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posted by Fnord666 on Thursday June 13 2019, @02:27AM   Printer-friendly
from the a-bridge-too-far dept.

Florida International University ("FIU") needed a foot bridge to cross a canal and busy street. An FIU committee selected a design without redundant structural support because they were wanting a dramatic landmark (the bridge looked like it was a cable stayed design, but it wasn't -- the faux cables were almost entirely aesthetic). The original specs had called for structural redundancy so that the failure of one structural member would not cause a collapse -- the committee ignored this requirement in favor of visual appeal.

The engineering firm selected for the bridge (FIGG) made an error in calculation for a critical member at the end of the span. The engineering firm providing peer review of the design (Louis Berger) has refused to turn over to OSHA, certain documentation regarding what it was supposed to evaluate and what it actually did. When the bridge section which had been built on the side of the road was moved into place, experienced workers became extremely worried about cracks that started appearing and made their worries known to those up the chain. A FIGG engineer examined the cracks but determined they "did not present a safety concern even though its engineers did not know what caused them — and despite clear evidence that they were growing daily." Apparently, the guidelines are that cracks deeper than a half inch are to be taken seriously and these were much deeper and growing daily -- one photo shows a crack 4" deep.

The final bridge would have two sections -- the long section over the roadway and a short section over the canal. The canal section was to be built in place and tied into the long section. Had the canal section been built first, the risk of collapse for the section over the roadway would have been reduced because it would have shored up the longer road section.

The bridge collapsed killing six and permanently disabling another.

Article regarding the OSHA report: https://www.miamiherald.com/news/local/community/miami-dade/article231428938.html
Article regarding independent engineering review with some good explanations which I, as a non-engineer, found informative: https://www.miamiherald.com/news/local/community/miami-dade/article212571434.html
Time Lapse Video of Bridge Collapse (released by FIU): https://www.youtube.com/watch?v=vrBOF2jugFM
Original Soylent item: https://soylentnews.org/article.pl?sid=18/03/19/1746219
Link to the OSHA report itself: https://www.osha.gov/doc/engineering/pdf/2019_r_03.pdf


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  • (Score: 0, Informative) by Anonymous Coward on Thursday June 13 2019, @10:08AM (1 child)

    by Anonymous Coward on Thursday June 13 2019, @10:08AM (#855062)

    https://www.miamiherald.com/latest-news/73nar3/picture208745869/alternates/FREE_1140/fiu%20bridge%20ntsb%20investigators.jpg [miamiherald.com]
    not that i have seen a lot of broken building material, but this looks more like crushed rock, than brorken conrete...

    /zug

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  • (Score: 2) by RS3 on Saturday June 15 2019, @07:17PM

    by RS3 (6367) on Saturday June 15 2019, @07:17PM (#856049)

    I don't know why you were downmodded. I'd love to know who's doing that.

    I'm not a civil engineer nor concrete expert, but I've done some, and studied some. You may know, and certainly notice in the pictures in your linked article, that there's "rebar" - reinforcing steel bars - embedded in the concrete. Those greatly strengthen the structure, but they also unfortunately create weak spots where the concrete will fail when something catastrophic happens. So the net result is that crushed rock look. It also shows fairly good consistency in the concrete's consistency. If there was a particularly weak spot, it would crumble even more, and leave larger unbroken sections. The picture is of the highest stress area of the bridge, which is why that section is so crumbled, and other sections look surprisingly intact.