Hard Rock Hotel under construction in New Orleans collapses... 119

[MrHershey]

A news item about concrete strength vs. removal of temporary shores at the hotel:

https://www.nola.com/news/article_64e1c72a-fcf3-11...

There's a lot I disagree with in that article.

For one, ACI 347 doesn't really apply to this case. That's a formwork guide. Upper floors were steel framed with slab on deck. Formwork removal guidelines (not rules, again 347 is a guide) don't really apply here. The proper standard to follow is ANSI/SDI-C1.0, which is for composite floor deck and available to download for free on SDI's website. The current version of that standard requires shores (if used) to be left in place until concrete hits 75% strength. A user note says typical practice is to also leave shoring in place for 7 days, but that's not a requirement.

For two, even if they did remove shores early, the main consequences of ignoring formwork removal times once the concrete has hardened is typically deflection and cracking, not catastrophic failure.

For three, the article says its source is a steel worker. While I guess it's possible for steel workers to be familiar with formwork guidelines, I'd consider it a little unusual. Going the other direction, you wouldn't expect the guys placing concrete or laying block to be familiar with AISC's Code of Standard Practice.

 

[charliealphabravo]

Does LA have inspection requirements for threshold buildings? If so, it is hard to believe that the apparent issues with out-of-plumb shoring, damaged post shores, sagging decks, post shores being forcibly removed under load, undersized beams, and poor cantilever configurations were not caught by the threshold inspector (engineer).

 

[Ricardo S. Lancaster]

LADBS was supposed to inspect and accept it.

 

[DTGT2002]

Saying 347 is not applicable is not correct. SDI-C1.0 references ACI 318, which references ACI 301 which references ACI 347 to give the designer more information regarding the behavior of formwork, which includes shoring and reshoring. I have not yet found an SDI reference that provides insight into recommendations for shored deck construction - meaning actual methods for shoring props and the like, so heading back to 347 is my typical plan.

The direction of the SDI standard that the only consideration that must be made is that shoring of composite deck remain in place until 75% f'c is attained can be rather short sighted if loading other than the self weight of the structure is involved - hence the value of a guide document that exists to inform the user about a range of options that need to be considered, rather than a minimum prescriptive code that directs a minimum outcome within noted limits - the standard is adequate for the direct components of the decking, but lacks depth in the erection portion for shoring guidance.

I'm likely biased - I'm a member of the 347 committee as well as 301, but a certain reality in this tragedy is that if we all don't understand how loadings are applied at early ages of our structures and how those loads should be released, we can certainly find ourselves having overloaded a structure.


While yes, early removal of active shores (shores under the freshly or most recently placed concrete) is likely to cause issue only with the structure directly above, removal of the lowest level of reshoring prior to releasing the loading applied by the active shores will lead to a portion of the structure carrying more load than intended.

For all the videos I have seen, I still can't point to an exact point where it all starts.

 

[MOJOJOHN]

While I agree with much of what DTGT2002 said above about what is applicable to steel decks, I do not consider a reference of a reference of a reference be a reference. When a building code references a standard, such as the Florida Building Code, it lists the references in a specific section. We do not then follow that reference, and all the others in that section to infinity.

There may be wisdom and guidance in the references of references, but forensically, we cannot use them in analyzing what was required in a structure when analyzing a failure. I know Louisiana has a different system of laws from the rest of the Country (really!) and that may affect how things are done.

The various officials and others are now "making news" as it seems to happen after all disasters such as this until the facts are known. Their announcements should be taken with a grain of salt until the building is thoroughly explored by engineers and necessary analysis done on the real structure.

I personally have given up on analysis of the permit plans. There are too many failure areas clearly seen as discussed in this forum and many differences have been seen in the photographs.

Any thoughts?

Regards,

 

[GPR_Tech]

...I do not consider a reference of a reference of a reference be a reference.

Clearly we need to see the contract documents, but
yes in many specification there are numerous reference of a reference to chase...
i.e. Specifications for Structural Concrete ACI 301 sends you to Mold and cure three cylinders from each sample in
accordance with "ASTM C 31" and so on...

 

[DTGT2002]

We should be careful here in a distinction between references that are made part of a specification by incorporation by reference versus those that are referenced in commentary or other non-mandatory means.


I was not claiming that any and all references are somehow enforceable simply by reference - but those in non-mandatory references are there to inform a reasonable engineer of available resources.

 

[charliealphabravo]

I recall that the old FL building code had a list of reference documents and also included a statement to the effect that only the explicitly quoted excerpts were meant to be enforced, not the entire document.

I suppose lifting quotes out of their immediate context has its own issues, but perhaps it is better to be minimalist and incremental rather than reference a document that might not be written in consistent and enforceable language.

Edit: And yes, the contract documents can add most any requirement, no matter how arbitrary or contradictory.

 

[StrucDesignPE]

The building is slated to be demolished. Timeline looks to be approximately 9 weeks.

https://www.foxnews.com/us/hard-rock-hotel-new-orleans-imploded-bodies-recovered

 

[JAE]

They must have gathered enough evidence, facts, etc. to conclude what happened and why.

 

[ATSE]

An ACI Guide (like 347) is just a guide. No contractual weight. None.
You don't have to be a committee member to read and understand the front page of any ACI Guide, which says "Reference to this document shall not be made in contract documents..."
In addition, the behavior and construction practices for metal deck permanent formwork are distinct from concrete formwork, so as good as ACI 347 is, it's relevance to this project's steel framing is negligible.
As MrH noted, it is unlikely that the failure was initiated by early removal of shores.
Just based on the photos in this thread, there were fundamental framing problems.

 

[JStephen]

"An investigation into the cause of the collapse is ongoing. Evidence will be gathered once the building is brought down, McConnell said."

 

[JAE]

That seems strange....seems like evidence will be altered or lost once the building is brought down.

 

[dold]

The implosion will coincide with the College Football Championship being hosted in New Orleans on Jan. 13 at the Mercedes-Benz Superdome. McConnell said the implosion could be slightly delayed because of the game, NOLA.com reported. [URL unfurl="true"]https://www.foxnews.com/us/hard-rock-hotel-new-orleans-imploded-bodies-recovered[/url]

Is it me or does it seem like the city has just decided to cash in on this disaster? Is anyone else reading into this the same as I am? First the crane demolition spectacle, now we're scheduling the implosion for the same weekend as this football game? Seriously?

Then there's the "Evidence will be gathered once the building is brought down." Seems like the least they could do is fly some drones through the mess. Hell, some people already have, or at least close enough to provide a fairly good picture of the ruins. Just fly this bad boy around each floor. Better than nothing...

 

[JStephen]

My guess is that they have done all the investigation they feel like they can SAFELY do, so anything else comes later.
Also, they had those braces bowing and stuff prior to the collapse, so they may have a pretty good idea of what went on already. "Investigation" in this case may just mean checking materials to confirm they are not faulty, etc.

 

[ldeem]

I agree with JStephen - they probably identified the root cause as a design error.

 

[XR250]

Celt83, I presume the entire company can't work on this one project since I assume the firm also has other projects. The size of this project and the size of the structural engineering company seems a little disproportionate. I'm sure it's possible to complete with a small team like that but there are also other projects, marketing, etc. that must happen. I'm guessing this project really taxed that firm.

Yea, after checking out their website, looks like two PE's, and EI intern and a bunch of drafts-people.
Seems disproportionate in general and excessively so for a project of this scale.

 

[IRstuff]

Is there a requirement that all the design resources must be organic to the bidder? Companies often hire additional resources to handle excess loads and slough them off once done. There are lots of freelancers that work on short-term contracts.

TTFN (ta ta for now)
I can do absolutely anything. I'm an expert!

https://www.youtube.com/watch?v=BKorP55Aqvg

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[NOLAscience]

"An investigation into the cause of the collapse is ongoing. Evidence will be gathered once the building is brought down, McConnell said."

This may just mean that ADDITIONAL evidence will be gathered once the building is brought down. In other words, don't expect the debris to be hauled away by February 1st.

 

[bigengineer]

See every fourth post above for all disclaimers about not blaming anyone yet. I second these type statements and want to say that before I say what follows.

I own a firm about the size of the structural firm in question. I've never designed a building this size, but fully believe we could. If a project this size presented itself, the very first thing I would do would be to bring the project to a colleague who owns a much larger firm that routinely handles projects this size. I would ask his firm to be the EOR, but let my firm gain some experience by outsourcing calcs and drafting under his DIRECT supervision. That's my initial thought and he might not even go for that. I often run hypotheticals in my head.

Point being, we have to stay within our limits of experience and not make quantum leaps.

In following this disaster, I can say that it has strengthened my resolve to remain diligent in my work product. We can become a bit over confident as engineers. When you have designed well over a thousand buildings during your career and never had an actual structural issue, being overly confident can be one result. Almost a feeling that your building can't collapse. I've often wondered how far we could, in reality, take our designs and have no issues (how much over-design is really there).

Every one of us can learn some lessons from this. There will be many to be learned as all plays out over the next year(s), but I guarantee there will be a lesson here for each and every one of us. Even if it is something as simple as don't view yourself as superior... and even listen to the immigrant worker/laborer on your project.