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What the hell is wrong in Florida? - The bridge collapse is puzzling on a number of levels
Posted on 3/16/18 at 6:12 am
Posted on 3/16/18 at 6:12 am
How can you be putting a horizontal bridge across a roadway, that has a center support as part of its design, without providing a center support during the process?
How can you have an active construction site with the public (without 'hardhats') buzzing around underneath the construction?
The latter was an immediate "WTF?" with me as soon as I heard of the collapse, and from just observing the sketches of the bridgeI wondered how it maintained its structural integrity without some sort of central support. Then I find out that the center support structure 'would be put in later' - with thousand of passenger cars whizzing underneath hourly>>>>????
W.T.F. >>>>???????
this just makes no sense to me at all. I am not a structural engineer, but it just seems to fly in the face of everything I do know.
How can you have an active construction site with the public (without 'hardhats') buzzing around underneath the construction?
The latter was an immediate "WTF?" with me as soon as I heard of the collapse, and from just observing the sketches of the bridgeI wondered how it maintained its structural integrity without some sort of central support. Then I find out that the center support structure 'would be put in later' - with thousand of passenger cars whizzing underneath hourly>>>>????
W.T.F. >>>>???????
this just makes no sense to me at all. I am not a structural engineer, but it just seems to fly in the face of everything I do know.
19
Posted on 3/16/18 at 6:14 am to ChineseBandit58
just a conspiracy to take david hogg and his beta friends out of the news cycle.
Posted on 3/16/18 at 6:14 am to ChineseBandit58
quote:
Florida
South FL ain't like the rest of FL but shite happens. Obviously it was a bad design.
quote:
I am not a structural engineer
Posted on 3/16/18 at 6:16 am to ChineseBandit58
One span went across the roadway, the other across the water. The supporting pier is on the grass.
Posted on 3/16/18 at 6:23 am to NYNolaguy1
quote:
One span went across the roadway, the other across the water. The supporting pier is on the grass.
OK - I have not seen that photo - only the part across the roadway. That looks perfectly functional as a finished installation.
Was any part of the suspension cabling in service? Or is that the 'cable tightening' operation that I heard mentioned as happening when the collapse occurred?
To have that span unsupported while allowing normal traffic flowing underneath just seems totally reckless to me.
Certainly those cables could not be there just to support the additional weight of the people walking on the bridge.
Posted on 3/16/18 at 6:38 am to ChineseBandit58
South Florida makes Louisiana government look like a JV corruption team
Posted on 3/16/18 at 6:40 am to ChineseBandit58
Sad situation.
Now of course it is a lawyer's bonanza.
Now of course it is a lawyer's bonanza.
Posted on 3/16/18 at 6:43 am to ChineseBandit58
quote:
Was any part of the suspension cabling in service? Or is that the 'cable tightening' operation that I heard mentioned as happening when the collapse occurred?
No, the cable tightening you heard about I suspect has more to do with the post tensioning inside the top chord of the bridge, not the suspension cables.
If they were messing with the post tension cables with active traffic underneath, it could be why it failed. Theres a lot of things that go wrong with precast post tension slabs though, and sudden failures can happen from a variety of reasons.
Posted on 3/16/18 at 6:58 am to ChineseBandit58
article with time lapse video of bridge install.
it was built next to the road than lifted into place.
watch bridge.l collapse here, warning it is a cnn link
it was built next to the road than lifted into place.
watch bridge.l collapse here, warning it is a cnn link
Posted on 3/16/18 at 6:59 am to NYNolaguy1
quote:
No, the cable tightening you heard about I suspect has more to do with the post tensioning inside the top chord of the bridge, not the suspension cables.
If they were messing with the post tension cables with active traffic underneath, it could be why it failed. Theres a lot of things that go wrong with precast post tension slabs though, and sudden failures can happen from a variety of reasons.
You seem to know quite a bit about this - thanks for the enlightement.
Question - was the overhead roof a substantial part of the structural integrity? i.e. could it have been part of looking at the span as a girder rather than just a flat slab? that is the only thing that makes sense to me.
Posted on 3/16/18 at 7:11 am to ChineseBandit58
someone said something about selfcleaning concreate, a new product used in bridges? anyone knowaboit that?
Posted on 3/16/18 at 7:11 am to tiger7166
quote:
South Florida makes Louisiana government look like a JV corruption team
Not really THAT big a difference...more like Ebola vs. Ebola with the flu.
Posted on 3/16/18 at 7:21 am to ChineseBandit58
quote:
I am not a structural engineer,
Did you at least stay at a Holiday Inn Express?
Posted on 3/16/18 at 7:36 am to PsychTiger
I've been told that Louisiana is the northern most Banana Republic and that includes South Florida as a banana republic.
Posted on 3/16/18 at 8:05 am to Zahrim
I haven’t heard of that type of concrete. I’m definitely interested in learning what type of steel was used for the project
Posted on 3/16/18 at 8:13 am to ChineseBandit58
quote:
Question - was the overhead roof a substantial part of the structural integrity? i
The moment it failed the top portion of the walkway was acting in compression, and the bottom in tension. In the structural world this is called a positive moment.
However if you look at the rendering of what the bridge was supposed to look like, it looks like the top chord was never designed to be in compression, and was temporarily put in compression when it was erected, until the cables come in- at which point the forces and loading change completely.
In other words, someone missed something either in the erection of the bridge, failing to correctly mathematically model the max stress vs available strength- or someone messed up the casting of the precast structure in the shop, which can happen.
Or one of the post tension cables failed when tightening them (as said below), in which case the construction company would be at fault.
This post was edited on 3/16/18 at 8:24 am
Posted on 3/16/18 at 8:15 am to ChineseBandit58
From a local news source. Take it fwiw.
Channel 9 news
quote:
An innovative pedestrian bridge being built at Florida International University had been put to a "stress test" and its cables were being tightened when it collapsed over traffic, killing six people and sending 10 to a hospital, authorities said.
As state and federal investigators worked to determine how and why the five-day-old span failed on Thursday, one factor may have been the stress test that Miami-Dade Mayor Carlos Gimenez said crews were conducting on the span.
Two workers were on the 950-ton bridge when it pancaked on top of vehicles waiting at a stoplight.
U.S. Sen. Marco Rubio tweeted late Thursday that the cables that suspend the bridge had loosened and the engineering firm ordered that they be tightened. "They were being tightened when it collapsed," he said on Twitter.
Channel 9 news
This post was edited on 3/16/18 at 8:16 am
Posted on 3/16/18 at 8:19 am to ChineseBandit58
Bridges kill... must ban them.
Posted on 3/16/18 at 8:26 am to NYNolaguy1
Like a cantilever design it looks from photos.
Posted on 3/16/18 at 8:35 am to thejudge
quote:
Like a cantilever design it looks from photos.
Right, but it failed as a simple truss. The load pattern for a cantilever bridge is completely different than a simple truss, which makes me think either someone missed something big, someone messed up the post tension cables at the site, or there was defective concrete/strands fabricated at the shop.
Heres a crappy youtube video of the collapse
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