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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[tmwaits1]

I appreciate your post. We are trying to walk a fine line between being skeptical of new theories but also open minded if the evidence points in a new direction. I think we are at that point with what, to my eyes, shows the pool deck area column basically destroyed prior to the main collapse. Your theory about the catenary action of the progressively failing slab pulling the column over may be 100% correct. I feel like another plausible explanation is that a section of the roof fell down the facade of the building and impacted directly on top of this column. Looking at the first second of the video from next door and comparing it to a shot showing the existing roofline looks like prior to the main collapse, a section of the parapet is missing. Let me reiterate that I am not wedded to any particular theory. I want to look at the evidence we have (however imperfect that may be) and form the most reasonable hypothesis on why the collapse occurred. I also think the original design was probably flawed in many ways and was a major contributing factor.

 

[Js5180]

Rodface,

The reflection theory is interesting and I’ll have to take a look. It does appear that that particular “light” gets tucked under, which would be consistent with a reflection.

I did notice that the red light on the top of the elevator room, which I assume is an aid to navigation light for airplanes, is on a circuit with a white light to the far right of the eastern wing.

As for the parapet, I don’t think there’s any question most of it was there, but in the earliest frame, it’s hard to line up. Try drawing the same lines in that frame.

My theory is that the upper roof collapsed before the main collapse, by as little as a few seconds or as much as 15 minutes. It could be a trigger or a result of shifting elsewhere.

And Allyn isn’t drilling that roof slab for nothing. I’m not going to say that a washing machine fell off the roof and brought the pool deck down, but I do see it as a weak link that could have contributed to the collapse.

One other point - in most pics, the rebar looks relatively clean. However, the ramp column, which I think would be M8, looks really bad.

 

[1503-44]

We should be seeing some evidence of the missing parapet theory come to light very soon, if not already. As I said above, the last photo with a supposed parapet looked a bit beefy for a parapet. Its basically not a load carrying member and most likely not more than 8" thick. Has anyone seen that piece dimensioned in a design drawing anywhere.

I think that theory might be getting less probable by the minute.

 

[1503-44]

I'm kind of a stereoscopic photo fan. When I first saw that video, I lined adjacent frames together to view a stereoscopic image in a 3D type viewing perspective. Since many things are moving downwards, rotate them 90° to the right, to minimize the appearance of 3D displacement in depth from the downward motion and it helps. Those lights did seem to have a reflection characteristic, as they seemed to be a bit in front of the action, rather than from behind. Another thing was that I believe the camera was swaying from the seismic vibrations, as one duo of pictures will appear to be displaced a bit forward from their adjacent pairs. These don't take a lot of motion to distort depth. Anyway I was impressed as to the apparent depth of the hole that opened up below what seemed to be the roof, or a good portion of it, that I thought it looked like it was trying very hard to remain horizontal. Well, if you like that potential method of seeing some depth there, I thought it was interesting for awhile.

 

[pellucidar]

I think that Cassondra Stratton lived in 412, not 410, based on an evaluation of her recent blog photos, which show her in a unit that she just redecorated at great expense.

Cassondra previously lived in 412, but moved within the building last year, probably to 410. She blogged extensively about the first place, but not so much about the move. The reddit thread I linked has more details.

 

[CE3527]

Ok, here is a hypothesis which accounts for M11.1 being "missing". It can extend to include K11.1 and L11.1, if the evidence requires a similar failure mode for them.

Murph - In agreement with your post, just a minor clarification. We do know what happened to K11.1. It failed in punch through and can still be seen in the post collapse photos. But I agree that L11.1 and M11.1 may have failed differently (together or separate). One difference between patio support beam at L and M, versus K is that the raised patio extended further from the building than along line K. That would suggest to me that these beams had better capacity to resist bending than beam along K. This could have accounted for a different failure mode

Whatever was left of L11.1 and M11.1, whether they were destroyed before the building collapse or not, was buried under the rubble. I'm sure they got heavy scrutiny during the cleanup.

 

[tmwaits1]

The 4 ft tall parapet is comprised of reinforced concrete columns at 20 o.c. with a reinforced concrete cap beam and CMU wall filling in between the columns. Maybe there are some other notes or details in the plans but this only states that the column is tied to the slab with 4 -#5 bars.

 

[pellucidar]

It would be nice if we could take the non-engineering related subjects back to Twitter, or wherever they belong. It sure isn't here.

If you're complaining about Cassondra, she was a witness to the patio deck collapse so her location at the time she saw it is relevant.

 

[rodface]

Question for the guys who build buildings: If I am not mistaken the objects circled in green are the scuppers that drain from behind the parapets. But what are the items circled in red? This is from the Google StreetView of 87th street looking up at the top of the façade that came down first.

Edit with a W.A.G. - condensate drains embedded in the floor slab? That they chipped out when they built the penthouse?

 

[Penagwin]

Just found another video I haven't seen mentioned, it's from a video of a Hurricane Wilma in 2005.

https://www.youtube.com/watch?v=X4BwnI0VyPM

Around the 3:30 mark there appears to be a shot of the pool/patio deck and it looks rather torn up. Can any structure/civil engi tell if this is cosmetic or if it would have prompted repairs, etc? It looks pretty bad to me.

 

[rodface]

@Penagwin great find. That's the toppled wall between the pool and 87th street to the south of the building.

 

[Santos81]

the objects circled in green are the scuppers that drain from behind the parapets. But what are the items circled in red?

Green are the overflow scuppers, red is balcony drainage (added in 20xx)

 

[spinspecdrt]

Ungrouted CMU wall. I don't see any rebar. It wouldn't take much to blow that over.

 

[rodface]

@Santos81 interesting. I would have thought that the scupper sufficed as a balcony drain, but perhaps it ended up too high or too far off to the side? Though if I entertain wild thoughts without enough evidence... if the drain on the RHS was inadequate, and water was flowing/pooling to the LHS enough that additional drains were needed... could that be indicative of slight settling beneath those drains? To carry that thread further: is the balcony itself sagging, or is the building somewhere below descending by 2mm?

 

[Nukeman948]

 

[Santos81]

I would have thought that the scupper sufficed as a balcony drain, but perhaps it ended up too high or too far off to the side? Though if I entertain wild thoughts without enough evidence... if the drain on the RHS was inadequate, and water was flowing/pooling to the LHS enough that additional drains were needed... could that be indicative of slight settling beneath those drains? To carry that thread further: is the balcony itself sagging, or is the building somewhere below descending by 2mm?

The overflow scuppers were not the primary RW drainage outlets for the roof or UPH parapet balcony. Their base elevation was 7” above TOS and incorporate spring loaded doors. It would take approx 10” of water before they will open and it’s not subtle. Definitely wouldn’t want to be standing under one when it does. In Miami, Flat Roof systems utilizing scuppers as primary RW discharge to ground on Mid-Rise and greater structures require downspouts. I marked the original balcony drain on your photo. For the given drainage area, one outlet definitely was not sufficient and interior flooding would occur before the overflow would be reached.

 

[jbourne8]

I edited the Ring video to have a more realistic (but very hypothetical) tilt, and tried to end it with the least tilt possible to cause the table and camera to slide across the table/floor like they did. This really doesn't capture how much the room is leaning towards the camera by the end, but that's impossible to illustrate in this video. I then compared it to the CCTV footage in the second half of this video. I think the rushing sound in the Ring video is the upper floors collapsing, and more than anything this illustrates how long the building had been falling apart before the CCTV footage begins. I placed it where I did too because we probably only lost around 100ms when the power cut out to that area. Warning you now though, this is a pretty horrifying version of this video.

https://youtu.be/8FNkJrHPBKQ

Mostly I think this video shows how weak the roof theory is, since it hinges entirely with this CCTV footage that begins way too late to be that helpful. I also had an AC unit that fell off my building once and down 4 stories, and it wasn't exactly square shaped anymore when it was picked up off the sidewalk. They aren't constructed that well, and I really doubt they'd be identifiable in the tiktok video. I think if this was as simple as the roof causing the collapse they would have announced it by now and wouldn't be panic inspecting and closing old buildings in Miami too.. a chunk of parapet at the bottom of the pile shouldn't be hard to find. It also doesn't really match up with the statements from people at the collapse.

 

[rodface]

@Santos81 Got it. Those figures surprise me. Does that mean that a flat roof equipped with a parapet and scuppers as described would collect and hold a considerable amount of water before it was able to drain through those devices? I am somewhat ignorant on the subject, but I have to assume that the roof would be designed to shift the water to some other means of collection/discharge and would not be designed with the expectation that it would regularly hold up to several inches of accumulated rainfall?

@jbourne8 this edit somehow makes the scene appear very realistic.

 

[1503-44]

Generally one would expect roof sloping to centralised catchment points and drain pipes from those to ground level. Only runoff from the balconies would normally be directed outward and overboard.

The anchorage of the parapet looks like it is sufficient, if it was in good condition. A column at 20" o.c. and the top tie beam would be all that I would expect, if that much. The dimension of 8" thickness was exactly what I expected. I'd say, if in good condition, it needed quite a bit of help to get knocked off the roof.

So to see that on the ground, we look for 8"x8"x16" CMU bits with some sand-cement morter columns on each end. The columns cannot be more than 4" wide and they have only one 16" long block between them. Anything else would put the columns at > 20"c/c. So, probably adequate, or more so, but probably not very chunky when broken into pieces. The cap beam would most likely form the largest remains of that assembly.

 

[Optical98]

I have found it almost impossible to find images or video of the Western exposure/Front of the building post collapse. There are some aerials but they are mostly focused on the eastern side and rarely get low enough to view the Drive Thru Lobby area. After much footage scrutiny I finally found 2 that had such vantage points. It seems like they were keeping everyone away from the front of that condo at street-level, and rushed to demolish it asap.

I wanted to find this angle because several survivors that did go down the stairs all the way to the basement, they mention flooding and that the roof or ceiling was crumbling down..this causing some to return back up the stairs and to balconies.

Here are a few stills I grabbed from videos and as someone else mentioned above, here we go analyzing crap photos.... Actually I want y'all to analyze them and tell me what you see.

Zoom in, what is going on with the drive thru overlay?
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From a different angle, I've circled a few things, one is a ladder...but why is it braced between the truck and planter? (I've wondered if that truck backed up too far and bumped the retaining wall). But beyond that what are the other items?
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