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
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1
- #102
video simulation of the bridge collapse
Interesting simulations, but none accounted for the rotation of the one large portion of the bridge. I expect getting the connectivity between the sections and the strength of the sections just right is a problem. Still, they did show gross behaviors that were also found in the actual collapse indicating that overloading the bridge or having a cable fail is not a good thing.
LittleInch
Petroleum
Don't forget there was a howling gale at the time which might not be easy to simulate.
Cable failure looks like the best bet so far. Has there been any more information released?
Remember - More details = better answers
Also: If you get a response it's polite to respond to it.
Cable failure looks like the best bet so far. Has there been any more information released?
Remember - More details = better answers
Also: If you get a response it's polite to respond to it.
(in Italian)
The attached in English (but different)
and one more on maintenance done on stays
The attached in English (but different)
and one more on maintenance done on stays
A howling gale isn't going to flip that much concrete without flipping all the concrete. It wasn't enough to blow the truck from the bridge or deflect any vehicles. I think the model overestimated the torsional strength of the bridge deck and underestimated the bending strength of the tower members.
The article provided by robyengIT is very interesting, but also presents a little confusion in understanding the principles of the Morandi's design.
The bridge is an early version of a cable-stayed structure, with unique concrete cable protection system, also serving as added component of stays, carrying part of the live and dead load and reducing vibrations and deflection.
So, the A cables were original stays, stressed by the cantilever's DL and later, by the center span DL and LL on both cantilever and center spans. These were not subject to any stress relaxation, to the contrary - any extra sagging of the cantilever was the sign of deterioration/degradation of the stays, increased stresses in the tendons, and resulting elongation of the stays. The B cables were likely extended beyond the anchorage of the A cables, to be fully effective in participation of carrying the loads. Detailed drawings of the anchorage zones will be very helpful.
The stressing of the concrete encasement was only serving as protective anti-crack countermeasure, and reported "relaxation" was the sign of elongation of the A and B strands due to corrosion section loss, cracking (hydrogen induced stress cracking) and/or combination of both.
The bridge is an early version of a cable-stayed structure, with unique concrete cable protection system, also serving as added component of stays, carrying part of the live and dead load and reducing vibrations and deflection.
So, the A cables were original stays, stressed by the cantilever's DL and later, by the center span DL and LL on both cantilever and center spans. These were not subject to any stress relaxation, to the contrary - any extra sagging of the cantilever was the sign of deterioration/degradation of the stays, increased stresses in the tendons, and resulting elongation of the stays. The B cables were likely extended beyond the anchorage of the A cables, to be fully effective in participation of carrying the loads. Detailed drawings of the anchorage zones will be very helpful.
The stressing of the concrete encasement was only serving as protective anti-crack countermeasure, and reported "relaxation" was the sign of elongation of the A and B strands due to corrosion section loss, cracking (hydrogen induced stress cracking) and/or combination of both.
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- #108
hpaircraft
Member
robyengIT said:
Wow, the level of detail in the diagrams is pretty amazing.
Kind of a hijack, but one of the things that impresses me about the design is the use of diagonally-oriented rebar to increase the shear capacity in the area where the support struts react concentrated loads into the viaduct sections. I think if Denney Pate had seen these diagrams a year ago, we might have a lot less traffic here in the failures & disasters forum.
Another thing that struck me about the photos in the article is that this bridge appears to embody at least some of the principles of accelerated bridge construction. They show construction going on over the tops of buildings and across a busy rail yard.
the prestressing patented system M5 (manual for designers)
For people who do not speak italian/spanish : detailed info (drwgs too) can be found in "Construction and design of cable-stayed bridges - ed 1976 or ed 1986". Book of "Wiley series of practical constructions guides" (Maracaibo - Venezuela bridge , very similar to Genova one)
from the BBC,
Italian prosecutors are investigating 20 people on suspicion of involuntary manslaughter in connection with the motorway bridge collapse in Genoa last month.
They include managers at Autostrade, the company which managed the bridge.
Link:
Dik
Italian prosecutors are investigating 20 people on suspicion of involuntary manslaughter in connection with the motorway bridge collapse in Genoa last month.
They include managers at Autostrade, the company which managed the bridge.
Link:
Dik
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- #114
Here's a simulation by the NYT, supposedly based on not-yet-released video:
Different in many ways than the YouTube videos posted above - they have both southern stays breaking simultaneously, and a more clear distinction in time between the falling of the roadway and the collapse of the tower. That seems more consistent with the security video that has been released.
Different in many ways than the YouTube videos posted above - they have both southern stays breaking simultaneously, and a more clear distinction in time between the falling of the roadway and the collapse of the tower. That seems more consistent with the security video that has been released.
- Moderator
- #118
Thanks, Jasm.[ ] That is a very well presented and well supported article.
I am not a bridge engineer (although through my career I did work on some aspects of a few bridges that were much smaller and simpler than this one).[ ] From my inexperienced perspective I have a problem with it.[ ] The article says that the pair of southern stays broke simultaneously.[ ] Surely that is highly unlikely to happen to a pair of independent structural elements.[ ] If the NYT's "simulation" is correct with regard to the fact that these stays broke in or near their middles rather than at their tops (and that should have been fairly easy to ascertain from examination of the post-collapse pile of rubble), what was the mechanism by which the break in the one stay caused a nearly instantaneous corresponding break to occur in the other?[ ] The first break would tend to lessen the amount of force in the second stay, not increase it.
I am not a bridge engineer (although through my career I did work on some aspects of a few bridges that were much smaller and simpler than this one).[ ] From my inexperienced perspective I have a problem with it.[ ] The article says that the pair of southern stays broke simultaneously.[ ] Surely that is highly unlikely to happen to a pair of independent structural elements.[ ] If the NYT's "simulation" is correct with regard to the fact that these stays broke in or near their middles rather than at their tops (and that should have been fairly easy to ascertain from examination of the post-collapse pile of rubble), what was the mechanism by which the break in the one stay caused a nearly instantaneous corresponding break to occur in the other?[ ] The first break would tend to lessen the amount of force in the second stay, not increase it.
LittleInch
Petroleum
I have my doubts about this also. I'm not sure that the designers of the video / slideshow, realize that the pier structure is actually two separate structures as far as I can tell. You have the two A frames which are held together with two concrete beams at the top and under, but not supporting, the road way. These then have the suspension stays at the top.
The second structure within the footing of the A frames is a Y shaped support which actually holds up the deck in two locations centred on the A frame. See the pictures below.
Thus when the slide show shows the bridge deck rotating, it would impact the horizontal support tieing the two A frames together which would probably start a collapse of the A frames.
One failure of a stay could quite quickly lead to a second failure, but unless they both broke at the top, it seems unlikely they broke at exactly the same time.
It would be interesting to see this apparently unreleased security video though.
Remember - More details = better answers
Also: If you get a response it's polite to respond to it.
The second structure within the footing of the A frames is a Y shaped support which actually holds up the deck in two locations centred on the A frame. See the pictures below.
Thus when the slide show shows the bridge deck rotating, it would impact the horizontal support tieing the two A frames together which would probably start a collapse of the A frames.
One failure of a stay could quite quickly lead to a second failure, but unless they both broke at the top, it seems unlikely they broke at exactly the same time.
It would be interesting to see this apparently unreleased security video though.
Remember - More details = better answers
Also: If you get a response it's polite to respond to it.
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