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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[zebraso]

There seems to be a high probability all those plants were root-bound. Never the less I was thinking that the mechanical force involved in pulverizing concrete might impart a static charge on the dust particles assuming the concrete was dry - not *all* of the concrete was damp. It's less likely in high humidity, so I am not really sure about it. The concrete would not be carrying a charge before the collapse.

 

[MaudSTL]

If the irrigation line was pressurized at the time of the collapse, is it possible that it sprayed the pilaster during the collapse so that it became a dust magnet?

 

[SFCharlie]

I'm sure that there are many contributing factors. I feel that the twitter iPhone video suggests that one of them was the blast of dust at the southwest corner of the pool deck (plaza) as the east tower began to collapse.

SF Charlie
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[MaudSTL]

The dust on the pilaster seems extraordinarily well targeted…very accurate. I’m trying to understand how that targeting could have occurred.

 

[SFCharlie]

The dust on the pilaster seems extraordinarily well targeted…very accurate. I’m trying to understand how that targeting could have occurred.

Thanks, that make your question clear.
Just below where the dust appears on the wall, there is a section of pool deck at the southwest corner, that is turned over, leaving a void. It makes sense to me that the blast that turned this corner over, blew a concentrated stream of dust up onto the wall.


SF Charlie
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[IanCA]

SFCharlie

]Just below where the dust appears on the wall, there is a section of pool deck at the southwest corner, that is turned over, leaving a void.[/quote]

MaudSTL and SFCharlie, thanks for clarifying. I agree.

It makes sense to me that the blast that turned this corner over, blew a concentrated stream of dust up onto the wall.

I suspect the void in that corner was created when the Southern edge of the parking deck disintegrated. And the concentrated stream of dust was blown up the wall and column when the remainder of the pool deck and parking deck collapsed.

 

[IanCA]

Here is an image that combines a few different ideas:

 

[SFCharlie]

I suspect the void in that corner was created when the Southern edge of the parking deck disintegrated. And the concentrated stream of dust was blown up the wall and column when the remainder of the pool deck and parking deck collapsed.

Yes, a reasonable suggestion. I realize that I don't know the sequence of events. I just see this huge geyser of dust going straight up later in the sequence, but don't see dust hanging in the air earlier?

SF Charlie
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[SFCharlie]

Here is an image that combines a few different ideas:

Wow! I love it!


SF Charlie
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[IanCA]

Wow! I love it!

SFCharlie, thank you, I'm very pleased to hear that. Please let me know if you see anywhere I need to make any adjustments or improvements. Would a new sectional view through the garage at the parking deck with more detail be helpful, do you think?

 

[SFCharlie]

I think it is just fine. Simple is best. If you find more info, I would suggest that the new info go into a new image?

SF Charlie
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[FJBnomics]

Please let me know if you see anywhere I need to make any adjustments or improvements.

With IanCA's latest Visualization tool, I am trying to understand the possible implied sequence of events. I have added numbers at end of his arrows trying to understand perhaps an implied sequence of events.

It appears that perhaps step one is the E-W cracking of slab under parking deck planter North side wall, causing planters to roll North, and at some point break the water cooler line and sprinkler lines.

Which then causes deck to retract at 2a and causes tension break in the top of the slab at 2b at same time.

It would appear initially, the E-W rebar just north of the 2b break is temporarily restraining the E-W and the N-S rebar load, and transferring the load.

The loss of N-S tie to wall plus shifted loads causes the complete failure at 3.

Since their is a relatively small liner rectangle of parking deck slab retracted from the South wall, and the area under planters is where concrete and rebar disintegration are worst, there is more powdered concrete in the air at south wall break, when rest of parking deck collapses and creates a high pressure blast of air to blow the heavy dust concentration out and onto the exposed South Wall of broken parking deck Planter, and Pool Deck Pilaster.

Parking deck drops to the West at Same time as to the North, and breaks around pilaster, thus forcing dust cloud out in only one direction, which is towards south wall break at wall?

IanCA, obviously you have deeper thoughts and perhaps you can fine tune this attempt at understanding your Imagine Tool Provided.

 

[SFCharlie]

I have a longer timeline:
Sometime before 87 Park construction was initiated, the pool deck slumped (due to design and construction errors (to achieve goals of cheap and time to market)) and water puddled near the focus area of IanCA's image.
When 87 Park was built, the pavement was removed to the south of the parameter wall, exposing rebar and creating a void that gravel and water could pour into.
Two months before the collapse: the tension in the pool deck and the South wall of the North part of the tower being cantilevered off the stepdown beam, twisted the stepdown beam enough to cause the sliding doors above it to become very difficult to operate.
Two or so weeks before the collapse, the slab under the planters north of the access between the valet parking and the pool deck started to give way, puncturing itself on the column under it.
This increased the tension in the deck catenary. The increased tension and the damage at the south wall/deck joint allowed the west half of the deck to slump, punching through at many columns.

This increased the twist in the stepdown beam to the breaking point near its west end near the gym.
Bang: queue the twitter iPhone video.

SF Charlie
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[IanCA]

@Thermobaric Thanks very much for analyzing the information and contributing to our understanding.

I have added numbers at end of his arrows trying to understand perhaps an implied sequence of events.

If you would be willing to upload a version with numbers we can be sure to use the same reference.

It appears that perhaps step one is the E-W cracking of slab under parking deck planter North side wall, causing planters to roll North,

Yes, I think so, although I am not yet 100% sure which way that crack propagated. Although I think it more likely propagated from the West to the East because in that way the crack is moving further away from the Southern wall and increasing the volume of less well-supported concrete. In that case, the crack is diverging from the wall. I think it is less likely the crack converges with the joint at the wall. Also I see the corner of the pool deck collapse that is bounded by a curved fracture centered near the column as the termination of that phase of the collapse. Please see below:

at some point break the water cooler line and sprinkler lines.

I see what appears to be two PVC pipes (supply and drain?) along the pool deck side of the wall between the pool deck and parking deck leading to the water cooler and it appears the water cooler was included in the area associated with the early part of the collapse. The supply line could have been broken at that stage. As the pipe was breaking there probably was some water jetting out, but I expect that soon developed to an open pipe with a fairly well-organized flow, such as from a hose. So I think the chances that water would be entirely responsible for the dust sticking to the column as suggested by Nukeman948 is relatively low.

Which then causes deck to retract at 2a and causes tension break in the top of the slab at 2b at same time.

Yes, agreed.

Since their is a relatively small liner rectangle of parking deck slab retracted from the South wall, and the area under planters is where concrete and rebar disintegration are worst, there is more powdered concrete in the air at south wall break, when rest of parking deck collapses and creates a high pressure blast of air to blow the heavy dust concentration out and onto the exposed South Wall of broken parking deck Planter, and Pool Deck Pilaster.

That is a good summary, thank you.
"relatively small liner rectangle of parking deck slab", I estimate the size of the area of slab that detached from the wall is about 30 feet East-West by 10-15 feet North-South. My original estimates for the weight of that volume of concrete (structural and stampcrete) were above 40 thousand pounds. Is that a reasonable estimate, I wonder?

"there is more powdered concrete in the air at south wall break". Not only in the air but I suspect there was a large ammount of dust in the debris on the garage floor.

"onto the exposed South Wall of broken parking deck Planter, and Pool Deck Pilaster". Exactly.

 

[IanCA]

When 87 Park was built, the pavement was removed to the south of the parameter wall,

Here is an image I found that gives some idea of the work that went on adjacent to the CTS Southern property line wall.

Two or so weeks before the collapse, the slab under the planters north of the access between the valet parking and the pool deck started to give way, puncturing itself on the column under it.

I think it is possible that partial ductile failure at column K13.1 was sufficient to transfer enough load to the weak concrete at the Southern property line wall/parking deck to cause a rapidly increasing failure (over a few hours) in that area. But I think there has to be sufficient dust and debris at the bottom of the wall before the main area of the deck collapses to get the dust on the column in the way we see.

EDIT: It's ironic there should be a black vehicle like that in the foreground. EDIT: But I see now it is an F-150, so not ironic.

 

[FJBnomics]

Yes, I think so, although I am not yet 100% sure which way that crack propagated. Although I think it more likely propagated from the West to the East because in that way the crack is moving further away from the Southern wall and increasing the volume of less well-supported concrete. In that case, the crack is diverging from the wall. I think it is less likely the crack converges with the joint at the wall. Also I see the corner of the pool deck collapse that is bounded by a curved fracture centered near the column as the termination of that phase of the collapse.

IanCA, I follow your logic on the West to East diverging progression of the possible initial break under North Parking Deck Planter wall, and feel the tear at the East end that you illustrated in the pool deck, is consistent with that being a temporary stopping point of initial collapse propagation. And of course we have a HD Diesel Truck sitting near that possible initiation point, at the time of collapse (perhaps more than double the 'fly spat' car that landed against it?)

Edit: I added image I omitted to post, with the sequence numbers above annotated.

 

[Nukeman948]

As the (water cooler) pipe was breaking there probably was some water jetting out, but I expect that soon developed to an open pipe with a fairly well-organized flow, such as from a hose. So I think the chances that water would be entirely responsible for the dust sticking to the column as suggested by Nukeman948 is relatively low.

The water cooler would only need a 1/2" pipe to feed it with a reducer to 3/8" or even 1/4" at the connection. However it was not the only pipe that could have sprayed water on the wall. Irrigation pipes were mentioned as just one possible example.

Since someone already mentioned the fire sprinkler system was likely damaged at that location, I checked to see what was there. A 2" header pipe forms a loop system so it can be fed from both directions in case there is a break like this one and the 100 hp pump is more than capable of maintaining enough flow @ 130 PSI and 750 GPM to keep that wall doused in water for hours and the pump has the generator to keep it running even if the electric supply is cut off. Perhaps you could see this as increasing the chances of sufficient amounts of water getting on the wall.
Perhaps "a high pressure blast of air to blow the heavy dust concentration" would also blast water through the same opening as the dust was blown through.
Unless someone posts a better idea of what could cause dust to stick to that wall, I'm going to "stick" to the water theory.

Edit: I see the original fire pump was 750 GPM @ 95 PSI (130 psi was for the new pump) but my calculations show 70 PSI would be needed just to reach the 12th floor so 95 PSI would only give 25 PSI at the sprinkler heads and be insufficient to meet the needs at the penthouse level with the new fire code.
From NFPA 20: "A fire pump’s size is dictated by the most hydraulically demanding area of the fire protection system. In many high-rise buildings, this can be the automatic fire standpipe system demand which requires 500 gallons per minute at 100 pounds per square inch at the top of the most remote standpipe, plus 250 gpm for each additional standpipe, up to a maximum of 1,000 gpm for wet systems or 1,250 gpm for dry systems." Well that explains where the 750 gpm comes from. So if there is 100 psi at the top floor there would be 170 psi minimum standby pressure (if my math is right) in the fire sprinklers on the parking level.

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[SFCharlie]

I think we are agreeing with each other. If you see a difference, I don't see it.

SF Charlie
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[SFCharlie]

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

SF Charlie
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[IanCA]

I think we are agreeing with each other. If you see a difference, I don't see it.

Yes, I believe we broadly are in agreement. I only rephrased it slightly to reduce the chances of misinterpretation by other readers in the future. Similar to the way in which things are often described twice in legal documents to clarify a point, using two slightly different perspectives. I suspect I am less certain about the extent of the failure at column K13.1. I studied the planter wall above that column in more detail and I feel more confident now that the wall was displaced inwards toward the plants. Meaning the vertical displacement would be less in reality than it appeared.