Miami Beach, Champlain Towers South apartment building collapse, Part 05 111

[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


SF Charlie
Eng-Tips.com Forum Policies

 

[zebraso]

The new inverter driven compressors have almost no torque steering of chassis

The starting torque requirements for traditional ac induction blower motors is low. You can start them with your little finger if the run capacitor goes bad. From there it's smooth even acceleration. Mine is not bolted down and it does not ever shudder slightly on start up. There is very little internally generated peak force being expressed to the frame. The fan motor torque could never ever move the base or threaten is security.

 

[JR97]

A note about the mystery cylindrical object in the tictoc video; I agree it looks like a garage ventilation fan. But the recent YouTube video with the lady walking through the garage in 2020 does not show any similar ventilation fans. The picture SFCharlie reposted is not from this garage. The paint on the columns is wrong.


I am not sure about the entire penthouse roof hinging as a solid slab. If the infamous roof anchors caused something to fail, I think it would just be the cantilevered roof over the balconies and the parapet wall.

That may well be the trigger that caused the mostly agreed upon initial failure of the pool deck. I find it very likely something atypical happened to the pool deck to initiate the failure. As it has been mentioned, once the deck failure began the rest was inevitable.

JR97

 

[waross]

Rheem hold-down strap.

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

 

[Js5180]

I was the one that posted the ventilation fan pic so I wanted to clarify - it was not a pic from this building. It was used as an example. I apologize for any confusion.

That said, the renovation plans DO show a “jet fan” in that approximate location. I could not find a detail showing what model fans they were, and we don’t know if they were installed or not.

I continue to think that some degree of early damage occurred on the western penthouse roof - these images is from the surveillance camera’s perspective, and includes the camera itself. The drop of this middle area is not well explained in the context of the lights still being on. Both theories need some work, and there isn’t much to prove or disprove.

It’s incorrect to say that it’s impossible because nobody reported falling objects. How many people were watching before the booms?

As for occupants on the upper floors or in x10/x11 above floor 7, we don’t know if there ere any that night. The lack of complaints doesn’t mean there wasn’t an event there.

Finally, a roof collapse could have occurred even seconds before the main collapse, and that would explain the missing parapet. Again, I don’t see how any of these theories can be ruled in or out at this time.

 

[jbourne8]

Js5180, We actually do know that people were on the 10th, 11th and even the 12th floor. This is a bit outdated now, but it shows who was upstairs -

https://archive.is/QmPiY

I guess it's a bit more thrilling to think that you can see stuff from the roof on the garage door in the tiktok video even though it's really grainy, but it can easily be explained by stuff that's sitting on the pool deck that we know has collapsed there. If all of those shapes are items from the roof, where are all of the large planters, circular tables, etc from the pool deck. Also, I think you can see the column lying on the ground between 27 and 28 on the floor there, with the top facing towards the southwest and the bottom covered in rubble. It's more obvious in the original video than it is in the lightened photo though, because it's the only thing that's clearly painted white.

Sym P. le, That before garage photo is a bit off too.. the streetview pics from 2011 are a closer perspective and you can just barely see the column towards the top of the screen in that one. I believe they were posted around part 3 or 4 though, so I'm not going to post them again.

 

[Js5180]

The round object in the tiktok video is not readily explained as an all-black table. It appears in the video as a cylinder, with light colored walls, and a concentric circular opening that’s darker.

Saying it is more likely to be a table ignores the obvious - it just doesn’t look like a table.

As for the green, I think the green in the tiktok is way too artificial and man made to be plants. The fact that an enhanced picture was able to bring it out so easily suggests it is very consistently colored.

 

[Demented]

If an AC unit falls off a 12th floor roof and hits the ground, that's what, 4,000lbs of force give or take on impact? If that will make the pool deck collapse, then the building was absolutely doomed come morning time when everyone was leaving for work.


With how much it's been raining down here recently, and how poor the drainage and waterproofing in that area was, I don't find it unlikely at all that there could have easily been 3" of water sitting just under the surface of the pavers. Even as first responders were first getting there, water was puddled up in spots that had yet to spray with hoses and had not had water mains leak on.

How much water weight could potentially be on that slab? Seems likely far more weight than that of any falling AC unit.

 

[jbourne8]

Js5180, That photo has been lightened.. check out the original video -

https://www.tiktok.com/@adrianitacastillero/video/6979296632919706886

To me if very obviously looks like a shiny black table, it even changes colors as she zooms in that hints that it's glossy, flat and reflecting some light from the garage. Also, glossy black tables can look grey too in photos btw.. and how the glossiness shows up, especially at low resolutions, can sometimes seem like there's an inner circle. The green bushes in their planters were also quite large, and that photo is lightened which can make colors look more consistent than they actually are. I guess I'd find the roof theory more believable if we could see pool deck items as well as roof items, but it seems to be one or the other.

 

[bones206]

I attempted to overlay the parking spot plan on the framing plan to help with cross referencing. It's not perfect but it's as close as I could get it.

https://files.engineering.com/getfi...e=Lobby_Framing_with_Parking_Spot_Overlay.pdf

 

[bones206]

Another overlay with the planters and test probes superimposed on the framing plan and parking lot plan.

https://files.engineering.com/getfi...Spot_and_Planters_and_Test_Probes_Overlay.pdf

 

[bones206]

@Demented - good point about the water weight. Do we know if there was a drainage system installed prior to the collapse? It looked like white pvc drain pipe was hanging below the plaza slab in the parking garage tour video. But that may have been for something else.

The planter soil may have been quite saturated as well.

 

[Seppe]

The "impact by falling roof stuff" theory is certainly sensational in comparison to the more pedestrian "highly-deteriorated, minimally-redundant plaza slab system gives up ghost" theory.

For the roof-based theory, it sure seems like there needed to be a chain reaction of components experiencing there own acute, sequential worst case scenarios.

For the deteriorated plaza theory, all it really needed was father time and breakdown of inherently impermanent / imperfect systems.

Something cut this building's legs out from under it. I personally lean towards the plaza deterioration theory. At the same time, the falling roof debris theory isn't an impossibility.

 

[bones206]

Just a few observations of this particular area.

 

[aggualaqisaaq]

Reposting coz I mistakenly posted this on the old thread:


Another possibility: the water in the video wasn’t coming from the sprinkler lines. Didn’t the planters have some sort of automatic watering system? Perhaps the pipe that broke was related to that?

(I’m not necessarily endorsing this theory; just putting it out there as another possibility)


“NOOK-yoo-ler. It’s pronounced NOOK-yoo-ler.”

 

[Demented]

@Demented - good point about the water weight. Do we know if there was a drainage system installed prior to the collapse? It looked like white pvc drain pipe was hanging below the plaza slab in the parking garage tour video. But that may have been for something else.

The planter soil may have been quite saturated as well.

Ah, the planters. There's a chance those were full of water too, and I mean FULL.

3-4 years ago a contractor from the Miami area hired me to make some planters for a well known hotel down there. Wound up not doing the job, but his plans called for 2ftx2ftx10ft planters with no drainage, and mounting tabs so he could just lag bolt it down to the concrete where they wanted it internally.

I don't think a drainage system was installed prior to, or work had even begun on fixing the issue with the drainage. I'm an hour north of Surfside, and up here, from the 21st to the early hours of the 24th, we received 2.44" of rain, and it's been on the drier side here compared to more south. It's been mostly cloudy too, and water has just been sitting here in puddles. Especially areas where there's a lack of drainage, 3-8" of water easily pools up where allowed. Sloped drainage areas with clogged drains, especially around landscaping day or windy days when lawn debris is everywhere, are all too common.

Even though there is a pipe hanging, that may have absolutely nothing to do with the fire system. (Plus, if the penthouse collapsed first, where were those fire system alerts?)
The slab could have fully cracked through, or even epoxy injection repairs could have failed, allowing the sitting water on top to start to flow through cracks, which could explain what we are seeing. To me it looks like no more than a small amount of water being poured or drained, similar to the amount you'd see coming from a gutter/drain system, not a pressurized system for fire suppression. I've seen those break first hand, and you actually get gushing, not the slow, 80 year old man prostate dribble coming from the upper deck in the tiktok video.

Precision guess work based on information provided by those of questionable knowledge
Aerospace/Industrial/Medical/Structural
SoFla

 

[Sym P. le]

You are building the argument. Tons of water plus junk from the roof may be the difference.

 

[Demented]

If 1" on 1 acre is 113 tons, then quite literally tons of water.

Precision guess work based on information provided by those of questionable knowledge
Aerospace/Industrial/Medical/Structural
SoFla

 

[CE3527]

bones206 - I feel pretty strongly that the deck collapsed first. It's hard to know the exact origin with the available evidence. What you suggest is a strong candidate. The other area of interest to me is the at grade parking area south of the lobby and west of the pool deck. This area was also in poor condition based on the reporting and videos. It too had planters but unlike the pool deck, there is no evidence this area ever had waterproofing in its 40 year history, then add in the live load of cars backing in and out for 40 years.

I also feel pretty strongly that failure at the area you point out led to the eventual collapse of the building. Start on the basis that the deck collapsed first, and then ask why some parts of the deck simply punched through supporting columns or sheared away from the structure, yet this particular portion of the building collapsed? Then ask, what is different about this area? The answer to that is that this area had a stronger connection to the building than any other area of the pool deck because of the beams supporting the step down terrace. And therefore, the most likely area of the building structure to be impacted by a failing pool deck.

 

[BKNJ]

There are some question on Reddit if Cassondra Stratton was in unit 412. Since the body of Miguel Pazos, the owner of 412, was recovered in the rubble. Apparently, the unit Cassondra has taken selfies from recently is a x10 unit, possibly 410, it's possible she moved units.

This would, to some degree, change her view from the balcony.

https://www.reddit.com/r/Catastroph...z?utm_source=share&utm_medium=web2x&context=3

BKNJ

 

[Js5180]

Let me explore this from a different angle.

Let’s look at the column M10 stack - this is next in the row, west of “27”. I’m pretty sure most of us agree this column was compromised and played a major role in the collapse (even if not the trigger).

The roof extends a good bit past M10 - I’m estimating 8 feet. At the edge is a CMU parapet.

If M10 has sunk and M9 has not, then the roof will slant outward. The outer face of the parapet is now inches over the edge of the building.

At this point, doesn’t the parapet now become the weakest link? The rest of the collapse portion, when it falls, is tied together. The parapet is now a few degrees off vertical. It is held on only by a few bars. We saw in the controlled demolition - a section of parapet actually separates from the roof in free fall.

Each foot of the parapet weighs about 288 lbs. Each foot of cantilevered roof, on the south wall, weighs about 900 lbs. And that’s a 6” waterlogged slab which appears to be exactly where some level of roof work was being done. It would take very little “sink” in columns K/L/M to cause that parapet to lean or that cantilevered slab to bounce like a diving board.

The parapet, in my estimation, would almost be expected to break off, even with the slightest drop in one of those column stacks.