Miami Beach, Champlain Towers South apartment building collapse, Part 04 49

[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

SF Charlie
Eng-Tips.com Forum Policies

 

[SFCharlie]

9 inch slump? Really? Unbelievable!

For us dummies, Could we have a very brief explanation of "slump" Is more inches sloppier?

Concrete Slump Test - Tutorial (for dummies)

 

[1503-44]

More slump is easier to place, since it flows easily to all corners of a slab. 9" is almost self-leveling stuff. But more water decreases compressive strength and increases shrinkage.

Jezzz! Didn't see the 'nother 3 gal.
According to USDA (PDF)
1 gal added per year. = -200 psi f'[sub]c[/sub]
So thats f'[sub]c[/sub] -500 to -600psi less.
So it must have been something slightly stronger than compact baby powder.
Is that the reason why the bars zipped out so clean?
Most look like a skinned squid.

The date is '02, so maybe only used for repair work or pressure injection?
Edit.[and its 3 gal added to the 9yd load, so not so bad as I thought.]

 

[RWW0002]

I could be mistaken but the 3 gallons added is likely for the full truck (9 CY) so 1/3 Gal/CY. The USDA doc you reference is referring to strength loss due to a gallon of water added per yard.

We all cringe with water added on site, but I highly doubt that this particular 3 gallons added to repair concrete in 2002 has much of an impact on anything of significance.

 

[1503-44]

Yes, you are probably correct. ... Hopefully so. Sorry I panicked just looking at that.

Are there any concrete tickets remaining from the 80's? Long shot...

 

[Santos81]

Column Line I does not have this beam tie to patio deck

Those are not the correct plans for anything resembling as-built as far back as ‘81.

Surfside did not have electronic Building Dept Archives which has resulted in very confusing and out of order plan sets after scanning and uploading what has been found in storage for FOIA requests.

Several had asked about saving evidence from the office before the remaining portion was demo’d without understanding the interior lobby slab had also collapsed into the basement in that area.

 

[jbourne8]

One thing that seems a bit strange in that video is the water pipe near the garage entrance:

Here's another shot of it when she pans to the left:

This is the same pipe that's broken in the tiktok video:

I always figured that it broke because it turned towards the pool at that spot, but it's clear that it doesn't. Instead this seems to point towards a failure near this circle before the video started:

I think this might indicate that the tiktok video and the ring video were taken at the exact same time. I always assumed the tiktok video was a few minutes earlier, but this does line up well with how the kitchen dividing wall is leaning in the ring video. Perhaps there were already multiple columns under the building that were collapsed when she started taking the video.

 

[MikeJ65]

Thermopile:

A technicality, but I believe that the beam in the picture is actually column line M (M10-M11), but that doesn't change anything. Note that there is an 11" floor drop in the middle of that beam, making a step in the beam. To make matters worse, they plunked down a very large planter right at the step.

Also note the complex geometry on column M10. The SW quadrant floor is patio height (12'9"), the SE quadrant is pool deck height (11'10"), and the north half is lobby level (13'4"). I'm not saying that this is unacceptable, but it would cause some head scratching on framing and bar placement and there is insufficient detail on the drawings to define how it should be done. Given the ease with which the columns in the pool area punch sheared through, I don't have a great deal of confidence on the floor attachments in this complex area.

As you pointed out, the bottom of the lobby and patio level floors look good, but you can draw a line where the patio ends and the planters start. It would be expected to have a small amount of sag at the center of that beam and the floor step would insure that any leaks through the waterproofing would collect along that step line.

The floor drops, beams, and planters south of column line 10 and K-M form a very rigid box structure supported by the line 10 columns to the north. Note that the NW corner of this structure is K10 which corresponds to parking spot 78. If there was a pool deck failure between lines 10 and 11 (possibly at the slab step), this structure could put a huge moment on columns K10, L10, and M10 and may have inflicted the fatal damage. The columns held for a few minutes, finally gave way, and the rest was a foregone conclusion.

 

[gonefishing2]

[/Those are not the correct plans for anything resembling as-built as far back as ‘81.]

Santos81, I agree Sheet 5 of the Structural Plans I posted above is from the Surfside archives and is a 1979-80 Vintage Design Drawing. I would think 'As-Built' Drawings are just mark-ups of the Design Drawings to reflect changes back in 1981, as plans were paper back then on job sites, and not digital.

I can't image a builder deleting or adding concrete columns or beams in his as built, without consulting the design engineer. However, what they have uncovered so far, says this builder/developer may have been making lots of changes without getting approval from the EOR. So who knows what as built would really look like on this project, and now most of the evidence is gone.

My only point was comparing design drawings to the video from 2020, you can clearly see the Beam between column 27 and 28, which is consistent with the 1979/80 design drawing I posted. Thus, in this case as built looks a lot like the design drewing.

Point of my post was the building is tied firmly to the planter deck area, so any deterioration of the planter area is not isolated structurally from the building, thus failure of deck causes progressive failure of building.

This looks like a terrible idea to not have isolation joint between building and elevated patio deck.

 

[Teguci]

So let's look at some numbers if we assume the Tik Tok column is collapsed.

Column at L/10 - the yellow painted column adjacent to the presumed failed column in the Tik Tok video - is a 16"x16" column with 8-#11 at the basement level. Rough numbers assuming 50% live load, it was carrying 640k. The 9 1/2" plaza slab frames into it with hooked #5 at 12". Assuming yielding of the slab (moment = 11.6 ft-k / ft) for the full tributary width of that column puts 240 ft-k of added moment to that column. Much of that moment would redistribute into the Lobby slab (only a 7" elevation difference). Column interaction diagram gives us a Phi Pn = 640 k with a phi Mn = 240 ft-k. While redistributing moment into the lobby slab will remove some moment, it will also increase axial load to the column from the lobby floor (maybe 15k). Another nearby point on the interaction diagram is 710 k, 220 ft-k. So this is close, but still under the limits of that column.

The collapsed column would get the building column close to failure but not necessarily exceed the column capacity immediately. This allows for the progression of failures to occur as provided by witnesses. I'm still resistant because a vehicle impact on a 12x16 reinforced column (beam connected)supporting 30,000 lbs of weight would not impart enough energy to really even be noticed by that column. To me, the failure is from something else.

Would love to see what the chloride content is in the top of that plaza slab, but even that is probably well localized to the leaks in the plaza membrane (there is a membrane right?)

 

[Murph 9000]

Seems like this strong tie between building perimeter and patio deck would tug even harder on the building once the patio end collapsed? Tug harder than if just flat slab in that area.

Tug harder, or damage more of the column's rebar cage as it detaches, or hold onto the column for longer and act as a giant rigid & heavy lever applying torque. It seems guaranteed to have some sort of larger influence on the attached columns than the basic slab, especially in failure scenarios, none of it good for the capacity of the columns.

 

[gonefishing2]

MikeJ65 thanks for your correction of my Column line error, and especially for your further explanation of the asymmetric moments and shear loads on those columns.

 

[Pud]

I've read all parts of this thread with fascination. Not being structural or civil I would ask what may be a dumb question:

What was the design life of this building? If it was 30 years then a good job was done. If it was 100 years then maybe not so good.

What determines end-of-life, everyone out and its taken down?

Cheers


Politicians like to panic, they need activity. It is their substitute for achievement.

 

[GPR_Tech]

Can anyone comment on drawing S.5 of 14 showing:
[Pool side of the BLD that collapsed]
UPDATE-
1.) Basement Column line 9.1 (offset 8") from the grade level of building Column line 10
. (answer for offset of 8" is because it is not the center line of the column but the outside edge of the column)

2.) Change in slab Elevation along/near column 9.1
. (this may or may not have been a contributing cause of the collapse)

3.) No Beam (BM-A) under at column I / 10
. (answer is because change in slab elevation is within the column)

Sections taken from S.5 (Pg. 31 of 336)

https://www.townofsurfsidefl.gov/do...-collins-ave-1979-plans.pdf?sfvrsn=bd2a1194_3

.

 

[MikeJ65]

GPR, 1) There is not really an offset. 9.1 is column CL, 10 is outside line of building. 2) Pool deck is 18" below lobby level. 3)BM A is required at column lines K-M because there is a slab step mid slap between 10 and 11. Column line I steps down the full 18" on line 10, so beams would not be required.

 

[DavPc]

Jbourne8,

My old eyes see what seems to be a slight pitch downward in that large, white pipe. Even if there is no slope, it looks more like a PVC drainpipe of some sort rather than a pressurized water line.

The south-pointing spray direction of the water in the TikTok video says to me it is one of those red fire sprinkler water lines that broke, perhaps the one on the right side above the ramp in your first attached image. If so, I am still perplexed why the fire alarm didn't sound, which could have saved many more lives. Instead we had a few residents (and even the security guard) wondering what all the loud noises were and everyone else remained unaware anything was happening.

On a slighltly related note, that garage video once again confirms what was reported in 2018 - the exposed sections of the concrete deck lacked sufficient waterproofing and were moist enough to cause the paint to peel off.

 

[Penagwin]

I'm not sure if it was mentioned yet but I wanted to add this because I just found it. It's their minutes report from their October 2020 meeting. It looks like they did exploratory demolitions and there's some photos in there.
This appears to be where the "curious results" is from.

This initial work yielded
some curious results as it pertained to the structural slab’s depth, and MC requested that additional core work be
performed by CPR to confirm/clear-up said results. CPR performed 6 separate cores at the direction of MC. The
results of exploratory demolition and the additional core work are summarized in the attached “CTS Test Probe
Notes” file.

Direct link:

https://s3.documentcloud.org/documents/20985354/20201014bodminutesapproved.pdf

Source:

https://www.npr.org/sections/live-u...-deterioration-before-surfside-condo-collapse

 

[Spartan5]

Regarding the broken water line in the intermediate collapse video into the garage… wouldn’t there be much more flow from this line if it were a broken main or fire suppression line?

 

[GPR_Tech]

Did they really have to cut right through the Rebar?
and then how did they, after coring through the Rebar restored each exploratory (and core) location back to its original
condition?
Pg 39 of 83 "At completion of the investigative work CPR restored each exploratory (and core) location back to its original
condition"

https://s3.documentcloud.org/documents/20985354/20201014bodminutesapproved.pdf

.

 

[Santos81]

Santos81, I agree Sheet 5 of the Structural Plans I posted above is from the Surfside archives and is a 1979-80 Vintage Design Drawing. I would think 'As-Built' Drawings are just mark-ups of the Design Drawings to reflect changes back in 1981, as plans were paper back then on job sites, and not digital.

I can't image a builder deleting or adding concrete columns or beams in his as built, without consulting the design engineer. However, what they have uncovered so far, says this builder/developer may have been making lots of changes without getting approval from the EOR. So who knows what as built would really look like on this project, and now most of the evidence is gone.

My only point was comparing design drawings to the video from 2020, you can clearly see the Beam between column 27 and 28, which is consistent with the 1979/80 design drawing I posted. Thus, in this case as built looks a lot like the design drewing.

Point of my post was the building is tied firmly to the planter deck area, so any deterioration of the planter area is not isolated structurally from the building, thus failure of deck causes progressive failure of building.

This looks like a terrible idea to not have isolation joint between building and elevated patio deck.

It would have been helpful if a complete permit set was maintained. Perhaps then, if those had existed, this may never have happened. After the first penthouse revision and second upper penthouse addition, none of the work from that point required as-built plans for the full building.

Those core samples should have been an immediate cause for shoring up the slab. There’s way too much structural steel for it not to be obvious something was off.

 

[Santos81]

Did they really have to cut right through the Rebar?

Take a very close look at Core A.