Miami Beach, Champlain Towers South apartment building collapse, Part 15 32

[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
Miami Beach, Champlain Towers South apartment building collapse, Part 09
Miami Beach, Champlain Towers South apartment building collapse, Part 10
Miami Beach, Champlain Towers South apartment building collapse, Part 11
Miami Beach, Champlain Towers South apartment building collapse, Part 12
Miami Beach, Champlain Towers South apartment building collapse, Part 13
Miami Beach, Champlain Towers South apartment building collapse, Part 14

SF Charlie
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[Sym P. le]

Some more on cracked columns from the litigation and garage video:

The unknown location may be south face Column 76 (across the lane from 28) given the faded paint stripe on the floor (and carefully watching the garage video).

Edit: I've changed my mind about Column 76 but what looks like a faded paint stripe on the floor to the right of the column may be a clue:

 

[FJBnomics]

I wonder if some of the horizontal cracks in columns are areas where columns were previously repaired?

The aux deck drain line to garage floor is classic of the lack of a designed in or maintained drainage system for patio deck, and what appears to be lack of storm water run off drainage system all together.

The aux drain serves only to keep caustic liquid from draining onto people or parked autos.

 

[IanCA]

Thanks thermopile, NukeDude948, SwinnyGG.

From the pictures I have seen and the drawings it is not clear whether the patio deck slab pour is capping off the perimeter wall and the bulkhead or did the deck slab stop short of capping off the concreted filled corrugations between the bulkhead and 8" wall shown on plans?

That is correct. Also the drawings show piles on 12 foot centers supporting that slab around the entire perimeter to handle the load. Page 307 of 336 from the big set of drawings or page S1.

When you look at the entire sheet, the pile layout is crystal clear. It's simple, really. Piles are spaced 5'0" or 6'0" from the slab edge. The slab had a thickened edge per the detail shown earlier in the thread, 8' wide. There are no columns above this ring of perimeter piles; the thickened edge of the slab is carrying load which has been transferred down from the grade level slab, through the retaining wall which bears on the thickened slab edge.

There is a good image by Robert Lisman in the Miami Herald Article "Did drilling next door damage Surfside tower? Newly surfaced vibration data offer clues" here:

https://amp.miamiherald.com/article255411881.html

archived here:

https://archive.fo/22xyO

Using that image and others, it is possible to estimate the dimensions of the deck at the wall as shown below:
Yes, there is clearly concrete on both sides of the sheet pile in the areas where it is exposed.
But, even though the sheet pile was capped off the protection against salt water ingress would be lost as soon as the slab cracked horizontally.

The following are cropped from that image:
Notice in this section the deck has shared off:

This image shows the deck concrete between the sheet pile and the privacy wall above:

Here the deck has been fully retracted from between the top of the perimeter wall (basement garage wall) and the 4 foot exterior wall of the planter.

Clearly there was a horizontal crack between the top of the wall and the bottom of the deck.

I believe it is possible to show that the collapse of the deck started along this connection between the parking deck and the southern wall and I can explain why the concrete in that area was in such bad condition.

 

[FJBnomics]

Wow IanCA you nailed it! You put together the as-built issues with the way they capped the sheet pile and that structural wall, and how water easily gets into space between sheet piles and concrete wall and via the corrugate fill.

This was the questions I had about southern wall and water intrusion and this clearly shows water intrusion was NOT a trivial issue at southern wall.

Edit: Last picture shows directly under planter at wall. It will take some time to fully absorb all the information presented.

 

[SwinnyGG]

@IanCA great post.

Raises some questions for me.

My own private working assumption had been that the initiator for the building failure was failure of the pool deck slab near the building, which put a horizontal load into the columns and 1st floor building deck (the garage ceiling/lobby floor) which they could not handle. I've also been operating on the assumption that the pool deck itself was not structurally critical to the stability of the building; in other words, I've been assuming this whole time that if you sawcut the pool deck level slab out and removed it right up to the edge of the building, without damaging anything of course, that the building itself would remain structurally stable. That may not be the case.

From IanCA's post, it's clear there was relatively severe degradation of the slab connection to the perimeter retaining wall. Is the failure of that connection enough to create a cascade all the way from the perimeter wall to the columns which ring the first floor deck of the building, in which case the catenary action of the pool deck slab created a horizontal load on the perimeter columns and 'ripped' them down? Or did the removal of the pool deck itself from the foundation system reduce the stability of the first floor lab below a safe level, even if that slab failed without putting significant horizontal load into the columns at the building side?

 

[spsalso]

If there was severe water damage at the intersection exposed in the photo, would it be evident in the exposed concrete? How--is it something visible, or perhaps "tactile"?

I assume the rebar would show evidence of extreme corrosion right around the break. A close examination of those would be interesting. Would there be rust staining around the rebar?



spsalso

 

[Sym P. le]

The images posted by Ian were not in the immediate aftermath of the collapse. I agree that the lobby car park is a candidate for the trigger location but I would not read much into those photos as evidence (EDIT: of slab edge condition).

Note the screen erected along the walkway:

Various stills from two body cam vids (posted in no particular order) indicate a significant gap under the privacy wall where the slab pulled away.

Further west where the slab did not pull away and is not fractured. The slab edge is formed closer to the property line than I previously considered and the finish level of the sidewalk was likely several inches higher than the gravel strip.

Thermopile, what you indicate as a cold joint is not. It is a joint line in the form work.

 

[FJBnomics]

Sym P. le, I can agree that cold joint looking horizontal line is just a formwork line. Since it has been painted it makes it even harder to tell.

I am posting 2 images below. Can you tell if these unpainted joints are:

A Cold Joints

B Formwork Joints

C All of the above.

 

[SwinnyGG]

Both look like form lines to me. The bottom is a form line 100%. The top one is less certain, but only slightly so.

Cold joints are never laser-straight. When you pour a joint with a cold joint in it on purpose, the cold joint is not tooled and finished, so the resulting bond line is not perfectly straight. It will be roughly straight, but there will be obvious jogs in it approximately the size of the aggregate, because the joint has not been tooled to drive the cream to the top surface and hide the ag.

When you pour something and there's an unintentional cold joint in it, the result is very, very obvious. Neither of those are an 'accidental' cold joint.

 

[Sym P. le]

I am posting 2 images below. Can you tell if these unpainted joints are:

A Cold Joints

B Formwork Joints

C All of the above.

Context would be helpful. I see a joint between the two images.

 

[FJBnomics]

SwinninGG, You are correct bottom joint in second image is only a B.

Now the upper line in the first image is a C.

The joint in the middle is the break point between the way the web site displayed the 2 images.

Sym P. le, My context is it very hard to tell the difference from the images we are analyzing. I know the history of these joints because I was the engineer and builder on this home project. In person, the difference is more obvious to the trained eye 👁

 

[FJBnomics]

I believe it is possible to show that the collapse of the deck started along this connection between the parking deck and the southern wall and I can explain why the concrete in that area was in such bad condition.

IanCA, are you saying the roots of the shrubs in the planters had grown into the concrete structural slab below and broken it up into gravel over time?

In your first image showing the sheared of slab area, I can see the step in the driveway slab thickness vs the patio deck thickness.

Edit: I also like your theory that roots would break some of the masonry units below the concrete sideway on 87 Park Side, prior to removal of concrete curb/slab at 87 Terrace. So some of block damage could have been pre-existing condition under concrete cap.

 

[MaudSTL]

The NYT interviews Surfside Building Inspector Jim McGuiness and others in The Towers and the Ticking Clock, which is focused on the impact of the CTS collapse on the Florida condo market.

Here’s a link to the archived version.

 

[AusG]

I could see Mayor Burkett being played by Clifton James in the movie, except he's no longer with us

 

[IanCA]

are you saying the roots of the shrubs in the planters had grown into the concrete structural slab below and broken it up into gravel over time?

No, sorry, I was rather vague there. It is highly likely that the roots of the palm trees, previously located in the planter at the southern wall, caused cracks in the block walls of the planters and we know the waterproofing within the planters had previously failed, been repaired and failed again, in part from the Morabito report. The gravel comes from the beach path that was previously 87 terrace and was placed there during the development of 87 Park.

Here are my arguments for the failure of the slab initiating at the southern wall:

1) Very simplistically, think Ockhams razor, we can clearly see from the CCTV video shot from 87 Park that the collapse of the building progresses from the south to the north, therefore elements of the structure that are further to the south likely collapsed earlier and the location furthest south on the property would be the earliest and would be the connection of the deck at the southern property line wall. This also agrees with the witness statements suggesting the sequence was parking deck, pool deck, building.

Before the next point, let me say first that I very much appreciate Mike Bell's contribution to understanding this event and the skill and determination exhibited by Mike and his team in producing their animated videos. I believe that the rotation of the 1' 6" drop slab at the south of the building he depicts is very close to actual failure dynamics. Mike and I have discussed aspects of the collapse, but we didn't reach an agreement.

2) An initial collapse of a single column punching through, as proposed by many, including Mike Bell, has several geometric characteristics that reduce the probability of a progressive failure. Firstly, ignoring construction joints, an individual column is surrounded by 8 other columns. I suspect this means that the increase in vertical load on the adjacent columns may be as little as 12.5%. The deflection of the deck would require the deck to stretch in two dimensions (even in poor condition that deck was not very stretchy) to form a depression at the point of failure and the increased stress on the adjacent columns would be substantially lateral, horizontal, and each adjacent column would be backed up by several other columns beyond them. Consider a heavy object in the middle of a trampoline, the vertical load is translated predominantly into a lateral load shared by the horizontal springs who's deflection is mostly radial not vertical. Secondly, If a single column punches through, the geometry of the failure progression will tend to be concentric, radiating out from the first column. If that point is close to the building, then only a small region of the front involved in the collapse will initially reach the southern facade of the building and the bending moments or rotational torque on the 1' 6" drop slab will be relatively low and limited in area and in addition the debris from the parking and pool deck do not appear to exhibit signs of concentric failure.

3) If the initial failure begins at the southern wall, by the deck detaching from the wall, and encompasses the area occupied by the 8 vehicles, bounded on the east and west by construction joints or weaknesses running from south to north, then I believe it is possible to consider the approximate loads on the deck and column I14.1 at the south-east corner of the western portion of the building that remained standing as shown in the diagrams below.

4) If column I14.1 punches through the deck the load is transferred to column I14 but at a greater distance from the column and with an additional 23 feet of deck weight added. If column I14 punches through the load is further increased and transferred to column I12.1 The progression is linear towards the building and the progressive increase in weight allows a progressively larger area of the deck to be engulfed.

5) The possibility of a linear progression is reinforced by the deck failure line that runs east west through the parking deck gate.

I'm interested to hear whether that sounds feasible, whether it matches the evidence that was visible in the debris and the sequence of events.

 

[IanCA]

The images posted by Ian were not in the immediate aftermath of the collapse. I agree that the lobby car park is a candidate for the trigger location but I would not read much into those photos as evidence of slab edge condition.

Thank you for your input and the body cam images, they are helpful and clearly show the gap left when the deck detached. I will look for some other examples of the edge condition soon after the collapse, but I don't feel as though the condition of the wall changed much from the time of the collapse to when the photo I referenced was taken. It is still in virtually the same condition now, apart from where the west portion of the building fell during the demolition.

 

[IanCA]

this clearly shows water intrusion was NOT a trivial issue at southern wall

Thanks for your comments and I agree with your points about the water [chlorine, salt, and organic compound] intrusion.

in which case the catenary action of the pool deck slab created a horizontal load on the perimeter columns

Thanks very much. I believe that is true but the load is not entirely horizontal it is also rotating the drop slab and column connection. As the collapse progresses north the deck is impaled on an increasing number of columns so the required change in length could really only be accommodated by changing the geometry of the 1' 6" drop slab and column connection.

 

[FJBnomics]

I'm interested to hear whether that sounds feasible, whether it matches the evidence that was visible in the debris and the sequence of events.

IanCA, Another Excellent post. Early on there were folks talking about parking deck and the many hours, days, months-and years of cyclic loading of that parking deck and how that was a very stressed area. Also there was discussion of cracks and possible damaging repair solutions.



North Tower gets temporary shoring

https://www.kansas.com/news/business/article257966283.html

EDIT 2: I just watched some of Mike Bell's Animations that IanCA mentioned. Here is link to part 3, which is very interesting to me.

https://youtu.be/WdkdIUdJLEk

 

[MaudSTL]

…witness statements suggesting the sequence was parking deck, pool deck, building.

There are no witness statements supporting a deck collapse sequence. No surviving witness actually saw the deck collapse. All the surviving witnesses who saw the deck after it collapsed only saw the parking deck, either from inside the lobby or from the porte cochere as they escaped and ran to the street.

The first survivor to see the deck after it collapsed was Sara Nir of 111, who was in the lobby at the time, talking to Shamoka Furman the security guard about the loud crash they had heard at 1:10 AM. When they heard and felt the deck collapse at about 1:15 AM, Sara ran over to the lobby window next to the parking deck and saw that it had collapsed. The MH House of Cards infographic does a good job of depicting the view from the lobby window. It shows that that in the dust and darkness there was no way to see beyond the parking deck from the lobby.

Sara assumed there had been an earthquake, and ran from the lobby down the hallway to 111 to evacuate her kids. Gabe Nir of 111 was in the kitchen cooking salmon when the deck collapsed and dust started rolling in through the open patio doors. As the building rumbled and swayed, he ran to the bathroom door to roust his sister Chani, who had just taken a shower. They both made it to the apartment door by the time Sara got back to them, and all three ran back to the lobby.

While Sara was coaching Shamoka on what to say to 911, the Vazquezes exited the elevator (where they had experienced the collapse) and were met with panic and clouds of dust. They had no idea what had happened until they ran outside and saw the collapsed parking deck as they escaped. Gabe ran outside to the porte cochere and only then saw that the deck had collapsed. He ran back inside to roust his mother and sister, and then they ran across the street and up the block before the building collapsed.

Shamoka remained at the security desk, calling 911, fielding calls from residents, and telling them to get out.

According to her husband, the late Cassie Stratton of 410 was awakened by the building shaking rather than by the deck collapse. When she got up and went to the balcony, she saw that the pool deck had collapsed and water was pouring out of pipes. Mike Stratton says she called him at 1:20 AM, fully five minutes after the deck had collapsed.

>>>>>Edit: None of the surviving witnesses, including the Nirs, Vazquezes, and Shamoka Furman, talk about hearing or feeling a multi-stage deck collapse sequence. Ileana Monteagudo of 611 said she was awoken by a “supernatural force.” Adriana Sarmiento, who shot the garage ramp video at 1:18 AM, said they heard a loud crash and felt the air pressure forced out of the garage.

 

[AutisticBez]

I agree with the failure starting at the south wall. I mean, it makes sense. It also occurred with a car parked above it right? To me it makes sense that the weakest point on the south wall is where the planters and car are. And moving to the north from there we have the design flaw caused by the change made in deck height and elimination of the beams that would have been under the planters. This progresses towards the building to the north and failure occurring at planters outside 111.

Cantilever of the beams / drop slab at planters. Enough damage has been done.

So then what was the solution? Expansion joints dividing building from outside deck? Those parking garages are a real problem. Nobody ever considers a parking deck to be a structural risk. Why on earth would you run a beam from a building column to hold up a planter box? Nobody ever thought this would be a problem?