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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[spinspecdrt]

Video of debris pile from July 12th from different angles. Video of debris pile 7-12-21

 

[nessman]

Some thoughts on the past 5 pages of this thread.

Security cameras - the outdoor surveillance video of the building collapsing - you can bet that camera / NVR / hard drive / SD card, etc... are all in a secure place for further analysis / evidence. There are a number of neighboring properties that may also have cameras recording and those too were all likely canvassed early on to preserve footage before it could be overwritten. Existence of these recordings, if any, aren't being made public.

The collapsed building security camera NVR/DVR system. If they have one - it's likely one of the first things they looked for to preserve it. If they found it, assuming it was still functional - they haven't said anything yet publicly (no reason to at this point). But it would likely be in a secure place for later analysis / evidence for now.

NVR/DVR systems are getting cheaper, with more storage space and higher resolution. No telling what type of system they had showing the initial collapse and really no reason to have motion activation on any type of system these days. At my home, the $300 system I bought on Amazon has 4 high-def cameras recording 24/7 and a 1 TB hard drive that holds a week of high-def 30 fps video. Cost shouldn't be a factor at this point. But like anything else these things need to be maintained too.

Some general thoughts about the possible causes. Most of you have some pretty good ideas about what likely happened and I'm not going to doubt those of you who are professional structural engineers for a living and know this stuff inside and out (not my wheelhouse). But until we know more from the people who actually have boots on the ground at the site - it's generally speculative at this point.

From what I can see from everything here, it took 10-15 minutes from the initiating event - whatever that may have been - to collapse. Something didn't snap and the place instantly tumbled down. This means the occupants had time to evacuate but there likely wasn't a plan or someone smart enough to realize something was very very wrong and sound the alarm / start pounding on doors, whatever it takes. A few people had the wherewithal to know something wasn't right and got the hell out of there just in time but most others in the affected portion of the building weren't as fortunate. The question I have was that security guard/front desk person asleep when it happened - or just unware/incompetent? No offense to anyone who works in security, but most are just warm bodies to satisfy insurance requirements and little more.

Unfortunately the condo association and residents found themselves in a very bad situation and it was too late to do anything about it (not that they didn't try as repairs were just starting to get underway). But egos, incompetence, pride, stubbornness, frugalness etc... all delayed needed repairs over the years and to get things moving fast after the 2018 report. Volunteer boards, as well meaning as they may be, are generally ineffective and unqualified in these areas - and serve little more as go-along to get-along governing bodies / social cliques (been there / done that).

Much will come out of this and like any disaster on this scale, many lessons will be learned and many changes will come to both existing and new construction of this type. Unfortunately it's disasters like this that spur changes (i.e., the Rochester Holiday Inn fire in 1978 and the MGM Grand Casino/Hotel fire in Las Vegas in 1981 were catalysts for hotel fire prevention / safety).

I wouldn't be surprised to see some buildings ultimately condemned and demolished because they are deemed too high of a risk for continued occupancy and too expensive to repair... and insurance costs for these types of buildings will go through the roof as a result.

 

[spsalso]

Let's not forget that a lot of people were asleep. You aren't leaving if you're asleep.

spsalso

 

[SFCharlie]

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...

SF Charlie
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[spinspecdrt]

Surfside recommends owners of older buildings hire geotechnical engineers to study ground below structure

"Surfside Mayor Charles Burkett and structural engineer Allyn Kilshimer, who the town hired to help with the investigation into why Champlain South collapsed, explained why they are urging the owners of older buildings to hire a geotechnical engineer.

“We don’t know why the building fell down and it is possible there were issues below the surface,” Burkett said."

Do you think the city is trying to cover their ass or have they found something pointing to geotechnical issues????

 

[davidbeach]

Arses, clearly.

I’ll see your silver lining and raise you two black clouds. - Protection Operations

 

[3DSoftwareDev]

Hi everyone,

New here, but have been following these threads since the beginning. Such a fascinating discussion, thanks for everything so far.

I wanted to go back to the Ring video from unit 711 because I think it's one of the most interesting pieces of evidence. Someone in a previous post noted that the direction of the falling debris changed over the course of the video, which may indicate the room is actually tilting. I hadn't considered that before, and wanted to investigate a bit further.

I've created a few GIFs of the Ring video which may be relevant to the discussion of whether the column in the parking garage is indeed missing.

First, I made a very short GIF combining the first frame (which I suspect was captured by the Ring cam before anything happened - nothing seems out of place) and the last frame only, to demonstrate how much of the room has changed over the 13 second duration.

It's obvious that the formerly rectilinear room has become quite deformed in the last frame. In particular, it looks like the entire floor is sliding to the left (or the ceiling sliding to the right), causing the wall on the left and the drywall column between the unit doors and kitchen to become noticeably angled. Also, the couch and the refrigerator (EDIT: not the stainless steel refrigerator, but whatever the black rectangular shape against the right wall is) on the right side seem to actually lift up. The refrigerator seems to move up quite a bit.

I suspect the movement of the black-refrigerator-looking object and couch on the right are due to the south side of the room falling, while the east-west column line, which runs right next to the black object, is not falling (or not as much), causing the black object and part of the couch to seem like they are lifting upwards.

Next, I took the Ring video and sped it up by about 8x, which exposes how the building is slowly, but actively, deforming under some sort of unsupported load condition:

Finally, circling back to the theory that the room is tilting during this time, I roughly rotated the view to match the direction of the falling material from above. One thing I'm not certain of, could this change in direction be simply due to a breeze in the room? I doubt the windows were open, but maybe they've broken by this time. If this is due to wind, then this theory falls apart, but if it's actually indicating the direction of gravity, then I think the room is tilting during the duration of the video. I had to reduce the framerate here to keep the file size down.

It seems like a pretty extreme angle of course, but what's interesting is the right wall here is exactly on the column line we've been scrutinizing in the Tik Tok video. Seems like structural changes along that line may be impacting this room (unit 711). Also, this would explain the strange snapping and movement of the TV box, and sort of rationalizes the strange lateral shifting of the floor and ceiling.

This video makes me think something has shifted so significantly in the building structure - several seconds before progressive collapse - that this room is both severely deformed and possibly tilted, and the collapse has already started, albeit very slowly. A missing column at the building line could cause this, but I know the column some think may be missing is actually only supporting the pool deck, one bay to the south. I don't think that column alone would cause the entire building envelope to sag, but maybe if it is missing, or if the pool deck collapse had also destroyed another column nearby, or some beam/connection at the building envelope and pool deck, it could be causing the entire facade of the x11 stack to start sagging? Perhaps there would be slow, visible movement of the facade in the exterior surveillance video, but it's too subtle to trigger recording until the moment the collapse picks up speed? This could also account for the alleged missing penthouse level in the video - maybe this facade has been slowly sagging for several seconds and descended many feet before the progressive collapse begins.

Probably a stretch, but I'd be curious to hear real engineers' thoughts on what's happening in this video. How is the structure twisting and deforming to cause what we see in the Ring video?

 

[nessman]

This probably isn't the place to get into the global warming climate change [sub]h[/sub][sup]o[/sup][sub]a[/sub][sup]x[/sup] debate. But... it's generally sage advice not to build/develop on the waterfront either. Sooner or later, mother nature will win - whether it be storms, erosion, flooding, rising sea levels, whatever the case may or may not be. Building on a sandy salt water beach is one sure way to give her a head start. Growing up on Long Island - this has been evidenced and documented many many times over the past 200 years via hurricanes and natural shoreline erosion - especially on the barrier beaches (i.e., Fire Island, etc...). Yet, people keep building / rebuilding knowing the risk. I mean who doesn't want a view of the ocean? Some places are best left to nature. There's plenty of places to build housing further inland.

 

[dold]

waross (Electrical)13 Jul 21 02:17
Good catch Nukeman948, thanks. Correction made.

Quote (nolascience):
Aren't those Electricals so cute with their talk of phases, breakers, and neutrals?

Back at you:
Aren't some of those those Structurals so cute with their mangled understanding of phases, breakers, and neutrals?

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

@NOLA
What is your angle? Ever since you've been active on this website, I suppose starting with the new orleans hardrock hotel collapse..., your posts have always had this sort of accusatory flavor - always looking to blame SOMEONE right away... I think I can speak for many here by saying that a lot of your input is not very constructive, and some of your posts simply do not belong on this forum. It is unfortunate that we're devolving back to pissing match type posts as seen in the warrenslo era (my post here not excluded...).

I'm also curious about Demented's question earlier:
Quote (Demented)
Does anyone by chance know what the theoretical compressive strength of column M11.1 should have been in an ideal environment?

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

Keith_1 (Structural)12 Jul 21 12:40
Even IFF a car took out a column, there is so much redundancy built into a structure that it is a non-event. This structure has has been subjected to multiple instances of high asymmetric pressure loads (hurricanes), and those pressure are way greater than loading a roof with a few tons to support a swing stage, or taking out a single column. I will state with 100% certainty that a single column, beam or any other discreet element will not cause a catastrophic failure like this, in a structure that has been loaded in the manner that this building has.

I will have to 100% disagree with you. The complete loss of a column in this building can, and likely did cause a catastrophic collapse like this. Lateral loads can indeed effect vertical forces on non-LFRS members, but to say a hurricane will impart more severe loads on a gravity member than a total loss of a column is simply not true. If you disagree, please discuss. The only possible way I could see this being the case is if you consider the absolute lack of shearwall in the E/W direction causing story drift that imparts significant moment into the columns, and this would be more apparent in higher stories, not at the base. Even then, it is likely that unbalanced moments at column/slab joints would initiate a punching shear failure before a failure of the column itself. Who knows, but the building certainly collapsed.

Awestruc (Structural)11 Jul 21 04:35
I don’t see how unbonded PT tendons that are stretched to 70%-80% of their ultimate tensile strength can offer any shear strength. They would be under extreme tension + shear = pop.

Modern connections are more robust due to the use of stirrups or stud rails or puddling of high strength concrete atop columns (questionable).

The pool deck design had no real shear reinforcement. The design concept was
To design the concrete thickness to handle the shear. Then to design the horizontal top bar for flexural tension, and then place a certain amount of horizontal rebar directly over the column for good measure. This is the same philosophy with modern PT.

Integrity tendons support the failed slab via catenary action. All prestress in the slab and tendons goes to zero as soon as the slab fails. They offer effectively no shear strength. And yes, two way mild reinforced slab design and modern PT design share many similarities. One critical difference is that there are no splices in PT tendons. I would wager a lot of money that not a single one of the top bars (or any bar in this building) failed in tension. All discontinuities are at lap splices. Hence the importance and effectiveness of integrity tendons.

 

[SFCharlie]

how much of the room has changed

I'm stunned by how far out of perpendicular the (post? wall?) between the door and the counter moves!

SF Charlie
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[Keith_1]

DOLD

Let me guess if a PT tendon fails, the building is going to fall down. In reality, you abandoned it.

 

[dold]

Let me guess if a PT tendon fails, the building is going to fall down. In reality, you abandoned it.

What are you talking about? Losing a PT tendon isn't quite the same as losing a column..? As I described in a previous post, integrity tendons would not necessarily prevent a collapse in the case of a column failure, but the intent is to prevent a pancake type collapse in any event.

 

[SFCharlie]

Can someone tell me this is not what it looks like.

What does it look like to you???

A Cat-Racoon Hybrid?

I still thick I see a Giant Yellow Jacket

SF Charlie
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[Keith_1]

Dold

Seriously, do you truly believe that a single column is under that much compression, that its failure would result in a 12 story building failing?

 

[warrenslo]

I'm still lurking but nobody has changed my mind. The roof anchor work caused the penthouse roof to collapse onto the pool deck.

1) The green bag in the tick-tock is a roofing material bag (similar to that left behind on the existing building. There's no way it's a plant, haven't any of you seen a plant upside down, it's brown dirt. Photo of left over bag:

2) The penthouse collapsed first, no matter how you look at the pool video (which was activated by movement or has earlier shots not shared with the public) those floors are missing, get that through your head!

3) I requested the recent inspection records and the city replied we posted them not realizing they only posted to 2019 (at that point.) They replied days later after they posted the info from 2019-2021. Literally, the only work on the building is to the roof in the last weeks. Buildings don't just collapse unless provoked. The demo experts (CDI) said the rebar they dealt with was different but not rusted, damaged, etc. If the rebar was wrong this building would have fallen during construction or shortly thereafter. If the rebar is wrong, in a 40-year old building, the first thing you check before roof work is to make sure the roof work can be withstood. The structural engineer clearly had an agreement with the roof anchor guy, I'm not sure all of you understand how these rackets work. Most roof anchor companies use their own structurals and because of OSHA rules get a yearly maintenance fee for the life of the anchors they install. It's government at its finest. And, it's not in the IBC.

3A) IN a recent debris pile photo - I can't find it again - they have placed a green bag (same color as roofing) next to the column which was damaged by the pool deck cars. Plastic doesn't get damaged too much by concrete, I'm curious about this. Can anyone find this photo - it's recent?

This entire discussion has digressed into complete BS from some members, if you can prove MY theory wrong, please do it with evidence. Nobody has thus far, even the guy claiming the "C" on the gate was not an AC unit was ignorant to the fact the C was right above where he claimed the "C" to be.
CHANGE MY MIND!

-W

 

[warrenslo]

Well lookie here, KCE is drilling to the ... Penthouse... boom...

Link

 

[BKNJ]

One thing I would like to point out with the 711 video... a lot of the room appears to move to the left, but I think in reality, the extreme tilt of the room is actually causing the table the ring camera is on to slowly slide down to the right.

I've also noticed a lot of people claim the falling debris to be from the popcorn ceiling... and I think it's too fine to be popcorn. It looks like powdered concrete to me. I thought if the camera is backed up to the concrete block wall, that it might be coming from cracks grinding across each other in the concrete block wall. Is if possible the slab has cracked above the camera and this is concrete dust from cracks in the slab moving?

BKNJ

 

[Auri]

WOW, you have the exact same idea I had! Last night I made a GIF alternating between 1st and last frames, and a 50fps version of the active video frames to show there was slow but eerie movement.

I believe I can disprove the gravity shift idea, though, and attribute all the skewed movement to wind. The parabolic bounce of the particles near the "desk" the cam is sitting on is still symmetrical across the top-down axis of the camera viewpoint, all the way till the last particle bounce near end of video. The "desk" is however lifted slightly from the left at the end, which I attributed to the floor warping upward toward the wall at the southwest and northeast corners, at minimum.

 

[rodface]

I finally created an account to thank you for the GIFs and analysis you’ve contributed. I too have been following this discussion closely and believed that the Ring video contained valuable clues to the movements of the building in those final seconds. I lacked the time and ability to illustrate it and you have exceeded what I could have hoped to present. Some observations:

•Can we pinpoint the precise location and direction of this view, on a floorplan? This will help make sense of the perceived distortions
•I don’t think air movement is a large factor in dust trajectory but it should not be ruled out, A/C registers puffing due to being crushed/pulled, large objects falling outside camera view, broken window as suggested, etc. I am intrigued by the displacement of the dust vs the frame of reference, are we seeing the room shift as the dust continues falling, some combination?
•In the last GIF on the upper left there is something interesting happening, a crack forming or the wall has changed shape perhaps
•Can anyone identify the precise device that recorded this? It appears to slide across the surface it is resting on, what size of deflection/force could be expected to cause that?
•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? Knowledge of the device can inform this.
•Timing of video end coincides with loss of power but there are delays due to latency in wifi connection, server-side activity. Just some disorganized thoughts on the element of time with regards to the footage.

Finally I’ll just say that the visual of the upper floors perhaps failing first due weaknesses/flaws, and slowly sagging down, hanging on by threads of rebar is... chilling.

Oh and about the “green plastic”... I guess not too many people have done any major home remodeling and filled up a $25 Bagster... at least that’s what that shade of green and those yellow lifting straps looks like to me!