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

 

[CE3527]

I sketched down some of my thoughts on the pool deck collapse, trying to tie together what is known. More questions than answers. Seems that there are at least one too many variables right now, which cannot be answered without further video, eyewitness testimony, or forensic evidence. There should be more information once they get to the bottom of the debris pile. One thing is certain when they remove the debris, they should be able to quickly rule out/in a sinkhole below the actual building foundations. Either the pile caps below the garage slab are still there or they aren't.

 

[Js5180]

JBourne,

I wouldn’t expect to see columns laying intact or even in pieces on the ground. They have rebar at both ends. That isn’t really a likely failure mode for RC columns. If this was a stone church, then yes.

The missing column is curious, but there are many possible explanations for it. First, it could be hidden by all sorts of non-reflective debris, like topsoil or plants. Second, it could be hidden by a hinged piece of slab. The picture is simply too grainy.

And remember - to the extent that I’m suggesting a roof event, I am not suggesting it as a trigger. I am only stating that the absence of the K/L/M roof slab, the in-plane appearance of the floors, and the lights being on all work against the theory that the M column descended first. The answer to that doesn’t lie in the basement pictures but in surveillance video and the roof framing plan.

 

[arbitraria]

Hello all, I've seen it mentioned over and over that no alarms were sounded until the building was in active collapse. However, it was reported very early on that there was in fact an alarm that sounded prior to the collapse, and this is why emergency crews were already en route when the final collapse occurred. Whether this was an automated alert or someone pulled an alarm box, I don't know (anyone familiar with Jefferson alarm services?)

I know I saw this reported on multiple platforms in the first couple of days afterwards, but it wasn't repeated much as more information came out, I had to go looking go find it.

https://www.washingtonpost.com/nation/2021/06/24/video-timeline-miami-building-collapse/

 

[Demented]

Has it been 100% confirmed the column is missing in the tiktok video? Just because we don't see it, doesn't mean it's not hidden behind a fallen, hinged section of the upper deck, prior to the failure of the structure.

Seriously, is it not possible that the already weakened structure simply failed due to the additional weight of inches of water over the pool deck? It doesn't have to be some freak accident. Would lend to the deck simply falling down, and hinging on columns attached to the building before ultimate failure. Weather data for the area does confirm at least, at the very least, 2" of rain in the days leading up to the collapse. Assuming a lot of it did drain away, and only half an inch is left on the failed waterproofing of the collapsed section. Basing some rough dimensions off of the pool furniture, lets say that's a 63'x49' area.

96,000lbs of water just sitting there, on a weak structure. I do believe between the hours of 9PM and 12PM leading up to the collapse, gusts of wind 30-45 mph were recorded.

I don't really know what damaged, poorly draining, overloaded flat top structure can handle tons of weight constantly collecting on it day in and day out.

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

 

[mb3928]

If the garage had a deluge system, a broken water pipe may not trigger an alarm.
Some deluge systems use open sprinkler heads and a second dry, air pressurized pilot system.
If a head on the pilot system operates, the dropping air pressure allows a water valve to open and supply water to all of the wet sprinkler heads.
Deluge systems are often used for vehicular areas. A typical system only supplies water to the head that has overheated. A deluge system supplies water to a zone including the area of the head that triggered the flow.

My point is that 1) the 1979 FA riser doesn't show a waterflow alarm of any kind in the garage, 2) there is evidence of significant damage in the garage before the collapse, and 3) there are no reports of a fire alarm going off until during/after the collapse. That's not ironclad, but taken together, those facts are one more piece of evidence lending credence to the initiating event happening in the garage/pool deck area, not anywhere else.

 

[jbourne8]

Js5180, there just isn't enough debris to completely hide the column. Do you have any ideas on what else that white object could be? I find it curious that some people think they can see rolls of roofing paper in this photo, but not a column. I just don't see how anything falling from the roof could detach a column from it's rebar at the base, and throw it too far away from that spot to be identifiable. Also, I think it's really obvious which column descended first from the ring video.

arbitraria, I heard they were already in the area, and Gabe Nir was the one that called 911 at 1:19 to alert them. The only reports of the fire drill going off seem to be after the collapse. Maybe the security guard pulled it, but it didn't sound across the entire building because of a short in the basement or something?

Demented, If you watch the 2020 tour video.. that's exactly where it was. They were all an equal distance apart and are the same size there. It's definitely missing. We also can't entirely see column 28 even though we know it stayed standing, which hints that the object above it is the pool deck and it hasn't completely collapsed down to the floor there.

 

[Js5180]

Microwizard,

I am confident Josh will address the error, but wire and conduit don’t stretch. The vertical feed was a fairly critical part of his analysis. His theory needs to be refactored. He may end up at the same place but you can’t just skip over that part.

As for how a roof collapse would take place, I believe that at some time before the first frame, the penthouse roof collapsed, hinging at the column M line. This could have happened as late as the second before the video starts, but it’s very difficult to prove that it didn’t happen at some point in time. The penthouse roof slab has clearly separated at the M line. Did it shear off and drop straight down? Did it hinge?

Had that event happened independently of the main collapse, the parapet wall was definitely a weak link and it would provide enough energy to damage the pool deck in the manner we see and then weaken the beam between 10 and 11.1. In fact, if there had simply been a strong enough vibration nearby, I’d expect the parapet to be the first major piece to fall, owing to its position way out on the cantilever.

 

[JStructsteel]

The roof
Anchors don’t seem to be installed very good.

 

[JStructsteel]

What was the plaza
Designed for? A lot of sand on top of it.

 

[JR97]

I am not backing or discounting any theory. But, if a car /truck hit the column with enough force to completely detach it from the floor, wouldn't it have followed the column? In other words, why isn't there what is left of the vehicle resting against the thrown column? I keep getting drawn back to the unknown cylindrical object where the column should be. But my mind can't make it look like a car part. I must be missing something.

JR97.

 

[spsalso]

What I found interesting in the above photo:

Yes, the two heavy rebars meet at the joint. Perhaps it is acceptable practice to do this for one of four bars passing through vertically? Concrete guys, of which I am not, would know.

But also:

It was posted on June 30. That means that some or all of the parts of the building were being relatively carefully kept off site, for evaluation. As you would expect, but ya never know....

Also, of course was the amount of rebar going horizontally (formerly) through the joint. I can see only one piece coming out of the (now) top, with no places evident where it had been snapped off cleanly. This then looks like one piece of bar where there should have been six. The facing side seems to be similar. Again, perhaps the location of this particular joint only demanded a small amount of rebar. Concrete guys?

So far, this is the ONLY photograph that I've seen with good definition and up close to the subject.


spsalso

 

[Murph 9000]

The lights can possibly stay on with M9.1 being the effective origin of the building collapse if the slabs remain continuous and just hinged / folded across to the elevator shear wall. I'm not certain, but I think the power runs from the north end of the shear wall, in conduits embedded in the slabs, and we just need them to stay attached for the first few frames of video. It seems conceivable you could maybe get a floor or two of drop in the x11 bays, with the x10 bays gradually hinging down before detaching. If there's something like a 60–100 amp supply to a panel in the apartment, those heavy cables would require a good bit of force before finally breaking.

 

[gonefishing2]

https://res.cloudinary.com/engineering-com/image/upload/v1626026145/tips/Untitled_drawing_c-1_cad4db.jpg

What I see with the cue, is I see top portion of column 28 upside down, standing on j-Hook rebars near corners.

Anybody else?

 

[jbourne8]

Thermopile, 28 is the one that puncture sheered and was still standing. The missing column is the one between 27 and 28.

 

[Demented]

I do understand that is where it should be. My point is it's too grainy of a video and there's no actual distinguishable items other than possibly a planter, and rubble that appears to be pavers or CMU. It is possible it his hidden on the other side of the decking that collapsed. There is very obviously debris behind the column location, closest to the garage ramp. If the decking collapsed and hinged behind that column, especially with little light and shaky grainy video, we very much likely wouldn't be seeing it at all.

If this 5 seconds of zoom in is the only proof currently of that column being missing, I think we need to all take the missing column theory with a grain of salt.

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

 

[gonefishing2]

Sorry quoted wrong column number, but I still see top of column siting on rebar cage from where beam interfaced into it

update: Definitely gate bars are giving me an illusion of the vertical column corners, so not sure anymore what I see

 

[julootamu]

Probably 200A electric service per condo or more if they have tankless water heaters. My Steibel 21kW tankless has two 50A breakers for total of 100A. For a large family you need a 36kW 180A tankless meaning electric panel over 200A. Or they could have natural gas either per unit or central.

 

[Demented]

If you squiint really really really hard at the tiktok video, lights and shadows might make some sense.

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

 

[Js5180]

Murph,

I would agree - if there was hinging that didn’t break the floor completely off, the power still reaches the unit. The other possibility is that there is much more hinging along maybe the 8 columns than we realize. In other words, the corridor was intact, the southern side of the units hinged downward, but there was still a connection.

The wire to the unit panels is unlikely to be cable and more likely to be conduit with 2-3 wires in it. I don’t believe, from the pictures, that the conduit was embedded. The corridors had drop ceilings, and the conduit comes through the shear wall just below the slab, according to the pictures.

I’d be curious to see a diagram that keeps the conduit intact for a few seconds.

 

[gonefishing2]

jbourne8, thanks for the updated link