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
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[IanCA]

IanCA, Understand not many bars but if also a N-S or E-W construction joint in area, coupled with chemical reaction in area, things get very interesting in this area.

And missing beam from design change

@thermopile, I completely agree, that's why I removed the word "only" from my post. It is all too easy to neglect, or downplay, this part of the structure because it wasn't taking the building loads, "there was nothing under that wall", "the wall wasn't taking any load", all it has to support is 4-foot high CMU wall, it is easy to understand why people think this area is insignificant. Plus that area was damaged when the 8 foot high pool deck privacy wall collapsed during hurricane Wilma

Penagwin (Computer)14 Jul 21 18:29
Just found another video I haven't seen mentioned, it's from a video of a Hurricane Wilma in 2005.

https://www.youtube.com/watch?v=X4BwnI0VyPM

Around the 3:30 mark there appears to be a shot of the pool/patio deck and it looks rather torn up. Can any structure/civil engi tell if this is cosmetic or if it would have prompted repairs, etc? It looks pretty bad to me.

@IEGeezer,
Looking at that image I'm not sure what material strengths to put in for my calculations. Any suggestions, please? I see one piece of bar that pulled out, it looks as though the rest, were missing, already failed or sheared off due to embrittlement.

 

[sgw1009]

It was back on August 20 (in Thread 11) that IEGeezer (Industrial) theorized that the initial failure point was Column K13.1

Based on the measurement of the weight of the planters I think that the probable point where punching shear first developed was column K13.1, followed by K12.1 as shown on the attached Sheet titled Level 1 Demo Plan and identified as Sheet D2C-1.0 from the Morabito bid documents referenced in my prior post.

 

[FJBnomics]

sgw1009 (Computer)6 Feb 22 18:36
It was back on August 20 (in Thread 11) that IEGeezer (Industrial) theorized that the initial failure point was Column K13.1

I am having a hard time seeing the deck slab failing in punch shear first at an internal column, due to Building Integrity’s tight jump rope grid analogy of rebar grid in slab.

Unless there is a shear of rebar on all sides of column at same time.

 

[Sym P. le]

I don’t see how we avoid considering the effect of South Planter distributing loading on slab ...

Because the planter is continually supported by the wall and has no ability to impart significant bending moments to the slab.

 

[Sym P. le]

... the box identified by the speech bubble ...

Nice catch!

If I can draw an analogy to wood framing, a piece of lumber is not wasted because of a knot provided that certain limitations are met. Similarly, holes can be drilled through floor joists provided that certain limitations are met. Also, an opening for stairs in the floor diaphragm of a house is typically provisioned with double joists on either side and a double header on each end. Likewise, the duct opening in the slab is provisioned with additional rebar to accommodate the loss of continuity. Thus it is an interesting anomaly, given its location, but not a smoking gun. It does help to isolate the two failure regimes, zones A and C, but note Geezer's identifying that the concrete in zone A would be thicker than the concrete in zone C which would also isolate the two regimes.

I need a lot more help before I believe the corrosion driving the collapse theory. (Edit: along the south perimeter wall)

 

[Sym P. le]

What if 3 tons were applied to a single quadrant or 4 tons to half the surface?

 

[FJBnomics]

Because the planter is continually supported by the wall and has no ability to impart significant bending moments to the slab.

Sym P.le, thanks for feedback. I can see that loads near the south wall do not contribute to increasing bending moment on say I or K columns as much, and mostly add shear load on wall. However, at the Zone A and B transition area there does appear to be a change of state if your will in the concrete. The Core Sample also indicates this 'peculiarity' at bottom of deck slab.

I did some reading up on pool chemicals, and how they control the pH and the chemical effects on concrete from the Portland Cement Association.

I will attach that pdf, if anyone else wants to read it.

Even a Blind Squirrel gets an acorn every now and then.........

[URL unfurl="true"]https://res.cloudinary.com/engineering-com/image/upload/v1644187678/tips/is536-types-and-causes-of-concrete-deterioration_umzezc.pdf[/url]

 

[Sym P. le]

Concrete and rebar can suffer a lot of abuse by chemical action but deterioration does not dictate complete failure.

 

[Sym P. le]

A quick calculation shows that for a 25 foot span to pull 8" off a support, the far end would have to drop almost 6 feet. To borrow Geezer's catenary sketch, this would be easier to accomplish if a line of multiple columns punched through as opposed to only the closest one and suggests that a broad area of punch out was required to pull the slab in zone A off the south perimeter wall. The lowering of the lobby parking into the garage level may have been graduated by a succession of failures rather than all in one go.

Edit: In keeping with this, we do not know if witness accounts reflect one or more, or which event in a sequence.

 

[Sym P. le]

a rough and ready stereo 3D garage image with one frame from the USA today video and one from the TikTok video. Hint: concentrate on the far items, not the gate.

I'm reupping the video's in case anyone can improve on this. Attached USA Today video:

 

[Sym P. le]

Tiktok video

 

[FJBnomics]

Sym P. le, I confirm your 6 foot drop at far column. I came up with 5.74'. But then I decided what if break in slab is at 10 feet from wall. When I did this, it only took 3.16 to 3.6' range drop at break to pull slab off wall. If slab has two opposite breaks, seems the drop would be even less to retract slab from wall. A V-shaped Fold if you will as seen on after collapse damage around rear of DuraMax

 

[MaudSTL]

…we do not know if witness accounts reflect one or more, or which event in a sequence.

Although there is a gap of about five minutes between the first crash heard on the first floor at 1:10 (which apparently did not cause noticeable debris in the garage) and the deck collapse at ~1:15, the witness statements we have in the Timeline do not describe seeing or hearing a deck collapse sequence. They all describe hearing a single, very loud crash when the deck collapsed at ~1:15, rather than a multi-stage deck collapse.

 

[zebraso]

a rough and ready stereo 3D garage

And don't forget to look cross-eyed until you see three images with the one in the middle being 3D. There is a deleted post which I missed. I will say there are some planters there but that's about it as far as recognizable items. Albeit the parking deck would not be that far east. right? Is the point what can't be seen? At one point it was claimed by someone that car(s) are visible along the perimeter south wall. I think I felt that was true at the time. But that's a lot of staring cross-eyed, and it hurts after a while.

 

[Sym P. le]

I threw it up in case it triggers some creative brainstorming.

 

[zebraso]

Got it. I am thinking single seminal loud crash heard by pool attendees across the street from garage entrance. After that thought, I don't know in light of the south wall failure theory. It probably put things into focus but it's not coming to me. This theoretical wave progression could have happened so very quickly. That's a problem.

 

[FJBnomics]

 

[zebraso]

Could be something reflective bifurcated by the gate. Another thought I had which probably isn't worth much is that if 13.1 punched first before the section along the wall then you would not be able to see any cars along the back wall. And there was a general feeling that I recall when these images were being looked at ad nauseum, that the back wall and car or cars were visible. Of course this suggest that the pool deck area had not completely collapsed yet when the tic toc video was made. Because I can't quite imagine how you could see autos along the back wall if the pool deck was as low as it is in the final collapse. But that's a lot of unconfirmable crap too.

 

[FJBnomics]

If tail lights, where along back wall is that auto? Was someone in that auto or could initial rubble fell on car and triggered lights to come on due to impact with auto? Does this suggest collapse started from West side of that auto and perhaps North of that auto?

 

[Sym P. le]