Miami Beach, Champlain Towers South apartment building collapse, Part 02 151

[dik]

thread815-484587


Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

 

[SFCharlie]

Sorry about the paywall.

... found this on NPR ...
Official Who Said Champlain Towers Was Sound Is On A Leave Of Absence
Hope this helps ...

SF Charlie
Eng-Tips.com Forum Policies

 

[AtomixPro]

Every spot in that parking area was occupied. Any better images of the load on that pickup?

This would have been within view of Gabe Nir while she was in the lobby having security call 911.

This fits her account of the "parking lot of the building collapsing, like an abyss that has opened up beneath it,”. She wouldn't have referred to the patio as a parking lot.

 

[BlakeStr]

I have read 90% posts on these threads and have several observations

1.) The drawings detail 3/4" cover on the slab bottom bars.
2.) I am an engineer for a demo company and our workers spend weeks knocking concrete off rebar so the clean rebar can be sold for scrap,
3.) For the slab bottom rebars to unzip clean from the still standing slabs means either the concrete was mush or there was little cover or the bars were already corroded and popping the concrete.
4.) The collapse of the pool deck considering the main building did not fall on it means the concrete and or rebar deterioration was so bad that not even 1 level at night with no live load could be supported.
5.) Another poster explained that the drapping of this slab during failure would cause tension on the adjacent building and may have caused an outer building column at a planter to fail. I will also add that the pool deck slab that failed may have been a brace which was needed to resist lateral earth and water pressure on the far side of the building.
6.) A 11 foot unbalanced earth pressure would exert about 1k/ft at the top of foundation wall. This may have rolled the columns.

 

[Spartan5]

Sara Nir's interview, they ran out of the apartment with construction noises, there was dust coming at them in the hallway. She was talking to security in the lobby fronting Collins. The garage collapsed with the first large boom (her, her son and her daughter were together at this point) she saw this from the lobby (you cannot see the first part of the collapse from this vantage point.) Then the second boom happened as they were running across Collins. This tells me the garage collapsed with the first main collapse which they would not have seen from the lobby.

Link (Go to 14:00.)

I appreciate you sharing the link. But your transcription/interpretation leaves a lot to be desired.

She describes hearing progressively load knocking sounds around 1:10 am before a very loud “smash/collapse” noise. (15:00)

She goes to report this to the security guard because it is too late at night for such noises. (15:20)

She asks him if he hears the noises, he says he does. She asks what he’s going to do about it when she hears a very loud “big boom” noise so she runs to see where the noise is going from and she sees “all the garage is collapse.” (16:00)

So she runs back to apartment to get her family, finds them standing next the door “at entrance the her apartment.” (16:14)

She yells at the security guard to call the police as she collects her family and start to flee. (16:43)

As they approach the exit of the building, they yell at security again to call the police. Security says he does not know address. And asks them to write it for him. So her son stops and writes the address for security before exiting building. (17:00)

They flee, getting all the way across Collins before the before the big boom and her first mention of “white clouds of smoke” and not being able to see anything. (17:20).

The daughter mentions hearing “construction noises” while showering and looking out of the apartment to see “white particles” (18:54)

In your telling of this event you want us to believe that she viewed the collapse of the garage concurrent with the total destruction of 1/3 of the building. And then in 8 seconds, 1. collect her family from some portion that didn’t collapse.
2. run to the security guard, having her son stop to write down the address of the building.
3. exit the building and get all the way across Collins St. (I’m not even going to waste time measuring that.)

In 8 seconds. All of that? No.

 

[AtomixPro]

https://vm.tiktok.com/ZMdasA62E/

This is interesting. Video of deck failure visible through the north parking entrance. All prior to the full on building collapse.

 

[BlakeStr]

If the building was 120 feet tall a 30 psf wind would exert about 3,6 kips per foot shear. I doubt there were enough piles to take that and the original designer used the 1st floor diaphragm to transfer passive soil resistance from the foundation walls. Once the pool deck slab diaphragm failed there was unbalanced earth pressure on the remaining building.

 

[Mark R]

https://vm.tiktok.com/ZMdasA62E/

This is interesting. Video of deck failure visible through the north parking entrance. All prior to the full on building collapse.

Are we sure that shows the collapse of anything and not just a view down the ramp into the parking garage?

 

[serdkcin]

Are we sure that shows the collapse of anything and not just a view down the ramp into the parking garage?

Appears to be debris on the ground and a water pipe broken. Also helps explain the water in the garage.

 

[JimmyP80]

Hi long time lurker here.

Just wanting to chime in.

Since the very beginning of the thread, the most telling imagary was the punching shear failure of the pool deck, and specifically IMO how it extended all the way into the small guest parking area under the uncollapsed section..

secondly, how perfectly the slab punched through, leaving so little damage, or remaining slab tied to the coluums. Not even much rebar on show. No drop panels in sight either.

So no matter where in this area the failure initiated first, the fact is a single column or joint failure somewhere either beneath the pool deck or the guest carpark has been able to rapidly spread across the whole area and someway under the collapsed section of the building. with punching shear failures at every column on the patio deck by the looks. That's surely got to be a clue that the slab-column joint's are a universal issue

and just as I type this, i noticed Latest tiktok video and eyewitness accounts confirm without a doubt this was the sequence of events. Looks like partial slab failure into the carpark under collapsed section.. Debris is visable inline with the first column after the ramp (M8 or L8?)

 

[smaarch]

I'm an Architect involved in the design of a number of fairly complex buildings.
I'm of the opinion This building collapsed for at least three reasons
Beyond this: I've worked with some seriously great PE's and some seriously terrible PE's
What I find truly amazing in this thread are the posts in defense of a profession instead of finding the problem.
The failure of this building is an engineering problem - pure and simple.
I suggest you cats get your house in order
This will forever change the construction industry.

 

[lucky555]

In the $15M building repair and restoration, I don't see a lot of dollars going to structural repairs. Tree plan pg. 71 mentions Garage elevation -0.28' is that correct? I wondered how low can you go to keep the building's height within restrictions, or maybe low enough to add on a penthouse.

 

[spsalso]

If the pool deck and the parking area outside the lobby were the first failure, which seems very likely, why did they fail?

We're talking about a "diaphragm" held up by an assortment of posts. I don't see much of a load on those joints. WHY would a big slab of concrete just drop?

Another interesting question is what was making the sounds that irritated Ms. Nir for several minutes? It appears nothing BAD had happened yet.


spsalso

I see JimmyP80 was entering a very similar viewpoint while I was writing mine.

 

[sdh4]

@SocklessJ: A portion of pool deck/upper parking that is collapsing due to punch-through of its supporting column(s) could easily give a firm yank to to any remaining supports, potentially destabilizing them and allowing the collapse to spread progressively. The pool deck slab terminates at the columns on the boundary with the collapsed portion of the building with a 2'6" step up to the interior floor slab (see the posting by @dold in the first thread). Thus it has the potential to provide a force at a location where the column is unrestrained by the interior floor slab.

As the span of the deck gets wider because it has lost support during the progressive collapse, the slab starts behaving less like a beam and more like a heavy rope (because it is relatively slender and significantly more compliant in bending with the longer span). The slab will have significant inertia as it falls, and if it is caught by more distant supports (rather than the ground/cars/etc. underneath), it will transmit (depending on the condition of its originally-rigid joint to the supporting column) either a huge bending moment F*d, a huge tensile force F/sin(theta) (if the bottom side of the slab-column joint fails in compression before the rebar fails in tension), or both. Either way it could do significant damage to those columns or trigger buckling.

A few more shear walls would have made this structure significantly more resilient.

In aerostructures we have this concept of "widespread fatigue damage" where widely distributed damage smaller than the nominal critical flaw can nevertheless cause catastrophic failure. Perhaps what we are seeing here is a similar concept but applied in reinforced concrete where widespread corrosion and spallation allows damage to propagate in ways it wouldn't in a new structure.

 

[AtomixPro]

Mark, you can see the concrete debris on the ground. The water main break resulting from this collapse explains the water seen in the Miami-Dade video.

The person who filmed this was staying in the hotel next door. She posted this 5 days ago. Her video history checks out.

https://www.tiktok.com/@adrianitacastillero

There was another guest interviewed at this hotel

https://www.youtube.com/watch?v=BvkRmtmB-Fw

This seems to be a different party but same view. Both shouted at the 8777 tenants to get down.

 

[NOLAscience]

spinspecdrt noted on the previous thread @ 27 Jun 21 02:59,
"I agree with columns on 9.1 line. Particularly @ I and K line. Both are exposed to planter box at lobby level."

Are there any recent photos of this column in the planter? Or that column in the parking garage?

Where did the pool contractor make his comments about the standing water in Parking Space 78? I would like to hear the exact wording.

 

[AtomixPro]

The Sara Nir (unit 111) interview on Anderson Cooper. go to 14:00 A progression of deck slab collapses is becoming clearer now. Question is where it began.

https://omny.fm/shows/anderson-cooper-360/12-dead-149-unaccounted-for-in-surfside-condo-coll

 

[Spartan5]

Another interesting question is what was making the sounds that irritated Ms. Nir for several minutes? It appears nothing BAD had happened yet.

Slow (relative) progressive failure of deck/slab working it’s way towards 111?

 

[dik]

Could be... that, however, might be an oversimplification... could be caused by a faulty design, could be caused by not recognising corrosion of reinforcing steel... Would a clever Architect have noticed that? Might be a negligent/criminal lack of maintenance and repair... maintenance and repair not undertaken because the AHJ may have said that there was no problem... could be the fault of the authorities not following up with statutory requirements... Could be something else.

dunno enough yet... jury's still out...

Your architect 'over simplification' does not further this discussion. The dialogue here simply tries to come to a reasonable conclusion based on the information on hand at the time... We all know that something 'bad' happened, and steps should be taken to prevent this in future... just don't know what these steps are at this time...



Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

 

[Spartan5]

Where did the pool contractor make his comments about the standing water in Parking Space 78? I would like to hear the exact wording.

It’s paraphrased, here:

The deepest puddle of standing water, according to the contractor, was located around parking spot 78 — an area that building plans show is located directly under the pool deck where in a 2018 inspection report, engineer Frank Morabito had flagged a “major error” in the original design that was allowing water intrusion and causing serious damage to the structural concrete slabs below.

He did not photograph that standing water because he was there to examine the pool and what was underneath it.

 

[spsalso]

It looks like the pool deck and guest parking area failed first.

WHY?

I see really minimal loads on those column joints. Weight from some concrete and maybe a car (but not on the pool deck). WHY?

I am looking at, in photos, the rebar at the top of the columns. I am not impressed. Imagine if there had been some horizontal pieces 12' long running through that joint. Would it then have failed?

I am reminded of the Nimitz freeway collapse in the Loma Prieta earthquake. I saw what I took to be a shocking lack of overlap in re-bar in the joints between the columns and the horizontal. Hey, guess what? It pancaked. Surprise!


spsalso