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Miami Pedestrian Bridge, Part X
23

Miami Pedestrian Bridge, Part X

Miami Pedestrian Bridge, Part X

(OP)

RE: Miami Pedestrian Bridge, Part X



P107 of OSHA report determines shear capacity of joint as only 22% deficient. Further down, when comparing 11 with 2, they mention that they have included Member 1 & 12 reinforcement when calculating shear capacity. No where, however, do they mention specifically which bars they've included and excluded (for lack of development length). They could be a lot clearer here. I also think that it's debatable whether Member 12 steel should be included, and certainly not all Member 12 steel, as a good portion of the member lies outside of deck.

RE: Miami Pedestrian Bridge, Part X



P110. I realize they are here focused on Member 11 when pointing out the deficiencies w.r.t. shear lag between deck PT and horizontal force from diagonal. The way it's worded, however, they make it sound like shear lag concerns are gone once pylon is cast. This is obviously not the case, as Member 2 will still have these concerns.

RE: Miami Pedestrian Bridge, Part X

Just finished scanning/ reading the OSHA report. One thing I notice is that OSHA seems to confuse design review at 30%, 60% and 90% of design with design review at 30%, 60%, and 90% of construction, which is not the same thing at all.

RE: Miami Pedestrian Bridge, Part X

Quote (TheGreenLama)

re OSHA Pg 110
OSHA states the 45 degree influence of PT each side of 11/12 in the deck leaves 11/12 outside the shear lag zone so the horizontal force is not restrained by the PT.
As I recall, "40YearsExperience" was addressing exactly that in his posts, and suggested reinforcing wrapping behind 11/12 and extending into the PT compressed zones.
Member 2 at the South End has a better chance of having some more capacity - the location of PT strands and the 45 degree lines are the same as at 11, but the column member 1 is 36" and flush with the end of the deck, so we gain a foot there (12 extends past the end of the deck), then member 2 is 36" deep and at a flatter angle so we pick up maybe 2 feet there. And the drawings call for 5-#7 hoops with the chance for proper embedment above the shear plane. But a dedicated calc is the only way to know. And how much development can we count on when clipping the compressed zone of the PT ?
However, the OSHA photos of the North end diaphragm show cracking like I think Pate was addressing in his PowerPoint show, so he was right to be concerned about that. It just was not the most critical thing to address at that point in time.

RE: Miami Pedestrian Bridge, Part X


Transfer of Tensile Forces to the Deck, OSHA pg 110.
In members 2 and 11 the first PT is centered 1'-8" (+1/2") from C/L of structure. OSHA addressed the influence of this on page 110, as previously discussed.
The North span of 96 feet has the first PT at 4'-8" from C/L, meaning the end diagonals 14 and 23 are far from any PT zones. Looks like the same problem, just less load.

RE: Miami Pedestrian Bridge, Part X

Force of collapse was energetic enough to cause minor cracks on face of thick north pier.



Chipping on pier edge appears to be directly related to punch through.

RE: Miami Pedestrian Bridge, Part X

3
I have been following this thread, highly intrigued by some of the comments by those that post and in seeing how the investigation unfolded. From the first reports I saw on the bridge collapse I could tell some of the critics of the bridge design and construction (YouTube, comments sections on news sites, etc.) would point to many non-important items, such as the principal owner of the design firm, FIGG, being a woman, construction was conducted by a minority-owned business, possibly there was some corruption in the design award process, etc., etc. I was hoping as a whole the engineering community could rise above some of this but hey we are human and humans are emotional - it is the way it is.

Well, enough said on that but what I am so amazed with is the OSHA report, in my opinion, has finally pulled the gloves off and said what needed to be said:
1. The design was lacking in structural strength.
2. The design did not provide redundant load paths.
3. The EOR had plenty of information and notification the bridge section erected was showing signs of structural failure.
4. The peer review system failed not only with the CEI (Bolton, Perez and Associates) but also with the "independent" review hired by FIGG - Louis Berger. Even, FDOT and FIU should have put more engineering horsepower into their review of the plans and ongoing construction.
5. The very experienced construction team, Munilla Construction Management, on site did not strongly speak up and call an alarm.
6. Many firms, entities, professional people (with very storied and prestigious degrees and licenses) failed to step up and be "Captain Obvious"; their years of experience and expertise were not put to use when it was most important.

So, how did all this go down? Did this relatively "simple" pedestrian bridge get a quick glance over for the calculations and analysis? Hey, it is "only" a pedestrian overcrossing. Did the hope and interests of FIU to promote their ABC engineering program cause their peer review to take a back seat to getting a landmark iconic bridge - even if the design is a risky concrete truss? Isn't there a term or theory for no one willing to challenge a perceived expert or group of experts? I see this not as a lesson for pointing a finger at a villian, but as a lesson for learning to not to get lulled into complacency.

Mr. Pate, is a licensed professional engineer and the FIGG team is composed of multiple PEs; they are very skilled and their record and past designs speak to that. They are very educated and experienced.
Ms. Figg, may not be a licensed engineer, but she has an engineering degree(s) and whether she is licensed as a professional engineer is not the point. She hires very capable people to do the actual engineering, probably without micro-managing them - give 'em the project and turn 'em loose. She continues to run the company her father started; more than likely with a great sense of pride and honor.
Bolton, Perez and Associates and Louis Berger were supposed to have used their engineering expertise to check the work of Mr. Pate and his team. Did they get lulled into giving the analysis a quick glance because of the reputation of FIGG and Denney Pate? The OSHA report calls out the Louis Berger review very pointedly as being insufficient and improper for ensuring load conditions for all phases of construction were reviewed.
FIU with their academic team should have looked more closely at the plans and the ongoing situation. But somehow they coasted and only asked light questions and did not show the engineering expertise that would be expected of a center of bridge engineering. Did they let the FIGG reputation blind them? Did FDOT engineering figure this is all covered by all the aforementioned experts and they wouldn't need to look too closely?
Even the construction company with the more often "boots on the ground" view didn't step back from the project and call for a halt until the cracks and failing structure were addressed. They totally flew by the numbers given by the EOR and since none of the other reviewers objected strongly maybe MCM chose to stay mum, also.

I'm taking this as a lesson for me - though I only design desktop type analyzers. For now on, when I present my calculations and designs for review, I will strenuously ask for thorough review and comment/criticism. This bridge failure has emphasized to me, as a designer/engineer there are times you can be so invested in your design you may miss the obvious and unintentionally precipitate a disaster!

RE: Miami Pedestrian Bridge, Part X

2
Thoughts about a Prestressed Concrete Truss.
My career included some experience with prestressed concrete.
When still in college, the company I worked for designed an auto dealership in 1962 using 10 ft tees, and with parking on the roof. I did some drafting on that project. About 1966 I designed the additional floor to create a second parking level. In 1995 the School District wanted to use the building for an Adult Education Center, and I established procedures for injecting cracks, full scale load testing, and then the design to current codes for approval by The California State Division of Architect as a school. The remodel required taking down the PT in the topping slabs, creating a two story atrium with skylight, and restoring PT in the remaining sections.
We also did PT design for a small precast fabricator, and developed the necessary stressing frame and procedure for casting bonded prestressed box girders 4 ft by 84 foot length, on a riverbank.
Along the way I learned that prestressed structures are alive, and simple is the best. Strain compatibility, shear lag, walls that steal the PT forces and then crack themselves -all are problems to be addressed.
A concrete truss? I can imagine bigtime problems.
First concern is post-tensioning the deck, causing about 5/8 inch shortening in this bridge. From center out that is 5/16" at the base of 2 and 11. Neither of which really want to shorten, and so cracks develop at their connection to the deck. To minimize this, one could consider stressing the canopy concurrently, keeping the top and the bottom shortening balanced. Reducing the distance between nodes on the deck and the canopy would have caused the thing to "grow" in height, of course. And that would decrease the angles between the diagonals, with strains and possible cracking. Then there is the stressing of only the tension diagonals - how do we suppose the compression diagonals are going to react to the shortening of the stressed tension in the adjacent diagonals? Rotation at the canopy nodes, perhaps? Then there are the joints, with high compression forces under the anchor plates, sometimes crossing of PT, and the need for confinement reinforcing. Perhaps 40YearsExperience could look at this and make a recommendation, using Mohr's Circle. I am asking in earnest. There is a lot going on in these joints.
Faced with these obstacles, I recommend refusing the project.
In it's final stage, the structure will (and for a brief period did) appear simple - but that is deceptive, as has been proven.


RE: Miami Pedestrian Bridge, Part X

[quote jrs_87 Chipping on pier edge appears to be directly related to punch through. [/quote]
The chipping could possibly be due to the impact of the overhanging portion of 12 as it was dragged over the edge.
I can't see any evidence of extra shims at the center, so I guess MCM did not get to that before the collapse. It is good that they were not working on that Friday afternoon.

RE: Miami Pedestrian Bridge, Part X

2
My experience is that reviewers are lazy/without support and only spot check the math as presented, not clean-sheet the assumptions, do their own work, and then look for discrepancies. The problem is that most of the reviewers aren't given the time and budget to do that clean-sheet review, so they shortcut. Most are little better than spelling checkers, complaining about small things.

RE: Miami Pedestrian Bridge, Part X

Excerpt, page 4, NASA Systems Engineering Handbook (PDF). NASA. 2007. SP-6105

In summary, the systems engineer is skilled in the art and science of balancing organizational and technical in-teractions in complex systems. However, since the entire team is involved in the systems engineering approach, in some ways everyone is a systems engineer. Systems engineering is about tradeoffs and compromises, about generalists rather than specialists. Systems engineering is about looking at the “big picture” and not only ensuring that they get the design right (meet requirements) but that they get the right design.

Emphasis mine.

This excerpt from NASA's handbook sums up my entire motivation for visiting this thread.

https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa....

RE: Miami Pedestrian Bridge, Part X

That's SP-6105, not 610s

RE: Miami Pedestrian Bridge, Part X

Quote (Brian Malone)

Bolton, Perez and Associates and Louis Berger were supposed to have used their engineering expertise to check the work of Mr. Pate and his team. Did they get lulled into giving the analysis a quick glance because of the reputation of FIGG and Denney Pate?

When I read this it reminded me of the Boeing/FAA relationship as it relates to the MCAS problem.

RE: Miami Pedestrian Bridge, Part X

In response to Vance Wiley, it is not a small issue that the FIU bridge was a real time, real life experiment carried out on Main Street with thousands of unwitting participants invited to defy the odds by passing beneath the awesome structure. In any other circumstance, exhaustive, even destructive testing is demanded to ensure product safety before it is unleashed upon the masses.

RE: Miami Pedestrian Bridge, Part X

Why does OSHA refer to the 2014 FDOT manual setting out independent review requirements instead of the 2016 version?

Does FDOT require 30% and 60% independent review as OSHA says? Looks like 90% and 100% only to me. The 30 & 60 are FDOT reviews, on a normal project where FDOT is the client?

The FDOT requirements place a lower standard on the 'constructability' review - not intermediate construction stages - than OSHA seems to think is the FDOT intention.

In summary, I read FDOT's requirements differently than OSHA. Louis Berger probably did its job of reviewing the completed structure and we'll never know if the completed bridge would have collapsed.

RE: Miami Pedestrian Bridge, Part X

Following the OSHA report I decided to go back and look at a post I made on 31 Mar 18 when trying to summarise the whole thing with information at that time. Here is an updated version with additions in Red

Things we know we know
The Bridge fell down and killed 6 people and injured many more. Let's not forget this has affected lots of people who were in a 1 in 10 million chance of being in the wrong place at the wrong time.
The collapse happened very quickly and hence finding a root cause at this time with the limited public data available is next to impossible - Now rectified after multiple release of information
The collapse happened at the Northern end within the last bay containing members 10, 11 & 12(the end vertical member).
There was a crew working on the bridge doing something with the PT rods in member 11 - We now know they were tensioning the PT cables in an apparent attempt to close the cracks and prevent further movement.

There was a crack somewhere in the North end of the bridge
That crack wasn't deemed serious enough by the construction company to close the road underneath it. The main cracks were in the base of member 11 where it met the deck and in the diaphragm at the base of member 12. No one thought the cracks serious enough to override the opinion of the EOR that there was no safety issue.

The bridge was in structural terms a concrete span, not a cable stayed bridge (the "cables" were going to be mainly cosmetic and non supporting, but could have limited any vibration or bouncing)
The artistic design led to an asymmetrical supporting member design
The bridge was in essence a rigid concrete beam with some interesting features making analysis more complex
The second span on the North side wasn't yet installed
At some point the bridge span was lengthened and the north pier moved to allow for a future road widening
Moving the pier meant that the two transporters moved inboard from the ends ( the concept design) requiring special re-inforcement of members 2 and 11 to take account of loads seen during movement of the bridge only.

Things we know we don't know for certain
Well virtually everything else:
What the crew were actually doing at the time of collapse. See above - Now Known.
Whether the initial crack had anything to do with the collapse. Not only were the cracks growing, but it had been there since they removed all the construction supports BEFORE the bridge was moved into position.
Whether member 11 failed at the top or bottom or was just caught in collateral damage. Now very clear that the base of 11/12 punched a hole out of the base deck.
Whether the upper or lower bridge flanges failed first or broke as a result of failure of something else maybe a few milliseconds earlier. See above
What the final design was or what the design analysis showed. Now issued
Whether there was any failure in any tendons or PT rods. No failure of the rods.
Whether planned reinforcement details were altered on site and other ducts installed. This to me is still not clear. The 4" ducts adjacent to member 12 seem to be ducts for tensioning rods intended for the vertical tower structure. But when they appeared in the design is unclear.
Whether the span had been adequately analysed for its temporary condition before the second span and tower / "cables" were installed. This is still not clear. It is stated in OSHA report that the final full build would have reduced forces on the blown out joint, but it is not clear to me whether this temporary stage was properly analysed.

Things we don't yet know we don't know
Everything that has been handed to the NTSB or disclosed in testimony The OSHA report fills a lot of those gaps. In particular I didn't know that the original cracking and noise happened when they removed all the supports prior to moving the bridge.

We can speculate on these items above until the final report is written and given the probable lack of real time data, even that may never pin down 100% a single cause only one or maybe several probable causes. I think we now have a very likely cause - failure of the 11/12 connection to the base deck.
Many of the potential causes have been identified in the many many posts in parts I to V. People coming late to this post are clearly not reading through 900+ posts and so the debate has started to get very circular and mainly just rehashing old ground.

It will start again on the release of the data from the NTSB.


People are encouraged to read the earlier posts which should help answer most questions.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

RE: Miami Pedestrian Bridge, Part X

2
I hope OSHA and the NTSB get their acts together so that there are no conflicts between their respective reports.

RE: Miami Pedestrian Bridge, Part X

Quote (TheGreenLama)

I hope OSHA and the NTSB get their acts together so that there are no conflicts between their respective reports.

It would also help if they could get basic facts correct, like the order that diagonals 11 and 2 were detensioned. In today's toxic fake-news culture, a single mistake like that is enough to discredit an entire report in some people's minds.

RE: Miami Pedestrian Bridge, Part X

[quote Sym P. le] "it is not a small issue that the FIU bridge was a real time, real life experiment" - -
Very well stated. I am not sure you will consider it a compliment, but if an attorney finds your post, it will likely be used in court.
At this point in the engineering and construction technology the workings of a truss should be well enough understood to be considered common practice. The melding of that technology with brittle concrete, on a scale such as this project, then using prestressing (as I tried to describe) and the need to transport the heavy but (as it turned out) delicate structure makes this project particularly risky to all involved. Add to those real and daunting concerns the overlooking of details resulting in the deficient design of the most critical joint (which had no redundancy) and we have seen the results.
Should it have been tested full scale? You bet. When the falsework is removed from CIP work the self weight loads are present and immediately load the structure. If the transporters had remained at the end of this bridge, with PT not required in member 11, it would have likely have failed in lifting onto the transporter, or at least on the trip to its final location.
This structure was a bad idea at the outset, and received horribly deficient execution in the design, review, and construction phases. It is a poor representation of the current state of our knowledge and abilities.
Perhaps it will provide guidelines tor the ABC process. Clear guidelines or requirements for ductility, redundancy, and peer reviews with great attention given to the effects of moving a structure which is intended to serve without moving.


RE: Miami Pedestrian Bridge, Part X

Can this page help us understand failure? Did FIU bridge have block shear failure? This page is for steel, I don't know if concrete has similar page.

https://www.bgstructuralengineering.com/BGSCM14/BG...

OSHA report indicates 2 was deficient. This reinforces past concerns that collapse could have happened any time in the future, for example, with a critical load of students. Another point, by policy OSHA has zero mandate concerning safety of the public - only employees. It will be interesting to see what fines will be levied by OSHA later.

No one here has commented on OSHA's emphasis of lateral support on diaphragm II in casting yard. I think OSHA got that wrong, how could those tiny long pipes participate in load?

RE: Miami Pedestrian Bridge, Part X

Quote (jrs_87)

It will be interesting to see what fines will be levied by OSHA later.

OSHA issued some citations and fines on 2018-09-18. Links to the formal citations are included in the news release. The five companies involved are still contesting their fines. No status change in months - I check from time to time.

Will more citations be issued now that the report is out?

RE: Miami Pedestrian Bridge, Part X

More on Figg's reaction:

https://www.enr.com/articles/47044-osha-investigat...

Please read all of comment titled OSHA calculations show end diagonal truss member #11anchorage overloaded past failure by 22% and after retensioning by 45% etc. at above link.

RE: Miami Pedestrian Bridge, Part X

From FIGG's response to the OSHA Report:

In a statement to ENR, FIGG disputed OSHA’s findings, calling the report “factually inaccurate and incomplete” with “errors and flawed analyses.”

The OSHA FIU Pedestrian Bridge report “does not include an evaluation of many important factors pertinent to the construction process leading up to the accident. Additionally, it has not been reviewed by any other entities involved in the accident investigation. FIGG disagrees with the conclusions in the OSHA report.”

Um, your bridge is on the ground, bruh. Why even comment? It seems the NTSB report will likely echo the OSHA report, so they'll end up looking like fools.

RE: Miami Pedestrian Bridge, Part X

samwise753 (Structural)12 Jun 19 20:03

Legal tactic by Figg's counsel. All reports are factually inaccurate and incomplete with errors and flawed analyses if you are arguing in absolute terms.

Gaslighting:

https://thoughtcatalog.com/shahida-arabi/2016/06/2...

Side note: Louis Berger Inc. as merged with another company and made changes to board last July. Another side note: Louis Berger employees did a nice job helping build a practical footbridge in rural Panama - without heavy equipment. https://vimeo.com/294241866

RE: Miami Pedestrian Bridge, Part X

P.S. Unfortunately for the engineering profession, as pointed out, the OSHA report is indeed flawed and it would be prudent for them to amend it.

RE: Miami Pedestrian Bridge, Part X

Somewhere in there, the OSHA report mentioned that the #7 bars sheared off. (Edit: "As a result of the blow-out, three #7 shear reinforcements at the construction joint of diagonal 11 and the deck were sheared but the southernmost shear reinforcement remained intact.", Page 84.)
I agree they should amend as needed.

RE: Miami Pedestrian Bridge, Part X

I can see why an attorney would defend their client using that tactic, but it really looks dumb in light of what went down and how the aftermath is spelling out.

And it's valid that there is that flaw in the report, but that hardly invalidates its conclusions. The 12 conclusions stated in the executive summary are spot on. #12 stands out the most to me.

RE: Miami Pedestrian Bridge, Part X

Pate's call to FDOT was not a warning as widely reported. He was trying to head-off someone ELSE reporting cracks. ("...because I suspect at some point that’s gonna get to your desk...") Examine every single word of the voicemail transcript.

“Hey Tom, this is Denney Pate with FIGG Bridge Engineers. Calling to, uh, share with you some information about the FIU pedestrian bridge and some cracking that’s been observed on the north end of the span, the pylon end of that span we moved this weekend.

“Um, so, uh, we’ve taken a look at it and, uh, obviously some repairs or whatever will have to be done but from a safety perspective we don’t see that there’s any issue there so we’re not concerned about it from that perspective although obviously the cracking is not good and something’s going to have to be, ya know, done to repair that. At any rate, I wanted to chat with you about that because I suspect at some point that’s gonna get to your desk. So, uh, at any rate, call me back when you can. Thank you. Bye.”

Message contains subtle tells. "whatever", "at any rate" (twice, equivocation), "we/we've" (mouse in pocket), "chat" (no urgency), stumbles after "although", "some information" (dilutes "some cracking"), "been observed" (to distract that it's ongoing), "taken a look" (past tense again, no mention of further analysis, just repair) I'm not implying or saying he was lying, I'm looking for something else than that here.

*Source of transcript: https://www.equipmentworld.com/insurers-covering-f...

RE: Miami Pedestrian Bridge, Part X

Quote (Vance Wiley)

OSHA states the 45 degree influence of PT each side of 11/12 in the deck leaves 11/12 outside the shear lag zone so the horizontal force is not restrained by the PT.
As I recall, "40YearsExperience" was addressing exactly that in his posts, and suggested reinforcing wrapping behind 11/12 and extending into the PT compressed zones.

It think you may be referring to this informative post by SheerForceEng in thread part IV, 24 Mar 2018 22:40, responding to my questions as to whether the diagrams I sketched represented principles we would expect to see in the 11-12-deck connection, conveying the horizontal load of #11 to the deck's longitudinal PT bars.


RE: Miami Pedestrian Bridge, Part X

Skimming the OSHA report, it appears that Figg had intended to join the main span to the back span in such a way as to resist the sort of tear-out failure that caused the collapse. However, I haven't seen any signs of this plan in the materials so far released. Did I miss something? Were they going to connect something to the ends of the longitudinal PT tendons where they came through the diaphragm? I saw one passing reference to this in regards the tendons in the canopy, but if there were references to doing that with the tendons in the deck I missed them.

If this is actually the case, it might explain earlier commentary about "capturing the node." Maybe they were planning to build an appliance that they could attach to the ends of the PT tendons to simulate the presence of the back span and resist tear-out at the 11/12 node.

RE: Miami Pedestrian Bridge, Part X

Another angle. Note large size of concrete chunks.

RE: Miami Pedestrian Bridge, Part X

Quote (Vance Wiley)

[comments on OSHA report mislabeling direction of views on some photos]

The north-south swap is annoying, but probably results from confusing wording of previous view direction statements on preceding photos.

More concerning is their assertion on one of the photos that #11's lower PT bar sheared off, when photos at the scene show it attached to the deck, which is a highly important piece of evidence implicating the tensioning of this PT bar as the final factor precipitating the collapse.

RE: Miami Pedestrian Bridge, Part X

Quote (hpaircraft)

Were they going to connect something to the ends of the longitudinal PT tendons where they came through the diaphragm? [...] If this is actually the case, it might explain earlier commentary about "capturing the node."

That "capturing the node" discussion stems from the "cracks" meeting just prior to the collapse. From that meeting: "Steel channels to 10/9 node & PT Bars to capture some of that force which is better than vertical support.". So something like this:


This was deemed "better than vertical support", because just supporting near the end of bridge, does not deal with the horizontal component of #11's compression.

RE: Miami Pedestrian Bridge, Part X

Quote (gwideman)

I believe OSHA is correct. Those members were 21" wide
You are so correct - and thank you. I just embarrassed myself bigtime. And I have deleted the post and can only hope you were the only one to notice. In my defense - I was only 90 degrees disoriented, N vs S is 180 degrees. Not a lot to hold onto, but that's all I have at this time.
Thanks again.
Regarding the 45 degree shear lag and transferring the horizontal force from 11 to the PT -
I had forgotten the post you reference but I thought a similar post with "V" shaped diagonals wrapping the 11/12 node had been posted by 40YE. Now I see he has apparently removed his posts - I did a search and did not find one. I agree with the reinforcing - but it would take a lot to develop the 1300 kips (DL) and more to be safe for TL.

RE: Miami Pedestrian Bridge, Part X

Quote (hpaircraft)

it appears that Figg had intended to join the main span to the back span in such a way as to resist the sort of tear-out failure that caused the collapse
I too have trouble with that statement.
I have only seen details that anchor the concrete closure between the diaphragms to the pier cap, and a couple of PT rods down into the pier. Also some delayed placement of PT in the canopy to tie the tops together. And the casting of the 109 foot spire to support the fake "strands". Has anyone seen more ties detailed? Anything that could develop 2000 kips?

RE: Miami Pedestrian Bridge, Part X

Quote (Brian Malone)

So, how did all this go down? Did this relatively "simple" pedestrian bridge get a quick glance over for the calculations and analysis? Hey, it is only a pedestrian overcrossing. Did the hope and interests of FIU to promote their ABC engineering program cause their peer review to take a back seat to getting a landmark iconic bridge - even if the design is a risky concrete truss? Isn't there a term or theory for no one willing to challenge a perceived expert or group of experts? I see this not as a lesson for pointing a finger at a villain, but as a lesson for learning to not to get lulled into complacency.

Your entire post is spot on.

For example, while it's important for OSHA or NTSB to use alternative software to cross-check the strength of the design, I hope that one of these bodies reconstructs how FIGG performed the design. I want to understand whether the errors are as simple as discussions in Part IX of this thread suggest. Because if so, then your other points about the efficacy of all the checks and reviews etc are not about some obscure technical detail being missed, they are about how the process failed to stop even a design with problems that were about as conspicuous as possible. (And of course then failed to shut down a structure whose physical symptoms of imminent collapse were also about as conspicuous as possible.) Whatever is behind that part of the failure needs urgent attention.

RE: Miami Pedestrian Bridge, Part X

Quote (Vance Wiley)

You are so correct - and thank you.
No worries. I've deleted my comment to you as well.

RE: Miami Pedestrian Bridge, Part X

Quote (OSHA .pdf page 84)

As a result of the blow-out, three #7 shear reinforcements at the construction joint of diagonal 11 and the deck were sheared but the southernmost shear reinforcement remained intact. The width of the blow-out was 2 ft. at the southern end gradually enlarging towards the north. The blow-out encompassed the two 4” pipes on either side of column 12, and was symmetrical to the center line of the deck.
There had been some question regarding the rebar...

SF Charlie
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RE: Miami Pedestrian Bridge, Part X

It may be a little late in the game but here is my animation of the collapse based on the dash cam video. I've taken seven screen shots, rotated the images to align the orientation with the canopy section from 11 -12 and then centered them with the white figure on the #11 banner. I've attached a GIMP image file of the seven layers for better clarity of the subtle details.

I believe this shows clearly that #11 ruptured at the base (puff visible in image 2), then the canopy snapped along with the top of #11, then as #11 is pile driven into #12 evacuating a significant amount of concrete from its bottom end , #12 is pulled over and down off of its base by the canopy section which is still attached to the larger canopy by the PT bars (layer 5 and 6). I believe #11 needed to loose about 7 feet of length to straight line with the long canopy. The slab dropping from the pylon does not occur until after this sequence. This also helps to explain why the lower PT bar in #11 is kinked upward at the slab (or sheared per OSHA).

RE: Miami Pedestrian Bridge, Part X

I believe the project FDOT & FHWA standards are from 2014, based on the date of the TIGER Grant.

FDOT Tom Andres repeatedly pointed out the issue with the 11/12 node not being captured by the longitudinal PT tendons as early as the 30% Submittals Plans in March 2016 & again in the 90% Construction Plans.

FIGG did not contract for 30%, 60% & 90% PEER Review as required by FDOT. They originally tried to finagle FDOT to allow one of their OTHER FIGG offices do the PEER Review. They finally finagled FDOT to agree to PEER Review when plans were at 100% Construction ready but they used that instead to contract with Louis Berger for a 100% completed structure PEER Review instead of the still required incremental PEER Review. Louis Berger submitted the PEER Review Certifications to Alfredo Renya the FDOT LAP Coordinator, bypassing FDOT Structural Reviewer: Tom Andres. This seems a bit slippery behavior by FIGG.

During an interview with FIGG, OSHA quizzed FIGG about the lack of Redundancy. FIGGS reply was that the numerous PT bars were a form of Redundancy. Let’s hope that was Linda Figg & not Denny Pate.

FDOT’s Tom Andres was also concerned about the 12/Canopy region in front of the Canopy Blister.

What if some of the Sag in the bridge during transport remained as camber, until Truss No. 2 & Truss No. 11 are detensioned? I’m just trying to visualize the load path. At the South end (FIU) there are two bearing pads. At the North Pylon (Canal) there are 4 pedestals with stacked shim plates. It seems any longitudinal settling from SPMT move induced camber would take place to the north. So when Truss No. 2 & Truss No. 11 are detensioned, Truss No. 11 tries to kick out the base of Vertical No. 12 as the deck and canopy try to flatten out. The detensioning having a more immediate effect on the uncaptured Vertical No. 12, than on the deck & canopy.

RE: Miami Pedestrian Bridge, Part X

Sym P. le - your "dash cam video" from Joel Franco's YouTube channel is one of many fuzzy interpolated versions. Here is the highest quality version that I've found. You can clearly read the ID number on the school bus bumper: 32082. It appears to be sped up, but this is what the original footage looked like, as I explained in my post of MikeW7 (Electrical) 12 Jul 18 02:16 in Part VIII.

RE: Miami Pedestrian Bridge, Part X

Thanks Mike, I'll see if I can improve on the images. Did you check my GIMP file, the images are much clearer than the GIF. I was more interested in the overlay and reorientation of the images to see if it could give a better understanding of the collapse sequence.

RE: Miami Pedestrian Bridge, Part X

Sym P. le - I just checked your video link and saw that it was a low-quality version (fuzzy, can't make out ID number on bus bumper). The YouTube owner, JoelF (Franco), is some kind of free-lance journalist and he was sent (or obtained) one of the first copies of the dash-cam video. The original source video, as far as I can tell, was obtained directly from the truck driver by a web developer with the handle o2webdev. He posted it on his FB and IG, where some of the local media (Miami Herald, etc.) found it, and he ended up deleting all his social media accounts shortly after that. I got my shortened copy from somebody's FB before they deleted it.

The original truck dashcam video actually starts in the MCM construction area. You can see the flatbed truck being loaded by the blue mobile crane at top center starting at 2:22 in the N view collapse video, and again in the last frame of the video, at far right.

RE: Miami Pedestrian Bridge, Part X

Quote (MikeW7)

I just checked your video link and saw that it was a low-quality version (fuzzy, can't make out ID number on bus bumper).

... but most important is whether or not it's interpolated in time, as you previously pointed out. If an assessment like Sym P. le's is based on a time-interpolated version, then it's just assessing the interpolation method and model, literally the morphing method that generates the intermediate frames, not what the bridge actually did.

RE: Miami Pedestrian Bridge, Part X

MikeW7: Back in the old days of Part IX (!) you were assembling videos that focused on when personnel inspected parts of the bridge. The appearance of the OSHA report perhaps drained some of your momentum, but I wonder if you have made any observations of whether the various inspections noted in the OSHA report can be seen happening in the videos, as might be determined by approx time of day?

One episode that would be interesting to see is "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."

RE: Miami Pedestrian Bridge, Part X

Here are the individual images. They seem blurry (are soft) because the video poster cropped and magnified the video, and this is to our advantage. I'm not sure I can do much better in a short period of time.






RE: Miami Pedestrian Bridge, Part X

qwideman - I've got all the videos cut out and processed (15 total), just haven't got them uploaded yet. I will put them in a separate playlist. I found 4 separate inspections on the 12th, 3 on the 13th, and 2 closely spaced ones on the 14th which I just left as one combined video. No activity noted on the afternoon of the 10th, or on the 11th. Most of them are duplicated in N and SW views, but the N view camera malfunctioned on the 12th (visible wind buffeting and raindrops on lens). In the descriptions I'll add time-stamps (and frame numbers) for the start of each clip within the original timelapse.

RE: Miami Pedestrian Bridge, Part X

I checked the OSHA report titled: OCTOBER 10, 2012 PARKING GARAGE COLLAPSE DURING CONSTRUCTION AT MIAMI DADE COLLEGE, DORAL, FL

https://blog.newdayunderwriting.com/wp-content/upl...

It was also prepared by Mohammad Ayub, P.E., S.E., and if casually browsed is completely interchangeable with FIU report.

RE: Miami Pedestrian Bridge, Part X

Sym P. le - Attached is a 9-frame video, with individual JPGs of each frame. They are cropped to 212x203 (original video was 1280x720).
NOTE: "Zoom, enhance, zoom, enhance" only works in the movies.

UPDATE: I will try again tomorrow. The JPGs I made are distorted...

RE: Miami Pedestrian Bridge, Part X

Quote (Sym P. le)

yet another post based on bogus images

Please please read the previous forum posts about these interpolated videos. You are not analyzing evidence, you are analyzing the model used to interpolate, which means you are muddying the waters by claiming that these images tell us anything useful.

As MikeW7 pointed out 28 Mar 18 22:52, the dashcam video was capturing at 5 frames per second. And read here for how intermediate frames are interpolated, in that case by Zac Doyle:
https://zldoyle.blogspot.com/2018/03/photogrammetr...

Note in particular that the frames are interpolated (morphed) by the user manually drawing reference points. A user will generally place the points to show more or less linear motion. The user will not know if some abrupt accelerations, deccelarations, or changes of direction took place in the 200 milliseconds between video frames. The author of that blog post wrote:

"However, as I mention above, there are errors present in the rendering. One consideration you mentioned was the possibility that the motion is being linearly interpolated between the points, as in they move in a straight line from point A to point B. That is absolutely correct in regard to how the motion is interpolated in this. I could correct for a more expected curved motion for the reference points. However, its more challenging to get this correct in the short time I was spending on this."

RE: Miami Pedestrian Bridge, Part X

You may choose to disregard this, others may find it useful. Poor video is better than no video. I chose to present it in a different manner. The movements I've referred to are significant, even in terms of the limited quality of the source. The time span covered is less than 2 seconds, probably closer to 1.4. This is the smoking gun on the collapse sequence. Period.

RE: Miami Pedestrian Bridge, Part X

Quote (Sym P. le)

Poor video is better than no video.

But you are not presenting poor video. What you are presenting is fake video.

RE: Miami Pedestrian Bridge, Part X

I know a thing or two about videos and engineering. Don't be so quick to dismiss it. I could always be wrong, but maybe I'm not. I think it is far more real than you are willing to give it credit for. I'm willing to stand on this one. To be sure, I am presenting an animation, a sequence of images, sourced from a video.

RE: Miami Pedestrian Bridge, Part X

The Sym. P. le frames are fine for the purposes of this forum as long as we know the limitations.

RE: Miami Pedestrian Bridge, Part X

So Denney Pate's wife never checks pockets of pants before dumping them in the washer? Nothing suspicious there.

If they have the phone I expect it can be returned to working order. It doesn't need to go to Cellebrite first, it needs to go to iPad Rehab or similar repair company to fix whatever component made the battery angry; usually going to be something small that handles higher power rather than a SOC and memory chip.

RE: Miami Pedestrian Bridge, Part X

After spending a couple hours this morning trying to figure out how to "properly display" images I've come to the conclusion that it is darn near impossible. Anything that displays an image, be it a viewer or editor or browser, automatically processes the crap out of a small image as it is enlarged to protect you from the embarrassment of seeing square mono-colored pixels in their naked glory. As such, it is very difficult trying to illustrate how difficult it is to "zoom, enhance" a low-resolution video and expect it to provide a divine revelation.

Here's the best I could do. I took the original "high-quality" truck cam video, original format 1280x720, and used VirtualDub2 to crop out a 200x200 image at frame 70. VD2 is one of those rare applications that lets you see something resembling real square pixels in its work window. Then I took a Windows PrintScreen from my 4K monitor and pasted the capture into another of my favorite free apps, IrfanView, cropped the PrintScreen image, and saved it as a JPG with 100% quality:

The result is an 2509x2160 image that preserves most of the original 200x200 video frame chunkiness and allows you to see just how lego-like the video details really are. Note the stair-stepped diagonals.

Next I used the VD2 Rotate2 filter to spin this frame -30 degrees, and did an identical work flow to process a screen capture:

The result is a confusing, blocky mess, but this is what the real raw data looks like. It can be edited to look "cleaner" and "more realistic" but doing so severely damages the true visual data.

In closing, this isn't intended to be a criticism, just a friendly reminder that whenever you work with computers you are plugging into the Matrix, and the onscreen "reality" isn't always what it seems to be.

RE: Miami Pedestrian Bridge, Part X

I imagine it is quite the rabbit hole. Digital cameras, even our eyes, filter, distort, interpolate, extrapolate, pixelate, stabilize reality. Sometimes to the point that it becomes an existential question. I'm not trying to muddy the water for good technique, but I'm sure this stuff comes up regularly when attorneys are trying to discredit an observation.

RE: Miami Pedestrian Bridge, Part X


Quote (epoxybot)


During an interview with FIGG, OSHA quizzed FIGG about the lack of Redundancy. FIGGS reply was that the numerous PT bars were a form of Redundancy. Let’s hope that was Linda Figg & not Denny Pate.
What a deflection - Yes, the PT system has redundancy - if one strand fails there is only a small reduction in the prestress force and a small increase in loads to the remaining strands at near ultimate moments. But the PT system is not the only thing important in this structure.
I saw somewhere in the past a factor to be used if there is no redundancy, and as I recall the example, they were using maybe +3%, like divide phi by 1.03. I don't think that would have saved this structure.
What would be an appropriate redundancy factor for a bad idea? A factor of 2? So lets use two bad ideas?
A V-8 engine has 8 connecting rods - but not a redundancy of 8, because if one rod fails you walk.
Redundancy in a structure seems to mean alternate load paths. Or joints and members so well designed that they just don't fail. One intended redundancy in this case was the peer review. An alternate path to a safe design. Which, by the way, did not help much.
Redundancy in the construction phase is provided by the Project Inspectors - a redundant set of eyes.
If a redundancy factor of +10% had been used in this case, the thing might not have failed when it did. And with full consideration for loss, and very real sadness in my heart for those lost and injured in this collapse, this might have been a better time than sometime in the future when even more lives could have been lost. A better time would have been 2:00 AM with no traffic. But my point is, and I am not good at making it, no formula can compensate for a simple oversight. Engineers simply must pay attention.
To see two prominent companies go bankrupt over a small project like this does not seem right. The risk/reward ratio seems badly skewed. Sure, this project in this form should have been load tested - in fact, I submit that it should have been a research and development project with a budget of maybe $50 million. How do we get that funded? Sounds cheap, now.
So after the dust and the lawsuits have settled, what will we have learned?
Probably that the Architect was right when he told me "Never be the first to try something, and never be the last to use something."

RE: Miami Pedestrian Bridge, Part X

This article has interesting parallels to FIU bridge:

BRIDGE CONSTRUCTION: AT A HIGHER LEVEL
Elevating span in Va. creates multitude of solutions

W. DENNEY PATE, P.E., AND DWIGHT D. DEMPSEY, P.E., S.E. / NOVEMBER 02, 2012

https://www.roadsbridges.com/bridge-construction-h...

RE: Miami Pedestrian Bridge, Part X

Quote (3DDave)

So Denney Pate's wife never checks pockets of pants before dumping them in the washer? Nothing suspicious there.
Sounds like a wash being done in haste. Like maybe the pants were filled and needed an immediate washing.
(Sorry - some opportunities just can't be passed up.)

RE: Miami Pedestrian Bridge, Part X

Quote (3DDave)

So Denney Pate's wife never checks pockets of pants before dumping them in the washer? Nothing suspicious there...

I admit the timing is convenient, but FWIW, my wife of 30+ years is exactly like that. Whatever happens to be in the pockets goes right in with the clothes,
whatever it is, paychecks, phone, tools, nothing seems to get her attention. Her take on the issue- "if you don't want it washed, don't put it in the hamper".

RE: Miami Pedestrian Bridge, Part X

Hay, I've washed tv remotes, but putting them in rice worked wonders.

SF Charlie
Eng-Tips.com Forum Policies

RE: Miami Pedestrian Bridge, Part X

Whirled Gnus now has 3 PlayLists:
Bridge Timelapses
Bridge Inspections
Links
Because of the way YouTube hides unlisted items, the only way to see a playlist is to use a direct link, and the only way to see a video is to use a direct link, or select a link from Playlist.

The Bridge Inspections are video clips of the foot traffic and manlift excursions that began on the 12th. Each video description contains source video info, including the start time plus start frame of the clip within the source video.

The Links are intended to be a group link list for everyone. I tried starting a link list in an earlier forum post but found out I couldn't edit it after a few days.

RE: Miami Pedestrian Bridge, Part X

Thank you MikeW7
Now I can see the playlists...

RE: Miami Pedestrian Bridge, Part X

Thanks Mike for your work on the videos. I've tried a few different things now and conclude, barring receiving an original video (not through youtub), the images I ended up using are the best quality available. I think the poster of the video did an excellent job with the source and I picked my way through it rather well (that was determination and luck).

Moving on, with the videos you are presenting now, do they show workers on the deck at the time of the collapse, or just on the canopy?

RE: Miami Pedestrian Bridge, Part X

Quote (Sym P. le)

do they show workers on the deck at the time of the collapse, or just on the canopy?

There were a total of 6 people on the bridge. Kevin Hanson was at deck level (he's the guy wearing a lime-green shirt) and ended up being buried in rubble. He was in a coma, and is now brain damaged. 2 of the guys on the canopy were Hanson's co-workers, and one of them was killed - Navaro Brown. The other 3 guys were probably MCM workers doing the grunt work: operating the crane and manlift, helping move equipment, etc. I'm not sure if any of them have been named.

RE: Miami Pedestrian Bridge, Part X

SFCharlie - THX for the feedback. Been a long day. Had to re-upload all the Insp. vids because the first go round I posted the fast small originals instead of the slow enlarged versions. Different folder but same filenames. Grrrrrr....

RE: Miami Pedestrian Bridge, Part X

Pate designed the Varina Enon Bridge in Virginia. Here is a pony-tail wearing observer praising bridge for not cracking after 100 MPH wind storm.

https://youtu.be/nltXu1VPAlQ?t=76

RE: Miami Pedestrian Bridge, Part X

FIGG proposal to FDOT for bridge in Miami. Proposal states Linda Figg is architect (uncapitalized). (page 1/foot, page 3/PDF) I assume she did not intend to be referred to as architect (not qualified) and this was a mistake made by graphic artist.

http://www.fdotmiamidade.com/userfiles/files/Signa...

RE: Miami Pedestrian Bridge, Part X

FDOT doesn't seem to be very popular in Miami. The beautiful Figg design referenced by jrs_87 (Mechanical) 13 Jun 19 22:50 lost to an ugly spider that none of the locals liked.

RE: Miami Pedestrian Bridge, Part X

Ha - these pants weren't in the hamper, but lucky Pate, anyway.

Rice doesn't work. The problem for phones is they have a very high energy density power source -and- a need for high current density. If, as described, it's an iPhone, there is no barrier coat applied to any of the circuitry. When I mention iPad Rehab, it's because they produce videos of repairing water damaged iPhones and show exactly the damage that even a small amount of water entering the phone will do to an Apple product. Not can. Will. By the time the phone makes it to the rice, it's a goner.

RE: Miami Pedestrian Bridge, Part X

Please read the complaint filed by a victims family. https://images.law.com/contrib/content/uploads/doc...

Not that I'm smart or a lawyer, but it gives me that weird vibe that I wrote it.... I guess we all get that vibe sometime. Is there a word for it? Déjà vu is not the right word.

If anyone can post other complaints, I would appreciate it.

I checked on the four hard plastic pads mentioned in the report. High-resolution photos elsewhere show thin metal shims under all four pads. Is this typical in the industry? The pads I assume are HDPE and temporary. The purpose of this low-friction arrangement was to allow diaphragm II freedom to slide and relieve strain while chains were removed from lifter? Who checked to confirm these pads would not yield, creep, or rupture in this application? The south bearings were indeed typical and designed for bridges. The north diaphragm/pier gap was supposed to be grouted right away? And if the gap was to be grouted, how would they get the pads out first? I understand they did not grout because of delay caused by color/material mismatch. (What color was this bridge anyway? The web was sloppily brushed-over with some kind of white slurry, the rest was uncoated). All four pads can be found in post-collapse photos. Side-note: In fifty years when the south bearings are due to be replaced, the pipe stays will have to be dealt with to allow jacking of diaphragm. https://youtu.be/iFK4LTUwoAU

RE: Miami Pedestrian Bridge, Part X

Another claim: https://media.local10.com/document_dev/2018/03/29/...

Point of fact missed by almost everyone. Portion of roadway was in fact closed during PT operation. (However, this was not done for sake of safety, it was for the crane). This seems like a trivial point until your realize it was a missed opportunity to close entire roadway. Edit: It turns out they used "blanket" permission to close two lanes. Other permission was required to close all lanes. But still, needing permission is not reason to not do it anyway.

RE: Miami Pedestrian Bridge, Part X

Quote (jrs_87)

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....

RE: Miami Pedestrian Bridge, Part X

Quote (MikeW7)

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.

RE: Miami Pedestrian Bridge, Part X

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.

RE: Miami Pedestrian Bridge, Part X

Quote (Vance Wiley)

"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/local/indian-riv...

RE: Miami Pedestrian Bridge, Part X

Quote (Vance Wiley)

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.

RE: Miami Pedestrian Bridge, Part X

Quote (jrs_87)

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.

RE: Miami Pedestrian Bridge, Part X

Quote (MikeW7)

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.

RE: Miami Pedestrian Bridge, Part X

Quote (jrs_87)

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.

RE: Miami Pedestrian Bridge, Part X

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-closin...

http://panthernow.com/2013/08/29/fiu-anticipates-p...

“[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, “We’re pushing the envelope. This is a world’s ahead agenda.”

http://panthernow.com/2016/03/01/fiu-to-build-brid...

... The construction also includes a concrete canopy that is 30 feet wide and overall, “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-ben...

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

RE: Miami Pedestrian Bridge, Part X

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-brid...

RE: Miami Pedestrian Bridge, Part X

Quote (jrs_87)

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

RE: Miami Pedestrian Bridge, Part X

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" site:panthernow.com)

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

RE: Miami Pedestrian Bridge, Part X

Quote (jrs_87)

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.

RE: Miami Pedestrian Bridge, Part X

3

Quote (MikeW7)

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...

RE: Miami Pedestrian Bridge, Part X

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

RE: Miami Pedestrian Bridge, Part X

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.

RE: Miami Pedestrian Bridge, Part X

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.

RE: Miami Pedestrian Bridge, Part X

Quote (jrs_87)

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.

RE: Miami Pedestrian Bridge, Part X

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...

RE: Miami Pedestrian Bridge, Part X

jrs_87 - Yeah, it's still supposed to be completed in time for 2020 school year. The developer REALLY needed that bridge to be built on time, but remarkably I can't find any hard-news stories about the connection, so they must have sicced the lawyers on the news media.

Notice in your Google map (March 2019) that there is no replacement bridge construction going on - the north pier of the old bridge is still up! That crossing is going to be an absolute nightmare when Fall 2020 comes around.

EDIT: This is the walkway (2011 view) for University Bridge Residence to get to the crosswalk. Wow! - 2019 view

EDIT: this project was mentioned previously by epoxybot (Structural) 25 May 18 18:45 - my bad for not doing a forum search first.

RE: Miami Pedestrian Bridge, Part X

MikeW7, don't worry.

RE: Miami Pedestrian Bridge, Part X

jrs_87 - That would be one way to put the old piers to good use!

RE: Miami Pedestrian Bridge, Part X

2
Two photos, Fig 61 and Fig65, in the OSHA report caught my attention.



The Fig61 shows all the vertical rebar were intact after the collapse. In that the steel did not shear off like the concrete did but just debonded and separated from the spalled concrete. They were hardly bend or yielded. Most have the original 90-degree bends remain surprisingly in good shape after they came off off the concrete Member 12.

My concern is the vertical rebar of Member 12, seen from the OSHA report photo Fig61 and Fig64, did not participate much in resisting the Member 12 (together with diagonal Member 11) from being pushing outward during the collapse and none of them failed by shear. This would suggest the bulk of the resistance to prevent failure was the shear strength of the concrete alone. If any the rebar was designed to resist shear in Member 12 then the design simply did not replicate what has happened in the field.

This is most likely due to the poor structural arrangement at this location where a 8” (ID) diameter pipe sleeeve was cast horizontally for the drainage allowance. With Member 12 only 1’9” wide the 8” internal diameter sleeve would have left only about 6” concrete necking on either side of the pipe sleeve. After taking the rebar size into consideration each necking has less than 3” concrete on either side of the rebar. When Member 12&11 were pushed out of position the concrete near the pipe sleeve simply blew out and disintergrated leaving the rebar behind.

No doubt many would argue the concrete area is wider than the Member 12 as it was cast partially into the deck. However the deck has been compressed axially to deflect inward but the Member 12&11 were pushed outward so there are clear and well established shear planes between them. To make the case worse there was a construction joint, acting as a plane of weakness, between the deck and the Member 12&11. OSHA report has provided photos on the cracks and spalling at this interface prior to the collapse.

Since the majority of the rebar at the failure location remains in their original positions and suffered no shear failure the evidence would highlight a serious deficiency that the concrete member sizes there were inadequate as they were unable to produce a common strain between steel and concrete. In other word the concrete had insufficent mass to transfer its stresses into the steel reinforcement. In properly designed reinforced concrete there should be no slip in strain between reinforcing steel and concrete.

It is quite possible had the 8” ID sleeve been omitted or relocated elsewhere the FIU bridge might still exit today or the fialure pattern would have to be substantially different.

RE: Miami Pedestrian Bridge, Part X

Quote (saikee119)

The Fig61 shows all the vertical rebar were intact after the collapse.
Good post. If one were demo'ing that concrete with a jackhammer, it would look much the same. Add the part of 12 that remained on the pier and it is an interesting failure.
One variation to what I had posted earlier was that perhaps the shear plane exited the end of the deck at the top of the 8" pipe sleeve, leaving the portion of 12 below the sleeve still attached. Then as the deck was pulled over the edge of the pier, there was 10-1/2 inches where the deck/bridge weight was being supported only by that projection, and that part separated in an upward motion relative to the top of the deck. There is spalling of the edge of the pier at the center portion only, supporting this thought.
https://res.cloudinary.com/engineering-com/image/u...
from jrs_87 (Mechanical)12 Jun 19 07:23.

RE: Miami Pedestrian Bridge, Part X

Quote (Vance Wiley)

"separated in an upward motion relative"

The appearance of shattered 8" pipe pieces in the rubble at the top of the deck would support your thought as well.

Check
jrs_87 (Mechanical)8 Jun 19 17:22
jrs_87 (Mechanical)10 Jun 19 05:21
jrs_87 (Mechanical)10 Jun 19 05:36

Someone please clarify. Is not that "sleeve" the actual embedded drain pipe section for passing through diaphragm II? If so, is not "sleeve" a misnomer? The allowance of pipe at both sides of diaphragm support assertion it is actual drain. Hopefully it is not sleeve for 8" pipe to pass, because then that sleeve diameter would be greater than 8 inches. FIGG's intention was to hang drain system with no slope from the belly of the deck? There are several center line vertical passages in deck for drain system.

If the pipe is actual drain, it would be difficult to repair in the future without restricting it's diameter.

Perhaps a FEA can be made for just 11/12/deck "zoomed in" to model actual construction. NTSB has stated they laser 3D scanned the remains in 2saikee119's photo.

RE: Miami Pedestrian Bridge, Part X

Thanks jrs_87 via Vance Wiley
I hadn't even thought to use street view to view the aftermath.


SF Charlie
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RE: Miami Pedestrian Bridge, Part X

Quote (jrs_87)

Re: 8" pipe
I assumed it was a sleeve - for a smaller dia pipe thru. It would be a poor solution to cast the permanent pipe in concrete - minor structural movements would crack it someday. As to size - the roundie channel in the bottom apex was 12" dia (or 6" radius since it is hot full circle).
Perhaps that extra dim was to provide fall. Unfortunately, there was not enough time to determine the camber of the structure but I have not seen any camber instructions so I suspect it was to be flat. Kinda risky over 184 feet. Bit with the curbs and slope to center of the deck it would have only held maybe 8" of water.

RE: Miami Pedestrian Bridge, Part X

Bridge was not flat. Elevations and stations are all over plans. Dwg B-04 shows slope of 0.01 ft/ft.

RE: Miami Pedestrian Bridge, Part X

FDOT's Tom Andres had comments on the drain pipe. He noted in the submittal drawings that the drain was flat, relying on hydraulic action to drain and suggested the addition of some slope would make the drain self cleaning. He was also concerned that the 2" gap (to be later grouted) between the two halves of the deck level tower/pylon would make it difficult to fit up the plumbing. I believe 1-1/2" is the amount of drop from the North pylon to the South Landing. If the had drained the main span & the back span separately, they could have eliminated the penetration all together.



The rupture stayed for the most part within the area of the original cracking.





It looks like the rebar that was in #12 also came away fully intact and that only the concrete below the drain was left to shear off when the deck finally fell.

RE: Miami Pedestrian Bridge, Part X

My thinking about the rebar in 12, at least that which remained part of the diaphragm, is that it was on the east/west sides of the column. There was insignificant rebar on the north/south face to resist 11 pushing through so that rebar is effectively demolished.

RE: Miami Pedestrian Bridge, Part X

I'm trying to pin down when Pate first learned of large cracks in member 11. Would some one care to discuss this?

The reason I'm asking is because I found a FIU email from 3/14/18 that mentions bridge cracks, but only the ones in the diagram. So this made me look at 3/15/18 presentation again.

I found the 3/15/18 presentation and meeting seem to address only diaphragm cracking. This begs the question - when and how was Pate made aware new cracking in the structure? We know Pate "dismissed" cracks two days prior in his voicemail to FDOT. But what cracks was he dismissing at that time? The voicemail is not specific beyond north end after move.

We are told that before the 3/15/18 meeting, he went up to bridge to see it for himself. I strongly suspect he used man-lift to view diaphragm. Was his focus on diaphragm so intense he only viewed bridge from the lift? I know this is unlikely, but It would go towards explaining the lack of reaction to the state of member 11.

The photos of major cracking are dated 3/14/18, enough time to react by 3/15/18.

I might be in left field on this one. Please check.

P.S. I'm missing something that might make part of this post moot. Looking or it now. It's about "capturing the node".

RE: Miami Pedestrian Bridge, Part X

jrs_87
Best I remember is that the inspecting engineer wrote (emailed?) MCM with photos of member 11 cracks just after the shoring was removed, asking them to have the EOR look at them. The cracks were already concerningly large. Images of the letters and photos were in some of the first early reports.
I was wrong:
I my feeble mind, I had put 2 and 2 together and got 5
The "visual inspection of main span truss members on 02-06-18 after PT bars tendons No 2 and No 11 were stressed"
mentions cracks, be doesn't raise an alarm.

RE: Miami Pedestrian Bridge, Part X

SFCharlie, you're welcome. Thanks for being polite. It help lessen the sting from being scolded by fellow members. flame

Digging documents is hard work, now I know why real forensic investigations cost so much. Please be advised there are some tiny gems in the emails preserved as attachments. I use a software I already have to extract them, but it's time intensive.

RE: Miami Pedestrian Bridge, Part X

Is this correct, or do they just mean groutted?
(from the OSHA report, page 27)
"March 2, 2018 Blisters of the canopy poured. Access openings for PT bars in diagonal 2 and 11, left open."

SF Charlie
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RE: Miami Pedestrian Bridge, Part X

SFCharlie (Computer)16 Jun 19 15:02

Now I need to find something that indicates specific response by FIGG. So far, I'm so mixed up by length of thread, I'm no longer effective.


Here is excerpt from email I just found.
Source http://facilities.fiu.edu/projects/BT_904/PRR/emai... updated 5/21/19

-------- Original message --------
From: Kenneth Jessell <kjessell@fiu.edu>
Date: 3/14/18 9:36 AM (GMT-05:00)
To: Rodrigo Isaza <risaza@mcm-us.com>
Cc: John Cal <jcal@fiu.edu>, Patrick Meagher <pmeagher@fiu.edu>, Alberto De=
lgado <delgadoa@fiu.edu>, Stuart Grant <smgrant@fiu.edu>
Subject: Re: Barnhartcrane Video--BRIDGE MOVING

Rodrigo. We will have FIU staff present. Thank you for the call and email.


Kenneth A. Jessell, Ph.D., MBA
Senior Vice President for Financial Affairs/CFO
Florida International University
305-348-2101

On Mar 14, 2018, at 8:50 AM, Rodrigo Isaza <risaza@mcm-us.com<mailto:risaza=
@mcm-us.com>> wrote:



Ken,

While FIGG has further evaluated and confirmed that the cracks encounter=
ed on the diaphragm
do not pose a safety issue and/or concern, be advised F=
IGG will be onsite tomorrow morning to complete its evaluation and will lik=
e to meet with the group to clarify and explain what has occurred.



Having said that, please advise if your team will be available for a sho=
rt meeting at the site tomorrow at 9AM.



Thank you



RODRIGO ISAZA | Sr. Project Manager | PH: 305-541-0000 - Ext 371 | M: 30=
5-970-6989

MCM | 6201 SW 70th St., 2nd Floor, Miami, FL 33143 | www.mcm-us.com

RE: Miami Pedestrian Bridge, Part X

SFCharlie (Computer)16 Jun 19 15:12
Is this correct, or do they just mean groutted?

Poured after groutting.

The grout is pumped in via grout tubes except 2 and 11. In addition, all blisters are filled with cement. Blisters for 2 and 11 have foam fillers placed before pour to allow for re-access to live ends of PT bars. I presume they also had to keep cement out of the duct.

RE: Miami Pedestrian Bridge, Part X

jrs_87
I think your post and my edit crossed in the cloud ether...
I don't have the bigger cracks, pre-move email saved on my computer, so I'll have to go searching for it. It somehow slipped out in spite of the NTSB ban, so maybe it was written before NTSB's outoff date?
Thamks

SF Charlie
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RE: Miami Pedestrian Bridge, Part X

No it slipped the ban and was recalled.

RE: Miami Pedestrian Bridge, Part X

jrs_87 in your post of 16 Jun 19 15:19 I saw the email for Stuart Grant - he is the guy who took the SE view & groundlevel timelapse videos, and is likely involved with FIU's still image photography as well. I looked him up and he one of six members of FIU's Planning Staff, which in turn is a subdivision of FIU's Facilities Management (see the tabs at top of Planning Staff page). If you're looking for new rabbit holes to dive into, those names and links should provide a good starting point.

ADD: in the email you referred to, the subject was "Barnhartcrane Video--BRIDGE MOVING" which I assume refers to the Stuart Grant groundlevel timelapse that I was concerned about earlier. I have since found out the move was stopped because of wireless problems, which I now assume was between the SPMT units. My concern was that the south units were apparently moving while the north units were not, which was causing the span to slip and pivot on the north unit cribbing, which I assumed may have caused some damage to the canopy since it was anchored to the SPMT arms. The move was halted for a considerable time shortly after that. Lots of assumptions on my part, but sometimes when there are a few wisps of smoke there is fire...

ADD 2: The ground level video was removed from Stuart Grant's YT page, and I had to piece together the slowed down version (Part 1 Part 2) from two other sources who downloaded it before Grant took the original down.

RE: Miami Pedestrian Bridge, Part X

jrs_87 first mention of larger cracks is in your post 1 May 18 23:35
MikeW7 - Stuart Grant was deeply involved in documenting the construction of the bridge.. I'm sure this was all very painful to him personally. please tread softly. We all owe him alot for the videos he provided on youTube.

RE: Miami Pedestrian Bridge, Part X

Ah yes
My post may 2nd has a zip of the fiu directory.
CRACKS REPORT AFTER SHORING REMOVAL.pdf Has the scarier photos.
Memo Style.pdf is the accompanying letter.
And, yes I can't prove FIGG and co. received it...

SF Charlie
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RE: Miami Pedestrian Bridge, Part X

SFCharlie (Computer)16 Jun 19 16:38

Yes, correct file.



RE: Miami Pedestrian Bridge, Part X

I believe most of the photo & video work by Stuart Grant can still be found on the Dropbox link, Link

What FIGG knew & when they knew it was pretty well covered in the OSHA report.

SFCharlie: I think what was intended, was to indicate that the openings/voids in the top of the other permanently tensioned Blisters were poured.

RE: Miami Pedestrian Bridge, Part X

Quote (epoxybot)

I believe most of the photo & video work by Stuart Grant can still be found on the Dropbox link

Thanks for the link - I was unaware of it. Is this a personal upload, an evidence trove, or what? If there are no objections I will add clips from any relevant videos to Whirled Gnus.

RE: Miami Pedestrian Bridge, Part X

EDIT: Never mind about the pictures. Whatever it is also appears in the on-board camera view. Doesn't cast a shadow, so might be a pre-exisiting crack from the casting area.

RE: Miami Pedestrian Bridge, Part X

expoxybox, MikeW7, SFCarlie, your posts are great. Thanks. Always enjoy following them.

The DropBox files were a great source of information in the early days of this thread.

MikeW7 (Electrical)16 Jun 19 21:24, your call out of dark line is intriguing. (I see it is not to be confused with torch scorch mark) Is the perspective in the last image an optical foreshortening illusion?

I found in emails from FIGG instructions for pouring deck. Up to one cold joint was allowed for the deck. A bulkhead is called out (to form the joint?).

Lastly, did you all catch in the OSHA report the note that the first deck pour was botched and had to be jack-hammered out? There are also FDOT notes asking for flexible forming so as to not constrain curing deck.

RE: Miami Pedestrian Bridge, Part X

jrs_87 - Whatever I saw is visible in Grant's On-Board Camera video before the bridge is even moved. I went ahead and uploaded a couple of slo-mos (half-speed) of closeups of the DJI_0013 video in a new Drone Footage Playlist.

In the Move part 1 - SW view video you can see somebody in a lime-green jacket (VSL? - Hanson???) climb up on the pier at 0:12 and look at that area, so they must have known about it.



RE: Miami Pedestrian Bridge, Part X

Had Denney-Pate/FIGG seen these cracks when they gave the structure the thumbs up? Was is already cracking like this when they did their calculations which proved it was ok? Who did the red markups?

EDIT: nevermind. The bad cracking as shown below is in the FIGG structural analysis presentation meeting minutes https://cdn2.fdot.gov/fiu/14-FIGG-Structural-Analy...

A bit odd to maintain trust in your own analysis when the member is already punching out...




RE: Miami Pedestrian Bridge, Part X

Re: 8" pipe in Diaphragm 2, I previously posted "I assumed it was a sleeve - for a smaller dia pipe thru"
Looking closer that is wrong (the old assumption trick again). The 8" pipe was to be connected to an 8" pipe, using a flexible connection or Flexible section of pipe. Pipe slopes were to follow the deck slopes.
And the deck appears to slope toward the pylon from both the south and north sections.
How much slope? I cannot wrap my head around the elevations provided - something about a missing gene which prevents believing what I see thru a computer screen (it prevented me from learning cad drafting) so I must see it on paper. It is a moot point at this time, so I should be able to get over it and move on.

RE: Miami Pedestrian Bridge, Part X

Quote (Vance Wiley)

How much slope?
I mosied around the Pate-signed construction plans last night and this is what I found:
  • Page 62/110 (sheet B-37) PGL elevation at column 1 (location A) is 30.693
  • Page 32/110 (sheet B-24) PGL elevation at center of pylon is 32.44
  • Difference is 1.747 feet, which is 1% of span length, as advertised.
I had to look up PGL because I didn't know what it was, but I figured it out. The Delphi Effect doesn't always need "experts", it just needs curious people with functioning brains and some decent technical background. Bear that in mind because I'm just a retired steelworker with a BSEE I never used, and a lot of spare time on my hands.

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