Posted on 03/23/2018 2:25:42 PM PDT by EVO X
According to several sources, the tube stays (they were never cable stays) for looks ONLY. They had nothing to do with the support of the bridge. They did not even have provisions for length adjustments, which is absolutely necessary for cable stays. They were only there to turn a lowly bridge into a work of “art”. Of course, it turned out to be “performance art” in 4 days.
“What I tell you three times is true” - The Hunting of the Snark.
The trouble is, it just doesn’t add up. There are design diagrams on the net showing the tower and the stays, which, as I’ve noted in a previous post, have been referred to as “pipes”.
The tower and stays are a massive structure, and include stays for a shorter span on the other side of the tower.
Also, as I’ve noted here, the span, as installed, included massive and visually complex “attachment points” for these stays. And also again, as I have noted, the struts on the installed span were designed to line up with the stays, as I checked by graphical comparison of news photos of the span with the published design.
Now these struts are claimed to be part of a “truss” which has no top bar, but only the roof to function as such, and which is what gave way, according to my own perception of the “instant of collapse” video.
So how can it possibly be claimed that this span was designed as a truss bridge, when it is so specifically, and asymmetrically, adapted to the tower and stays?
The FBI swooped in and invoked jurisdiction over the crash, which had never been done before or since. By doing this they relegated the NTSB to back bencher status.
Except for the cylinder break test to check to see if the concrete break strength was per spec.
The contractor should not have been messing with tensioning while there was traffic passing underneath. No traffic stoppage = no work may be done.
The municipality WOULD have closed the street if the contractor said there might be a problem with the bridge. A workman flagging down a police car and saying there was a potential hazard with the bridge would have resulted in an immediate traffic shutdown. But then the contractor would have had to explain what the problem was to the satisfaction of public-safety personnel before the street would be re-opened.
I suspect the contractor did not want embarrassing questions to be asked, and decided to try to fix it without saying anything. And people died. Some people need to go to jail for negligent manslaughter.
My guess is somebody was doing a "belt and suspenders" approach, where the combination of both the trusses and the tower/stays would have provided the required stability. Remember, they advertised that this thing was supposed to withstand a Cat 5 hurricane, and it didn't even hold up on a calm day.
What truss? I'm saying that all I see are the struts, obviously designed to connected the deck to stays. These have some perpendicular struts for support, so you have the semblance of a truss, but strangely asymmetrical, and with no top bar. So is that a truss? ... a DESIGNED truss?
The FIU bridge was a truss bridge, its designers, the FIGG Bridge Group, confirmed after the collapse. Many have assumed it was a suspension bridge because renderings of the finished structure show a mast with pipes or cables connecting from its tip to the bridge in a sail-like pattern. Observers, including some engineers, have posited that had the mast been in place, the bridge might not have collapsed.But in fact the mast would have provided no vertical support. FIGG advertised that as a “cable-stayed” bridge, and plans and other materials on the FIU website say the mast was there mostly to dampen vibration, provide some “stiffness” and create dramatic aesthetics.
The wikipedia entry says “The bridge spans used a novel concrete truss design invented for this project, a ‘re-invented I-beam concept’”. The concrete formulation used was also new. So we have two new and untested concepts being employed here.
The FIGG group are the perpetrators of this travesty!
This is their story! It makes no sense! I’m not buying it!
At first, I couldn’t believe they could get away with this. Now I wonder.
I wonder if it’s too late already to see the documentary trail. A trail of ashes, it may be.
I saved, at least, a graphical copy of the original design, in case this should disappear.
bump
> “So how can it possibly be claimed that this span was designed as a truss bridge, when it is so specifically, and asymmetrically, adapted to the tower and stays?”
There are a lot of things that don’t make much sense. Architects are the worst at that. When the try to make something functional into “art”, they spoil it. Just like happened here.
We have a cable stayed bridge near my home (look for the Bob Kerry pedestrian bridge — a pork-barrel project if there ever was one). It is a LOT lighter than the bridge that collapsed. If it really was a stayed bridge, the concrete truss could be a LOT lighter than it was. The “roof” was also a LOT heavier than needed to keep rain off the pedestrians. Evidently, it was not heavy enough to keep from buckling and collapsing in compression, though.
From what I have seen, the claim that it was a disguised truss bridge seems to make more sense than it being a cable-stayed bridge.
Not to me. It was a "cable-stayed" design without the stays, and it collapsed within hours of installation. What could make more sense?
> “Not to me. It was a “cable-stayed” design without the stays, and it collapsed within hours of installation. What could make more sense?
I guess we will have to agree to disagree. Right now, there is no way to tell what happened. Everything is speculation. When the engineering report is issued, we will know who is right.
A rash claim! At any rate, I don't want a report, I want an explanation, and I don't see one coming. That's my problem.
I agree re: Juan Browne. He’s pretty sharp. I watched a lot of his videos through the Oroville crisis.
I’m guessing this is a process failure rather than a design failure. Whether it was the mix, the transportation method, or insufficient curing time. I mean, it could be the design, but that would have to pass through a lot of approvals before being used.
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Since design compressive strength is quite low, the test is of little value. It will likely exceed the requred strength, but probably not by as much as it should.
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Protecting their SES friends.
Juan mentioned in a video the day before, that if a truss failed the bridge was coming down. I haven’t seen answers yet on why they were tensioning the bridge 5 days after moving the span in place. We may not have an answer for a while if everyone is lawyered up.
Here is a time compressed video of the move from start to finish. Around 6:38 you can see the span move into place. Around 7:00 workers start disconnecting the support rigging. At this point the rigging has done its job.
https://www.youtube.com/watch?v=hvZVuN-CHnE
The next video gives a clear view of the rigging down below at .18 and .19 seconds. The rigging system is clearly part of the design!
https://www.youtube.com/watch?v=Ik1fCeo4CpQ
The next short video show the cables disconnected on the walkway.
https://www.youtube.com/watch?v=SBoE34-WZoE
See my 79. It looks to me like the transport rigging was designed early on in the design process. The final design of the underside of the walkway was not flat. They used wedges to prevent rocking during the move. I forgot to post this in 79, but you can clearly see the wedges at .36
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