Florida university bridge collapses leaving several fatalities

konfab

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#21
I have an idea of what went wrong here.
If you look at the bridge's completed design, you will see it is a suspension bridge.
https://news.fiu.edu/wp-content/uploads/17703_EXT_FIU_Bridge_Move_Fact_Sheet_030918_DIGITA L.pdf

Given this is a pedestrian bridge, the main load on the bridge is its dead load (meaning the weight of the bridge itself). This means that the suspension part of the bridge is most likely required for the structure to remain standing.

If you see the way that other suspension bridges are built, they always build the supporting structures first.
new-construction-of-a-suspension-bridge-across-the-mekong-river-vietnam-B0H8KP.jpg

Youtube video on this:
[video=youtube;ioC61QW7SHQ]https://www.youtube.com/watch?v=ioC61QW7SHQ[/video]
 
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Gordon_R

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#22
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buka001

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#23
LOL, I've been watching AvE's video this morning. My comments on this forum yesterday align with his conclusions...

Edit: Important bits. The pre-tensioning cables: https://youtu.be/ioC61QW7SHQ?t=180
Only half the bridge that failed: https://youtu.be/ioC61QW7SHQ?t=425
Domino theory of multiple failures: https://youtu.be/ioC61QW7SHQ?t=590
Pretty much agreed as well.

I am still not sure on what exactly triggered it, but I pretty much agree with the video in as much as it looks like it simply slid off the bearings. So could be excess deflection from the tensile stresses, which were unrestrained by the absence of the cable stays, caused some sliding, in the direction of the undamaged section.

Insufficient temporary works to either restrict any lateral movement, or provide some mid-span support led to the failure. This should have been identified by the contractor, as it appears it was their choice to fast-track the construction this way, they should have checked with the designer what the deflection would be and any resultant movement of the deck in its temporary state.

EDIT - Just saw this now - https://www.theguardian.com/us-news...d-in-bridge-collapse-at-florida-college-video

I presumed the crushing happened when the deck hit the road, but from the CCTV footage it happened in the air. I think a Pre-tension cable or two snapped.
 
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Gordon_R

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#24
AvE has crowdsourced a definitive failure analysis (he even simulates the failure curve in his workshop): https://www.youtube.com/watch?v=KtiTm2dKLgU

Dashcam footage shows the break is instantaneous on the one side (where the rod came out), not in the middle: https://www.youtube.com/watch?v=KtiTm2dKLgU&t=110

A post-tensioning rod failed after installation, shown in post collapse photos: https://www.youtube.com/watch?v=KtiTm2dKLgU&t=691

During transport details were changed (load spreaders and position of 4th crawler), without allowing for full structural analysis: https://www.youtube.com/watch?v=KtiTm2dKLgU&t=820

The rod deformed and weakened, and they tried to tighten it: https://www.youtube.com/watch?v=KtiTm2dKLgU&t=891

They knew there was a problem, and were trying to fix the bridge while traffic was still flowing...
 

ForceFate

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#26
AvE has crowdsourced a definitive failure analysis (he even simulates the failure curve in his workshop): https://www.youtube.com/watch?v=KtiTm2dKLgU

Dashcam footage shows the break is instantaneous on the one side (where the rod came out), not in the middle: https://www.youtube.com/watch?v=KtiTm2dKLgU&t=110

A post-tensioning rod failed after installation, shown in post collapse photos: https://www.youtube.com/watch?v=KtiTm2dKLgU&t=691

During transport details were changed (load spreaders and position of 4th crawler), without allowing for full structural analysis: https://www.youtube.com/watch?v=KtiTm2dKLgU&t=820

The rod deformed and weakened, and they tried to tighten it: https://www.youtube.com/watch?v=KtiTm2dKLgU&t=891

They knew there was a problem, and were trying to fix the bridge while traffic was still flowing...
Unsettling.
 

genetic

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#27
If this happened in SA, the MyBB brigade would be crying BEE, ANC, Zupta blah blah blah...

Sometimes engineering just goes wrong.
 

buka001

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#28
AvE has crowdsourced a definitive failure analysis (he even simulates the failure curve in his workshop): https://www.youtube.com/watch?v=KtiTm2dKLgU

Dashcam footage shows the break is instantaneous on the one side (where the rod came out), not in the middle: https://www.youtube.com/watch?v=KtiTm2dKLgU&t=110

A post-tensioning rod failed after installation, shown in post collapse photos: https://www.youtube.com/watch?v=KtiTm2dKLgU&t=691

During transport details were changed (load spreaders and position of 4th crawler), without allowing for full structural analysis: https://www.youtube.com/watch?v=KtiTm2dKLgU&t=820

The rod deformed and weakened, and they tried to tighten it: https://www.youtube.com/watch?v=KtiTm2dKLgU&t=891

They knew there was a problem, and were trying to fix the bridge while traffic was still flowing...
Yeah see the edit in my post previously, as soon as I saw the cctv footage of the collapse I knew it had to be a failure of the pt cable.
 

Gordon_R

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#30
Yeah see the edit in my post previously, as soon as I saw the cctv footage of the collapse I knew it had to be a failure of the pt cable.
The exact stresses that the post-tensioning rod were exposed to during transportation, still need to be analysed in detail. That could take a while, but clearly the company knew there was a problem...

IMO the fully assembled bridge would have provided additional support from the center column cables.

As earlier suggested, there was a chain of failure/oversight/implementation for this disaster to happen.

FYI, the inquiry into the Grayston Drive footbridge collapse is still ongoing: https://www.news24.com/SouthAfrica/...on-bridge-collapse-inquiry-announced-20180309
 

supersunbird

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#31

thechamp

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#38
If this happened in SA, the MyBB brigade would be crying BEE, ANC, Zupta blah blah blah...

Sometimes engineering just goes wrong.
Lol

It doesn't come as a surprise anymore...
moan about certain people making every thread a TIA thread - does the exact same in a US bridge collapse thread

:rolleyes:
You're one of the first TIA'ers in every thread... Go figure.
shem, hypocrites on defense
Come on you guys, i am sure that if we look hard enough we can find an AA person to blame here, no need for all this bickering.
 

ForceFate

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#39
shem, hypocrites on defense
Your previous post doesn't make sense tbh. Ditch your prejudices and be rational for a minute then read it again. There's honour in accepting a mistake and apologising.

Now, let's not spoil a good discussion with garbage.

Back OT...
 
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