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

[dik]

thread815-484587
thread815-484717
thread815-484915
thread815-485059
thread815-485171
thread815-485223
thread815-485379
thread815-485535
thread815-485637
thread815-485844
thread815-486084
thread815-486593
thread815-487022
thread815-488247
thread815-489644

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

-Dik

 

[Sym P. le]

What I'm curious about is why or how the column that was supposedly under the wall, punched through east of the wall?

The planter wall is not a structural component. The slab punches through and the flaky planter wall falls over or is pushed out of the way. If the drawing overlays are taken literally, the planter wall is offset from the column center line anyway.

 

[zebraso]

Without analyzing that too deeply, the thing the occurs to me is the planter wall has no strength. That's why it cracked and broke when the deck lowered under it. The column supporting the planter wall alone is not significant. it's not taking any significant load from the planter wall. I may be off base as to what you are getting at. I mean to say the planter and it's contents are not transferring load to the top of the column via the wall. The planter wall would have given way to the column on the way down. There must be a photo that shows that.

 

[Sym P. le]

I agree. A scenario in which the planter wall would be structural is if it were cast as part of the slab complete with integrated rebar (as inverted T used as a stiffening rib).

 

[Sym P. le]

Thought project: The punch out failure in this situation is unconventional - /[sup]-[/sup]\ as opposed to \_/.

This might have hidden both top and bottom surface indications of its presence.

 

[zebraso]

/-\. Boy it all comes back to the pencil points.

 

[Sym P. le]

And if we're following the bread crumbs backwards, we now have column 76 punching out first, followed by the planter column (at least by documented evidence).

This is consistent with the column layout with the greatest span south of these two columns at 29'-8". If that span is not properly supported (edit: by the two columns in question), the area of slab affected is roughly 67' x 49'.

As a curiosity, these two columns also create a bulls eye for the deck collapse though likely only since there were interruptions one bay away on each of the four sides.

 

[zebraso]

What is the dark ring around the base of 76 at the slab in the walk through? It's odd looking to me. That pooled water is a haunting thing. Shouldn't there be evidence of staining or dirt on the column if sediment is following the water as was stated? Something is odd in that photo.

Edit: is that pipe coming down the plater column from the planter drain. It dumps onto the floor? If so I am not surprised it is dry under it.

Edit again: the actual drain is slightly s/e of the column. But I guess if you were going to dump it you would route it over to a column. And that's the closest one. That's not the only pipe down column I noticed in the walk through. In fact I don't think I noticed that one until now. I just can't recall that it mattered much.

 

[Reverse_Bias]

That wall is over K13.1 (Space 75) which was the most heavily loaded column on the deck and is one of the two possible initiation points for the punch shear. See Igeezers post in PT 15. The crack is consistent with the middle of the deck trying to butterfly downward like it ended up post collapse.

 

[Red Corona]

> The punch out failure in this situation is unconventional - /-\ as opposed to \_/.

Yes, I mentioned this several threads back and said I would put some reasoning into what that might mean, but I never got around to it, did I?

Amazing that this pic has just come out now. It seems to clearly show the planter has dropped a long way, maybe 2", at its NE corner. Hard to see how that's possible without the slab already starting to detach from that column just to the N. And while it might only be clear in retrospect that that puts the building at risk, surely a responsible engineer can see that that was already putting the pool deck (and therefore the garage) at risk, and should have ordered immediate shoring and investigation?

> What I'm curious about is why or how the column that was supposedly under the wall, punched through east of the wall?

Interesting question. You'd think, if the slab was failing from the east, the planters sitting on top of it would drop to the east as well, and end up east of that column, but that doesn't seem to have happened. That whole section of deck, to the next column line west, is all punched through, so did the deck hinge from that western extent of the break and pull the planters west of the column?

I still don't think this can have been the first part to visibly collapse into the garage though because it's quite close to the garage level elevator entrance, surely those people that parked up last in the garage would have seen it. They got into that lift only a few seconds before the main deck collapse.

 

[zebraso]

" pull the planters west of the column" Is that the top course of the CMU wall lying in a line to the east of the column? If so it might be telling how far away it fell.

Edit: as well as the angle. It's further away near the trash can. So then the deck was hinged north to south when it landed. It fell further toward the south. Does that make any sense? probably not. The missing part would be that it slid down the slope further on the lower end. so the the deck would have to be angled down towards the s-e. I think.

edit2: scratch that. the effect of falling over the car lump probably pushed it out further on that end. I mean if that is actually the top layer of the wall, which it mostly has to be. I would like to know why it did not break into more pieces though.

once more: well maybe the top of that wall is a lintel. obviously.

Ok this is the last one: Forget all that. That is likely a column remnant from the tower. My apologies. Missing cmus are probably buried. I thought this was far enough away to not have a debris pile on top. Hard to believe the trash can is sitting there like nothing happened. There might, *might* be a piece of the planter cmu east of the trash can.

 

[MaudSTL]

I still don't think this can have been the first part to visibly collapse into the garage though because it's quite close to the garage level elevator entrance, surely those people that parked up last in the garage would have seen it. They got into that lift only a few seconds before the main deck collapse.

From a witness statement perspective, whatever fell first fell after the Vazquezes got into the elevator. They heard a very loud cracking sound while in the elevator lobby, just before they entered the elevator. They were within the elevator and going up to the lobby when the deck collapsed at ~1:15 AM.

Also from a witness statement perspective, all witnesses who described the deck collapse at ~1:15 AM describe it as a single big collapse rather than a series of two or more discrete collapse events.

If you’re thinking about the crashing sound at 1:10 AM, it may have been rebar breaking and not not concrete falling, as the Vazquezes did not report seeing anything fallen in the garage. However, we don’t know what space they parked in or what their path was from the parking space to the elevator lobby. So it’s conceivable that a chunk of ceiling fell down outside their line of sight.

 

[Brian Malone]

And while it might only be clear in retrospect that that puts the building at risk, surely a responsible engineer can see that that was already putting the pool deck (and therefore the garage) at risk, and should have ordered immediate shoring and investigation?

Yes, this makes sense. The situation appears to be quite complicated for an engineer and/or engineering group to be responsible for a structural integrity analysis. If a highly cautious approach is taken and nothing bad happened later, then you would probably get hammered as 'chicken little' by the residents/owners for inconveniencing them with all the shoring, cost and access closures and/or sued for harm due to potential reduction of property value and your competence would have been questioned. If a conservative approach is taken ( as appears for the Champlain Tower), working within the wiilingness and financial ability of the residents/owners and something does happen then your competence will be questioned. Certainly, many of those who could have affected the tower outcome have pondered many 'would have/ could have/should haves'.

 

[zebraso]

At the risk of sounding like an idiot, I am just providing this screen capture from Penagwin from many threads ago.

Some evidence that the top course of cmu could stay together if the wall falls. This was said to be after hurricane Wilma. I assume the wall caps are responsible. I called them lintels for some strange reason.

There is also this capture from CE3527 from the same thread edit: note added by me.

Within his red circle of the column is the opposite side view of the line of concrete (resembling a column)and this angle looks like CMU. I hesitate to say it's the top of the planter wall, but.....

Thank you for your patience.

edit: second photo to add marks pointing to horizontal concrete section I am referencing. Forgot to add question mark. CMU (bottom opposite caps) apparent to the right of "planter column".

 

[Sym P. le]

New Building Integrity video at youtube

[URL unfurl="true"]https://m.youtube.com/watch?v=M0UtmbRAL9M[/url]

 

[Brian Malone]

Sym P. le Josh of Building Integrity gives a very measured and clear explanation on the warning signs of punching shear that should have been recognised by an engineer/engineering firm involved with structural integrity evaluation. Very interesting observation on water flow on the column surface - I am going to start paying attention for this when I am in a parking garage type structure! A persuasive case can be made to question why was shoring not immediately recommended for installation to address the pool deck instability. This still appears to be a test case study/precedent study on failure propagation - only in hindsight is the threat to the tower recognized. Were the materials and techniques of construction at Surfside dramatically different than standards of the time? Maybe it has already been asked or stated in the many parts of this thread: Is there a risk to a whole generation/era of structures built in a similar manner?

 

[Reverse_Bias]

The planter would be removed as part of the overall renovation plan just getting underway at the tower, he said.
Stewart said he remembered seeing some roots in the crack, but engineers consulted by the Herald say that wasn’t enough to determine the cause of the break definitively. “Part of these visits was to monitor the building, so if you see a significant change in something, that should be a red flag,” said Dawn Lehman, professor of engineering at the University of Washington and a consultant on the Herald’s collapse investigation. While it is possible that roots damaged the planter, it is not the only explanation for the gaping crack, nor even the most likely given the timeline and condition of the slab below, Lehman said

I'll play devils advocate here. The timing and location are very suspicious that this was a deeper problem related to the collapse. However correlation never implies causation. There is a nonzero possibility that the planter crack was just do to roots and nothing more.

Arguments for this being roots:
Roots were observed inside the crack.
A large part of the crack is vertical, hard to accomplish by deck sagging.

Arguments against roots:
The location is very near the heavily loaded part of the deck
The timing is right before the collapse
It appeared suddenly
These type of major cracks were not seen in other planter boxes (As far as I've heard)

 

[Sym P. le]

Is there a risk to a whole generation/era of structures built in a similar manner?

Perhaps from certain builders.

 

[Red Corona]

Roots add extra material, you can create cracks by root infiltration and growth but you'd expect them to push the structure up and out, not down. I can't see any way in which the planter being lower than it originally was could be caused by roots.

Edit: watched the BI video now, and he also addresses this, and points out that you'd also expect a much slower crack growth and water/organic staining if cracks were caused by roots.

You can actually see (and probably measure) the amount by which that slab is not planar from the pics, as well.
Edit 2: and you could do that from the 2020 picture, too - which shows a significant depression already, not sure if that was designed or if it shows flexure already a year before - and compare

 

[zebraso]

... is indeed a column, 75 to be exact.

I may have failed in the ambiguous nature of copying the original photo from a prior thread in which column 75 was already circled and the actual subject. I'm talking about the horizontally laying column-like feature that is about 6-7 feet of so to the right of 75 in the photo I provided. The reason I used that photo (other than convenience) is from that angle you see the opposite side of the feature which appears to show the hollow structure of cmu's. As far as I have known from the beginning 75 is not lying horizontally on what remains of the deck. So I am not talking about 75. In Reverse Bias photo the feature stretches left-right in the foreground in front of 75. It was once speculated to be a column that fell from the tower. There are such columns to be seen. But that was from a much further view point from above. If it's a matter of enlarging the photo to focus more on what I am talking about I can do that.

 

[Sym P. le]

I see. You make a good point as it confirms that the upper portion of the planter wall is reinforced cmu's