Miami Pedestrian Bridge, Part VII 51

[JAE]

A continuation of our discussion of this failure. Best to read the other threads first.

Part I
thread815-436595
Part II
thread815-436699
Part III
thread815-436802
Part IV
thread815-436924
Part V
thread815-437029
Part VI
thread815-438451




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[FortyYearsExperience]

hokie66 -- bending is also just a combination of compression and tension, acting as a couple.

 

[3DDave]

The previously posted plans did show the intended steel to reinforce the joint. The part that post-tensioning plays is that it seems to significantly increases the load on that steel and was the triggering activity for the failure. Had the post-tensioning not been done the bridge might have collapsed later for some other reason, or the end of #11-12 might have been braced by the other bridge half and no one would ever have noticed the potential for disaster. I expect the NTSB will investigate all the alternatives.

 

[hokie66]

FYE,
As you are new to this site, and to this bridge discussion, perhaps you should examine what has been posted before. Maybe you consider that too onerous, but it is the only way you are going to find out about the reinforcement of both types. Don't expect too much more from the NTSB for a year or so.

 

[Retiredat46]

Is it standard practice for the entities involved in a project like this to have insurance that would pay for designing and building the replacement for something that fails during construction? Will they have to start all over with obtaining grants or other funding? What are the chances the pedestrian bridge idea will be abandoned altogether? Where do they go from here, and who is going to pay for it?

It would be a real shame to have to wait for the investigations and inevitable court cases to play out (which might take years) before doing anything to fill what was perceived as a pressing need.

 

[dik]

before doing anything to fill what was perceived as a pressing need.

or maybe a politically expedient one. There's no corruption in Florida.

Dik

 

[hokie66]

Sure, there are insurances involved, but the insurance companies have lawyers too. The bridge might be built in some form before the litigation is finished, but who pays is a great unknown.

 

[SFCharlie]

In My (unfortunately not so humble) Opinion, “FIU got gypped as far as an innovative bridge design.”
Many of you are probably already aware of the following:
Please see:
Hybrid Composite Beams - MoDOTvideo (Missouri) - Aug 11, 2011
Part of its Safe & Sound Bridge Improvement Program "Highways for Life" utilizing hybrid composite beams on three bridge projects
and :
the report .pdf

also:

“The documentary presents realization of project „Com-bridge – An innovative bridge made of FRP composites”. In 2015”


SF Charlie
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[FortyYearsExperience]

3DDave -- could you perhaps direct me to the post in which the reinforcing steel in the deck is disclosed that would accommodate the shear forces set up by the #11/#12 connection to the deck? I have searched through the VII parts of this blog, and cannot locate anything that fits that description. I'd really appreciate.

 

[3DDave]

There are links to the plans. I downloaded them so I don't know where in the thread it was mentioned. The file I have is
"13-Denney-Pate-signed-and-sealed-FIU-bridge-construction-plans.pdf" which Google indicates is available from

https://cdn2.fdot.gov/fiu/13-Denney-Pate-signed-and-sealed-FIU-bridge-construction-plans.pdf.

 

[Retiredat46]

3DDave, look at sheet B-61 in the above link.

 

[RickyTickyTavi]

epoxybot: I used to work for Structural Group many years ago. From my understanding, Structural Technologies owns VSL in the united states. VSL, in the United States was purchased by Structural Group in the 90's or early aughts I believe. All of their offices in the United States are denoted as "Structural Technologies"

http://www.vsl.com/contact-us.html

I do know at least state side that Structural Technologies provided Labor for Post tensioning. They also had in-house engineers who specialized in it. Though I'm not aware if their office in Dallas was involved in this project.

 

[epoxybot]

RickyTickyTavi - I know Structural Technologies does contract to do work through out the US but they also sell & assemble(mfg) the hardware for other contractors. What I don't know is if they provide engineering services for other PT contractors. What seems to be clear from an email is that while Structural Technologies is permitted to make wide use of VSL logo, which may or may not confuse people as to who they are contracting with, they can't actually identify themselves as an agent of VSL when contracting. Since they really aren't in the business of research & development, they are more of a Hybrid/Turnkey contractor than a True Turnkey contractor.

One certainly has to wonder about the status of the 492 unit University Bridge Residences project. They were suppose to break ground around April/May 2018. The Quonset Hut/Green House was in fact for the housing project. That is, until the project went from a mix of Condominiums & Apartments to just apartments at the beginning of 2018.

Those apartments will add at least a 1000 students crossing Hwy 41/Tamiami Trail. Yet if construction proceeds, then at some point the street crossing will have to be reconfigured to the east side of 109th Ave, to allow for construction of the pedestrian bridge. There will be more pedestrian traffic crossing 109th on both sides of Hwy 41 (Sweetwater & FIU).

On another topic, it seems there is a unwritten but general rule, the FDOT does not record from their traffic cameras. There are two other agencies, that share the Miami-Dade Sunguide Traffic Center. Miami-Dade Metro & the Florida Hwy Patrol, so there is a remote possibility one of them has the traffic cam footage. While there has been discussion of using the traffic cam system for surveillance, there doesn't appear to be any instance of it having been used this way. If & when it does, then surveillance should be a two-way street (Govt watching the public & the public watching the govt). It makes sense that FDOT would not want to record accidents at intersections, since someone might be able to find a flaw in the traffic engineering & there would be a number of requests for vehicular injury accidents in lawsuits.

I'm fairly sure I read some place in the bid documents that the winning Design-Build team was required to obtain Full Replacement Insurance.

 

[chris snyder]

Now we don't know if they were in fact stressing or destressing this bar at the time of collapse, but as a general rule the anchor location, geometry, and existing detailing is concerning.

NTSB prelim said "On March 10 per the bridge design plans, construction crew members de-tensioned the bridge diagonal members on the north and south ends of the bridge. When the collapse occurred on March 15, a construction crew was positioned on the structure working on re-tensioning the number 11 diagonal member connecting the canopy and the deck at the north end of the bridge.

The 11/12/deck connection from B-61 (pg 86/110) above at 23 May 18 03:36, shows how re-tensioning force would transfer along the deck (adding to dead load force), now that it's confirmed lower #11 rod was being tightened. One photo shows a crack starting along the deck here. Tension on this rod was 280 kips in spec, but rod is rated at 390 kips (per Williams) - is possible they "gave it a little more" if they wanted to close the crack (Tony Pipitone's WLRN interview said ~"the work being done was to address something discussed at that morning's meeting")

Another photo, above at 21 May 18 21:37 fm B-47,72/110, shows better with a rod that attaches deck to diaphragm.. but I don't understand how this worked.. installed after the deck was moved to something in the pier?).
[highlight these time stamps, CTRL-F will show "find", then click arrow to zip up to it.. thanks to SFCharlie for this tip.. works for Windows7 anyway..)

B-46, Pg 71/110 at lower left shows detail for two PVC pipes (labeled 4" I.D. Reinforcement sleeve, through which passes the rod to pier??). There are two on each side - NTSB photos show the deck broke at the outside edge of these PVC pipes. I didn't see such 4" pipes at any other diaphragm connections (there are two pages for each.. labeled Type I at south end of mainspan to Type IV at north end of backspan.. so Type II is at #11/12).

I was searching for deck-reinforcing rebar which epoxybot 21 May 18 18:40 brought up in that photo/angle I'd never seen before... I thought #12 sheared at the deck, but NO! the cold joint held... looks like it broke apart at the top of the (spec'd) 8"x12" anchor plate... looks like ~1.5" concrete behind it, and on 21" wide truss/support, would only have 4.5" on each side of it.

Besides higher stress at #11/12 shown in Toomas's analysis,

https://www.eng-tips.com/viewthread.cfm?qid=438451

, 30 Apr 18 21:20
this area doesn't have much concrete supporting everything that's embedded within it (and an 8" embedded drain pipe below it).

I have some questions about my own montage above.. the duct stayed in the member about halfway down. Will look at it more later. The length matches what's on the ground.
#11 rode up #12 during collapse (can see marks), but ended up east - rebar and PT rod/duct don't look like they "mashed" against 12 as these look about same position as they'd be in the cast member (upper rod's duct is still intact).
I don't think the 1.75" rod "kinked" or bent so much, but was pushed out of the blister as deck fell, as PT rod supported #11 a bit and "eased" it east. At end of Gwideman's loop, #11 is about parallel/resting on deck, and deck is still resting on the pier. Longer slow motion video shows the deck falls after the 10/11/canopy comes down on it - jams against pier, then falls to ground.

 

[FortyYearsExperience]

The images below are taken from the reinforcing steel details posted above by 3DDave

https://cdn2.fdot.gov/fiu/13-Denney-Pate-signed-and-sealed-FIU-bridge-construction-plans.pdf

They are taken from pages 86 and 87 out of 110.

They clearly show that the shear steel at the connection between #11 and #12 to the deck is totally inadequate. It hardly makes nominal steel requirement. The person who designed this connection was clueless. No wonder the investigation is being held in secret.

 

[SFCharlie]

"Biesiada wouldn’t say exactly what Brown and the other employees were doing on the bridge when it collapsed, but he confirmed that Structural Technologies VSL was working on the project “providing installation support for our products.” Michael Biesiada, a spokesman for Structural Technologies VSL

SF Charlie
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[bimr]

Is it standard practice for the entities involved in a project like this to have insurance that would pay for designing and building the replacement for something that fails during construction? Will they have to start all over with obtaining grants or other funding? What are the chances the pedestrian bridge idea will be abandoned altogether? Where do they go from here, and who is going to pay for it?

I have no details on this particular contract, but it is normal practice on government projects to have a construction surety bond. Liquated damages are usually included in government projects as well. The government agency requires the Contractor to submit a construction surety bond prior to signing the contract.

What is a construction surety bond? A bond is a contract or a guarantee agreement which contains the promise of a third party, a bonding company or surety, to pay a fixed sum if certain acts are not performed. The acts are typically non-performance or non-payment.

The bonding company or surety will be responsible for the dollar value of the contract, plus liquidated damages.

 

[dik]

What is a construction surety bond? A bond is a contract or a guarantee agreement which contains the promise of a third party, a bonding company or surety, to pay a fixed sum if certain acts are not performed. The acts are typically non-performance or non-payment.

I've been involved with a couple of projects where the surety bond isn't worth the 'powder to blow it to...'. A payment like this comes directly from the insurance companies profits, and they will not relinquish this easily.

Because of the 'design build' nature of the project, there may not be a requirement for bonding.

Dik

 

[bimr]

Why isn't Bolton-Perez and Associates Consulting Engineers included in the list of parties assisting in the investigation? Bolton-Perez and Associates Consulting Engineers should have done a better job of documenting the cracks.

Bolton-Perez and Associates Consulting Engineers website states that they are providing construction engineering and inspection services.

Bolton-Perez and Associates Consulting Engineers website

In my experience, having the design engineering firm conducting the construction engineering and inspection (instead of a 3rd party) is preferred since the design engineer will know the intent of the various design details and should be able to quickly respond to the questions that will come up during construction.

 

[bimr]

I've been involved with a couple of projects where the surety bond isn't worth the 'powder to blow it to...'. A payment like this comes directly from the insurance companies profits, and they will not relinquish this easily.

Because of the 'design build' nature of the project, there may not be a requirement for bonding.

Your comments indicate that you don't have much experience working under government contracts.

In most cases, bid, performance and payment bonds are required by law on public construction projects.

Virtually all of the public construction work in America is accomplished by private sector firms. This work generally is awarded to the lowest responsive bidder through the open competitive sealed bid system. Surety bonds play a critical role in making the system work.

The Bid Bond is intended to keep frivolous bidders out of the bidding process by assuring that the successful bidder will enter into the contract and provide the required performance and payment bonds. If the lowest bidder fails to honor these commitments, the owner is protected, up to the amount of the bid bond, usually for the difference between the low bid and the next higher responsive bid.

The Performance Bond secures the contractor’s promise to perform the contract in accordance with its terms and conditions, at the agreed upon price, and within the time allowed.

Surety Information

 

[dik]

bimr: The contractor on the Lindsay Police station was terminated for cause (and against my thoughts)... they tried to cash his bond, and, he walked away a million dollars richer.

The steel fabricator for the addition to one of the large shopping centres in Winnipeg made a $300,000+ error... I found it when I was reviewing bids... I usually give a contractor the opportunity to withdraw or honour his bid... the developer insisten that he not withdraw, or the developer would cash the bid bond... and, I've got a few others out there...

I don't know how the contract bonding was handled for the 'bridge', but, because it was a 'design-build' effort, bonding could have been waived...

Dik