Miami Pedestrian Bridge, Part VI 31

[JohnRBaker]

Not sure if anyone has noted this before, but our friend Juan Browne (AKA Blancolirio), of Oroville Dam fame, has also started to post a series of videos covering the bridge failure. Now he won't be giving us aerial views of the bridge from 'The Mighty Luscombe' but he is providing commentary and opinions.

Anyway, here's the first of those videos and from this link you should be able to find the rest is you wish to:

https://www.youtube.com/watch?v=sBDDQLcp6iI

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

 

[epoxybot]

dik - Legal quagmire indeed but FIU signed a Local Agency Agreement with FDOT, essentially taking on the responsibilities of being a Transportation Dept, while also having control of permitting (Building Dept) & being the "Owner/Purchaser" and possibly Project Management organization.

 

[dik]

but FIU signed a Local Agency Agreement with FDOT,

I suspect that if the FDOT was actively involved with the project, as government agencies tend to be, that they are in for a pile of heartburn, agreement or not. If FIU was taking over, the FDOT had no place on the site.

Dik

 

[chris snyder]

We'd been discussing what might have caused the collapse, but the tragedy was the loss of life. I'm curious if all responsibility will fall on the one person (Denney Pate) who said the cracks weren't a safety concern.

From the Tony Pipitone radio interview:
"A.Z.: It certainly was a tragic error. We don't know why that decision was made to keep the road open, right?
T.P.: We don't, but we do know about accelerated bridge construction, which is what this technology is being highlighted there. FIU is a national leader in it. One of the big selling points is that you only have to close the road for the positioning of the bridge - sometimes only one day. In this case, it was about two days. So, it's a point of pride for these people that they don't have to close the road. There's a reluctance to close the road because it's not called for. But clearly it was called for in this case, and whether that came into play in the decision-making, I don't know. But it was determined it wasn't a safety issue."

There was pressure/pride to keep the road open. When this first happened, people (FIU, FDOT, etc) were quick to say closing the road wasn’t their responsibility. Someone (FDOT?) said the permit for a road closure was there for the asking. I think about the worker bees (like myself) who might have thought it would be been good to stop traffic, but just did what they were told.

 

[dik]

I hope the judge has his 'bullsh*t baffle' on...

Allen's letter notes that making the information public will cause people to 'clam up' and destroy evidence. Allen thinks that by announcing that several federal agencies are looking at charges as well as the Florida cops that everyone will become more talkative and will freely present all the evidence they can locate.

Some days you just have to shake the sawdust out from between your ears...

Dik

 

[dik]

I'm curious if all responsibility will fall on the one person (Denney Pate) who said the cracks weren't a safety concern.

We have no idea of what the cracking was... no one has come forth with photos or any information from the meeting about the cracks. We don't even know if cracks were discussed. If they were anything to be a concern, Pate, could be criminally negligent or worse.

Dik

 

[dik]

ABC... Always Be Careful?

Dik

 

[dik]

Jaun Brown made a comment about tensioning the web members would affect the camber; I'm not familiar with concrete trusses that are post-tensioned. Is this correct? I would have thought that it would have minimal effect.

Dik

 

[Retiredat46]

I don't think they're actually looking to bring criminal charges against anyone, but they're just being very careful in the way they're conducting the investigation so that anything they find can be used in court if warranted. It would be a real shame to find wrongdoing and not be able to prosecute because of a sloppy investigation. You only get one chance to get it right the first time.

 

[hokie66]

dik,
I don't think anyone is "familiar with concrete trusses that are post-tensioned".

Back to the peer review. They should be able to release that, as just like the construction drawings, the peer review was certainly completed prior to February 19, if it was done at all.

 

[TheGreenLama]

dik,
If you look at it as a beam, the horizontal component of force of the PT in the web would create a couple about the c.g. of the cross-section. This in turn would generate a moment and impact camber.

 

[dik]

I don't think they're actually looking to bring criminal charges against anyone

That's not the impression his letter left with me.

 

[dik]

Concrete truss bridges:

https://www.google.com/search?q=con...meAKHQFVDUsQ_AUICigB&biw=967&bih=602&dpr=3.16

don't know if any are post tensioned...

Dik

 

[dik]

Don't know why it attaches files like it does...

Dik

 

[Sparweb]

dik,
Please forgive my ignorance of bridge structures, but, to my eyes, most of the bridges seen in the links using those search terms look like steel bridges with stucco or some other "cladding". Some of them even have steel neighbours visible in the backgrounds, rivets and all...
Rue Denis Lecoq, Liege, Belgium for an example, the McMillin Bridge in Pierce Count WA for another.
I can't see how those bridges could work without a lot of steel hiding inside.

As for your PDF file. That is the only behaviour you can expect when uploading a PDF file to the Engineering.com server and including it in your post. I was able to access the file from the first try and your second. PDF's are not "pictures" that can be displayed like JPG, GIF, and PNG image files. They can only be opened by Adobe Acrobat and the associated plug-ins in some browsers, and Adobe wants it that way. If you'd like more assistance with image/document/file uploads, don't hesitate to ask.

STF

 

[hokie66]

SparWeb,

You are correct, most of those bridges linked by dik are steel. There is one concrete footbridge in Austria, trusses each side, which is interesting architecturally. And there is one now abandoned footbridge in California, which is really an arch bridge. Concrete trusses are rare, for good reasons.

 

[Ingenuity]

...post-tensioned truss bridge from Australia that I previously posted in Miami Bridge Collapse Part III (or maybe IV) - The Rip Bridge, north of Sydney:

Cantilever of 240' each side of the Rip crossing, that supports a 120' drop-in central-span. Constructed in the late [EDIT] mid 1970's.

 

[hokie66]

Thanks, Ingenuity. I have driven across that bridge at Ettalong a few times, but didn't realise how it was built.

https://www.youtube.com/watch?v=xpnutgevVS8

 

[dik]

most of the bridges seen in the links using those search terms look like steel bridges

It's used and I've seen a couple... my preference is steel... I like ductility without cracking.

Dik

 

[dik]

If you'd like more assistance with image/document/file uploads, don't hesitate to ask.

Thanks for the offer. The website or my browser didn't give me an alternative method other than I can copy the URL and paste it into the reply. I converted the pdf to a png hoping to just paste the image into the reply but after waiting 5 minutes for the png to load, I gave up.

Dik