Miami Beach, Champlain Towers South apartment building collapse, Part 08 20

[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
Miami Beach, Champlain Towers South apartment building collapse, Part 06
Miami Beach, Champlain Towers South apartment building collapse, Part 07

SF Charlie
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[Colostruct]

Demented

2” of flooring would weigh somewhere around 30 PSF maximum. That’s a thick floor heavy floor and would be conservative. That adds up to a load of 12k per floor(but that is unlikely). MAYBE we could say it was 75 k total increase. On a 16” column that’s 300 PSI increase.

IMO, UNLESS we had really really bad concrete in several columns, I find it hard to believe that the initial failure was a column.

BUT, if a slab were to fail, the height of that column now doubles and there might well be a hinge at the location where the slab was. Now, consider that maybe 5 columns had this go on, we have a major instability potential in the building. Even more so would be a failed transfer beam which might be able to rip that hinge apart.

 

[Demented]

How would it affect it if columns had been incorrectly repaired and the large sections of replaced concrete and mortar had become mechanically dethatched from the parent column, but only held in place because 3"-4" of rebar305 stainless rods extended in places holding it? Plus the heavy rains from the day before with a deck and roof that floods? There seems to be more trouble finding good concrete than finding bad.

Bring something to 80% it's load rating enough times...

 

[zebraso]

I'm putting my inconel hat on for this one.

Mine is mu metal. Occam's razor has nothing on it. I'll take it off when Kilsheimer mentions Occam. To me that is what you say when you have no data or theories left to pursue and still have no answer. It's actually a logical fallacy to say the most likely explanation can invalidate the rationale of pursuing evidence. I mean that's how you can be assured to have the wrong suspect.

 

[MechinNC]

Elevator motors were on top of the building while standing. Do a controlled demolition and where do you expect them to end up?

 

[Murph 9000]

Demented, that red beam is haunting, because we know once the east end of it lost it's footing, that huge unit took a long bite out of
the #4 units, pulling down everything in it's path.

That's an unlikely sequence. Columns E2 and E4 (west side of HVAC beams) survived to the very end, actually defiantly poking out of the top of the controlled demolition as the building fell below them. Columns H2 and H4 (east side of HVAC beams) fell as part of the collapse (the second phase of the tower collapse, delayed maybe half a second by the row 4 columns and eastern shear wall). The 04 units would have been collapsing ahead of or simultaneous to those columns, with the HVAC unit following the columns. The HVAC unit won't have helped, but it shouldn't have really done much more than ridden the collapse of the 04 units down.

 

[Auri]

Has to be from the collapse. Why would the passenger side curtains deploy with no obvious crumpling of the areas

It's just dust, same on hood & side panels. Airbags aren't supposed to deploy on parked cars - no electrical power to the triggers. Though there are explosives within airbags, the plaza collapse air boom would hardly register, wouldn't even crack the windshield.

 

[Demented]

I was thinking more from the jolting. I've had airbags deploy in Honda's/Acuras before, while no key in ignition. Don't install the G sensor upside down and then plug the main fuse back in.
Hondas and airbags don't mix.

https://www.wtvr.com/2012/06/07/airbags-deploy-while-car-parked-babies-inside

Hmmm.

*shakes head*

 

[TugboatEng]

I've had airbags deploy in Honda's/Acuras before,

Plural? What profession are you in that gives you this much exposure to surprise airbag deployments?

 

[Demented]

Honda certified tech while in college.
My father was also a master Honda tech for damn near 40 years so I've learned a few things along the way from a master tech cursing the engineer who designed what ever he's having to fix. A civic in the 90's decided to put him in the hospital after airbags deployed during a factory retrofit of A/C. Battery was not in the vehicle.

Hell, we used to have airbag detonation days scheduled. Warn everyone but the shop manager and then call him out to the shop.

 

[Murph 9000]

Demented, the HVAC beam in the collapse may not be the one in the permit drawings. The cover letter says that the steel was temporary shoring for the HVAC plant, to allow replacement (implied to be substantially like for like) of the original RC beams. At some point, the new permanent beams changed from RC to the steel we see in recent aerial photos and in the heap. At some point between temporary and permanent, it's not unreasonable to suspect the design may have evolved.

 

[Demented]

The 2018 inspection shows a photo that indicates the temporary beam is still located on the roof. A section of the bolted and welded area is photographed.

It was designed in such a way that it could be easily carried up the stairs, or service elevator, in sections. Once in place on the roof, it could be assembled (cut and predrilled in the fab shop) and then final welded with a generator/welder combo or a small transformer and access to a 30A breaker. Once welded, would require torch cutting most likely or hoisting down via crane for removal.

 

[gonefishing2]

Demented, What I see in picture is not a beam assembly, but rather a length of monolithic beam..... And it is on top of Cooling Tower, not under it...

And I see no permanent concrete beam...... in picture

 

[Demented]

@Thermo
Same. I'm just not counting out lost pixles because potato camera.
I see the beams on top too, but all the beams are on top. It did a barrel roll off the building, kinda like a portion of it was on the still standing section.

The two primer colored beams welded to a red painted beam, in the location of the new unit. Eh. Maybe, maybe not.

 

[gonefishing2]

Agree, so concrete was never used on roof beam replacement, and they were messing with cooling tower beams during roof work and anchor work?

Or rather they were replacing crappy concrete beam replacement with steel? Duh.....

 

[Demented]

I feel this needs a repost.

The building changed its HVAC equipment sometime after 2019. This equipment was on a red steel platform with corners sitting on concrete columns clearly visible in aerials. The equipment flipped over the platform as it fell down the building, this tells me it didn't ride down the building but may have been the reason of the collapse - falling first. The new equipment was on sitting the portion of the building that is still standing yet fell. There also is a large gash in the remaining portion of the building under where the equipment sat.

Furthermore, initial reports confused 135 and 136 units, it appears at some point the "Penthouse A" was added (possibly during construction) as the flyer from 1980 for the building only states 135 units and 12 floors. The penthouse is the 13th floor and 136th unit - it was recently sold and the listing noted marble floors. The penthouse and HVAC unit appear to share a column at the SE corner of the HVAC platform that seems to be the source of the collapse.

I wonder if they placed any additional equipment on or near the HVAC platform prior to collapse and if the building was structurally designed for the penthouse. It is also possible the platform itself failed if it was not designed for the new equipment - it does not look like they replaced or strengthened the platform when the new equipment was installed. To me, this does not look like a sinkhole but a progressive collapse from the roof for the first portion that collapsed as it did not tip over, followed by a failure of a low level (possibly garage) column due to debris causing the second collapse where the remaining building essentially tipped over on top of the first collapse.

Note: I have not been able to access assessor or permit info for this building on the town or county websites, it seems to be blocked - which is pretty unusual.

-W

2019 aerial (old equipment):

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

 

[Optical98]

I'm no expert on elevators but the only picture I've seen the lift motor room looked to me like the basement, plus I thought the elevator car went all the way up to the PH... some plans showed a secondary lift too, not sure if that took place either.

 

[gonefishing2]

Demented, I could also argue that the barrel roll was caused by loss of East side support when that part of building collapsed. The collapse perhaps pulled the steel beam down on east end, thus caused the barrel roll of the west equipment???

 

[gonefishing2]

Optical98, they extended elevator shaft up with the Penthouse addition. It is a pain to look thru Surfside's out of order drawings on a laptop. What is really needed is to print out documents on large scale printer and then sort in correct order. Elevator room looks normal to me....

 

[Demented]

@Optical98

@Thermo, sounds likely. Seems like at least some of the column was still attached to the support structure.

The beam modifications are still interesting.

Original

https://static.timesofisrael.com/

http://www/uploads/2021/06/AP21175469684808-1-e1624543703118.jpg

 

[spsalso]

On the plans, there are numerous references to an elevator machine room on the roof.


spsalso