Miami Beach, Champlain Towers South apartment building collapse, Part 16 24

[dik]

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

-Dik

 

[bones206]

The monolithic joint shown in that typical retaining wall detail is not a viable detail. Walls and slabs are never placed in a monolithic pour like that. Most likely the contractor would have flagged this in an RFI and asked the engineer to provide a construction joint at this location. Either a vertical CJ at the face of the wall, or a horizontal CJ at the soffit of the slab. The rebar detailing shown is also quite bad.

 

[Keith_1]

It is a retaining wall with sheet piles it is not structura. Damn non of you have actually designed or built anything.

 

[bones206]

Not structural? Please explain.

 

[SwinnyGG]

The monolithic joint shown in that typical retaining wall detail is not a viable detail. Walls and slabs are never placed in a monolithic pour like that.

Have to disagree... slabs are poured with monolithic thickened edges, depressed beams, and stem walls all the time. It wouldn't necessarily be my first choice to do it that way, but it can be done without much drama.

Not structural? Please explain.

Don't feed the troll. We've been down this road before with this guy.

 

[bones206]

Already regretting I dipped my toes back into this pool.

I agree that certain vertical elements can be placed monolithically with slabs (like thickened edges, etc.), but I would find it very unusual for a basement-type wall to be placed monolithically with an elevated slab.

 

[Sym P. le]

It is a retaining wall with sheet piles it is not structura. Damn non of you have actually designed or built anything

These 15 or so threads have been unbearable at most times, nor am I an expert designer, rather a curious one parsing through the crumbs that are out there for us to feed on.

The point I was trying to raise was whether it was constructive to model a vertical shear fracture of the slab at the interior face of the perimeter wall for analysis purposes or how such a structural defect would evolve.

From a structural design standpoint, does the slab diaphragm not offer lateral support to the tower structure and as such require adequate connection to the perimeter vertical elements?

 

[SwinnyGG]

See my post from 25 Jan 22 07:10 in part 15 for the full drawing sheet which shows the pile layout, as well as the perimeter retaining wall cross section which gives insight into how the pool deck level slab transferred load through the retaining wall and down into the outermost ring of piles below the basement level slab.

I don't think as a group we know for sure that the pool-deck-level slab was a critical structural element from the standpoint of maintaining stability of the building itself, because no one has done the big heap of math needed to figure that out... but based on the pile layout and the detailing at the joint between the perimeter retaining wall and the slab, it appears that one of the following is true:

1) the pool deck level slab was a critical element for maintaining lateral stability, and its failure put the foundation system into an unstable condition (in other words, sawcut out the pool deck slab and the building is now unstable)

2) the pool deck level slab itself was not critical for maintaining stability of the foundation system, BUT the failure of the pool deck put unaccounted for horizontal load into the foundation system through catenary action as the slab came down, and those horizontal loads caused localized failure(s) at the joint between the exterior pool deck level and the perimeter of the actual building, and those horizontal loads and localized failures put the building into an unstable condition (in other words, if you sawcut out the pool deck slab the building is stable, unless you then put some big horizontal loads into the top of the basement columns)

 

[bones206]

The point I was trying to raise was whether it was constructive to model a vertical shear fracture of the slab at the interior face of the perimeter wall for analysis purposes or how such a structural defect would evolve.

Yes, I understood your point. In my reply, I was trying to explain how that joint may have been constructed with a cold joint at that location. This isn't necessarily a defect, as cold joints (aka construction joints) with rebar dowels are commonly used in construction. If there were a construction joint at this location, it should be readily determined from an examination of the joint. I remember when the event first occurred, photos (although taken from a distance) seemed to show a clean vertical break at this joint in some locations. It could very well have been a vertical construction joint with steel dowels taking the gravity load.

The ground level slab may have been considered as a brace point for the building columns, but I would expect the columns could still survive if the slab was hypothetically removed from the analysis. But failure of the slab I agree could impose some lateral loading on the columns, which could initiate a collapse. I tend to believe the slab collapse progressed from the property line until it took out that one slender column near the planters, causing one end of a beam to drop and wrench down on one of the main building columns.

I haven't been following closely for a long time and have just been waiting for the investigative report to be published.

 

[MaudSTL]

Per the Miami Herald, Surfside’s new mayor implies they may cut KCE loose.

Surfside became known for deadly condo collapse. Now the town looks to champion reforms

 

[IanCA]

I hope you don't mind me jumping back in here.

1) the pool deck level slab was a critical element for maintaining lateral stability, and its failure put the foundation system into an unstable condition (in other words, sawcut out the pool deck slab and the building is now unstable)

I believe that if the saw cut was made first along the North side of the pool deck, it would isolate the north wing of the building from collapse. Cutting the East, South and West sides of the pool deck / parking deck first would allow columns to punch through and eventually the deck becomes a massive lever, torquing the columns on column line 9.1

2) if you sawcut out the pool deck slab the building is stable, unless you then put some big horizontal loads into the top of the basement columns)

I imagine that as columns punched through, the deck is located by them. If the deck is inclined, lower in the south and higher in the North (at the connection with the building) geometry dictates that either the deck must stretch (but it is extremely stiff) or the columns along column line 9.1 are pulled to the south.

Suggestions welcome.​

 

[MaudSTL]

The Miami Herald is going after the building next door. ‘[Bleep] that wall,’ contractor said when vibrations near Surfside condo got ‘too high’

 

[bones206]

Certainly seems relevant, given the hypothesis that failure initiated at the slab/wall joint along the property line, which happens to coincide with the location of excessive piling vibration.

 

[zebraso]

The Miami Herald is going after the building next door.

The vibration limits are intended to prevent effectively non-structural damage (stucco etc). According to the quote in the Herald, Wiza was talking about replacing a wall, not stucco. That's the basic problem. It's a damning statement.

 

[IanCA]

The Miami Herald is going after the building next door.

Interesting article. Thanks for sharing MaudSTL.

Suggestions welcome.​

 

[spsalso]

Wiza was talking about replacing a wall, not stucco. That's the basic problem. It's a damning statement.

It's a "damning statement" that he is willing to replace a concrete block privacy wall, in order to move his project forward?

That would be a wall that is completely non-structural. And it's my impression that it has mostly not even fallen down. Unaided.

Perhaps he should get a gold star for doing whatever he did so as to ensure that wall did NOT fall down.

I am not understanding how Wiza's actions are the least bit connected to the collapse of the building.


spsalso

 

[Cool_Controls]

It's a damning statement in that it shows a total disregard for the policies that were put in place to protect adjacent properties.

 

[spsalso]

And your thoughts about the seismologist who kept working there, even when he knew those policies were being violated?

And also your thoughts on the seismologist not (apparently) reporting his concerns to management higher than Wiza, or the City? Or anyone?


spsalso

 

[Cool_Controls]

It certainly looks like he was checking a box to collect a paycheck. I wonder who actually wrote the log entry wiza or the seismologist. I assumed the seismologist wrote it to cover his ass, if that was the case good for him. If a licensed professional was involved things may have been handled or at least documented differently.

 

[spsalso]

I suspect that Wiza thought that it would be a far better choice to replace a concrete block privacy wall than to stop the project, especially since it appears he had noted no structural damage up to that point (He was apparently worried about the area near the pool, which he had then completed). It's entirely possible that the seismologist agreed.

After the fact, it appears the wall was not damaged enough to replace it. Surely the CTS tenants would have complained if it had needed it done.


spsalso

 

[SwinnyGG]

The Superintendent stating that he was willing to make repairs to an adjacent structure means absolutely nothing. It's a complete red herring. We do it alllllllll the time. On my current project I'm about to replace a fence and some bushes on the property of a dude who took it upon himself to landscape in the public ROW, specifically because it is cheaper and a more efficient use of my time to replace his bushes than it is to tell the guy to pound sand and spend the next 6 months getting calls from the city after he calls them to bitch.

Unless someone can demonstrate that the pile driving operation next door actually caused damage to the Champlain Towers foundation system, this is a false hole to fall down. In his shoes, I would've done the same thing and probably used the exact same obscene phrase to instruct the crew to continue their work.