Miami Beach, Champlain Towers South apartment building collapse, Part 16 24

[dik]

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

-Dik

 

[zebraso]

...make repairs to an adjacent structure

....ummm. Structure??

 

[zebraso]

It's a "damning statement" that he is willing to replace a concrete block privacy wall, in order to move his project forward?

I am not seeing the words "CMU", "concrete block", or "privacy" in the quote. He is not making a distinction. But even if he was it would be just as curious. How do you damage the CMU wall, without going through the perimeter basement wall with the vibrational force via the earth? It's another matter yet to define whether a CMU wall is a "structure" in its own right in regard to the vibration standards. It's clearly not the same type or level of damage to replace stucco vs relaying/replacing a block wall whether or not it supports a roof. And it was stated by a structural engineering consultant in one of the links Maud provided that the concrete at the top of the perimeter wall, (post collapse) shows signs fracturing from intense vibration force in the area of concern. The only thing that is left is to determine whether that wall is "structural" in a strict sense, and it seems there is a certain faction here that strongly believes it is.
Having said all that I'm not sure the idea that the wall has "mostly not fallen down" is a test that could be written into any standard.

Edited once for clarity.

 

[Phil1934]

There was a five year gap between the time of pile driving and the collapse. Everyone is worried about the time noises appeared. If it was quiet for five years previously I don't think you can reach back five years for a culprit. I worked for a company sued by a bank that said pile driving several years earlier was what caused their building to develop cracks. A check of records showed pile driving was done before their slab was even poured.

 

[spsalso]

" How do you damage the CMU wall, without going through the perimeter basement wall with the vibrational force via the earth?"

The only damage to that wall that was described in the article was done previous to the pile installation. I don't see anything about it being damaged BY the vibration from the pile installation.

"... the concrete at the top of the perimeter wall, (post collapse) shows signs fracturing from intense vibration force in the area of concern."

As far as the concrete at the top of the wall being damaged by intense vibration force, a person could wonder whether there was any such vibration when the building fell down. I am surprised that the wall stood at all.


spsalso

 

[SwinnyGG]

....ummm. Structure??

Semantics.

 

[arbitraria]

I am surprised that the wall stood at all.

How many times was this wall rebuilt over the life of this complex? There were at least some sections that blew over in Hurricane Wilma in 2005 (video appears to show the failure of the entire eastern section abutting the pool deck, shown approximately 3:30 in

https://youtu.be/X4BwnI0VyPM).

Do we know if that was the original wall, or if it had sustained damage previously and/or subsequently due to tropical force winds? I can't recall how thoroughly that was hashed out here.

Infiltration was a known issue at this location on site, as was shoddy construction and maintenance. I have little faith that any potential damage to the connections at the pool deck and subterranean structural wall was repaired properly if at all. I'm sure the vibration from the pile driving didn't help, but it was likely just another irritating factor on top of decades of neglect and mediocre construction. This entire disaster should be seen as a cautionary tale, but we know how that goes.

 

[Eufalconimorph]

Looks like insurance companies are raising prices for condos in the area, if they'll even renew policies at all. The Florida legislature seems to be getting the free market solution they wanted when they declined to improve inspection requirements.

 

[MaudSTL]

Everyone is worried about the time noises appeared.

To clarify, this was a building that made noises over time…it was not silent until the 24 hour period described in the Timeline spreadsheet. Residents specifically complained during the period of construction next door (which started 2016) and also during the roof work that was going on when it collapsed. At the time of the collapse, there was an interview quoting a resident stating that the building always made sounds, but I don’t have a citation or know how long that person had lived there.

 

[AusG]

And speaking of timelines, not sure Josh at BI has it exactly straight in his video re the wall connections. Please correct me if I'm wrong but I don't think the timeline establishes that any of the pool-adjacent area collapse could have been visible to folks driving into the garage pre- the overall building collapse, or was seen for sure by residents above. Aside from the timeline matter, if a portion of the pool deck had collapsed leaving enough standing to drive around under obliviously, the catenary force on the columns would have been reduced commensurate with the area of deck already on the ground. Don't we need the whole catenary, +/- the reaction perhaps of the wall connection letting go, to bring the building down?

 

[zebraso]

catenary force on the columns would have been reduced

In this scenario you are stating the wall disconnection at most should provide stress relief to the remainder of the deck support, stabilizing it or isolating it from certain forces...all else being equal. And I guess by "equal" I mean not delaminated, spalled, corroded, or otherwise dilapidated. etc. Posing this as a question so I can understand. Or maybe that is reading too much into it. Do you mean that the entire deck in more or less one piece is simply required to generate the required vertical catenary. And I am sort or reading as a question that the shock wave of the wall disconnection is involved in getting the process going (stack of cards thing). Sounds like a new brain stormer. Who is going to model that?

 

[spsalso]

If the catenary force of the concrete deck brought the building down, it would have happened right away. There would not have been a several minute wait.


spsalso

 

[SwinnyGG]

That's not necessarily true... it depends on the relationship between the applied load, the ultimate strength of the structure, and the level of ductility available to absorb load over time.

 

[AusG]

I'm comparing two scenarios. The first has the pool deck columns no longer carrying full load due to punching shear, the resulting catenary (plus some thermal shrinkage overnights) is being held by the building columns and the wall connection, one of of which fails and the reaction breaks the other one. The other scenario, which I think is Josh's, is that the wall connection failure, triggered by the thermal shrinkage and weakened connections, predates and precipitates the punching shear which then eventually brings down the building. Both are clearly plausible but his diagrams had some sections of the pool deck fully collapsed minutes before the building, and my feeling is that would have lessened the catenary pull on the building columns and so eased their stress.

 

[zebraso]

I'm comparing two scenarios.

Thanks for clarifying that. It's a complex thing with multiple elements ready to go super critical. The idea that I have a bit of trouble with is that the wall was compressing the deck and and holding the whole thing together. But then from what Josh was describing that is not very likely in terms of the failures. i.e. that the wall was not a required structural element in that sense. You are I think looking at it without that idea being incorporated at least. So anyway I get you are talking about what more likely fits the timeline. And of course the ductility is in that. If the perimeter wall is not holding the building up (wild theory there) it's a little harder to explain, in simple terms.

 

[SFCharlie]

New FIU bridge designs revealed, four years after fatal collapse
06 MAY, 2022 BY ROB HORGA

 

[SFCharlie]

Upps, wrong thread. I'll climb back in my teapot now...

SF Charlie
Eng-Tips.com Forum Policies

 

[MaudSTL]

Members of the public may attend the June 9 NSCT Advisory Committee meeting to get the status of NIST’s investigation of the CTS collapse! Here’s a link to the announcement and agenda. You have to sign up before May 31, and you don’t need to be representing any organization.

 

[MaudSTL]

…his diagrams had some sections of the pool deck fully collapsed minutes before the building, and my feeling is that would have lessened the catenary pull on the building columns and so eased their stress.

Sorry, I haven’t been staying caught up.

From a witness statement perspective, a two-stage deck collapse doesn’t work. The Vazquezes drove into the garage, parked (I still have not found out which space they parked in,) walked to the elevator lobby, heard loud cracking sounds, and got into the elevator just as the deck collapsed at about 1:15 AM. They have never reported seeing any evidence of fallen concrete in the garage in the minute or two before the collapse.

The loud crashing sound that Security Guard Shamoka Furman heard in the lobby and the Nirs heard in 111 occurred at 1:10. Because the Vazquezes saw no evidence of collapse, could the 1:10 sound have been rebar failure at a column or at the south wall?

Note that none of the witnesses talked about banging or crashing sounds in the five minutes between 1:10 and 1:15. I doubt that anyone has asked the witnesses what they heard in those minutes.

 

[MaudSTL]

From the Pulitzer Prize winning Miami Herald, Lawyers in suit over Surfside collapse reveal staggering legal settlement: $997 million. This is just the insurers. The sale of the property will bring it over $1B. The security company Securitas paid the most.

It will be interesting to learn NIST’s findings someday…the Miami Herald states the failure of the connection of the south perimeter wall triggering the deck collapse as a fact.

One of their reporters called me up this week to tell me that the Miami Herald timeline deviations are insignificant and must surely be the result of expert advice they have received from people they have hired, as opposed to actual witnesses describing their lived experiences.

 

[spsalso]

Reporters aren't too bright. The exception might prove the rule.

spsalso