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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[Auri]

Oh, that's not the phone camera, it's sodium lighting. Green turns black and white becomes pale orange.

 

[zebraso]

Oh, that's not the phone camera, it's sodium lighting.

You can probably get the white balance of the video camera off the white columns. If any assumption or guesstimate can be made about the paint hue you can gauge the blue shift and correct it if it is way off. I think. Maybe. For the sake of argument. That's assuming the same type of lighting is used throughout.
And then incidentally you would want to correct it to the daylight color temperature to compare it to the roof top photo. Most likely the video camera is set to fluorescent and the outdoor camera daylight. I'm a little hazy on color calibration right now. Every time I think I understand it I get corrected. photopic incandescent used to be 2856 kelvins. But the trend in imagery has been to make everything bluer than it really is. So I don't really know how to do it if it is even possible. Probably not.

 

[Demented]

July 12th at 2pm - Seeing widespread reports of street-flooding on social media all across Miami Beach and points northwards
Nop, no evidence of changing climate here...

Nope, no evidendce...
Two abandoned single story buildings in the industrial complex at my work had caved in some time over the weekend, likely from all the rain.


The geotechnical research into the foundation is needed. That land has gone from tidal pool to ocean/intercoastal crossing to filled in and building built. In newer ocean front construction, on the E and W of the property typically, steel cribbing sometimes gets driven down to form a wall to prevent waterflow from tides attempting to flow underground from the ocean to the intercoastal. Not common, but people are determined for their beachfront property. 2003 was the first time I saw that at a building located on the E side of the island.

We really like to move lakes/water ways, fill, and build on top down here, in under a month. Gotta get that ground filled in because the concrete trucks have been waiting since a month before the drawings were finalized.

6,000psi spec'd. Look at the left side of the column schedule on the original struct drawings.

Thank you.

Turn on captioning and go to Settings (gear icon) to select English translation. At about 8:50, he says that one column of the type that we are interested in would have
a capacity of 320 TONS. Impressive.

https://youtu.be/c-1wwF_STiY

EDIT TO ADD: This is a FANTASTIC video, and well worth the 30 minutes. It is so fast-paced; after the intro, the video is packed with information with technical ideas presented in a way that almost anyone can understand. He uses a very nice 3D model and even some cardboard mock-ups of different structural systems.

I think he has an error in his calculation of live load, which he calls "overload". 40 psf is 200 kilos/sq meter and he says (or the translation says) 300 ksm. Also, I don't see that he used any live load reduction, discussed on Thread 1 or Thread 2 of this forum discussion.

So 12x16=192
6000+28000=34000 (Yield point psi of carbon steel)
34000x192=6528000lbs (326.4tons)

Something aint right.

Precision guess work based on information provided by those of questionable knowledge

 

[Seppe]

A building with no apparent preventative, successfully-deployed maintenance. Cosmetic attempts at best.

A poorly-drained plaza deck subjected to what over time was unmitigated water and chloride intrusion.

A two-way flat slab system inherently sensitive to direct punching, with tricky transfer of slab-column joint flexure that magnifies the punching effect... all occurring in what appear to be regions of much lighter-than-normal top reinforcement ratios. 

A very thin concrete slab (by today's prescriptive standards) susceptible to long-term creep effects made worse by a heavy paver and saturated planter system that is a very real permanent load.

If we were to design and construct a building with the above attributes today, how long do we give it before the confluence of systemic issues rear their ugly heads in the form of failure/collapse?  20 years?  30 years?  40 years?  And do we even need an acute, oddball event like faulty roof anchors or vehicular impact to set such a catastrophe in motion?

Some of the people who are married to the roof anchor theory don't seem to want to believe that the devastation absolutely could have been the result of a combination of unspectacular things at the pool deck level that got significantly worse over time. Ironically enough, it's that same thinking that allowed the building's condition to devolve the way it did.

 

[jbourne8]

I took that USA today video and stabilized it and cropped it down too.. and tossed the tiktok video onto the end of it so they're all in one clip. I also removed the bits where she scans around and it's too blurry to see into the garage, so just the good bits are left:

https://youtu.be/LoNy55PaHlc

Someone in here earlier asked why I thought you could see sky when looking into the garage, and I think that USA today video has been overlooked a bit. You'll want to watch the video to get the full context and see how the shadows change, but in the first few seconds you can see this frame:

I actually didn't notice what was going on here entirely until I was fixing the video.. it's a very time consuming process and I end up looking at the video a lot during it. Anyways.. it seems like the pool deck slab is actually resting on a car parked in 39, and it's clear that you can see the column between 39 and 40 (not sure what the letter is, but it's between L and M and is 13.1).

I'm sorry to say it, but I'm pretty sure you guys have spent two days studying the greenish tint of the back wall of a garage.. it's clearly behind the car and in the very back. This roof theory really has no merit.

 

[LittleInch]

Seppe - I don't know enough about the structural stuff, but that looks good to me also. Will be interesting to see how many other buildings are like this in Miami and elsewhere.

As I said in an earlier post, I can see how it's difficult for anyone to say something is structurally unsound when it's still sitting there and has been for nearly 40 years. It probably takes something like this to focus the mind.

Everyone is so sure that the building didn't fall down for no reason or initiating event but so far nothing is standing out and maybe that's what happened - it just fell down, piece by piece which then accelerated. Just because it was built in the USA doesn't mean it can't just fall down if you don't maintain it.

If you had 8 re bars in a beam and you gradually cut then one by one, the beam would fail before you cut them all. Why does this not apply if they slowly corrode over time. At some point the FoS goes from 1.001 to 0.999 and that's the end of the beam / column / slab.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[Keith_1]

The hardest question is how do you monitor a membrane that you cam not observe? Specifically, how do you actually protect the building envelope, when it is covered with pavers, asphalt and planters. I plead total ignorance to this issue, I really can't formulate a "best principle" for this problem.

 

[Teguci]

The hardest question is how do you monitor a membrane that you cam not observe? Specifically, how do you actually protect the building envelope, when it is covered with pavers, asphalt and planters. I plead total ignorance to this issue, I really can't formulate a "best principle" for this problem.

Good question - For starters, any detected leaking through a plaza system should raise a maintenance flag (the water has to go somewhere so a leak should be able to be detected and tenants are usually happy to complain about it).

The plazas I've detailed were effectively sloped roof membranes (hot applied asphalt is preferred) overlaid with a drainage board, then a slip sheet (to break the VQ/I shear interaction), and then a wearing surface (concrete for me or concrete with pavers). I could imagine some long term failures near the plaza drains, but otherwise think the system is fairly hardy. Repairing them is extremely expensive (requires concrete erasers) and locating the membrane leak will be frustrating. If the client doesn't want to invest in a 50 year life span system then they probably shouldn't be installing one.

 

[1503-44]

If we can monitor the underside of 150,000bbl oil tanks for leaks, a pool and jacuzzi should be manageable. But someone will still need to make repairs once in awhile. That seems to be the real problem. That corrosion and permeability deterioration was observed, but apparently no action was taken.

Let's try not to tarnish the security guard here. We can't really be expecting to evacuate buildings every time we hear a thunderstorm like noise at 1:00am. And who would expect the building to come crashing down 5 or 10m later. There were probably too many people asking her what happened for her to leave her post and actually investigate. There also seem to be a lot of engineers here that wouldn't believe the building would actually collapse even if they themselves saw just one broken column anyway.

 

[CE3527]

Really great work by 3DSoftwareDev and the analysis of the Ring video. It got me rethinking the initial collapse. I had always assumed the columns along link K and L collapsed first because that is what I saw on the CCTV collapse video. But I don't see how items can be falling to the right in the Ring video unless it's columns along line M that are failing first. I also assumed that M held firmly because column M-9.1 can still be seen in the Tik Tok video. But what if it's column M-9.1 between the 1st and 2nd floor that has failed? To go along with what 3DSoftwareDev mentioned, here's an elevation view of that scenario using the building elevations.

 

[SFCharlie]

PLEASE STOP POSTING IN PART 5 PLEASE

SF Charlie
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[SFCharlie]

Watch Live: Champlain Towers South Recovery - July 12
Right Now, and since at least 6:40 PDT (9:40 EST) the search team has been ripping up the pavers midway between the pool and guest parking. They are sawing holes in the pool deck and removing the slab with an excavator.

SF Charlie
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[rodface]

Thought I would put a frame from the TikTok video next to the USA Today video, both from Jbourne8's mashup. I thought they were the same file but they are clearly two different clips taken from two slightly different locations. Look at the #27 on the column and how the gate bars obscure it. Interesting how the object that resembles an AC compressor or patio table in the TT clip cannot be resolved in the UT clip. Of course this could be due to the greater compression in the latter. If there were 2 clips, I wonder: did she record more clips? Were the original files retained on her phone (likely will be higher quality and have less artifacts).

The same issue of compression/reproduction affects the other "primary" source of video evidence, the security camera from the property to the south. EVERYONE is working from a video recording of a screen that is playing back the video. I hope that the original video file is preserved (and that it becomes publicly available at some point), it is entirely possible that it contains sufficient detail to answer many questions, detail that was turned into blurry mush by the "re-recording". The strange "ghosting" of the highlights that can be seen on the white screen at the start, perhaps an artifact of the playback software, the screen, or of the camera performing the secondary recording, makes me think that much more detail is available than we are able to make out from the version we have access to.

 

[NOLAscience]

So 12x16=192
6000+28000=34000 (Yield point psi of carbon steel)
34000x192=6528000lbs (326.4tons)

Something aint right.

Did you watch the video? I didn't pay close attention to his calculations -- it was late when I watched and I may go back and watch again tonight -- but I thought he was using the design values for his calculations. He may have been comparing what the column was designed for to the load on it.

@waross,
I wouldnt go so far as to call our friend NOLAscience a "structural"...

Am I going to have to pull out those finite element matrix multiplications that I did BY HAND in graduate school to prove that I have structural analysis knowledge? Am I going to have to show you the shear flow calculations that I did yesterday for a job? No, I don't owe you such evidence.

I am just VERY suspicious of the stories people tell. I've seen too many 'neat stories' -- all tied up with a bow -- that later turn out to have had some crucial detail left out. I am not trying to blame any one person -- the failure was likely due to a combination of factors (see below) -- I am just trying to encourage us to look more closely at this man's statements and see if they ring true to you.

Ever since you've been active on this website, I suppose starting with the new orleans hardrock hotel collapse

I was active on this site BEFORE the Hard Rock Hotel collapse, see

https://www.eng-tips.com/viewthread.cfm?qid=457407

. And, my account data displays, "After joining Eng-Tips Forums on November 20, 2017,..." In addition, I think I had an account before that but perhaps lost the login, so I may have created a new account in 2017. I've certainly been reading posts here for a very long time.

 

[SFCharlie]

Quote (rodface)
The “old” initial frame is a bug that turns out to be a great feature here. Question is, how old is it? Could it be from the last activation (minutes ago, hours ago, why did it activate, loud noises perhaps?), or is it from a few seconds prior?

Great feature/bug indeed. I was very thankful for that first frame - an incredible reference opportunity. I assumed it was from just prior to the first frame, but you're right, that's not proven.

I have a ring camera, and it creates a unique video for each event

SF Charlie
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[NOLAscience]

Why isn't there more discussion teguci's sketches and notes? I find them quite convincing, especially (1) the planter hiding possible cracks in the slab step-up, (2) corrosion of #3 stirrups in this 'beam', (3) lack of development of rebar into 'beam' (no hooks, either), and (4) Champlain Towers NORTH (uncollapsed) has a different detail at this location (design flaw noticed and corrected?). My guess is that others find his theory convincing and have left the discussion. I wish I had had the patience to scroll through the design drawings to study the details.

So I've fleshed out my completely speculative deterioration hypothesis. In short, the drop beam at the planters is not detailed to transfer positive moment across the beam even though the reinforcement suggests that it was designed as a 2-way slab (top bars match adjacent slabs top bars). It took 40 years because the #3 stirrups needed to deteriorate before failure started.

Questions that would serve to illuminate:
- Is there any rusting of the #3 bars at the slab drop beam?
- How far are the #5 hooked bars developed in the slabs at the transitions?
- Did they hook the "Beam A" bars into the columns?

https://files.engineering.com/getfile.aspx?folder=325ca65d-6749-4a61-ba79-6

Does anyone have the plaza slab design details for Champlain Towers NORTH?

I wonder if water was pouring into the parking garage that night from the possible crack and/or failing slab at 11.1 below the planter? Has not been mentioned by garage witnesses, though.

Add this to the comments about the general lack of redundancy (due to lack of beams in this building, for the most part) by the architect at

https://youtu.be/c-1wwF_STiY

, and I think you have a cohesive theory of the collapse.

 

[SFCharlie]

I don't want to joke about it either

I apologize.
(I guess I'm just trying to cope with my horror. Watching the videos on YouTube, sometimes I just burst into tears...)
Laughing is the way humans deal with pain.. (paraphrasing "Stranger in a strange land")


SF Charlie
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[SFCharlie]

There could be a car under the debris right?

Watch: Yes, several, they have been being craned away.

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[rodface]

Livestream is a great find @SFCharlie. Unfortunately the ramp area of primary interest is just obscured from view by the adjacent building!

They have cut a nice clean rectangle out of the pool slab by the column marked 39 (EDIT 38?), slab layers are visible, it's definitely resting on crushed cars at some height and there is a good amount of water down there.

 

[NOLAscience]

Let's try not to tarnish the security guard here. We can't really be expecting to evacuate buildings every time we hear a thunderstorm like noise at 1:00am.

No one is "tarnish[ing] the security guard". This isn't "thunderstorm like noise"; the guard told Mrs Nir that there is "an earthquake". The guard COULD be trained to pull a fire alarm if there is an earthquake, especially at night, but this is "tarnishing" the security company that trained the guards, not the guard herself. Of course, earthquakes are not considered a risk in the Miami area. <<"We are not on a fault zone," said Dr. Warburton. "In fact, South Florida is what they call a-seismic, without earthquakes. It's one of the most earthquake free zones in the world. We are very unlikely in South Florida to suffer damage to an earthquake.">>

Some of the posters here are prone to exaggerating the comments they are responding to. Geez...