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

 

[dold]

I'm all in with @sdh4 on the patio/lobby/pooldeck slab being the initiator here. Obviously there were concerns/evidence of corrosion in the pool deck slab. And multiple eyewitness accounts indicate that the "pool area" slab had dropped one or more panels prior to the superstructure collapse.

Looking at the video it appears that the column on grid I/9.1 was the first to go, although I can't see the interior columns to the north.

See attached snip from the lobby level slab. A couple of items regarding the yellow area and the column with the arrow pointing at it:
Lets say:
+10'-10" = pool deck level
+11'-10" = plaza level
+13'-4" = lobby level

1) this looks like a low point (+10'-10" only open to the pool area to the east) where the slab would seem to be at higher risk of corrosion. ;
2) there is a 2'-6" step in the slab at this column joint.

2.a) this leaves a decent offset between a potential lateral load implied by a failed slab panel (possibly yellow area?), and the restraint at the primary deck at +13'-4".​

If the yellow area collapsed first or another area at pool deck level collapsed first then triggered the yellow area to collapse doesnt really matter I suppose. If the yellow area fell at any point I would start looking at some amount of lateral force being applied to the column between two supports (foundation/basement slab and the slab at lobby level).

Next, perhaps since all the columns along grid 9.1 are tied together with a beam at the slab step, if column I/9.1 (i.e. "the suspect column") collapsed first, that could potentially mobilize a force on grid 9.1 columns acting to the west, with load path bonus from the steel in the perimeter beam.

This seems to be reflected to some extent in the collapse video - the columns along grid 9.1 are among the first to go, starting at the suspect column and propagating east.



Also, I highly doubt any sort of mechanical equipment had anything to do with this.

 

[dik]

Having done dozens of parkades... slope and drainage is a real engineering issue.

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

-Dik

 

[Lnewqban]

The second part of this video seems interesting to me.
The flashing light coming from next to the elevator roof machine room could be from the rupture of the power supply wires of the AC rooftop unit while falling down.

https://m.youtube.com/watch?v=KR29pLccutY

"Where the spirit does not work with the hand, there is no art." - Leonardo da Vinci

 

[spinspecdrt]

This is the most believable statement in this entire thread.

 

[dik]

cute... but there are other parts that are OK, too.

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

-Dik

 

[missstructures]

@dold <
Looking at the video it appears that the column on grid I/9.1 was the first to go, although I can't see the interior columns to the north.>

This is exactly the column that stood out to me.... It kinda looks from aerial that it could be where the planter was located extra load and water infiltration and maybe not as easy to see during a visual inspection.

The waterproofing may not be a structural issue, but the slope and drainage definitely is a consideration and coordination that should always be considered. Even now I've seen lots of architects try to apply waterproofing to a flat slab and then "slope the finishes"..

Obv lots of speculation at this point, but as engineers our brain is trying to find an explanation to this horrible tragedy.

 

[spinspecdrt]

@missstructures I agree with columns on 9.1 line. Particularly @ I and K line. Both are exposed to planter box at lobby level.

 

[Engr1888]

Below is an image taken from a youtube clip on the sister building. The column doesn't look safe with the cracks and concrete spalling.
Surprisingly residents are still allowed to live in the building, given the witnessed catastrophe.

 

[Murph 9000]

Below is an image taken from a youtube clip on the sister building. The column doesn't look safe with the cracks and concrete spalling.
Surprisingly residents are still allowed to live in the building, given the witnessed catastrophe.

That's from

https://youtu.be/qTUykkOSLEw

They say that's Champlain Towers East, which is the much newer of the three buildings (1994, I think), which makes it all the worse. Champlain Towers North is the one which is near identical and the same approximate age as the South tower that has collapsed.

That looks about head height, so unlikely to be vehicle damage, it must be corrosion damage. I'm not an expert on corrosion in RC, but up high on the column suggests to me it's probably coming from the slab above rather than rainwater from vehicles. I know how destructive the ocean environment can be, but that's scary. How bad is the pool deck slab as a whole, if that's the state of the columns supporting it?

I certainly wouldn't want to be within a block of that building right now, until it's been properly surveyed (and appropriately shored up / repaired).

 

[IEGeezer]

ALL of the columns in the initial collapsed portion are Type C at the exterior and Type G at the interior. These columns have quite a bit of rebar at the lowest levels 12 x #11 in 16 x 16 (Type C) and 10 x #11 in 14 x 18 (Type G.) Both types near the maximum reinforcement ratio, once concrete spalling occurs they would theoretically be over code allowed ratio and need to be strengthened. But, they weren't strengthened due to parking, to enlarge columns reduces parking space size or the space altogether, so the HOA technically wasn't allowed due to zoning laws.

...

In addition, they appear to have been overloaded. According to the plans provided, the columns were not designed for the penthouse addition. The column schedule mislabels floor 12 as the penthouse.

If this is true for the South tower, then it may be true for the North tower as well (and maybe the East depending on whether the East tower has an added on penthouse also). You can find the "Typical Floor Plan Dimensions" blueprint for the North tower at page 164 of 336 of the 1979 plans. The "Column Schedule" for the North tower can be found at page 171 of 336 of the 1979 plans. The penthouse is also shown on the column schedule for the North tower to be floor 12. Maybe it was added also.

Given the picture of the lower level garage posted by Engr888 (which Murph9000 says is actually from the East tower), maybe somebody ought to consider evacuating the North (and maybe the East) tower until it (or they) can be shored up. Just a thought.

 

[warrenslo]

missstructures: To me it looked like the column line along the corridor went first due to the light flashes, otherwise the first portion to collapse would have tipped over more rather than fell in on itself. The rebar pattern also makes it appear a middle column failed. Did unit 101 escape into the pool deck, he had direct access. Finally, the pool itself looks undamaged.

Engr1988: is that North or East. East was built in the 1990s.

 

[geotechguy1]

I can't comprehend how the other towers haven't been evacuated

 

[Ingenuity]

I trust it was not constructed like this...maybe it was:

On drawing S-9 (penthouse framing) and S-10 (roof framing) the drawings detail top reinforcing at these column locations.

EDIT: Drawing S-6 (second floor framing) also details top reinforcing at these column locations.

 

[Engr1888]

warrenslo: I think in that video clip it was mentioned East.

 

[rapt]

Concrete strength is 3000psi.

To the current Australian code, since 1988, minimum concrete strength within 1Km of the ocean is 40Mpa (5800psi) because of the exposure to sea spray!

So I would be expecting bad corrosion a long time ago independent of any water leaks.

Typical floor slabs are flat plates, 8" thick spanning a maximum of 22'6", so about 6.9m and it is an end span. I would expect that sort of depth with a properly designed PT slab and 40MPa concrete, not an RC slab.

I do not have the complete drawings and design requirements, but from what I have seen, I would suggest the expected deflection on the typical floors would have been in the order of 100mm (4") if they had been correctly reinforced, and that is doubtful from the details we have so far.

And it would require significant amounts of shear reinforcement for punching shear, which I still do not believe is possible to make effective in an 8" slab and from the drawings I have seen has not been provided.

 

[dik]

I still have difficulty imagining a collapse like the one that happened. About 50 years back, one of my few albatrosses, I was asked to put a price in to determine the cause of excessive deflections on a flat slab roof over a parkade. I didn't get the project, but that's another one. The column arangement was unusual, and I determined that a column had been completely missed during the construction and the slab was 2x approx the span in that area. The structure had been in place for a few years. When I see this catastrophic collapse, I have to shake the sawdust out, to try to vision the cause and am surprised that nothing held it together.

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

-Dik

 

[dik]

With salt de-icing, I use 35MPa min... with added cover. Does the Australian code have minimum cover requirements?

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

-Dik

 

[rapt]

dik,

It has stood up for 40 years with its problems! It normally takes a lot more than one problem for collapse, but punching shear is very unforgiving once it decides to go. Pancake failure!

Yes it has minimum covers, but for that exposure it has minimum 40Mpa strength independent of cover.

 

[dold]

I can't comprehend how the other towers haven't been evacuated

Unbelievable. How would this even be a discussion?

This "40 years" is a completely arbitrary number as far as i'm concerned. What do the 40yr inspection reports of the other Champlain tower(s) say? Assuming they were built within a short time of each other. Or are they also just waiting a cool 2 years to take action on known issues. Critical issues.

Where does the inspecting PE's responsibility end? I.e., I feel like the findings of this report should have been followed up on. The inspection report has a forensic architecture flavor to it, not so much structural.

 

[warrenslo]

IEGeezer: North has a nearly identical penthouse. East was built in the 1990s and does not appear to have a penthouse.

I'm sure every building of that era will be looked at a bit more closely now. I could see even a mass inspection and required retrofit similar to what many jurisdictions in California have recently required.