Genoa bridge collapse

[roadtester]

Hence the idiot BBC reporter yelling at the Italian PM: "Why did the bridge collapse Prime Minister?" during a press scrum.

Why idiotic? It seems like the most obvious question to ask.

Of course, it is unlikely that anyone has the definitive answer yet, but if the PM did have something to say on the subject, the press would look like idiots if they had failed to ask the question.

I seriously doubt the PM knew the answer. I also think that sort of behaviour (shouting questions at politicians) is just idiotic. Do they really think the subject of their interrogation is suddenly going to blurt out the answer? I'm all for holding politicians to account but that just isn't going to work. Sorry for the OT rant but this is one of my bugbears.

Journalists not asking questions? What a bizarre notion.

[bothar]

Journalists not asking questions? What a bizarre notion.

Journalists asking useful questions? What a bizarre notion.

[roadtester]

Journalists not asking questions? What a bizarre notion.

Journalists asking useful questions? What a bizarre notion.

So the BBC journalist is supposed to sidle up to the Italian PM apologetically and say "I don't suppose you know anything about the bridge collapse, so I won't bother asking you about that. How was your lunch?"

[Steve in Cumbria]

One of the dashcam videos shown on BBC showed the tower collapsing, very unevenly, and taking the roadway with it.

I've only seen the blurry phone footage taken from afar which shows the A-frame towers falling over and the even blurrier traffic cam at the tunnel entrance on the western side of the valley.

[Edited to remove tin-foil hattery]

[c2R]

As of last night, La Repubblica was reporting that Autostrade plans to have a replacement for the missing segment in place within five months. Considering that the I-35W bridge was replaced in fourteen months even after months of time on site lost carefully removing fragments of the collapsed structure for NTSB investigation, I wouldn't say it's impossible, but it will be the civil engineering equivalent of replacing a jet engine in midair.

That's surely foolhardy to even suggest that's possible to do that safely within such tight timescales. A detailed study must need to take place on the state of the rest of the structure; and I can't believe, given the age of it, that any solution to just bridge the missing bit would be value for money...

[J N Winkler]

That's surely foolhardy to even suggest that's possible to do that safely within such tight timescales. A detailed study must need to take place on the state of the rest of the structure; and I can't believe, given the age of it, that any solution to just bridge the missing bit would be value for money...

I frankly doubt this segment of the A10 will be open in five months. What I would do, if I were the Autostrade CEO and had dictatorial control over the company's operations, is to recognize that the bridge has been an enormous maintenance liability from day one, and try to get a complement of long-term local and long-distance detours in place so I could demolish the entire thing and build a low-maintenance replacement with upgraded geometrics.

[KeithW]

This is possibly tin-foil hat territory, but there is now a large diagonal crack in the base of at least one of the 4 bridge deck legs in that picture.

We know that each pier was already supporting a couple of hundred tonnes of extra concrete crash barriers that were not part of the original design. Then, if there was talk of foundation work/issues on pier 9, could ground movement and/or a shearing failure in one or more of that pier's eastern deck support legs, thus making the whole thing tilt/twist enough to cause sudden progressive failure of the whole pier and deck structure?

Hope this pic makes sense...

The aspect of the photos of the collapsed tower base that concerned me was that I didn't see the amount of of reinforcing bars between the foundation and the tower itself that I would normally expect. This rebar is crucial when it comes to resisting anything other than compressive forces. Given the impact of the falling bridge I would expect to see cracks. What is needed is a forensic examination of the failure to find the origin of the collapse. Waht we can see now is just the result.

[c2R]

That's surely foolhardy to even suggest that's possible to do that safely within such tight timescales. A detailed study must need to take place on the state of the rest of the structure; and I can't believe, given the age of it, that any solution to just bridge the missing bit would be value for money...

I frankly doubt this segment of the A10 will be open in five months. What I would do, if I were the Autostrade CEO and had dictatorial control over the company's operations, is to recognize that the bridge has been an enormous maintenance liability from day one, and try to get a complement of long-term local and long-distance detours in place so I could demolish the entire thing and build a low-maintenance replacement with upgraded geometrics.

yes, I completely agree.

[roadtester]

I think they will also, at the very least, have to replace the whole thing.

Any solution that involves just fixing the bit that's fallen down, while somehow incorporating the sections of similar design that are still intact, probably just won't fly from a public confidence point of view, even if the surviving old bits pass the most rigorous of technical inspections.

I'm not sure the auguries for a quick effective solution are very good, given that Italy has a juvenile populist blame-everybody-else government without any money, rather than one determined to take responsibility.

[murphaph]

Bypassing the affected section would appear out of the question, given the mountainous terrain extending well to the north of the city. All the major roads in the area are a series of tunnels and bridges. Hardly anything at grade.

The only option would appear to be a replacement of the existing bridge. I also think that politically it will be impossible to propose just replacing the collapsed span. The entire cable stayed part at least will have to be replaced or there will be uproar I suspect.

One would hope the girder sections are ok though and would not need replacing, they are effectively different structures.

[Mark Hewitt]

I think they will also, at the very least, have to replace the whole thing.

Any solution that involves just fixing the bit that's fallen down, while somehow incorporating the sections of similar design that are still intact, probably just won't fly from a public confidence point of view, even if the surviving old bits pass the most rigorous of technical inspections.

I'm not sure the auguries for a quick effective solution are very good, given that Italy has a juvenile populist blame-everybody-else government without any money, rather than one determined to take responsibility.

Yes, just replacing the collapsed section would seem stupid. As you say if only from a public confidence point of view of driving over sections which are exactly the same in construction as the one that collapsed.

They should take the opportunity (seems a terrible word!) to remove the entire thing and rebuild it from scratch with modern materials and techniques. We don't yet know the fundamental cause but surely this make do and patch approach is going to be part of the issue.

It will probably take years to get a brand new bridge designed and built, yup, but that's what it takes!

[roadtester]

It will also be an interesting test of how easy it is to dismantle these vast pieces of infrastructure. I'm sure little weight was attached to this aspect when they went up - IIRC we had some discussion of this in connection with the old Forth crossing.

It's not an easy location for dismantling/demolishing what's left and disposing of it (he says as a layman rather than as an expert in dismantling Italian motorway bridges!).

[AAndy]

One of the dashcam videos shown on BBC showed the tower collapsing, very unevenly, and taking the roadway with it.

I've only seen the blurry phone footage taken from afar which shows the A-frame towers falling over and the even blurrier traffic cam at the tunnel entrance on the western side of the valley.

[Edited to remove tin-foil hattery]

Footage was shown starting before the collapse which shows a bright flash before and another during. I havn't seen this footage on uk tv or youtube since.

[Mark Hewitt]

https://amp.theguardian.com/world/2018/ ... ssion=true

The state of Europe's road network doesn't make for comfortable reading.

[Ruperts Trooper]

It will also be an interesting test of how easy it is to dismantle these vast pieces of infrastructure. I'm sure little weight was attached to this aspect when they went up - IIRC we had some discussion of this in connection with the old Forth crossing.

It's not an easy location for dismantling/demolishing what's left and disposing of it.

A number of structures have cables under tension that are gradually tightened as the erection progresses and more weight is added to the structure - the 1960's BBC Television Centre was built like that and it makes demolition difficult.

[Mark Hewitt]

It will also be an interesting test of how easy it is to dismantle these vast pieces of infrastructure. I'm sure little weight was attached to this aspect when they went up - IIRC we had some discussion of this in connection with the old Forth crossing.

It's not an easy location for dismantling/demolishing what's left and disposing of it.

A number of structures have cables under tension that are gradually tightened as the erection progresses and more weight is added to the structure - the 1960's BBC Television Centre was built like that and it makes demolition difficult.

The Genoa bridge could hardly be in a worse location both when it comes to taking down the old bridge and putting up the new one. See here
https://goo.gl/maps/bZZWYzTqZS82

I wonder to what extent the buildings have been built up under the bridge in the last 50 years, did it cross such a densly populated area when it was built? If the bridge was to be replaced in situ is would make living near the construction difficult or impossible

[rhyds]

https://amp.theguardian.com/world/2018/ ... ssion=true

The state of Europe's road network doesn't make for comfortable reading.

Part of the problem has been (in the UK at least) a constant squeeze of transport budgets, especially on the maintenance side. Transport spending has mostly been shiny new projects or publicity friendly cycle/rail infrastructure. Saying you're going to spend £1bn on roadworks will only get you "YEARS OF MISERY FOR MOTORISTS" headlines in the red tops.

[Bryn666]

It will also be an interesting test of how easy it is to dismantle these vast pieces of infrastructure. I'm sure little weight was attached to this aspect when they went up - IIRC we had some discussion of this in connection with the old Forth crossing.

It's not an easy location for dismantling/demolishing what's left and disposing of it.

A number of structures have cables under tension that are gradually tightened as the erection progresses and more weight is added to the structure - the 1960's BBC Television Centre was built like that and it makes demolition difficult.

The Genoa bridge could hardly be in a worse location both when it comes to taking down the old bridge and putting up the new one. See here
https://goo.gl/maps/bZZWYzTqZS82

I wonder to what extent the buildings have been built up under the bridge in the last 50 years, did it cross such a densly populated area when it was built? If the bridge was to be replaced in situ is would make living near the construction difficult or impossible

The failure has happened and broken cleanly at an expansion joint - as I said upthread, I don't think (but I'm not a structures expert) the conventional viaduct to the west of the collapsed span is in need of replacement - strengthening perhaps, replacement no. This is standard box girder viaduct and is for all intents and purposes a standalone structure.

The surviving cable stay spans will need to be removed for at least political reasons (although I would expect the loss of 33% of that element has not helped structural stability at all). Given there are buildings underneath the centre span, removal of that tower should prove fun.

Perhaps a single tall tower in the central position, allowing a larger single cable stayed span is the only real workable option unless you want to take away houses. The rail yards make conventional small spans difficult.

[WHBM]

I frankly doubt this segment of the A10 will be open in five months.

I, too, wondered where this assessment came from. It seems similar to the rebuilding of the Newhall interchange in Southern California which had multiple collapses in the 1994 Northridge earthquake, where the sections again fell at the expansion joints. Demolition and rebuild was indeed achieved there in 5 months. I think Turner Construction and C C Myers were the two contractors. The latter did a further series of collapse rebuilds at the same time, estimated at 5 months, in just 2 months.
https://en.wikipedia.org/wiki/Newhall_P ... 4_collapse

https://en.wikipedia.org/wiki/C._C._Myers#History

[roadtester]

I suspect another complication is that any new structure is also probably going to need to be an upgrade rather than just a 1:1 replacement (D2M to D3M?) - with all of the follow-on implications that might have for the rest of the route.