Miami Beach, Champlain Towers South apartment building collapse, Part 11 54

[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


SF Charlie
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[Santos81]

One thing that’s been a subject of speculation is the UPH Addition and what impact it may have had. I think it’s important to note that there is every indication it was intended to be constructed from the very beginning.

 

[AusG]

Not arguing, but what leads you to that conclusion?

 

[Santos81]

Not arguing, but what leads you to that conclusion?

This specific page:

 

[Vance Wiley]

Could you please elaborate a bit?
Thank you,

 

[Santos81]

Could you please elaborate a bit?

It’s one of the few from the original permit set (identifiable by the ring punches and signatures) but shows only reinforcement detail and minor changes required at that level for the UPH.

Compare to the same page from the “New Penthouse Addition - South” application set that came later (but has the incorrect vertical openings):

FWIW, the north tower has one of these oddball pages as well.

If someone else has a better explanation, all eyes are upon ya.

 

[Reverse_Bias]

Today's Miami Herald article is summarized in a large twitter thread with lots of graphics. It's mostly about the plans in the design not meeting code. All the columns in the portion that collapse had "overcrowding" issues.

https://twitter.com/MiamiHerald/status/1424386712248143876

 

[CE3527]

One thing that’s been a subject of speculation is the UPH Addition and what impact it may have had. I think it’s important to note that there is every indication it was intended to be constructed from the very beginning.

Not that I think this was part of the cause, but it's been reported that the Town stopped the construction at one point because the developer didn't have permission to build the penthouse, and it violated local ordinances (which were later changed to appease the developer). From Wall Street Journal:

"The developers of the collapsed Surfside condominium tower worked around local building codes by adding a penthouse that wasn’t part of the original plan, a review of town building records shows.

Plans submitted by the developer of the Champlain Towers South initially called for 12 floors of residential units. The developer decided to add a penthouse, which increased the building’s height by about 9 feet with an additional floor. That put the tower slightly above the town’s legal height ordinance at the time."

 

[Santos81]

but it's been reported that the Town stopped the construction at one point because the developer didn't have permission to build the penthouse, and it violated local ordinances (which were later changed to appease the developer)

Revoked the permit briefly so that could be “fixed”

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I put it up there with the “3.9 earthquake/aftershock” that:

Wasn’t an actual earthquake

Occurred more than 300mi NNE of Miami; further away than the actual very active seismic area to the south (yes we felt that 7.7 and the 6.8, 6.5, and 6.1 aftershocks)

Didn’t even register on the seismometers in Doral that are used to monitor the quarry blasting, such as on the evening of June 23. This has already been ruled out as a contributing factor after monitoring the site during last months blasting.

 

[arbitraria]

Thanks @Optical98 for posting the link to the article from the Israeli team, very interesting and respectful read.

This part is sticking with me: "We locate Ilan and Deborah in Apartment 811, as we expected. They lie side by side, embraced, holding their ID cards. Perhaps they felt the tremor." It's a fascinating and heartbreaking detail, obviously they knew that building was coming down and they weren't making it out. I thought maybe they were older so they didn't have the physical capability to try to escape, but they were only 21...they had enough awareness of the situation to understand what was happening, enough time to gather their identification and go to a specific spot to fall together. I have to think that something prevented them from trying to escape.

Being in the x11 stack, we know those units sustained damage prior to the collapse...after watching the video from 711, I wonder if the front door to 811 was compressed by the failure that woke up the camera one story below them? Ms. Monteagudo in 611 described the crack she saw forming as coming from above, perhaps every unit in the stack above her was unable to open their doors, as there's never been mention of anyone being found in a hallway attempting to escape.

As though the imagery of those final moments wasn't horrific enough already...

 

[Optical98]

arbitraria,

Yes, I noted that as well.. the only thing I could think of is if we consider the 904 survivor details that seem to indicate that some of the top floors dropped 1st, to the 8th and maybe just to the west end ( x4 and x10), that could have blocked 811's exit.

"Sara Nir was up late, checking her email when she heard knocking sounds that went from a soft tapping to hard pounding to a frightful crash overhead -- as if a wall had collapsed in the unit above her ground-floor condo. 

Raysa Rodriguez was sleeping in her room on the ninth floor when she awoke disoriented. The building was swaying "like a sheet of paper." She ran into the hallway to find that it had been impaled from floor to ceiling by a concrete pillar; the doors of the elevators were shorn off, exposing the shafts."

^From this article -

https://www.cnn.com/2021/07/03/us/surfside-condo-collapse-questions-unanswered-invs/index.html

Nir is describing something tipping (knock knock knock) and falling over.
And how did a column "impale" the hallway on west side of the shear wall? 

"Metallic boom" was heard and Furman thought something hit the elevators as well.

It's amazing Monteagudo (611) escaped. You'd have to think she must have already gotten to the stairwell while Nir was in the Lobby.

 

[Jedidad]

Here's a PDF that goes into a little more detail than the Miami Herald tweets: Link
Also uploading it.

 

[tmwaits1]

Interesting observations in this article but again so called structural engineers making statements that are incorrect. Specifically, the statement, which has been repeated numerous times, that if there was something incorrect in the original design then it would have shown up soon after construction. I cannot stress how wrong this statement is. First off you only have to look at the I35W bridge collapse for an unambiguous example of how a design flaw can lie hidden for decades. In the case of I35W, the gusset plate thickness was half of what it was supposed to be. 100% original design flaw which took 30 or 40 years to cause collapse. This happens largely because the structure is designed for both dead load and a live load (lets ignore wind and other effects for now) that it may not see for decades. This means the structure has capacity to carry a certain amount of live load. Deterioration over time, if left unchecked, will naturally reduce this live load capacity down to a critical level, and if that capacity was already low due to a design flaw, then you will reach a point where it only takes a tiny overload condition.

Its also interesting that they made a statement about the bottom cover on the plaza slab being too small. The conventional wisdom is that this is, strictly speaking, a durability and not a structural capacity problem. Videos of the underside of the parking garage by the prospective buyer certainly showed some water issues but didn't seem to show any serious concrete spalling that would be indicative of inadequate cover and subsequent rebar corrosion that would have reduced the load carrying capacity. If the investigation concludes that the plaza deck concrete and rebar weren't significantly deteriorated to the point where collapse was imminent, then the design methodology for these column supported slabs will need to be revisited.

 

[Optical98]

Question for the SEs, just looking at the facts at hand. Knowing there are many condo buildings along that shore in similar build and age.

What issue would you want to correct first?
I mean in hindsight, it certainly looks like the garage should have been shored up immediately, even if it wasn't the 1st project. It was part of the recert plan, but evidently not prioritized.

 

[Demented]

@Optical98
It actually was a priority. A delay in alternate parking just put it on pause.

Precision guess work based on information provided by those of questionable knowledge

 

[Red Corona]

Some interesting snippets in those articles, thanks for posting.

@tmwaits1 Yes, absolutely a structure doesn't need to collapse immediately to have a design or build time flaw, the original design is supposed to have a large safety margin to deal with deterioration over the design lifetime and variations of use, you can screw that up pretty badly and it will still hold up on day 1 with favourable conditions.

Those columns, just from looking at them as a layman, always looked unreasonably thin. (There's a 4 storey building in my town and it has bigger columns than that.) We'd all seen the photos showing not enough rebar, but the points in there about being too small to hold all the rebar at a safe interval sort of explains how that decision might have got made. I don't know how we can think that CT North is safe though in that case - I know there are differences in the slab design around the maybe crucial 9.1 line slab step, but CTN has thin columns and quite likely missing rebar too.

Re @Markbob2 - I'm still not convinced by his interpretations of those images*, but trying to look into the area of the first known collapse in the morning after pictures and see what's down there seems quite a legitimate line of enquiry that doesn't deserve the ridicule he was getting at the bottom of thread 10. There's still no good mechanism proposed afaik for why the pool deck failed, or for the noises in higher parts of the building before that.

* in particular I don't see how that green bag of tar paper could have fallen some 10m beyond the perimeter of the building, nor do I see how a heavy AC or crane+davits on the 1210 roof could have fallen down in front of 111 and the Nirs not reported that

 

[Optical98]

MaudSTL,

You're now famous >>

https://www.youtube.com/watch?v=9Hd2U8ELJpY

 

[tmwaits1]

In my experience this problem starts with the original plans, which were sloppy and never should have been approved for construction. This tells me there was insufficient oversight from the local building department. This is a major problem in Florida at both state and local levels and is a consequence of the average citizen's ignorance of the effective role of government in this process and the value of well paid qualified government staff. Low taxes = low salaries which means you will not have qualified people reviewing building plans. If you want to connect the FIU Pedestrian bridge collapse and Surfside this is your common factor. The FIU bridge collapse happened in part because FDOT has been scaling back real engineering oversight for many years (to reduce costs to the taxpayers) so there was nobody to stop the project even when the signs of imminent failure were obvious.

 

[spsalso]

You're forgetting about permit fees, which should be paying for the "oversight". Isn't that the reason there ARE permit fees?

Possibly "they" gave the developer a big break on those fees, and thus didn't have enough money to cover the costs for doing their job right. One could ask why "they" would do such a thing.

spsalso

 

[Vance Wiley]

Both drawings are titled SECOND FLOOR FRRAMING PLAN.
So they changed the Second Floor in order to add a penthouse? Probably due to added wind exposure so more drift moments in the slab and columns at the second floor level. The shears and moments for the slabs and columns are increased by one floor due to the addition at the top. Originally the First Floor slab and columns had similar moments because they were an equal distance ( same number of floors) from the top. And the First Floor slab was thicker, as I recall.
The columns have more vertical load and more bending if the penthouse is added. Were they increased in capacity as a result of the PH add?