Miami Beach, Champlain Towers South apartment building collapse, Part 15 32

[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

SF Charlie
Eng-Tips.com Forum Policies

 

[Sym P. le]

If the initial failure begins at the southern wall, by the deck detaching from the wall...

There has to be a mechanism that allows for the slab to be pulled off of the wall. Either the slab edge moves north or the wall moves south. The wall does not move south so the slab has to move north and the only way for that to happen is for the collapse to initiate further north in the parking area around the columns.

As I've further considered your previous images, I've realized that there are three failure modes along the southern edge and I propose the following:

Zone A: Slab is pulled north off the south perimeter wall​

Zone B: A tab of the greater slab fractures along the edge as it is pulled simultaneously off the wall and laterally to the west as it follows zone A​

Zone C: The slab breaks cleanly along the perimeter wall but does not pull off of the wall​

Note the diagonal scratches in zone B:

 

[FJBnomics]

My understanding from IanCA’s posts was punch shear at I14.1 could have started the deck ride?

 

[Sym P. le]

He also proposed the slab detaching from the perimeter wall as the initiation point, which is what I was responding to.

 

[FJBnomics]

Sym P.le,

Ok, understand. I think I14.1 punch shear more likely, in agreement with your post.

 

[Sym P. le]

Hopefully I've helped to clarify what was happening at the south perimeter. If so, it was a useful exercise.

 

[FJBnomics]

Sym P. le, Yes your excellent posts explained why we have 3 different zones of slab failure, and the pulling diagonally of middle section clearly supports first movement being parking deck, and it cascading from there. I think you and IanCA explain the linear progression of failure from somewhere around I14.1.

 

[MaudSTL]

To correlate the deck collapse sequence under discussion to the witness statement timeline, after over two hours of banging sounds heard in 111, the first big crash was heard at 1:10 AM by the Nirs in 111 and by Security Guard Shamoka Furman in the lobby. Is it conceivable that what they heard at 1:10 AM was the the rebar failing as I14.1 began to punch through the slab? If so, could this occur without visible collapse in the garage?

The reason I ask is because the Vazquezes have said nothing looked out of the ordinary in the garage when they parked in the garage and walked to the elevator just before 1:15 AM. Unfortunately, we don’t know what space they parked in, so we don’t whether a small local collapse of a delaminated ceiling layer, if one occurred, would have been within their line of sight.

We do know the Vazquezes heard unusual, loud cracking sounds in the seconds before they got into the elevator. To relate to the theory under discussion, could this have been the failure of the Zone A connection as the deck collapse began?

The Vazquezes were ascending to the first floor when the deck collapse occurred at about 1:15 AM. So the deck collapse occurred within a few seconds of the loud cracking sounds they heard just before they entered the elevator.

 

[IanCA]

There has to be a mechanism that allows for the slab to be pulled off of the wall

Thanks very much for taking the time to add additional notes.

I agree, and I have attached an image below showing what I believe to be one possible explanation for how the deck detached:
This is a sectional elevation through parking space 45 looking west.

I believe this satisfies all of the available evidence.

 

[IanCA]

To correlate the deck collapse sequence under discussion to the witness statement timeline

Thank you very much MaudSTL for taking the time to summarize the sequence of events in your post at 20:34 and for relating events to the sequence under discussion at 03:11. It is going to take me some time to think through your comments and to try and line things up in time. As you can see in my post at 06:07 there are several places where rebar and concrete could have been slowly failing and causing the banging sounds heard for two hours before 1:10am.

 

[IanCA]

Zone A: Slab is pulled north off the south perimeter wall

Yes, correct, but there is one slight adjustment required to your plan view, please. Zone A should also encompass parking spaces 46 and 47, and is centered on column I14.1, along with the blue ellipse being centered on column line I.
Thanks again.

 

[Jeff Ostroff]

Here is the article from the Miami Herald yesterday

https://amp.miamiherald.com/news/lo...7NF4ihZ2-kmPra8qTVOVFOs7fYxug_ofC4abeu6_Gd8_E

The Herald article is showing actual photos of the just-added shoring poles that Champlain Towers North Condo, the sister building to the collapsed condo had installed last week. I will be doing a video on this in the next couple of days, I'm still working on the 2nd Pittsburgh bridge collapse video. This to me is a major shift in thinking about the current safety of the surviving sister condo. As you know engineer Allyn Kilsheimer had mentioned back in July that he thought the building was safe enough that he would allow his kids to be in it. So now here they are putting up shoring poles around the columns in the garage so they must know something you don't just add a dozen shoring poless around a column for no reason.

 

[Optical98]

So CTS felt they needed to relocate the majority of their parking and thus applied for a permit... as far as I remember there wasn't a number of spaces listed on the permit application. If it was only a limited number of spaces like CTN, they should have just bypassed the permitting process and had Morobito shore up parts of the garage?

This is of course guess work as neither party is speaking atm. But just from the paperwork we've viewed.

 

[MaudSTL]

It is going to take me some time to think through your comments and to try and line things up in time.

I greatly admire your thorough, logical approach. To simplify the correlation of your detailed theory with the timeline, here is a screengrab of the key perceptions for your convenient reference. I understand that we cannot truly know how to correlate all structural failure details with the witness statements, but there does need to be some logical connection between the events proposed in the structural theory and what witnesses say they perceived.

Thank you so much for your efforts.

 

[FJBnomics]

I greatly admire your thorough, logical approach.

Ditto, Ditto, Ditto........

 

[Red Corona]

That shoring in CTN clearly indicates that someone (presumably having seen the survey of the concrete/rebar condition there) is worried about punching shear. Not in the place that you are now suggesting was the trigger though (near the southern perimeter wall).

But iirc (from one of the BI videos I think) the plans of the way the columns support the deck and ground floor parking area are different and that part of the CTN deck is not as poorly supported as it was in CTS.

 

[FJBnomics]

Along Sym P. le's Diagonal movement of deck, would this portion of broken slab also indicate the diagonal movement?

It would seem it takes punch shear of a column further from South wall than planters, to pull the slab totally away from South wall?

I can see how a break under inner planter lifts the end of slab, but I would expect to see a horizontal crack in the step part of the edge of slab where the deck slab caps off the sheet pile. See IanCA's 1 Feb 9:04 post diagram of as built conditions.

Back to image, does the stamped concrete area indicate we have back and forth lateral movement like the card table situation, prior to punch shear or as columns are punching and creating load transfers?

Or was stamped concrete pushed up in accordance with IanCA's planter fail diagram?

Or is raised circled stamped concrete support IanCA’s planter failure even more. Being slab in circle ️ is pulled North first by drop at planter near South wall?

 

[LionelHutz]

That piece was pushed up by the column that punched through. Trying to apply more meaning to that seems like a fruitless endeavor.

 

[FJBnomics]

 

[Reverse_Bias]

Here is a view that shows the the entire part of the deck that detached from the wall.

 

[Optical98]

The wall behind the parking area showed damage on the opposite side as well.