Pedestrian bridge collapses at FIU

[VeloClone]

This looks like some sort of major flaw in the installation plan. They just put this section into place last Saturday. Now judging from the model there are supposed to be suspension cables to support the entire structure but those weren't in yet. So it appears they removed all the supports holding it up so traffic could continue on Monday leaving that long span to just support itself.

https://news.fiu.edu/2018/03/first-of-its-kind-pedestrian-bridge-swings-into-place/120385

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That is if the suspension part was really structural and not ornamental. The skyway bridge over 1st Ave. in Minneapolis between Target Center and Mayo Clinic Square (Block E) has a giant suspension component built on top of it but it is entirely ornamental and does nothing to hold the span up.

 

[mj4cy]

It was still going to be a cable stayed bridge in its final state. You can see the cable connection points on top.

Oh okay. Then it was still under construction and the big news was that it was just put in place. I was under the impression it was finished.

One big thing with structures sometimes is how to support it until it can support itself. I design formwork all the time for Iowa DOT slab bridges until the concrete cures. You'd think this was done properly in this case, but maybe not.

Like most cases, best to wait 24 hours before pointing fingers.

 

[ArgentCy]

Helps to have video. One of my co-workers did some quick thinking just after the I-35 collapse and grabbed and saved the footage of the collapse that had been captured by our security cams.

The loud cracking sounds that the person reported and the worker hearing should have set off alarms and shut down the area. Of course don't know just how close or time was between that and the collapse.

 

[BoxsterCy]

Woof. If that is true and "crack" was something like the pre tensioning cables or similar in that truss snapping then they had some warning and someone didn't act.

 

[CtownCyclone]

Like most cases, best to wait 24 hours before pointing fingers.

This is 2018. Finger pointing and wild speculation begins even before a disaster occurs.

 

[Doc]

That is if the suspension part was really structural and not ornamental. The skyway bridge over 1st Ave. in Minneapolis between Target Center and Mayo Clinic Square (Block E) has a giant suspension component built on top of it but it is entirely ornamental and does nothing to hold the span up. I guess unless it was posttensioned.

It’s been a long time since I took statics, but on this one you can see that the truss looks like a legit box truss whereas the FIU one doesn’t look stable. There's nowhere for loads to go anywhere but the deck from what I've seen.

 

[DeftOne]

Looks like the time-lapse video I linked to on the first page of this thread of the main span move has been removed from YouTube. Figg Engineering and MCM's (contractor) website are also "down".

 

[CyArob]

There is a time lapse video. I posted it on the first page of this thread.

Ah, they must have taken it down pretty quick. shows as unavailable for me.

 

[ArgentCy]

Oops, gotta take down any evidence for cleaning. Or just standard OP when a lawsuit is likely incoming.

 

[mj4cy]

Oops, gotta take down any evidence for cleaning. Or just standard OP when a lawsuit is likely incoming.

There will definitely be a lawsuit. With Florida, a lot of projects are fast tracked and design build. It's likely both the designer/installer will be involved.

 

[ArgentCy]

Oh I'm sure the lawyers will get a hold of it and add everyone under the sun. They have perfected that business.

 

[throwittoblythe]

As an engineer myself, I agree it's way too early to speculate as to the cause. However, what we do know is that the bridge collapsed before it was open and, as far as I can tell, they weren't experiencing any extreme weather events at the time. It's pretty startling to me to see that it collapsed without ever experiencing load other than it's own self-weight and a few construction materials.

I was part of an engineering failure on a project early in my career. I learned there that it's never one thing, it's always a combination of several things that cause a failure like this.

 

[LincolnWay187]

I know this is a new bridge..but as an aside...I was really hoping during the recession in 2008 they would do some major infrastructure on old bridges and stuff, especially after Minneapolis. No idea where all the stimulus money went.. Did any engineers here see any infrastructure spending from that bill?

 

[BoxsterCy]

I know this is a new bridge..but as an aside...I was really hoping during the recession in 2008 they would do some major infrastructure on old bridges and stuff, especially after Minneapolis. No idea where all the stimulus money went.. Did any engineers here see any infrastructure spending from that bill?

The stimulus funding was short term with stipulations it needed to be spent "now". Lots of it went to easy "shovel ready" projects, paving etc, not to big projects like all new bridges and highways with longer lead time for design and construction. Infrastructure was part of the "stimulus" and benefited some short term but the stimulus was never really an "infrastructure" bill.

 

[HighOnCy]

Civil/structural engineer here in road & bridge construction. You all would be mortified to see what you are driving over everyday with older infrastructure. However, new construction with modern technology for design and building techniques, it is pretty inexecuseable to have a flaw of this magnitude.

 

[Die4Cy]

I saw it reported that the new bridge was undergoing a stress test at the time of the collapse. Yes, with cars on the freeway.

I can't find that tweet now, it's possible it was taken down if there wasn't proper corroboration.

 

[jdoggivjc]

Prime example of why sometimes taking the lowest bid is a bad idea.

I work for the Federal government for a living. Through experience, I can confirm that taking the lowest bid is almost always a bad idea.

 

[jdoggivjc]

Civil/structural engineer here in road & bridge construction. You all would be mortified to see what you are driving over everyday with older infrastructure. However, new construction with modern technology for design and building techniques, it is pretty inexecuseable to have a flaw of this magnitude.

I drive on roads in Michigan. It takes a lot to mortify me. We have potholes so big here rebar is exposed in many places.

 

[xr4ticlone]

With suspension/post tensioned bridges of that nature....the game these days is to maximize efficiency and push things to the limits. So if the design or construction is a little off, it can cause a domino affect.

We're now engineering and designing a world that's 'just good enough'...

I HATE that...it's not 'just enough' it's junk.

 

[xr4ticlone]

From the article...

The 174-foot, 950-ton section of the bridge was built adjacent to Southwest Eight Street using Accelerated Bridge Construction (ABC) methods, which are being advanced at FIU’s Accelerated Bridge Construction University Transportation Center (ABC-UTC). This method of construction reduces potential risks to workers, commuters and pedestrians and minimizes traffic interruptions. The main span of the FIU-Sweetwater UniversityCity Bridge was installed in a few hours with limited disruption to traffic over this weekend.

Also...not a good advertisement for FIU's engineering school.