Some speculation I’ve seen is that the “stress test” was pulling up on certain parts of the bridge, and the cable snapping caused the bridge itself to drop a little. *That *would be the weight that did the damage.
I have read that the death toll – presumably motorists below – to be 4, with 10 sent to the hospital.
I found this
“If anybody has done anything wrong, we will hold them accountable,” said Florida Governor Rick Scott …
to seem just a little absurd.
Catastrophic engineering failures are rare. There are so many redudant systems to prevent a collapse.
I can’t imagine how this bridge design passed modern computer modeling and simulation tests.
Some very serious errors occurred either in the design or construction.
I wouldn’t be surprised if homicide charges are eventually fired. An error this big is undefendable. I can’t recall a catastrophic failure on a new structure before.
The Tacoma Narrows Bridge had a serious flaw. Called old windy for flapping in the wind. But over engineering kept it up for several months.
Gallopin Gerty
blasted edit time out got me.
They were certainly confident a few days ago.
I’m finding these supposed reports (from the Santa Monica Monitor???
) that there was testing taking place WHILE traffic was allowed to pass underneath the bridge and an accident during the test caused the collapse to be highly questionable at best. A complete and shocking engineering disaster in 2018.
New information. May be significant if the cables pulled beams off their support columns.
Still, imho redundant systems should have held the bridge in place until engineers could fix the problem or safely take it down.
It’s very fortunate that there weren’t more deaths.
Some background information.
It was a “signature” bridge, meaning it was designed to look fancier than it really was.
It doesn’t look very fancy to me though. It looks like someone wanted a nice simple cantilevered truss bridge like this, and someone else really wanted a tall tower and cables like this, and they compromised and did both.
Reminds me of this - Hyatt Regency walkway collapse. 115 dead. Seems a sort of seat of the pants last minute design change was the cause.
While it might or might not have contributed to the collapse, why in hell was a stress test being performed on an uncompleted structure? It would be like testing a box girder while the guy is still welding it: The action tells you nothing about how the structure will perform when it is finished. If the test was done to ensure the bridge would stand until the suspension cables were in place, why in hell was it performed without closing the roadway underneath? IANA engineer but this makes no sense.
“Stress test” does not necessarily mean putting a realistic stress and seeing if it would fail. They could be putting a very small stress and measuring the strain (i.e. measuring how much it deforms under that stress).
It doesn’t have to be done on a completed structure. They can (and probably should) test every piece of the bridge to make sure they are up to design spec. At every stage of construction, they can test the unfinished structure and make sure the structure behaves as expected. If they put a tiny amount of stress - or even a negative amount (i.e. lifting a part of the bridge with a crane) and measure the response, that still tells you if the bridge is built to spec so far. And since they are not testing the structure to destruction, there is (in theory) no need to stop traffic under it.
Interesting case. Glad it wasn’t in my state else we’d be asses and elbows fielding half-baked questions from reporters and legislators.
A brief look at the desired product left me with “wow, way over the top. For a lousy pedestrian bridge they make such a major structure?” Okay, maybe they really want to make a good impression on visitors to FIU.
I’ve never heard of stress testing a new bridge. For new construction, you’ve got concrete cylinders and samples of the steel to test in the lab. If the design is sound you’d never think of testing the bridge.
If I had to guess, I’d put my money on the construction staging. Either the structure was not properly evaluated for this particular stage of construction or the plans weren’t followed completely. I find it hard to believe the designer was incompetent, generally for projects of this magnitude you’re going to hire one of the larger consulting firms with the experience and expertise to not have failures like this.
And I thought about this one. I had several relatives at that race–they weren’t on the bridge, but were still on-site to see the chaos afterwards.
The bridge was designed with a pylon and support cables - Seems to me as though they took the temporary supporting structures away before they added the permanent supporting stuff.
-Except I can’t believe it’s that simple, but I also can’t believe the pylon and cables were purely decorative - so if they’re required, and they’re not there, then the structure is at risk of failure.
Maybe it’s confirmation bias on my part, but this kind of fuckup seems to happen more with pedestrian bridges. Like someone is thinking “oh, it’s not like a REAL bridge, not like it has to hold up a truck”.
I read an article today that said that the engineering company that designed the Florida bridge also designed a bridge in Virgina … that collapsed during construction.
Here is an 80 page PDF on the proposal for the bridge.
in that article:
"Construction on the South Norfolk Jordan Bridge was put on hold after a truss used to build the bridge shifted,
doesn’t immediately identify the failure as a design flaw; could have been an error in assembling that segment or during construction.