strikes on a tall bridge like this, and they probably did, but it was probably just one stress too many on an old bridge.
--- Most topics have many sides worth arguing, allow me to take one opposite you.
If the bridge was only over-engineered by 20%, then it would be a disaster to keep using it.
It seems like the engineers have been opposed to this bridge design from the beginning, pointing out the impending disaster since 2012, and advising limiting traffic and building an alternate route. But good luck getting politicians in a democracy to spend money on infrastructure (even when given money by the EU specifically for infrastructure).
Socialism: a lie told by totalitarians and believed by fools.
AvE posted a great video on this bridge. The designer of the bridge didn't like adding extra reinforcing. This was probably for aesthetics. This made maintenance of the bridge difficult as structural components couldn't be repaired while the bridge was in service.
One of our competitors trademarked the term "hypothesis". From now on, we will call them "boneheaded ideas".
They both failed at their jobs resulting in loss of life, by the sound of it.
If by "failed" you mean "consistently warned about the impending disaster for the past 6 year, while politicians openly mocked the warnings", then sure.
And maybe both will see jail time
Probably so. It's not like the politicians who blocked funding of an alternate route are going to let any consequences affect themselves.
Socialism: a lie told by totalitarians and believed by fools.
Though I generally agree with your assessment of the issues there are a few I can take an alternate view of.
First is that the strike to the cables would not have lasted long enough to cause heat induced weakening of them, But... The high current upon entering the the wet concrete could have caused the water to flash over to steam and maybe induce cracking in the structure.
Second is the rebar embedded in the concrete supports has definitely corroded leading to weakened bonding and compromised structure internally. All concrete structures suffer this issue over time. Some deal with it by using epoxy coated rebar, some use composite rebar, and others use stainless steel to stave off this inevitable failure.
Third is that the bridge was carrying four times the original traffic it was designed for and at speeds likely far in excess of those thought prudent at the time of design and build. This again added to the stressed induced on the structure and I would submit accelerated its failure.
It is very likely that there were one or more engineers blowing the caution horn for some time now. It is also likely that they were flatly ignored, removed from the job, or sent elsewhere to silence them. Nice to see that the higher ups that lost their jobs at Morton Thiokol found new places to work and ways to kill others.
The bridge's sorry state was known years ago. A certain political party used the "environmentalist" demagoguery to keep the status quo.
And now the same people are blaming the company that built and maintained the structure:
Because the government is so good at everything...
In Soviet Washington the swamp drains you.
Itâ(TM)s not just that, the bridge was hopelessly overloaded by traffic.
Have you ever driven in New York City? Every bridge is totally full of traffic nearly 24x7, during rush hour basically parked (it took me an hour once to cross George Washington bridge leaving NYC near rush hour). That happens every day, including in driving rainstorms... bridges are usually built assuming the bridge is packed with trucks, during the worst storm imaginable (including many feet of snow, far worse than rain), then use safety margins well beyond that. It seems the designers of this bridge cut some corners.
I’ve driven in all kinds of places. However, the real question is: Have you ever observed the dysfunctional cocktail of corruption, populism and incompetence otherwise known as Italian politics at work? In this case you have a steadily deteriorating bridge whose load carrying capacity is rapidly decreasing, that may not have been built to specs in the first place due to corruption and that was being subjected to traffic loads and thereby vibrations that its decayed structure could not handle. And the whole time there is a political cat fight going on with a bunch of populists wingnuts who are blocking the replacement bypass project, staging protests against any repair work and ridiculing anybody who spoke out about the danger of the situation. The bottom line is that this bridge should have been replaced and decommissioned at least ten years ago.
It was designed by Calatrava
The Ponte Morandi bears the name of its designer:
Riccardo Morandi
"Bridges by Morandi have proved to require extensive maintenance and repairs over the years to pass bridge safety inspections. The third span of Ponte Morandi collapsed in Genoa, on 14 August 2018, causing 43 fatalities."
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