Miami Beach, Champlain Towers South apartment building collapse, Part 09 139

[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
Miami Beach, Champlain Towers South apartment building collapse, Part 06
Miami Beach, Champlain Towers South apartment building collapse, Part 07
Miami Beach, Champlain Towers South apartment building collapse, Part 08

SF Charlie
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[Ingenuity]

This looks to be the most successful thread on this site, and it will probably continue to be until we get real answers and closure to this shocking event.

How you measure successful threads is not by the quantity of replies, but by reply quality.

In the 20+ years I have been an active member on Eng-Tips, the majority of this thread (and its recent related parts) does not qualify as quality, and in my opinion, takes this forum site to the dark side of conspiracy-theory trash.

 

[Demented]

Seems there's very two distinct groups here. Those who believe the collapse happened over a day or so, and those who believe it happened instantly with no other outside factors possible.

@Seppe
There seems to be multiple roof first theories. Some of which I don't agree with as things like A/C units falling off the roof, punching into the pool deck, and still being recognizable.


I've been doing my best to try and find any and all modifications to this building, and map them out on which columns, slabs, and beams have been worked throughout the start of the building's history. It all centers around a certain arrangement of columns, E-K2(or 2.1 depending on which version you look at) and E-K4, and then a lot of work on the slabs between the H to L column lines south of row 9, as full depth repairs to balcony slabs did extend into interiors of units. A large portion of this work was done by the same engineering firm and same contractor, that seems as though they were using outsourced staffing firm day laborers to keep costs down as much as possible, and even in the words of the field inspector/supervisor, passed incorrect repairs anyway.
Anyone that's been into enough homes/units and demoed them knows very well what a cracked slab looks like when you view it from the top, without ever needing to see the slab. Tiles don't just magically crack in the same row for no reason. This, along with slanted door openings along slab supported by columns I8-L8, with signs just starting to show near M8. M8 being the very suspect place over a "how in the fuck did this get built?" design error if I am not mistaken. Seriously, I'm still scratching my head because the 1-17-80 change of column type revisions include that elevation change that I don't see mentioned anywhere in the construction or revision notes. These plans should have been reviewed and kicked back with a lot of angry red pen scribbles. It doesn't take a rocket surgeon to realize there wasn't much supporting the generator room; hell, even Morabito knew that which is why they were going to put a larger steel support beam in there to redistribute the load a bit better. This work being done already or not is still questionable. I haven't seen permits showing it, but at this point permits don't seem to matter for anything other than proving poor engineering, planning, and construction.

TL;DR, I'm concerned with work over the poor roof structure as well as additional weight having lead to an upper slab failure. Not falling far, but our good friend F=MA helps us there. Especially with the loss of an upper beam between E and H, the one the cooling tower was being supported by, along with what it appears to be a portion of CMU wall for the PH corridor that needed external bracing on the opposite side, if this section were to collapse first, say only 2-3 floors down (We have to take into account the recounted story of the family from unit 904. They got very lucky in their survival, but their account does show that the collapse did have a pause in it between the upper floors falling and the lower floors falling. The upper floors outside the main hallway above units xx0 (I believe) and xx5 fell first and stopped at the 8th). This initial falling of or through the roof could have even been stopped by the cooling tower tether.
At this point, I am very uncertain of how the load redistribution would react, and what I am trying to figure out with all of the new information about repairs, weight, etc that I have found), but I believe this would have easily caused a massive shock force at the base of one or more columns somewhere at the lobby or garage deck level. Garage deck seems to be the place as indicated by the TikTok video. From then on out, the main collapse with the deck bringing down the building, and what we see in the security video potato cam, commences. The loss of the internal structure along those columns/rows, in my fully out there mind, could very easily explain the "void" the building collapsed into in the center, as if it imploded right in it's foot print, as well as the delay between the S and N sides of the building collapsing, as it's very clear the S section fell first at the main corridor line, followed by the N side of the building collapsing at that same line.
Extra waster weight on the pool deck is still a contributing factor as the rain over the days would have stressed that deck even more, and not helped the situation any.

To me, this makes total sense with what we see and does not seem all that farfetched. Yeah I have some crazy ramblings at times, but who doesn't have stupid ideas that need to get shot in the foot? We know these contractors deviated from the set rules. To me that's like throwing a bunch of color on a black and white painting. We can't just judge the painting for it's black and white work.

Before coming to this structural area of South FL, I came from a world where a .003" error missed in inspection can cause catastrophic unscheduled disassembly and loss of life. Things don't just blow up for no reason. Failures and multiple events typically lead up to the ultimate final incident. I don't care if ya'll think I'm crazy (Hey, his name is Demented, he must be insane!) or a conspiracy theorist. If I would have been allowed, I'd have been down there day 1 looking at the ends of rebar with a portable SEM. Sometimes there's blurred lines in tensile and shearing failures, and both can work hand in hand together. At least metal likes to hold it's final shape for us to see it's exact failure mode down to almost near the atomic level if you really really want to get crazy with it.


I'm still very curious to see the condition of these piles and if they are poured or precast. Yet another thing that hell, what could normally be moot of an additional 1mm of drop over years, could have been enough to put further stresses on very shallow rebar that was supporting the weight of cracked slabs that were only being held up via the rebar.

 

[Seppe]

LionelHutz and Ingenuity's posts directly above are a good summation of my thoughts.

I've been practicing structural engineering for my entire career, and I've visited this website for at least the past ten years (only lurking, at first). The structural engineering community on Eng-Tips, from my perspective, is a really good group and a fantastic resource. Their absence from the latter threads of this topic is telling.

As ashamed as I am to admit this, I check in on this particular topic perhaps once or twice a day still, with a sort of "trainwreck / can't look away" type of mindset as it relates to the posting itself. At this stage, quite frankly, the discussion is equal parts useless and flat-out embarrassing. The champions of the roof-first theory (you know who you are), for example, defend their own incessant back and forth as if it is some form of "no stone left unturned" analysis that others on here are just too closed-minded or shallow to consider. Guys... in reality, all you are doing is sensationalist babbling that, structurally speaking, is the easiest to dismiss. You so badly want to be right that you've blinded yourselves to the spirit of the original discussion. You just can't seem to abide any explanation of building failure that is a boring, highly plausible one, so you heap your efforts into tangential theories to create/maintain a buzz.

I'm sorry for even posting again, as it probably just sustains a topic that should have wrapped up at least five threads ago.

 

[Demented]

I'll again repeat a joke an old MSE prof told the class. This man was a well known SE/ME in the South FL area too.

A group of engineers took a taxi together to a convention. As they were driving through some farm land, the taxi driver says "Hey, look at that cow with one eye!"
All of the engineers covered an eye with one hand, turned, and said "where?"


I'm sorry if I've soiled your Structural Engineering thread. I didn't know this was strictly SE. >.>


Edit: BTW, I'm pretty sure finding the location of that upper roof and the stairs completely shoots down the theory of the upper wall tilting forward allowing unsecured A/C units to fall forward. So, you're welcome.

 

[davefitz]

Without the NIST report ( due in a few years) or the footage from the installed surveilance cameras around the pool, it is not likely that we can be assured of the root cause of the instant failure. However, all of the above discussion points can point to a direction for upgrading future inpsection procedures and regulatory statutes.

It was reported that some insurance companies are already pulling out of the market for insuring buildings designed prior to the year 2000 upgrade of Florida building regulations . That could lead to a lot of older condos being uninsured, so the units would need to be purchased for cash without bank loans. That suggests a step change in value for the older units is forthcoming. Another evolutionary approach might be to duplicate the de facto process in Hawaii, where the condos have a fixed ( 50 yr ?) life related to their initial land lease life, so a known end of life is prescribed in the purchase agreement.

Not yet discussed above is the interesting theory that the garage floor slab was not directly supported off the pier caps, and that allowed a reservoir of salt water to accumulate under the slab and attack the support piers in a manner that cannot be examined without removing portions of the floor slab . I guess we will just have to wait for the NIST report, hopefully not compiled using political science.

"...when logic, and proportion, have fallen, sloppy dead..." Grace Slick

 

[microwizard]

Pretty much the only thing this thread is now demonstrating is that the Dunning-Kruger effect is alive and well.

 

[JStructsteel]

@ Mocrowizard, LOL!

 

[sbisteel]

 

[Optical98]

Demented

I was looking at a few photos of the roof area, there does look to be some measures were being taken to "try" and help the stability of the corridor wall, ie...it was unstable.

Link

Link

Link

What is the point of the rope or cable tying off that walkway, in section 2 there is that odd brace looks as if it's helping hold up that wall and the last image, the area doesn't look squared and you can see the deep moisture lined areas from the upper corridor wall. That wall is directly connected to the PH that complained to her son about the creaking and groans waking her up at night.

 

[Optical98]

I'm just going to say that I have not offered up even one conspiracy theory.

I have offered evidence of contributing factors to the overall failure, my first post was regarding the weakness of the generator room slab. My further interests have been that there is evidence of a fire or some sort of combustion on the north side of the building...where there just happen to be many combustible factors.

I've not put forth a formal hypothesis because I can't say what happened first, the collapse or a fire, but I will continue to peruse and gather info as I find it.

I also sometimes come across items that may help others in their perusals, and enjoy the bits of humor we find along the way.

Grown professionals can conversate without calling others "Trash" and "Stupid". If you have nothing to add to this thread other than badgering or name calling, you should be embarrassed.

 

[LionelHutz]

Theories and speculation have been called stupid, not members. Who should be embarrassed exactly, the ones posting theories with absolutely nothing to back them up or the ones calling those theories out?


As an example, the amount a building would have to shift to make a door 1" out over 3' is a lot. I can't envision any way the one side of the frame dropped that much while the other side remained in place without there being major wall damage to fix. I'd be much more inclined to chalk that up to poor construction with the rough wall opening not being constructed square causing the door to be installed crooked.

 

[Optical98]

LionelHutz

I don't recall a theory on door alignments, perhaps that was just an observation?
Sometimes several of us have come across a picture, a permit, differing plans and conversed over what was followed thru on or not... those are not theories.

But I have found usually when I ask questions....as in there were plans to install a natural gas line...did it happen etc. I get very good feedback.

You went on about my mention of a white car or 2... if you go back to where that all started, I've never been on the vehicle vs column team, not bashing them... I just happened across a picture that looked very much like a wheel inside a column.

Demented quickly corrected my vision, and several of us saw the humor in it, but there are still some question as to what happened to that particular car, it was involved with the NW portion of the collapse, in so far as it was dented and the airbags inflated. Possibly from falling pipes, we don't know and there was NO THEORY put forth..

But no one can outright claim one way or another that their theory or hypothesis is the absolute truth atm.

I feel like with the number of sock accts at play, I can't be sure who I'm conversing with anymore - this is my only acct. And I feel like some are trying to turn this into a 4chan monkey show with propping up their own opinions and then demeaning others.

 

[Demented]

An observation. One where nitpicking over slight, and I mean slight, trapezoidal shape was noticed. Less than 4mm at most. I have no idea how that grew to an inch.

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

 

[Santos81]

in so far as it was dented and the airbags inflated. Possibly from falling pipes, we don't know and there was NO THEORY put forth..

Curtain Airbags (not to be confused with side thorax airbags), will deploy if there is deformation of the roof structure without regard to the operational status or vehicle occupancy.

 

[davefitz]

Wow. Sounds a bit supercilious to disqualify any comment by any person not listed as a structural engineer. It seems to be conveniently forgotten that the catastrophe occurred primarily due to a substandard design provided by a structural engineer, was inadequately inspected and analyzed by a structural engineer, and that the implications of a collapse of a residential building designed and inspected by a licensed structural engineer threatens every member of the public, including those that are not licensed to practice structural engineering in the state of Florida. It would seem that it is too soon to discount any possible failure pathway , and the theories submitted by structural engineers are no more or less possible than those of other observers at this point in time, aside from those that are physically impossible.Methinks thou dost protest too much.


"...when logic, and proportion, have fallen, sloppy dead..." Grace Slick

 

[Red Corona]

> @LionelHutz To me, that column without lower level balconies is ending with the 11th floor balcony right above the windows with lights on

That just goes to show that different people will see what they think they already know, when presented with unclear imagery. To me, frame 3 (the one I posted in my comparison pic), and also 18, clearly show the strip of separated windows below the 12th floor balcony going up one floor above the lights. Frame 0 (although full of artifacts) and 1 also appear to show something where floor 13 should be, at the right hand half of the collapse area.

The 13th floor should be present over the double pillar, and the right side, but not over the left side (there was no floor 13 there). I'm struggling to see in your version what the visible structure on the left side on that floor is.

I also put the (not under dispute afaik) floors on the right side in so we can see how much the building has dropped. In my interpretation the camera has actually triggered pretty much at the start, the floors still align well, only floor 13 is missing, and it looks like (with the eye of faith at least) you can see that collapse in frames 0-2.

> @Santos81 Most of the “lights” in the x10/11 stacks are reflections from glass that is no longer in place. The two bright flashes from the X10 stack are reflections from a fire alarm signal on the exterior landings of stairwell 1. There are a couple of exceptions but it’s a very macabre subject I don’t feel is appropriate to discuss in detail.

We're looking up from ground level, what are those windows reflecting? Surely we'd be looking at the sky reflected? The 'lights' in 911, 1011 and 1111 look like real lights. But yes, if they're real lights that means people turned them on and didn't get out in time - nicer not to think about that. I don't think it's particularly relevant to the engineering 'what happened' side.

Do you know what floors those fire alarm signals were on? That would clear up which floor is which.

@Demented/@Optical - there is definitely bad news involved in that roof/PH floor.

Here is my attempt to make a plausible 'roof first' story. But I'm still not convinced - it just seems a huge coincidence that two separate bits of the structure would be in a bad way at the same time.

- The day before, roofing contractors get up there and cause some roof level overloading (bad roof anchor drilling sites hitting some rebar, or putting heavy stuff on the roof of 13, or something)
- The penthouse roof slab starts to puncture with the roof columns at K/L/M 9.1. It doesn't collapse, because it's still supported by the walls, which aren't structural but they're still well built enough to take a single slab load. This causes the 'creaking' (slab top rebar ductilely failing in tension around the puncture? load redistribution noises) heard be 1211 the previous night. Nobody notices because the deflection is small and the slab is hidden under roofing material
- Failure continues and the next night the walls and roof columns fail. Initial stages cause 'construction noises' (as per 111) as load changes in the structure. The PH roof crushes floor 13's facade (spraying glass from the balcony windows and dust down in front of 111) and falls down onto floor 12's roof.
- Some or all of the roof parapet falls onto the planters in front of 111, this could be the 'loud crash like a wall falling'
- This extra load causes the pool deck to fail and we know the story from there

Alternatively, the failure causes a redistribution of load which affects M9.1 and causes the M9.1-M11.1 beam to detach from M9.1. This then puts the plaza slab into overstress and starts the plaza failure, without anything falling. In this version the failure of the PH roof 'sounds like a wall falling' (because it is), and that noise is transmitted through the columns so is loud in 111. This also wakes up 611 but she was asleep so didn't register it consciously.

I still favour a plaza-first failure, but if you think that frames 0-2 of the collapse show floor 13 collapsing first, perhaps a partial failure of M9.1 from the loss of support from the pool deck is what causes the roof slab to let go.

 

[LionelHutz]

Since you asked, I looked again and yes from the start all along I have actually believed the lights are on the 11th floor which puts the 12 floor balcony above the lights and the the double rows of parapet above that. I'd get the floor numbers right if I would stop counting the roof parapet as the balcony for the 13th floor.

I don't agree with the angles on your right side floor lines.

 

[Santos81]

We're looking up from ground level, what are those windows reflecting? Surely we'd be looking at the sky reflected? The 'lights' in 911, 1011 and 1111 look like real lights. But yes, if they're real lights that means people turned them on and didn't get out in time - nicer not to think about that. I don't think it's particularly relevant to the engineering 'what happened' side.

Do you know what floors those fire alarm signals were on? That would clear up which floor is which.

They’re reflecting the ground lighting. The exterior luminaries are not the only part required to be sea turtle compliant; the glazing is as well to minimize interior light transmission. The only interior lights that are visible in the footage are at locations where the balcony doors are either open or the glazing units have detached from the envelope or shattered before power was lost. Several balconies were occupied. People seem to be omitting material displacement when analyzing the footage.

The flash heads are on the north elevation of the floor landings at every floor. I believe the artifact I circled in red is from one.

 

[SFCharlie]

that's good work, but I don't see it proving anything.

Right, All I think it proves, is that I was right several threads back, to say that a video from a smartphone, whatever, of a security system display, that's out of focus, (and compressed in the phone and again in YouTube) is practically immune to analysis.

SF Charlie
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[Auri]

As a reminder, closest-to-original public source of the video is at:

https://twitter.com/wsvn/status/140...g-collapses-in-florida-watch-video-young-pan/

Fullscreen, pause, scrub. I'm seeing too many transcoding artifacts like blurriness and repeated frames on Youtube or other Twitter sources.

The two bright flashes from the X10 stack are reflections from a fire alarm signal on the exterior landings of stairwell 1.

I don't think that can be. Those flashes illuminate a bit of the left side of building, and they last way too long. Were the light sources from the opening next to the western stairwell, they'd illuminate a good chunk of the mid section building instead. They'd perhaps be synchronous unlike in the video, and much shorter than electric sparks. A typical xenon flash is 5 microseconds. (One can be seen on exposed 13th floor passageway - two strobes, a few seconds, another two strobes, each strobe occupying exactly 2 frames.) A typical arc/induction spark is ~10 milliseconds and the were 12 tubes going east from each meter room. A single exposure at 30 fps naturally maxes at 33ms.

Edit: I see the fixtures on every floor in the surviving open area next to stairwell. I'm just not sure they flashed at all. Maybe they're unusually dim for how recessed they are, or you'd expect almost uniform illumination bouncing off building or smoke.

Also some of those window lights were not reflections... too square, and reflections move as the building tilts. The flecks seen in 1112 and then 912 could very well be reflections. The lights that vanish at the same time as 1209, not so much.