Just found that the cable-stays were meant to account for "natural frequencies". It almost sounds like the span itself could be lowered into place and be self-supporting, as long as no other forces were acting on it. If they left it there for 5 days, with traffic moving under it, that could have caused the internal cables to loosen off and the centre span to fail. https://facilities.fiu.edu/projects/BT_904/MCM_FIGG_Proposal_for_FIU_Pedestrian_Bridge_9-30-2015.pdf Start on page 63. No shit!
I bet the next thing to come out was that the Engineering team wasn't onsite or the severity of the loosened cables wasn't properly communicated to the team, if they were told at all. Most of the civil engineers I've dealt with only care about one thing: Make sure the GD structure doesn't fall down and kill somebody. I gotta hope that the engineers didn't just go "oh you know those cables that support the weight of the bridge, they've loosened off.....ahh no big deal, just tighten them up and we'll keep traffic flowing, it's rush hour you know."
There was a Reddit post by a guy who had (supposedly) just walked under the span when it went "CRACK"... and he said he looked back and saw that a bunch of workers all heard the noise, looked up and around, and just kept doing what they were doing. No shouts to "STOP!" or anything. He said the loud "CRACK" came from the centre of the span where it gave way, and it then gave way.
Purely speculative since I’m working on making sure the same doesn’t happen in any of my projects so I’ll wait until the weekend to look more. But based off what Nett and others have said my guess would be that the strands were slipping which would result in failure of the bridge. There likely wasn’t enough time to reinstall the falsework because the bridge would’ve failed by then. Additionally, the way the falsework was set up when the bridge was constructed likely wouldn’t work because of the way traffic lanes are set up below. Which would mean redesigning the system, then first installing it. Which even in best case scenario is weeks, plus you would have people working under the bridge (where no one should have been). So someone figured the best option was to retension the strands. Which may be correct. At that point the road below should’ve been closed to traffic, obviously a logistical nightmare which people wanted to try to avoid. From there is where it becomes a question of who knew what and when were they told.
Based on the video I've seen, there never was falsework. Part of the reason for this design (cables through the span) was to eliminate the need for falsework until the centre cable support was put in place and the cables attached. The span was designed to be self-supporting without the sways.
I just read that post. Sounds like he heard that crack at 9am, and the bridge came down at around 2pm. The more I read about it, this sounds like the cause is going to be attributed to a lack of communication between the parties involved. What a mess. If it comes out that the engineering team knew about this, and didn't immediately stop traffic, people are going to jail.
I don't think I've ever seen such an online focus on an engineering failure like this before. Sure, some stuff has failed, but this just seems to be everywhere. I wonder if it's because of so much of the "totally new and cutting edge" posturing the project has had. It's like it was more about the PR than the engineering, until it collapsed.
I think it might be that so many of us, who aren't engineers, look at the thing and scratch ours heads thinking "How the hell did they not see this coming?" It's just not natural for a span that long and heavy, with a superstructure, to be put up with no other support and expect it to keep standing. Like Rush said..."A board across a stream."
That video is pretty fucking informative... AVE got a hold of some drawings, and does some bench-testing of rod failures. If you're into the engineering of that failed bridge, I think you're really going to appreciate that video.
Here's the video of the bridge failing. On the top of the bridge to the left you can clearly see a dude fall down with it. Must have been a hell of a ride.
It’s not like the movies where the good guy escapes. At the snap of your fingers it was one million pounds of rubble. Just like that.
Apparently an engineer who worked for the company that designed the bridge saw cracks and left a VM for someone back at the office about it. 2 days earlier. https://www.theblaze.com/news/2018/...ut-cracks-in-florida-bridge-prior-to-collapse
Gee, I wonder if social media is going to drag this guy: http://www.nydailynews.com/news/nat...puppy-class-snapping-turtle-article-1.3871401
Here's something to think about before voting "Yes" on recreational marijuana. Our stupidly high insurance rates just went up about 15% with the insurance companies citing recreational dope as the reason. My rates went up about $150 annually so other people can smoke dope.