Miami Pedestrian Bridge, Part IX 33

[JAE]

A continuation of our discussion of this failure. Best to read the other threads first to avoid rehashing things already discussed.

Part I
thread815-436595

Part II
thread815-436699

Part III
thread815-436802

Part IV
thread815-436924

Part V
thread815-437029

Part VI
thread815-438451

Part VII
thread815-438966

Part VIII
thread815-440072


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[MikeW7]

gwideman - If you watch the Move 4 videos the canopy crews are working at the north and south blisters, assisted by a big yellow mobile crane. After the crane is removed, street traffic resumes. Pretty easy guess that those crews did the untensioning, but I may have been assuming Hanson took the pictures AFTER the untensioning. In any case, he took them on the 10th, as reported in the article, which is the day of the move. I doubt he would have allowed the untensioning if he noticed the cracks beforehand.

 

[MikeW7]

Pate has a BS and MS in Civil Engineering from Auburn. WTF kind of Engineering Department does Auburn have that would teach a student to respond with an answer like "the EOR acknowledged that his computations could not replicate the cracks and therefore, he did not know why the cracks were occurring." I hope they yank his "Outstanding Alumni" award and ban him from ever setting foot on the campus again. JFC....

 

[gwideman]

I may have been assuming...

This question seems moot now, as the OSHA report just released contains this:

"March 10, 2018 [...] As they [VSL] began to de-stress the PT bars of diagonal 11, cracks began to appear at multiple locations, most prominently at the construction joint of diagonal 11 and the deck and at the top of the diaphragm II. There were three VSL employees performing the de-stressing – Kevin Hanson (supervisor), Navarro Brown and Chester Ashley. Kevin is regarded as one of the most knowledgeable PT field personnel in South Florida. After observing the cracks, Kevin became visibly disturbed and informed other VSL employees of the situation. Kevin took pictures of the cracks, and sent them to his supervisor, Sam Nunez, stating that “it cracked like hell”, see Figure 23. Reproduced below is Kevin’s text. Ashley mentioned to OSHA that Kevin went to MCM to show the photos of the cracks. Sam Nunez of VSL stated during an OSHA interview that the photos he received subsequent to March 10 were different, showing spalling and cracks in the diaphragm II implying that additional cracks took place after March 10, 2018.
In a March 22, 2018 interview with OSHA, MCM superintendent, Ernesto Hernandez, stated that Kevin Hanson told Pedro Cortes (MCM in charge of quality control) that cracks were appearing at the bottom of diagonal 11 after de-stressing. Mr. Cortes examined the cracks and took pictures on March 10, 2018."

 

[gwideman]

Also MikeW7, you may find the OSHA report useful in correlating your video efforts with the report's description of who the personnel were. For example, page 75: "March 15, 2018 Two structural engineers from FIGG, Denney Pate and Eddie Leon arrived at the site approximately 7:45 am to examine the cracks first by walking over the deck. Thereafter, they evaluated the cracks by using a man-lift for better access. Also present were MCM’s Rodrigo Isaza and Pedro Cortes, and BPA’s Jose Morales. Denney Pate and Pedro Cortes went up in a man-lift, and examined the cracks."

 

[jrs_87]

It appears to me grout was not given 28 days to cure before shoring was removed in casting yard. Is this typical?

 

[jrs_87]

Regrettably, the report misspells Denney as Denny twice.

 

[jrs_87]

Our conspiracy theory friend at youtube will be ecstatic his video was referred to on page 27.

 

[3DDave]

The grout offers long term corrosion and freeze-cracking control by excluding water from filling the channels. It also provides some protection if, in the long term, the anchors fail. In the short term I see no benefit to the minor section change in the grout which, installed after post-tensioning, will not be compressed.

 

[gwideman]

For those who have been following this story, and particularly the details of the #11-#12-deck area, these photos from the OSHA report finally give us a decent look at that area.
Fig 62:

Fig 63:

As a side note: Fig 63 says that #11's lower PT bar sheared. Yet I don't think that matches what we see in this picture:

...perhaps that lower PT bar was cut off on site in order to detach this large piece of evidence for transportation.

Fig 64

And for what it's worth, this should be "from north looking south", I believe.

There are numerous other photos of interest. It's well worth downloading the report and reading through it.

 

[Sym P. le]

I'm disgusted by what I read in the OHSA. If there is no criminality here I will be shocked. The structure started sagging right out of the gate and progressively deteriorated with each ensuing step in the construction process. By the time the #11 PT rods were released, the deck had twisted itself away from the 11/12/deck node. They've known all along, we didn't. How did they not have basic information about sagging from the monitoring. There should be a database revealing the progressive distortion of this nature.

 

[MikeW7]

Regrettably, the report misspells Denney as Denny twice.

I think the spelling is forever more going to be "Mud" after his quote about not knowing why the cracks were occuring.

When somebody mentioned that Figg was considering bankruptcy I couldn't figure out why because I figured they were big enough to absorb the financial repercussions, but when Figg's customers hear about Pate's "did not know why" and the company's entire "deer in the headlights" attitude during the days before the collapse they will bolt.

 

[gwideman]

(quotes me regarding Denny spelling)

Actually that was jrs_87

 

[SFCharlie]

I agree the entire document is worth the download.
Page 52
apparent cracks north end of diaphragm

SF Charlie
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[jrs_87]

Tip for those that may not know: Most PDF viewers have tool to rotate view so you may view landscape orientation pages of report without printing hard copy or turning screen.

 

[gwideman]

when Figg's customers hear about Pate's "did not know why" and the company's entire "deer in the headlights" attitude during the days before the collapse they will bolt.

Aside from clearing up a lot of heretofore ambiguity about the initial failure location, what stands out for me about the OSHA report is that it doesn't reveal any new shop drawings showing extra steel, or FIGG calculations that might have been later and better and replaced the ones we've been looking at this last month.

So while earlier this month we discussed what appeared to be really basic and conspicuous design errors more or less in plain sight, and wondered whether that could be all there is to it, the OSHA report agrees that these analyses were in fact deficient in the ways we identified.

The fact that basic analysis and design were incorrectly performed, and not caught, despite obviously silly numbers (like no rebar required in the 11-12-deck connection) is not just a mistake on this bridge. It's indicative of FIGG's process, and casts doubt not only on their future prospects, but on all their other past projects that have not yet fallen down.

 

[Vance Wiley]

gwideman - Fig 63:

At guy with tape measure - "Construction Joint" - -
WHERE ARE THE #7 HOOPS ??" There should be 4 - "Truss member 11 & 12 has 4 - ties "7S01" --
That is a clean joint - do you see any 1/4" intentional roughening?
No wonder it slid so easy.
And 11 did not "slide" all the way off cleanly. It clearly did take concrete from below the deck surface back in areas which were reinforced. But no reinforcing thru the "cold Joint" in Fig. 63.
But - how far from the face of the pier is the deck slab as it rested at the bottom of the pier? Did it break the extension of 12 off as it slid over the edge? There was an instant when the shear in the 24 x 10-1/2 extension for 12 was enormous.
EDIT: Thank you for the pictures - Big time!

 

[gwideman]

#7 hoops [...] 1/4" intentional roughening

Yeah, I don't see those hoops either, but if they sheared they might be obscured under concrete dust in this picture.

As for the roughening, that lack of such is mentioned in the OSHA report as one of the problems. But there was so much wrong with that connection it's hard to know which part to be more exercised about.

 

[MikeW7]

When you look at Figg's portfolio the thing that stands out is the immense scale of their projects. I think what did them in is they really didn't understand how to downsize their engineering, in the way that a clockmaker skilled in making grandfather clocks would be stymied trying to make a watch mechanism. Us oldtimers remember what a disaster it was when the American automakers first tried to make smaller cars - they were clueless, for years and years and years.

I don't think Figg actively sought out this contract. The owner of MCM is an FIU grad, as is 40% of their staff. My bet is that FIU approached MCM and told them they had the deal, but on the condition they had to get Figg aboard (this was a first-time MCM-Figg collaboration) so they could design one of the cool cable-stayed bridges that was at the top of the FIU wish list.

But FIU also wanted the bridge built with ABC (to enhance their engineering school brand) so the result was a compromise of the worst kind, a faux cable-stayed bridge. That would explain why Figg refused to change the design when Tom Andres asked if they had considered building "a real cable-stayed bridge" instead of a "fake one."

In the NBC Interactive Timeline - dated 10:55 Am March 25, 2016 - Andres sent an email to a Figg engineer (Jonathan Van Hook) and asked

"Just a thought. Have you guys considered a real cable stay, constructed about a pivot pier in balanced cantilever alongside the road way where the truss element and canopy were not a main load carrying members and then the completed structure rotated into place with SPMT's?​

That would (sort of) satisfy the ABC requirement, but Figg apparently refused.

If you haven't heard the entire story of the bridge's history, it's contained in this immense Miami Herald article from 2018-06-14 in the section titled Bridge Beginnings.

 

[3DDave]

I doubt that 11 took any material from the deck as much as the rebar that was part of 12 levered it out during the collapse. The prying action of 12 during the collapse would be much stronger than the loads applied by 11.

 

[TheGreenLama]

Some errors in OSHA report thus far:

P46, photos 4-6 refer to base of diagonal, not base of diaphragm.

P47, according to MikeW7 video, Move part 4 N view, PT in diagonal 11 was detensioned prior to 2.