Miami Beach, Champlain Towers South apartment building collapse, Part 17 14

[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


SF Charlie
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[SFCharlie]

I think that, since there was no sand nor pavers between the planter and the deck that any downward displacement of the planters required a failure of the deck, even if it hadn't fallen yet.

SF Charlie
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[IanCA]

Since someone already mentioned the fire sprinkler system was likely damaged at that location, I checked to see what was there.

Thanks very much for taking the time to research that aspect and provide that perspective. I will give that some more thought. I'm interested to see which way the pipes ran and where they would likely have broken and at what time in the sequence and whether the deck shielded the wall.

I'm going to "stick" to the water theory.

Water off a duck's back?

 

[MaudSTL]

I thought that Maud had stated that the witnesses saw the whole deck collapse at one time? I could be confused.

No surviving witness actually saw the deck as it collapsed at about 1:15. But multiple survivors heard it collapse, and to all of them it sounded like a single loud event, whether they were in the lobby, the elevator, 111, or by the pool at the Blue Green Resort across the street.

The first survivor we know of who saw (after the fact) that the deck had collapsed was Sarah Nir, followed by Shamoka Furman, in the lobby. Since they were looking at the collapsed parking deck and the clouds of dust in the dark, I have always doubted that they could have seen beyond the collapsed parking deck to the collapsed pool deck. This theory is born out by the fact that all of the surviving witnesses who saw the collapsed deck from the lobby and/or porte-cochere described seeing (and hearing) the cars jutting out. None of them talked about seeing that the area beyond the parking deck had collapsed.

We know second-hand that the shaking building woke the late Cassie Stratton in 410. She did not see the deck as it collapsed…she saw it after it had collapsed, and then called her husband at 1:20.

 

[Jeff Ostroff]

In seeing all these theories on how the pool deck separated from the south wall, 2 things still bother me.

1) I still don't see how that planter next to the wall could have caused the pool deck to break apart there and pull away from the wall, it is too close to the wall, and so any rotational or moment arm forces would not likely have enough strength to pull it from the wall. Tha area was never mentioned as a problem area prior to the collapse, unlike column 76, which had water leaking down from the pool deck.

2) IF the slab separated from the south wall with cars on it, why did they fall back into the V-shape at the center of the slab (driving lane of the covered parking deck), instead of cars falling forward toward the south wall since the slab separated from the wall?

This is why I think the punching shear initiated somewhere north of that first line of cars near the south wall, causing them to fall back into the V. This would then cause the slab to detach from the south wall. SO I am looking at that detachment of the pool deck slab from the south wall as a result of the pool deck punching elsewhere, instead of the south wall separation being the cause, it is the result.

 

[IanCA]

But multiple survivors heard it collapse, and to all of them it sounded like a single loud event

Understood, but there were loud structural events before that and I'm not sure we know what they are. Do we?

For example when I look at the Theory/Hypothesis spreadsheet here:

Cell F3 [Proven Evidence] identifies three collapses at 1:10 [preceding collapse], 1:15 [main deck collapse] and 1:22 [main building collapse].

And those collapse events were preceded by multiple knocks and multiple louder knocks. At least two waves of multiple structural events before the first [unidentified] collapses.

Is that correct?

EDIT: corrected name of spreadsheet.

 

[IanCA]

I still don't see how that planter next to the wall could have caused the pool deck to break apart there and pull away from the wall,

Jeff, Thanks for raising this concern. I will try to describe tomorrow in more detail how I think it could have happened.

 

[MaudSTL]

@IanCA, no surviving witness saw evidence of a physical collapse at 1:10, when a loud crashing sound was heard in 111 and in the lobby.

Banging noises were heard in 111 from 11 PM until at least 1:10 AM, first by Chani Nir and then by Sarah Nir and Gabe Nir. They heard the loud crashing sound in 111, and Shamoka Furman heard it in the lobby.

There are no witness statements to support a visible collapse at 1:10 AM. The Vazquezes were in the garage after 1:10, when the loud crashing sound was heard, and before 1:15, when the deck collapsed as they rode the elevator to the lobby. They heard very loud cracking seconds before the deck collapsed. We do not know what parking space the Vazquezes used, so we do not know the path they took to walk to the elevator lobby. But they did not report seeing evidence of a collapse while they were walking from their car to the elevator lobby.

 

[Debirlfan]

Not sure if this adds anything, but a new interview with the father of the boy that survived:

Link

 

[IanCA]

no surviving witness saw evidence of a physical collapse at 1:10,

@MaudSTL thank you for responding. Can we agree that there was a collapse at 1:10 before the main deck collapsed?

 

[Red Corona]

It's clear from the reports of noise that there was something structural at 01.10. It doesn't appear to have been a collapse visible in the garage though. So I would say it's more likely to be internal structural failure in the deck than an actual collapse. Perhaps the deck starting to punch at column 76 but still hanging on its rebar mat, or the south wall starting to let go, dropping the ceiling a few inches, but not actually falling yet.

We still don't know which parking space they used but we do know that (i) they must have driven down the ramp and (ii) they walked into the lift room, and any path between those two places gives a view of pretty much the whole garage. I find it hard to believe they wouldn't have noticed fallen ceiling slab, or even a lot of dust in the air, if anything had collapsed when they came home.

 

[FJBnomics]

We still don't know which parking space they used but we do know that (i) they must have driven down the ramp and (ii) they walked into the lift room, and any path between those two places gives a view of pretty much the whole garage. I find it hard to believe they wouldn't have noticed fallen ceiling slab, or even a lot of dust in the air, if anything had collapsed when they came home.

However, if their parking spot was say in North East Corner near the East Stair Tower and I lived on first floor, I for one would take the stairs as the shortest direct path to my apartment/condo. Especially if justing getting back from a gym workout.

So it is possible they immediately turned left off entrance ramp? If 1st collapse was closer to elevator, perhaps they were not aware. I see in recent photos posted the deck delaminated at South Wall. Thus perhaps all that fell initially was the 3/4” concrete. cover below rebar grid?

 

[Sym P. le]

You will stretch your imagination to any length to make shit up.

 

[SFCharlie]

AND, I feel any dive into the minutia of which crack broke first after the K14.1 punch through 2 weeks or so before the collapse isn't very interesting UNLESS it relates to transmitting the collapse to the tower.

SF Charlie
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[SFCharlie]

The problem in my mind is, how was the energy of the collapse "stored" during the seven minutes between the deck and tower collapses?
Was the North tower swaying north and south while the West (Collins side) tower was swaying east west? Were they transferring the energy back a forth between the two? If so, the (stress, strain, distress) between the two must have been horrendous. ( I can't image what it would have been like for the West tower to sway east slamming into the north tower.)
What was going on during those seven minutes?

 

[MaudSTL]

Can we agree that there was a collapse at 1:10 before the main deck collapsed?

No. We can agree that surviving witnesses heard a loud crash that some of them assumed was a collapse. Since no survivor saw a collapse, we cannot know if something actually fell.

 

[IanCA]

1) I still don't see how that planter next to the wall could have caused the pool deck to break apart there and pull away from the wall,

1) The area of the parking deck that collapsed is essentially bounded by column line G.1 to the West and by column line K to the East. We know that the area of the parking deck West of column line G.1 did not collapse and most of the area of the parking deck East of column line G.1 did collapse, so there was a weakness or discontinuity north-south along column line G.1. We can see that the pool deck East of column line K has collapsed against the southern wall leaving the top surface of the deck concave, but the top surface of the parking deck West of column line K is convex, so there is also a discontinuity or weakness running north-south along column line K that extends from the southern property line wall north to somewhere between column lines 14 and 15.

We can observe cracks in the parking deck area between column lines G.1 and K that run generally east-west that are open at the top. So I think it is reasonable to conclude that the top surface of the deck failed in tension. The areas of deck to the north and south of the crack are lower than the crack. The question then becomes which area failed first, the area to the south of the crack or the area to the north? To understand the answer to that question we can consider the two scenarios in detail before the crack is formed and decide whether they are viable.

Scenario 1) the area of deck south of the crack first becomes unsupported. The collapse is progressing from the south to the north. In this case the area bounded by column line G.1, K and the southern wall is now supported by six columns, three along column line 14.1 and three columns along column line 14 / 13.1. The area of the deck south of column line 14.1 is supported in cantilever and the top surface is in tension. Some combination of loads and concrete strength in that area can allow the concrete to crack in the way we see. The area of deck north of the crack and north of column line 14 is sufficiently constrained by the three columns 23 feet to the north along column line 14 / 13.1 to resist rotation of the deck surface upwards. Scenario 1 is a viable condition to produce the top surface crack in tension we see.

Scenario 2) the area of deck north of the crack first becomes unsupported. The collapse is progressing from the north to the south. One or more of the columns along column line 14.1 between column line G.1 and K have punched through. The only remaining support for the parking deck is the connection to the wall and the deck is rotating downwards in the north. We know from sheet S12 of 14 (37 of 336) modified 1.17.80 to reflect change of pile type. That the typical retaining wall is 8” thick plus the concrete over the sheet pile, perhaps 16” total. The question becomes whether it is possible for the deck wall connection to offer sufficient resistance to downward rotation of the deck to the north to create the crack. In this scenario the stress is concentrated in the outside of the wall as the deck hinges on the front surface of the wall. The distance of unsupported deck from the hinge point to the north is at least 49 feet, the length of supporting concrete at the deck wall joint from the hinge point to the outside of the wall is 16 inches. The deck is only 9.5 inches thick but it has two pieces of rebar running horizontally the wall has one piece of rebar running vertically. The deck wall joint cannot offer sufficient resistance to the rotation of the deck to cause the crack we see. The deck wall connection would fail first, just as it did east of column line K. Scenario 2 is not a viable condition to produce the top surface crack in tension we see.

Since the area of deck south of the crack rotates down and the area of the deck north of the wall also rotates down, there must be a hinge point somewhere between the wall and the crack that allows the deck to retract from the wall.

Tha area was never mentioned as a problem area prior to the collapse,

In your helpful video “Analysis Garage Video BEFORE Condo Collapse: Water Everywhere”
From 9:50-15:20 including the important advice at 10:35 “If you don’t tell water where to go, it will make up it’s own mind and it always picks the most expensive course of action”. There is lots of evidence of water damage. And that area of deck underside is stepped down, meaning the water can flow from column line K to the west via capillary action.

2) IF the slab separated from the south wall with cars on it, why did they fall back into the V-shape at the center of the slab (driving lane of the covered parking deck), instead of cars falling forward toward the south wall since the slab separated from the wall?

2) The deck cracked beneath the black pickup truck, its rear wheels dropped to the point the chassis bottomed out, column I14.1 punched through, column I14 punched through, other columns punched through, the deck impacted cars below and fractured [along the construction join?] between column lines 14 and 14.1. The cars didn’t move toward the south wall significantly because they were not between the crack and the wall and the angle of the deck was never steep enough to cause them to roll towards the wall.

 

[IanCA]

The problem in my mind is, how was the energy of the collapse "stored" during the seven minutes between the deck and tower collapses?

I have imagined that the energy was stored as potential energy, with not all of the deck collapsing [as L to M did] adjacent to the building and part being left suspended [ I to L or I to K for example] and continuing to apply torque to the columns along the front of the building at column line 9.1.

What was going on during those seven minutes?

gradual rotational displacement of the columns along 9.1 until the tipping point was finally reached.

 

[MaudSTL]

However, if their parking spot was say in North East Corner near the East Stair Tower and I lived on first floor, I for one would take the stairs as the shortest direct path to my apartment/condo. Especially if justing getting back from a gym workout.

So it is possible they immediately turned left off entrance ramp? If 1st collapse was closer to elevator, perhaps they were not aware. I see in recent photos posted the deck delaminated at South Wall. Thus perhaps all that fell initially was the 3/4” concrete. cover below rebar grid?

You’re confusing the Nirs and the Vazquezes.

Sarah Nir and Gabe Nir did indeed park in Space 14 near the east stairwell when they arrived at around 12:30 AM. They have never stated explicitly that they used the staircase instead of the elevator to get to 111. But your theory does make sense.

Another person who also arrived at about that time and parked in the garage was Eric Zion, who had just dropped his wife off at the hotel where they were staying. I have never found an interview with him to state what space he parked in and whether he saw anything unusual in the garage before he went up to 508. He left before the collapse on his scooter. We do not know for sure whether he left from the lobby or the garage, but since his scooter was in the apartment I theorize it was from the lobby.

We do know for a fact that the Vazquezes used the elevator, even though we do not know which parking space they used or what route they walked to get to the elevator. They heard very loud cracking sounds just before they entered the elevator, and they were inside the elevator when the deck collapsed.

 

[IanCA]

and to all of them it sounded like a single loud event,

This implies there was only one deck collapse event.

We can agree that surviving witnesses heard a loud crash that some of them assumed was a collapse.

A loud crash preceding the primary deck collapse event. This confirms the witnesses reported two events.

 

[MaudSTL]

A loud crash preceding the primary deck collapse event.

The witnesses perceived the loud crash at 1:10 AM as one event. The witnesses perceived the deck collapse at about 1:15 AM as one event. The witnesses perceived the building collapse at 1:22 AM as one event.