Miami Pedestrian Bridge, Part VI 31

[SFCharlie]

Please expect that the NTSB preliminary report will be out in a least 2 to 3 weeks.
SFCharlie

 

[dik]

I'm pretty sure they specified "doesn't fall down under its own weight"

I'm not sure that I would have included that line in a spec... but, I will in future.

Dik

 

[The Mad Spaniard]

To Dik, JRS87, JAE and SFChralie (and others)

Regarding independent review of the bridge:

This is a Designg-Build project

The "peer review" activities are not very clear in the State of Florida (Plans Preparation Manual). Because they do not specify every step on the peer review so that a truly inpependent analysis of all the elements of the bridge is done. It is open to interpretation. It is something that may have to be evaluated by FDOT.

The peer review is made usually in FL at the 60%, 90% and 100%. BUT!!!! It is potentially made "under pressure" to meet the schedule. You may have the EOR and the contractor breathing in your neck. And under these, it is potentially done very fast and without paying enough attention to details. It is an issue that needs to be resolved and clarified in the FDOT PPM. It also involves how much the "peer reviewer" is going to be paid...

We know for sure that the Structures Design Office in Tallahasse reviewed the project and provided comments. But we do not know, at what level the calculations or the plans were at that time. We have to wait and see for that report. Maybe the Miami Herald will get that in their request for documents. It should have been done before February 18 2018 and therefore obtainable.

And finally, if the shims at the pier are not directly undet members 11 and 12, OOOOPS!!! The transfer of vertical force at that node it is done thru vertical face shear friction and strut-and tie which potentially creates a horizontal force in the diaphragm (in the plane of the diaphragm) to mess up more the force situation at the node 11-12-deck-diaphragm.

Furthermore, you guys are great. I enjoy your insights.

Good hunting.

 

[jrs87]

"OOOOPS"

FIU Bridge north landing shims (repeat post from another user):

makes cracks more visable. [sic]

Okay, it's just I don't see any cracks on images from March 10 to March 14.

Retiredat46, about photos of cracks, they are from February 2018 after shoring was removed and span was dead loaded from ends and BEFORE move. If you examine the record you will find separate crack development reports after forms were removed, after shoring was removed, after PT bars and 2 and 11 were stressed, and after bridge was placed on permanent landings. Some of the reports were done by consulting firm. NTSB has locked down everything after Feb 19 2018.

I want to reexamine term "Stress test". It has been said this was misnomer, what if it was not? Perhaps the cracks lead them to test stress and strain using the PT bars. I'm grasping at straws now.

 

[dik]

jrs: [sic] thanks, corrected.

Dik

 

[bimr]

To Dik, JRS87, JAE and SFChralie (and others)

Regarding independent review of the bridge:

This is a Designg-Build project

The "peer review" activities are not very clear in the State of Florida (Plans Preparation Manual). Because they do not specify every step on the peer review so that a truly inpependent analysis of all the elements of the bridge is done. It is open to interpretation. It is something that may have to be evaluated by FDOT.

The peer review is made usually in FL at the 60%, 90% and 100%. BUT!!!! It is potentially made "under pressure" to meet the schedule. You may have the EOR and the contractor breathing in your neck. And under these, it is potentially done very fast and without paying enough attention to details. It is an issue that needs to be resolved and clarified in the FDOT PPM. It also involves how much the "peer reviewer" is going to be paid...

Each professional design firm should have a Quality Control Plan included as part of their Project Management procedures. This is not something that the State should be telling you what to do, it should be a normal part of the engineering business and of project management.

The Federal Highway Administration (FHWA) created a guidance document on QC/QA for bridge design in response to NTSB Recommendations after the catastrophic failure of the I-35W highway bridge over the Mississippi River in Minneapolis, Minnesota. The following paragraph is in that guidance document.

"For major projects involving unusual, complex, and innovative features, a peer review may be desirable to raise the level of confidence in the quality of design and construction. A peer review is generally a high-level QA review by a special panel of professionals specifically appointed by the bridge owner to meet the demands for quality and accuracy, recognizing the complexity of the design. Peer review is an effective way to improve quality and to reduce the risk of errors and omissions. The need for such peer reviews is at the discretion of the bridge owner."

fhwa

In light of this particular bridge's features including design build contract, unusual complex concrete design, supposedly innovative construction techniques, etc., a peer review would have been desirable. Don't believe any information on peer review has been released.

 

[jrs87]

"Don't believe any information on peer review has been released"

I understand Louis Berger reviewed the design. Does that count as peer review? In the future, designs will be reviewed by cloud-sourced engineering talent, so get ready.

 

[hokie66]

jrs87,
This bridge was the first, and hopefully the last, of its kind. Your suggestion that lab testing should have been done is good, but they had a full scale prototype. They could have load tested it on the ground beside the road where it was built, by using something like sand bags or water. Rather, they erected it, and it fell under its own weight. "If your foresight were as good as your hindsight, you would have a devil of a sight."

The Louis Berger review was supposed to be the project mandated peer review, but nothing about that review has been released to the public.

 

[epoxybot]

The FDOT On Thursday, the agency released a statement of “preliminary findings” suggesting that Louis Berger, the company hired by FIGG Bridge to conduct the independent peer review on the concrete construction was not pre-qualified for the work as required.
Read more here: Link

According to my reading, the FIU Bridge would have been categorized as a Major Bridge due to its complexity & truss design. The consulting criteria is here: Link

Based on the stringent Major/Concrete/Complex Bridge unique experience & number of personnel, Louis Berger may not have locally met the requirements for this particular area of design consulting.

MCM+FIGG's submittal mimics the FIU request for proposals, nearly word for word.

Just an observation of the postensioning schedule (Sheet B-69). In truss #2 the A tendon is the longer (Top) of the two, while in truss #11 "B" is the longer (Top) tendon.

 

[chris snyder]

I'm trying to understand the timeline.

From TheMadSpaniard VI 1 May 21:35 pdfs
The "FIU Pedestrian Bridge Crack Inspection" email (shows only hairline cracks) says photos are after 6 Feb 18 inspection..
"The members showing these small cracks are truss members that share the same blister at the canopy of the already stressed members No 2 (stressed 1/30/18) & No 11 (stressed 1/29/18) . We believe, this first stressing operation has temporarily created tension on members No 3 & No 10;... No other truss members within span 1 show any cracks similar to these shown on members No 3 & No 10."

The six photos of other cracks have a created date of 28 Feb 18, and (assumed? I saw no description) before the span was moved into place. These could relate to jrs87 videos showing the span supported only at the ends after all other shoring was removed.

I'm curious if PT rods for 11 and 2 were stressed while span was suspended like this.

These videos are dated 9 Mar 18 (heading at top of page) - if accurate, the span was moved the next day but someone had already seen these larger cracks. I looked at all (nice hi-res) videos - #561 gets close to bottom of #11... starts a little above the crack, pans down the span, then comes back lower, and ends just before it might show the crack.

All reports have said the cracks were noticed after the span was moved so it's odd if the photos were taken before. #11 had already moved back almost 1/16", and I'd think cracks would get worse after moving the span (jostling as it traveled, set in place, etc).

From VI 2 May 15:24

It was stated by Pate that they were going to tighten the tendons to close the crack.

Was there an article about this, or is a logical deduction? (the closest I read was ~"work was ordered by Pate to deal with something discussed at that morning's meeting")

I'm curious that the media hasn't mentioned these photos/cracks since MiamiHerald(?) noted this site in an article.

All this, and my question is does anyone know when the shoring was removed and SPMTs moved into position?

 

[jrs87]

"...mentioned these photos/cracks since MiamiHerald(?)"

No sign the media knows about other crack reports. Youtuber Construction Engineering & Photography knows. He seems to resent members of this forum, although I find him to be doing his best with what he has. Your mileage may vary.

"timeline"

A limited timeline would be a good idea. I would like us to piece one together. To start, Google street view shows formwork in August 2017.

Side note: Why do so many experts and academics think titanium oxide was mixed into 8,500 PSI concrete mix? I have trouble trusting people that fall for marketing hype. Nanoparticle titanium oxide smog scrubbing concrete indeed. I would like to see line item charge for coating.

One nice side-effect of this thread for me is that I have seen dozens of other interesting footbridges in my causal research. Some are inspiring.

Out

 

[SFCharlie]

Time Lapse FIU-Sweetwater Bridge for February 2018 - Stripping Forms, Post-Tensioning
Stuart Grant
Published on Mar 6, 2018

https://youtu.be/qBXnr0FoqA8

PG6 Camera Time Lapse FIU-Sweetwater Bridge for February 2018 - Stripping Forms - PG6 Feb 2018 1800X 1080P with Music
*Post-tensioning activities can be seen occurring over several days on the canopy in the second half of the video*
Bridge design is by Figg Bridge Engineers and it is being built by MCM.
Music is "Grasshopper" by Quincas Moreira from the YouTube Audio Library

Please also see other bridge build and move time-lapses Stuart Grant's channel.
Stuart Grant is the Facilities Planning Coordinator at Florida International University in the Miami/Fort Lauderdale Area.

https://www.linkedin.com/in/stuart-grant-7b01b214

Thanks SFCharlie

 

[Retiredat46]

FWIW, this is the very end (22/23) of #560 showing the base of #11 before the move. The progress bar hides part of the joint area for several seconds after pausing the video. I couldn't step the video frame-by-frame, so there may be more to see.

 

[dik]

The FDOT On Thursday, the agency released a statement of “preliminary findings” suggesting that Louis Berger, the company hired by FIGG Bridge to conduct the independent peer review on the concrete construction was not pre-qualified for the work as required.

That's just part of the legal quagmire coming up... If the FDOT knew Berger was not pre-qualified, and, that they should have been, and that the project was proceeding... The FDOT should have all their press releases 'screened' by their legal department, if they don't already. FDOT has to be very careful in what they release; maybe best for them not to say anything.

If they have been busy throughout the project, they may have difficulty removing themselves from it.

Dik

 

[Retiredat46]

But "not pre-qualified" does not necessarily mean "unqualified".

 

[dik]

Retired... agreed and edited.

Dik

 

[SFCharlie]

Woke up this morning to this:
NTSB confirms local, federal criminal investigation into FIU bridge collapse

http://floridapolitics.com/archives/262930-ntsb-fiu-bridge-collapse

 

[jrs87]

Actual letter from NTSB:

https://cloudup.com/cW7td9cgf3o

 

[SFCharlie]

jrs, Thank you.
SFCharlie

 

[Cutterhead]

chris snyder
"Was there an article about this, or is a logical deduction? (the closest I read was ~"work was ordered by Pate to deal with something discussed at that morning's meeting"

I can't remember exactly where I heard it, but this comes close. The issue at hand was cracks, & tightening tendons was meant to strengthen member. I know it was stated somewhere, but now I can't find.
It was repeated several times, but look at minute 12:00.

https://www.youtube.com/watch?v=8lN1hpMbMxs