Stress test may have contributed to collapse of FIU pedestrian bridge

Miami Herald ^ | 15 March 2018 | By Jenny Staletovich, Rene Rodriguez And Joey Flechas

[JohnBovenmyer]

Since instead of a bridge they ended up building a wall across the road, which will stay there until the forensic engineering inspection is done, that traffic interruption clause just maxed out. Meanwhile the FIU admin honchos, who were pushing over the edge engineering on a mere Ped Bridge, to produce a bragworthy landmark for their engineering school - who cares what it costs, we’ll get Obamabucks - got the rep they deserved. Next we’ll learn whether anyone in FL will give them the Rap (sheet) they deserve.

[Liz]

Oops......wrong thread....I wondered where it went.

[JohnBovenmyer]

Like the eco retrofit that burned down the London high rise recently, green lemmings.

[EVO X]

Just about every over pass I see on highways and local roads have steel beams. Why the need for a cable stayed bridge for this; what should have been a mundane pedestrian footbridge? Oh, the Feds are on the hook, let’s splurge ?

According to one of the articles I've read they went with concrete to reduce vibrations. Evidently it was going to more than an overhead walkway. They were going to have benches and WI-FI access points so students could hangout.

[jetson]

Sounds like a problem with pre tightening and post tightening in relation to moving the bridge around. Sounds like they may have cracked it during moving.

[4yearlurker]

I used to do construction and one mantra was "if you don't start out right,you don't end up right." This whole idea was a disaster from the get go.

[meatloaf]

Concrete works great with compression loads. It fails easily under tension. The design most likely incorporated cables in the bottom of the beam/bridge that could be tightened to place the bottom of the beam/bridge in compression. I suspect the cables were tightened after the concrete cured and reached a specific strength. The tightening was calculated to allow the beam/bridge to be moved onto the piers. Then additional tensioning was applied to enable the bride to support additional loads other than the dead weight. During that process something got out of sync and the load exceeded what the concrete could withstand.

[T-Bird45]

With VT in your screenname, I think you probably have a handle on this that’s not evident in other responses. Few people understand the post-tension concept. I first worked a building with post-tension concrete in 1987. Since then, it has made its way even into home construction as I have PT cables in the slab of my house that was constructed in 2008.

[nickedknack]

Actually, I *am* an engineer, and that is what should have been done, traffic disruption or contact financial penalty be damned.

[The_Media_never_lie]

The bridge should have been strong enough to handle a full load of drunken college students, jumping up and down to see what happens.

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Where could you find enough drunken college students who could jump up and down in unison?

[BRL]

Somewhere there exists an engineer who said don’t do this. He is soon to be fired

[who knows what evil?]

Stick to home ec,honey...no one dies.

[pas]

Trumps tariffs caused this. They could not afford steel so went with concrete. /s

[The_Media_never_lie]

Maybe the schools stopped teaching about empirical dead white guy engineering

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Dead white guy engineering sent dead white guys to the moon, a feat that has not been repeated repeated in many years. It is also known as slide rule engineering.

[Haddit]

Thanks Sherlterguy, you know exactly what I’m talking about. I used to get in trouble at my parties because all the guys were in the garage building or fixing something.

[DuncanWaring]

Spring Break?

[Godebert]

One would think there would some cctv footage of the bridge collapsing, particularly if “stress testing” was being conducted and FDOT officials were present at the time of the collapse.

[Robert A Cook PE]

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.

Obama’s democrat government, spending democrat money, by democrat politicians in a democrat-controlled city in a democrat congressional district? “We don't need no stinkin’ engineers!”

[markoman]

I did see some cctv footage at DailyMail.com

Marko

[frog in a pot]

Agree the odds favor your #15 analysis.

It seems clear the erection schedule provided for the structure to be in place prior to installation of the mid-span column and support cables - without support at the bottom in order to facilitate auto traffic. Ergo, the design team had calculated the structure could span the gap with its dead load. One would suppose the structure could have been substantially post-tensioned while yet on the ground once the fabrication process was completed.

OTOH, what are the odds this was a Hyatt walkway type of failure?