Miami Pedestrian Bridge, Part X 50

[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

Part IX
thread815-451175



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[MikeW7]

Portion of roadway was in fact closed during PT operation.

The road remained completely blocked off after the move, until the PT was done and the big yellow crane was removed.

This is the time frame where Kevin Hanson freaked out when he saw the "gaping cracks" and sent pictures to his boss. Hanson's crew worked on the North blister first, then the south blister, so his boss had plenty of time to make some phone calls and get higher-ups involved before traffic was reopened. The MCM on-site trailer was less than a block away. The SPMTs were still warm. Hindsight is 20/20....

 

[Vance Wiley]

When exposed to sunlight, the titanium dioxide in the concrete captures pollutants and turns it bright white, reducing maintenance costs.

So this bridge is an air filter? And students and people are supposed to walk on and brush / lean against a surface especially created to "capture pollutants"? Has anyone done a health study to determine how far away one should stay from these "pollutants" on these surfaces? Will the pollutants wear off the deck surface and embed themselves in your shoes? This could be the beginning of an asbestos-like court action. Potential mothers will say it caused infertility.
I read about this additive in the proposal.
Any chemical analysis of the concrete to establish the TD content? Is a titanium doped pollutant more or less toxic? I have images of Miami lawyers on late night tv.
Why paint the diagonal web members if they are going to turn white all by themselves?
They sold this thing with images of lounging students in hammocks, music, gatherings - - did Linda Figg term it "10,000 square feet of assembly area"?
"Nothing like the smell of" 8 lanes of exhaust fumes "in the " early evening.

 

[jrs_87]

MikeW7 (Electrical)14 Jun 19 04:14
Quote (jrs_87)
Portion of roadway was in fact closed during PT operation.

Mike, I meant the day of collapse, west bound travel was blocked by crane. But since you brought it up... Your timelapse of move day - which of course is speedup - appears to be move span, de-stress, Slam-Bam-Thank-You-Ma’m, we are out of here. And then all of a sudden you see traffic under lonely bridge in the dark. They ready could not leave roadway closed until Monday?

Someone should check how long does it take to loosen 4 bars 50 kips at a time, although I have high confidence Hanson's crew did indeed do their part correctly.

 

[jrs_87]

"Nothing like the smell of" 8 lanes of exhaust fumes "in the " early evening.

Not to mention what the air over Tamiami Canal might smell like in the summer.

Prepare to be grossed out:

https://www.tcpalm.com/story/news/l...2018/07/03/moving-water-south-goal/755309002/

 

[MikeW7]

They sold this thing with images of lounging students in hammocks, music, gatherings

FIGG didn't "sell" anything. They gave FIU was it asked for.

For some reason FIU seems to be getting a pass so far, but this ugly, over-built monstrosity was a direct result of their egotistical desires. From the TIGER Grant Request for Proposal (PDF):

OWNER's INTENT (page 1): The OWNER seeks America’s best designers and builders as members of a design-build team to design and build an innovative signature bridge that will become a respected and valued design landmark in Miami. It will serve as the critical element of a pedestrian-oriented shared-use corridor between FIU and Sweetwater, igniting the development of UniversityCity. We envision a wide pedestrian bridge (20’ minimum width to perhaps even more than 30’) that would serve not only as a means to cross from one side to the other, but would become a destination in its own right where community members might linger, gather, and create an urban social space --a linear park. We expect that the bridge might even be used as an event venue. For those reasons, it should be equipped with furniture, shading, protection from the elements, and state of the art safety features such as LED lighting, video surveillance and emergency call boxes.We envision a wide pedestrian bridge (20’ minimum width to perhaps even more than 30’) that would serve not only as a means to cross from one side to the other, but would become a destination in its own right where community members might linger, gather, and create an urban social space --a linear park. We expect that the bridge might even be used as an event venue. For those reasons, it should be equipped with furniture, shading, protection from the elements, and state of the art safety features such as LED lighting, video surveillance and emergency call boxes.​

INNOVATION (Page 2) A balance must be achieved between the desire for innovative design and the realities of proven operating and maintenance practices. A commitment to innovation and design excellence as well as to durability, ease of maintenance, and material innovation are encouraged​

The Miami Herald also published a lengthy story about the evolution of the bridge's design complexity at FIU's request, including a requirement for ABC construction, well before MCM-FIGG got involved.

I'm not trying to deflect from MCM-FIGG's poor choices and sloppy design, I'm just noting that a lot of what they did was trying to satisfy the "customer is always right" mantra. MCM-FIGG's biggest mistake in this whole mess was not having the balls to say "Nope" and walk away from their crazy customer.

 

[MikeW7]

Mike, I meant the day of collapse...

My mistake.... But my response was spot on. There were serious warning signs going up the chain of command while the roadway was still closed, and people ended up dead because nobody in the chain thought it was important enough to pause for a few hours and see what was going on. I worked in a steel mill (sheet finishing) for 22 years and one of the first thing you're taught when you move up to an operator position is don't be afraid to push the E-Stop because it will almost always produce a better result (less damage, etc.) than if you do nothing.

 

[Vance Wiley]

biggest mistake in this whole mess was not having the balls to say "Nope" and walk away from their crazy customer.

Sounds a bit like my comment "Faced with these obstacles, I recommend refusing the project."
of 12 Jun 19 07:50, although I was a little less direct. I like your approach. Sometimes the best projects are the ones we don't get to do.
You and I would have avoided the headaches of this project, Mike.
In the phrase "They sold this thing . . . " I intended a broad reference. And I fully agree with you - FIU wanted this project bigtime. That is a long shopping list FIU prepared - the "be-all to end-all" project. The hype was beyond real.

 

[Vance Wiley]

Please read the complaint filed by a victims family.

I am surprised they did not name the peer review firm as a defendant - and FIU - although FIU did forfeit their claim on FIGG's insurance policy so that may exclude them.

 

[jrs_87]

MikeW7, Your story about FIU getting a pass... It's like the dysfunctional relationship between patients and plastic surgeons. There is always a surgeon willing to risk botching a procedure for a wacko patient. I want triple D's and a 30 foot wide deck.

Don't forget about Sweetwater. If you listen to audio recording you will find selection committee complaining about their struggle to get bidders. They end up pleased to get two, and then - dejection as they learn one bid is non-responsive and does not count. So this project was awarded to only bidder. How was that allowed by grant? The ability to attract multiple bids is a strong indicator of feasibility.

http://panthernow.com

is a good source of contemporaneous forensic information. BTW, how many posters do not notice "forensic engineering" is a sub-topic this thread is under? How could they not, we have forensic-ed this topic to death.

http://panthernow.com/2018/03/04/8th-street-closing-for-bridge-construction/

http://panthernow.com/2013/08/29/fiu-anticipates-pedestrian-bridge-proposal-plan/

“[The secretary] can award part of it, all of it or none of it,” said Sauls. “We have had two tries, and we’re trying for the third time. Each time it gets better and we’ve been encouraged to continue the effort.”
This project has been in the plans since 2010. If the proposal is approved, the project will begin fall 2014.
Sauls said, [highlight #FCE94F]“We’re pushing the envelope. This is a world’s ahead agenda.”[/highlight]
​

http://panthernow.com/2016/03/01/fiu-to-build-bridge-over-sw-8th-street/

... The construction also includes a [highlight #FCE94F]concrete canopy that is 30 feet wide and overall[/highlight], “enough width to allow for the comfortable passage of bikes and pedestrians as well as a space for special events and student seating,” according to FIU News.
​

What?! They wanted the canopy 30 feet wide as well? (Elsewhere FIU is quoted as settling for 16, due to cost, and weather is mostly good anyway).

http://panthernow.com/2016/02/22/new-bridge-to-benefit-student-pedestrians/

“We wanted it to be from the very beginning a signature bridge, because we could’ve easily put in a [highlight #FCE94F]box bridge…just to get across[/highlight]. We wanted it to be a continuation of the City of Sweetwater and FIU,” said Jessell. “I’m pretty excited about it.”​

 

[jrs_87]

FINALLY, the first and only voice of reason questioning this project contemporaneously during it's planning stage. She calls BS on it and easily states her points.

Watch the first student in the top video on this page. Did the school not like her statements and called for the disclaimer? I don't know, but I have not come across another article at Panther Now with such a disclaimer.

http://panthernow.com/2016/03/01/fiu-to-build-bridge-over-sw-8th-street/

 

[stevenal]

Did the school not like her statements and called for the disclaimer? I don't know, but I have not come across another article at Panther Now with such a disclaimer.

7 pages of search results

 

[jrs_87]

stevenal (Electrical)14 Jun 19 15:27

7 pages of search results

Noted, thank you for correcting record. My post was imprecise and asserted invalid conjecture.

Panther Now
184 results (see stevenal's post)
"Posted by", 1340 results (enter this in google search: "POSTED BY" siteanthernow.com)

So they disclaimed 184 of 1340. Roughly 14 percent by this metric.

 

[MikeW7]

There is always a surgeon willing to risk botching a procedure for a wacko patient.

The huge, immense difference is that plastic surgeons NEED to continue doing ego-based surgery because it brings in MORE of their core customers: desperate insecure people. Large constuction outfits like MCM and FIGG should have a self-preserving obligation to AVOID risky projects because their core customer group wants to avoid litigation over "ugly" or possibly dangerous structures.

 

[hpaircraft]

I wonder who'll play him in the movie?

Well, William H. Macy did great in his role as the clueless husband whose wife bribed a college admissions department...

 

[jrs_87]

Again, as this site's moderator admonished me for doing last time, I have directed this forum into the weeds.

 

[jrs_87]

This thread is helping me understand the 11/12 joint. I'm finally starting to get it.

https://www.eng-tips.com/viewthread.cfm?qid=122089

Two simple but excellent standout posts in this thread:

JAE (Structural)25 Apr 05 11:45

Is this correct? - I would say no - the shear friction method is all about the friction between two surfaces of concrete - dependent on the roughness of the concrete. The shear friction works due to the ability of the reinforcing to hold the surfaces together and this engages the rough edges such that slippage is minimized.

So the concrete works in shear, the reinforcing works in tension. Shear capacity of dowels are not involved.
​

cap4000 (Civil/Environmental)25 Apr 05 13:24

Just to add to JAEs excellent response. If you have 2 separate pours, the first pour should have a "rake-roughen joint surface" at 1/4 inch amplitudes per ACI 11.7.9. The ACI premise I believe is that for the concrete to actually slide in shear and move over the 1/4 inch high points the rebar will immediately go into TENSION not shear. The typical 2x4 or 2x6 footing key everybody uses may not be technically as good as the ACI roughen condition. ACI 11.7.5 limits the concrete shear portion of the Vn, above that rebar is required. Dowel shear capacity a moot point.​

Any comments? Note, I understand dowel effect is not relevant.

 

[Brian Malone]

I had to go look for the term I was alluding to earlier: groupthink . . . The phenomena has been described and the effects are often documented in hindsight. Link
Possibly, the attendees of the meeting onsite the morning of the collapse just got pulled into an unrecognized condition of groupthink. The confidence and authority of the FIGG presentation, along with each group's hope for a successful outcome for resolving the cracks and indications of failure of the bridge, allowed the obvious not to be recognized or spoken. From some of the earlier posts I get an understanding that this bridge though unconventional, probably could have succeeded with the proper attention given to rebar placement and sizing, the order of the construction (back span and pylon first, then put in the ABC main span), better design of the drainage sleeves and proper sizing of diagonal #11, etc. The bridge failure appears to be not just one root cause but the culmination of many faults, missteps and missed opportunities for correction.

 

[Vance Wiley]

This thread is helping me understand the 11/12 joint.

A comment - after all, you asked. I have used the shear -friction concept for a career. No problems. But I see it as most useful in flanges to girders and such. Continuous walls - few retaining walls will have a shear of 1300 kips from a slice of soil every 1'-9" along the wall (I chose 1'-9" because that is the width of member 11 and its shear contact with the deck).

The concept of shear-friction can be used wherever you can draw a line (plane) where shear might develop basically parallel to that drawn plane. At the face of a column with a cip corbel, for instance. But in that case (cip) a factor of 1.4 is used. Intentionally roughened (1/4") a factor of 1, and as cast (even finished or formed?) the factor is 0.7. They say this is confirmed by testing. Concrete to steel is also 0.7. Using numbers like that for a condition like this truss is scary - I recommend reaching into the bucket for a lot of redundancy. With the mating of two basically smooth surfaces just how much axial strain can be developed in reinforcing steel? Large bars need a lot of development length - or half length and a 90 bend. I find it questionable that that yield strain in the reinforcing will maintain contact sufficient for a friction factor of 0.7. (That should garner me some comments). But I do not write codes nor do I conduct lab tests. And varying points of view stimulate debate and conversations, I hope.
As to the 11/12/deck joint, there was a plane that can be identified thru the failed zone almost parallel to the slope of member 11, and that pretty much describes the failure in the OSHA pics 62,62,64.
Because the #7 hoops across the deck plane sheared, they had about 80 kips to contribute until they failed, then nothing across the deck remained except some friction from the normal force (the flat joint had slipped days before the collapse). It appears the deck plane held until passing the #9 bar at the top interior face of the diaphragm, then began to slope down along the incline of 11, until it joined the 8" pipe sleeve. The width of the failing block increased until reaching the highly compressed regions of the D1 PT strands. Note on the west side (Rt in the pic) the coils that contain the bursting pressures under the PT anchors. It appears the breakout continued in a diagonal widening like in diagonal tension. And no diagonal tension reinforcing to help.
I read the divot in the cold joint at the bottom PT anchor and stub as having been pryed up as the PT ripped from the bottom of 11. If that idea has merit, the cold joint was basically flat all the way to the #9 bar, where the shearing turns down and begins widening and developing diagonal tension, eventually daylighting out the end.
Getting back to the action of an intentionally roughened cold joint, I have some difficulty with a "raked joint". I would rather see a ribbed area formed with cured surfaces if we want to assume a 45 degree slope and a subsequent development of tension in reinforcing across the plane. I question at what point in a "slide" does the raked concrete crumble and effectively lubricate the joint? It has probably already failed at that point, I suppose.
For forces in the order of those on 11, I would have investigated a formed an integral well reinforced and well anchored bulkhead/block cast with the deck, with a joint face perpendicular to the axis of 11. And added plenty of confinement reinforcing at all joints. But then I would not be doing this project.
In addition, I think there may be issues with the aggregate strength at this level of stress (8500 psi). The splitting tensile strength could be critical and might affect joints and shear-friction.
And there was mention of changing suppliers of the concrete - was there time to test the new product? (28 day test?). Was the reinforcing well cleaned or replaced, and where was the concrete removed?
Just a comment - -
Thanks.

 

[jrs_87]

Vance Wiley (Structural)15 Jun 19 08:32

Thank you very much. I will study your post carefully...

Tomfh (Structural)15 Jun 19 09:12

Thank you, very well put. Looking forward now to design of replacement bridge. I expect they will get one out of a catalog this time.

https://www.bigrbridge.com/solutions/prefabricated-bridges/pedestrian-bridges-truss-styles/

 

[MikeW7]

This may explain why the bridge became "too big to fail": PantherNow 2017-09-05:

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