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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[SFCharlie]

Is there an other way?

Not that I know of...
Before I start to reply, while I'm still a the post I'm replying to, I copy the name and time stamp. Then I click on cartoon balloon, Paste, and OK.
Then I highlight just the time stamp in my blossoming reply, copy, and find (control f) and up-arrow in the find box (top of window) and copy what I want to quote, up-arrow again to get back to my reply and paste between the ][ marks. then place cursor after \quote] and reply.
(whoo, sounds like a lot of work to me...)


SF Charlie
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[1503-44]

This clip is from the demolition. [Correction! of a different structure from a 2018]
Workers were apparently under the building while pulling down columns with a dozer winch. MIT grad and a city commissioner are shocked by the continuing negligence. Building Dept Admin won't comment because of the criminal investigation in progress.
In Spanish.
Skip to 00:51

https://www.youtube.com/watch?v=0EzlhBKW018

 

[Santos81]

This clip is from the demolition. Workers were apparently under the building while pulling down columns with a dozer winch. MIT professor and commissioner are shocked by the continuing negligence. Building Dept Admin won't comment because of the criminal investigation in progress.
In Spanish.

That is not footage of CTS. It’s from the 2018 demolition work of 5775 Collins in Miami Beach that resulted in a premature collapse due to negligence.

 

[Spartan5]

See:

https://www.eng-tips.com/viewthread.cfm?qid=442327

for more on the 5775 Collins illegal demolition.

 

[1503-44]

OK. Sorry and thanks for the correction.

 

[Torai]

, and the popcorn ceiling that's probably raining down starts to lean to the right too

What is vertical in the ring video? Maybe not the room. The popcorn stuff will follow the gravity vector, which the real vertical, not the frame of reference of the camera. Note: This sort of camera probably has barrel distortion.

If you mount a wireless camera in a box and roll it down a hill, you won’t see much if the camera is mounted rigidly. Put popcorn ceiling in the box, different story.

 

[Spartan5]

That new footage was pretty shocking anyway. Worker in the street wound up losing his leg and dying.

 

[CE3527]

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.

I don't believe this is correct. This would suggest that failure occurred to the west of the shear wall, although it's pretty widely accepted that the shear wall stopped the collapse. I think what you are looking at in the photo is columns E.1 and E.3 which were further north. In that photo, you can see the beam at E.1 which is a step down from the lobby to the outside.

 

[dik]

I do this all the time... rebar is not terminated at the same location... minimises cracking. I use the same length bars and 'stagger' them.

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

 

[kjm93]

What is vertical in the ring video? Maybe not the room. The popcorn stuff will follow the gravity vector, which the real vertical, not the frame of reference of the camera.

I think that was the point jbourne is making. He is implying that in that video the room is already leaning due to collapse of columns (possibly beam) that should have been visible in the tiktok video.

 

[Santos81]

I don't believe this is correct. This would suggest that failure occurred to the west of the shear wall, although it's pretty widely accepted that the shear wall stopped the collapse. I think what you are looking at in the photo is columns E.1 and E.3 which were further north. In that photo, you can see the beam at E.1 which is a step down from the lobby to the outside.

Fortunately it’s a video with numerous parking bay markers. I may be incorrect in the direction it’s facing, but it’s absolutely west of the shear wall.

https://youtu.be/MmleL6I2T5M

 

[1503-44]

I've been reviewing all the Spanish Language survivor account videos and happened upon the best explanation I have yet to see so far.
Great computer 3D models with critical columns circled. This collapse theory is from the bottom up and that there are no beams in the building above the first floor, which allowed an extra floor to be had for the same profile height as all the other buildings on the street. In Spanish. I'll do a translation later, or if Geezer is around ... his translation the other day was perfect, so maybe he could help out till I get back to it. Gotta run right now.

https://www.youtube.com/watch?v=jGUEwj-Pi54

 

[bones206]

One thing that is useful to estimate sequencing is that wherever we see the lines of rebar ripped from a slab soffit, we can infer that the adjacent slab collapsed first. That should be act as a sort of compass for the investigators to follow towards the initial failure point.

 

[Js5180]

Jbourne,

I’ve been struggling to reconcile the 711 video for the reasons you’ve mentioned. The wall as appear to show that the left side of the room has descended. The dust shows the opposite. The table movement could be either - it could be pushed rightward up the floor by the out-of square wall at the left, or it could have slid rightward, downward.

However, the biggest problem I see with column 27 falling with no significant precursor on the roof is this:

If column 27 and those above it descended, we should be seeing the penthouse roof directly over it forming a V. That slab is the thinnest in the entire building.

The initial images indicate that the penthouse roof west of that column stack is 15 feet or so further down than the roof to the east, despite being supported by the exact same column.

While I agree that column 27 may be the main cause here, the differential collapse at the penthouse level needs additional explanation.

I’m thinking that what we’re seeing in the video is a cloud of dust, directly over the x11s, where the western end of the penthouse has collapsed prior to the main collapse - perhaps by only milliseconds, or possibly minutes, but earlier either way.

 

[waross]

Click on the Quote Icon.

Now you will see;

Start typing or pasting.
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Bill
--------------------
Ohm's law
Not just a good idea;
It's the LAW!

 

[jbourne8]

BennyTheBeaver, I think by the time the ring video starts, the tiktok user is already running away from the site.. they say in one interview that it collapsed as they were walking to their pool to take another video. The person who posted the ring video says it was recorded at exactly 1:22am. I thought they were recorded at the exact same time, but that doesn't look possible anymore. That north end of the building also stayed standing and seems to be pulled down by the south end, so they may not have really seen the leaning from there.

Js5180, The wall on the left doesn't seem to be at enough of a tilt to push the desk to the right. Also, the camera is pretty clearly not being pushed by how it starts to slide to the right and then slides to the back of the room (south). I've also had a hard time figuring out why that large box would flip to the right and stay there if the building is leaning to the left. It seems like the first noise is probably column 27 collapsing with how that box jolts and flips.

Part of the building's roof has certainly already collapsed in that surveillance photo before it starts, but I can't make much sense of that really. That's probably why we don't see that clear V you're expecting at the roof line though. You can see it on the mid-floors around those lights that are on once you add in some level parallel lines for reference.

This is the closest before shot I've seen to their surveillance video, and it makes it clear how that roof line should have looked from that angle when it started -

https://www.youtube.com/watch?v=8Pt7_ymjhpk

The difference between where those white lines that go up end (at the 8th floor near the x11 rooms, with the two room lights that are on in the surveillance photo around the 8th or 9th floor) and the roof is strange since so much of it seems to be missing. But it still seems possible that they just collapsed a bit early because of the stress the missing column in the garage was putting on them.. the 711 room seems to almost twist internally as it starts to lean to the right, and the penthouse had a lot less columns supporting it. When that video starts column 27 is probably already collapsed. The person who escaped 611 also said that large cracks were starting to form, and this seems to be around when the tiktok video was shot and before the ring video started.

The way that everyone describes the incident it's not really clear how much of the pool deck has collapsed when they look at it, or if that slab failure line in the pic was actually collapsed before the building fell. The force it would have taken to pull the slab cleanly from the fence seems to hint that it didn't detach from that spot until the building fell. Cassondra in 412 was right next to it and didn't think it looked urgent enough to evacuate right away. It's possible that the pool deck collapse was much smaller then. Even from the lobby they should have been able to see over towards the edge of the x11 rooms and the entire x12 stack.. and a missing planter was probably obvious from there. There's a good chance that 111 ran from the building because of the odd state it was in too, with popcorn ceiling raining down, rather than just how the pool deck looked alone. I swear her daughter mentioned the ceiling raining in one of their interviews. It's odd that if the initial cause was punching sheer failure, that this first column that collapsed entirely in the tiktok video wasn't puncture sheered. It seems like that might be more of a symptom that the weight the missing column put on the rest of the pool deck. Could explain too why there's no slab material stuck to the tops of the columns if those were puncture sheered with great force as the building collapsed too. It all just looks so strange it's hard to make sense of.

I think if Mike Bell's reenactment was correct too, we'd see that entire part of the building collapse at about the same rate. Instead just the portion under the failed column in the tiktok video dropping at a much quicker pace and the rest dropping slower. It also seems to be the simplest steps that could have caused this. And sure.. popcorn ceiling doesn't always fall straight down, but it would have to be at about that angle for the table and camera to slide to the right. If you tilt your head as you watch the ring video to keep the popcorn ceiling falling straight down, it all seems to line up. The video is pretty horrifying when you view it as being during the collapse.

 

[Js5180]

I don’t think the YouTube shows the “before” from the camera’s perspective. Here are some I pulled from a video taken from a walking tour. The red lines are mine, the yellow arrow points to the camera that caught the collapse. The step down in the roof, I think, is far more profound than people imagine:

 

[Murph 9000]

Part of the building's roof has certainly already collapsed in that surveillance photo before it starts, but I can't make much sense of that really. That's probably why we don't see that clear V you're expecting at the roof line though. You can see it on the mid-floors around those lights that are on once you add in some level parallel lines for reference.

I believe the CCTV footage starts after the facade has dropped approximately 1 floor. The video from inside 711 suggests to me that the M line of columns (right hand wall in the 711 video, right hand side of x11 balconies in CCTV from South) dropped maybe about quarter to half a floor ahead of the L line.

The KLM section for the x11 stack basically falls together, but M leads a little to give the slant in the 711 video. The stairwell resists at the north of M, N initially resists at the south before failing well behind the KLM collapse and leaving O–P as the sole bay to briefly survive at the south. The I columns in the x10 stack also possibly lagged by about quarter to half a floor.

Check out Building Integrity's analysis of the roof collapse theories and sequence. I find it quite convincing.

https://youtu.be/383SIaQDg0k

 

[Torai]

Agree with jbourne8 and BennyTheBeaver. I want to time tag the video, and make a time plot of (1) the angle that the popcorn falls showing the right end of the room dropping, and (2) and popcorn angle at the left and right of the image (how trapezoidal - as the room tilts back and camera points more up in the gravity field, streaks from falling popcorn will spread more at the bottom).

When the box moves (1st 3sec) the camera does not move at all relative to what its sitting on, there is a change in the scene, maybe a little more on the right. Also the wall between the door and fridge and the area above the door seems to distort between the pre-box-move and post-box-move frame.

I would agree that if I was shrunk down sitting where the camera is at I would feel as I was falling to the right and backward.

 

[SwinnyGG]

9 inch slump? Really? Unbelievable! Seems that the cement company had a hard time even making it. Actual was only 8,5". Ran out of water on batch 9/9?

9" is a relatively 'standard' slump value; 8.5" against a 9" spec is also completely normal. You can't efficiently pump low slump concrete.

Also, field measured slump values are never going to be exact; the specified target value is usually controlled in one of two ways; it's either a not-to-exceed limit, with lower slumps acceptable at the GC's discretion depending on how they plan to place the mix (ie pumped or not) OR it's a spec target with a tolerance (usually =/-1" IME, although ACI 117 allows +/- 1 1/2" tolerance for specified slump values above 4", because of the increased difficulty in accurately measuring higher slump values). If I reviewed a concrete spec from an engineer that called for 9" of slump, and when the mud showed up it tested at 8.5", neither scenario would be cause for a moment of second thought on my part. In fact, if 9" was a not-to-exceed limit in this case, I'd want concrete to show up between 8 and 8 1/2, so that I know I have a little buffer to the limit and I won't be worried about a load showing up that's over the line.

Posts above are inferring a great deal about the properties of the concrete without any hard data; looking at the slump value alone is meaningless unless we have access to the concrete spec and can determine what concrete strength, w/c ratio, plasticizer or other admixes, etc were specified, and we'd also have to be able to compare that to actual concrete tickets to determine what was delivered and placed.