Miami Beach, Champlain Towers South apartment building collapse 151

[bugbus]

Partial collapse of 12 storey apartment building in Miami Beach:

https://www.google.com.au/amp/s/

http://www.dailymail.co.uk/news/art...-building-collapses-sparking-huge-search.html

Was built in 1981. Not much information as yet.

Building profile:

https://www.miamiresidence.com/surfside/champlain-towers.htm

 

[GPR_Tech]

Champlain Towers Plans LINK...

https://www.townofsurfsidefl.gov/do...-collins-ave-1979-plans.pdf?sfvrsn=bd2a1194_2

 

[bugbus]

Are there structural drawings of that transfer beam BM35?

I am on my phone and it does not want to open such a large PDF

 

[jrs87]

Discernable column remnants?

 

[Kreemerz]

That area near the pool does look like subsidence or a slight depression.

Is there a garage underneath?

 

[jrs87]

Yes, but not under pool itself. The small spa drained into the lower level? Columns to lower level can be seen on pool deck area.

See Ingenuity (Structural)26 Jun 21 02:3 for image taken from below the pool deck.

 

[271828]

Are there structural drawings of that transfer beam BM35?

Beams BM33, BM34, and BM35 are in the attached beam schedule.

Stirrups in BM33 and BM34 look odd to me. Seems like the shear would be nearly constant on each side of the point load.

 

[799931]

Looks like PFI - Pressure Injected Footings were the deep foundation system (S3 typical piling section) ?

https://www.keller-na.com/expertise/techniques/franki-piles-pifs

 

[WannabePESE]

In my opinion, the collapse looks like it initiated somewhere between grids H-N. The area with the transfer beams was part of the secondary collapse.

 

[MOJOJOHN]

CONFUSION?

Foundation drawings shows PIF's (pressure injected footings). Then call out 14 x 14 precast driven to 50 tons (100 kips).

14x 14 precast are usually driven to 75 kips and I doubt that they would ever be used at 100 kips in South Florida.

Likely Franki or other PIF's at 100 kips. Franki's were being used in South Florida in that time period.

Videos show what appears to me as a failure that started at or near the bottom of the building.

Without speculating as to the cause, which would not be ethical as I am not involved, I would pursue the question of column failure at the
garage level as suggested by others in this forum. Photos show corrosion and indication of previous flooding of the garage which is accordance
with resident reports.

Was the concrete remediation started? Had garage columns been chipped to repair without multi floor shoring? Had past repairs to the columns been made?

Remediation plans call for no more than 1/4 of a damaged column be repaired at one time and call for shoring.

Mojojohn

 

[sdh4]

There's a TV news interview out there of with 3rd party testimony from someone on the phone with a victim who was complaining right before the collapse about the pool patio area sinking. (Edit 6/26/21: I am referring to the video link posted by Jon43442, above, where the interviewee at 1:30 says 'She was on the balcony on 4th floor and she was telling her husband in a frantic way that "the pool was sinking, the ground was cracking," ... "The pool is sinking. The ground is shaking" ... "The building's shaking! The building's shaking" and then she screamed a screech and the phone went dead.')

It's actually pretty plausible that a patio slab failure could have been the initiating event here:

There is otherwise not a whole lot of reason why the collapsed portion of the building zone should have caused as large a portion of the patio to fail as it did. Water ingress through failed waterproofing in the patio area could have damaged rebar connecting columns to the slab leading to shear failure and a single initiating punch-through of a single column. Such a punch-through could overload neighboring columns with similar damage leading to a cascading collapse in the patio zone.

The suspended patio would now have very high tensile stresses in its rebar with the rebar acting like the cables in a suspension bridge. The rebar on the bottom (east-west oriented) seems to have torn out relatively easily, relieving those stresses and potentially saving the southwest corner of the structure and making the load be carried in the north-south oriented rebar.
The extreme tensile stresses in the north-south oriented rebar from the collapsing patio would mean that the patio level slab, instead of providing lateral stabilization to the columns in the portion of the building that failed first, would instead be destabilizing those columns.

From the perspective of the patio slab, the (relatively) stiff intact columns become stress concentrators for those tensile stresses. The columns under the building proper, probably bigger and better protected from water/corrosion than those under the patio, would be less likely to have punchout failures and more likely to transfer the tensile loads into the sides of the columns. Now we have highly loaded vertical columns with a significant sideload. It would only take one of these to buckle to initiate the major collapse. I am thinking of our undergraduate mechanics of materials lab where students put a rod in compression and then tap it from the side and it buckles instantly. With few internal walls, such a single column failure may have been enough to destabilize the larger structure.

 

[799931]

Where do the call out 100 kip driven piles?

The PFI call out on S3 is for 300 kips

 

[WannabePESE]

General Structural Note #3 on S11 spec's precast piles to 100 kips. FYI the North Building is included in the PDF, and there are differences between the two.

 

[MOJOJOHN]

799931

Page S-11 notes state 14 x 14 at 50 tons.

 

[dik]

A couple of observations... it appears there is a lack of concrete cover to the reinforcing... bad news if there are chloride corrosion issues... also the 40 year inspection report was developed to expressly eliminate this type of failure.

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

-Dik

 

[dik]

40 years may be too long a stretch... maybe 20 or 25 years would be more appropriate considering the 'corrosive' environment...

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

-Dik

 

[Seppe]

Slabs seem awfully thin, at least by today's standards for mild-reinforced flat plate construction. And no drop caps? I see square/rectangular regions shown in hidden lines circumscribing the columns on the original CDs, but no specific annotation indicating the presence of an actual thickened feature. No stud rails or comparable shear reinorcement either, apparently (though probably a bit before the time of stud rails).

The sensitivity of a punching shear mechanism is well-documented, with transfer of unbalanced moment at the slab-column joint component always requiring close consideration in addition to the direct two-way shear component. Eccentricities and misalignments in the concrete frame, whether subsurface settlement/subsidence-related or otherwise, only serve to magnify the system's sensitivity.

Just seems like a confluence of a lot of less than ideal attributes: subsurface element performance/displacement, a comparatively sensitive structural system (two-way flat plate, not to mention some big-time transfer girder elements down low), and an unforgiving coastline exposure.

 

[thejonster]

I have read through this entire thread, so I think this is new information here but my apologies if this is already been posted. A link to a story originally on the New York Times from The Drudge Report says that an engineer warned in 2018 that major structural repairs to the pool deck area were required. This work was designed and ready to be performed. This gives new understanding to the condition of the building that needed to be addressed.

Engineer Warned of ‘Major Structural Damage’ at Florida Condo Complex in 2018

https://dnyuz.com/2021/06/26/engineer-warned-of-major-structural-damage-at-florida-condo-complex/

 

[thejonster]

As has been suspected here the report documents a lot of cracking and concrete deterioration due to environmental damage. And has been noted before many complaints by the residents of water intrusion. Waterproofing near the pool had failed and was contributing to the environmental damage, partly due to poor design where water had nowhere to drain to.

 

[bones206]

The potential unzipping of rebar may have commenced at a construction joint - the rebar was developed into the slab portion that collapsed, and as the slab/s fell it ripped/zipped the reduced-cover rebar in the span that remained. Notice how 'clean' the exposed slab edge at the roof level.

I can’t help but draw a parallel to the Hard Rock collapse in New Orleans, where a design flaw created a weak plane that inadvertently allowed a section of the building to collapse without dragging down the rest of the building.

 

[dik]

Somebody speaks out...

https://www.cnn.com/videos/us/2021/...surfside-building-collapse-smerconish-vpx.cnn

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

-Dik