Bridge Collapse in Genoa, Italy 26

[thebard3]

https://www.cbsnews.com/news/italy-...noa-traps-cars-under-rubble-today-2018-08-14/

An interesting theory from the article: "Italian news agency ANSA said authorities suspected that a structural weakness caused the collapse".

Brad Waybright

It's all okay as long as it's okay.

 

[3DDave]

Good links - there is spall capture material applied at the top of the stays at the western tower. Perhaps there was cracking leading to water infiltration leading to excessive corrosion of the internal cables.

 

[SFCharlie]

The mystery of the maxi-contract to reinforce the tie rods and the work postponed until after the summer
Again, I needed to use Google Translate, "Right click" if Google chrome doesn't offer it automaticly


SF Charlie
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[SFCharlie]

I don't even know what part of the bridge structure I'm looking at, or if the rusty circle is a tube or solid, but I have seen it in more than one video and at lease once in sunlight so I'm sure it's very rusty...

A screen capture from this video:
Dozens killed in motorway bridge collapse in Genoa, Italy


SF Charlie
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[mbullism]

https://www.nytimes.com/video/world...rticle&region=Footer&contentCollection=Europe

Analog spoken here...

 

[chris snyder]

This article talks about corruption in construction (almost halfway down). Has a lot of photos.. updated today with a lot of victims.
"There were also concerns the Italian mafia could have contributed to the bridge's collapse by their construction companies being involved in maintenance work - including shoring up the foundations. 'Mafia-related companies are known to have infiltrated the cement and reconstruction industries over the decades and prosecutors have accused them of doing shoddy work that cannot withstand high stress,' Canada's Globe and Mail wrote."

http://www.dailymail.co.uk/news/art...s-35-people-killed-Genoa-bridge-collapse.html

Coincidentally, if nothing else, that the failed section had no reinforcement. SFCharlie's link about the 'maxi-contract' seems to address this (there were plans to do it after summer?)
Could be work at the top of next section saved that portion from falling on the apartments. I can imagine on balcony seeing that fall. The above article said it was reported two people died in their home.

 

[thebard3]

The more pictures and stories to come from this tragedy, the more I see that this bridge seems to be, uh, dilapidated. Repair and reinforcement work was started in the '90s and was never completed, and the section that fell seems to be the section that received the least of this repair and reinforcement work.

Brad Waybright

It's all okay as long as it's okay.

 

[bimr]

translated "I problemi dello “schema Morandi” e quel precedente del 1964"

Rome - After the tragedy that took place on the Morandi bridge in Genoa, Antonio Occhiuzzi, director of the Institute of Construction Technology of the National Research Council, recalled that the prefabricated reinforced stays made of other viaducts that are similar (like in Maracaibo, in Venezuela, but also in Basilicata), have shown a relatively reduced durability. And the stability of a bridge of this type depends fundamentally on the behavior and the condition of the stays.

In the case of the Genoa bridge, Occhiuzzi noted, some of the stays have been modified with clearly visible reinforcement, but the collapsed section was not modified. It is necessary to understand the background of the decision to reinforce some stays, but the same treatments have not been carried out on the other stays that are similar.

The previous collapse of other infrastructure:
Then Occhiuzzi recalled the previous failure of road infrastructures: "In July 2014 a spill of the Petrulla viaduct collapsed, on the state road 626 between Ravanusa and Licata (in the province of Agrigento), breaking in half due to the crisis of the pre-compression system; in October 2016 a flyover in Annone (Lecco) collapsed due to an exceptional load that was incompatible with the strength of the structure, which however was very aged compared to the original capacity; in March 2017 an overpass of the Adriatic motorway collapsed, but due to an accidental event during maintenance work; in April 2017 a span of the tangenziale di Fossano (Cuneo) collapsed, breaking in half in the absence of vehicles in transit and with methods very similar to those of the Petrulla viaduct".


The precedents of the "Morandi scheme":
A twin bridge of the one that collapsed in Genoa was constructed in Venezuela in 1964. This bridge was later was struck by an out-of-control tanker: That bridge was the General Rafael Urdaneta bridge over the 8.7-kilometer-long bay of Maracaibo, with 135 spans, of which there are 6 towers built with the same cable stayed scheme used by the designer Riccardo Morandi in Genoa.

It was April 1964 when the oil tanker Exxon Maracaibo, from 36 thousand tons, due to an electrical failure lost control at the exit from the Maracaibo lagoon and ended up against the 30 and 31 piers of the bridge, more than 600 meters away from the bays designed for the passage of naval traffic, with such violence that made them completely collapse, dragging into the sea 3 consecutive bays of the bridge. This type of event had not been taken into consideration during the design.

The expert: those bridges have always had deformation problems
Professor Andrea Del Grosso also spoke on the same issue, for years he was a professor of construction techniques at the University of Genoa, and today he teaches a course on Infrastructure Management and Monitoring: "Morandi has always had problems with corrosion on the stays and of excessive deformation, due to the loss of tension of the steel cables inside the prestressed concrete structures. But at the time of construction the deformations of the concrete were not known as today. We have been studying the problem of the degradation of these structures only for twenty years ".

Del Grosso added that the A10 bridge over the Polcevera River was very innovative at the time. A steel structure was more suitable for the project scope. However, at the time there were questions about steel, for reasons of duration, while Italian industries had great experience in reinforced concrete. But then the deformations of the concrete were not as known, at least not as known today; The bridge on the Polcevera River according to the teacher "was a critical structure, especially for the use of prestressed concrete

Link I problemi dello “schema Morandi” e quel precedente del 1964

 

[robyengIT]

I am an Italian engineer (mechanical) and I am not expert in prestressed concrete or bridge structures, but as far as I understand from several interviews, written reports of many professors at University (at least expert of the relevant theory) and from previous warning advices, it is more and more clear to me the following :
1 - the project and design were "deficient" in many aspects, i.e. possibility of failure of a cable (stays) and therefore collapse of a tower (too weak to resist to torsion and to bending moment of the remaining cable). Furthermore the increasing intensity of traffic (Genova is the biggest port in Italy)
2 - the cable were prestressed according to a patented system so called M5 invented by Mr. Morandi and used only by him (3 times luckily, but all 3 failed)
2 - a couple of cables was replaced in 1990
3 - the cables were coated with concrete (theoretically to prevent corrosion), so it was impossible to check for corrosion of the steel (possible and probable cause of the collapse)
4 - many people of the (private) highway company knews the problems. Theoretically the inspectors of the relevant Ministry could/should have checked because enforced by an agreement with the highway company
5 - a continous maintenance (heavy, hard and expensive) has been done since the beginning (1970)
6 - approx 10-12 years ago they were going to build a new structure side by side to the existing one but "no-global" people succeded in opposition
7 - people mentioned in above point 4 didn't do any alternative action. Same the Ministry inspectors
8 - in this case no mafia involved, but just (my opinion) negligence, lack of interest, indifference (blow-you-Jack attitude)
9- we will se the trial. As many other times : very late, no responsibles, all responsibles, ...
10 - just for curiosity : the highway company is ready to rebuild the bridge in 5 months (for me they don't do even the drawings of the project !!!)

 

[Vikko]

Antonio Brenchich, said in a video interview, the possible cause was the stress corrosion; due to high preload of the stay bolts (he said 1500-1600 MPa and also up to 1700 MPa (15-16 kkg/cm2 he said), (so high?) this means the bolts reach the yielding point for sure. Or maybe he meant only 150-160 MPa insyead (but that seems too low to me)?). The corrosion in preloaded bolts is accelerated so the ageing is faster. Then he said the rupture is brittle because of the bolt being under this high tension load (this seems strange to me, the steel shall not change its stress-deformation characteristic, just because it is under tension; maybe I did not understand and it is true for all the coupling of concrete under compression and steel bolt under tension togethere).
Here is the interview, at min. 2:14.

https://youtu.be/ehjQbIrIcds

 

[bones206]

Stress corrosion cracking (SCC) was a big concern at the nuclear plants I've worked at. I don't know much about it, but I always heard that term being floated around in meetings. Link Might be what Mr. Brenchich was referring to.

 

[epoxybot]

SFCharlie - The voids in the photos are in the columns of the towers. It looks as though they were made using cardboard void forms. The voids are to prevent the heat of cement hydration (exotherm) from causing subsequent stress in the mass concrete from shrinkage and other ill effects.

 

[thebard3]

epoxybot,
You're a structural guy. That doesn't look like much rebar in that tower, in fact I only see a layer just beneath the peripheral surface. I don't think that would make the grade today, would it?

Brad Waybright

It's all okay as long as it's okay.

 

[waross]

I have been wondering about the apparent skimpy re-bar also.
Referring to the picture posted by epoxybot, is it normal for a single layer of re-bar to be positioned that close to the surface?

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[SFCharlie]

Thank you epoxybot. Nice photo.

SF Charlie
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[epoxybot]

thebard3 - My knowledge of structures is from a manufacturer/supplier career in the Concrete Forming, Repair, Materials & Sub-Contracting side with a strong emphasis on structural repair - namely epoxy and other polymers. When I first registered many years ago I wasn't sure what category I should list. Last time I checked there isn't really an "Associate" category.

I don't disagree, that the column looks "Basic". My knowledge of Mass Concrete comes largely from reading the Bureau of Reclamation's "Concrete Manual". Certainly by today's standards this would be considered "Under Nourished".

What also stood out to my eye was the shape of cleavage plane. I would have expected more of a fractured surface. The photo I posted is suggestive of a cold joint region and the rather smooth, almost chalky break raises concerns of carbonation of the cement.

 

[RickyTickyTavi]

Cant comment on the amount of reinforcement, but concrete cover of steel reinforcement can vary between 1 and 3 inches. I dont know know Euro-codes of from the 1960's. But I would guess its in that range.

 

[chris snyder]

"Stays on the eastern span of the bridge had been remade, with huge costs," said Royer Carfagni, the Parma University lecturer, "But it was thought that the problem was not critical on the western span, which is the one that collapsed."

Does anyone know why the east span stays were rebuilt, or why the reinforcement metal was installed at the top of the center span stays?

 

[Vikko]

@chris snyder
The remade the concrete coating only of the stays, because it was corroded and aged, I suppose.

 

[thebard3]

Vikko,
My observations are that the stays at the east tower are completely different now from the original. Large steel reinforcements have been added to the top of the tower and additional cables surround the original stay (or stralli?). None of these modifications were made to the west tower that collapsed.

Brad Waybright

It's all okay as long as it's okay.

 

[Lomarandil]

We're professionals here, let's try to keep the speculation under control. As we saw in the FIU collapse, sometimes members of the public or press tend to wander in here and take the opinions offered as engineering fact.

As for the reinforcing, yes, it was and is common in piers of this size to have reinforcing only around the perimeter. After all, that is where the steel is most efficient.

A failure surface like the one shown above is an indicator of a sudden failure, rather than one that developed slowly over time (which would be rougher or more "fractured"). As such, it is most likely that the column failure was a result of some other issue, rather than the root cause.

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The name is a long story -- just call me Lo.