Miami Beach, Champlain Towers South apartment building collapse, Part 06 131

[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

SF Charlie
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[rodface]

I think the rotating clip was made to illustrate the scenario where "the dust always falls straight down" but of course does not hold 100% against other clues, such as those you have pointed out. It is likely that the dust is being affected by other forces. I like the idea that someone higher up mentioned, that the room's shifting out of square is pushing air around inside the space.

 

[CE3527]

Spalso - or is that box empty (and the actual TV is to the left), so the empty box moves very easily?

As for the bar chairs, if the settlement is happening diagonally across the room from the right and to the front (towards columns M-9.1), then objects in the rear are less susceptible to movement. One possible explanation anyways.

 

[waross]

I have no idea of the origin of your user name, NOLAscience, but it rings a chord with sparkies.
Nola Technology, Nola Devices, Nola Science; Nola Devices are marketed as a cost and energy saving device. While there are some very few niches that will benefit from a Nola Device, the great majority of the marketing is misleading and at times an outright scam.
To a sparky, Nola Science has no credibility.
Your user name is blowing a pretty loud dog whistle to the sparkies.

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

 

[spsalso]

CE3527-

Then the foreground would twist visually, compared to the background. The whole scene just twists evenly.

It's true the newly tilted box could be empty, and the stacked boxes full. Still seems like they would slide, though.


But, as rodface points out, it could just be an exercise in demonstrating the assumption of "vertical fall" for the "stuff". And that it didn't happen. Vertically.


spsalso

 

[Murph 9000]

...but they can drop another building down on top; are they concerned about damaging a crime scene? Go figgure...

It would have been better for the investigation if they didn't have to do that, but we know that the lower 5 or 6 surviving slabs had partially or fully detached from E2 and E4, based on the way they were sagging. The lobby level slab had fully dropped away from those columns, based on the early video of firefighters in the basement. At the south end, 3 significant columns were both damaged and had lost bracing due to the surface parking deck dropping. The surviving section of tower was clearly badly compromised and at high risk of collapse.

Mark Loizeaux did a truly remarkable job bringing it down, specifically avoiding bringing it down "on top" of the collapse. With only a couple of days planning, he moved it SW as it dropped and still kept it within the site boundary and its own footprint. Yes, some evidence was lost, but not really in the original collapse area. They reported only dust fell on the geotextile covering the original pile.

It was a judgement call to bring it down, but it made a lot of sense to do it. Note also how the recovery process was able to move much quicker without the unstable remaining structure looming over them.

 

[tmwaits1]

this is the detail in the Morabito rehab plans that shows strengthening of the slab to resist punching shear. These are preliminary plans so they don't say where they intended to use this but it looks like they didn't think some of the 9-1/2" slabs were adequate to resist the design loads for this failure mode.

 

[MechinNC]

Yep, if the deck and the stools are rotating and accelerating together, there is little reason for them to tip. We don't know really what motions were occurring.

 

[Teguci]

Regarding the webcam video - some questions:
1. If the camera is accelerating down with gravity, how fast will other particles fall in comparison?
2. What is that powder and why is it detaching from it's substrate?
3. The upper floor is shearing to the right and the lower floor is shearing to the left (you can see this deformation has already happened at the entrance frame in the first second of the 11 second video).

a. What do you think the rebar in the upper slab is doing considering the rebar failures we saw at other locations?​

b. Given the orientation of the parallelogram, and assuming the columns are staying vertical, which way are the floors sloping during the fall?​

4. Wasn't the elevator stair wall on grid M a clear dividing line between progressive collapses as seen in the exterior camera?

My thoughts - The white powder is being forcefully ejected due to structural deformations under considerable stress. Their direction and speed is not simply from gravity. The powder might be caused from the rebar in the slab above stretching (bottom slab in tension at upper left column to slab connection) and turning adjacent concrete into powder. You can kind of imagine the source of the powder is traveling to the right as the video progresses. As seen from the exterior camera, the floors are failing towards the column at K or L.

Further questions - do any of the particles arc up? Are particles traveling in different directions? Under gravity, 6th floor had a little more than 1 second in freefall. At what point do you think the building let loose in the video?

 

[3DSoftwareDev]

It's true the newly tilted box could be empty, and the stacked boxes full. Still seems like they would slide, though.

I read somewhere that Rosie, the owner of Unit 711 and the Ring camera, confirmed that the TV box that snaps/shifts midway through the video is indeed empty. I'm struggling to find it though. Will update this when I do.

I also find it odd that more objects are not sliding around during this time, other than the TV box moving. But perhaps the angle isn't quite extreme enough to overcome whatever friction the objects have with the floor, until the very end, when you can see surface the camera sits on moving to the right relative to the floor, which I assume is it sliding across the floor. I cannot tell what the camera is sitting on, if it's a piece of standalone furniture or some built-in casework. I'm assuming the former currently, but I don't know what the "column" in the very far left of the frame is, which seems to be attached to the surface below the camera. If it's a piece of furniture, it could be a credenza with a wood column supporting something above it.

 

[3DSoftwareDev]

2. What is that powder and why is it detaching from it's substrate?

I haven't seen a section through a typical unit, but I assumed these units were finished with a sheet of painted drywall at the ceiling, perhaps dropped down from the slab to hide plumbing and HVAC. But if it's actually the painted bottom of an exposed slab, then I'm wrong, and the powder would be from a cracking concrete slab above, which was suggested also. The particles seem lightweight and fine to me, suggesting drywall, but I'm not 100% sure.

I also think the camera is near the unit's balcony doors/windows, so there's not much behind the camera other than a thin section of slab, or the balcony above and behind. Perhaps the debris is caused by cracking of the slab or drywall near where the balcony connects to the rest of the slab. But it's unclear where exactly this debris is coming from, or how close to the slab edge it really is. The camera and whatever it's sitting on could be closer to the middle of the room, for all I know, hard to say for sure.

 

[jbourne8]

Sym P. le, NP. I attached the video from the USA today site to this post. It hasn't been edited at all from their version and it's just the raw video they had. It's 17M so it's quite a bit larger than the tiktok one was (1.59M).

Someone on youtube suggested this was a better video than the USA today copy, but it seems condensed to me and not as clear -

https://www.youtube.com/watch?v=0g1sNRSOz44

You can also just download these directly from youtube btw.. but you'll have to google that one.

Also, people on youtube are also asking that we stop placing blame or investigating the victims. Lots of people are reading this, including friends and family members of the deceased. Try to keep that in mind, NOLAscience.

Teguci, I posted that ring video tilt in part 4 with the timestamp "9 Jul 21 08:33", but in that post I also added a bunch of parallel lines to the surveillance photo that show that the M column seems to be descending faster than the rest of the building. It is a hard angle to understand without drawing in what level should be though.

Lots of cameras and tables don't have as much grip as chairs do too btw, since they aren't really meant to shift around.. I don't think it's that odd that the chairs never move. And even an empty box would need a good deal of force from the building to shift like that on it's own.

 

[3DSoftwareDev]

At what point do you think the building let loose in the video?

I'm under the impression that the building starts progressive collapse in the final 1-2 seconds of the video.

In the original footage, with audio, you can hear a terrifying rumbling begin right at the end before the power cuts out. It's also around this time that the floor and ceiling are doing a crazy dance and the whole room looks like it's deforming much more quickly.

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

I always assumed this sound was the 5 floors above pancaking, but it could be the entire structure this side of the corridor sliding downward as part of the progressive collapse, as you seem to allude to.

 

[Penagwin]

Those chips/dust in that ring video seems to me to be way more then just some type of dust falling - something was either ripping/tearing, or being compressed so much that chips were being ejected (I lean towards this one).

Either way, it seems likely the chips are being ejected from their location? If that's the case, then it certainly seems possible that their ejected direction is shifting along with the wall. I think we can safely say the point of origin from the dust/chips is moving across the room (at roughly a foot a secondish?).

I think the left part of the floor is being separated from the ceiling (whether the floor is falling or the ceiling is raising I don't know), there's a crack propagating in the ceiling/against the wall behind the camera, and it's propagating like a zipper across the wall.


Can somebody confirm for me that the camera is roughly near the balcony looking in towards the kitchen? And somebody that's smarter then me confirm that if it was horizontal shearing we wouldn't have seen the crack propagate horizontally like we see in the video?

EDIT: Actually I think compression would be more likely to eject chips like this, can a civil/structure confirm this to?

 

[RickyTickyTavi]

I think its hard to equate relative movement on the particles once the building starts to move. Is the camera anchored to something and also moving? The vectors the dust takes will have gravity affecting it and whatever force knocked it loose initially. Whether those were localized shear, buckling or flexural failures, i could imagine dust being on a path not quite normal to gravity. The Gif maintaining verticality on the dust in my opinion isnt quite reality in terms of where the floor actually is relative to the horizontal plain. The first two gifs are great though. That 13 second frame change is really fascinating.

 

[Penagwin]

I've been looking at the video more.

I'm fairly confident the floor is higher on the left side then the right at the end of the video, I think by roughly 10deg as this is both the angle of the wall next to the refrigerator and the angle of the dust.


This is confusing to me though because if that's the case I would expect the dust to have gone from the right side to the left instead?

 

[Teguci]

To those who have lost love ones and somehow find your way here -
May the Lord bless you and keep you
May the Lord make His face shine upon you and be gracious
May the Lord lift up His countenance upon you and give you Peace.

 

[rodface]

@Penagwin you are correct, there is a post higher up that marks it out, but yes near balcony, facing towards kitchen/front door/building hallway

@3DSoftwareDev are you able to create another GIF where you show the sped-up movement, but instead of looping the video, you play it forward, and then play it back? Imagine a simulation of a beam under load where the goal is to show it wiggling back and forth as it loads and unloads. Perhaps this allows us to better view the displacement without the jolt of it resetting to the 0 mark.

An observation after replaying the video with sound. At the beginning there is definite crashing and some groaning/rumbling. The groaning is similar to what is heard at the end, without the... for lack of a better term... galloping hooves sounds.

The most interesting thing to me is the empty TV box: at 0:10 there is a sudden snap/bang, and it shifts position.

Last night my wife's friend told her that their 1 year old had knocked over a floor length mirror that was leaning up against the wall. Just now I had the same thought about that TV box: What if there was a mirror, or a picture frame, that had been leaned against the wall, and then the TV box was placed in front of it. That sharp change in position marks the point where that leaned object became vertical, and then fell forward, against the TV box. What does this tell us about how this scene is angled?

 

[RickyTickyTavi]

EDIT: Actually I think compression would be more likely to eject chips like this, can a civil/structure confirm this to?

Compression failure of concrete is typically "explosive". Not like fireball, but the dispersion of energy will send dust and concrete projectiles in all sorts of directions.

 

[RickyTickyTavi]

this is the detail in the Morabito rehab plans that shows strengthening of the slab to resist punching shear. These are preliminary plans so they don't say where they intended to use this but it looks like they didn't think some of the 9-1/2" slabs were adequate to resist the design loads for this failure mode.

I think you bring up a good point here. There's not really a code rationale for a structural engineer to 'strengthen' the shear capacity of an existing slab/column interface unless the design loads were being changed or the existing capacity was insufficient for the applied loads. Based on the core samples taken it appears as though the deck was a good bit thicker than predicted. I'd imagine their engineer elected to add in drop down panels to accommodate the existing loads.

Another thing that I'm a bit skeptical of are the planters. I might be missing it, but on my drawings I traditionally call out planters and their estimated weight of soil, etc. For really large planters on buildings, Ive put a line in there limiting the kind of plants they put in the planters. I dont really see that on the original plans.

 

[dauwerda]

Here is a video showing the "explosive" compressive failure of a concrete test cylinder:

https://youtu.be/iev2UNX16QA?t=62