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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[Sym P. le]

We know that Nir's patio furniture was in the garage when the ramp video was taken. We don't know how that relates temporally to any prior events. Because if that info exists, we haven't been told. Longobardi would be a good source for temporal information, i.e. was Nir's furniture already in the garage when you ran through or did that portion of deck collapse after you left.

 

[Sym P. le]

I apologize for not keeping in line with the discussion, I'd like to itemize the column references but I got distracted.

So I bounced back to the garage video interpretation and came up with the following. The green line represents underside of fallen slab while the shading represents slab thickness. The dark areas beneath the green line are shadows where the fallen slab does not rest flush on the garage floor. On the left side of the image, the slab drapes over the vehicle. This implies a clean deck slab break at the tower perimeter, as expected.

The second image is an unmarked copy of the first. They are taken from the June 2022 NIST presentation with the contrast/brightness pushed.

P.S. The missing column might be partially visible as the light patch at center-top of the "C", otherwise obscured by the draped slab or planter sections.

 

[Murph 9000]

Yes, I think the pool deck collapse most likely extended to KLM 9.1 (the southern wall of the tower). M9.1 is the bright column in roughly the middle of the image, with the yellow base. I said at least KLM 11.1 above, as the greater volume of rubble a little further back from M9.1 can only really be interpreted as total collapse. Closer to M9.1, it certainly looks to me like the slab is fully collapsed, but I'm allowing for other interpretations.

 

[Sym P. le]

I'm curious about column K15 (I mistakenly referred to it earlier as K14.1). The connection rebar on its north face is not readily discernible in most images so it was either pulled down through the collar ties or snapped off. Either way it is unique in its failure where most other pencil tops just had their connection rebar bent downwards.

 

[MaudSTL]

I am still searching for some explanation on how Shamoka got from the lobby to the parking level.

Not long after the collapse, Raysa Rodriguez posted a GoFundMe for Shamoka that was taken down quite some time ago. It said that Shamoka first climbed out of the valet window onto the ruined porte cochere. She couldn’t see a way to get out from under it, so she climbed back into the lobby and escaped from the lobby to the garage, during the process injuring herself.

Because we see in the police bodycam video of the porte cochere and the parking deck area that the lobby glass was intact, Shamoka’s only other lobby exit would have been the door to the pool deck. She may have tried to climb down the rubble to circumvent the porte cochere, which would explain how she was injured.

When Shamoka encountered Ileana Monteagudo, Ileana had made it down the west staircase through the door into the garage level and was trying to climb up. Based on Ileana’s comments, Shamoka helped her climb a wall and jump over a chasm, and then helped her up onto the visitor’s parking deck. The first time we see Shamoka in the bodycam video is when she and Ileana are climbing up out of the collapsed parking deck.

Later in the bodycam video we see her on the street.

 

[IanCA]

Although the west staircase survived the collapse, it was functionally blocked by the initial parking / pool deck collapse.

@Murph 9000, thanks for clarifying those details.

When Shamoka encountered Ileana Monteagudo, Ileana had made it down the west staircase through the door into the garage level and was trying to climb up.

@MaudSTL Thanks very much for the detailed description. I hope you don't mind me adding a couple of additional observations here. In the police body cam video Shamoka states that the lady she is with is also injured. I have not heard any reports of what Ileana's injuries were. I have often wondered at what point the pair of step ladders were placed onto the back of the black Chevrolet Silverado. It appears to me that at some point someone stepped onto the cover over the bed of that truck, presumably thinking it would take their weight, but instead, it collapsed.

 

[SwinnyGG]

Has anyone watched the WJE webinar on their analysis of the failure?

Lots of interesting information. Maybe not quite as technical as many of us would have liked, but informative.

Link

 

[Sym P. le]

WJE webinar. Just give them your info and you're in.

This webinar presents very relevant information.

Concrete meets or exceeds specs, notably, deck slab is above spec.
Level 1 slab design is wholly inadequate.
Rebar placement is suspect in two applications. One, slab rebar has excessive cover (i.e. inadequate chairing or sagging during construction), greatly reducing its performance. Two, building column rebar at Beam A connection is displaced and Beam A rebar is not properly integrated with the column.
Corrosion, though excessive in some areas, is not representative of the entire structure. Further study required.
Chemical deterioration of slab is not a significant factor.
Geotech is not a problem.

Punchout is the problem stemming from inadequate slab design and poor rebar placement. Code needs to be tuned up.

 

[dik]

That was an extremely good webinar... I thought it was very good. A couple of comments:

It's been a while since I've done anything large in concrete, but I seem to recall that you require 1-1/2" conc cover to give columns a 2 hr fire rating. 3/4" seems too little. I'm not sure what Florida requires.

With the excessive concrete cover, there would be negligible carbonation, reflected in the lack of corrosion.

Concrete strength was low to marginal. This would have a great effect on the shear and punching shear strength. Reinforcing was underdesigned, it appears, and the reinforcing ratio was small. Concrete strength would have little or no effect on the flexural strength.

-----*****-----
So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

 

[Luceid]

Thanks for the link and highlights Sym. Very interesting.

 

[Sym P. le]

From the WJE Webinar slide

I find the positive bending weakness along the south perimeter an interesting feature. I also owe IanCA an apology for pushing so hard against his theory (part 14 - 6 Feb 22 06:30). It turns out when the structure is analyzed as a whole, the positive bending maximum shifts significantly towards the south portion of the span rather than center span. In fact, it will take abuse from the planter and the parked vehicles, especially a 3 ton truck.

Although I still think the failure initiated from the pool deck, this perimeter weakness could be the explanation for the slab pulling off the perimeter wall in the parking area while transitioning to fracturing along the wall through the somewhat more robust and less loaded pool deck area (three failure zones part 14 - 2 Feb 22 21:07).

I believe Prof. Lehman, who's study was used by Miami Hearld, states somewhere that of various scenarios her team considered, the only one that brought down the building initiated at the south perimeter wall.

 

[Luceid]

Give me some slack on this one because I haven't done anything like this before, but where does the load combination 1.4D+1.7L come from?

 

[Sym P. le]

I'm Mechanical, not ...

 

[Luceid]

No problem Sym, curious what the crowd has to say.

From a quick google search, it seems like this may have been the load factors during the iteration of the code that this structure was designed, rather than the current 1.2D+1.6L.

 

[dik]

Those were the DL and LL factors for concrete at the time, I seem to recall... back in 1965, it was 1.5 and 1.8, respectively.

-----*****-----
So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

 

[IanCA]

I also owe IanCA an apology for pushing so hard against his theory

Gladly accepted. Thank you. In fact, I really appreciate all of the constructive criticism and challenges and the way those suggestions encourage me to think about things from another perspective and to consider other possibilities. I am looking forward to viewing the WJE webinar now that I have access.

 

[IanCA]

Has anyone watched the WJE webinar on their analysis of the failure?

@SwinnyGG, thanks very much for sharing this information. It certainly is an excellent presentation.

There were a couple of interesting points in the question and answer section, for example:
61:12 regarding lateral forces due to suspected catenary action. However, the strength of the connection between the parking deck and the south wall of the basement does not appear to have been studied to justify that assertion. In addition, the diagrams at 41:56 and 43:17 show the remains of the collapsed slab at the south wall of the garage incorrectly inclined against the south wall with the remains of the deck at K15 at a lower elevation.

 

[IanCA]

@Sym P. le, thanks very much for your summary and interpretation.

One comment I have on this point:

Chemical deterioration of slab is not a significant factor.

With respect to chemical deterioration, I can understand your conclusion but what I took away were comments such as (by Matt at 45:05) "We don't under..[stand]" and (by Gary at 63:27) "we did not definitively address its contribution as we would have liked, we did not get to examine as many samples as we would have liked of the pool deck itself."

Personally, I still believe that chlorine from the ocean in the form of salt and pool chemicals played a significant part in the deterioration of the parking deck and pool deck.

 

[MaudSTL]

Am I correct in understanding that NIST denied access to Kilsheimer (for Surfside) and allowed access to WJE (for the condo association?)

If this is so, why would that have happened?

 

[MaudSTL]

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?

Then at 1:15, the punch through progresses rapidly as the deck collapses, crushing cars and unzipping at the south perimeter wall while progressing to the building facade as seen by the Longobardis.

This is a FEMA article I was looking at, showing catenaries in partially destroyed buildings.