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Miami Pedestrian Bridge, Part VIII 80

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JAE

JAE

Structural
Jun 27, 2000
15,460
A continuation of our discussion of this failure. Best to read the other threads first to avoid rehashing things already discussed.

Part I
thread815-436595

Part II
thread815-436699

Part III
thread815-436802

Part IV
thread815-436924

Part V
thread815-437029

Part VI
thread815-438451

Part VII
thread815-438966



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I may have missed it, but has the bridge transport procedure been fully addressed? The original plans showed an idealized continuous ramp that allowed the movers to gracefully swing and move the bridge from the construction area to the installation site, but videos and images clearly showed that several short ramps were used to run both ends of the bridge off the curb, and awkwardly jump the far end over the highway center divider, at an angle. I realize the movers had built-in height adjusters, but that move over the divider has always bothered me because it looked like it would be very easy to flex and/or twist the bridge as it went over the divider, or bounce the cantilevered end with a sudden vertical adjustment.
 
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There are photos showing that the concrete had only minor cracks after it was set in position and that only after the post-tensioning was relieved on member #11 (the diagonal nearest the canal) did the significant amount of spalling and rupture seem to occur. While transport damage might have occurred, my opinion is that the final straw was the choice to try to restore the positions of #11 and #12 by restoring tension in the threaded bars in the diagonal without appreciating that tensioning would only make the positions worse.

Sort of like saying - "His sedentary lifestyle and fondness for high calorie snacks contributed to his death, but his inability to out run the bulls at Pamplona was literally the final step in a long journey that started with his first cupcake at age 5 that later joined a love for Hemingway novels."

 
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You have a way with words, Dave. grin

Bill
--------------------
"Why not the best?"
Jimmy Carter
 
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Hemingway resolves dramatic tension a helluva lot better than this bridge did.
 
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Just saw this about OSHA fines. Still thinking how Navarro Brown wasn't hooked to safety harness, and the other worker hooked up when he heard/felt movement. I can't imagine people working up there with those big cracks at 11/12/deck without ensuring they were hooked up safely.
 
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Those fines are peanuts, but it's likely just the beginning of what it will cost them, moneywise. The damage to the reputations of the people and firms involved will be far more costly, though.
 
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Tried looking for the actual OSHA reports on OSHA's website. No luck. But their search system kind of sucks.
 
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Apologies in advance for forgetting how to post links.

Here is a news release dated September 18 that contains links to citations (in PDF form) for each of the 5 companies: Link. Each citation includes an "Inspection Number" that might be of use. I tried using one of the Inspection Numbers in the OSHA accident search page Link in the "Insp Nr:" box with no results, so maybe the reports aren't publicly available yet.

If a site's built-in search engine is crappy, try using Google's "search-string site:URL" search function: "miami bridge site: This allows you to use all of Google's search functions on the site's contents. Apparently the reports are not stored on-site as searchable items.
 
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The Miami Herald is oddly silent on this?
Ahh! digging deeper reveals This is old news (from August) Sorry.
 
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I found the OSHA Inspection Detail Page that accepts the "Inspection Number" taken from each PDF citation noted in my post of 20 Sep 18 21:03 - Link. The Insp Nrs are:
[ul]
[li]1306456 Figg Bridge Engineers[/li]
[li]1304055 Network ESI[/li]
[li]1303015 Structural Technologies[/li]
[li]1304240 Munilla Construction Management[/li]
[li]1304351 Structural Group of S. Florida[/li]
[/ul]
and the completed Detail Pages for all of the inspections are here: Link. Each entry includes a "Related Activity" at the end that has an Inspection Number for a similar incident.

These Inspection Numbers can also be used to search for "Fatality and Catastrophe Investigation Summaries" on this page: Link. The five Insp Nrs all return 0 search results, probably because the cases are still open - the Case Status for each of the citations are listed as either "Open" or "Pending Abatement".

Each Detail Page also lists a common "Report ID" of 0418800 at the top, but a Google Search for it indicates it is a generic report number that has been applied to multiple incidents spanning many years.
 
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This is a followup to my post of 22 Sep 18 05:35 - apologies for any thread protocol violations - this is all new to me and I'm just wingin' it!

The Case Status for all five Inspection Numbers are now listed as "Pending Abatement". The Detail Page for Insp. Nr. 1303015 (Structural Technologies - Link) includes a "Related Activity - Accident ID" of 1318855, with keywords "bridge, fall, collapse" and a summary of:

At 2:00 p.m. on March 15, 2018, a crew of six employees were working on a bridge and were tightening post tensioning rods when it collapsed. One employee was killed and the other five employees were hospitalized with multiple injuries.​

I couldn't find any info on Accident 1318855, but I did a search in the "Fatality and Catastrophe Summaries" page for "bridge collapse" and found an "Accident Report Detail" for - Accident: 104149.015: Link. It includes the same summary shown above.

I assume more information will be available when the Case Status for Insp. Nr. 1303015 is marked as "Closed".
 
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Unrelated to the FIU bridge, but compare the reactions and closures after finding a cracked beam in this SF structure to not even closing the road under the FIU span with MAJOR cracks. Another article said the total shutdown was "out of an abundance of caution" - caution was completely missing in FL.
"Cracked steel beam shuts down SF’s new Transbay Transit Center"

Interesting above. I'd only heard about two people on the canopy, but did see more in a recently posted video or photo. Wondering if the others used safety harnesses.
 
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Regarding my post of 26 Sep 18 04:00, the OSHA summary says one worker was killed and five others were hospitalized, but the news reports at the time only mention one dead and four injured. This March 17 ABC News article - Link - states one employee of VSL Structural Technologies (Navaro Brown) was killed and his two co-workers were hospitalized, then later in the article it says first responders pulled "four unconscious construction workers" from the rubble but it was unclear if that total included the VSL workers.

Brown died after being transported to a hospital, so perhaps the OSHA summary is mistakenly including his hospitalization among the "five others".

Also, in the OSHA news release of September 18 - Link - two of the five companies (Structural Technologies and Munilla Construction) received identical citations that mention 5 workers (Navaro plus the 4 others?):
... employees had installed a single rope lifeline on the canopy of a pedestrian bridge for five employees who were all connected to the same horizontal lifeline ...​
 
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Well in bridge engineering cracks in steel beams are much more serious than cracks in concrete beams. However, the cracks in the FIU bridge where they can slide a folding rule in are alarming to me.

I have designed highway bridges for years before stepping into my current role of inspecting the fabrication of steel and P/S concrete members for the DOT. Considering the factor of safety that is inherent in the AASHTO Code, something very basic had to have been overlooked to have a bridge fail under essentially its own selfweight. In concrete, a new approach to analyzing tricky concrete design problems is the Strut-And-Tie modeling. I wonder if there was something there related to S-A-T that was missed?
 
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Having read the 9 Aug NTSB update which contains 5 photos on the cracked joint at the bottom of Member 11 taken a few days prior to the collapse I cannot help but to put forward my own opinion after working in the civil engineering industry for 54 years.

(1) The persons who have access to the photos showing the locations, severity and and extents of the cracks would appear to have inadequate knowledge of structural engineering if they were party to permitting the bridge to be fixed in situ with live traffic flowing underneath.
(2) The cracks are sufficient indications confirming a major connection failure/under-design was taking place/present at the bottom of Member 11 which carried one of the heaviest loads. Diagonal member 11 could only perform its structural duty if it could be adequately restrained by the horizontal deck by counterbalancing its huge axial force, thereby putting the deck in large tension. The deck showed cracking spreading 45 degree on both side to the back which has nothing but air to stop the diagonal member 11 from pushing outward. The first four photos in NTSB8 Aug Update clearly indicate the deck was incapable of holding the Member 11 in place resulting the alarming separations of concrete.
(3) The pattern, extent and severity of the cracks are enough to halt the construction process immediately it requires a permanent cure. The cracks are major, structural and requiring a substantial rectification and/or possibly a local joint strengthening. If the same bridge were to rebuilt to the same design with the same materials it would simply collapse again.
(4) The cracks discovered before the collapse are so severe that finding out the root cause had to be more important than completing the construction as further construction activities could make the bridge less safe. In the end it was the adjustment of the tension in the bridge that triggered its collapse.

In the 9 Aug NTSB update Figure 4 shows a small triangular piece of Member 11 was still attached to the deck with the rest of Member 11 totally sheared off horizontally. Figure 1 and 2 show the deck on the left and right side of Member 11 "had" sheared off and totally separated from the rest of the deck at the deck level. The sheared off portions were monolithic with the vertical member 12 but there was nothing but air to prevent the cracked portion of the bridge from moving further away. Are these four photos on their own not enough to tell every structural engineer that something huge is going to pop?
 
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Thank you, Pete.

That appears to make it official; the failure of this bridge is due to engineering design errors. Even if the contractor(s) also messed something up they've confirmed what I believe we all suspected; that there were design errors in both capacity and load at that end joint.

Given the convoluted nature of the liable parties and timeline of events combined with the very alarming photos and reports; I would reason this could have very far reaching consequences for the structural engineering industry. I wonder how insulated FDOT, FIU, and any other authorities and owners are on this?

Ian Riley, PE, SE
Professional Engineer (ME, NH, VT, CT, MA, FL) Structural Engineer (IL)
American Concrete Industries
 
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