Autostrada Bridge collapses in Genoa.

[AM9]

Breaking news is that the 'Morandi' bridge, a concrete cable-stayed bridge on the A10/E80 that crosses the Torrente Polcevera has collapsed following a storm. No absolute figures of casulties have been reported yet by there are mainly industrial buildings underneath it's path. The bridge spans also cross the main rail route from the north that run down the Polcevera valley, crossing at the point of a very large group of sidings.
https://www.bbc.com/news/world-europe-45183624

A motorway bridge has collapsed in the northwest Italian city of Genoa and fire brigade sources say 35 people were believed killed as vehicles plummeted to the ground.

Dramatic video footage captured the moment of the disaster when one of the huge supporting towers crashed down during torrential rain.

Vehicles and debris fell 45m (148ft) on to rail tracks, buildings and a river.

Searches for people trapped in rubble are expected to go into the night.

 

[zoneking]

Sadly, La Republica reports 35 dead.

 

[Altfish]

This looks awful. Weather shouldn't bring a bridge down, there is an underlying reason that this has collapsed.

 

[Bletchleyite]

This looks awful. Weather shouldn't bring a bridge down, there is an underlying reason that this has collapsed.

Quite...the Tacoma Narrows was really quite a long time ago - that kind of thing is now the stuff of school science classes, not complex engineering.

There has to have been some kind of serious underlying defect. Somebody I suspect is very worried indeed at the moment.

 

[AndrewE]

Another news report says that engineering /repairs have been ongoing for a while now, however given the level of corruption in Italy (if that isn't racist) maybe it's surprising that more stuff doesn't fall down...

 

[Altfish]

Another news report says that engineering /repairs have been ongoing for a while now, however given the level of corruption in Italy (if that isn't racist) maybe it's surprising that more stuff doesn't fall down...

I've heard a report saying that repairs were being carried out to the foundations. !!!

 

[AM9]

I've heard a report saying that repairs were being carried out to the foundations. !!!

The bridge design was unique to it's architect, Riccardo Morandi and ever since its only sibling, the General Rafael Urdaneta Bridge in Venezuela was completed, other engineers have queried it's single encapsulated cable design. There's no immediate suspicion of corruption playing a part in the failure, other than the new populist Italian government looking for someone to blame. Well they would wouldn't they!

 

[Edgeley]

other than the new populist Italian government looking for someone to blame. Well they would wouldn't they!

I don't think a government which has been in office for a couple of months or so can be held responsible for construction failings dating back decades.

 

[30907]

I don't think a government which has been in office for a couple of months or so can be held responsible for construction failings dating back decades.

I didn't take that to be AM9's meaning - more a comment on politicians' soundbites (see these forums, frequently).

 

[AM9]

I didn't take that to be AM9's meaning - more a comment on politicians' soundbites (see these forums, frequently).

That's correct. The Italian populist regime wants to blame every problem in Italy on the last government to try and boost it's own credibility. They might be aiming at the Liguria regional administration which being in the 'rich' north would probably be seen as part of the establishment that they populists rail against.

 

[duesselmartin]

what trains are still running or what lines a severed?

 

[squizzler]

what trains are still running or what lines a severed?

Seeing that rail line underneath - only by the grace of God was there not a train running at the time, or the death toll could have been a multiple of the already tragic number yet to emerge.

 

[edwin_m]

The bridge design was unique to it's architect, Riccardo Morandi and ever since its only sibling, the General Rafael Urdaneta Bridge in Venezuela was completed, other engineers have queried it's single encapsulated cable design.

I guess a lightning strike if not properly conducted elsewhere could feasibly cause a cable failure. And once one cable had failed the unbalanced load could bring the tower down.

 

[Altfish]

I guess a lightning strike if not properly conducted elsewhere could feasibly cause a cable failure. And once one cable had failed the unbalanced load could bring the tower down.

Unlikely but if it hit a cable stay that was already in a bad state, I suppose it is possible.

Interestingly, it seems Italy's popularist government had in the run up to the last election called the safety fears about the bridge "a Fairy Story"

https://www.independent.co.uk/news/...-star-movement-league-populists-a8492201.html

In 2013 a statement on the party’s website described warnings of “the imminent collapse of the Morandi Bridge” as a “favoletta”, an Italian word meaning a children’s fantasy tale or fairy story. The bridge collapsed on Tuesday killing at least 39 people and severing the country’s A10 motorway.

The statement has since been deleted from the party’s website, but a cached version is still visible online. It was drawn up in opposition to the “Gronda di Genova”, a major infrastructure project to improve the motorways in the city region that included work on the now collapsed bridge.

 

[northwichcat]

There's rumours the concrete was substandard and supplied by associates of the mafia.

 

[Altfish]

There's rumours the concrete was substandard was supplied by associates of the mafia.

I'd have been more surprised if the Mafia weren't involved.

 

[LeylandLen]

Looking at TV pictures , now that there are live broadcasts from there, the supporting legs on the remains dont exactly impress me as to
their construction or inspire me with confidence . Condolences to relations of those that lost family members.

 

[LNW-GW Joint]

I haven't got my Schweers atlas with me, but the bridge appears to have collapsed on to the main route north from Genoa to Milan and Turin.
I think the coastal line (Genoa-Ventimiglia) is unaffected (except that many trains run through from Ventimiglia to Milan).
Apparently they have cleared the route sufficiently for trains to run, which seems remarkable.
The Trenitalia web site is saying long-distance services are restored with 60-120 minutes delay, with some local trains cancelled.

• Line Genova Piazza Principe – Arquata Scrivia (direction Turin and Milan): active circulation but slowed, with average delays of 60 minutes with peaks up to 120, and some regional trains cancelled.
  
  
• Genoa – Savona – Ventimiglia: active circulation.
  
  
• Ovada Line – Genova Piazza Principe: movement suspended between Genoa Borzoli and Genova Piazza Principe. Trenitalia launched a replacement bus service between Ovada and Genova Voltri

http://www.fsnews.it/fsn/Gruppo-FS-...genova-crollo-ponte-informazioni-circolazione
(using Google translate)

 

[duesselmartin]

Possible diversion?

 

[RichJF]

I would hazard a guess at substandard Italian concrete being supplied from dubious sources + an intrinsic design flaw in the concrete cable stay as a result of age/weather/structural fatigue.
A possible lightning strike would expose the metal to stresses that could cause it to fail & thus completely weaken the structural integrity of the bridge. I read a report that in the 60s bridge designers didn't fully understand concrete could become susceptible to aging & decay, they thought it would be futureproof.
Some of the pictures of the bridge before the collapse are shocking with bare metal exposed on connecting segments, cables dangling down & suspicious marks on the towers.

They're actually demolishing & replacing the Ponte Amerigo in Colombia as it's unsafe in an engineering respect. The Wadi El Kuf in Libya was closed in 2017 over fears it would collapse!
The Morandi's Venezuelan cousin (Urdaneta) has had serious doubts raised about its long term integrity and longevity combined with no maintenance for decades.

 

[Craig2601]

Yes, the route under the bridge is the route from Genova to Torino/Milano, trains to Ventimiglia run along the coast on a different route so should be unaffected. Scary to think as I was on that railway only a matter of days ago!

 

[urbophile]

Possible diversion?

There are a couple of alternative routes that run up the Polcevera valley, but both underneath the collapsed bridge. If you know the local geography you will know that getting a railway line anywhere else than through the valleys or along the coast is next to impossible. And both those are difficult enough, with tunnels and bridges galore. Indeed the motorway disaster wouldn't have happened without the need for a bridge at that dizzy height.

However, the map shows a secondary line from Genova to Alessandria via Ovada. I can't work out whether that branches off the coastal mainline west of the city, or heads north first, in which case it too might be underneath the bridge. Anybody more au fait with Ligurian railways able to answer?

 

[eastdyke]

A tragic event.

I really do not understand the use of concrete to encase the stay cables.
It must have been purely part of the aesthetics of the design, sure makes any inspection and NDT testing a real headache.

It seems that the stays from the pylon at the eastern end of the bridge were augmented with an array of cables external to the concrete circa early 90's.
Google street view:
https://www.google.com/maps/@44.423...4!1sn9xn605XsTJO2KEZQQkktg!2e0!7i13312!8i6656

The bridge of similar design in Venezuela had cable stays replaced just 18 years after construction.
From this 1994 (by which time note that the replacement strands were again under threat!) 'Technical Advisory' put out by US Department of Transportation:
https://www.fhwa.dot.gov/bridge/t514025.cfm

Cable stays of most, if not all, early cable-stayed bridges consisted of zinc-coated or galvanized locked-coil strand, e.g., the Lake Maracaibo Bridge in Venezuela (constructed in 1962). In many cases, these strands also had a paint coating. Zinc coating or galvanizing has the advantage that it is not easily damaged in handling and installation and is relatively inexpensive. However, it is a sacrificial coating, i.e., it is consumable with time in an aggressive environment. In the harsh environment of Lake Maracaibo, the galvanized locked-coil strands had to be replaced in 1980 after 18 years of service and currently, the replacement strands are being threatened once again by corrosion.

For some time now, a new bridge has been proposed in Venezuela but I guess the cash is even more difficult to find there.

 

[Bletchleyite]

The design is more than a little bizarre (like many Brutalist style buildings) - too few cables and the concrete thing. But it wasn't the stay cables that failed, it was the supporting tower's foundations, wasn't it?

 

[eastdyke]

The design is more than a little bizarre (like many Brutalist style buildings) - too few cables and the concrete thing. But it wasn't the stay cables that failed, it was the supporting tower's foundations, wasn't it?

Who knows the way that the collapse was initiated? We get to find that out later.
As ever probably a combination of factors triggered by something(s) on the day that exploited weakness(es) resulting from other things that should have been (or not have been) done sometime over and during the last ~50 years.

 

[axlecounter]

Last-minute-expert warning: what’s below comes from what I’ve read and learned these last days and nothing more!

Could have been many things and probably all toghether. From how brutally the bridge collapsed people are at the moment supposing that it started at stays and/or road level. At some point something triggered in some way a stay(s) break , the bridge (due to its design) immediately and completely lost all (!) of its balance and collapsed. That’s what I’ve read more often and what seems IM(very)HO a plausible explanation.

The cables are incapsulated in concrete because it is prestressed concrete: https://en.m.wikipedia.org/wiki/Prestressed_concrete
That is to say, the stays were actually designed to be made of concrete, hence the use of the prestressed type which should (and does) resist to tensile forces, a thing at which normal concrete isn’t good at.

 

[axlecounter]

Warning similar as above...

There are a couple of alternative routes that run up the Polcevera valley, but both underneath the collapsed bridge. If you know the local geography you will know that getting a railway line anywhere else than through the valleys or along the coast is next to impossible. And both those are difficult enough, with tunnels and bridges galore. Indeed the motorway disaster wouldn't have happened without the need for a bridge at that dizzy height.

However, the map shows a secondary line from Genova to Alessandria via Ovada. I can't work out whether that branches off the coastal mainline west of the city, or heads north first, in which case it too might be underneath the bridge. Anybody more au fait with Ligurian railways able to answer?

Here’s a useful map (colors by Andmart@ferrovie.it)

In yellow-orange what was already interrupted for various engineering works. In red the lines interrupted by the bridge. In light green the single track line that remains as only “straight” way to go to Turin/Milan (via the older pass line:
https://en.m.wikipedia.org/wiki/Turin–Genoa_railway ).
The line via Ovada is needed for all the goods traffic, and was already planned like that because of the engineering works closure of the second pass line (the older line has excessive gradients for them).

 

[AndrewE]

A tragic event.

I really do not understand the use of concrete to encase the stay cables.
It must have been purely part of the aesthetics of the design, sure makes any inspection and NDT testing a real headache.

It seems that the stays from the pylon at the eastern end of the bridge were augmented with an array of cables external to the concrete circa early 90's...

The design is more than a little bizarre (like many Brutalist style buildings) - too few cables and the concrete thing. But it wasn't the stay cables that failed, it was the supporting tower's foundations, wasn't it?

I didn't understand the concrete stays either - so I assumed too that the work was being done by steel in tension (good) just clad in concrete (useless in tension) for the visual effect. Pre- or post-stressing concrete helps it resist bending, has no effect on overall resistance to tension beyond the strength of the steel that has been added! I also wonder whether it was assumed the concrete (alkaline) would protect the steel from corrosion indefinitely.
Then low quality concrete degraded and got porous, allowing the steel to corrode, getting thinner... finally a lightning strike runs down the thinned-out steel and melts the thinnest bit. The problem with that is that we were taught at school that current flows along the outside of a conductor, so you would think it would have flowed along the outside of the wet concrete. I think the foundation repairs might have been a mis-translation somewhere, it could have been work on the bracing struts at the base of the towers.

Has anyone else noticed the similarities to the Forth Railway Bridge? Big towers with cantilever arms and short simple spans between them. The video I watched showed some of the approach spans already missing, then a tower being pulled down towards the gap. Maybe a deck joint failed and the falling spans pulled down the tower by dragging some of its structure out on one side?

 

[eastdyke]

The cables are incapsulated in concrete because it is prestressed concrete:
That is to say, the stays were actually designed to be made of concrete, hence the use of the prestressed type which should (and does) resist to tensile forces, a thing at which normal concrete isn’t good at.

Sure, I accept that the cables were encapsulated in concrete and that was in theory prestressed, but the main strength in each stay was the cable(s). Not sure whether the stays were anchored to the pylon top or employed the saddle arrangement generally used in early cable stayed bridges.
Some more reading if you are interested:
New Civil Engineer (you may need to refresh your broswer if you are not a subscriber and want to 'read this more than once'):
https://www.newcivilengineer.com/la....article?blocktitle=Most-popular&contentID=-1
https://www.newcivilengineer.com/la...struction-photos-and-designs/10034288.article
Has some pictures taken during construction, including working at height on the partially completed bridge over live railway yards. They certainly did things differently back then.

 

[edwin_m]

As I understand it the idea of prestressing is that the cables are stretched before the concrete is poured around them. When everything sets the tension on the cables is removed so the cables try to spring back and in doing so hold the concrete in compression even if there is some external tension applied to it. I was told by a structural engineer of my acquantance that prestressed concrete has a tendency to fail without warning, presumably if the bond between the cables and the concrete is weakened so the concrete is no longer in compression and fails under external tension. I guess prestressed concrete could theoretically be used for a "cable" stay supporting a bridge and therefore in tension, but I've no idea whether this is done at this bridge or indeed anywhere else (isn't there a small concrete cantilver former railway bridge on the Ballachulish branch?).

It does indeed look as if it operates on the principle of the balanced cantilever, and therefore any significant unbalance such as the loss of the span on one side could cause the tower to topple. The same is also theoretically possible with the Forth Bridge but that is a much heavier construction with no concrete (except maybe in the piers) or cables.