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

[NOLAscience]

Sorry for my error on the elevator core. People kept interrupting me (with real work questions!) while I was looking through videos for photos and searching the drawing PDFs. The PDFs got hung up every now and then, too, which added to the discontinuity.

As for this,

What type of collapse would this be officially referred to as?
I'm used to seeing damage from collapses caused by external forces such as natural disasters. But seeing these 'seemingly' random collapses like the pedestrian bridge at the Florida university is quite disturbing.

We are supposed to design structures to resist "natural forces", though we are given a pass when truly unforeseeable events occur (e.g., an earthquake in an area not known to be subjected to seismic activity and where the building codes do not require seismic resistance). Usually after a disaster such as this one, building codes are updated to reflect something like a new design condition to be checked.

"Random collapse"? It's not random. We will find the cause for both of these collapses. Usually, the failure is caused by a combination of factors, such as (1) design decisions, (2) construction practices or variances, as well as (3) environmental conditions (perhaps unanticipated conditions). This is not "random", and we learn from each failure.

And, yes, I know that "random" has a different meaning for those of us who are scientists and statisticians as compared to teenagers and 20-somethings.

<<random
1.
made, done, happening, or chosen without method or conscious decision.
"a random sample of 100 households"
STATISTICS
governed by or involving equal chances for each item.

2.
INFORMAL•DEROGATORY
unfamiliar or unspecified.
"are you going to take some random guy on Twitter's word?"
INFORMAL
odd, unusual, or unexpected.
"the class was hard but he was so random that it was always fun" >>

 

[IRstuff]

Almost invariably, failures such as this are ultimately caused by human error or human malfeasance. If loading was incorrectly analyzed or missed or ignored or materials were incorrectly specified or incorrectly supplied, then human error. Human malfeasance might be the latter case, where someone intently delivered substandard material or intentionally failed to build per design.

We see in the case of Kansas City that someone essentially altered the design during construction and completely changed the way certain components were loaded, resulting in an overload failure. No malfeasance, per se, but certainly some amount of duplicity, where the changed construction was not re-analyzed to determine its impact on the structural integrity of the final product.

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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[azcats]

Not sure if this video has been posted or not. Some good shots of the framing. No comment on the commentary.

[URL unfurl="true"]https://youtu.be/7muzuf9Fmdo?t=1[/url]

 

[Rabbit12]

I feel a tad dumber listening to that commentary.

 

[bones206]

Another article that’s mostly speculation but some more quotes from workers speaking out about the design: Link

 

[bones206]

But seeing these 'seemingly' random collapses like the pedestrian bridge at the Florida university is quite disturbing.

For me, what’s more disturbing than design errors in all these catastrophes we are seeing is that there were clear warning signs; there was still time to make the right decisions that could have spared lives. The cracks in the FIU bridge should have been enough warning to have stopped erection of that bridge. The early pilot complaints regarding the 747 Max8 controls should have been heeded and the planes grounded. The worker complaints about structural distress in the Hard Rock building (if the allegations are true) should have been deemed serious enough to stop work. We should scrutinize those decisions to push forward despite the warning signs as much as we scrutinize the design issues. That part of it really is a human nature issue.

 

[RVAmeche]

We should scrutinize those decisions to push forward despite of the warning signs as much as we scrutinize the design issues. That part of it really is a human nature issue.

But money

 

[NOLAscience]

Cranes to be brought down by controlled explosion demolition within 24 hours. I'm betting sooner rather than later. Officials are trying to point to Friday, but I think it will happen today. They don't want too many hard-to-control people in the area, even outside the expanded exclusion zone.

According to expert spokespersons, it will look like the "cranes are melting".

https://twitter.com/nolaready/status/1184917477203107845

 

[NOLAscience]

This was in the article, "Hard Rock Hotel collapse: Theories of fatal incident focus on weak shoring of concrete tiers", in today's New Orleans Advocate,

<<That corrugated metal decking was positioned differently along the edge of the building above Rampart Street than elsewhere on the building. That caused a “shearing point,” the worker said, that he suspects contributed to the collapse.

A former worker who requested anonymity on the advice of his attorney shared that theory and blamed midstream changes to the design of the building.

“It wasn’t the ironworkers. We did everything to engineered specs. I wondered if the engineers were really OK with it,” said the former worker. “The whole crew joked about how bad it was. We all joked we’d never stay in that hotel.” >>

 

[3DDave]

Blasting the cranes is likely to finish off the buildings from the falling debris and require taking them to the ground.

 

[Kreemerz]

Thank you all for replying to me post. It explains a lot.

 

[dold]

Cranes to be brought down by controlled explosion demolition within 24 hours.

Holy crap. This is getting kinda crazy. I guess there's no hope of salvaging the concrete frame/PT levels? Certainly not after they drop two cranes on it. I will be very interested in how they rig these cranes. If it were me, I'd try to drop the tails (counterweights) off the towers - on to the street - before dropping the tower. Or maybe cut the tail and boom at the same time, then the tower later? They seem to be oriented such that the boom is over the structure, and tails over the street? At least they were when everything started happening.

And what's this about melting cranes? Clearly they're not supported by the upper slabs any more, but I don't see any melting...? But melting cranes would follow along with the current reporting/expert opinions...

 

[NOLAscience]

Holy crap. This is getting kinda crazy. I guess there's no hope of salvaging the concrete frame/PT levels? Certainly not after they drop two cranes on it. I will be very interested in how they rig these cranes. If it were me, I'd try to drop the tails (counterweights) off the towers - on to the street - before dropping the tower. Or maybe cut the tail and boom at the same time, then the tower later? They seem to be oriented such that the boom is over the structure, and tails over the street? At least they were when everything started happening.

And what's this about melting cranes? Clearly they're not supported by the upper slabs any more, but I don't see any melting...? But melting cranes would follow along with the current reporting/expert opinions...

The statement was that when the cranes are brought down tomorrow (Friday), they will LOOK like they are melting. Just dropping straight down.

They are going to send up workers using a mobile crane that was brought in. They will use a blowtorch to cut some members, and place explosives in key places. Both the counterweight and the boom must be dropped at the same time. If the counterweight is dropped before the boom, the crane would be guaranteed to fall towards Burgundy St, destroying several neighboring buildings. I imagine the arms will fall first, then the tower will come down.

The city said that the demolition team will try to avoid disturbing where the bodies of the missing workers are thought to be and they would do everything possible to avoid damage to nearby historic buildings. If the podium levels of the Hard Rock have to be sacrificed, that is simply the way it will be. Plus, the neighboring buildings didn't cause this situation.

 

[Ingenuity]

Blasting the cranes is likely to finish off the buildings from the falling debris and require taking them to the ground.

I am not so sure.

The Level 8 three foot thick post-tensioned transfer slab will have a bunch of capacity - spans of only 25' feet etc. Even catastrophically, if there was to be punching shear failure through the RC columns - with hopefully a minimum of 2 code-mandated tendons running orthogonally over the supporting column 'cores' - the tendons will go into catenary action and avoid further progressive collapse.

 

[hokie66]

Agree with Ingenuity. The photos early in this thread of the transfer slab would indicate that it is very robust. Maybe a few divots, that’s about all.

 

[JG2828]

This was on the news this morning. It is grainy cell phone video from (apparently) a few days before the collapse, showing various internal posts buckling.

Video shows workers were concerned days before Hard Rock Hotel collapse

https://www.youtube.com/watch?v=_p_3tiOesYY

 

[StrucDesignPE]

The steel floor deck was called out in the general notes to be continuous over three spans. I wonder if they were really counting on this as I can't imagine that this was possible with the spans shown on the drawings. Most deck manufacturers I have seen make deck sheets no longer than 40 to 45 feet which means most everything would have been single span. Since the deck was shored, I'm really not sure if it would matter, but it seems like it would affect at least deflections.

 

[WinelandV]

The steel floor deck was called out in the general notes to be continuous over three spans. I wonder if they were really counting on this as I can't imagine that this was possible with the spans shown on the drawings. Most deck manufacturers I have seen make deck sheets no longer than 40 to 45 feet which means most everything would have been single span. Since the deck was shored, I'm really not sure if it would matter, but it seems like it would affect at least deflections.

A co-worker and I were just talking about this when I came in this morning.

1) 3 span condition absolutely increases the capacity of the deck system - max negative moment of 0.1*wl^2 and max positive moment of .08wl^2.
2) Unless there was some special lapping called out, I don't know how you 3-span 25' bays with 45' maximum length sheets.
3) It's highly likely that the general notes were just a boiler plate.


Of note, Vulcraft's 3" composite tables only go up to 15' span length.

 

[StrucDesignPE]

It's highly likely that the general notes were just a boiler plate.

I know when I specify a 3-span condition, even just "boiler plate" notes, I check for it in the deck shop drawings. If there is a condition that is not 3-span, then I make sure it still works. I've seen the same 15 foot max span in the CMC tables.

 

[OHIOMatt]

I have stopped using the permit drawings as anything more than a way to get spans and general layout. I don't think we can really gain much by using the notes and sizes in the drawings at this point. We will have to wait to see if there is a revision set or see if there were extensive mark-ups in the shop fabrication drawings or the steel decking submittal.