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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[IanCA]

Also see slide 6 in the following presentation:

Thanks very much, SFCharlie. Incidentally, I noticed earlier that slide 2 of that presentation does not include the Jacuzzi. I sent a message to NIST to let them know.
And the pool profile is wrong.

Previously posted by aspiring investigator

I think they copied that sketch.

 

[Sym P. le]

next lesson "coloring within the lines"

My follow up post aged well. LOL

 

[IEGeezer]

@Murph 9000 (Computer)

Thanks for that. I was really struggling. I thought the parking space numbers were marked on the sides of the columns, but I found in the garage video that the odd numbers on that side were painted on the sides and the evens were painted on the face of the column (facing the parking spaces), so if the last digit was a 6 (it's really blurry), then the column I marked with a red circle would be the one between parking spaces 116 and 117 with 116 painted on the face or south side of the column and 117 (not visible) painted on the east side.

 

[Jeff Ostroff]

I missed the deadline to register for the NIST live event, does anyone know if there will be another livestream tapping off this one? It tcan take them weeks to upload a video to NIST web site after their meeting

 

[FacEngrPE]

The videos from the live stream are up
The National Construction Safety Team (NCST) Advisory Committee, June 14-15, 2023

 

[SFCharlie]

slide 2 of that presentation does not include the Jacuzzi.

I Think the point here is that they were comparing the original design against the code at that time, not the as built design.


SF Charlie
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[dik]

Something that appears to be missing from the NIST reporting is holding the local governments responsible and compelling them to enforcing the remediation reports.

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

-Dik

 

[kevinsnn]

SFCharlie, i think they are doing as built check as in talk on deck slab that the top of slab rebar cover was 2 " rather than 0.75" design cover and that it would lower the capacity alot for punching shear. I know that here was talk here should be larger cover on exterior slab because of salt sir from ocean.
But why no discussion about multiple story building and why it fell down even if deck slab could started it?

 

[SFCharlie]

But why no discussion about multiple story building and why it fell down even if deck slab could started it?

First i am assuming they wished to present what they were sure of, not what they were not.
Second, I think we see hints in what structures that they are going to test in order to find out.

SF Charlie
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[IanCA]

I Think the point here is that they were comparing the original design against the code at that time, not the as-built design.

Yes, I agree and can appreciate that, but the discrepancy isn't noted on the slide and wasn't explained in the presentation. It seems to be a rather academic exercise to study a design that is known to be significantly different from the design that collapsed. Is it fair to say that since the Jacuzzi and pool survived the collapse of the pool deck it should be possible to study the design with those features accurately modeled? That was not stated as an objective in the presentation. This also highlights the importance of retaining copies of the drawings which were approved for construction. It sounds as though NIST will be making some recommendations in that area.

 

[MaudSTL]

For anyone interested in NIST’s thoughts on a trigger for the collapse, there is a discussion at about 12:00 before the end of the last video. Gary says concrete failures are more like timber failures than steel failures. He doesn’t think a specific CTS failure trigger is likely to be identified. Basically, he says that a combination of design, construction, and other factors made failure inevitable, and that CTS failed when it did because so much damage had accumulated over time and time had run out. My words, not a quote.

They bring up the Piper Row car park collapse as an analogy. It famously failed through punching shear. Corrosion was central to its failure, but doesn’t necessarily seem central to CTS’s failure.

https://www.building.co.uk/hse-word-is-out-on-pipers-row-car-park-collapse/3032553.article

 

[MaudSTL]

But why no discussion about multiple story building and why it fell down even if deck slab could started it?

In the third video, they talk about the contractor who did the calculations for the deck and say that they are still working on their calculations for the tower. In the slide it says “Tower work in progress.” So I think in six months we will see the results of those calculations and get more details on the tower’s flaws. The theme of this meeting, after the presentations of “this is what we are working on and how we do our work,” was “what we know about the deficiencies of the pool deck, which collapsed before the tower collapsed.” This meeting did not even mention how the pool deck could have caused KLM to buckle and bring down the tower.

 

[FacEngrPE]

The link MaudSTL posts is a good summary, however the cited summary contains an incorrect link to the HSE site.

Pipers Row Car Park, Wolverhampton - Quantitative study of the causes of the partial collapse on 20 March 1997

The final report in two parts

https://www.hse.gov.uk/research/misc/pipersrowpt1.pdf

https://www.hse.gov.uk/research/misc/pipersrowpt2.pdf

Citation:
Pipers Row Car Park, Wolverhampton
Quantitative Study of the Causes of the
Partial Collapse on 20[sup]th[/sup] March 1997
Jonathan G M Wood

 

[IEGeezer]

Comments of Jose "Pepe" Izquierdo Encarnación (former President of ACI) beginning at 30:39 of "Conclusion of Champlain Towers South NCST Investigation Progress and Next Steps" (talking about why the top reinforcement ended up with 2 inches of concrete cover instead of 0.75 inches):

Is because they use the guides for the final top screening of the slab. Then they use the guides inside the slab. So the only way of allowing that to happen is to lower the upper reinforcement. The guide should be above the slab and they have a screening squidgy that has like arms so that they can fly above the guides, but it's too much trouble so they just put the guides inside and they can use a flat screen and in order to happen that they have to push the reinforcement down. And that happens. I've seen it hundreds of times. Unfortunately. Bad construction practice.

Can someone find a picture of what he is talking about?

 

[FacEngrPE]

Jose "Pepe" Izquierdo Encarnación was probably misquoted. In the quote I suggest replacing screen with screed.

There are a number of approaches to screeding, Important variables are local practice, the skill of the mason, and the flatness specification of the floor.

https://youtu.be/mN2wmpPEurA

 

[Sym P. le]

My take on the comment is that the rail which the screed is pulled across has a certain depth. If you implement the rails above the finished slab, the screed has to drop down and fit between the two parallel rails. This is not consistent with many/most screeding methods which use a straight edge that extends beyond the rails on either side.

 

[Reverse_Bias]

WJE said the deck did meet code at the time even though the code was probably inadequate. NIST is saying most of the deck was never anywhere close to meeting code. Anyone know why there's a discrepancy?

 

[jerseyshore]

I've been following along only intermittently, but can anyone summarize what the current thoughts are from the investigation and/or prevailing theory?

I, and I'm sure a lot of other lurkers, would really appreciate it.

 

[dik]

Possibly causing it to be underdesigned, the 2" cover is more appropriate for the environment.

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

-Dik

 

[IEGeezer]

The WJE illustration shows 4 sections that collapsed in order from 1 to 4. I will ignore the pool deck for now. Please see the 2D NIST debris pile elevations.

(I am also attaching a similar 3D diagram.)

On the 2D diagram, the lowest elevations (i.e. the fallen pool deck) are dark red, while the surviving pool deck elevation is light blue. The next highest elevations are green, then yellow, orange and finally a rusty red. There is very little green within the footprint of section 2, which is mostly blueish.

It would appear that most of the debris from section 2 fell into the footprint for section 3. The first conclusion is that section 2 fell into section 3, thus causing its collapse. I am proposing that the debris from section 2 was subject to an unbalanced moment caused by the uneven collapse of the section 2 columns. The resulting moment then caused most of the section 2 debris to fall 20 to 40 feet further north than if it had fallen straight down.