Miami Beach, Champlain Towers South apartment building collapse, Part 09 139

[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

SF Charlie
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[Spartan5]

I am just curious if this is, what process would have been done to leave this shape of a mortar patch? They're too uniform for it to be by hand one would think. Would a template be used in this process?

Ooooh look at all those repairs, I bet those beams are like Swiss cheese on the inside.

Actually, it looks like those are simply imprints of the patches that were used to fill the knots in the plywood that were used for the forms.

When you’re a hammer, everything looks like a nail. When you’re an unsupported theory, everything looks like evidence.

 

[Demented]

As I said, it was a question to the method. If we get attacked for asking questions to something we don't know now, then there is more wrong with this world than I thought.

Thank you for answering my question though. If those were repairs, they held up good. Would have been pretty damning evidence against concrete repairs.

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

 

[sbisteel]

If we get attacked for asking questions to something we don't know now, then there is more wrong with this world than I thought.

In the context of at least 1,000 posts of pure uninformed conjecture, people are going to get testy with basic questions like these.

 

[gonefishing2]

This black area the red arrow is pointing to is troubling to me. It looks like part of the very large PH balcony has fallen and we are looking at black roof in this area and not vertical PH parapet. Hinged slab near sliding door wall.

No a 3/4" masonry bit in a hammer drill is not going to take out 1/2" or 5/8" rebar, but it could kit and glance off bar and break up what little concrete bond there is between rebar and suspect concrete such that it renders the short poorly developed steel from proving any say negative moment capability. You know when you hit steel with masonry bit, so what do lots of workers do in this situation, they tilt the drill a little bit and keep drilling past it.... Problem is they have to tilt it perhaps more than one way to figure out which way the rebar is running, all the time they are hogging out the 3/4" hole much larger and detaching or delaminating the rebar from the concrete.....

 

[gonefishing2]

I would like to point out, after all the postings here, it was Building Integrity's Video that came up with delamination theory, and not any of the Structural Experts on this Forum. Perhaps the experts on this forum already knew that, but was just holding back their theory?
I would like to also say a lot of the structural expert analysis is based upon a perfect world and the original design drawings, and NOT the as-built configuration that we really know was not as designed.....

Let me also say, if I were a practicing Structural PE, I would be going by the book too in my analysis as I would not want any liability from speculation. However, for the non-PE types here there is no risk to exploring concepts based upon the real world facts and best public information available to date as to current condition of building, and not brand new design condition of perfect world structure..

If the pool deck slab at the planters next to building failed first, then the core sampling of the slab (Core A) in that area, probably contributed a lot to the sudden failure coupled with heavy rain loading that area after recent loss of a steel rebar continuity while probably causing more delamination in that area...

 

[BadgerPE]

Question for concrete guys.
Would this be indicative of a column repair location? I am not concerned with the cracking as I wouldn't be surprised for this to be related to the removal. I am just curious if this is, what process would have been done to leave this shape of a mortar patch? They're too uniform for it to be by hand one would think. Would a template be used in this process?

Since they appear shallow and aren't broken off, my vote would be for knots in the plywood formwork. These would be limited to a single-ply depth. The roughness of them further advances this theory in that the inner plys of plywood aren't sanded smooth before gluing.

 

[MaudSTL]

South African Architect Mike Bell has published a new simulation with narration.

https://youtu.be/2INrz2u9-sQ

 

[Sym P. le]

Included in the video is a 3D view of the TikTok view into the parkade which makes clear how the column line recedes into the shadows. The large grey block sits in front of the missing column while the upper portion, if not obscured by a sagging deck would be dimly lit to the point of being faded out.

 

[rodface]

@MaudSTL this is a nice video. His explanation nicely summarizes and illustrates the pool deck collapse theory. I did not realize that the east stairwell shear wall ended up flopped all the way over to the west.

Edited post to remove the suggestion of a "pool deck theory". The video explains the likely mechanism of the collapse well. Discussion of the triggering event is not part of it.

 

[Demented]

@Thermopile
I'm sure you've seen it when those same people drill the same way in steel structures. Oooof. You can feel the building vibrate as they do it. The angry angry chatter of interupted cuts and the vibrations associated with.
Just kicked back a bunch of cnc work because it chattered like crazy in the wooden jig with 3.5" unsupported stickout on thin material.
Why is the woodshop machining metal?
I don't know, but we renovate condos.

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

 

[Auri]

it is a legit forensics technique which has been used to obtain murder convictions

The type of enhancement is critical. Knowing the context of an image or video and the mechanisms of each enhancement is part of being a photo forensic analyst. Otherwise one could generate highly misleading pictures by blindly using the same tools the professionals use. In recent years AI-based enhancement has begun to add data to pictures... even a layperson nowadays should be especially careful about media from untrustworthy sources.

This black area the red arrow is pointing to is troubling to me.

It's an artifact of taking a video of an LCD screen. The missing white up top is compensated for by the missing black right below, indicating the LCD was in the middle of a transition. The detectives must have the original feed and just haven't released to the public.

 

[gonefishing2]

@Demented, yes during college, I worked in machine shop and welding shop, designing, fabricating and installing creative field repairs. My dad's contact's got me the job, but my open mind and aggressive desire and ability to learn coupled with baseline skills and work ethic kept the job for me. In that time, no engineering designs to work from. It was a different era. Mostly supporting manufacturing plants and facility and equipment repairs.

I had read the Topic of this Thread is Forensic Engineering with a sub-topic of Engineering Failures and Disasters. How does this limit this forum to just talking about pure structural design criteria stuff without considering real world forensic pieces of the puzzle?

PS: No engineering disasters from the work I did.... But plenty of margin....

Auri, thanks for that response. I realize everything may be there in the poor quality edited video we have, but something just does not look right about the middle section vs the right section near the top....

Demented, got any old Monarch Gear Head Lathes in your shop? Built to Last forever with maintenance and repair.... No Buggy Software either....or a Vintage Lincoln Buzz Box?

 

[CE3527]

Not sure if anyone tried this already, but I tried to create the same angle in Google Earth as the security camera footage of the collapse. It's pretty clear that the middle part of the building has already dropped about one story at the beginning of the video.

 

[Auri]

What a good interview... (incognito if you have to)

https://www.palmbeachpost.com/story...raeli-team-found-majority-victims/8021350002/

Vach almost makes it seem like we handled the concrete debris and they handled recovering the people. I hope we were as meticulous about labelling the column/slab pieces before transporting to Doral. It would greatly help diagnosing any internal building failure as a suspect cause of the plaza collapse.

 

[Murph 9000]

Not sure if anyone tried this already, but I tried to create the same angle in Google Earth as the security camera footage of the collapse. It's pretty clear that the middle part of the building has already dropped about one story at the beginning of the video.

Yup, and it's basically the entire 10 & 11 stack that has dropped (on the facade / south span, at least), in a bottom to top collapse. I can't be certain, but I suspect the facade has been pulled slightly inwards / northwards by the slabs hinging down at about the 4 line / central corridor (maybe briefly resisting on the 8 line before reaching 4). It also looks to me like the master bedrooms (left side) of the 12 stack are fully involved in the early stage of the tower collapse, with the M–N span hinging downwards on the N columns.

It seems quite clear to me that the opening frames of that video clearly show catastrophic failure in the 9.1 line, with I,K,L,M gone somewhere low down, probably starting at the ground / basement level.

 

[zebraso]

It's pretty clear that the middle part of the building has already dropped about one story at the beginning of the video.

Yes, but then some way back in the thread parts questioned whether the roof had collapsed (or hinged) initially before what was below it started moving, which could be dismissed easily if the video started about 1 frame earlier. And then someone wants to know how the lights are still on below if all floors had progressed 1 or so levels downward. And it goes on from there. I think Building Integrity lined up the architectural features in the eastern most section with the floors under question to tell if the roof had progressed before the rest. I right now for the life of me I can't even recall what he thought about it.

Edit: Ok Building Integrity does not believe the roof dropped or hinged first. But what he shows in his diagram "hinges" somewhat on whether the line he draws for the top of the penthouse is actually the leading edge parapet wall or the back edge hinge line where what you are seeing as the PH level (it's dark) is actually the top of the roof. So: grainy image.

 

[gonefishing2]

I truly hope MaudSTL will contact her friend in Israel, as they probably already know the real truth. Look how fast they generated a model and found bodies, and got out of dodge. They have lots of experience with collapsed buildings in their neck of the woods...

 

[zebraso]

The type of enhancement is critical

What you are saying I agree with. You wouldn't want to use the standard type used to enlarge a family portrait. There you would have the intent of smoothing details to eliminate grain. Instead you would produce a grainier image while enlarging which is counterintuitive to photography. The problem here is the originals are not forensic quality to begin with. In the case I cited there were two subject matter experts (forensic odonatologists). The one that analyzed the enhanced image reached the opposite conclusion of the one that examined the unenhanced image. There is a difference between pure speculative folly and forensics of course.

 

[MaudSTL]

I truly hope MaudSTL will contact her friend in Israel, as they probably already know the real truth.

I contacted my Israeli friend just this past week. I specifically asked her to see if she could find and translate the Israeli Channel 13 interview with Gabe Nir. I have been hoping Gabe might provide more details in a Hebrew interview. Anyhow, my friend hasn’t been able to find the interview so far, but she’s going to keep looking. I’ll report if she tells me anything else.

 

[Seppe]

I would like to point out, after all the postings here, it was Building Integrity's Video that came up with delamination theory, and not any of the Structural Experts on this Forum. Perhaps the experts on this forum already knew that, but was just holding back their theory?

Or perhaps not every poster here is as compelled as you and a couple others seem to be when it comes to throwing every strand of woulda-coulda spaghetti against the wall to see what might stick. This isn't a competition to see who is willing to dig into the bowels of minutiae just for the sake of a water-cooler talk.

I'm not at all opposed to the sharing of thoughts and ideas, but I also think there's a point in time where, as folks who weren't on the ground as part of USAR or NIST deployment, we reach a reasonable limit on just how accurate and productive a belabored attempt to analyze/assess can be. Speaking for myself, I reached that point about four or five thread iterations ago.

I continue to believe that this structural failure was the result of a series of compounding, unspectacular issues at the pool deck level. I don't think the confluence of these issues and the degradation and resulting destabilization needed to have an acute vehicular impact or "butterfly flaps its wings in Brazil" roof-level sequence to be considered legitimate and plausible.