Posted on 03/16/2018 12:25:26 PM PDT by C19fan
Engineering experts say investigators looking into the collapsed ‘instant’ bridge in Miami will want to know why a central tower which is usually built to support a suspension bridge was not in place when it collapsed onto Tamiami Trail on Thursday afternoon.
Last week, Florida International University’s official Twitter account posted a rendering of the bridge in its completed form as envisioned by the planners before its opening to foot traffic in early 2019.
The rendering shows a tall central column with cables connecting it to the main span.
Engineers say the design is known as a ‘cable-stayed bridge,’ which is a kind of suspension bridge, according to USA Today.
(Excerpt) Read more at dailymail.co.uk ...
They were playing the percentages, no doubt, and something went amiss. Situations transpired.
A reasonable possibility.
What was needed was temporary center pillars right at the highway median strip. Once the tower and all the cables are installed you can test and adjust cables and test test test and remove the center pillars. And not be hasty about removing them. Only when you are 1000% sure it will hold minus the center pillars.
I’m just a little old lady married to a P.E.; I used to type his papers in college (on a manual typewriter, of course) about pre-stressed concrete and water hammer but know nothing about either.
Just from watching my father mixing up concrete by hand 75 years ago, could it have been way too much sand and way too little cement? He explained to me how important the correct ratios were but that’s probably considered old-fashioned nonsense in todays “superior” institutions of higher(?) learning.
It's one 'o them big ole lumpy things what grows in th' ground.
The thing looks like it was made out of beach sand. All the places that failed, there arent many big jagged chunks, just very small aggregate and lots and lots of sand.
They were barely over half done. They still needed to build the section that was to go over the canal, OH, and dont forget that tall pointy thing that defies the constant gravity.
I wouldnt trust that concrete company to pour the foundation for my grand-kids playhouse!
Two word: Public education
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With that long of a span, the bridge’s own weight was likely too much to stand without uniform support.
Adding pedestrians in motion brought in resonances that easily took it down. It is amazing that it didn’t collapse immediately.
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Was this one of Obama’s “shovel ready” projects?
The assembly instructions from IKEA were in English when they should have been in Mexican.
You are right, of course, so the question would be whether placement of the span could be accomplished prior to installation of the cable stay system.
As you know, in the typical arrangement both the design team and the contractor would have agreed on the calculations that demonstrated the structure was capable of supporting itself prior to installation of cable stays. In fact, we can speculate the structure supported itself for some duration after fab was completed while it was yet on the ground.
It seems relevant the span remained in place for some days after placement and prior to the post-tensioning phase. Even if the roof didn't reguire p-t, it is almost certain there was at least one engineer onsite during p-t. Back in the day, p-t was accomplished by a qualfied specialty subcontractor; is it possible there was no enginer present and the work was performed by the regular crew?
IMHO, at this point, the p-t of this structure is likely a significant element and it either failed on its own or in conbination with some unrecognized error by contractor.
I will agree with you, however, that it would have been prudent to install the foundation and column system to the bottom of the span before placing the span.
Their mistake was using engineers who graduated from that school.
A licensed engineer probably did sign-off on the design.
A soon-to-be-formerly-licensed engineer.
This bridge failure and the resulting death and destruction, including lives and property losses, simply mirrors the "changes," and their "consequences," advocated and carried out by such "champions of change" as Progressive cultists like the Clintons and Obama impose on formerly free American citizens--the same citizens they lure into supporting them by promising "hope," "change," and goodies for the wealthy and the poor, as well as every "identity" group they can identify and tag.
Though slower in imploding and revealing the consequences of Progressive socialist policies, citizens ultimately suffer similar results as those of the "bridge."
The construction process here seems highly questionable.
If the bridge section failed at one end, then it was probably a shear failure. For a structure like that one, the maximum shear force (in simple terms, the force of gravity acting downward, and being resisted by the bridge support points) occurs right at the supports.
If the bridge section failed in the middle, then it would likely be a bending failure. For this bridge section, the maximum bending force occurs at the furthest distance from the support (in this case, the midpoint of two support points).
What a metaphor for socialist policies, once implemented!
That sounds exactly like something I would write, LOL.
I thought them things was "taters"!
Design is not assembly! Had the column been built, and even a few of the interior stays in place, the load at the ends would have been greatly lessened.
Agree with the rest of your comments.
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