Miami Beach, Champlain Towers South apartment building collapse, Part 03 148

[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

Thank you

SF Charlie
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[Vance Wiley]

Regarding the new column caps to be installed/constructed under he existing pool deck slab - -
Does anyone else have a problem with backing up an overstressed 9.5 inch slab with 4 inches of new (fresh) unstressed concrete?
Seems to me the action from here out will be an increase in stresses in the existing questionable slab and the initial buildup of stresses in the added 1 FOUR inch slab beginning at zero.
Then there is the possible difference in the elasticity of the old concrete and and that of the new fresh concrete. So for a while most of the loads will go into the existing slab - and little will go into the new concrete. Splitting hairs there, it seems.
Consider also what drilling under the slab at the first column which failed last week could have caused. Not a good place to be.
Was shoring of the slab required during the installation of the new 4 inch concrete cap? Would that be gunite concrete on the overhead? Bore a hole and feed thru from above?

I dunnoo - - - 'bout this idea.
I see rapt (Structural) caught it.

https://www.townofsurfsidefl.gov/do...0-year-re-certification.pdf?sfvrsn=9e2a1194_3

 

[Murph 9000]

On the demolition and stability of the remaining structure, there are some serious signs that the structure is unstable. On the south end, those columns that lost the lobby/parking slab are a problem. There are also 3 or 4 floor slabs low down at the north end that are visibly sagging down and probably detached from column E2. The elevator tower will help a lot, if there's no hidden damage to it, and the slabs are still firmly attached to it.

I would not be confident about its performance in a storm. At a minimum, I think they need to tidy up the ragged north east section, removing the remaining big bits of dangling material.

 

[Roga50]

Here's a layman's view of the list of "improvements" that the condo they just red-tagged are supposedly undergoing... Link

Other than the generator (ie, elevators not having backup power), I don't see them mentioning anything too serious (so what are they ignoring?) Doubt they'd red-tag the building just for that rather than just close the elevators (which has happened several times down here with older condo's in the past).

 

[Santos81]

although it’s hard to rule out an HVAC unit as the round object in the garage debris.

One of the round objects is the marquee on the vehicle gate. The other roundish object down in the debris field is possibly the patio furniture from 111. It’s hard to see but the pedestrian gate for the terrace of 111 appears to be just inside the right arc.

 

[aggualaqisaaq]

My working hypothesis (for now) is that the precipitating event occurred at or near the 111 planter (the bushes seem to be visible in the TikTok video). Either the slab beneath the planter gave out from the combined effects of corrosion and neglect (perhaps related to that hole/damage visible in the overhead pic) or the column beneath it collapsed somehow. The collapse then spread to the rest of the pool deck, I would imagine similar to this:

https://m.youtube.com/watch?v=6ssbowQjH4A

 

[Js5180]

I wonder how consistent this failure pattern is. Would this mean that the more distant pillars will usually have columns puncturing the slab, but the slab nearest the failed pillar would break across its entire width? That would suggest that the upper parking deck failure happened first, as that’s the only part we know of where the slab “hinged” rather than punctured.

Edit: scratch that. It looks hinged because it’s resting on cars.

 

[Torai]

the center is probably a black cleanup bag stuffed in the bore hole and spread out with sandbags around the perimeter

Actually probably is a person as you first suggested. The picture was probably taken at 10:39 when the sun azimuth was 149° (By rotating image and looking at angle) and at 37° elev. Object height will be 0.60 * shadow length.

https://gml.noaa.gov/grad/solcalc/azel.html

This is slightly Northeast on one of the paths near the beach. Two people. Another nearby (not this image) probably walking a dog. The white band around the dark person is probably an image compression artifact.

Gets more fun with radar images; you can sometimes see metal inside structures from far far away.

 

[hokie66]

It does sound like punching shear was a factor, as there were plans to add to the slab thickness at some columns. Whether that scheme would have overcome the punching shear susceptibility is questionable at best. One thing I would look at with the pieces of columns remaining is evidence of effective slab depth at the columns. A favorite builder's trick is to pour columns a bit high to simplify floor formwork, and that can drastically reduce punching shear capacity.

 

[Js5180]

One has to wonder - with so many columns punching through, was it really a column failure at K/L-9.1/10? This would suggest that only three columns were seriously degraded, but the slab everywhere else was.

 

[DB27]

Drilling took place up to a foot down in order to determine the structure of the concrete below. The work 'yielded some curious results as it pertained to the structural slab's depth' - but the reason as to why the results were 'curious' was not explained

People have been joking about the slab depth but it was as follows:
1-1/4” Pavers on sand waterproofing
1-3/8” Tile & Mortar
2-1/8” Concrete Topping
9-1/2” Structural Slab

I’m dumbfounded that an engineer would leave a cliffhanger inside one of their reports… unless they are leading the way of engineers using the subscription model???

 

[Sym P. le]

I would assume an accident. People drive drunk. Elderly drivers get confused and hit the wrong pedal. People get their foot stuck. In the middle of the night in the dark especially, none of those things alone would be surprising.

Agreed.


You have more faith in the system than I do but I hope they haven't overlooked anything.

One of the round objects is the marquee on the vehicle gate. The other roundish object down in the debris field is possibly the patio furniture from 111. It’s hard to see but the pedestrian gate for the terrace of 111 appears to be just inside the right arc.

The roundish object is likely an object in front of the vehicle. The reason I suspect a pickup truck is the square box that abuts the "broken column" (if that's what it is). The roundish object could be the wheel well or not.

What is missing in the frame grab is the column at the back of stall 27 which is why I pose the hypothesis that the two concrete peices bent over the back of the vehicle are the remains of that column.

Additionally, if the slab dropped into the parkade, I would expect a notable depth of debris on the parkade floor but I don't see that.

Fair game on calling whether the vehicle is parked sqaure in the stall or not. At any rate, I hope it is useful to post my suggestion as to what the image shows and its positioning beneath the pool slab/building footprint. I didn't expect to get that much out of this little project. I only did one frame and perhaps other frames can lend more clarity but of the ten frames that I glanced at, this one seemed to offer the most clarity.

https://m.youtube.com/watch?v=6ssbowQjH4A

A chilling animation of what likely happened, and worse. The animation is likely predicated on sound (but marginal) column caps. From the images of the actual collapse, the column caps or what was left of them (after corrosion) were minimally provisioned and gave up without a fight, ergo, after the first column or grid line gave out, the remaining slab came down as one piece.

 

[dold]

Alright.

Need some help. I'm working on...something...

I am soliciting everyone's best guess at the dead loads on the: pool deck, lobby, parking (lobby level), typical residential, and roof. Kindly note, I'm looking for dead loads as described by ASCE 7 / IBC. Not subjective live loads (such as "I consider tile = live load). I will be using live loads as required by ASCE 7-16 for now.

 

[Roga50]

Here is the inspection report for the Crestview Towers condo that was red-tagged and evacuated tonight: Link

 

[DB27]

Further evidence of the initial collapse in the garage. On the left entrance wall of the garage, there is a reflection of flashing vehicle emergency lights.

I have attached the “enhanced” clip below:

[URL unfurl="true"]https://res.cloudinary.com/engineering-com/video/upload/v1625292979/tips/trim.369046FC-DCF4-4D56-9ABC-FA2B578C3978_tm2dmw.mov[/url]

 

[dik]

Is this a crime scene? and are they destroying evidence?

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

-Dik

 

[FacEngrPE]

NIST Will Conduct Technical Investigation Into the Collapse of the Champlain Towers South Condominium, The investigation could take years, lead to recommendations for building code improvements. NIST News, June 30, 2021

https://www.nist.gov/news-events/news/2021/06/nist-will-conduct-technical-investigation-collapse-champlain-towers-south[/URL]]The team found that the collapse met necessary criteria to invoke the act: It was a “major building failure at significantly less than its design basis, during construction, or while in active use.” In addition, NIST determined that “a fact-finding investigation of the building performance and emergency response and evacuation procedures will likely result in significant and new knowledge or building code revision recommendations needed to reduce or mitigate public risk and economic losses from future building failures.”

I think that NIST's initial finding of the collapse meeting the criteria for an investigation by the National Construction Safety Team Advisory Committee is well established. This should alleviate some of the concerns related to preserving evidence.

https://www.nist.gov/disaster-failure-studies/champlain-towers-south-collapse[/URL]]On June 25, NIST began deploying a team of six scientists and engineers to collect firsthand information on the collapse. Since then, NIST experts have been working with federal, state and local authorities to identify and preserve materials and information that might be helpful in understanding why the collapse occurred.

Link to the NIST Disaster & failure studies page for the National Construction Safety Team Advisory Committee.

NIST Disaster & failure studies Champlain Towers South Collapse

 

[Santos81]

The roundish object is likely an object in front of the vehicle. The reason I suspect a pickup truck is the square box that abuts the "broken column" (if that's what it is). The roundish object could be the wheel well or not.

What is missing in the frame grab is the column at the back of stall 27 which is why I pose the hypothesis that the two concrete peices bent over the back of the vehicle are the remains of that column.

The site seems to not like me. I’ve twice composed an extremely thorough reply and hypotheses but find myself logged out automatically by the time I get to submit.

In the mean time to be brief:

The vehicle in bay 27 is a SUV (possibly a Ford Explorer) positioned head in. The square box is a planter from outside 111, but I’m not convinced it’s the one in cluster positioned directly above the column that is no longer visible. I think it may be the one to the west.

I don’t see a failure of the pool deck occurring first; rather a slow column shear failure below the pool deck that is made unusual due to the already deteriorating structure and pendulum behavior of the planter as it separates from the slab. This generates a non-linear alternate load path that spreads out in an almost circular motion. Of the elevated pool/plaza deck, the parking area seems to be last portion to fail but the load is still continuing back through the superstructure at the lobby level until it too cannot carry more.

I’ll elaborate after some rest. In the meantime, short of DoD Shock Tests, or an intentional demolition, it would be shortsided as professionals to look at this as anything resembling typical or simply explained. That method did not bode well for those at the start of this tale.

To sign off with a moment of levity

I wonder how they got 13" cores out of a 9" slab.

Definitely used a Men’s Tape Measure. Women’s would have been an inch short.

 

[Nalzoe]

Has the more recent (2020?) Morabito report that the media has referred too been made publicly available yet?

 

[Sym P. le]

There is a significant amount of debris missing where the first collapse section appeared to drop straight down. It should be piled up three or four stories deep like the rest of the pile.

Also,some interesting items atop the debris pile. The northeast stairwell wall (I believe a section of five of the uppermost floors) landed about 100 feet from its origin.

Strings of column sections (a total of ten make that nine, in one string) all detached from the slabs and apparently falling over as a single item.

 

[Murph 9000]

There is a significant amount of debris missing where the first collapse section appeared to drop straight down. It should be piled up three or four stories deep like the rest of the pile.

I believe a significant portion of the south side may have collapsed slightly northwards. If you study the collapse video closely, the southwest quadrant of the penthouse and access corridor appear to hinge downwards on roughly the 4 line of columns (the north side of the corridor on all floors). If that was representative of most floors, the slab hinging on the 4 columns, the debris pile would be moved a little to the north.