Pedestrian bridge collapse at Florida International University FIU Miami

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Re: Pedestrian bridge collapse at Florida International University FIU Miami

#76

Post by TollandRCR » Sat Mar 31, 2018 5:44 am

The Miami Herald has a two-week summary of what is known and what is suspected about the collapse of the FIU pedestrian bridge.:
http://www.miamiherald.com/news/local/c ... 58659.html


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Re: Pedestrian bridge collapse at Florida International University FIU Miami

#77

Post by TollandRCR » Sun May 06, 2018 7:34 pm

NTSB has confirmed that two Federal agencies and the Miami-Dade police department are conducting criminal investigations of the FIU bridge collapse. They also said that they have prohibited FDoT from releasing certain information until the NTSB report is finished.


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Re: Pedestrian bridge collapse at Florida International University FIU Miami

#78

Post by Mary Quite Contrary » Sun May 06, 2018 11:56 pm

Amy idea how long that will take? Is it ballpark of 6 months or years?


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Re: Pedestrian bridge collapse at Florida International University FIU Miami

#79

Post by TollandRCR » Mon May 07, 2018 2:01 am

Mary Quite Contrary wrote:
Sun May 06, 2018 11:56 pm
Amy idea how long that will take? Is it ballpark of 6 months or years?
Nobody knows, or at least nobody is saying. A firm is conducting tests on the cement, the post-tensioning rods, and other parts of the bridge; that could take a while.

If anybody committed a crime i should bet it is in the materials. We have seen that before.


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Re: Pedestrian bridge collapse at Florida International University FIU Miami

#80

Post by TollandRCR » Tue May 08, 2018 11:07 am

May 7, 2018




In a February email that was unintentionally released by Florida International University, the FIU construction and engineering team said that it had detected cracks in a diagonal support member at the North end of the bridge. The collapse began at the North end. Outside experts have reportedly said that truss was under-designed -- incapable of supporting the weight above it.

http://www.miamiherald.com/news/local/c ... 49384.html


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Re: Pedestrian bridge collapse at Florida International University FIU Miami

#81

Post by TollandRCR » Tue May 08, 2018 1:40 pm

The Miami Herald says that this crack might have signaled imminent collapse. I wonder whether this might be the reason for the three criminal investigations — a question of negligent homicide.


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Re: Pedestrian bridge collapse at Florida International University FIU Miami

#82

Post by RoadScholar » Wed May 09, 2018 1:49 pm

I nominate for the main blame whoever made the call not to halt traffic during that last procedure. If they'd done that, it would just have been an expensive structural goof. Now it's homicide. :madguy:


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Re: Pedestrian bridge collapse at Florida International University FIU Miami

#83

Post by TollandRCR » Wed May 09, 2018 4:28 pm

This bridge was intended to be an exemplar of Accelerated Bridge Construction, a field in which FIU has an international reputation. One of the selling points for ABC is that bridges can be constructed with minimal traffic disruption. It was truly amazing how quickly that initial span was moved from its construction area to span the street.

I suspect, without evidence, that FIU engineers -- not contractors -- resisted closing the street for work on the post-tensioning system and for repairs to cracks. In addition, the Florida Department of Transportation must approve closing streets like that. That may take a bit of time. ABC argues that such disruptions and delays are unnecessary.

It is disturbing that the February email was not intentionally made available and that it took an "inadvertent" release for outsiders to see that worrisome photo. I do not like it when universities appear to engage in cover-ups.


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Re: Pedestrian bridge collapse at Florida International University FIU Miami

#84

Post by Sterngard Friegen » Wed May 09, 2018 4:55 pm

TollandRCR wrote:
Wed May 09, 2018 4:28 pm
This bridge was intended to be an exemplar of Accelerated Bridge Construction, a field in which FIU has an international reputation. One of the selling points for ABC is that bridges can be constructed with minimal traffic disruption. It was truly amazing how quickly that initial span was moved from its construction area to span the street.

I suspect, without evidence, that FIU engineers -- not contractors -- resisted closing the street for work on the post-tensioning system and for repairs to cracks. In addition, the Florida Department of Transportation must approve closing streets like that. That may take a bit of time. ABC argues that such disruptions and delays are unnecessary.

It is disturbing that the February email was not intentionally made available and that it took an "inadvertent" release for outsiders to see that worrisome photo. I do not like it when universities appear to engage in cover-ups.
Could the bridge have been braced after the cracks were found? That would not necessarily have required traffic to be stopped during repairs.

I think there was a cascade of failures here and that the list of culpable parties will be so long that no one will suffer the consequences.



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Re: Pedestrian bridge collapse at Florida International University FIU Miami

#85

Post by RoadScholar » Wed May 09, 2018 5:11 pm

Stopping the traffic would mean lost time, so maybe liquidated damages for late performance, so lost money; and embarrassment, or lost face.

My question: how does that balance out loss of life?

I'm not talking about a requirement that it be done every time. I'm saying as soon as somebody had any question about the procedure like seeing unexplained cracks, why did they not then stop traffic in this particular instance?

To me that seems criminally careless.


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Re: Pedestrian bridge collapse at Florida International University FIU Miami

#86

Post by TollandRCR » Wed May 09, 2018 5:17 pm

I cannot answer that question. An engineer might be able to do so.

I agree that there is a cascade of failures here. It may have started with the decision to construct a bridge of concrete rather than steel, then deciding that the roof should also be concrete and thus heavy. It is possible that the NTSB will have concerns about the concrete that was used. Has the self-cleaning concrete been used for a bridge before?

I wonder whether the crack that we see in that photo was repaired. Does the self-cleaning property make repairs more difficult? Is that crack the one that the engineer reported to FDoT? If not, were there several cracks?

Questions of this nature may be what NTSB is considering.


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Re: Pedestrian bridge collapse at Florida International University FIU Miami

#87

Post by TollandRCR » Wed May 09, 2018 5:25 pm

RoadScholar wrote:
Wed May 09, 2018 5:11 pm
...
To me that seems criminally careless.
That is exactly why i maintain an interest in this matter that is so far outside my fields of competence. This may be another instance of corporate, governmental, and university (!) arrogant disregard for human well-being. I think that is a real problem in our society.


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Re: Pedestrian bridge collapse at Florida International University FIU Miami

#88

Post by RoadScholar » Wed May 09, 2018 5:36 pm

Yes. That.

I guess my point was that whatever else contributed, whether it turns out to have been poor design calculations, substandard materials or handling, flawed installation methods, unwise design modifications, combined effects of several factors colliding... not stopping the traffic before proceeding to that last step was "the difference that makes a difference." Remove that, and everybody would have made it home to dinner that night even with all else being the same.

If anyone in a position of responsibility noticed something amiss and carried on anyway, that's what's inexcusable.


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Re: Pedestrian bridge collapse at Florida International University FIU Miami

#89

Post by JohnPCapitalist » Wed May 09, 2018 6:40 pm

Sterngard Friegen wrote:
Wed May 09, 2018 4:55 pm
I think there was a cascade of failures here and that the list of culpable parties will be so long that no one will suffer the consequences.
Very possibly true. However, if there are a bunch of e-mails should emerge along the lines of "well, it's just a #$*!ing pedestrian overpass, how bad could it be? After all, we're not designing the next Kansas City Hyatt..." it is gonna get uncomfortable for a lot of people.



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Re: Pedestrian bridge collapse at Florida International University FIU Miami

#90

Post by TollandRCR » Wed May 09, 2018 7:26 pm

"Steel-truss bridges have been commonly used in roadway construction going back decades. But they have a well-known vulnerability: If a vehicle hits one of the horizontal support trusses, the entire span can collapse.

"That’s what happened in the 2013 collapse of a 1955 steel-truss bridge over the Skagit River on Interstate 5 near Seattle: A truck carrying an oversized load struck supporting steel struts along one side of a bridge span, which split apart and fell into the river. That’s because there were no backup or redundant structural elements to support the span if one piece failed.

"That’s also why truss bridges are mostly avoided in modern road construction, said Ralph Verrastro, a Cornell-trained bridge engineer with Bridging Solutions, a Tampa firm. “A through-truss bridge can catastrophically fail,” Verrastro said."

Another factor may have been the size of the initial span. It was the largest pedestrian bridge ever to have been moved by Self-Propelled Modular Transportation.


Read more here: http://www.miamiherald.com/news/local/c ... rylink=cpy


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Re: Pedestrian bridge collapse at Florida International University FIU Miami

#91

Post by TollandRCR » Mon Jun 04, 2018 3:34 pm

Try this

http://www.courant.com/news/connecticut ... story.html

State officials have said as many as 34,000 homes in 36 towns in north central and eastern Connecticut might have crumbling foundations. A mineral known as pyrrhotite — used in the concrete aggregate for the foundations that are now crumbling — is partly to blame.

Insurance companies have denied homeowners' claims, saying the problem does not qualify for coverage under their definition of collapse. Homeowners have been left to bear the burden of a repair, which can cost more than $200,000.


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Re: Pedestrian bridge collapse at Florida International University FIU Miami

#92

Post by TollandRCR » Mon Jun 04, 2018 3:54 pm

Photographs released by NTSB noted three cracks in the north end of the [FJU pedestrian bridge] span, where crews were working on tensioning a structural component of the crossing when the failure occurred. A crew was on the bridge working on the diagonal beam at the time.


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Re: Pedestrian bridge collapse at Florida International University FIU Miami

#93

Post by RTH10260 » Mon Jun 04, 2018 6:10 pm

TollandRCR wrote:
Mon Jun 04, 2018 3:34 pm
Try this

http://www.courant.com/news/connecticut ... story.html

State officials have said as many as 34,000 homes in 36 towns in north central and eastern Connecticut might have crumbling foundations. A mineral known as pyrrhotite — used in the concrete aggregate for the foundations that are now crumbling — is partly to blame.

Insurance companies have denied homeowners' claims, saying the problem does not qualify for coverage under their definition of collapse. Homeowners have been left to bear the burden of a repair, which can cost more than $200,000.
Background article: https://www.americangeosciences.org/cri ... oundations



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Re: Pedestrian bridge collapse at Florida International University FIU Miami

#94

Post by GlimDropper » Sat Jun 16, 2018 5:34 pm

A whole lot more detail on not much new:

FIU had grand plans for 'signature' bridge. But the design had a key mistake, experts say
It started as an idea for a footbridge to get college students safely over the busy Tamiami Trail.

But fueled by millions of dollars in available federal stimulus grants, Florida International University's doomed pedestrian bridge morphed into something far more ambitious: A gleaming testament to FIU's lofty institutional aspirations and the linchpin in a grand plan to create a true college town in the neighboring working-class suburb of Sweetwater.

As FIU's ambitions grew, the need to shape a uniquely memorable bridge drove key engineering decisions, resulting in a striking but unorthodox concrete structure. But the design hid a fatal flaw that its designers and reviewers failed to recognize, according to experts who have examined plans and mathematical calculations for the project.

The unconventional placement of diagonal supports in an uneven zig-zag pattern along the bridge produced a complex structural web with a glaring weakness at a key connection point, apparently overlooked by designers at FIGG Bridge Group, say three independent structural engineers who reviewed nearly 2,000 pages of calculations for the bridge at the Miami Herald's request.
It's tough to know who all will get blamed but it sure was supposed to be a pretty bridge.



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Re: Pedestrian bridge collapse at Florida International University FIU Miami

#95

Post by ZekeB » Sat Jun 16, 2018 5:57 pm

While I’ve never cared for ugly things, I’ve always picked function over form.


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Re: Pedestrian bridge collapse at Florida International University FIU Miami

#96

Post by Sam the Centipede » Sat Jun 16, 2018 6:08 pm

I havent read the report (or taken much interest in the affair), so I can't comment on whether they had introduced frailties into the overall design.

But I have read reports on other failed projects pointing out that the design of connections between elements of reinforced concrete structures is critical and does not always receive as much attention as necessary. Typically overall design methods focus on axial forces and bending moments and don't necessarily highlight how large the shear forces are at connections and how they are transferred through connecting elements. Some computer models also are poor at calculating the shear stresses in those critical regions (don't ask why, explaining needs greek letters and squiggly symbols) so can be important to avoid accepting the pretty colored stress plots showing everything is fine without an extra look.

Structural engineering is an odd discipline in that it tends to be binary in its results: either a structure stands up or it collapses spectacularly. If it stands up, it's not obvious whether the structure has massive reserve capacity or that is standing up by the skin of its teeth; it just stands there quietly. That's not always true, but it does mean that feedback to designers is limited.

My guess about blame? It will probably come down to asking why the designers didn't put someone with seriously good experience onto verifying the design at a detailed level. But that's only a guess. Hindsight is a wonderful thing.



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Re: Pedestrian bridge collapse at Florida International University FIU Miami

#97

Post by TollandRCR » Sat Jun 16, 2018 7:27 pm

The University of Miami faced the same problem as did FIU: students were being killed trying to cross a busy highway to get to the campus. Unlike FIU, the University of Miami chose a simpler and cheaper solution. The result was this:



I suppose the FIU bridge was more beautiful. But a big part of the beauty was fake: the "cables" and central pylon had no structural role. That saddens me.


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Re: Pedestrian bridge collapse at Florida International University FIU Miami

#98

Post by TollandRCR » Sat Jun 16, 2018 8:16 pm

This Miami Herald article is thorough and informed
http://www.miamiherald.com/news/local/c ... 71434.html


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Re: Pedestrian bridge collapse at Florida International University FIU Miami

#99

Post by TollandRCR » Sat Jun 16, 2018 9:02 pm

Writing in Forbes and advocating Slow Engineering along the lines of the Slow Food movement, Bernie Carlson concludes with a myth:
To help students appreciate this holistic approach, I would tell them the mythic story associated with the great dining hall at New College, Oxford. The ceiling of the dining hall is supported by huge oak beams, some 2 square feet and 45 feet long. Legend has it that when New College was created in 1379, it was given forested land as part of its endowment, and over the centuries, the college’s foresters made sure to preserve very large oak trees. The foresters did so because they knew that, sooner or later, the beams in the dining hall would become infested with beetles, causing them to rot and would need to be replaced. While it is not clear there was ever a specific grove of oaks earmarked for the great hall, the myth conveys the importance of understanding how materials and natural processes underlie all of what we do as engineers. You can’t have a great hall with massive oak beams unless you understand where the oak beams come from and how long it takes for the oak trees to grow.
As may be clear, i have been angry at FIU since the catastrophe. Universities do not put human lives at risk.

The climate at FIU was the opposite of waiting for the oaks to grow.


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Re: Pedestrian bridge collapse at Florida International University FIU Miami

#100

Post by tencats » Fri Aug 10, 2018 3:20 pm

Cracks in FIU bridge grew to ‘shocking’ size days before collapse, new photos show

Cracks that appeared in the Florida International University bridge days before it collapsed were far more extensive than previously disclosed, according to photographs included in a preliminary report issued Thursday by the National Transportation Safety Board.

The photos show four alarming-looking cracks — one at least 3 1/2 inches deep into the bridge’s deck — developing in precisely the section of the span that is believed to have failed on March 15, killing five motorists and one worker.

Given the size of the cracks, the photos raise new questions about why officials at FIU, the Florida Department of Transportation and the private contractors running the project did not seek to shut down the busy road underneath the bridge.

Read more here: https://www.miamiherald.com/news/local/ ... rylink=cpy
Image
Image
Photos show cracks in FIU bridge grew before tragedy


More.
NTSB pictures show cracks on FIU bridge days before collapse
https://www.local10.com/news/florida/mi ... e-collapse



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