Miami Beach, Champlain Towers South apartment building collapse, Part 19 27

[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
Miami Beach, Champlain Towers South apartment building collapse, Part 15
Miami Beach, Champlain Towers South apartment building collapse, Part 16
Miami Beach, Champlain Towers South apartment building collapse, Part 17
Miami Beach, Champlain Towers South apartment building collapse, Part 18

 

[dik]

We always put reinforcing over the column area when I was with RJC. I don't recall the percentages anymore for slabs with drop panels (over 40 years back) I think it was 80% and 20% for drops with 80% going in the column strip and 20% over the column. For slabs without drops, there were two other ratios based on the size of the column... a greater percentage for 12" wide columns and a lesser percent for 24" wide columns, adjusted for columns in between...

This was based on work that Per Christoffersen had done with a loaded plastic model and a dial guage to determine curvatures. The model used to be in the Toronto RJC office. RJC used to use these for designing office building slabs.

Forgot to add, I always put a couple of 25M (#8) in the bottom of the slab for narrow columns, to preclude punching shear.

-----*****-----
So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

 

[zebraso]

The structural engineer SHOULD have known. He was also the inspector. He signed off on the rebar placement.

Yeah. So what is the thinking here? It does not seem plausible that it was an error or "mistake". Were there last minute calculations based on some revised load estimates? Seat of the pants to save a few bucks? Anything? I know it's wrong but why was it done this way? I can't believe they missed a note in the drawing. How else would they guess the percentage centered on column in the strip?

 

[spsalso]

"So what is the thinking here?"

My thinking here is that:

The structural engineer never showed up to do the rebar inspection. And that the pour happened anyway.

OR

The structural engineer showed up to do the inspection but did a thoroughly inadequate job.

OR

The structural engineer showed up for the inspection, saw the improperly placed rebar, and did not act on that knowledge.



spsalso

 

[Sym P. le]

I tend to believe it's a casual indifference. None of these actors are yesterdays child.

There is nothing like a true inspection report. "The plans call for a 4" stitch weld every three feet. The welds are only 3.5"." Not many words need to be exchanged as the welder spends another day on the cherry picker.

 

[dik]

From Canadian code:

-FOR INTERMITTENT WELDS, LENGTH SHALL NOT BE LESS THAN THE GREATER OF 4 TIMES THE WELD SIZE OR 40MM (1-1/2”). FOR COMPRESSION MEMBERS, THE MAX CLEAR SPACING BETWEEN WELDS SHALL NOT EXCEED 12”. FOR TENSION MEMBERS, THE MAX CLEAR SPACING BETWEEN WELDS SHALL NOT EXCEED 18” (CSA W59 11.4.13.2).


-----*****-----
So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

 

[Sym P. le]

Sorry dik, that wasn't an exact quote. The incident was real and the solution could not have been easier and it was a long time ago. The point being that if the inspector takes his responsibilities seriously, managing work quality gets easier. Once word gets out that performance is expected, everyone remembers what they're supposed to do.

Thanks for bringing out the code though.

 

[dik]

US code is likely similar... not even close to code compliance. I occasionally review construction, but that would have 'jumped out'. It distresses me that there was no one charged with criminal negligence for all the deaths. I guess it's the way they do things in Florida. The system is broken.

-----*****-----
So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

 

[spsalso]

"It distresses me that there was no one charged with criminal negligence for all the deaths."

Who is still alive who might be charged?

Notably missing, however, is any interest by any governmental authority to examine and make public whether there WAS such negligence.


spsalso

 

[dik]

or businesses associated with it? or those neglecting the upkeep? or the EOR that did the sloppy 'repair'?

-----*****-----
So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

 

[NOLAscience]

I happened to be in Miami this past week. We walked on the beach path and swam in the Atlantic. This is the Champlain Towers site, 28 Jan 2024.

 

[NOLAscience]

Did we ever have the plans for the parking levels and the first floors of the Champlain Towers NORTH? Does it have the "step" that was eliminated in CT South?

 

[Jeff Ostroff]

You should have walked by the Champlain Towers North building also, they changed their name, they are no longer called Champlain Towers.

 

[stcbus]

Did we ever have the plans for the parking levels and the first floors of the Champlain Towers NORTH? Does it have the "step" that was eliminated in CT South?

I do find it strange how there hasn't been any follow up or media information on CTN after they were reportedly shoring up some spots. Nothing about the design, how similar, etc. Probably on purpose to protect property values, just like renaming mentioned above lol. But as someone very interested in the causes and such, I'd love to know these things.

 

[Sym P. le]

They will reinforce their property values by reinforcing the structure with appropriate oversight.

 

[Jeff Ostroff]

STCbus, I live locally here to CTS, I can drive there in 40 minutes. The local news stations did cover the added pole shores in early 2022 when they were first added, and I have already done a video on these added poles at CTN analyzing why they were put in the spots that they chose, and I mentioned it also on my 1-year remembrance video, where I was on site there for the ceremony, and Jill bidden was there along with Ron DeSantis.

Also The local news here 2 years ago mentioned the Champlain Towers East building also added pole shores in their garage and they showed some severely crumbling columns in their garage too.

 

[stcbus]

^ yeah I remember that just was curious because I don’t think the results were ever reported, like what was done permanently and blueprints if it has the same design flaws like mentioned above.

 

[Murph 9000]

See page 217 of 336 in 8777-collins-ave-1979-plans.pdf for the CTN lobby level framing plan. It does not have the double-H of BMAs spanning KLM 9.1-11.1 that I believe doomed the CTS tower from the pool deck collapse. (Note the garage ramp in CTN is the K-L bay, not the L-M bay as in CTS; as the entire east wing is shortened by 2 or 3 structural bays, relative to CTS.) I don't know if that page is the newest one in the public PDF, or how it relates to as-built.

 

[lexpatrie]

I didn't get caught up, here, but has there been any prior discussion of potential backstay effect when it comes to the pool/parking slab?

Backstay Effect, Tocci, Levi, June 2012, Structure Magazine

As a side note, was the backstay effect in common engineering parlance as a phenomenon back in, say, 1978?

 

[Mark R]

So what is the thinking here?"

My thinking here is that:

The structural engineer never showed up to do the rebar inspection. And that the pour happened anyway.
OR
The structural engineer showed up to do the inspection but did a thoroughly inadequate job.
OR
The structural engineer showed up for the inspection, saw the improperly placed rebar, and did not act on that knowledge.

I believe there is at least one more possibility. The structural engineer could've known what was happening but was paid to ignore it!

 

[Sym P. le]

... has there been any prior discussion of potential backstay effect when it comes to the pool/parking slab?

After nineteen pages, I don't recall. It's an interesting topic.

The article seems to focus on grade level and lower diaphragm interactions with the tower system. In the Champlain Towers situation, the evidence is leaning towards design/construction shortcomings of the grade level slab coupled with abuse of same with overloading pool deck renovations triggering its collapse.

I don't recall hearing any investigative avenues regarding the possibility of wind effects pushing the tower against the diaphragm, which would be an inverse cause/effect of backstay.