Miami Beach, Champlain Towers South apartment building collapse, Part 04 49

[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

SF Charlie
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[jbourne8]

Odd, that 2020 budget report doesn't seem to be in any of their public docs on either site. Is there a link to it somewhere?

There's also one thing I've been a bit curious about, and I haven't found a good explanation for it. I'm not a structural engineer at all, but I always assumed that the columns in the tiktok video were what initiated the collapse and not the columns that are circled in blue here:

I think that we might have misunderstood some crucial bits of those videos at the start of the thread.. which is pretty understandable because they're hard to interpret cleanly. The blue column (78 + 80) theory seems to mostly hinge on the surveillance camera footage from next door. But if you assume those top center lights that are on are from the 9th floor and that it hasn't fallen much when it starts, the angle they are at hints that they are actually level with each other in the first frame. A few milliseconds later the end under column 27 starts to drop much faster than the rest of the building. This is easiest to illustrate with a bunch of parallel lines, but only the still standing structure can really be trusted that it's level. Because of how far away the camera is, you can sort of use what you know about point perspective drawing and the top floors to see what level would be there.

All of these lines are parallel with each other and only use the top floors of the still standing building for reference on the angle of the line:

What actually first got me thinking about this was the ring video from 711. In the video you can hear a noise that woke it, and then a large box gets flipped to the right, and the popcorn ceiling that's probably raining down starts to lean to the right too. A wall starts to lean in the kitchen too, but I'm not sure how to interpret that part really. This pic is taken right after the second snap in the video, and it seems like the room is already leaning significantly to the right at this point if the ceiling is falling straight down. Something like this:

This angle also matches up very closely with the angle in the surveillance camera in the second frame I posted. Right after that the entire table starts to slide to the right within the room, and then the camera slides slightly to the right and mostly to the back of the room (south) in the very last second. I think at that point we're actually watching the building collapse from the inside and it cuts off around when the power cuts off. Video will have a slight delay when they're uploading externally, but it was probably around 100-500ms before it lost power (most of the US is reachable in around 120ms or so). I know some people think the video starts at the second boom, but based on statements from survivors that was actually a few minutes before this video starts and I don't think it ever picked it up. Or if it did, it's most likely in another video clip.. these things tend to end the clip within 5-30 seconds or so of the movement/sound ending.

With the view we saw of the inside garage too, I think this might be what's going on with the rubble in the tiktok video:

The object on the ground definitely seems to the be the only thing painted white, and the planter seems to have a bit of green on it. If you create a parallel line using most of the vertical lines in the pic (red line) it also looks like column is leaning a bit to the right towards the top of it, and the top looks broken off.

But my question is this.. is this possible? And could this one column failing have caused a collapse of the entire rest of the building? It seems like it could have caused serious damage to column 27 because of how that horizontal beam on the ceiling was tying them together. And with how skinny all of the columns are, and how soft they say the concrete is, it seems like that alone could have caused a complete collapse of the building. Just seems to make more sense than column 27 failing and the ones in blue as well, with the column between them seeming to collapse after the building starts to fall (because of how slowly that section falls compared to the rest of the floor). But perhaps I'm missing something?

Of course, this still doesn't explain why the column failed in the first place.

Videos I mention here so you don't have to go dig them up again:
Surveillance video of collapse from next door:

https://www.youtube.com/watch?v=KR29pLccutY

Ring video:

https://twitter.com/_rosiesantana/status/1407970894924992512

Tiktok video:

https://www.tiktok.com/@adrianitacastillero/video/6979296632919706886

2020 view of the inside of the garage:

https://www.youtube.com/watch?v=w4rGWH7aDJc

 

[1503-44]

Maybe its just me, but I dont see any hint in any of the videos that show a top to bottom failure progression. No pancake from roof to basement. I only see a more or less monolithic drop, the kind precipitated by loss of lower support. The upper levels visible in the videos all dropped at the same rate, as a unit. Any pancaking occurred at the bottom. The lower column(s) failed first, perhaps from the pool deck pulling them out, or maybe from compressive overload of lower columns from excessive roof loads, but do not really believe that is likely, unless you consider the extra roof load became enough cause to buckle lower columns, but only after they lost the lateral stability that was being provided by the ties to the deck structure. I just can't see any top to bottom progression.

 

[Sym P. le]

jbourne8 (Computer), excellent work on reinterpreting the videos. The garage is still a mess but i like your idea of the horizontal component. That would have been cast as one piece with the floor slab above it so I suspect that the area to the right is the underside of the pool deck sloping down to the garage floor and impeding further view into the parkade.

 

[Sym P. le]

1503-44 (Petroleum), I agree, the failure was from the bottom up or an inverse pancake.

 

[jbourne8]

1503-44 - I agree with that too, I think it started from the basement. The numbers I reference are the parking space numbers, not apt numbers btw.

Sym P. le - Thanks! Yea, another interesting thing that 2020 garage tour showed us is how well lit the garage was, so it seems like the dark end must be collapsed back there.. or at least the lights are all off which makes it impossible to see. Only the lights under the building seem to be on.

 

[1503-44]

OK. With all the banter about drilling anchors for window washing and falling balconies, I thought others might be seeing that differently. Not to say that the loads from bobcats and roof materials didn't have an effect at lower levels. It all adds into the total. Just that I couldn't envision the roof or upper balconies collapsing first into those below.

And I do think the loss of just one column could certainly do in that whole side of the building, if the design was anything like I've done previously. I haven't done much commercial and residence work, only the TX A&M football stadium and gymnasium actually, but I wouldn't expect those types of structures to be more conservatively designed than chemical plants and refinery buildings and they would definitely not withstand the loss of any one column and survive in any recognizable form, so yes, losing one column would most certainly be enough to collapse the adjacent ones, then 2 more ..and so on.

Pardon me if all that has already been accepted by the majority. Its been a long story with more than a few forks, so I'm just trying to get a concensus of where the collective wisdom stands at the moment.

 

[JimmyP80]

Can't seem to quote anyone , (is there supposed to be a quote button?) so I applogise if it looks like i'm ignoring peoples replies.. i'll reply when i work it out!


I have a question though.. Regarding the change in slab level at the main structure perimeter that was mentioned eariler by various posters, and is present in this simulation:

https://www.youtube.com/watch?v=hynHiWE818

I can't see this in the garage inspection video? am I missing something?

 

[1503-44]

Quote button is two places to the right of Smiley.

 

[GPR_Tech]

It's hard to see the [Pool/Outside SLAB Elevation change] but look at the conduit go up at 45 degrees... it changes right there.
.

.

 

[1503-44]

As far as initiating from below, TeleMundo's interview with Adriana I think is rather convincing.

https://www.youtube.com/watch?v=I2F7Rv57L1k

They were probably the best eye witnesses to the moment and their focus was directed only to the lower level, rather than to any action above. Yes, they are at ground level, but even though, if something was breaking above, surely they would have noticed and focused on that. At 01:24, Adriana says she saw the "roof" collapsing, then the pipe breaking and water pouring down. She means the roof of the parking area, since she tells her father that she will stay there [to record] because "here something will happen". That area is where the pipe broke and water falls, so she is not talking about the building roof above. Then not seconds later a black cloud was coming and they ran for their lives.

 

[tmwaits1]

One thing that we know pretty well from eyewitnesses and video next door is that the slab between the pool and the building failed first. This is also corroborated by the site photos of the damage (see below). An excellent video of the probable collapse sequence is on youtube Link. The photo below shows classic punching shear failure of the slab at each column. A quick calculation of the punching shear demand vs capacity for this slab would confirm this apparent design flaw. If the original design calculated this wrong, it is likely that there are other aspects of the building structure where the design was also miscalculated. If there were design flaws throughout the building, it would help explain why this was not a more localized failure.

 

[LionelHutz]

Is it just me or does there appear to be some sagging near the edge? Is that normal?

That just looks like the sand layer to me.

 

[bones206]

That deflection is towards the center of the photo.

Of two general types, that would be “pin cushion” distortion, rather than “barrel” distortion.

A showing that barrel distortion is inconsistent with the camera would prove the point. And I’m pretty sure a phone camera distorts away from the center, in the barrel shape.

As someone else mentioned, the pipes in that video are straight, so it cannot be a lense distortion of the beam only. It’s either service load deflection or it was cast that way in deflected forms. If it was already a stressed, hard working beam with a lot of tributary dead load, then you consider possible rebar corrosion, soft concrete and perhaps even one of the main flexural bars was cored through by Morabito’s subcontractor… then I could see this beam failing and being the triggering event. I hope they can get surveillance video from those cameras in the garage.

 

[waross]

Quote Button.
First Click: "Who?"; Add Title.Second Click, (Click OK): Paste Quote.
Example:

(is there supposed to be a quote button?)

Bill
--------------------
Ohm's law
Not just a good idea;
It's the LAW!

 

[Teguci]

If only we knew someone who could do a quick punching shear calculation for these 12x16 columns supporting a 9 1/2" 2-way slab reinforced with #5 on top...

phi-Vc = 140 k, 1.4 x DL (9 1/2" + 7" concrete on 20 ft x 20ft area) = 115 k - so no. A failure somewhere else added load to these columns until they failed suddenly in shear. Testimony states that noises were heard above rooms 111 and 411 that woke them. Then 111 saw the plaza slab fail suddenly.

 

[Spartan5]

Testimony states that noises were heard above rooms 111 and 411 that woke them. Then 111 saw the plaza slab fail suddenly

I think you mean 611, not 411. And if I recall correctly, 611 just said they were woken by noises from outside (not above) and got up to close the balcony door.

 

[sgw1009]

Several had asked about saving evidence from the office before the remaining portion was demo’d without understanding the interior lobby slab had also collapsed into the basement in that area.

This is the only reference in the entire thread to the lobby floor collapsing. Just curious what is the basis for that statement?

Unless the layout of the first floor had been repurposed since the original plans, the Security Office was immediately north of the elevator shaft, which survived (presumably).

The area to the right of the blue line had collapsed, but the area to the left of the blue line still stood. The Security Office should have still been there before the demolition.

Also, viewing the east side of the standing portion, the back of the Security Office would have been somewhere in the area of the red circle. This area still appears to be intact.

So hopefully the security footage was retrieved before the demolition.

 

[GPR_Tech]

How do you "add Title"?
[Hint I copy & past, but that wasn't clear at 1st.]
Is there an other way?

 

[NOLAscience]

It’s either service load deflection or it was cast that way in deflected forms.

I was about to suggest the same thing. My guess is that the wood forms deflected a bit when the concrete beam was poured. If that beam were actually deflecting under service load, it would have cracks in the lower half.

 

[Santos81]

This is the only reference in the entire thread to the lobby floor collapsing. Just curious what is the basis for that statement?

Unless the layout of the first floor had been repurposed since the original plans, the Security Office was immediately north of the elevator shaft, which survived (presumably).

The area to the right of the blue line had collapsed, but the area to the left of the blue line still stood. The Security Office should have still been there before the demolition.

This is the view from garage parking space 99 (under the plaza level drive) facing NW. The collapsed portions are from the lobby level (note the visible dumpster and trash chute) as well as a portion of the ground level driveway.