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.

 

[jasm]

It sounds like the NYT reconstruction is based on an unreleased video. There was some security video already released though that doesn't seem to match the YouTube simulation above
* This analysis of security video that was posted by mdepablo on 21 Aug. seems to show the roadway falling well before the tower base cracks

http://www.retrofutur.org/retrofutur/app/main?DOCID=1000116032

* The dashcam or phone video by a distant driver at the start of this also shows the delay. The roadway has already fallen and the driver is already shouting when the video starts. Then, the tower falls.

https://www.youtube.com/watch?v=_Pl0rsVdXxM

 

[prex]

As you can see on page 10 of the document posted above by robyengIT (31 Aug), the tendons are continuous over the top of the A frames, so breakage on one side, especially if near the top, where corrosion was likely deeper, implies immediate detachment of the other top end.

prex
[URL unfurl="true"]http://www.xcalcs.com[/url] : Online engineering calculations
[URL unfurl="true"]https://www.megamag.it[/url] : Magnetic brakes and launchers for fun rides
[URL unfurl="true"]https://www.levitans.com[/url] : Air bearing pads

 

[Denial]

Thanks, Prex.[ ] That would explain it.[ ] I was misled by the animation showing that both stays broke near their middles.

 

[prex]

In the youtube video reposted above by jasm you can see:
1) one side of the A frame (the one farther from the oserver?), falls first with at least one stay still attached; it is likely taken down by the stay itself
2) the opposing side (the one closer to the observer?), still upright when the other one is falling down, falls down immediately after, but it has no stay attached
So it would appear that the closer side loses both stays first, then the farther side is taken down by its stays, then the closer side falls down.
The closer side in the video, however, is the nothern one, this would indicate that the stays that initiated the collapse were the northern ones, contrary to what is assumed in the beautiful article of the NYT posted by jasm.
However the distinction between farther and closer side in the video is unclear, due to the blurred view, so the NYT might be correct. Observation of how the rubble of the A frames is scattered on the ground can easily resolve the issue.

prex
[URL unfurl="true"]http://www.xcalcs.com[/url] : Online engineering calculations
[URL unfurl="true"]https://www.megamag.it[/url] : Magnetic brakes and launchers for fun rides
[URL unfurl="true"]https://www.levitans.com[/url] : Air bearing pads

 

[LittleInch]

Hmmmm,

Had missed that drawing. I think any break anywhere in the top half of the stay above the split would be enough.

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

 

LittleInch,
Thanks for posting the pictures.
I am no designer, but this design scheme doesn't pass the basic sanity test for me.
What I do know is that I would immediately ban reinforced concrete for highway structures here in Canada. Road salt is a concrete-killer, and the structures are virtually uninspectable.

"Everyone is entitled to their own opinions, but they are not entitled to their own facts."

 

[bimr]

There has to be more video. Supposedly there were CCTV cameras on the bridge.

“I have heard that video footage from the CCTV cameras on the bridge just before the collapse showed concrete being exploded off the main stay because of the violence of some of the cables snapping underneath,” one source said.

Link

 

[prex]

ironic, what you state is today a fact, but the bridge dates back in the sixties, when prestressed concrete was beloved and believed, by enthusiastic designers, to be light, elegant, and as durable as rock.

prex
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[URL unfurl="true"]https://www.megamag.it[/url] : Magnetic brakes and launchers for fun rides
[URL unfurl="true"]https://www.levitans.com[/url] : Air bearing pads

 

prex,
True, but I think I would have considered it ugly both then and now.

"Everyone is entitled to their own opinions, but they are not entitled to their own facts."

 

[waross]

Ironic;
I haven't been in TO for a long time. How is the Gardiner holding up?

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

 

How is the Gardiner holding up?

With bandaids manufactured from dollar bills.
'
I haven't been to TO for a long time, do not plan to visit TO for a long time, and hope not to travel to TO for a very long time. I hope I've made my feelings clear!

"Everyone is entitled to their own opinions, but they are not entitled to their own facts."

 

[thebard3]

How is the Gardiner holding up?

Hey, I live in Ohio, so when I say that Gardiner expressway is pretty ugly, you can be assured I know what I'm talking about. It would fit right in any city here.

Brad Waybright

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

 

[JStephen]

This video popped up on my YouTube today. Non-technical, but interesting none the less:

https://www.youtube.com/watch?v=OIOgy4QuB74

 

[Alistair_Heaton]

And its been demolished.

https://www.bbc.com/news/world-europe-48790056

 

[JAE]

I thought there were occupied buildings underneath?

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

 

[BrianPetersen]

Evidently the parts of the bridge that were over other buildings had been taken down separately over the past few months. Tricky job, for sure.

 

[robyengIT]

1 - buildings underneath : empty. People have been evacuated immediately after the disaster (august 2018). New houses under construction somewhere else.
2 - part of the bridge between pylons (piers) : cut with diamond saw and landed by cranes
3 - people still living in vicinity (approx 300 meters from bridge) evacuated this morning at 6.00 am till this afternoon
4 - demolition powder reduced to minimum because on the deck were installed a lot of prefab flumes filled with water. Furthermore, immediately after demolition, many firefighters with hydrants

 

[robyengIT]

secret till this morning : the actual failure sequence

http://tg.la7.it/cronaca/esclusivo-...e-morandi-il-14-agosto-2018-30-06-2019-140192

 

[12345abc6ttyui67]

Link

Considering the detailed nature of the video, again sympathies go to the victims and families affected.

Thoughts on the technical aspects of the new video?

Both right hand stays appear to go slack, and the deck drops, slightly before the main tower fractures.

1 - Cable snaps in one or other of the right hand stays (perhaps closest, hard to say?)
2 - Resulting out-of-balance cable tension makes the tower 'spring' towards the intact stay (possibly furthest?), making it appear to go slack.
3 - With no tension, both decks drop.
4 - Take up of slack, and shock load, on whichever stay was intact (furthest?), applies out of balance tension on top of tower, fracturing it.

 

[LittleInch]

Like the Miami bridge collapse, it's all happening so fast with only a slow frame rate you can't really work out what happens first, but if the cables snapped as has been put forward you would expect them to be seen to separate, but they stay connected.

Did the tower snap first?

Or the cross beam holding the two towers together?

Given the right hand cable bends in the middle it implies loss of the structure at the top first, but so difficult to see.



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