Miami Pedestrian Bridge, Part I 65

[JohnRBaker]

Multiple Fatalities After Pedestrian Bridge Collapses Near Florida International University

https://www.nbcmiami.com/news/local...orida-International-University-476984523.html

As investigators continue to search the site of a deadly collapse involving a 950-ton pedestrian bridge near Florida International University in Miami Thursday, officials say the death toll has risen.

Early Friday morning, the Miami-Dade Police Department confirmed that six people have died as a result of the collapse....

John R. Baker, P.E. (ret)
EX-Product 'Evangelist'
Irvine, CA
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[bridgebuster]

I just read this article, which cites previous safety violations against Figg and MCM.

Link

 

[minerlax4]

structuralengr89, I think it was likely #11. On page 115 of that pdf, it shows the tendon arrangement for the panel point on the opposite end. If you mirror that, the #11 tendon, assuming #11 has tendons, would protrude in the spot that matches the tendon in the photos with the jack attached. It also appears to be pointing toward the end bent in the photos. I agree it makes no sense to be tensioning #11 when it's already under compression. Maybe you're right and it is #10, though. That would make the failure more difficult to explain, but would make a lot more engineering sense.

 

[dik]

Marco Rubio tweeted this last night: “The cables that suspend the #Miami bridge had loosened & the engineering firm ordered that they be tightened. They were being tightened when it collapsed today.” So it seems like it was either over-tensioned and the concrete crushed or a cable snapped and the jolt lead to a failure

I read somewhere where someone heard a 'snapping or pinging' sound a few hours before the collapse.

Does not bode well if the engineering firm ordered that the strand be tightened. Also, did anyone question why the strands loosened?

Dik

 

[minerlax4]

hokie66, FDOT is already pointing fingers about the third party review in this article.

https://www.local10.com/news/florida/miami-dade/fiu-pedestrian-bridge-collapse-what-went-wrong

 

[JohnRBaker]

...while that's quite an insightful statement by Professor Petroski, I can't imagine that this particular showcase bridge in any way optimized public funds.

Please read the last sentence in my post, where I acknowledged that possibility.

John R. Baker, P.E. (ret)
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Irvine, CA
Siemens PLM:
UG/NX Museum:

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[hokie66]

I suppose there is no stopping them, but it would be nice if politicians stopped putting out misinformation.

 

[hokie66]

A rubbish article by an academic at Texas Tech. The guy is also on TV news, espousing his opinions. How do universities get sucked into hiring people like this?

He says the bridge should have had a centre support. Duh! That would have been a different bridge.

https://olivermcgee.org/fiu-bridge-collapse-why-muller-breslau-matters/

 

[Tomfh]

Were those red shoring towers removed when collapse occured?

 

[MJB315]

Here's a voice mail that the bridge engineer left notifying a stakeholder about significant cracks on the bridge.

Thought there wasn't a safety issue, although repairs were going to be needed.

https://www.google.com/amp/amp.miamiherald.com/news/local/community/miami-dade/article205627294.html

"We shape our buildings, thereafter they shape us." -WSC

 

[hokie66]

tomfh,

Yes, it was spanning full length.

 

[Tomfh]

Any possibility they tensioned this member out of sequence? Tensioning of this member should probably have waited for the cable stays..

Makes sense. Maybe they messed up the sequence, or maybe the sequence had errors meaning the strut had to carry the bridge and the stressing load - which was actually only intended to apply when the thing was hanging.

 

[Tomfh]

hokie66, FDOT is already pointing fingers about the third party review in this article

Pretty sad the way everyone bunkers down and tries to pass the buck rather than honestly appraising the situation. Reminds me of our professor's parting words: "When something goes wrong on one of your projects - and something will - the person who's fault it ends up being is the person who the blame ends up landing on."

No doubt the designer and builder will already have worked out why it's not their fault.

 

[GregLocock]

I hesitate to get involved but in some ways it is like the Shuttle O ring failure. The system didn't perform as expected. In the case of the O rings they leaked a bit on previous missions. In this case the tendons detensioned, the concrete cracked, THAT was the point at which everyone should have drawn a deep breath and start investigating. Trying to bodge it without understanding the root causes of the system's odd performance lead to this.

Cheers

Greg Locock


New here? Try reading these, they might help FAQ731-376

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[MJB315]

I wonder if the last diagonal was more flexible / compressed more than they anticipated.

Compressing more may have caused the cables to loosen and tensile forces to happen where they weren't expected (the observed cracking).

The jacking the cables down more would have just added more load in that member, croaking the connection.

To the post-tensioners in the group- does that happen?




"We shape our buildings, thereafter they shape us." -WSC

 

[racookpe1978]

Tomfh (Structural)
17 Mar 18 01:14
Were those red shoring towers removed when collapse occured?

Yes, the portable red lifting rigs were only used to move the bridge segment from its (nearby) fabrication site to the installation point. They were NOT under the bridge when it collapsed - which had a full traffic flow: 3x lanes each way.

I have driven under that location several times while down in Miami for AWS and power plant work. Sobering to know I was at that exact traffic light - waiting to be crushed later.

 

[Tomfh]

In this case the tendons detensioned, the concrete cracked, THAT was the point at which everyone should have drawn a deep breath and start investigating.

Easy to say with benefit of hindsight, but concrete cracks, tendons detension, tendons snap, anchorages fail, and getting on with things is part of life.

 

[oldrunner]

No! When the bridge started making noises and cracks - that's when you stop the traffic, get people out from under the bridge and off of the bridge and try to get some sort of shoring under the bridge before it comes down. Even if you have to call the fire department! Most fire departments have some sort of training similar to Rescue Systems I which includes rapidly installing timber shoring.

 

[OHIOMatt]

It will be interesting to follow this investigation. One aspect of the project that I hope is scrutinized is the project delivery method of design/build.

Based upon what I have read, the engineering firm and the GC have worked together on several projects. Can this type of relationship lead to questionable decisions?

I am not making accusations, but I have been part of design build teams. The pressure exists.

 

[JohnRBaker]

This was just reported by CNN:

Engineer warned of cracking on bridge two days before collapse

https://www.cnn.com/2018/03/16/us/bridge-collapse-florida/index.html

John R. Baker, P.E. (ret)
EX-Product 'Evangelist'
Irvine, CA
Siemens PLM:
UG/NX Museum:

The secret of life is not finding someone to live with
It's finding someone you can't live without

 

[Tomfh]

No!

Yes, obviously in retrospect the traffic should have been stopped, the area cordoned off etc. But no-one knew that at the time. Presumably in their minds it was some ordinary cracking and misbehaving tendons, and they made that assessment, the same assessment all sort of engineers make everyday in response to issues - including engineers on this forum.

In this case it was the wrong call, no doubt.

That's assuming the cracking was in fact related. Do we know that yet?