Miami Pedestrian Bridge, Part VIII 80

[JAE]

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

Part I
thread815-436595

Part II
thread815-436699

Part III
thread815-436802

Part IV
thread815-436924

Part V
thread815-437029

Part VI
thread815-438451

Part VII
thread815-438966



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[drawoh]

.....and why didn't the flight engineer on KLM 4805 speak up? why were they running a low-power non-standard test on unit 4? how did water get into a methyl isocyanate tank? clearly the o-ring was bad, Eastern Flight 401.................

This is way off topic, however, you mention methyl-isocyanate, and Bhopal, I presume. Methyl-isocyanate can be safely stored if its temperature is kept below 4[°]C. This is a tricky thing to do in India. The refrigeration was an active safety system. There was no fail-safe. Apparently, other manufacturers of insecticide generated their methyl-isocyanate as part of the process. There was no attempt to store it.

--
JHG

 

[3DDave]

This struggle over records highlights a peculiar legal problem - the balance between rapid and effective compensation for victims and criminal prosecution of the guilty for past problems versus wanting better policies that would preclude future problems. I think the court's interest would be in knowing where NTSB feels the investigation stands. It would be a shame to cripple a potential long term solution to move the monetary settlement up a bit. OTOH it would be good if FDOT had a victim's fund to make up for immediate expenses with the expectation of reimbursement from future settlements. And if FDOT doesn't then the Florida state government is capable of special legislation to cover it (I know, I'll see Santa in person first.)

drawoh - have a read of

https://en.wikipedia.org/wiki/Bhopal_disaster#Causes_of_the_disaster:_overview

Both explanations seem reasonable and both are horrific. As bad as it was, it so clearly could have been worse.

 

[JAE]

I think the legal problem is that one side wants to keep all the data under wraps to ensure a complete, accurate, and effective process in getting to the true cause.
The other side wants the data out in the open NOW rather than later.

The Pros of delaying release of the information:
1. Ensures a logical flow of review
2. Eliminates or reduces fear in witnesses and participants from testifying if they don't know whether they will be eventually blamed.
3. Reduces the potential for possible responsible actors from destroying evidence.
4. Avoids a media frenzy based on limited or incomplete information.
5. Avoids a media frenzy based on limited media understanding of engineering principles and processes.
6. Still allows for eventual release of all material to the public, which is a must.

The Pros of releasing the information NOW:
1. None that I can think of....perhaps others have some ideas?



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[hokie66]

I do disagree, JAE. See my comment of 22 August, 0046. The NTSB should focus on the technical investigation, and let the chips fall where they may legally. Amendment X of the US Constitution.

 

[bimr]

Agree with JAE (Structural).

Unfortunately, the wheels of justice turn very slowly.

There is a reason for non-disclosure. Nobody will freely provide information that will prevent a future problem if they are concerned with being sued.

The delay in waiting for the NTSB report does not prevent the Owner from moving forward and replacing the bridge.

 

[JAE]

hokie66,
I think if the NTSB is charged only with determining the technical cause of the collapse - and is not focused on the human interactions, processes, sequences, obligations, duties, etc. then they could proceed with publishing it all immediately.

But honestly, hokie, I don't know the actual mandate placed on the NTSB with regard to all that human interaction stuff.

It seems like they are taking a holistic approach and wanting to ensure that their human interviews are kept uninhibited by fears of prosecution should the public start pointing fingers at particular players....similar to what has been going on in these threads with respect to Mr. Pate.

I am a big state's rights guy - and the state has a right to publish this information as it is "public"...the question may be exactly when they publish.



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[dik]

Factual information should be available for anyone to do whatever they want with it. This will not change the outcome of the NTSB report or add confusion to what the NTSB is working on. It will, however, allow others to review the material as they see fit.

Dik

 

[hokie66]

Politicians are writing to the NTSB to request release of these documents.

https://www.miamiherald.com/news/local/community/miami-dade/article217279600.html

 

[human909]

My sense is that, like too many engineering failures, the Skywalk collapse was more a failure of imagination than a failure of calculation.

Agreed. Little thought was given. And at initial glance the connection didn't seem materially different for those who haven't seen similar examples.

In my experience there are plenty of mediocre engineers who give little or ZERO thought to construction. (Probably not the case for bridge engineers.)

I was once on site when the engineer responsible halted work because a suspended concrete slab on steel didn't have appropriate lateral support. (IMO tilt panels on two perpendicular sides was enough, but I never did the calculations.) The absurdity of it all was the finger pointing at the steel fabricators. Asking them why the lateral steel wasn't installed? The engineer obviously hadn't looked at his own drawings the that steel all attatched to members sitting upon the suspended slab..

The point is too often engineers just focus on the completed structure and don't for a second consider how it is to be built and connection details sometimes seem to be an afterthought. Yet it is connection details that are often the most critical.

 

[dik]

human900... I'm not sure that's correct. Most engineers I've met are concerned about how the things assembled and the constructability has to/ and is considered.

Dik

 

[human909]

Most engineers I've met are concerned about how the things assembled and the constructability has to/ and is considered.

Depends on the task.... Bridges, tunnels, mega highrise etc... For sure the constructability is often considered from the very beginning. Though for more mundane sections of structural engineering it often isn't.

Case in point is the Hyatt Regency. The start of the chain of mistakes was the engineer designing something that was eminently not constructible.

 

[bimr]

Case in point is the Hyatt Regency. The start of the chain of mistakes was the engineer designing something that was eminently not constructible.

The Hyatt Regency collapse was caused by a fabricator changing the design of the walkway hangers, not a constructability issue:

Hyatt Report

 

[JAE]

bimr, human909 is entirely correct that the start of the chain of mistakes was that the original design by Gillum, the EOR, had a long continuous threaded rod assembly for both walkways...very non-constructable.

This led to the change in the design of the hangers.

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[Agent666]

This paper (free to ASCE members) provides a good timeline for the Hyatt design and subsequent collapse, and also a lot of precursors including the collapse of part of the roof during construction. There were lots of warning signs that were missed in the process by the designers/constructors, and this paper sums them up quite concisely.
CHRONOLOGY AND CONTEXT OF THE HYATT REGENCY COLLAPSE

 

[bimr]

Not sure if it is accurate to say that the start of the Hyatt Regency chain of mistakes was constructability since the original design drawings were considered by the structural engineer to be conceptual. Miscommunication appears to be the start. Nobody working on the project followed through to prepare design calculations of the connections, and review and approve the construction drawings.

Link

Miscommunication appears to be rearing its ugly head again on the Miami pedestrian bridge project.

 

[JAE]

After hearing Jack Gillum talk to one of our local groups a while back - his drawings were not simply conceptual - the hotel was being built off them...what happened was that in that era in KC it was very common and typical for the EOR to leave ALL connection design to the fabricator. In this case, the connection wasn't typical yet was pawned off to others.

The fabricator started working on it and either they, or the GC, determined that the single line of rod wasn't feasible/constructable and requested the change to the split rods.

The fabricator then was awarded a much larger contract elsewhere and sub-contracted the shop drawings to another fabricator who, upon observing the split hanger design assumed wrongly that the connection had been engineered and completed the drawings for fabrication.

Gillum's own EIT had "reviewed" them but didn't realize the problem with a split rod assembly doubling the load on the box channel connections and passed them back as OK.

Gillum stated that his first comment upon arriving at the collapse scene was "where's the stiffeners?". He saw right away that the two box channel welds had failed at the rods.

Edward Phrang (National Bureau of Standards), the principle investigator for the collapse stated to us also that even without the split in the rods, the connections were still barely able to support the required loads of the walkways in their physical test mock-ups and calculations.

bimr - I think your thought that "miscommunication" is the primary culprit is probably accurate - miscommunication and a systemic flaw in the practice of EOR's delegating design tasks to fabricators for unique connection designs. But I think the constructability was the first step in magnifying the flaws in the then current practices.



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[Spartan5]

I haven't read it it some years now, but To Engineer Is Human: The Role of Failure in Successful Design by Henry Petroski goes into decent detail on the Hyatt Regency walkway and other failures.

https://www.amazon.com/Engineer-Human-Failure-Successful-Design/dp/0679734163

 

[TheGreenLama]

Wow! Just reviewed the NTSB "updated preliminary report." NTSB didn't have to release these additional photos at this time, yet they did. Surely they knew how damning they'd be. A question for the legal minded: Would releasing them now place the photos in different legal status (w.r.t. lawsuits) than if they were held until the final report is issued? There was some mention earlier that a "NTSB report cannot be used as evidence in a lawsuit." Why release these photos, then turn around and fight tooth-and-nail to block the judge's request for a records release?

 

[3DDave]

I suspect it's because the NTSB wants to avoid having newspapers yanking them around. Wouldn't the inability to use the report have more to do with NTSB employees being free from being called to testify as to the contents of the report? Outside litigators should be able to use the evidence in the report as long as it can be independently verified.

 

[hokie66]

Admissibility is not cut and dried. As long as it is factual, it should be admissible. But the line between fact and expert opinion is often obscure.

https://www.wilsonelser.com/writabl...les_PDFs/016111508wilson-attorney-article.pdf