Miami Beach, Champlain Towers South apartment building collapse, Part 18 30

[SFCharlie]

A continuation of our discussion of this failure. Best to read the other threads first to avoid rehashing things already discussed.
Miami Beach, Champlain Towers South apartment building collapse
Miami Beach, Champlain Towers South apartment building collapse, Part 02
Miami Beach, Champlain Towers South apartment building collapse, Part 03
Miami Beach, Champlain Towers South apartment building collapse, Part 04
Miami Beach, Champlain Towers South apartment building collapse, Part 05
Miami Beach, Champlain Towers South apartment building collapse, Part 06
Miami Beach, Champlain Towers South apartment building collapse, Part 07
Miami Beach, Champlain Towers South apartment building collapse, Part 08
Miami Beach, Champlain Towers South apartment building collapse, Part 09
Miami Beach, Champlain Towers South apartment building collapse, Part 10
Miami Beach, Champlain Towers South apartment building collapse, Part 11
Miami Beach, Champlain Towers South apartment building collapse, Part 12
Miami Beach, Champlain Towers South apartment building collapse, Part 13
Miami Beach, Champlain Towers South apartment building collapse, Part 14
Miami Beach, Champlain Towers South apartment building collapse, Part 15
Miami Beach, Champlain Towers South apartment building collapse, Part 16
Miami Beach, Champlain Towers South apartment building collapse, Part 17


SF Charlie
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[Murph 9000]

Question for structural engineers. Is it possible that K13.1 punched through, the deck dropped just a bit and then remained in catenary for up to five minutes, and then failed altogether? The reason I am asking this is because I am trying to explain the 1:10 crash heard on the first floor, which was followed a full five minutes later by the deck collapse at 1:15.

Is it possible that the deck could remain in this state for up to five minutes?

Not a structural engineer, but it seems to me that K13.1 punched through at least several weeks before the collapse, when the planter visibly dropped by a couple of inches. Some combination of the rebar or catenary held the deck up but in severe distress after that. The crash at 0110 could maybe be something like the last of the K13.1 rebar breaking, or the next column punching through, as the collapse finally spread out from that initial failure. It could also be something else failing from the catenary tension created by the K13.1 punch through (e.g. the slab pulling away from the southern edge of the site, or the torque action from the catenary tension on the KLM 9.1 beam connections).

 

[Sym P. le]

My two cents, again. Too much has been made of catenary forces. They are not part of the design calculus though their presence through the state of decay until collapse cannot be denied. They are role players but not likely the overarching scheme.

Although some initial speculation argued the weight of the sagging slab exerted horizontal forces on the building support columns pulling them askew, the collected evidence shows the BMA/column connection was not capable of developing lateral forces by catenary action as the BMA's would simply rotate off the column if they sagged. The remaining column, significantly diminished, remained standing until it succumbed to its newly introduced weakness. (The five minute time lag, or the parkade video)

We can also see that the south perimeter connection was incapable of sustaining lateral loads as the deck either pulled off the wall or fractured as it sagged, again truncating the development of any catenary force.

Where catenary forces are important is in load redistribution at the column connections. As the connection at one column deteriorates, load is redistributed to adjacent connections until they too succumb to decay. It is this catenary action that I argue caused the rebar at stall 135 to break. The forces are capable of breaking rebar but not toppling columns or buildings in this case.

With regards to "punched through", I don't see black and white, I see a grey progression. Just as the planter column and 76 connections existed in a diminished state, there is still room for further decay to advance the progression without having to witness a free hanging slab.

In sum, the WJE graphics may be misleading in this regard but they serve to make a valid point. Eventually, everything breaks free.

 

[IanCA]

The reason I am asking this is because I am trying to explain the 1:10 crash heard on the first floor, which was followed a full five minutes later by the deck collapse at 1:15.

@MaudSTL, I recently rewatched the ABC Good Morning America interview by T.J. Holmes with the Aguero family and I think the existing timeline entries can possibly be updated to agree with your statement above.

The current entries I see for "Aguero" in CTS Collapse Witness Statements:
~1:15 felt The building shake "like the first gust of wind from a storm" while playing video games
>1:15 felt The building shake "kind of like [Super Storm] Sandy"
1:22 felt The building shake "…like a jet took off right on top of our building," and they evacuated to the beach via the west staircase.

ABC Good Morning America
June 25, 2021, 6:22 AM

https://abcnews.go.com/US/survivors...building-collapse-knew-race/story?id=78482867

Albert and Janette Aguero, Justin Athena.

From the interview:
0:14 T.J. Holmes: So Albert what was the sound like? Albert Aguero: It was like a really loud clap of thunder, Justin was awake and heard multiple sounds, it was about three different distinct sounds he said. [The third sound was the collapse of the north wing.]
0:24 And Justin when you heard it when did you think this is a problem? Probably the third one I mean it kind of felt like a jet took off above the building and being around Sandy I knew it was a lot different.
0:40 T.J. Holmes: You all tell me you the hear the sound and what did you see first? [Albert] The chandeliers and the pendent lights just swaying completely which was not normal that was not a clap of thunder it was not a storm it was something else. This was after the collapse of the north wing, the third event described by Justin, because until that point Albert had been asleep.

Do you have links to any other interviews they gave, please?

I take the phrase "about three" to mean that there were at least two events that Justin heard before the collapse of the north wing at 1:22am which they all heard and felt and they saw the effect of the building shaking with the chandeliers and the pendent lights just swaying completely. This matches up with the crash heard at 1:10, the deck collapse at 1:15 and the main collapse at 1:22.

 

[MaudSTL]

Here is the link that includes Justin Willis’ description of three events: UConn pitcher Justin Willis, family survived harrowing escape from collapsed condos in Surfside, Florida

The big question to me is, what “thunder” and “metallic crunch” woke up the Longobardis in 309 in time to go to the window to witness the pool deck collapsing from south to north? I feel skeptical that it was the 1:10 crash heard in the lobby and in 111, as the people on the first floor didn’t hear thunder or crushing cars at 1:10..

My theory is that the parking deck collapsed at 1:15 with a deafening crash in the lobby, like thunder and with a metallic crunch in 309, like a supernatural force in 611, and like a gust of wind in 1106. I wonder if the deck then attempted to readjust its load for just a few seconds, unzipping itself from the south perimeter wall. This would have given the Longobardis time to wake up and run to the window to see the pool deck collapsing from south to north, which in 1106 sounded like Hurricane Sandy.

The Fire Dept employee on the 12th floor who ran down to the street described the 1:22 building collapse as sounding like a jet, as did Justin Willis in 1106.

 

[Reverse_Bias]

Keep in mind Paolo Longobardi said he saw the deck collapsing from S-N. Although he only saw the east end of the deck collapse zone, his statement does make it unlikely that the collapse started at K13.1.
It's much more likely it initiated closer to the southern wall, either in the positive bending zone or the along the wall itself. Both those areas also have an E-W elongated shape that might initiate a S-N punching shear failure as opposed to one that radiates out from a point like you'd expect if it initiated at K13.1.

 

[Sym P. le]

It is fairly certain that at 1:14, Sara Nir was at the front desk complaining of loud noises. At 1:15, she witnessed a portion of the lobby parking area collapse and responded by running back towards her unit, 111. Her two kids were already at the door/hallway and they all went to the lobby. Sara and Chani ran clear of the building while at 1:19, Gabe, who remained in the lobby, called 911. As he witnessed further collapse of the lobby parking/pool deck, he interrupted his call to run for his life, shrouded in dust. The tower collapse is said to occur variously at 1:22 or 1:24. (Washington Post Article 1 and Article 2, CBS Article, NY Post Article)

It can be a mistake to equate loud noises with any portion of deck "breaking free". It could be that there is a load redistribution with elements breaking but not much in the way of a visible presentation. For example, the loud noise before 1:14 could be the rebar breaking at stall 135. This does not necessarily mean the lobby parking collapsed at that time, rather it could be another step in the progression.

The metallic crunch heard by Longobardis could have been the first collapse of the parking area given their bedroom window was only two floors above the truck and car coming into contact with each other. They then arose and moved to the sliding door where they witnessed the pool deck collapse from south to north. They decided to leave and finding the west stairwell undesireable, ran to the east stairwell and exited through the lobby garage. From the given timeline, they had a six or seven minute window to accomplish this.

Others on higher floors and facing west heard only increasing noises and moved to exit via the west stairwell, problematic though it became or was.

 

[IanCA]

Here is the link that includes Justin Willis’ description of three events

@MaudSTL, thanks very much.

 

[MaudSTL]

@Sym, I was unable to find a statement by Adriana Sarmiento that a family of four came running out of the garage ramp. I suspect the Longobardis exited the east stairwell on the first floor and feom there exited the building at the lobby. In a contemporaneous interview, Chani Nir said she saw a family leave the lobby.

Also…we know that the building collapsed almost exactly at 1:22 by the time stamp on Gabe Nir’s 911 call as they ran down the street. During that call Gabe reports the collapse live at about 01:21:57.


@IanCA, I am not sure how to incorporate what Justin Willis said into a chronology. I realize that it isn’t particularly important. My goal is just to be consistent and comprehensive, as I intend to leave the Timeline up for convenient reference.

 

[MaudSTL]

WJE has put up its presentation on YouTube so it can be seen without registering.

https://youtu.be/2UpjMV9PYgI

 

[Sym P. le]

ASCE Dallas - Jan 9, 2023 Keynote Presentation

Another Youtube video with Gary Klein doing the presentation with similar slides.

[URL unfurl="true"]https://www.youtube.com/watch?v=R_fV3bsnAxE[/url]

 

[Sym P. le]

Thanks for the clarification. CTS Timeline

CBS Miami Surfside Condo Collapse - 911 Calls on Youtube

 

[Sym P. le]

More thinking out loud.

It's clear that the pool deck shifted at the planter/column 76. It may be a distraction that the lobby parking collapsed first when in fact the progression of load redistribution would have radiated in all directions from these two locations without anything collapsing. Imagine the implications of a BMA shifting --> building shifting but not collapsing. I suspect that is what was happening in the days/hours leading up to the collapse. Lots of noises but no readily visible indicators.

Just as the shifting planter was visible from the deck but not the garage, any top side structural shifting in the building would be obscured by finishes. Even if the finishes were visibly effected, that would be seen as an inconvenience or insult rather than a red flag indicator of the more serious underlying cause.

In the end, this whole thing was a game of Jenga.

 

[stcbus]

Unless it’s been debunked I remember reading early after the event that visitors heard loud creaking sounds the previous night or two before the collapse.

 

[Sym P. le]

That's exactly the point. Many pieces were being pulled out of the Jenga tower. So much so that putting the emphasis on one syllable or another is missing it.

 

[MaudSTL]

Agreed. I still need to update the Detailed Data tab in the Timeline. Unless there are corrections, I am pretty sure I am finished updating the High Level Sequence tab.

 

[IanCA]

I am not sure how to incorporate what Justin Willis said into a chronology.

@MaudSTL, I agree, perhaps just adding 'heard' to the existing entries would be sufficient.

 

[Jeff Ostroff]

STCBUS, yes you are correct. The day after the collapse, there was an article in PEople, from a CNN interview of a man whose mom said she heard creaking sounds in the building the day before she died in it:

Talk about the cracking noises starts at 2:55 on the video in this article

https://people.com/human-interest/m...g-from-her-surfside-building-before-collapse/

 

[Reverse_Bias]

Gary Klein presentation talked about how building end of the Beam A's was not attached to the column properly. I'm still curious about the deck end of KLM 11.1.
K 11.1 was the only one of the three visible after the collapse (left center of pic). I see the top rebar which was connected to the deck, but no rebar below that where the Beam A should have been connected. I'm thinking that there must have been some sort of improper connections at that end too for the deck collapse to have been able to take the beams don with it.

 

[Sym P. le]

... no rebar below that where the Beam A should have been connected.

Excellent point!

 

[Sym P. le]

BMA's are only 5 1/2" deeper than the slab at line 11.1 and could have been nested between the column/slab connection rebar. In the recovered specimen, it looks like the end that rested on line 11.1 (the far end in the image) is void of concrete which allowed it to slip off the column support. If so, the surviving column presents as expected.