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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[jbourne8]

Probably my last post on this too Thermopile, I'm pretty satisfied with Teguci's theory.

Here's a rough drawing of what I think the slab on the ground in the tiktok video looked like exactly, and where it was before the collapse if it fell straight down. It all seems to line up too well with what he suggested. I guess this means that missing column must be hiding from view under the planter.. makes the most sense really. I left out all of the areas that are outside of the camera view too.

 

[Js5180]

Softee - thanks, very helpful. Can you link to that? I think I have the reno plans but not that one.

I notice the closets are on 2-5-8-11, while the riser diagram shows 2-3-5-7-9-11, and I don’t see anything covering the PH. Not sure why they would be different.

Do you see anything that indicates different phases?

 

[zebraso]

I give up, I am out. I can not keep facts straight when looking at pictures....

You're just overloaded right now. To be expected. Take a well deserved deep breath and come back with a fresh perspective. Everyone's been there.

 

[bones206]

Teguci - I believe that slab drop is 1'-11", not 11". It is incorrectly noted as 11" on the Morabito report plans, but the plaza and entry slab elevations are noted on the original plans as 10'-10" and 12'-9", respectfully.

Regardless of that discrepancy, I think your hypothesis pretty much aligns with what I was thinking yesterday:

The angle of the planters (what I believe are the planters) leads me to conclude the slab failed around the 1'-11" elevation drop at the edge of the long planter. The slab would have hinged along grid 11.1 and dropped to the shape of a ramp. That would explain why some of the planters look high up in the photo. Then maybe column M11.1 buckled and fell to the right after the initial slab collapse.

The thing that's nagging in my mind is the column on the left (M10) is supporting the building and the column on the right (M11.1) is only supporting plaza slab. But since they are connection by a beam, if the column on the right (M11.1) collapsed for some reason, the falling slab would cause the beam to rotate clockwise and put a huge bending moment on the left column (M10). That's a plausible trigger for the subsequent building collapse.

However, my thinking evolved after it came to light that the surface level parking area along Collins Ave may have collapsed virtually at the same time as the planter area around column M11.1:

If that account is true, it would indicate a larger area of initial collapse of the plaza slab, to include the area where cars are parked. As opposed to a more localized collapse in the vicinity of the planters/column M11.1.

So if we accept the timing of the surface parking collapse and we take into account the many punching shear failures that were the first thing everyone noticed when the dust settled, do you agree with the logic that the initial plaza slab collapse was more likely a much more widespread event? I believe that the failure of the planter area and beams connected to M10 eventually triggered the building collapse, but I'm not so sure anymore that the plaza slab failure started there. It seems to me more likely that it was a widespread progressive collapse of the entire plaza slab, that may have slowly accelerated over several hours based on the timing of witness accounts of creaking/cracking noises. Putting the timing of the tik tok video together with the timing of the Vazquez/Accardi elevator ride, it would appear the planter area and surface parking area collapsed about at the same time. Since those two areas are on opposing sides of the lobby, it follows that the plaza slab collapse was widespread and wrapped around the building. This is consistent with the aerial images that show the slab sheared around the perimeter of the basement. Initially it was hard to say whether this was a precursor or a symptom of the building crashing down onto the slab, but I'm leaning towards the precursor theory.

Does this logic make sense?

 

[waross]

For larger services, three phase is more economical than single phase.
I don't know the current break point but guess around 400 Amps plus for the service to go three phase.
The breakers are installed onto bus bar extensions.
From top to bottom in a panel the bus bar extension phasing is:
A phase.
B Phase.
C Phase.
A phase.
B Phase.
C Phase.
A phase.
B Phase.
C Phase.
repeat.
The top breakers are A + B phase.
The next breakers are C + A phase.
The next breaker spots are B + C phase.
In Canada AC90 is often used for feeders to apartments. Armoured Cable, 90 degrees Celsius rated.
The labour cost is often the lowest.
480/277 Volts for large motors? Again an economic concern.
First choice is all 120/208 Volts.
If the addition of the large motor loads in the design phase requires a larger transformer, then the option of a larger transformer may be compared with the option of a second 480/277 volt transformer.
Another factor may be the use of motors above 200 HP.
A rule of thumb says that it is desirable that the motor HP not exceed the voltage.
The rule may be broken on both economic grounds and on voltage dip when a large motor starts.
It depends.
Most designers will run one 250 HP motor on a large 120/208 Volt service.
A 400 HP chiller motor will have serious consideration of a higher voltage.
Four wire, 120/240 Volt delta? Forget it. Too many problems for large single phase loads.
Such as: the transformer bank capacity is reduced by 1/3.
For a given single phase 100 KVA load:
One phase will have 50 KVA at unity power factor.
One phase will have 50 KVA at 50% lagging power factor.
One phase will have 50 KVA at 50% leading power factor.
Wait! That's a total of 150 KVA for a 100 KVA load.
That is correct.
I told you that the four wire delta connection was problematic for large single phase loads.


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

 

[Demented]

Teguci's post about the design/deterioration really explains every single video and fact perfectly. It seems like the slab he's describing is the one you can see laying on the garage floor in that tiktok video too. The north building also doesn't seem to have this same design flaw even though they were supposedly built with the same plans. You can see this section of their garage at 3:31 in this video -

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

He never looks at M10.1, but on the left you can see M11.1, and M12.1 at the center of the screen. There is no beam connecting M10.1 to M11.1 in their garage, and no step in between them. Instead the step seems to be sitting on M10.1. Or perhaps there's a soffit or a drop ceiling covering it there? If not, it does make you wonder if they noticed the flaw in between the two buildings and then tried to fix it on the north one.

I think the curious thing MC noted was that the building slab actually did have a slope to it when he tested it in 2020, but in 2018 that was his best guess for why it was so deteriorated within the garage. It's brought up a bit in those board meeting notes in 2020, and it says that he was going to need to test the slope further. It makes sense that the design problem was actually much more complicated than that.

If I am not mistaken, the slope of the deck was such that water accumulated in that particular area. Not the entire pool deck draining towards it, but a substantial bit of the pool deck that was not flowing towards a drain and getting under the waterproofing through faults. This section, located under pavers and planters, directly ahead of the main entrance ramp, was in need of complete removal and replacement. There were also signs of failed epoxy repairs of cracks of the entire slab at that exact location.

Page 9 of the original structural report lays it all out for us.

Florida rainy season just started. 2.88" of rain in an area in 3 days collecting on a 0 years left slab. Unfortunate. Some simple shoring probably could have prevented this, but alas, that would have blocked the parking entrance and they needed the towns permission for off-site parking.





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

 

[Demented]

*shrugs*

It doesn't take a rocket surgeon to put 2 and 2 together, or does it?

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

 

[JAKLED]

Is it just me or does it look like a roof anchor crashed through the wall in this picture?

 

[Spartan5]

It seems like someone desperately wants to get this roof anchor narrative to take hold. It’s the flavor the of the week for those who have just joined in the last few days or so.

 

[Electronbelt]

Does anybody know the timestamp in the re-occurring tiktok screenshot that appears to show a round object on the ground just below and to the right of the "C" on the vehicle gate? (aka the 'table'/'fan/'hvac unit'/'truck'/'portal to another dimension'. I have not been able to produce a similar view and I am wondering if it may in fact be a chance compression artifact.

For what is is worth to anybody, these are the images I have been referencing/processing during my reading:

Entryway Frame 259 Raw:

Entryway Frame 259 Deep:

Entryway Frame 274 Raw:

Entryway Frame 274 Deep:

Entryway Frame 291 Raw:

Entryway Frame 291 Deep:

and maybe I'm blind, but I'm not seeing anything that might resemble objects "from the roof". Rolls of tar paper etc...


EDIT: "hi-res" links:
1: Entryway Frame 259 Raw
2: Entryway Frame 259 Deep
3: Entryway Frame 274 Raw
4: Entryway Frame 274 Deep
5: Entryway Frame 291 Raw
6: Entryway Frame 291 Deep


Thanks.

 

[NOLAscience]

If you drive right past a fresh pile of broken concrete in your garage, and then the building falls down, you might think to bring it up.

You might even decide to gather your valuables and go sleep in a hotel...

 

[Roga50]

New article on the analysis going on at the North tower.
Link


Notice how specific they were about the concrete drilling and refilling... Wonder why they are being so detailed specifically on this in the article?

“We have scanned parts of the slab and some columns to locate reinforcing steel,” Kilsheimer said. “And then we have dripped some concrete core samples in the slabs, avoiding the reinforcing steel where we could. The holes will all be cleaned out and filled in with 8,000 PSI concrete before we leave today.”

 

[dik]

Small world... a note from the STI... I'd signed up for a webinar on yield line analysis... but, now postponed.

"STI’s technical consultant and presenter of the webinar, Mustafa Mahamid, PhD, PE, is currently on site at the Champlain Towers South building collapse in Florida. He is assisting in the evaluation and recovery efforts there, and this effort will take him beyond July 14th. Our hearts go out to all those who lost their lives or loved ones in this disaster and to all the volunteers who are continuing to work in difficult conditions.

We appreciate your patience as we work to find a new date for the webinar. You will be notified as soon as possible of the rescheduled date. If the new date does not work for your schedule, we will offer a refund. If you have questions, please email us at hssinfo@steeltubeinstitute.org."

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

 

[dik]

I think your deleted post was right on the mark... sorry for snooping.

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

 

[miningman]

ah ah , finally a documented attempt to examine the sub surface geology . If theres anything untoward down there , all the structural theorizing goes outta the window

 

[Js5180]

Electronbelt - that just means the HVAC unit got run over by a car backing away from a column. Ha!

 

[NOLAscience]

Even IFF a car took out a column, there is so much redundancy built into a structure that it is a non-event.

How long will the garage ceiling or visitor parking deck stay in place after a column is removed, by a car or other event? Please provide your answer in 'seconds'.

 

[Demented]

ah ah , finally a documented attempt to examine the sub surface geology . If theres anything untoward down there , all the structural theorizing goes outta the window

Link?
Edit: nvm. I see it now.

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

 

[dik]

Until there is more information... I would lean away from the vehicle and the HVAC impact... even if the iniator... there's something much worse in play... even with the Twin Towers... the impact was a tad greater... was the fire and the damage to the fireproofing that did them in.

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

 

[Nukeman948]

The top breakers are A + B phase.
The next breakers are C + A phase.
The next breaker spots are B + A phase.

Excellent information is this post even though we learned this building was only 208/120, however the third breaker in your example would be B + C phase, then it repeats.