Miami Beach, Champlain Towers South apartment building collapse, Part 17 14

[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


SF Charlie
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[SFCharlie]

In San Francisco, they build on top of clay and use friction piles that don't go all the way down to the bedrock, too deep.

The proposed fix to the Millenium Tower is to install piles along two sides of the building's perimeter. That may seem kind of simple, but there is a lot of clever engineering involved to make it work. Fifty-two piles will be drilled along the north and west sides of the tower all the way down to bedrock. Nov 16, 2021

What Really Happened at the Millennium Tower?

Original Cost to Build to Bedrock for Tower Like Millennium Put at Just $4 Million

(The SF does stand for San Francisco)

 

[Sym P. le]

I worked on the demolition of an old retired steel structure that was sandwiched between more recent structures which remained in full use. It was a pulp mill which used chlorine and was generally a hot, humid and corrosive environment. It would not fall down, thus we had to dismantle it piece by piece without causing an unintentional collapse that would affect the attached adjacent structures. It was a bit of a nightmare scenario, but we prevailed with minimum collateral damage.

Take away --> it did not fall down on its own. Rust stains do not equal rebar vaporization. Chlorine on concrete does not equal dustation. For the common good of mankind, who are you people?

 

[Nukeman948]

I worked on the demolition of an old retired steel structure that was sandwiched between more recent structures which remained in full use. It was a pulp mill which used chlorine and was generally a hot, humid and corrosive environment.

And we all (should) know that chloride is commonly added to concrete mixes to allow the mixture to set more quickly and increases its initial strength. Without knowing how much chloride was present and the conditions in this building, both when it was built and through its lifetime, we are only muddying the waters. Some stainless steels react poorly to certain chemicals and conditions while other stainless steels have little to no reaction to the exact same conditions. And the same thing happens with different grades of mild steel. The phrase "correlation does not imply causation" comes to mind here.

Edit: Even the professionals use the wrong grade of steel sometimes. I made some good money from the wrong grade of baffle bolt steel.

https://www.nrc.gov/reactors/operating/ops-experience/baffle-former-bolts.html

[sub]
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[Reverse_Bias]

Using two NIST slide images, it's clear that the x11 stack drops with column lines K and L (I think L leads the way). The whole east wing of the building appears to twist grotesquely as the collapse is initiated.

That twist only amounts to every column in the east side buckling at once.

Also sorry if this has been mentioned, but the higher resolution image solves the disappearing penthouse mystery. The apartment with the light on (1110 I think) tore open and the apartment and roof above it didn't drop until a split second later.

Edit: Nevermind, I think that is a power flash in 1210. The X11 stack and the right half of the X10 stack dropped almost in unison. The roof above is from the back part of the building that fell just after
[

 

[Sym P. le]

... twist only amounts to every column in the east side buckling at once.

A fair comment. The images took some work to scale seperately in the x and y axis. With possible lens distortion and/or reorientation, it's not the purest overlay, however the foreground and background are reasonably stable, so I'll just leave it for people to consider that the lagging structure was rocked when the collapse initiated. And we already know that it was not designed for this type of abuse. Imagine what a nominal earthquake could do.

 

[IanCA]

Even the professionals use the wrong grade of steel sometimes

Thanks for sharing. Those documents raise some questions for me. Please direct me to an alternative thread if there is a more suitable one.

1) I'm surprised the designers couldn't reach a consensus on the grade of stainless steel "Type 347, Type 316, or Type 304".

2) Very surprising the construction is not fully welded internally.

3) "These lock tabs normally retain the bolt heads should they become detached".
Normally, but not always... I looked for a generous radius under the head but couldn't confirm it.

4) "A bolt head or bolt lock tab may detach if the degradation of the baffle-former bolt is significant". It is hard to imagine the forces necessary to cause the bolt lock tabs to become detached.

5) "The results also showed many bolts which the ultrasonic inspection identified as partially cracked retain a significant amount of strength". That is a very weak statement since it is known that the cracks progress to failure and the individual failures progress to clusters. Significant strength relative to what? What is the strength of the cracked bolts relative to the design strength and by how much does it reduce the factor of safety? or safety margin in normal operation and under failure scenarios?

6) Why is there a difference in the rate of degradation between up flow and down flow? Pressure fluctuations? Oscillation? Resonance?

7) "Degraded bolts plus additional non-degraded bolts have been replaced". Why were additional bolts replaced?

8) "Finding no damage to the replacement bolts and [BUT] 13 additional degraded original bolts". The wording could be taken to mean no damage to replacement bolts or original bolts, but I'm sure it means additional degraded bolts were discovered.

9) "The fact that a relatively small percentage of bolts broke during removal". How many broke during removal at other reactors and how was breakage remedied?

10) '“unzippering” as clusters grow'. It is concerning that the failures can progress.

11) "Shortest BFB bolt design [stiffness] with smallest head-to-shank transition radius [stress concentration]".

12) What is the recommended torque on the bolts when installed? What thread lubricant is used, if any? What surface treatment is used on the bolt threads? What is the pitch of the threads?

13) "Progression of random failures to clustering". Surely this means the baffles are deflecting.

14) "The WOG stated that because of the large number of baffle former bolts in the baffle assembly, the failure of a few bolts should not have a significant safety impact. Omitting to mention that as bolts fail additional stress is exerted on adjacent bolts causing a cascading failure into clusters".

 

[SFCharlie]

Using two NIST slide images, it's clear that the x11 stack drops with column lines K and L (I think L leads the way). The whole east wing of the building appears to twist grotesquely as the collapse is initiated.

First, I think you did a great job on this, the fact that NIST changed the aspect ratio to make their slide pretty didn't help.
I've been doing this powerPointy thing for thirty years now so I thought I'd give it a go:

I think I got it pretty close?

SF Charlie
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[IanCA]

Rust stains do not equal rebar vaporization. Chlorine on concrete does not equal dustation

Thanks for sharing your experiences. The problem is that several unexpected conditions caused the partial collapse of CTS and we would like to understand what they were so that we can reduce the probability of similar events in the future. The example raised by Vance Wiley shows that there are conditions involving chlorine that can lead to premature failure of structural steel elements. So we need to explore those possibilities until we can prove or disprove them. For example, in the building you worked on was the steel treated to reduce corrosion and painted? How high were the stress levels on the structural elements? Were the elements designed to tolerate high levels of corrosion over their lifetime?

It certainly appears that the primary cause at CTS is the degradation of the structural steel-reinforced concrete, so we need to understand what was causing the accelerated degradation.

Is that reasonable?

 

[IanCA]

high local humidity from vegetation and pool equipment room fan may have caused condensation to form on that column causing the dust to stick there more than the other ones.

I understand it had rained at CTS the evening before the collapse, it certainly did at Miami International airport. The humidity was high and the temperature was close to the dew point so any cool surfaces were likely to have condensation or be moist. The wind was blowing from the East as usual so humidity from the pool equipment room vent and plants was being blown to the West as usual. My feeling is that any difference between the surface moisture on those two columns was minimal. But the difference in the amount of dust is dramatic, so there has to be another explanation.

 

[Red Corona]

> sorry if this has been mentioned, but the higher resolution image solves the disappearing penthouse mystery. The apartment with the light on (1110 I think) tore open and the apartment and roof above it didn't drop until a split second later

Yes. I was one of the people that was asking that question in earlier threads, based on the apparent lights on in X10 and the lack of a roofline gap. But the higher resolution seems to confirm that isn't the case, that the X11 and X10 stack dropped from the bottom (including the penthouse), and there's no roof gap because something else is obstructing the view of the sky above X10 (the roof level corridor as someone speculated back in an earlier thread maybe? indicating that the front of the building - column line 9.1 - dropped first?).

The other interesting thing from that image is that we can clearly see that the power got cut in the parts of the west wing, and apparently in 611 (that's where one of the survivors escaped from right? did she turn the light off?) but not 1110. Maybe some of you guys with the wiring diagrams can make something of what happened at the bottom of the structure from that.

Edit: The most interesting thing for me at this point is why, apparently, their investigation indicates that the issues were unique to CTS. Other 80s concrete multi level buildings, including CTN with a very similar design and presumably very similar construction materials, remain in normal use. And yet the likely failure scenarios we've been talking about in the last few threads on here - a punch through on the deck or detachment at the south wall - involve substandard initial materials, insufficient rebar, poor slab maintenance and corrosion, not just the thin column design of CTS.

 

[MaudSTL]

that's where one of the survivors escaped from right?

Ileana Monteagudo (611) has always said she blew out her candle of the Blessed Virgin of Guadalupe as she grabbed her stuff and left. But she has not mentioned turning off the lights, as far as I know. Nor has she mentioned turning on the lights after she woke up. She consistently says she woke up and went to try to close her balcony door. So I suppose it is possible there could be a reflection on her window. But the enhanced image certainly looks like she turned the light on.

>>>>Edit: I just re-read some of the interviews with Ms. Monteagudo, and then ran into the GoFundMe her son has put up. This is secondhand, but the son says that when she got to the fourth floor in the staircase, all the lights went out. The fourth floor is also, of course, where she was when the building collapsed. I hadn’t previously seen this in the interviews with Ms. Monteagudo. So apparently, according to her son, she had light in the staircase until the collapse.

 

[SFCharlie]

Edit: The most interesting thing for me at this point is why, apparently, their investigation indicates that the issues were unique to CTS. Other 80s concrete multi level buildings, including CTN with a very similar design and presumably very similar construction materials, remain in normal use. And yet the likely failure scenarios we've been talking about in the last few threads on here - a punch through on the deck or detachment at the south wall - involve substandard initial materials, insufficient rebar, poor slab maintenance and corrosion, not just the thin column design of CTS.

Yes! I noticed that they said they were investigating damage from 87 Park etc., but most of the work displayed focused on the structure as built.

SF Charlie
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[SFCharlie]

My first Giphy, Suggestions encouraged.

SF Charlie
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[MaudSTL]

most of the work displayed focused on the structure as built.

Having sat through most of the NIST presentations, I agree that NIST has at this time a strong focus on defining CTS as-built. They talked several times about the difficulty of calculating dead load in such an old, poorly documented structure. This is why they are requesting the public to provide photos and videos taken over the years, even as they research historical real estate records and photos. They want to gain a better understanding of how unit owners added to the interior loads and when they did it.

Based on their analysis of the concrete, rebar, design, etc. that they hold in evidence, NIST also plans to reproduce and destroy key elements, such as column/deck connections, etc., in a condition as close to as-built as possible. I believe the intent of such studies is to get closer to identifying a trigger.

NIST’s purview is to make policy recommendations on how to prevent similar failures, so it seems reasonable to me that they would do this only after they know as much as possible not only about what fell down but also [pre][/pre]why it fell down when it did. In contrast, KCE doesn’t have to meet the same objective. Their job is to figure out why CTS fell down; they don’t have to make recommendations that will keep similar buildings from falling down.

If you go through all the NIST presentations, you may notice (as I did) that their images seem to place a lot of focus on the K, L, M columns this group has focused on, rather than on the south perimeter wall connection or the gym that Prof. Lehman has focused on. At one point they even mentioned that they look at Internet content. Their database of evidence is going to be massive.

 

[SFCharlie]

Let me try again: (Any way to make it bigger? A better gif maker?)

SF Charlie
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[SFCharlie]

One more time!

There we go!
edit (The "Before" (1st) frame is definitely before the first frame of the twitter iPhone video
edit 2 In the "early" (2nd) frame I'm reasonably sure that the Eastern most portion is not only twisting, but falling also
edit 3 increased brightness in before frame

 

[FJBnomics]

I noticed that there appear to be exhaust fans mounted at ground level along the western edge of the parcel are these for an underground parking?

Posted on Thread Number Uno!

Anybody see a CAP on top of that Exhaust Fan Assembly in those images? Don't see how the air exhausts immediately vertically without a hole in the top cap?

Perhaps Nuke can explain???

 

[Nukeman948]

Thanks for sharing. Those documents raise some questions for me.

The answers to most of your questions would be proprietary information that Westinghouse is not going to release with all their competitors reading along.

[sub]Sorry, I don't have any Powerpointy training so this is the best I can do.
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[sgw1009]

SFCharlie - here is a corrected copy of the first NIST image of CTS. I cannot guarantee that the sizing is exactly the same as your original, but the levels are close to those of the 2nd image, to eliminate the glaring difference in levels between the two images on your GIF animation. Also it is a PNG not a GIF. If you need it to be a GIF, I can do that.

Edit - never mind, I see that you just did the same thing.

 

[SFCharlie]

SFCharlie - here is a corrected copy of the first NIST image of CTS.

Thanks!, Yes that's my point, this image is earlier than the first image in the twitter iPhone vid.

SF Charlie
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