# FL bridge collapse



## artisanstone (Nov 27, 2007)

Hard to imagine this happening with the current mindset on jobsites. Someone is going to be hit hard. No need to link, it's all over the news.


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## 480sparky (Feb 1, 2009)

I noted one student (re: similar to the Florida school shooting survivors) saying: "Why do you continue to build over a road with vehicles on it?"


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## RangoWA (Jun 25, 2014)

One eyewitness said a crane dropped a load where it buckled.


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## KAP (Feb 19, 2011)

Sad... read there was attempts to delete lots of twitter posts praising it's construction... like that's going to help... :no:


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## Fouthgeneration (Jan 7, 2014)

the Final product was to have cables to a tower at one end and another piece on the bedroom town side?

There is some concern the use of so much Titanium dioxide "pollution whitener" might have slowed/ lowered the rate of the concrete strength gain "enough to keep the bridge white for 100 years with out painting..."

On further review it is unlikely Ti- O2 weaken or slowed hydration...

Tree Huggers/LEED pimps Kill again? Maybe?

To soon to tell.

Love to hear from MEDEEK.

Will liberals try to out law driving under bridges now?

Will high school students skip another day of school to protest the deaths? More kids died travelling to various protests last week then from massacres......


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## rustyjames (Aug 28, 2008)

Fouthgeneration said:


> Tree Huggers/LEED pimps Kill again? Maybe?


I've been out of the LEED loop for a few years now that I'm retired (although still maintain the credential since it was hard to achieve) but I don't believe there has ever been a LEED bridge project. So take it easy on the LEED bashing. But I get where you're coming from with the lib's :thumbsup:


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## TimNJ (Sep 7, 2005)

Fouthgeneration said:


> the Final product was to have cables to a tower at one end and another piece on the bedroom town side?
> 
> There is some concern the use of so much Titanium dioxide "pollution whitener" might have slowed/ lowered the rate of the concrete strength gain "enough to keep the bridge white for 100 years with out painting..."
> 
> ...




Probably non-union contractor cutting corners. You know, the ones that claim they can do a job cheaper than a union contractor.
Makes as much sense as your liberal tree hugger comments.


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## jlhaslip (Dec 31, 2009)

Someone's nutz will be in a wringer, and they ain't mine. Some Engineer will be back to sweeping floors.

Sad about the deaths and injuries.


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## Fouthgeneration (Jan 7, 2014)

The bridge is just a part of parking ramp and other smaller projects rolled into one large Tax dollar eating burrito, Might of conflated "sustainability" silly Meme for the silly LEED Memes....:jester: IM not so HO Spending $ to save dimes of energy is crazy dumb. 

Building owners will cold chiseling the LEED Platinum Awards plaques off their building walls to raise their resale value 10 years from now. 

I don't think anything in S. Florida is Union labor start to finish other then Medical care? or Lawyers?

This is a massive engineering boo-boo with an weak in concrete structural theory project manager that didn't know enough to say " hey, wait a minute, what takes the place of the suspension cables tension until they are installed?..."


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## Deckhead (Dec 9, 2010)

TimNJ said:


> Probably non-union contractor cutting corners. You know, the ones that claim they can do a job cheaper than a union contractor.
> Makes as much sense as your liberal tree hugger comments.


I'm thinking you might not understand Florida too well. Unions here are a joke. Private companies are where all the talent is at in Florida.


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## RangoWA (Jun 25, 2014)

So 6 dead so far, likely more since cars are still flattened underneath. If anyone asks you to bid on an accelerated bridge project, don't walk, run.


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## greg24k (May 19, 2007)

My heart goes out to families who lost the loved ones.

How sad, 6 people dead because of some engineering load miscalculation or faulty construction.I'm sure the finger pointing already started.


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## rrk (Apr 22, 2012)

TimNJ said:


> Probably non-union contractor cutting corners. You know, the ones that claim they can do a job cheaper than a union contractor.
> Makes as much sense as your liberal tree hugger comments.


No, because the chances of non union labor is slim and none. More than likely someone who did the testing was paid off


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## Randy Bush (Mar 7, 2011)

I surely am no engineer ,but it looks like a poorly designed bridge to me. I can't even imagine the horror of being one of the people in the cars.


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## rrk (Apr 22, 2012)

It was designed by the school, 
More of the "everything works on paper" that we see all too much

https://nypost.com/2018/03/15/bridge-that-collapsed-was-built-in-just-a-few-hours-school/


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## RangoWA (Jun 25, 2014)

I don't know if it has been done before but it was designed to be built at the side of the road and then swung into place.


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## fred54 (Dec 1, 2010)

Fouthgeneration said:


> the Final product was to have cables to a tower at one end and another piece on the bedroom town side?
> 
> There is some concern the use of so much Titanium dioxide "pollution whitener" might have slowed/ lowered the rate of the concrete strength gain "enough to keep the bridge white for 100 years with out painting..."
> 
> ...



No offense but there's a lot of stupid here in this post. A bridge collapsed and people are dead and you make it political? 

And because more kids died traveling to protests (source please?) you think it's silly to protest against being shot at school?! False equivalency much? 

Stick to construction. This is a tragedy. Somebody or lots of somebodies made some serious errors in calculation. Hard to believe something this big didn't have enough eyes on it to prevent it from happening.

Kind of similar to that building fire in the UK where all the pieces fell together after the fact.


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## cwatbay (Mar 16, 2010)

Based on what I have read so far, it appears that the failure is due to: 
Cost cutting
Avoiding inconvenience to traffic
Too much reliance on academic theory and calculations without regard to possible failure
Premature and poorly calculated installation prior to testing and inspection

That is just my best guess based on news reports and witness statements. And, of course, the fact that it fell apart.


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## MarkJames (Nov 25, 2012)

My buddy has been a bridge inspector for many years, and just retired from that gig. He's a no-nonsense type, who basically said it's too early to tell what happened, but they'll be sure to get to the bottom of it (design and materials, etc.) so it's not repeated and lessons are learned.


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## MarkJames (Nov 25, 2012)

cwatbay said:


> Based on what I have read so far, it appears that the failure is due to:
> Cost cutting
> Avoiding inconvenience to traffic
> Too much reliance on academic theory and calculations without regard to possible failure
> ...


:laughing: I think there's more rigor involved, but stuff still happens in life. We'll see.


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## rrk (Apr 22, 2012)

I just read this morning that the tension cables were loose and they were being tightened when the collapse occurred. Why would they do that with traffic going under it?


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## RangoWA (Jun 25, 2014)

fred54 said:


> No offense but there's a lot of stupid here in this post. A bridge collapsed and people are dead and you make it political?
> 
> And because more kids died traveling to protests (source please?) you think it's silly to protest against being shot at school?! False equivalency much?
> .


But you are criticizing making a political statement with one of your own. The kids are being used, they only know what they've been told. Guns were always around and didn't become evil beings somewhere along the way and it's the entire focus.


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## tipitop (Dec 3, 2013)

RangoWA said:


> So 6 dead so far, likely more since cars are still flattened underneath. If anyone asks you to bid on an accelerated bridge project, don't walk, run.


After battle we all are generals.


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## tipitop (Dec 3, 2013)

greg24k said:


> My heart goes out to families who lost the loved ones.
> 
> How sad, 6 people dead because of some engineering load miscalculation or faulty construction.I'm sure the finger pointing already started.


Just to aware you they did try something new. Just like that skyscraper in Sf that is build at floating footings and is sinking now.
Second to aware you all, static is not exact science compared to for example electromagnetic. Structural engineers relies at experience and assumptions. You reed that well. Now I do not say that someone should not go in jail for this. I just say it is job as is, you call name for such job.


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## tipitop (Dec 3, 2013)

rrk said:


> It was designed by the school,
> More of the "everything works on paper" that we see all too much
> 
> https://nypost.com/2018/03/15/bridge-that-collapsed-was-built-in-just-a-few-hours-school/


"Atorod Azizinamini, chair of FIU’s Civil & Environmental Engineering Department and one of the world’s leading experts on Accelerated Bridge Construction, hailed the $14.2 million project — calling it an “outstanding example of the ABC method.”"
I guess rest of stuff that worked at structural engineering side of bridge are all Indians and Pakistani. Wonder why nobody use them in free market projects but they are everywhere in education.


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## hdavis (Feb 14, 2012)

A lot of maybes on thus one. One thing is for sure, simulating transport and installation stresses would be iffy.. There doesn't seem to be enough info to really say anything meaningful on the technical aspects.


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## Lettusbee (May 8, 2010)

Just to reiterate what has already been iterated.

Could be a good design and a crappy install. 

Could be poor design and perfect install.

We won't know for a while.


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## tang (Jan 5, 2009)

I'm sure this will be investigated and litigated for years! We will eventually find out what happened.


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## MarkJames (Nov 25, 2012)

*Stress test may have contributed to collapse of FIU pedestrian bridge*

http://www.miamiherald.com/news/local/community/miami-dade/article205422719.html

In the hours after a 950-ton pedestrian bridge over Tamiami Trail collapsed Thursday afternoon, killing at least four people, civil engineers began to speculate about potential causes.

Was it a design error? Did something go wrong during construction?

The answer may be buried deep in the calculations made by workers who were conducting a stress test on the unfinished and vulnerable bridge. Any such test, experts told the Miami Herald, requires extreme care and precision to avoid overwhelming the structure. Too much weight on the bridge or over-tightened cables could cause problems.

The firms behind the project are Miami-based MCM and Figg Bridge Group, a well-known Tallahassee design company. Miami-Dade Mayor Carlos Gimenez said that crews were conducting a stress test on the bridge Thursday, and Miami-Dade Fire Rescue confirmed two workers were on the bridge when it collapsed.


The bridge was designed to enable students at Florida International University to safely cross the busy six-lane roadway between campus and a popular residential area. It was built using a method known as “accelerated bridge construction” — an innovative way to build bridges more speedily than with traditional building methods. While support columns were constructed on both sides of Tamiami, the 175-foot span was built on the side of the road. In a matter of hours Saturday morning, the span was installed onto the columns.

The accelerated bridge construction (ABC) approach has become more common in the past 10 years, particularly in urban areas with heavy traffic, said Ralph Verrastro, a Cornell-trained engineer and principle of Naples-based Bridging Solutions.

“That’s the driver and why ABC is so popular, because it allows you to keep the road open,” he said. “It’s more expensive to do, but it gains the advantage of keeping traffic moving and that’s what makes the phone ring at the mayor’s office.”

Play Video
0:50
Aerial footage captures aftermath of FIU bridge collapse

Aerial footage shows the aftermath of the FIU pedestrian bridge collapsing on Southwest Eighth Street in Miami on March 15, 2018. Pedro Portal Miami Herald

As was the case with the FIU bridge, the structure typically is assembled from pieces placed alongside the road before being moved into place. Cables running through the bridge slab that are tightened to strengthen the pre-fabricated portions are adjusted and stress tests completed before the pieces are moved over roads, for obvious safety reasons.

If workers were adjusting cables once the bridge was in place, the cables should not have connected to the bridge’s structural integrity, Verrastro said. “Once you’re done tensioning those cables, you’re done,” he said.

It’s possible the cables were over-tightened, causing the bridge to elevate slightly in what’s called a camber. Adjusting the cables to address camber would be appropriate, but that would not impact the structural strength.

“If they were adjusting the structural cables, it was to try to put more or less camber,” he said.

Still, adjusting the camber — called tuning the bridge — can be tricky. Robert Bea, a University of California Berkeley engineer and catastrophic risk expert, has studied hundreds of structural failings including the BP Deepwater Horizon. According to Bea, when workers adjusted the camber on a bridge in Australia in the 1970s, it also collapsed.

RELATED STORIES FROM MIAMI HERALD
Families wait for news of FIU pedestrian bridge collapse victims in Miami
Families wait for news of FIU pedestrian bridge collapse victims in Miami
‘Beyond tragic’: Miami congressmen shaken by FIU bridge collapse
‘Beyond tragic’: Miami congressmen shaken by FIU bridge collapse
At least 4 dead in catastrophic FIU pedestrian bridge collapse; 9 rescued from rubble
At least 4 dead in catastrophic FIU pedestrian bridge collapse; 9 rescued from rubble
Company that designed the failed FIU bridge also designed Skyway, part of Selmon
Company that designed the failed FIU bridge also designed Skyway, part of Selmon
Crews continue working on rescuing victims of the FIU bridge collapse 
Crews continue working on rescuing victims of the FIU bridge collapse
“The steel buckled while they were attempting to tune this camber, so it’s very plausible,” he said.

Another vulnerability: the span’s weight capacity. At this stage in the accelerated timeline, bridges typically need additional temporary support; engineers must not exceed weight limits during load-bearing tests.

“The loads have to be calculated precisely in the analysis to make sure the partial bridge would be able to carry them safely,” said Amjad Aref, a researcher at University at Buffalo’s Institute of Bridge Engineering.

Because precision is key, multiple factors may have contributed to the bridge failure. The investigation, Aref said, will need to examine the construction sequence, testing, environmental conditions such as wind and other possible factors.

“It might not be one factor,” he said. “It could be a combination of things.”

The bridge also had some unusual design features.

The bridge’s superstructure was something Verrastro said he’s not seen in 42 years of designing bridges. Rather than using steel trusses, it employed heavier concrete trusses. The bridge also had a concrete roof, adding even more weight.

“This was a very long span and then they used very heavy material,” he said. “The majority of pedestrian bridges are steel.” Steel bridges are about one-tenth the weight of concrete, he said.

Play Video
0:44
FIU installs new pedestrian bridge over the Trail in a few hours

FIU installed a new pedestrian bridge over the perilous Tamiami Trail in a single morning, part of a project to provide students a safe crossing and directly connect its main campus to Sweetwater. Pedro PortalThe Miami Herald

Verrastro, an expert in accelerated construction who has spoken at FIU’s bridge engineering program, suspects that using concrete was part of the bridge’s aesthetic, rather than structural, design. The FIGG Bridge Group that designed the bridge is known for its signature bridges, he said.

“They typically get involved in ones that look fancy, but they’re competent,” he said.

Using the accelerated process doesn’t necessarily change the design, just the construction, he said. However, it does require trained contractors who specialize in the method.

In almost all bridge or building collapses, he added, construction is at fault, not design. The flattened bridge will likely remain in place, he said, while a forensic engineer conducts an investigation.

While the accelerated bridge construction process is not well known outside the engineering world, FIU has become a hub for fostering the new approach.

FIU started a center to “advance the frontier” in the field in 2010 after identifying a need for more engineers trained in the method. Since launching in 2011, the center has drawn 4,000 people to its webinars, according to the website. In 2016, it became one of just 20 accelerated building programs nationwide to receive federal funding that amounts to $10 million over five years.

The center was not formally involved in constructing the pedestrian bridge.

The center’s director, Atorod Azizinamini, recognized by the White House in 2016 as one of the world’s leading bridge engineers, said the method is safer and more efficient than conventional construction methods.

“We are able to replace or retrofit bridges without affecting traffic, while providing safety for motorists and workers who are on site,” he said in a 2016 press release about the program. “The result is more durable bridges.”

But Bea was more skeptical of too much innovation.

“Innovations always bring potential ‘failure modes’ that have not been previously experienced,” he said.


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## Easy Gibson (Dec 3, 2010)

This story sucks.

I'll avoid throwing my hat in the ring for the crappy armchair opinion contest, but I gotta wonder aloud if it's protocol to be performing ANY phase of the bridge building process with cars going under the affected area?


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## greg24k (May 19, 2007)

Easy Gibson said:


> This story sucks.
> 
> I'll avoid throwing my hat in the ring for the crappy armchair opinion contest, but I gotta wonder aloud if it's protocol to be performing ANY phase of the bridge building process with cars going under the affected area?


Exactly my thoughts, you have to be out of your mind to perform stress test with active traffic below.


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## tipitop (Dec 3, 2013)

Engineers was Figg Bridge Group. The have several hundred bridges designed. I guess it is bigger chance that MCM as GC is guilty. It is some Cuban family owned company. Time will show.


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## rrk (Apr 22, 2012)

The company had a previous bridge collapse. You would think they would be out of business after the first one.


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## blacktop (Oct 28, 2012)

It needed a center pillar . The span was too long . A temp pillar would have saved a few life's The concrete wasn't stress tested . This same company built a bridge here In va . It collapsed too. My heart goes out to those who lost life over a hack job. It just goes to show .


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## MarkJames (Nov 25, 2012)

It's looking more like the keystone cops by the hour:

https://nypost.com/2018/03/16/engineer-reported-cracks-in-bridge-2-days-before-collapse/


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## blacktop (Oct 28, 2012)

MarkJames said:


> It's looking more like the keystone cops by the hour:
> 
> https://nypost.com/2018/03/16/engineer-reported-cracks-in-bridge-2-days-before-collapse/


I heard that some cat from cali told them it was going to fail . Heads are going to roll on this deal .


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## blacktop (Oct 28, 2012)

And god forbid all the workers were Mexican. Trump will have a field day with 
That .


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## RangoWA (Jun 25, 2014)

rrk said:


> The company had a previous bridge collapse. You would think they would be out of business after the first one.


But they were the low bid and the state has better things to spend money on. Personally I would have let the college students cross the road and let Darwinian selection sort it out.


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## Bearded Wonder (Jan 21, 2011)

I’m no Engineer, and I fully acknowledge that this is just so much yacking, although I am a lifelong fan of bridges and how they’re built, and I am in construction, so there’s that.... 

Take a look at this bridge, as it was before it failed, and then as it was going to be upon completion with the cable stays. I swear I would have seen that bridge as it was and been skeptical of it. Very thin top and bottom chords, and the webbing all wonky. Obviously the webbing is intended to match the cable angle, but without the cables, it seems really iffy for that long of span and that much weight. 











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## Bearded Wonder (Jan 21, 2011)

Zoomed in view. 











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## Anti-wingnut (Mar 12, 2009)

A joke


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## Railman (Jan 19, 2008)

Leo G said:


> The smoking gun is that the bolt didn't shoot up out of the bridge because there was no tension on it. Because it had broke earlier.
> 
> That's how I understood the reason. The bolt wouldn't have been just sitting there, it would have shot out and been a distance from the bridge if it was under tension and broke.
> 
> That's the other reason why it was a snap break instead of a bending break. The bolt was already broke.


http://www.sacbee.com/news/nation-world/national/article205760454.html

After looking at the above video......
The point of failure was on the top/compression side on the last 45' angle web, not the extension/bottom. It seems to me that tightening the bolt would have made more compression on the 45' angle web that appears to be the point of failure. It appears that there was at least one worker on top when the collapse happened. It also appears that the failure was right where they were working, most likely they were tightening the bolt. The dash cam video shows one fairly clearly throwing his arms and legs out to keep his balance during the fall. You can see a white hard hat in a few frames. At one point, he tried to hang on tho the crane cable.
One of the 3 sides of that last triangle ( at crane) changed length resulting in failure. When they transported the bridge, that web was in a tension/extension load. Once the under support was removed, it was on compression load. That is the web that failed. It had 1/2 of the full bridge weight on it in compression.


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## Leo G (May 12, 2005)

They were suppose to adjust the tension when they moved it


I did see the guy falling in the car cam. Went back and forth quite a few times to see that it was a person. Bet he needed new underwear.


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## Anti-wingnut (Mar 12, 2009)

Leo G said:


> I did see the guy falling in the car cam. Went back and forth quite a few times to see that it was a person. Bet he needed new underwear.


At the least. I think this is probably the individual. All the deceased were crushed in vehicles

http://abcnews.go.com/US/worker-hurt-bridge-collapse-thinks-locking-harness-saved/story?id=53794013


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## Leo G (May 12, 2005)

Looked like the guy in the video fell to the ground, or top of the pile of concrete.


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## Anti-wingnut (Mar 12, 2009)

The article doesn't say where he was or what he landed on. I assume he was on the roof and clipped into a safety cable. The assumption on my part being that the landyard saved him from being catapulted further.

I was wrong about all the victims being motorists. The individual on the canopy roof could have been this worker, who did die.
http://www.nydailynews.com/news/nat...da-international-university-article-1.3880312


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## rustyjames (Aug 28, 2008)

RangoWA said:


> How does FOX News factor into his math?


Trump hater (joke) :whistling


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## B.Johnson (Sep 17, 2016)

RangoWA said:


> How does FOX News factor into his math?


Exactly in the same way that Obama is responsible for the collapse. But I don't see you bitching about THAT.


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## MarkJames (Nov 25, 2012)

Railman said:


> http://www.sacbee.com/news/nation-world/national/article205760454.html
> 
> After looking at the above video......
> The point of failure was on the top/compression side on the last 45' angle web, not the extension/bottom. It seems to me that tightening the bolt would have made more compression on the 45' angle web that appears to be the point of failure. It appears that there was at least one worker on top when the collapse happened. It also appears that the failure was right where they were working, most likely they were tightening the bolt. The dash cam video shows one fairly clearly throwing his arms and legs out to keep his balance during the fall. You can see a white hard hat in a few frames. At one point, he tried to hang on tho the crane cable.
> One of the 3 sides of that last triangle ( at crane) changed length resulting in failure. When they transported the bridge, that web was in a tension/extension load. Once the under support was removed, it was on compression load. That is the web that failed. It had 1/2 of the full bridge weight on it in compression.



I would say the the bottom (in tension), failed, pulling it down. And there was little in the structure at that point (future cables or whatever they're called), to keep it from doing so. And we've heard little or nothing about this concrete gusset innovation it supposedly had.


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## Windycity (Oct 3, 2015)

Anti-wingnut said:


> The article doesn't say where he was or what he landed on. I assume he was on the roof and clipped into a safety cable. The assumption on my part being that the landyard saved him from being catapulted further.
> 
> I was wrong about all the victims being motorists. The individual on the canopy roof could have been this worker, who did die.
> http://www.nydailynews.com/news/nat...da-international-university-article-1.3880312




The Chevy that you see in the pictures with the hood and doors exposed is the company vehicle that he worked at...he was probably in that truck


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## RangoWA (Jun 25, 2014)

B.Johnson said:


> Exactly in the same way that Obama is responsible for the collapse. But I don't see you bitching about THAT.


Huh? You went full retard. He didn't cause it, neither did the previous guy, many factors were in play. I do blame him for policies that crippled the recovery though. The present reality speaks to most people. Others think we can regulate and spend ourselves into prosperity.


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## Easy Gibson (Dec 3, 2010)

Guys I think we're getting good at this.

With the collective knowledge we seem to have gained from this thread alone in the past two days, I think we should open the CT Bridge Corp.
I'm sure we could do better. Hardest eyeroll.


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## KAP (Feb 19, 2011)

Easy Gibson said:


> Hardest eyeroll.


Don't think CT has an emoji for that one yet... :whistling :laughing:


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## blacktop (Oct 28, 2012)

People died . Its really nothing to joke about. From what I hear .. the lowest bidder got the job.


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## Rio (Oct 13, 2009)

I think this sums it up as good as anything else so far................


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## Leo G (May 12, 2005)

blacktop said:


> People died . Its really nothing to joke about. From what I hear .. the lowest bidder got the job.


Isn't that usually the case for the govt.


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## blacktop (Oct 28, 2012)

Leo G said:


> Isn't that usually the case for the govt.


Pretty much . This is on florida as much as it is on the bridge builder. 

They dont have inspectors in florida ? You would think on a project of that size . There would be intensive inspections .


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## Bull Trout (Dec 6, 2016)

blacktop said:


> Pretty much . This is on florida as much as it is on the bridge builder.
> 
> They dont have inspectors in florida ? You would think on a project of that size . There would be intensive inspections .



was going to make smart*$$ comment, feels like it is too soon


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## tipitop (Dec 3, 2013)

tipitop said:


> Look like mcm get jobs at affirmative action and is packed with minority women.
> https://squawker.org/culture-wars/a...pany-built-the-florida-bridge-that-collapsed/


Well when I posted it. All that girls look lie sweat harts. They would have good life like nurse or so. I do not know why they wash women brain to go to f construction. It is just bloody bs it is what that is.


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## RangoWA (Jun 25, 2014)

Sweat harts. I like that.


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## kapena (Aug 20, 2004)

RickP said:


> I've been on some jobs sites in Dade County(it's been over a decade, though) and the safety standards were not the same that I encountered in other places.
> This video is a bit long and a few f bombs, but it's worth watching and seems to have figured out what happened based on the limited evidence at his disposal.
> https://www.youtube.com/watch?v=KtiTm2dKLgU


This was worth watching, but I'm wondering if maybe it was the washers on the ends of the rod or cable that were inadequate to hold the tension instead of the rod or cable. I remember watching those documentaries showing how they would tension the support cables on bridges. The ends were always wedged against steel; not concrete. Post-tension ends on slabs or structural members usually have a large washer plate to distribute the stress. Those stupid concrete blisters where the washers were buried in did not have very much concrete to keep from blowing out and I did not notice any huge metal plate to distribute the stress and avoid a blowout of the relatively thin depth of concrete. The exposed washers in the first news report I saw was what I keyed in on. There seems to have been no real holding power for the stress involved in that design. 
It does not take an engineer to see how stupid that design was.


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## Fouthgeneration (Jan 7, 2014)

Ooops, 6 tons a foot for a WALK bridge, my bad, IT HAS benches and TABLES on the suspended part.....

Yes Virginias, it was hatched out under the Obama administration with a little Miami-Dade county Cuban legacy politics thrown in and final layer of LEED manure/ added costs with out any function..... 

Ignoring the political climate that allowed a large multi-level government project to ignore hundreds of years of bridge building experience will just allow similar PREVENTABLE failures to occur in the future, and prevent so far un- revealed unsafe structures built under the Faith based ideas of the former Progressive socialist administration. 

If the bridge was only 1200 lbs a foot would there be as many DEAD?
Two normal sized bridge cranes could have hoisted it in place in a few hours....

Why build a foot bridge 30 feet wide unless it was an emergency exit? To an arena?

This bridge design was like building a MacDonald's drive-thru on I-80 bridge span over the Mississippi River. 

Kapena: above, the post/pre stress tendons have poured in place tapered bores to "catch" the tapered wedge and nut tightener.

See:https://image.slidesharecdn.com/det...ng-for-post-tesioning-4-728.jpg?cb=1344747015

IMO there are too many functions assigned to the 'Nexus'or Node above the bridge piers... Not all the steel and PT cables could develop their rated capacity, parts of the 'confined" concrete went into a partially or completely "Unconfined" state and failed when the tensile load exceeded its capacity.

What did the Repair crew do that speed up the collapse?

Locating the drain hole for the deck in this area may have started the origin point of the failure event....


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## tipitop (Dec 3, 2013)

^^^ We have similar bridge here in s Minneapolis. It work and I never heard abut any problem with it.
http://www.americantrails.org/resources/structures/Minneapolis-Sabo-Bridge-Midtown-Greenway.html
When I said it
http://www.startribune.com/contract-to-fix-sabo-bridge-increases-to-550-000/164495406/
https://failures.wikispaces.com/Cable+Bridge+Failures+Overview
"Another example of the failures in construction period happened when an earthquake occurred during construction of Akashi-Kaikyo Bridge in Japan. The main span of this bridge which is depicted in Figure 12 was 1990 meter. At the time of the earthquake the pylons were built; and due to earth movement the main span (distance between pylons) increased about 1.3 meter; but, as the result of good cooperation between design and construction groups, construction continued to the end without any problem (Nasu et al., 1999, P312)."
Japanese are real dill at this planet as technics in question.


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## Fouthgeneration (Jan 7, 2014)

Tipitop: The Representative Sabo bridge was closed isn't it? the longer Stay cables were vibrating in 5 to 10 mph winds and breaking the connection hardware...

FYI the FIU bridge is a FAKE Cable stay bridge, the pier and faux cables(actually hollow 12" pipes) just stabilize it a little in the eventual Hurricane event....

It is a lot longer and a lot cheaper, 5.7 million$, it has only killed indirectly through longer ambulance and fire truck rides caused by roadway closures.


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## tipitop (Dec 3, 2013)

It seem to me that one real expert structural engineer for cable bridges would not have problem to charge 1000$/hour.
Sabo was closed for a few months I guess but is reopen. I admit it has problems too. But it work for now.


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## Railman (Jan 19, 2008)

An HD time lapse video of construction.
https://www.popsci.com/failed-florida-bridge-what-went-wrong


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## Anti-wingnut (Mar 12, 2009)

Fouthgeneration said:


> If the bridge was only 1200 lbs a foot would there be as many DEAD?
> Two normal sized bridge cranes could have hoisted it in place in a few hours....


But then still you would have the possibility of issues being caused by transporting the unit.

I think this is going to come down to a communication/engineering issue which was caused by the configuration of the transporters. Earlier configurations showed the transporters at about 10.75 (numbers in reference to truss numbers. It was moved with the transporters at 9.75. Trusses 9 an 11 also have no tension rods, and all of this is in the area of the presumptive intitial failure.


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## Fouthgeneration (Jan 7, 2014)

Anti-wingNut: Its is possible that transport damage from moving the support point inward was the origin point of the failure. But if so why did it not fall apart then? under the then (over) stress?

Years of studying rebar and grouting specs from hell in regards to construct-ability of masonry walls in high value public buildings has forced me to study re-enforced concrete design in self defense/ cost reduction..

I'm trying to develop a block and post stress wall system to complete with massive grouting and pre-cast tornado shelters and their ilk. Simple enough for a brickie to use and for an engineer to understand....:thumbsup: 

I am not against "pretty" structures, but I prefer ugly ones that don't kill people to pretty death rides... double that when the taxpayer's $ are spent on false to reality belief systems like LEED "design"ratings.


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## Anti-wingnut (Mar 12, 2009)

Fouthgeneration said:


> Anti-wingNut: Its is possible that transport damage from moving the support point inward was the origin point of the failure. But if so why did it not fall apart then? under the then (over) stress?


Over at welding web, it seems like the cause was too many women and a lack of men with names like Smith or Jones.


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## Fouthgeneration (Jan 7, 2014)

The Minority owned, Cuban/ Hispanic ethic "group"(don't know if it is also majority owned by a female) got a 5% margin in bidding on the Federal Job.....

I've got no issues with any split tails working or engineering, as long as they don't receive any "affirmative action" qualifications...:thumbsup:

Bad sexist joke warning: "The sorority house across the street is collapsing! What is happening? It is full of cracks....." 

You'll find surviving concrete trusses are rare as hen's teeth in the World for good reasons.


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## kapena (Aug 20, 2004)

It seems that the real mistake made by the engineers might be that they treated the incomplete assembly as if it were an actual truss capable of supporting itself without first being finished. The problem with that assumption is that the primary support against gravity was going to come from the later suspension supports coming from above. That assembly should have never been allowed to be unsupported from below until the suspension from above was fully connected.
The section diagram shows the horizontal top and bottom "chords" of this assumed "truss" as structurally keeping the angled suspension cords in place. Those chords were not meant to act as top (compression) chords or bottom (tension) chords as a normal truss would do. They were way too thin for that. It was amazing that the heavy assembly even held at that span before they blew the node connection out by putting tension on the angled suspension cord connection that was already under extreme stress.


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## Anti-wingnut (Mar 12, 2009)

The problem with your analysis is that it has been stated by the erector and the NHTSA that the cable stays were not in fact structural supports.


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## kapena (Aug 20, 2004)

Anti-wingnut said:


> The problem with your analysis is that it has been stated by the erector and the NHTSA that the cable stays were not in fact structural supports.


Such statements by the erector and the NHTSA are not very credible to me after what happened.


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## hdavis (Feb 14, 2012)

Anti-wingnut said:


> Over at welding web, it seems like the cause was too many women and a lack of men with names like Smith or Jones.



What, the weld inspections were done by women?

Hiring welders with poor quality would be a company issue, not a welder issue. Same thing with inspectors and the engineer who thought the cracks were safe.


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## TimNJ (Sep 7, 2005)

It seems the state transportation dept decided to move the support 11' over from it's original design so they could squeeze in a future traffic lane.

Required job stoppage and new engineering in the middle of the job.


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## Anti-wingnut (Mar 12, 2009)

There's some real class acts at weld web. A member or two was making a huge deal that an engineering professor or two are middle eastern, Persian and Pakistani.

Just racial nuttery like this:


tipitop said:


> "Atorod Azizinamini, chair of FIU’s Civil & Environmental Engineering Department and one of the world’s leading experts on Accelerated Bridge Construction, hailed the $14.2 million project — calling it an “outstanding example of the ABC method.”"
> I guess rest of stuff that worked at structural engineering side of bridge are all Indians and Pakistani. Wonder why nobody use them in free market projects but they are everywhere in education.


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## Railman (Jan 19, 2008)

My $.02....
The failure happened at the last diagonal behind the crane, that workers were doing said stress test on. It compressed/crushed, resulting in catastrophic failure. I did measurements on the frame by frame truck dash video, & drew out intersecting lines of the last triangle. The bottom stayed the same, & the right side of triangle stayed the same. The 45 deg diagonal got shorter from one frame to the next. You could also see the buckle appear in that diagonal, going from one frame to the next. No buckle was apparent in any other member, other than the deck buckle, which was a result of the diagonal failure. That member had aproximately 1/2 of the bridge weight on it in compression. In rough numbers basesd on 45 deg angle, that would be 1,000,000 lb x 1.41 = 141,000,000 lbs. on compression force. If that member had a fracture/crack from moving bridge, it would have made the buckle easy to happen. That spot is definitely where the attention was at.

The worker that survived the fall (apparently in black outfit) said he heard a loud snap, & quickly snapped in his harness. I believe their was another man in a white outfit, such as the engineers wore. It would make sense that an engineer would be present while a worker applied more tension to the rod. It appeared the engineer tried to latch onto the guy in the black outfit, & then separated from him. I suspect he didn't have a harness set up. If you do a frame by frame at the failure, it appears there are 2 people hunched over the last 45 diagonal end. Most likely they were applying more load to said bolt when the member buckled.
In one frame they went from kneeling, & next frame in a stand up position. Then the guy in dark outfit appeared to be reaching straight up to the boom cable, & shortly afterward he went downward. The harness appeared to fly upward. In his statement, he said he didn't remember what happened, but at the same time he remembered the snap, & latching his harness. I don't think he latched it, but instead grabbed the above cable, & the white clad engineer latched onto him. Then he lost his grip & both went down.


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## Anti-wingnut (Mar 12, 2009)

TimNJ said:


> It seems the state transportation dept decided to move the support 11' over from it's original design so they could squeeze in a future traffic lane.


That doesn't sound right. I think they moved the location of the transporters, but the length of the bridge and the fact that it was always meant to be end-supported never changed.


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## kapena (Aug 20, 2004)

Anti-wingnut said:


> That doesn't sound right. I think they moved the location of the transporters, but the length of the bridge and the fact that it was always meant to be end-supported never changed.


If that bridge was meant to be end-supported, then the joint (node) on the upper cord was where all of 1/2 of the weight of the bridge was concentrated at. Look at how thin the upper cord is. You could not get enough steel cable, rebar, or any sort of metal into that concrete to take that much weight. There is not enough meat in that concrete and that is where the bridge began to collapse as others have pointed out. That bridge was meant to be held up by suspension supports, regardless of what the engineers say to cover their stupidity. The end chord is aimed toward the eventual support column for a reason, not for decoration.


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## Anti-wingnut (Mar 12, 2009)

We'll see. I don't see how they are covering themselves with statements.


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## kapena (Aug 20, 2004)

Anti-wingnut said:


> We'll see. I don't see how they are covering themselves with statements.


You are right that they claim it is a truss bridge, but they seem to be making stuff up when they call it a truss.

A truss is usually a lightened form of a steel I-beam or an engineered wood beam made up of opposing parts that increase the vertical plane where the strength comes from. The horizontal flanges on a steel or wood beam keep the vertical web strong by stiffening it. The flanges also add strength with the top flange being in compression and the bottom flange being in tension if there is no camber in it etc.
What I'm pointing out is that there is no real web in that so-called truss-bridge. If you cut out most of the web in a steel I beam, it would lose a lot of strength. That is why holes drilled into any joist, beam, etc are not supposed to exceed certain sizes or locations (1/3 in middle) without adding some reinforcing. I would like the engineer to point out where the web of that bridge is. It is not a truss without a good-sized vertical member top and bottom. All I see are some angled chords and a top and bottom flange. That ain't no truss in my book.


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## Bearded Wonder (Jan 21, 2011)

Anti-wingnut said:


> The problem with your analysis is that it has been stated by the erector and the NHTSA that the cable stays were not in fact structural supports.




That seems ridiculous. They were going to put up the planned 150 tall pylon or tower with all the cables connecting to the bridge, and coincidentally the webbing in the bridge was angled to line up with the cables, even though it was all unnecessary? I find that unbelievable. 


Sent from my iPhone using Tapatalk Pro


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## kapena (Aug 20, 2004)

It occurs to me that there probably was a lot of extra potential energy, besides the bridge's excessive weight, in the bottom or possibly even the top chord, that added to and caused the final failure we saw. If the tension cables in the over-stressed bottom walkway were beginning to level out of the needed upward camber, they may have suddenly hit the point of no return and reversed what they were supposed to prevent as they began to flex downward. The tensioning of that end chord may have ruptured the already over-stressed bridge walkway, which would then make that thing go down the way a combined mousetrap, flyswatter, and bowstring would. There was more than gravity dropping that bridge from the speed which it went down.


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## hdavis (Feb 14, 2012)

kapena said:


> You are right that they claim it is a truss bridge, but they seem to be making stuff up when they call it a truss.
> 
> A truss is usually a lightened form of a steel I-beam or an engineered wood beam made up of opposing parts that increase the vertical plane where the strength comes from. The horizontal flanges on a steel or wood beam keep the vertical web strong by stiffening it. The flanges also add strength with the top flange being in compression and the bottom flange being in tension if there is no camber in it etc.
> What I'm pointing out is that there is no real web in that so-called truss-bridge. If you cut out most of the web in a steel I beam, it would lose a lot of strength. That is why holes drilled into any joist, beam, etc are not supposed to exceed certain sizes or locations (1/3 in middle) without adding some reinforcing. I would like the engineer to point out where the web of that bridge is. It is not a truss without a good-sized vertical member top and bottom. All I see are some angled chords and a top and bottom flange. That ain't no truss in my book.


Trusses don't generally have webs.


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## Rio (Oct 13, 2009)

Here's a basic truss and its components. Regarding the Florida truss debacle it's a good example of the wrong principles being applied to a project. The first concern should always be safety and they obviously failed at that; The appearance is secondary but important also and they failed at that too, what a butt ugly design.

P.S. the point up the thread about redundancy is so important, it's one of the most basic design and engineering lessons. Structures should always be designed so if one part fails something else in the structure will pick it up.


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## Railman (Jan 19, 2008)

better yet...
That design was much like a Warren truss bridge. The two inverted triangles at the ends added little if any value to the design strength.

https://ojhsbridges.weebly.com/truss-bridges.html


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## blacktop (Oct 28, 2012)

Rio said:


> Here's a basic truss and its components. Regarding the Florida truss debacle it's a good example of the wrong principles being applied to a project. The first concern should always be safety and they obviously failed at that; The appearance is secondary but important also and they failed at that too, what a butt ugly design.
> 
> P.S. the point up the thread about redundancy is so important, it's one of the most basic design and engineering lessons. Structures should always be designed so if one part fails something else in the structure will pick it up.


Yeah. A wood factory crap system will hold if braced properly .


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## TimNJ (Sep 7, 2005)

Anti-wingnut said:


> That doesn't sound right. I think they moved the location of the transporters, but the length of the bridge and the fact that it was always meant to be end-supported never changed.



They didn't change the size, just where the center pole was originally placed.
I will dig through google in the morning and try to find the article.


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## Anti-wingnut (Mar 12, 2009)

TimNJ said:


> They didn't change the size, just where the center pole was originally placed.
> I will dig through google in the morning and try to find the article.


I'll be interested in what it has to say


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## TimNJ (Sep 7, 2005)

https://www.cbsnews.com/news/florid...hind-schedule-over-budget-updates-2018-03-20/


There are a couple others.

Initially saw it on Yahoo news and they had interviewed a couple bridge engineers from Duke and also from CA, though which school in CA escapes me at the moment.

Been plowing snow all morning. I will try to find the original article I saw.


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## Anti-wingnut (Mar 12, 2009)

Thanks, I'll try to digest it later


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## Leo G (May 12, 2005)

Florida bridge collapse: Design change put project behind schedule, millions over budget


And to boot a big failure that cost lives and countless dollars.

I'm betting "rushing" will be why this thing collapsed.


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## Fouthgeneration (Jan 7, 2014)

Anti-WingNut et al: the Florida Dot or Miami-Dade county wanted a future turn lane and forced the pylon north to the canal edge, thus ADDING 11' to the free span, after the majority of design analysis was thought complete for the shorter span,(~700,000$ for redesign and added work for that change order) Note the the top member height WASN'T increased to maintain the original ratios of the trusses....:sad:

The road monkeys moving the pier brought the US Army Corp of Engineers BACK into re-permitting the pier new location in the canal's (Donkey path)((i made the donkey path up))edge, Note the pier now lower strength due to missing soil abutment wasn't checked, or any footing details changed meet added loads and moment loads or even the original #s....
while this was occurring throw in a budget sequester, that kept the USACE from acting rapidly.... So running the USG out of cash does kill taxpayers....

StakeHolders were worried the TIGER $ would disappear with the new Admin, thus pushing for "quick" decision and action.....

the FIU bridge was never a tension suspended bridge, it just was a faux one because they look neat lighted up at night....Not kidding

Eng-Tips web site has useful thoughts re the collapse.

They have noted insufficient rebar to tie in the truss nodes with the decks-more "nexus" congestion problems, the long tension cables ran beside the "truss" in the deck and "roof deck" not directly above or below, creating a need for transfer "beams/rebar' that appears not to present in sufficient amounts. 

Kapena: I love your sticking to a magical world view, does it have Unicorns and strawberry fields forever?:thumbsup:


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## kapena (Aug 20, 2004)

Fouthgeneration said:


> Kapena: I love your sticking to a magical world view, does it have Unicorns and strawberry fields forever?:thumbsup:


I have to admit to having a wild imagination at times, but it has occasionally helped me succeed in some projects that others have warned me against even trying.
I'm too jaded to believe in Unicorns or forever strawberry fields, but I might be willing to give some free how-to advice to anyone who thought they could make such things happen.:thumbsup:


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## Railman (Jan 19, 2008)

Eng-Tips web site has useful thoughts re the collapse.

They have noted insufficient rebar to tie in the truss nodes with the decks-more "nexus" congestion problems, the long tension cables ran beside the "truss" in the deck and "roof deck" not directly above or below, creating a need for transfer "beams/rebar' that appears not to present in sufficient amounts. 

I've concluded that the bottom end of the last angle web at the bottom deck blew out. It would explain how the angles, & diagonal length changed in video from frame to frame. If you look at some of the videos of that end of the angle web after the event, it looks like it exploded. That whole end of bridge separated into separate pieces. I bet they saw cracks in area, & though that they could pull it back with increased bolt tension. As noted, that area would have had extreme loads in opposite directions while being away from main lower deck tension rods. The stated "stress test" was just a more pc way of saying that they were going to adjust tension to fix the cracks. They were more worried about public perception than public safety.


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## kapena (Aug 20, 2004)

So now we are being told that more rebar would have prevented the bridge failure. Maybe the original engineers should have first considered that concrete, as a building material, is weak in tension. The lower structural chord of that truss design must have been in extreme tension with such a long span to that bridge. To make matters worse, the designers seemed to also have not considered that concrete is a damned heavy building material, so maybe they should have not have piled on all of that unnecessary extra concrete in the roof and walkway, which increased the tension even more.


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## Leo G (May 12, 2005)

Apparently designers in name only. Maybe a bit more math homework related to gravity my benefit them.


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## Fouthgeneration (Jan 7, 2014)

One little bit of hyper Paranoia: WHY place the FIU brag pennants on the DIAGONAL trusses ???? Wouldn't 99 out of 100 people want them displayed horizontally??

My inner Paranoid thinks they were placed to cover a crack??

That is a super Wild A&* Guess, folks above, I'd love to talk to the installers of the pennants UNDER OATH.:sad::blink:


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## Railman (Jan 19, 2008)

When they moved the bridge, they added tension to the end diagonals to compensate for the change in load bearing points due to transport. Because of this, the two end diagonals were helping to keep the overloaded deck ends held together, reducing the load on the bottom deck tension rods/cables. They had just got done with de-tensioning the diagonal on the south end, & were in the process of reducing tension on the north/failure end, when I believe the deck center tension cables/bolts let go. In the video, you can see the end of the deck exploding outward, just prior to the resulting collapse. Once the bolts let go, the deck, & diagonal exploded the deck central area out the end.
I believe the intended redundancy was not going to be in place until the tower, & suspension components were in place. It was stated the the bridge would support itself without the tower, but I believe they didn't beef up the deck ends enough to distribute all the loads at the ends.
One more thing that I found puzzling was that the south end diagonal was about 2x the cross sectional area of the north #11 diagonal. The prelim. drawings didn't look that way. I'm thinking the added bridge length was compensated on that end, & resulted in a more beefy end.


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## Fouthgeneration (Jan 7, 2014)

Railman Et al: The FIU & Sweetwater bridge WAS never a stayed bridge, It was A Fake stayed bridge to look "Pretty" Something to give the FIU a little skyline flash in the swamp Flatlands of South Florida... courtesy of the USA's taxpayers.....

The 12" Hollow pipe fake stays would perhaps, reduce wind induced vibrations. The single truss being poorly dampen by itself....


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## Leo G (May 12, 2005)

:w00t:


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## Calidecks (Nov 19, 2011)

Engineers are welcomed. Engineering is absolutey science. 


Mike.
_______________


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## Leo G (May 12, 2005)

But is it contracting?


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## Easy Gibson (Dec 3, 2010)

I don't know why you wouldn't want guys like him hanging around if we let guys like me hang around.

I'm a professional, I pay the stupid bridge troll to get my stupid piece of paper and I do dumb stuff like paint basements for money... but don't we want to help expand the artform of the building trades through shared knowledge?

I feel like if his initial post is any indication that he's certainly within the "spirit" of the forum.


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## Tinstaafl (Jan 6, 2008)

Californiadecks said:


> Engineering is absolutey science.


Sorry, we don't do absolutey science here. :laughing:

This site is for guys who pick stuff up and move it. 

Doctors sign contracts. Lawyers sign contracts. No doubt your wife the educator signs contracts, as does my wife the business analyst. None of those folks fit here.


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## Calidecks (Nov 19, 2011)

What about jaws, he's a truck ass we let him in!!! 


Mike.
_______________


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## blacktop (Oct 28, 2012)

Californiadecks said:


> What about jaws, he's a truck ass we let him in!!!
> 
> 
> Mike.
> _______________


Ive been doing a little truck assing lately . Not a ton of coin in it . But its easy on the spine.


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## Easy Gibson (Dec 3, 2010)

Truck ass has become such a great joke/mental image for me and the guys I work with that we actually love seeing it. Gives us something to joke about the rest of the day.
"You see, it's not good to keep starting and stopping the truck all the time. Wears out the engine. It's actually better for it to keep it idling in the driveway for six hours with the air conditioning running."


Anyways, I thought the guy made a solid first post which demonstrated a genuine interest in the building trades and he produced original content, which is the holy grail of the internet.
If it ever were to come to a vote, I'd vote let him stay.


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## Leo G (May 12, 2005)

It's not a popularity contest.


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## tipitop (Dec 3, 2013)

Californiadecks said:


> Engineers are welcomed. Engineering is absolutey science.
> 
> 
> Mike.
> _______________


No structural engineering is not. It is more guessing science. Srs you can google it. We have structural laws but they are guessing laws. You remember Millenium tower. They guess it will hold, footing didn't hold.


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## Calidecks (Nov 19, 2011)

tipitop said:


> No structural engineering is not. It is more guessing science. Srs you can google it. We have structural laws but they are guessing laws. You remember Millenium tower. They guess it will hold, footing didn't hold.




I agree there are bad engineers. That why they carry malpractice insurance like doctors. 


Mike.
_______________


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## Fouthgeneration (Jan 7, 2014)

IF you sell something, with a "contract" aren't you a "Contractor"?

Thus a consulting (licensed?) P>(rofessional = paid performer)E.(ngineer) or S.E. /Structural Engineer.

Full time teaching Engineer not a contractor....except with the college.....
Retired Eng. not a contractor....


Engineer in Training for A structural engineering firm that designs to contracts.....????

If you do something that speeds the plow of a building being constructed, to a written or verbal contract: you are a "contractor" IMHO.

Accountants, tax people, inspectors, deliverymen, supply chain, waste management, solid and semi-liquid....eeuh! design, labor, finishes, floors, roofs.......windows and doors, holes and walls, plumbing and electrical...

I can't build a large scaffold with an enclosure with out an Engineer's approval of the design....

Engineers sucked over 10% (1,200,000$) out that bridge that lasted 5 days in SweetWater Florida. Now that is contracting.


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## Railman (Jan 19, 2008)

Final approved plans for construction from fdot :

https://cdn2.fdot.gov/fiu/13-Denney-Pate-signed-and-sealed-FIU-bridge-construction-plans.pdf


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## Railman (Jan 19, 2008)

From Leo....
"I can explain it to you, but I can't understand it for you."





I've already shown what happened, & I will now attempt to explain it....again.

It's about being between a rock, & a hard place......
#12 was the rock solid connection to deck, & #11 diagonal was the hard place. The short fillet block fillet was what stood between, & what ultimately failed.

#11 was 24 x 21 = 504 sq inch cross sectional area, at aprox 4,000psi load.

The fillet block that connected #11 to #12 was aprox 10 x 20 = 240 sq inches. at 2.1 x 4000 = 8000psi load.

Potentially the fillet block, is over 2.1 x the psi of #11.

If the bottom of #11, without fillet, was to travel .024" (.024"= 7 paper printer sheets), it would apply 8000 psi to the short fillet block. Becasue #11 to deck was a concrete construction joint, it would be normal for movement while the rebar took up a portion of the load. 
So, in other words, .024" travel transfers 8000 psi to fillet block. Concrete fails at the rate .003"/inch, so .024" #11 travel = fillet failure.

In order for the fillet to be downsized to 1/2 #11, you would have to assume that the engineers figured that 1/2 of #11 energy would be transfered to the deck, WITHOUT MOVEMENT ACROSS DECK. I also have to wonder if they considered the block to be on a horizontal plane, & hence subject to the resulting horizontal force vector of the truss. If so, that was also a mistake. It doesn't become a horizontal force until it transfers to deck.
Again, here is what it would have looked like:


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## Railman (Jan 19, 2008)

Said #11 to #12 fillet connection.


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## Railman (Jan 19, 2008)

Here's the crack pict I was looking for. It would have allowed #11 to slide toward #12 needed amount for the fillet to explode. There are 3 different cracks in pict, so it may have been more complicated than I previously posted. In previous post I should'd have reduced force by about 25%, but that is still a very high psi on fillet.


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## hdavis (Feb 14, 2012)

If the concrete didn't cure in tension, the steel would have had to deform to keep the crack open, unless I'm missing something.


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## Railman (Jan 19, 2008)

Preliminary report...
https://www.ntsb.gov/investigations/AccidentReports/Reports/HWY18MH009-prelim.pdf


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## Leo G (May 12, 2005)

Sure is preliminary


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## Fouthgeneration (Jan 7, 2014)

The blueprints(Plans for the youngsters/BIM) show only ONE set of confinement stirrups while I believe three sets are needed due to the three different directions the the concrete at the "nodes"/nexuses required 3 sets of confinement steel(carbon fiber or basalt might have been spec near salt water...).

Thus when all three tension vectors are combined, the design fails as the max load/difference/shear is exceeded..... :wacko:

There was NOT enough steel rebar nor was the deck thick enough ( The ~16" thicken portion under the cross webs, which were 21" wide by 24" deep ( so the rebar box was only 17" wide by 20", with 2 or 4, 3.25" diameter post stress conduit tubes(many as yet ungrouted)) was further comprised with the ~ 9" deep recess to "Hide" the deck drain rain horizontal pipe.

The decision early on to hang the bridge from the structural components to reduce the elevator and stairway costs & lengths indirectly lead to the embedding the 8" drain pipe(it would have drained 30' x 185' of walkway) another straw(9" deep notch, 185' long) on this broken camel's back , note the center drain design reduced concrete thickness at the center line WHERE IT WAS needed the most.....
Add the 9,25" x 9.5" square deck drain opening less then 24" from the nexuses providing one MORE crack starting local ON EVERY ONE. to transfer the loads of the cross beams to the decks post tension cable, the concrete went into a tension mode and cracked apart.

Swiss cheese has fewer holes then the joints of this bridge did.

If the bottom joints had "tumors" of thicken concrete to distribute the stresses like the one added to the roof deck to attach the faux cable piping, the bridge might of went years before collapsing...

Furthermore, the silly angling of the cross beams to match the fake tension pipes, unnecessarily created a non-symmetrical loads which weakened and added costs, and appears to never have been checked design wise....

Mathematically constant angle cross webs would be MUCH simpler to model accurately....and avoid residual side thrusts with the least amount of material.... Form didn't follow function here.

What is the story behind the white coating? the Titanium Dioxide doped concrete didn't yield a white enough surface?:blink:

Railman @ 176:

Your picture shows the coating clearly. That crack starts at an unnecessary 90 degree stress riser built into the form work.... I'm thinking there is Zero steel bars bent around that inside angle..... 
The truly scary part of that crack is the horizontal leg that appears to show the concrete has 100% separated at the deck level...
The bridge is already broken: No one has yet the balls to say so.

The accompanying photos show two cracks that parallel one of the PST cable conduits.

Just the fact the collapse was nearly instantaneous, points to brittle concrete in tension failure = inadequate steel load paths


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## Railman (Jan 19, 2008)

Her is a link to some circa 1937 patents by Ulrich Finsterwalde ( Nazi Germany) on concrete truss design. In it, he talks about how the node areas don't work well in concrete....not nearly as well as steel. One of the most striking things that I see, is that he isolated the truss webs from the nodes. They came together at 90 deg abutments. 
Many modern concrete designs go out of their way to control how and where concrete cracks. The FIU bridge didn't seem to do that in the truss structure. 

https://patents.google.com/patent/US2151267A/en


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## Railman (Jan 19, 2008)

For what it's worth, I told you so...


https://www.ntsb.gov/investigations/AccidentReports/Reports/SPC2002.pdf


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## Leo G (May 12, 2005)

Can you pull out some conclusions? Copy and paste them.


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## hdavis (Feb 14, 2012)

The bridge span in this area already had extensive concrete
cracking that had progressed signiicantly in the several
days before this work was performed. These
cracks were a clear indication that the structure’s
intended load-resisting mechanisms were
failing. The engineer of record (EOR), who worked for FIGG
Bridge Engineers (FIGG), stated later that the PT rods in
member 11 were being retensioned to return the bridge to a
“pre-existing condition.”
But there was no way that this severely cracked bridge
could be returned to a pre-existing condition through
retensioning—the severity of these cracks indicated that
the steel reinforcement was already yielding or fracturing
and the concrete had lost some structural strength.
Although intended to be a remedial action that would
return the bridge to a previous state, retensioning the
rods located within member 11 increased demand on,
and damage to, the member 11/12 nodal region until the
distress became critical.


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## hdavis (Feb 14, 2012)

IIRC, this is what Railman said at the time. I know we discussed that exact part in detail.


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## Leo G (May 12, 2005)




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## Railman (Jan 19, 2008)

The pictures of the cracks just prior to failure discussed at meetings just before collapse are devastating. Look at them in report. Basically the engineers said it was not a concern.
From the video, I concluded the point of failure, & what happened in succession. The one point of the conclusion that I would contest is that the report shows 11/12 just sliding off the end. The video showed otherwise. The node exploded & shoved 11 ( diag member) into 12 (the end pillar). The reason I know that it happened that way is that prior to 11 moving, there was an expulsion of debris on the end of the deck. That was the 11/12 node exploding while they were trying to pull cracked node areas back into original position. There was a hesitation at this time before #12 to deck connection failed. Then 11 collided with 12 vertical splitting 11 down the middle, & knife edging the #12 column before shoving it off the deck. Basically, the node failed 1st, not #12 column.

The node size, & amount of steel was insufficient. The cold joint to the deck was a contributing factor, by putting all the shear on just 4.5sq inches of steel. There was also a mention of several vertical drain pipes in the area that lessened the shear area. Bad design, major calculation mistakes, bad execution = disaster.

This all happened right before I went through lymphoma battle. In my shop office my dry erase board drawing of node failure is still there from right after collapse. My boys thought I was nuts!


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## AustinDB (Sep 11, 2006)

Because of the errors in FIGG’s design calculations, the total amount of reinforcing steel needed was underestimated. Only a 4.8-square-inch, cross-sectional area of reinforcing steel was resisting the northward shear force pushing the bridge deck. An additional 13-square-inch cross-sectional area of reinforcing steel in the interface shear reinforcement area should have been provided.

reinforcing steel was too small and additionally the to-be built second half of the bridge would have offered some countering force. 

looking at the pictures of damaged concrete looks looks similar to the Surfside collapse


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## rrk (Apr 22, 2012)

There is a entire engineer forum just for that bridge collapse and another for the Surfside collapse. You read some of the posts and wonder how in the world did they not think the clear evidence was important. And who had the authority to say "its not a problem, continue on"?


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