Miami Beach, Champlain Towers South apartment building collapse, Part 18 30

[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
Miami Beach, Champlain Towers South apartment building collapse, Part 08
Miami Beach, Champlain Towers South apartment building collapse, Part 09
Miami Beach, Champlain Towers South apartment building collapse, Part 10
Miami Beach, Champlain Towers South apartment building collapse, Part 11
Miami Beach, Champlain Towers South apartment building collapse, Part 12
Miami Beach, Champlain Towers South apartment building collapse, Part 13
Miami Beach, Champlain Towers South apartment building collapse, Part 14
Miami Beach, Champlain Towers South apartment building collapse, Part 15
Miami Beach, Champlain Towers South apartment building collapse, Part 16
Miami Beach, Champlain Towers South apartment building collapse, Part 17


SF Charlie
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[IEGeezer]

Please see the following illustration of a building in China that fell over. For illustration purposes, I am going to pretend that the foundation piles are "columns".

It seems logical to me that if the "column" to the left marked by a red X collapsed first and the "column" to the right collapsed some time later that the building would then be subject to an unbalanced moment that would cause it to fall in the direction of the red arrow. Similarly, if the "column" marked with a blue X collapsed first and the left "column" remained intact for a little bit, that the building would fall in the direction of the blue arrow. ONLY if both "columns" collapsed simultaneously (black Xs) would the building fall down into its footprint (black arrow).

Applying this logic to Champlain Towers South, section 2 would fall northwards only if the columns to the north of gridline 9.1 collapsed first. Most likely, columns on gridline 8 collapsed before columns on gridline 9.1. I don’t think that the collapse of gridline 8 and gridline 9.1 was very close in time, because the amount of debris that fell outside of the footprint of section 2 is very large. That means that a very large force was required to cause the section 2 debris to fall that far north.

On the Eastern Engineering page on Champlain Towers, they estimate the dead load on one of the southern perimeter columns to be about 470 kips. They may have missed a slab, since the building added a penthouse, so I propose rounding it up to 500 kips. The perimeter columns only have half of the attribution area that the interior columns have and the “corner” columns only have a quarter, so I use 1000 kips as the dead load for the interior columns and 250 kips for the “corner” columns. Accordingly, I have estimated about 6000 kips for the section 2 columns in gridlines 8 and 9.1 (I am not counting gridline 4) and a very rough guess is that about 70% of that resulting debris fell into section 3. Accordingly, the unbalanced moment must have been very large, which I interpret as the perimeter columns on gridline 9.1 resisting the collapse for significantly longer than the columns on gridline 8.

That brings us to the surprising conclusion that the collapsing pool deck acted upon the Beams A attached to columns KLM9.1 but did not cause the collapse of the building by acting on those columns despite the Beams A significantly reducing the section of columns KLM9.1. Columns KLM9.1 apparently significantly resisted the collapse to the point of causing an unbalanced moment that caused section 2 to fall mostly into section 3.

 

[IEGeezer]

I further theorize that the horizontal displacement of the section 2 debris from where it would have fallen due to gravity alone may indicate which columns on gridline 8 were the first to collapse. I overlayed the debris pile elevations on a Morabito plan of the roof area.

The apex of the horizontal displacement (indicated by the border between the light blue and the green) is roughly halfway between I8 and K8. Thus, if this theory is correct, the collapse of the columns of the building began with I8 and K8 collapsing very closely in time, followed by the columns on gridline 9.1, thus imparting an unbalanced moment that caused most of section 2 to fall into section 3 and causing the latter’s collapse.

This high resolution photograph of the collapsed parking deck shows a ladder that provided access to the elevator machine room. The ladder's position is shown with a red line on the debris field overlay above. The ladder was near gridline 9.1 and ended up near gridline 4, a northward shift of about 44 feet. The ladder is an indicator of just how far north section 2 fell.

 

[jerseyshore]

Honest question because I don't know anything about major collapses like this, but is debris (location, height, etc.) really that useful for failure analysis? Referencing an individual item like a ladder seems like a stretch to me, I mean things fall weird. I could see a general debris plan like you copied above being relevant, but I'm curious to learn how useful it may actually be.

 

[IEGeezer]

Referencing an individual item like a ladder seems like a stretch to me, I mean things fall weird

The ladder is just an indicator. The 4.2 million pounds of debris (4,200 kips) that didn't fall into its footprint is what needs to be explained. It shows how the building fell, which, in turn, can provide a clue as to which columns collapsed first. The main point is that, if KLM9.1 had collapsed first, I think the debris from section 2 would have fallen to the south and NOT to the north.

(If this passes peer review, I am setting up a theory about the pool deck.)

 

[Murph 9000]

IEGeezer, I think you may be missing the influence of the floor slabs on the collapse direction. If KLM 9.1 collapse first, but the slabs hinge down on KLM 8 and/or KLM 4 (the 4 line is the north side of the east-west corridor, and roughly the dividing line between zone 2 and zone 3), that's going to pull the direction of the collapse to the north, isn't it? I.e. the zone 3 structure resists the collapsing elements of zone 2, pulling them towards zone 3. Personally, I think KLM 8 offered only minimal resistance to the progression (after it started at KLM 9.1), but KLM 4 provided a relative strong point due to the shear wall of the eastern stairwell, resulting in the brief pause in the progression at that point.

You can see this type of action in some of CDI's videos, where they blow columns on one side of a structure first, causing it to be pulled towards the other side by the slabs; or where they blow the middle first, pulling both ends in towards it.

 

[zebraso]

If KLM 9.1 collapse first, but the slabs hinge down

As I was reading the theory posited of unbalanced moments in the progression, I kept thinking "hinging". I mean we are thinking about unbalanced moments continuously. The slabs are coming down like a pendulum right? under what conditions other than certain controlled demo are they going to land in their footprint?. I mean there are unbalanced moments there. I am willing to stretch my mind any way to see how KLM9.1 was not directly involved in the progression. If I could see that I would be excited too. I am trying anyway.

 

[SFCharlie]

... summarize what the current thoughts are from the investigation ...

Apparently Not...
The original design did not meet the original code, particularly in the area of the pool deck.
The contractor didn't build the building to the original design, particularly in the area of the pool deck.
The condo owner owned HOA did not maintain the property, particularly in the area of the pool deck.
The condo owner owned HOA did add heavy adornment to the property, particularly in the area of the pool deck.
The building fell down in it's own time, like a pile of sticks, due to the above, particularly in the area of the pool deck.
NIST is still analyzing the towers.
Please forgive my sarcasm, I haven't finish my first cup'a coffee this morning


SF Charlie
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[jerseyshore]

Thanks for the summary. This one is definitely going to be a subject for those webinars for many years.

 

[dik]

another BPS, and I owe you a beer... 100 people dead and no criminal charges.

-----*****-----
So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

 

[Sym P. le]

Do we have any history on the addition of sand and tile? Who thought that would be a good idea etc.?

 

[SFCharlie]

Do we have any history on the addition of sand and tile? Who thought that would be a good idea etc.?

The original or the HOA added pavers?


SF Charlie
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[Sym P. le]

HOA

 

[MaudSTL]

I wouldn’t demonize the HOA.

Remember that it was the owners who wanted the HOA to spend their money that way. The HOA was not some rogue group acting without restraint. They were acting on the wishes of the unit owners. One of the more recent HOA presidents was so horrified at the difficult and failed struggle to get the owners to do structural repairs that she quit, moved out, and sold her unit. The very day the building collapsed, owners were still circulating a petition to reduce the assessment that would have saved the building had the repairs been done in a timely manner. Basically, a large percentage of the owners couldn’t afford to live there or were investors whose only interest was monthly income.

The Big Lesson to me in all of this is never to buy into a condo. Before CTS collapsed, I had been thinking about selling my houses and moving into a condo. Thanks to CTS, I am now renovating both of them, one as a residence and the other as a rental. No condos for me!

 

[hpaircraft]

The original design did not meet the original code, particularly in the area of the pool deck.
The contractor didn't build the building to the original design, particularly in the area of the pool deck.
The condo owner owned HOA did not maintain the property, particularly in the area of the pool deck.
The condo owner owned HOA did add heavy adornment to the property, particularly in the area of the pool deck.
The building fell down in it's own time, like a pile of sticks, due to the above, particularly in the area of the pool

At this point, the question of why the building stood as long as it did is probably more interesting than why it fell down.

 

[Reverse_Bias]

I just watched the failure hypothesis NIST video and starting around 10:15 Kamel says they did find 10 hard drives that might belong to the dvr but not the dvr itself and they are trying to recover data.

 

[jerseyshore]

At this point, the question of why the building stood as long as it did is probably more interesting than why it fell down.

Same reason 99.9999% of buildings don't just fall down under normal service conditions: redundancy of structural elements, they rarely see their design live loads in service, and material/ design "safety factors".

These types of failures are so noteworthy because they are just incredibly rare, even though there are probably a million buildings and structures that are some combo of under-designed/ poorly built/ terribly maintained/ downright shitty. But buildings don't fall down thankfully. Well until they do.

 

[MaudSTL]

The condo owner owned HOA…

Thanks for the edit, SFCharlie.

 

[SFCharlie]

But doesn't the (only, to date) video show the south wall falling straight down?, then the corridor and then the north ridge?
Do I misunderstand you?

SF Charlie
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[Sym P. le]

w.r.t. HOA and sand/paver application on pool deck, I was more concerned about how this plan passed muster with building permits.

 

[IEGeezer]

But doesn't the (only, to date) video show the south wall falling straight down?, then the corridor and then the north ridge?
Do I misunderstand you?

In part 17 on 12 Jun 22 at 17:15, you posted a gif using a slide from NIST, if I understood that correctly. Looking at that gif, it looks like the building is falling away by comparing the parapet of the penthouse with the facade of the eastern portion. You can also look at the machine room above the elevators. The eastern portion twist from right to left, as if section 2 is falling away from the camera. Maybe it's just an artifact, but it is intriguing. The ladder and the debris pile don't show section 2 falling straight down. Look at the blue lines you marked on the gif.

The camera is very far away and at a bad angle, as it would be easier to tell if viewed from the side. It's hard to tell from a distance whether something is falling a little towards you or a little away from you, but the gif you made is intriguing. It's one of the things that got me thinking.