Miami Beach, Champlain Towers South apartment building collapse, Part 03 148

[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

Thank you

SF Charlie
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[Vance Wiley]

I recall the deck area was a concrete slab, waterproofing, sand, mortar bed, and the paver tiles.

This was posted by bones206

https://res.cloudinary.com/engineer.../tips/Screenshot_2021-06-29_105802_tzq8wh.png

 

[Retiredat46]

One thing I noticed in the video of the North Tower is the condition of the ceiling in the garage. One part looks moldy and discolored while the other part is nice and clean. I assume the clean part is under the building itself, and the other is under the pool deck and patio area where water is getting through the concrete from above. Is there any other plausible explanation?

 

[dold]

Back in the day, we'd design for lateral using X brace and moment frame. If we had a "shear wall" we would not consider that it actually resisted anything. It was an entirely redundant element.
Now it seems to be the only thing keeping the rest of the things upright.

Not to discredit your experience, but this is not at all the case with concrete frames.

In steel structures (building frame systems), the lateral systems are ~95% braced frames / moment frames as you mention. In concrete structures, it is EITHER concrete shearwalls or concrete moment frames (with a few exceptions - not relevant to this discussion).

In the case of this building, it would be entirely appropriate to use concrete shearwalls as the lateral system. Granted, the 'amount' of shearwall provided in the east-west direction in this building is woefully inadequate. Any practicing/retired structural engineer can see this without doing any calculations whatsoever. Literally two 8ft, 10" thick shearwalls for a 12/13 story building... There is no explanation for this in my opinion. 175mph wind, exposure D in this direction, youre looking at ~1500kip ultimate base shear. Considering half of that goes to each wall, shear stresses are nearly 800psi. Design strength of these shearwalls (10", 3000psi, #4 at 12" o.c. e.w. e.f.) is about 150kip. There are tons of (seemingly) non-participating masonry walls that certainly contributed to the lateral strength of this building. Otherwise, there is no way this building could withstand hurricane force winds.

 

[Sym P. le]

The higher dark ceiling is under the living space and is coated with additional material. The pool deck level is 1'-6" lower and uncoated. The exterior parking and entrance drive is a third intermediate level.

 

[Js5180]

I wouldn’t assume that any detail of the north building is identical, nor that one is an improvement over the other.

My sense, though, is that the north building plans are actually older, and they were expanded for the south building based on additional lot area.

I say this because in my lay opinion:

1. The shear walls are reasonable for the north tower but arguably insufficient for the long east wing of the south tower.
2. The aesthetics of the north tower balconies are better than the south tower’s, on the inside corner.
3. Subsequent engineering projects are usually focused on maximizing value, not improving aesthetics beyond the original. See: DC-9 and every Boeing that was ever stretched after the initial release. See also: the Great Pyramid. See also: One and Two Liberty Place in Philadelphia. In almost all cases, the later structure is an uglier, more economized version of the original.

 

[Js5180]

Dold - I am equally floored by the weak structure here. I am a layperson that built a two-story house that I live in and I was required to build basement walls that were 14” thick and with #4 8” OC. At the time it was maybe a few yards of extra concrete and a few more wire ties, and yes, sure, it was 3500 mix. I also had a lot of #5 bar in critical areas.

But to hear that a 12 story shear wall was only #4 12” OC - wow. I had always assumed that you’d never even find #4 in anything like a column or a shear wall or anything commercial other than a plain old slab.

 

[Retiredat46]

The higher dark ceiling is under the living space and is coated with additional material. The pool deck level is 1'-6" lower and uncoated. The exterior parking and entrance drive is a third intermediate level.

So I got it backwards. What we see is the deterioration of the added coating on the underside of the slab under the living spaces. That makes sense, and it's not as alarming as I thought. Thanks for the correction!!

 

[IEGeezer]

https://www.youtube.com/watch?app=desktop&v=arUOCTDRnCc

The subtitles in the video are more accurate than the auto generated ones. This is a quick and dirty as many who don't understand Spanish may find the video more interesting with a better translation.

00:21 Estamos en el edificio gemelo, pero aquí

[We are in the twin building, but here]

00:24 uno llega con el auto ingresando por

[one would arrive by car entering from]

00:25 Collins en rumbo hacia el norte y tenía

[Collins going north and you had to]

00:29 que dejar el auto aquí.

[leave the car here.]

00:31 Miren qué bien que se ve. Parece muy

[Look how good it looks. It seems very]

00:34 seguro, muy bien mantenido.

[safe, very well maintained.]

00:38 Ahora estamos subiendo por la escalera que (se) colapsó.

[Now we are going up the staircase that collapsed.]

00:41 Esta es la parte que dá a la playa.

[This is the door that leads to the beach.]

(Music)

00:50 Estas son las puertas de ingreso a los

[These are the entry doors to the]

00:54 departamentos que (se) colapsaron.

[apartments that collapsed.]

00:58 Esta parte que es la puerta de ingreso a tu

[This part which is the entry door to your]

01:00 departamento, ¿Hubiera quedado en pié?

[apartment, would it have stayed upright?]

01:02 Sí, esta parte sí. este departamento, este creo que se hubiese

[Yes, this part yes. This apartment, this one I think would have]

01:05 cortado por la mitad.

[been cut in half.]

01:09 ¿Víste que se vé entre los balcones,

[Can you see that you can see between the balconies]

01:11 cómo que la parte del edificio se vé abierta?

[how that part of the building looks open?]

01:12 Yo creo que es este departamento,

[I think it is this apartment,]

01:13 las habitaciones de este departamento

[the rooms of this apartment]

01:15 Creo que acá el techo te da un poco la idea de done se corta la...

[I think here the roof gives you a little bit the idea of where the..]

01:17 El muro de corte. O sea que si

[The plane of the cut. In other words, if]

01:21 estuviéramos en el otro departamento, a

[we were in the other apartment, from]

01:22 partir de esta línea, dando un paso más

[this line on, taking one more step]

01:25 hacia allá, ya no habría nada, sólo el mar.

[over there, there would be nothing, only the ocean.]

01:29 Estaríamos viendo la montaña de escombros.

[We would be looking at the mountain of rubble.]

01:33 (Music)

01:38 Así eran los balcones

[This is what the balconies were like]

01:40 del edificio colapsado porque es el

[of the collapsed building because it is]

01:43 mismo diseño arquitectónico, la misma

[the same architectural design, the same]

01:45 empresa, el mismo estilo.

[builder, the same style.]

01:49 Para que vean ustedes, cuando ven ese

[So you can see, when you see that]

01:53 colapso progresivo

[progressive collapse]

01:55 cómo los balcones se fueron apilando, uno

[how the balconies stacked themselves, one]

01:59 arriba del otro.

[on top of the other.]

02:01 ¿No hay nadie en el edificio ahora?

[Is there anybody in the building now?]

02:03 Hay muy poca gente. Cómo te habrás

[There are very few people. As you may have]

02:04 dado cuenta, el 80% del edificio

[noticed, 80% of the building]

02:09 se exilió por voluntad propia.

[left on their own.]

02:10 (Sound cuts out so no transcript)

02:19 Las personas que decidieron tomar esta vía

[The people that decided to take this route]

02:23 y llegar hasta esta puerta de emergencia

[and got to this emergency door]

02:25 que estamos mostrando ahora,

[that we are showing now,]

02:27 son las que pudieron salvarse,

[are those that were able to save themselves.]

02:31 son las que pudieron ser rescatadas.

[are those that were able to be rescued.]

02:41 Si estuvieramos en el edificio que (se) colapsó,

[If we were in the building that collapsed,]

02:42 esta sería la primera parte que (se) colapsó,

[this would be the first part that collapsed.]

02:44 (Sound begins again.)

02:45 porque es la (parte) de la plataforma de la piscina

[because it is the part of the pool deck]

02:47 y abajo de la piscina está, los, los gara...

[and beneath the pool are, the, the gara...]

02:49 el, el, ...

[the, the]

02:52 lo que sería el sector de estacionamiento.

[what would be the parking area.]

02:54 (Music)

[]

02:56 ¿A cuánto estamos Alan aquí?

[How far away are we here, Alan?]

02:58 A una cuadra. (can't understand)

[One block away]

02:59 Un bloque digamos: 160 metros

[A block let's say: 160 meters]

03:02 aproximadamente.

[approximately.]

03:05 (Music)

03:07 En el edificio colapsado es todo esto es

[In the collapsed building all this is]

03:10 lo que falta.

[what is missing.]

03:11 [Música]

03:19 La gente que se salvó, pudo haberse encontrado

[The people that save themselves, could have been]

03:23 más de aquel lado.

[more towards that side.]

03:25 Acá arriba está la pileta está la pileta.

[Up above here is the hot tub(?).]

03:28 Y acá dicen que también perdía mucha agua.

[And here they say that it also would leak a lot.]

03:30 Pero este edificio parecería estar

[But this building would seem to be]

03:31 mejor mantenido de lo que

[better maintained that what]

03:33 mostraron en el otro edificio.

[what was shown of the other building.]

03:35 La verdad, pero bueno, es similar.

[The truth, for what it's worth, it's similar.]

 

[warrenslo]

I wouldn’t assume that any detail of the north building is identical, nor that one is an improvement over the other.

My sense, though, is that the north building plans are actually older, and they were expanded for the south building based on additional lot area.

I say this because in my lay opinion:

1. The shear walls are reasonable for the north tower but arguably insufficient for the long east wing of the south tower.
2. The aesthetics of the north tower balconies are better than the south tower’s, on the inside corner.
3. Subsequent engineering projects are usually focused on maximizing value, not improving aesthetics beyond the original. See: DC-9 and every Boeing that was ever stretched after the initial release. See also: the Great Pyramid. See also: One and Two Liberty Place in Philadelphia. In almost all cases, the later structure is an uglier, more economized version of the original.

Yes, the north building is only different near the assumed point of collapse (x10 unit is studio vs. 2br) and across the hall similar. The north building also didn't have the column dimension error on the x10 unit. Finally, the north building also seems to have been better maintained. Now the south building seems to have been complaining they couldn't access much of their building during the construction of the nearby building to the south. The south building also had roof anchors installed and most likely tested less than 24 hours before collapse. The north building didn't have this issue. Until proven otherwise this is an OSHA code issue and needs to be fixed!

 

[warrenslo]

This forum today was alot of BS so here is today's press conference link:
Link

 

[tmwaits1]

Statement from a previous post...I also think that all buildings constructed should have a repository of all the final construction documents and submittals, along with documents related to post-construction renovation/modification.

Looking through the original plans You can see many red flags but one obvious thing is that the plans are not even close to being “As-Builts”. They are not stamped as such and contain a number of inconsistencies and missing details. Unfortunately this is very typical, even with buildings recently constructed. This is one thing that should change as we go forward. If you do not provide a proper set of as-built plans you will not occupy the building.

 

[warrenslo]

Alan knows it was the roof anchors but cant prove it yet, boom:
Link

 

[warrenslo]

My understanding is that in Florida even when they had vehicle inspection you could sit in your car while they did it.

Yes this is today's OSHA roof anchor testing because there is no standard but it's "always required."

 

[warrenslo]

Statement from a previous post...I also think that all buildings constructed should have a repository of all the final construction documents and submittals, along with documents related to post-construction renovation/modification.

You're a structural engineer? Good luck!

 

[1503-44]

Dold, No worries. Lots of ways to skin a cat and refinery structures are typically very conservatively designed. 4 function calculators were the only thing on the desktop besides dialup phone, pencil, sharpener, eraser and a pad of paper. Punch cards were for the PDP 11 pipe stress runs we did down in the basement.

I was also a bit horrified by the liberal use of what seems to be nothing more than a few #4 bars in many locations. We only used #4 for stirrups and pavement bars. As for punching shear, that was usually handled by concrete thickness alone. We'd use more concrete thickness rather than throw more steel in it.

 

[Cool_Controls]

Alan knows it was the roof anchors but cant prove it yet, boom:

??? He didn't say anything about roof anchors in that interview.

 

[tmwaits1]

this is probably the best simulation I have seen of the collapse sequence. Punching shear failure with the slab area between the pool and the building which induced lateral load on the line of building columns that failed first. This seems to follow both what is seen in the video and with what is seen in the debris pile.

Link

 

[stevenal]

Please help an electrical to understand here. Do I understand the deck, which appears to be no thicker where it meets the columns, is reinforced by 12 X 12 pieces of steel that don't seem to be much bigger than the columns they sit on?

 

[SFCharlie]

...may find the video more interesting with a better translation.

Muchas muchas gracias

alma de piel (soul of skin) seems to be a brand of ice cream or a dance studio. Is this an Idiom?

SF Charlie
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[GPR_Tech]

Any thoughts on the NYT article?
See related DWG's that I could find for the SOUTH [not north] Towers

S.6 Second Floor Framing Plan (Pg.28 of 336) & (Pg.110 of 336)
Typical Notes
#5 at least 25% of all column strip reinf. shall be centered over the column as explained in typ. flat plate det. - see sheet S.11

S.11 Flat plate Sections and Details (Pg.38 of 336) & (Pg. 237 of 336)

S.5 Lobby Level Framing Plan
(Pg.31 of 336) & (Pg. 162 of 336) & (Pg. 210 of 336) & (Pg. 234 of 336)

https://www.nytimes.com/2021/07/03/us/florida-condo-collapse-steel-rebar.html?smid=url-share

https://www.townofsurfsidefl.gov/do...-collins-ave-1979-plans.pdf?sfvrsn=bd2a1194_3