An interesting theory from the article: "Italian news agency ANSA said authorities suspected that a structural weakness caused the collapse".
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Bridge Collapse in Genoa, Italy 26
- Thread starter thebard3
- Start date
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 * 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.
* 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 * 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.
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.
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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.
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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.
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LittleInch
Petroleum
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
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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.
Guest
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."
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."
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
“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
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.
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Guest
waross said:
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."
- Thread starter
- #132
This video popped up on my YouTube today. Non-technical, but interesting none the less:
Alistair_Heaton
Mechanical
BrianPetersen
Mechanical
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.
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
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
secret till this morning : the actual failure sequence
12345abc6ttyui67
Structural
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.
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
Petroleum
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.
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.
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