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.

 

[SFCharlie]

My heart and prayers go out to the victims.
This is the third deadly collapse in which maintenance on a bridge, open to traffic was a factor: twin cites interstate, FIU pedestrian, and this. The video shows one of the tower structures collapsing after the roadway. I haven't been able to see how many of the non-cable stayed segments of the viaduct collapsed (edit: apparently none.).

 

[BridgeSmith]

"From the photo posted by bimr above, the two cable-stay assemblies are still standing."

Two of them are, but there were 3 stayed spans (see the Google streetviews posted by cooperDBM).

I think you're on the right track, though, because the video appears to show the tower collapsing (or being pulled down) after the deck had already come down.

 

[thebard3]

From BBC website--
Expert warned of bridge problems in 2016
A structural engineer who lectures at Genoa University, Antonio Brencich, warned back in 2016 that there were problems with the bridge, Italian media report. It was inaugurated in 1967.

"Right away the bridge manifested various problems, beyond the construction costs, which went over budget," he wrote in 2016.

"There are errors in this bridge. Sooner or later it will have to be replaced. I don't know when," he warned.

The Italian site ingegneri.info quotes his warning in full.

In the 1990s some major repairs were done to the bridge.

Mr Brencich said the designer, Riccardo Morandi, had miscalculated the "viscous deformation" - an ageing effect on reinforced concrete. "He was an engineer with great insight but lacking in practical calculations."

The link is Italian language for anyone who can read it--

http://www.ingegneri.info/news/infr...onte-morandi-genova-analisi-infrastrutturale/

Brad Waybright

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

 

[JAE]

thebard3 and HotRod10 - yes you are correct - I should have looked closer at the photos.

Check out Eng-Tips Forum's Policies here:
faq731-376

 

[JAE]

"viscous deformation" is apparently the same concept as concrete creep?

Check out Eng-Tips Forum's Policies here:
faq731-376

 

[chris snyder]

thebard3: "The link is Italian language for anyone who can read it"
Attached is translation

It may explain why the cables are flanked on the "concrete stays" of the NW tower. A different article said concrete stays are a unique feature, but I don't understand the point of doing it (so the cables would be stretched? to stop them from rusting?). Seems the concrete would just add a lot of weight.

Has anyone heard what was done for "restructuring" in 2016?

 

[thebard3]

JAE's pictures from the bottom side of the bridge and others show what look like patches or some type of laminate covering parts of the concrete. Can one of the structural guys make sense of these?

Brad Waybright

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

 

[3DDave]

I think they are patches to trap spalling concrete and keep it from killing or injuring people beneath the bridge. Similar structures with larger weave is used along some steep rocky highways to catch rocks from rolling onto the road.

 

[SFCharlie]

Ponte Morandi - Wikipedia
This is an article from the Italian Wikipedia.
When I view it in Chrome, Google offers to translate the page. If it doesn't, try right clicking on the page and look for "translate to English"

SF Charlie
Eng-Tips.com Forum Policies

 

[3DDave]

An interesting collection of photos:

http://www.retrofutur.org/retrofutur/app/main?DOCID=1000111180&albumMode=1000111180

One photo shows a building with the cornice notched to provide clearance; maybe an inch or so.

I'm thinking the obvious happened and one of the stays failed - either in the stay or, more likely, at the upper attachment, causing the deck on that side to twist and fall, which then overloaded the other stay on that deck segment. Since the main span could not survive as a cantilever it fell, the unbalanced load cause the upward V to tilt and fail, dragging with it the other span. The finale was the stays on that side pulling the tower down. Because of the asymmetry of the initial failure the failure of the far side was also a bit asymmetric.

It's possible the stay was already compromised enough that a lightning strike was the last straw, though the additional wind load might also have done the trick. Or maybe a rust fragment finally grew a bit too large.

The stays for the spans over the inhabited/apartment areas had already been reinforced with bolt-on steel, and the failed section had it's upper stay ends reinforced with external steel plate. It's clear that someone thought that the stays had a high risk of failure.

 

[cooperDBM]

I'm still wondering if the pier was partly undermined by the floodway beside it - enough to cause a tilt and overstress. Seems there was a severe storm and judging from the video I posted earlier the floodway can fill up. Many bridge have come down that way. Some relief that the span over the apartment blocks didn't come down.

 

[BridgeSmith]

"I think they are patches to trap spalling concrete and keep it from killing or injuring people beneath the bridge."

The necessity of adding something to catch chunks of concrete that break off is never a good sign. It brings to mind the bumper sticker I've seen on a few old trucks that reads "Warning: Parts may fall off".

 

[3DDave]

Don't look at the underside of Missouri bridges. MoDOT and city street crews dump salt by the ton and it corrodes the steel mesh, punching chunks up to 2 foot in diameter and about 1 inch thick loose. I think the maintenance technique is to rap any place with rusticles and salt stalactites with a hammer until the area pops loose, but they still do drop randomly by themselves. However, this bridge deck is more than 100 feet high and the outcome isn't going to be a dented roof or broken windshield.

 

[BrianPetersen]

The Gardiner Expressway in Toronto has had a few chunks of concrete break off and fall on the roadway below over the years. It's nowhere near as high as the Genoa bridge.

 

[SFCharlie]

Useful before and after pics:
Dozens reported dead after a huge highway bridge collapse in Italy
Sinéad Baker , Business Insider US

Italy Bridge Collapse Leaves 26 Dead NYT

SF Charlie
Eng-Tips.com Forum Policies

 

[LittleInch]

In the absence of evidence or video of the actual collapse, I agree with 3DDave at this point and think the non redundant concrete & steel stays must be major suspect especially given the repairs undertaken on part so them before. The split in the stays before they attach to the deck look interesting.

However any tilt of the tower could detach one of the connecting slabs and then it all gets very unbalanced.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[IFRs]

From

https://en.wikipedia.org/wiki/Creep_and_shrinkage_of_concrete

Creep and shrinkage can cause a major loss of prestress. Underestimation of multi-decade creep has caused excessive deflections, often with cracking, in many of large-span prestressed segmentally erected box girder bridges (over 60 cases documented). Creep may cause excessive stress and cracking in cable-stayed or arch bridges, and roof shells. Nonuniformity of creep and shrinkage, caused by differences in the histories of pore humidity and temperature, age and concrete type in various parts of a structures may lead to cracking. So may interactions with masonry or with steel parts, as in cable-stayed bridges and composite steel-concrete girders. Differences in column shortenings are of particular concern for very tall buildings. In slender structures, creep may cause collapse due to long-time instability.

 

[thebard3]

Here's an interesting article that highlights corruption in the EU (surprise, that). There's a link to a report detailing how it negatively affects inspections of infrastructure projects. European officials are always looking to prosecute someone, but I'm sure we'll find they miss the real target. It's interesting reading, whether or not you think it's necessarily germane.

https://www.nbcnews.com/news/world/...arks-finger-pointing-death-toll-rises-n900831

Brad Waybright

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

 

[epoxybot]

I can't find any photos suggesting any additional external reinforcing to saddle region of the Western tower that collapsed. Certainly none in the Google Streetview of 2017.

 

[hpaircraft]

Just a couple of observations based on the street view posted by DBMcooper:

https://www.google.com/maps/@44.424...=203&h=100&yaw=210.97716&pitch=0&thumbfov=100

https://www.google.com/maps/@44.424...4!1sQAt4gEhLxx56y0JyO810Bg!2e0!7i13312!8i6656

* The most eastern tower stays have been girdled and surrounded by cables that appear to have enough material to entirely replace the original stays.

* The middle tower stays have supplemental steel girdles at their upper ends, possibly to reinforce their attachments to the tower.

* The western tower and stays, which were involved in the collapse, appear to have none of the reinforcements applied at the middle or eastern towers.

Not that that means a lot, but it does suggest some possibilities:

* The reinforcements applied at the other towers worked, making the unreinforced tower the weakest link.

* Officials underestimated the deterioration of the western tower and stays, and so failed to apply any of the reinforcements to it.

Of course, it is quite possible that other factors such as instability at the tower foundation dominated the collapse, and that the reinforcements were irrelevant.

One other thing, the lightning strike shown in the one video of the collapse appears to have occurred after the collapse was well underway and the eastern portions of the western span had already fallen. However, it might be worth considering that an earlier strike (lightning often does strike twice!), not captured on video, might have sent enough amperage down the cables to put them over the edge. I don't think it's likely, but it's among myriad things that will have to be considered.