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Just from what I have read, the roof of the bridge was a 42 foot span of concrete. why use concrete? It is cheaper, and it can be quicker to produce. But it is much heavier, and more importantly its tensile strength is terrible. If they put a considerable amount of stress on it, it would not bend much at all.
Normally you build in a factory of safety of 5, which means you build in 5 times the strength you need. Maybe it is different for this new "advanced bridge construction" method they used.
I am a degreed (not licensed) engineer - although it is mechanical, not civil.
Me too EE not CE. I think the span was over 100 feet. (And one of the questions being raised is why there was not a center pier).I too find the roof interesting. A lot of structure above the deck. Then again the triangular struts holding the roof look to me like structure...providing the stiffness for the span.
In six months or so there will be a good report on what went wrong. Be an interesting read. Unfortunately in the near term we can only speculate.
I don't know how they work their safety factors...for instance I would presume that they have to survive a maximum hurricane. But I don't think the civil engineers go for factors of five...more like two or two and a half.
A student died last year trying to navigate thru all that traffic. That's what prompted the State to build it.
Whether or not a private company would have built it in the absence of a State is anyone's guess. Since it's a university sponsored by the State I would assume no.
Having said that...accidents will happen regardless if it's a private bridge or a State bridge. This doesn't change the fact that morally and logically the private way is the only option.
Can you honestly suggest that some private company might have one day thought, "hey let's go build a pedestrian bridge over that busy road.....maybe we can put a toll on it or something....."
?????
Be serious.
Give Rick Scott and the 100% GOP Legislature, inspectors, highway dept, etc. a call and ask why their landline has voicemail instead of a person:
"A lead engineer responsible for a pedestrian bridge that collapsed near Miami left a voicemail message for a state transportation official warning of “some cracking” two days before the structure crashed, state officials said Friday night."
That engineer was out of the office.
Far be it for me to defend the Super State.
But why did you omit the most vital aspect of the story... ??? Politics?
(Of course, I am referring to the manager who worked for the contracted engineering firm saying on that voicemail that "the crack isn't any kind of safety issue or anything"......)
Me too EE not CE. I think the span was over 100 feet. (And one of the questions being raised is why there was not a center pier).I too find the roof interesting. A lot of structure above the deck. Then again the triangular struts holding the roof look to me like structure...providing the stiffness for the span.
In six months or so there will be a good report on what went wrong. Be an interesting read. Unfortunately in the near term we can only speculate.
I don't know how they work their safety factors...for instance I would presume that they have to survive a maximum hurricane. But I don't think the civil engineers go for factors of five...more like two or two and a half.
I did elevator design for awhile... we did 5 for factor of safety. That's what I remembered in school as well.
No one likes stuff like this to happen, but the failure analysis is interesting.
Now I'm on this now to see what happened... and now I am sort of understanding this.
The whole bridge was not up. That was just the first span across the roadway. If you look at the proposal above, there are suspensions that run above the bridge that support the structure across the roadway. They were not installed.
The video of the collapse is below. Something gave way where you could see the structure sink slightly before it totally gave way. You can see (in the slow motion portion) there is activity occurring on the structure, and right beneath it, that's where it looks like one of the diagonal support members failed.
One more - then I am done on this for now. The first 1:30 shows the process of how that portion of the bridge was put in place. Again - that was just the first section, and it was NOT fully supported as it was displayed in the proposal. The newscaster specifically mentions that they were performing a stress test. That, to me, is the failure... the fact that they were doing a stress test on a span of mainly concrete that wasn't properly supported - with traffic flowing underneath.
FIGG Bridge Engineers knew that "numerous wide and deep structural cracks" had developed and lengthened daily, but dismissed them, the report says. The document contains multiple texts and emails from crew members concerned about the growing cracks.
One crew member sent his supervisor a text message with a picture of a construction joint with cracks running through it in multiple places.
"It cracked like hell," the crew member wrote in the message.
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