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
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[hochhaul]

I'm surprised nobody else has mentioned the phone conversation that Pablo Rodriguez had with his mother, Elena Blasser, hours before the collapse.

https://www.latimes.com/world-natio...-family-waits-missing-collapsed-florida-condo

"On their last phone call, the day before the tower collapsed, she told him she didn’t sleep well because she was woken up at 3 or 4 a.m. as the building made loud creaking noises."

In a different interview, Pablo said that his mother had told him that the "creaking noise" she heard was so disturbing that she couldn't go back to sleep.

Guess where Elena Blasser lived in the building.

Yes, 1211 (edit: this penthouse is listed as PH-11 and is the x11 apartment layout of the 12th story penthouse floor). The apartment directly below the section of the penthouse suspected of having a roof collapse. What are the odds. A "creaking noise" so loud and disturbing that it woke her up in the middle of the night, less than 24 hours before the building collapsed. A noise that coincided with questionable work by the roofing contractors on the penthouse roof above her.

I think the recovery team is going to find a parapet in the garage, mixed in with debris from the planter it punched its way through. I also wanted to note that the roof scupper in this parapet is also directly above the planter. For 40 years, that roof scupper was inundating the planter and nearby pool deck with water every time there was heavy rainfall. It had actually rained nearly 2.5 inches in the days before the collapse, which is a potential source for all the water pooled on the garage floor.

 

[julootamu]

Js5180 (Computer) commented "I've also noticed that some of the lights appear to go out in synch with the blue flashes going out, but not necessarily the ones directly horizontal to them. Someone mentioned three phases. Are different floors on different phases? Would this mean that appliances like stoves and dryers are 208v, instead of 240v? Would this also mean that every third floor is the same phase, or is that unpredictable?"

Three phase supplies are either provided in 460V or 208V. I'm sure each floor would be the same, as providing different phases on different floors would be impractical and confusing. In this case its apparently 208V. The good thing about 208V is that a connection from of the three wires of the 208V service to the neutral provides 120V single phase service. Two such connections can supply a standard 240V dryer/etc. While the 120V single phase powers lights/etc. There are special commercial appliances available at extra cost that are designed for three phase but I doubt they were required here.

 

[Keith_1]

Even IFF a car took out a column, there is so much redundancy built into a structure that it is a non-event. This structure has has been subjected to multiple instances of high asymmetric pressure loads (hurricanes), and those pressure are way greater than loading a roof with a few tons to support a swing stage, or taking out a single column. I will state with 100% certainty that a single column, beam or any other discreet element will not cause a catastrophic failure like this, in a structure that has been loaded in the manner that this building has.

I have seen many thoughtful comments about codes and regulations, but have not responded because this does not seem like the proper forum for such a discussion. Can we start a new forum dedicated to preventing "engineering disasters", that deals strictly with inspection and repair of existing structures in terms of codes and regulations, so that we can actually help the general lay person?

 

[LionelHutz]

I suspect the camera has a sensitivity setting, as many motion activated cameras do. In the video you can see foliage swaying in the wind within a foot or two of the camera. You would have to have the sensitivity turned down to a minimum to avoid it being constantly triggered by that foliage movement. Thus it probably took the motion of a full building collapse to rouse it.

That's a pretty useless camera if it requires a large portion of a building to move before it records anything.

 

[LionelHutz]

I think it is the point where a floor slab intersected the column. The small rebar which is bent over would have extended into something and that supports the slab idea. There is no paint on the column so it was behind wallboard somewhere if it was a column. It could have been a transfer beam - but I assume that would have been painted but that may not be correct.
It would be good to hold final determinations until the member is identified.

Yes, there is also that piece of bent rebar that could be from the slab. I can see 2 lines outlining what could be the top and bottom surfaces of the slab too. I'm not understanding why a rebar in a column ending in a slab joint would be an issue?

 

[LionelHutz]

Things like the stove and dryer and water heater would be standard 240V commodity pieces. They just heat a little slower on 208V. The dryer motor runs on 120V, so the drying time just gets extended a bit.

 

[emtv]

I for one don't care where any of these parked their cars, but I find that knowing about it is no different than knowing where any of the other residents were as they observed/heard the various events unfold. What's interesting about the thereabouts of the Argentine couple's car can be relevant to the time at which the events unfolded from an observation standpoint. They had to go through the garage entrance and literally got in barely minutes before the whole thing came down. When they did, clearly nothing was standing in their way, which means the deck collapse hadn't happened yet, and they possibly didn't register any visible signs that it was about to. Their location is also interesting in relation to the noise they heard prior to getting into the elevator. They heard something but couldn't recognize what it was, and also didn't see anything happen there and then (either because their line of sight was blocked, say, if they had been standing behind the elevator block, or because nothing "visible" had happened yet - cue what bones206 said about load redistribution noises - but doesn't that imply the deck falling is subsequent to whatever else had already been going on, and if so, what was that exactly?), but by the time they got to the ground floor and came across the other panicky people there, dust had been flying already, and supposedly only then the deck then caved. To be honest it's still unclear to me whether the deck gave in as they were coming up, or while they were in the lobby with the others. But if that timeline is correct, and the caving is secondary to the dust flying around, then what's the source of the dust? (Honest question).

As for the wild theories going around. The two didn't observe anything out of the ordinary. I would imagine that if the car-slammed-into-column theory had any credit (which I doubt, personally), they'd have perhaps noticed plastic, glass, metal, car liquids, tire signs – anything from the car, really – that would deviate from the ordinary, and it would have been right on their path. Or maybe they did notice, but given the magnitude of extraordinary things that happened afterwards, they just didn't recall these specific details in their telling... but again, it'd be a stretch, I could think of at least 5 different things more plausible than that. Secondly, I'd also rule out their own involvement (I think I saw a comment here implying that perhaps they could have been responsible instead), there would have been simply no time for them to hit a column, recollect themselves after the fact, and then carry on like nothing had happened - given they barely made it out as is. Those implying they fled shortly afterwards because they had something to hide, they were there only temporarily and weren't owners in the complex. I'd imagine the first thing I'd do, if I were in a city I'm only temporarily in and a building I had no particular relation with came down on me, would be getting back home asap. I'd also imagine, much like for any of the other survivors, that on top of what was made publicly known, officials have collected their statements privately. What we know and what they know might not necessarily have the same depth.

I've read the mulling on "when it was only structural people discussing it". With all due respect, much of what is being done here, at the time being, is speculation. Literally all of what is being done here is, including combing through "hard facts", i.e. schematics and plans. Witnesses accounts are notoriously unreliable, but pretending that looking at plans, photos and documents on the internet isn't is a bit delusional, too. For all we know, things were omitted from documents ("curious results" in the cores, yeah, thank you very much, I guess?), plans vs. how it was actually built differ, and photos and videos (more so if sub-potato quality) can be deceiving by their own very nature. Without being there and with the limited access we have (thankfully, I'd say), we know no better. If the scope of the exercise was strictly limited to discussing good/bad practices then by all means, I agree that having experts in those specific fields is the bee's knees, but over the span of 5 topics it simply unhinged from that premise and became a let's throw around hypotheses on the cause - including from structural engineers themselves - so the finger pointing now seems a bit uncalled for.

 

[1503-44]

Dont know if it matters to anyone, or not, but if it does, I am 100% certain that Vasquez learned that the parking area had collapsed certainly after leaving the lobby and probably the property. Just by the words he used. If he saw the parking garage, he would had said that he saw it, not "understood" it. He also said that on the way out Gimena ran into a palm tree and got a knot on her head, so that doesn't sound like they were leaving via the parking garage.

And as for not believing that the other guy would leave that complex to check into a hotel, just because the power had been cut to the unit they were going to stay in, I suggest that you have never tried to sleep one single summer night in Miami with no AC, especially if you are used to cooler nights. Totally plausible. Ask for a night's refund the next day.

I also don't think that the camera was necessarily triggered by motion of the falling debris across the street, high up and in relative darkness, but by the seismic event of the first large pieces hitting the ground and swaying the camera, causing it to see relative motion of objects within the well lighted close field of view. I think I see some evidence of that in the ripple patterns in the pool as well. If the wind started the camera swaying, it would be recording all the time.

My guess would be 4000psi concrete in columns made in 1981.

 

[spinspecdrt]

If both of these prove to be true, it gives actual evidence to the falling penthouse balcony theory.

 

[waross]

I once backed into a column in underground parking.
No visible damage to the column and no apparent damage to the car. The car was completely drive-able and you had to know where to look to see what visible damage existed. The plastic bumper cover popped back into shape. There was minor scuffing of a bright strip.
A few years later the car had to pass an extensive safety check and I had some expensive repairs of hidden damage to the rear underside.
Could a car have backed into a column with soft concrete and corroded rebar, seriously damaged the column, and still been drive-able?
I vote yes.

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

 

[spsalso]

Three phase supplies are either provided in 460V or 208V. I'm sure each floor would be the same, as providing different phases on different floors would be impractical and confusing. In this case its apparently 208V. The good thing about 208V is that a connection from of the three wires of the 208V service to the neutral provides 120V single phase service. Two such connections can supply a standard 240V dryer/etc. While the 120V single phase powers lights/etc. There are special commercial appliances available at extra cost that are designed for three phase but I doubt they were required here.

On Floor 2, all three phases were distributed approximately equally, from a 3 phase 600A 208V sub-main breaker on that floor (this is where individual meters were). That is, 1/3 got phase A 208V, 1/3 got phase B 208V, and 1/3 got phase C 208V. Of course, the 120V went along for the ride.

For the remaining floors, the three phase was distributed as single phase over TWO floors, from a single location, in a similar manner. The sub-main was 800A.


spsalso

 

[Spartan5]

As speculation goes, we don’t even know that the CCTV footage was “triggered.” In fact, considering that angle doesn’t offer much from a security standpoint, why would it be?

This is a recording of a recording being played on a monitor. It’s just as likely that that’s where they cued it up to in their haste to make splash with the media.

 

[CE3527]

The building had an Exterior Insulation Finishing System (EIFS) veneer, so cracks on the exterior are not necessarily structural concrete cracks. They may just be cracks in the EIFS. Also, the crack mentioned appears on the street facing (north side) of the structure, which did not collapse first.

 

[emtv]

Crack, or exterior cable being run? If a crack, then this could very well explain why the penthouse does appear to be missing in the start of the collapse.

Collapse sending a shockwave down the columns until it transfers the load to the top of the M11.1 column, causing it to overweight to failure?

Edit: Original link to source where I found the image. Actual source and date unknown.

Pic is from Google Maps, it's actually on the north face of the building and it's most likely a cable. Navigating through the pictures from previous years, it's been there all along (I can't tell in the 2011 picture, but for sure from 2014 onwards).
Otoh if anyone wants to have a look at the joint between the wall enclosing the area accessible from the overhead and the penthouse roof on the actual collapse side, and if it may have been a weak point... I'm not sure anything can actually be inferred from the sorry state of the Google pictures (the only ones I've seen are from 2014/2015) and I'm not structural so it may just be the way it's supposed to be, but hopefully structural guys here can chime in?

 

[CE3527]

Somehow this planter at ground zero of the collapse manages to remain mostly intact and not be covered in debris. I think it corroborates a slower settlement of the pool deck right in front of the initial building collapse area, and speaks to the completely vertical fall of this portion of the building. It fell completely within its footprint while the portion to the east fell towards the southwest.

 

[gonefishing2]

To my Multi-Discipline Eyes, that looks like a bond beam/concrete filled CMU infill from top of a parpet wall as designed on drawings.

 

[gonefishing2]

If columns can punch shear this patio deck, why the hell can't falling parapet or cantilever do punch shear from 13 stories up???

 

[gonefishing2]

 

[1503-44]

Did anybody find the missing parapet in the parking garage?
Maybe we will just have to wait and see where that landed.

 

[gonefishing2]

So did floor 12 cantilever fail first, the second was penthouse cantilever? Would explain the diagonal tear out at stair tower based upon where this complete crack of cantilever and parapet is located.