Miami Beach, Champlain Towers South apartment building collapse, Part 13 44

[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


SF Charlie
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[AusG]

It says "Shall" on the Plan ... shall means shall, no?

 

[arbitraria]

"Hilti Ferroscan, GPR, x-ray, chipping or other means" - selective demolition being "other means"?

 

[Demented]

"...requesting approval prior to cutting any bars."


Bars appear to have been cut. Was there approval?

I ask not because I think it contributed to the fall, but because I would really like to hear about someone involved who did a Really Good Job. I like people who do Really Good Jobs. Warms my little heart, it does.


spsalso

Assuming the GPR was run with an engineer on site as is claimed, I think we have a job done well here. More gooder if you prefer.

More holes were to be drilled after these first odd ones. A series of them on nearly all sides of the pool, extending south from core A and east from core B. But those never were done because of the situation where the board required the pool to remain open and in use at all times during season and more samples were going to be taken when the alternate parking was established in the back lot and side of the building on the access road.


Edit:
Probably late on these. Just noticed Surfside dropped more records at the end of August.

https://surfside.one/public-records-search/

Mostly just more interior demolition, marble tile, and hurricane windows/doors.

 

[SFCharlie]

Just noticed Surfside dropped more records at the end of August.

Thanks for the update from reality, and thanks for the update on the archive!


SF Charlie
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[Demented]

Has anyone else who's looked at the permits noticed the handwriting similarities between one engineering firm that did a lot of restoration work and the town permit reviewer?
I do not want to go down that hole but I'm sure someone will. Not that it even matters. Just more conflicts if true that'd still be keeping this a crime scene and the Town out.
I'm gunna shut up now.
It's been bugging me since this morning and please someone squash that thought.

 

[SFCharlie]

Has anyone else who's looked at the permits noticed the handwriting similarities between one engineering firm that did a lot of restoration work and the town permit reviewer?

Is it possible the firm just phoned it in, and the reviewer signed for the engineer? (should have initialed it) Still probably not legal (not binding in court), But if he did the work and then said "Yep, I'm sure I did a good job.” then I'm sure there is some wittier quote than “blind to one’s own mistakes”.
(not enough coffee yet this morning)

 

[ChiefInspectorJ]

https://www.eng-tips.com/viewthread.cfm?qid=317545

I think we are dealing with deflection and shear in the failed beams not cantenary actions.
If the BM A detached from the step beam we could be dealing with shear and maybe a moment applied to the drop beam even though the max M would be at the support still functioning. But even so the drop beams was too small especially behind the planter and was sheared off in some manner.
The smallest step beam I found could have been 12" x 13.5" near column O.
As someone questioned the buildings close together in NYC. That is a Gneiss bedrock a little more solid that a liquefaction situation at CTS. This soil was vibrated continuously for a long period of time according to the residents.
To avoid lawsuits tying up the sale I would suspect this will be suppressed.
We know the mayor is insane saying this collapse was an act of god.
All bets are off.

 

[Nukeman948]

That is a Gneiss bedrock a little more solid that a liquidfaction situation at CTS.

Please feel free to post some solid evidence of that happening here.
Perhaps a research paper describing "continuous seismic loads microscopically cause loss on rebar bond strength" caused by nearby construction or pile driving causing building collapse by liquefaction.

Sounds more like liquidfiction...

 

[Red Corona]

> The unusual pencil-sharpening of the columns is to me a critical feature.

It's certainly atypical for a puncture shear - normally the slab shears and leaves a piece of itself behind, but here it almost looks like it was the column that failed first. And the slab's rebar should have run through the column and made that clean failure impossible, too.

 

[SFCharlie]

it almost looks like it was the column that failed first

Well, the columns, in most cases, are still standing, but if one looks at the fracture of the top of the column, it almost looks like a cold joint. It is not, if one zooms in, one see the barest hint of white aggregate. The planar failure reminds me of the core samples. The failure stretches from rebar to rebar. Spalding?


SF Charlie
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[Vance Wiley]

Charlie - I think you are onto something. Most punching shear failures leave concrete from the slab on top of the columns. The pics of the UK parking structure show that. Four way flat slabs have tension on the bottom face, and therefore probably cracks, over most of their area, due to the positive moments. And they have tension on the top face at the columns, due to the negative moments there. The probable tension zones are reinforced to address/resist the moments, and that means placing reinforcing near the top of the slab over columns.
Compressive stresses in concrete can assist in resisting the entry of water (but not make it impermeable). Tension cracks welcome water.
While the slab over the top of the columns was the high point (unless drainage slopes prevented this) the overlay materials and the low slopes to drain could have created cases where the slabs over the columns were saturated also. The cracking there would have allowed that moisture into the slab and caused the concrete to deteriorate. If that deterioration led to the loss of strength in the concrete the negative moment strength would be reduced.
Now imagine, if you will, the reinforcing passing over the top of the column, and being pulled downward by the anchorage in the slab - and finally reaching the point of being an anchorage to the catenary tension in the reinforcing. The bars pass over the columns and the corners of the column must support the load in bearing - and maybe fail from that unintended force.
So the corners become "rounded", if you will, and demonstrate the effects of spalling..
Just speculation, but maybe it will provide some mental image of a possibility. We can see the results, this is what I think is one possible reason.
Can't wait to see results of concrete strengths from many locations in this (that) structure.
Thanks,

 

[spsalso]

Has anyone else who's looked at the permits noticed the handwriting similarities between one engineering firm that did a lot of restoration work and the town permit reviewer?

From the New York Times, August 25, 2021:

"Records show that the Surfside building department delegated inspections of the towers back to the Champlain Towers builders, who tapped their own engineer to sign off on construction work."


spsalso

 

[spsalso]

The bars pass over the columns and the corners of the column must support the load in bearing - and maybe fail from that unintended force.
So the corners become "rounded", if you will, and demonstrate the effects of spalling..

I am perhaps misreading this, but it sounds like the corners were "rounded" by the bars passing them as the slab descended.

If this were the case, there should have been those bars still connecting each "side" of the slab. They would now be found surrounding the bottom of the columns.


spsalso

 

[Demented]

From the New York Times, August 25, 2021:

"Records show that the Surfside building department delegated inspections of the towers back to the Champlain Towers builders, who tapped their own engineer to sign off on construction work."


spsalso

Unrelated to the original builders, unless an original team of engineers is what disbanded.

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

 

[ChiefInspectorJ]

/

https://www.prosperlaw.com/what-caused-champlain-tower-collapse

https://www.foundationprosfl.com/best-soil-types-for-building-foundations-in-florida/

You see this is the problem in Florida with people like Electrical Engineers ( not you Jeff) doing Structural Engineering. As a Building official I have referred many of theses cases to the board.

 

[Vance Wiley]

The should have been somewhere and that will show whether this was what happened or not. Wonder which pile they are in?

 

[AusG]

1. Those links are infomercials and PR by lawyers, and a communications grad at a geotech company
2. if anything liquefied from pile driving at the next door site, why would it not show up first at the next door site? At CTS the floor pan and column roots are intact. The question stands: what liquified, where and why?
3. The subsurface at CTS is I believe lime sand. This can dissolve and make caverns but has grain-on-grain framework so it doesn't liquefy. You need to show us a liquefiable layer exists and then some evidence that something actually liquefied.

 

[Nukeman948]

https://www.prosperlaw.com/what-caused-champlain-t...

https://www.foundationprosfl.com/best-soil-types-f...

You see this is the problem in Florida with people like Electrical Engineers ( not you Jeff) doing Structural Engineering. As a Building official I have referred many of theses cases to the board.

An opinion piece from a lawyer, and a foundation company describing soil types in Florida are not the solid evidence that supports your claims.

I have never pretended to do structural engineering. I have not presented any claims as to what caused the collapse of CTS. But you, the Internet's Chief Inspector J made a claim that you don't seem to be able to back up with any real evidence or facts.
We have been over the the theory of vibrations from exploding ordnance, jets taking off from MIA, construction next door, and even tar kettles and found all these theories totally lacking in being able to explain all of the events on the timeline or to be of sufficient magnitude to cause this collapse. And most of the discussions were shut down by actual Structural Engineers on this site. You could spend some time reading up on the first 12 pages.

 

[AusG]

This one has both rounded column and dropped slab preserved, at least until they collapsed the remaining part of the building. That visible lower loop of rebar may be a culprit for ripping out the side of the column, but who knows?

 

[Reverse_Bias]

Can't wait to see results of concrete strengths from many locations in this (that) structure.

We know so far that there are aggregates missing in some of the core pictures and the NIST photos of the columns.

The guys who drilled the columns to demolish the western part of the building said the drill went through it way too easily.

Moribito was getting some "curious results" but won't say what.

It's safe to say at least some of the concrete in the building was well below spec. It's just a matter of how much of it and how bad that needs to be determined. It certainly will clear a lot up if it turns out bad enough to be a major contributing factor.