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

 

[Seppe]

A large portion of the pool/amenity deck underwent some measure of collapse, and according to a couple different eyewitnesses this preceded the superstructure collapse.

I would be surprised if the investigation ends up showing that an issue on the roof ended being the primary, driving factor in this collapse. A contributing issue? Sure. Perhaps even the straw that broke the camel's back. But structure at the amenity level is what to me warrants a tremendous amount of initial attention. A bit of extra load on the roof or not, the amenity level presents as if it were a bit of a ticking time bomb.

 

[warrenslo]

warrenslo - the collapsed pool deck:

The pool equipment room where the pool contractor took the photos (highlighted in yellow below) did not collapse, it is still standing today.

We do not know if the pool deck collapsed first or if the building collapsing on it brought it down (more likely the latter in my opinion based on the damage pattern and 111's testimony.)

111 seems to have escaped via the pool deck as he said he went outside to go investigate and he had direct access - if the pool deck had collapsed 1-story into the basement at this time then this wouldn't be possible.

From 412's vantage point she wouldn't have seen the first collapse, her guest bedroom is in the way, only floors 9-12 in the x12 stack have a balcony viewing the initial collapse. Its likely she was seeing pool deck dropping due to the initial collapsed portion of building falling on it. This is evident by her phone cutting out seconds (not minutes) after which is when the second portion of the main collapse occured.

-W

 

[warrenslo]

The initial failure was under Unit 111. Gabriel Nir, Unit 111's testimony:

When part of a beachfront condominium building collapsed in Surfside, Gabriel Nir and his family escaped what would have been certain death.
"The first collapse happened, and me and my mom and sister went out," Nir told NBC 6 just hours after Champlain Towers South partially collapsed Thursday morning. "We see the collapse happening on the poolside and I saw a bunch of cars going inside the car garage, so I panicked, my mom panicked, everyone panicked."
Nir's first-floor apartment, unit #111, was above a planter and underground garage entrance ramp that engineers years earlier singled out as the most serious flaw in the building.
Proximity to that apparent failure point likely saved his and others’ lives.
"It was at that moment I saw the ground shaking. I felt something was happening," Nir said. "At that time, I had to run out. I told my mom, my sister, 'everyone, start running,' and so that happened. Everything started, out of nowhere, like cement, dust, sand coming out."
The first signs of collapse minutes later, appearing right at this unit. Nir estimates perhaps two minutes after he reacted to the thunderclap of a beam or column likely falling beneath his unit.
While that may sound like a delayed collapse to a layman, engineer Jason Borden says it’s an instant in engineering terms.
"It sounded like an immediate or spontaneous failure, which is unusual in a modern structure which is built with ductility, durability and redundancy in mind," Borden said. "So the fact that it failed as abruptly, as immediately as it did leads us to believe there had to be more than one thing going on there."
The time for warning and escape are built into designs, but there wasn’t much warning here.
"A freak accident, if you will, once in a lifetime for sure. I think possibly it was a collective of things, deterioration in the structure," said Yaniv Levi of Coast to Coast General Contractors. "It's very unfortunate and this is the first time I’ve ever seen this in my industry, ever."

 

[Spartan5]

111 seems to have escaped via the pool deck as he said he went outside to go investigate and he had direct access - if the pool deck had collapsed 1-story into the basement at this time then this wouldn't be possible.

”The first collapse happened, and me and my mom and sister went out," Nir told NBC 6 just hours after Champlain Towers South partially collapsed Thursday morning. "We see the collapse happening on the poolside and I saw a bunch of cars going inside the car garage, so I panicked, my mom panicked, everyone panicked."

“We see the collapse happening on the poolside and I saw a bunch of cars going inside the car garage…” seems pretty cut and dry to me. When they escaped, the failing deck had yet cut off their escape route. The failure then progressed towards the building and unit 111 until it compromised the critical columns holding the bulk of the building up.

If I’m not mistaken, there was a 911 call about a collapse in the garage with emergency units already in route when the whole building came down several minutes later.

 

[spsalso]

Nir's statement is not "testimony".

It's his recollection, and perhaps not worded clearly.


spsalso

 

[TheGreenLama]

Should an entire building collapse if just one (1) column fails, either by corrosion of cross section, vehicle impact, subsidence, etc.?? This is of course a rhetorical question, because the answer should be no.

So the next question is, Is this building special in that it may have taken just one column failure to bring down a building? Is there one critical column, or could it have been any?

If one column failure is not enough to cause building collapse then how many columns must fail to bring down a building of this type? Two? Three? Or are we back to this building being deficient in ways other buildings are not? I like the Jenga analogy someone else mentioned earlier, and the complete lack of ductility.

And even if all three exterior columns (I-K-L 10) failed, should a building of this type be able to maintain its overall integrity, or was complete collapse inevitable?

Of course all this assumes column failure is the culprit.

 

[Spartan5]

From 412's vantage point she wouldn't have seen the first collapse, her guest bedroom is in the way, only floors 9-12 in the x12 stack have a balcony viewing the initial collapse.

412 had a wrap around balcony that directly overlooked the pool. Same view as 111, only higher.

 

[spsalso]

warrenslo is advocating that the first collapse was under Nir's apartment. If so, Stratton would indeed have had trouble seeing it.

But it appears what she DID see was the collapse (or the aftermath thereof) of the pool deck, while still standing in her uncollapsed apartment.


spsalso

 

[LionelHutz]

I thought the Nir family from apartment 111 escaped though the apartment door by going down hallway into the part that didn't collapse.

 

[Spartan5]

It seems pretty certain that the collapse occurred in the pool deck and garage first. Before progressing towards and into the columns supporting the building.

Another account from the mother of Gabe Nir, both of whom were in unit 111. She states that she heard loud noises like “construction knocks” loud enough to warrant making a noise complaint, starting at 12:30 am. It was while she was in the lobby talking to the security guard that she saw the ground level of the parking garage collapse. Which she reported to the security guard. That would explain the first call to 911. She ran back, collected her family, and they all ran to the street, moments before the whole thing came down.

She returned to her home on Collins Avenue at around 12:30 AM. “I was sitting in the office, going through emails and the like, and I started hearing noises,” she told the COL news website.

Nir described the noises as sounding like “construction knocks” and was disturbed that they were being made at such a late hour, with her son and daughter fast asleep in nearby rooms.

“I thought someone had decided to renovate their apartment in the middle of the night,” she said. “At first, I ignored it. But a few minutes later I became upset about it and left the apartment.”

Nir says she went to the lobby of the building where she met the security guard sitting at the entrance. She reported about the noise and asked him to call the police to make a complaint.

What kind of failure are we looking at where the deck of the garage and pool has sheared more or less cleanly away from the columns?

“As I was standing in the lobby, I saw the parking lot of the building collapsing, like an abyss that has opened up beneath it,” she recalled. “I was in shock. My thought was that these (noises) are not renovations. This is an earthquake!”

She once again turned to the security guard and ask to call the police, this time reporting an earthquake. “There was a very loud noise,” she told him.

Nir then quickly returned to her condo and woke her 15-year-old and 25-year-old children (her husband and other children were out of town). She urged them to leave the house as fast as they could.

“We left the building Within a minute and started running down the street, as far as we could,” she said.

“I heard a huge noise behind me, but I didn’t want to turn around,” she added. “A huge cloud of dust flooded the space. I thought the end of the world had come.”

 

[spsalso]

Ms. Nir was in the lobby when she saw the parking deck collapse. The lobby has a view of same, and photos show at least a part of that deck collapsed (and, of course, the pool deck).

For the timeline, the time of the 911 call is known.

I wonder if the pool deck had already collapsed. I think it would have made a lot more noise than she heard, so probably not. I wonder what she heard earlier, when she was in her apartment. And it took so long, too: "At first, I ignored it. But a few minutes later I became upset about it..."

Uh, wow.


spsalso

 

[la belle vie]

I am also of the opinion that the collapse occurred in the pool deck and garage first, then progressed toward the building removing lateral support from the column and/or pulling them over. Whatever the final explanation ends up being, building inspection programs should explicitly consider potential failure modes (PFMs) the way we do with dams. This starts with identifying the possible PFMs during the design process and through periodic review. If PFMs cannot be engineered away in design or subsequent retrofitting, they need to inform the inspection process. Knowing the PFMs and fully understanding how they would play out and the signs they might be occurring provides a framework for action. Action isn't always repairs. It could also be more frequent monitoring or shoring. The "exterior structural slab pulls down building" PFM seems like it could apply to a lot of buildings with exterior plazas and underground parking.

 

[warrenslo]

I just found something interesting:
Column I-8 appears to be mislabeled as a column type G on the structural framing plan, it appears it was supposed to be a column type L.
It is clearly longer and skinnier than the remaining G columns in both the architectural and structural drawings.
The roof replacement (Roof #2) is directly above this column.

 

[SocklessJ]

I think we're all having a little trouble connecting the collapse of the pool deck to failure of the building columns. There must have been some sort of horizontal propagation of slab failure, leading to punching shear failure at the building columns due to unbalanced moments. This then doubles the unbraced length, leading failure of the column in compression.

Not the traditional form of progressive collapse, but plausible.

I do wonder how this building would have faired in a major hurricane.

 

[warrenslo]

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.)

 

[dik]

Could it be from all the corrosion to the rebar that the total structure was at the point of collapse?

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

-Dik

 

[spinspecdrt]

On S1 (pile cap plan) it is labeled "L"

 

[serdkcin]

Warrenslo:
I took her interview as she was in the southern portion of the lobby when the first major event occurred which would allow her to see the cars falling (she said she saw cars getting swallowed up in another interview) in the guest parking lot just outside the lobby; the guest parking area is adjacent to the pool deck separated by a gate and planter/fence. To me it sounds like the pool deck/guest parking area collapsed first then she went and got her kids and got them out through the front lobby. When they got across the street the building went down.

 

[w-streng]

My bet is this is where it started ('cars sinking into basement'). Punching failure and progressive collapse towards main tower and overloading columns I10 & K10. Load transferred on the demising walls on grid K (cracks seen rapidly opening in wall by resident on 6th floor), she got out in time. I8 or K8 (or thereabouts) then failed.

 

[serdkcin]

w-streng:
That column with the parking spots 72/73 has intrigued me since I saw it. I’m wondering if one can infer what side failed first based on the left side having the angled slab outside while the right is angled within the column. Also looks like a bit of discoloration of concrete on the side that protrudes.