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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[Sym P. le]

To say there was a sequence of events does not address a time frame. The deck collapse happened suddenly so the initial displacement of air from the garage did not contain dust. (My two cents)

 

[FJBnomics]

Thinking out loud, for 1 cent’s worth. Powder can not be pushed up and out at South Wall, until slab creates opening at wall, based upon powder covering South Privacy Wall in photos. Thus it would seem, there has to be a break in slab near South wall with heavily chemically changed concrete. Next step has to be deflection of slab between North and South, where deck hits ground first, thus creating a ground zero point for origination of pressure wave of air exhausted North and South.

If powdered concrete is worse South of that dividing line, then powder exhaust is South and North gets mostly clean air exhaust.

Edit: I also find it troubling that 87 Park planted palm trees in gravel next to Champlain South Wall. See slide 11 NIST image, 12:55 collection of afditional evidence

 

[SFCharlie]

Maybe the cracking in the pool equipment area was more important than we realized earlier on?
(Not that it fell, but that it showed us the strain (distance) at the south perimeter wall?)
Does anyone have a good photo of the pool equipment area, after the debris was removed?

 

[FJBnomics]

Does anyone have a good photo of the pool equipment area, after the debris was removed?

I think the pool chemicals were a very big contributing factor at South Wall, and remember the vent for the pool equipment room was ducted up and into area adjacent to planter between Pool Deck and parking deck. In a photo posted somewhere, I saw that the vent fan area was surrounded by block walls and was completely open on top. Whatever type of vent cap that was attached to the duct work coming thru the 19"x19" hole in structural slab, was inside a larger blocked wall area adjacent to planter.

I would imagine it had some sort of vent cap, which would force fumes to blow downward and outward and around vent cap, inside that area. So this part of structural slab, and those block walls were bathed in pool chemical exhaust 24/7 for 40 years. Then throw in rainy days to wash the exhaust down into structural slab, as vent fan should have been running 24/7.

Edit, mid deck drop could hit garage floor first as it pulled slab away from wall in one of the zones at south wall, and North end of slab at building. Either way, it appears we have continental divide as far as powdered concrete venting.

 

[Jeff Ostroff]

Back on Sept 24 I posted my video where I had 100 or so close-up high-resolution images that I showed on the video. Here are 3 of those images so you can zoom into them.

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[SFCharlie]

Back on Sept 24 I posted my video where I had 100 or so close-up high-resolution images that I showed on the video. Here are 3 of those images so you can zoom into them.

Thank you very much Jeff.

SF Charlie
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[Nukeman948]

The pool room exhaust does not need a vent cap that would "blow downward and outward". We had someone claiming to be an HVAC guy posting on here at one time. I'll bet he knows of a better type of vent cap.

https://www.labconco.com/articles/zero-pressure-weathercap

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[FJBnomics]

Perhaps an expert, could explain how you vent the pool chemicals to atmosphere adjacent to planters and a pool/parking deck without affecting the plants and humans in the area, while also preventing rain from entering duct work, with no visible vent stack, etc. in 1979 residential construction. From the plans it appeared to me there was a side exhaust thru block wall towards pool deck. Perhaps the missing top over that area was due to work being performed on the pool exhaust system.

Other ventilation fans required maintenance, so perhaps the pool ventilation system had failed years before, and there was no exhaust of pool chemicals, thus all the corrosion in that area?

Edit: Further they had a Covered Area in that corner of patio deck, near original pool chemical ventilation fan/exhaust. Looking more likely that a supervisory event might have turned off the exhaust fan or it had not been working for years, as very unlikely those chemicals were vented next to covered patio deck area???

 

[IanCA]

Isn’t prevailing wind also a factor in dust cloud analysis?

I agree that is a valid question. Thanks for asking.

I went back to check again the wind data on weatherUnderground.com and WeatherSpark.com, but the sample rate is only once per hour. I went looking for a better source and found ncei.noaa.gov (National Centres for Environmental Information formerly the National Climate Data Center) Link [Currently unavailable]. Which revealed that the Automated Surface Observing System (ASOS) captures 5 minute and 1 minute data at ~860 stations across the contiguous US summarized here: UCAR ASOS. I found that Iowa State University have a well designed interface to accessing that date here:

http://mesonet.agron.iastate.edu/request/download.phtml?network=FL_ASOS

Also described here: IAState ASOS. Here's a snap shot of the information I entered:

MIA = Miami International
OPF = Miami / Opa Locka
WHWO = Hollywood - North Perry (not FPY = Perry)
Confirmed here:
FAA ASOS KHWO
and here:
Iowa State Mesonet - ASOS

Here is the 5 minute data for 1AM to 2AM for the three nearest stations:
station,valid,drct,sped
MIA,2021-06-24 01:00,40.00,5.75
HWO,2021-06-24 01:00,80.00,5.75
OPF,2021-06-24 01:00,70.00,4.60
HWO,2021-06-24 01:05,80.00,5.75
OPF,2021-06-24 01:05,50.00,4.60
MIA,2021-06-24 01:05,40.00,8.05
OPF,2021-06-24 01:10,60.00,4.60
HWO,2021-06-24 01:10,80.00,5.75
MIA,2021-06-24 01:10,60.00,5.75
MIA,2021-06-24 01:15,60.00,5.75
OPF,2021-06-24 01:15,80.00,5.75
HWO,2021-06-24 01:15,90.00,9.20
MIA,2021-06-24 01:20,60.00,8.05
HWO,2021-06-24 01:20,80.00,5.75
OPF,2021-06-24 01:20,100.00,4.60
OPF,2021-06-24 01:25,110.00,5.75
MIA,2021-06-24 01:25,50.00,5.75
HWO,2021-06-24 01:25,80.00,4.60
MIA,2021-06-24 01:30,60.00,5.75
OPF,2021-06-24 01:30,110.00,5.75
HWO,2021-06-24 01:30,80.00,4.60
MIA,2021-06-24 01:35,90.00,5.75
HWO,2021-06-24 01:35,80.00,5.75
OPF,2021-06-24 01:35,110.00,4.60
MIA,2021-06-24 01:40,50.00,8.05
HWO,2021-06-24 01:40,80.00,5.75
OPF,2021-06-24 01:40,100.00,5.75
OPF,2021-06-24 01:45,100.00,5.75
HWO,2021-06-24 01:45,80.00,4.60
MIA,2021-06-24 01:45,40.00,4.60
HWO,2021-06-24 01:50,80.00,2.30
OPF,2021-06-24 01:50,90.00,4.60
MIA,2021-06-24 01:50,60.00,4.60
MIA,2021-06-24 01:53,60.00,3.45
OPF,2021-06-24 01:53,100.00,6.90
HWO,2021-06-24 01:53,0.00,0.00
MIA,2021-06-24 01:55,50.00,4.60
HWO,2021-06-24 01:55,0.00,0.00
OPF,2021-06-24 01:55,90.00,5.75

I take this to mean that the wind was a light ~6mph breeze from the East (6.13mph at 78.8deg - North by East averaged across the three stations between 1:15 and 1:25AM). I think this agrees with the drift of the dust seen in the CCTV video from 87 Park when the north portion of the building collapses.

Even when the wind is blowing from the North (which it rarely does) the garage entrance is shielded by the adjacent properties and it's low elevation. There probably is some pressure difference between the North and South but I don't think it is significant in this case. There is airflow normally from the garage entrance out though the ventilation fans, but again I think that is less than significant compared to the volume and speed at which air was expelled when the deck collapsed. From your timeline, MaudSTL, we know the gust of wind from the garage was reported by Adriana Sarmiento, which I take to mean the air flow associated with the deck collapse event was remarkable relative to the general atmospheric conditions at the time.

Does that answer your question?

 

[IanCA]

The deck collapse happened suddenly so the initial displacement of air from the garage did not contain dust.

Thank you Sym P. le, I appreciate your response. I would like to share the image below to illustrate the dust I am thinking about.

 

[IanCA]

Powder can not be pushed up and out at South Wall, until slab creates opening at wall, based upon powder covering South Privacy Wall in photos. Thus it would seem, there has to be a break in slab near South wall with heavily chemically changed concrete.

Thanks for clarifying that point thermobaric.

If powdered concrete is worse South of that dividing line, then powder exhaust is South and North gets mostly clean air exhaust.

I completely agree.

 

[IanCA]

So this part of structural slab, and those block walls were bathed in pool chemical exhaust 24/7 for 40 years. Then throw in rainy days to wash the exhaust down into structural slab, as vent fan should have been running 24/7.

Exactly. But even after leaving the vent and surrounding block work, the exhaust fumes were then blown through the adjacent plants, which have a very high specific surface area. This is why they collect far more salt from the prevailing wind than any wall or structural element occupying a similar volume.

 

[Nukeman948]

Looking more likely that a supervisory event might have turned off the exhaust fan...

LOL. Supervisory event? What are you talking about? You mean like from the fire alarm panel? That's not how any of this works.

Fire alarms supervise their wiring circuits to verify that continuity is maintained. We also use supervisory devices to verify that things like shut-off valves on the sprinkler system are not tampered with and the control panel for the fire pump has voltage. A "supervisory event" implies that wires or devices got disconnected or a valve was tampered with. There were no connections from this fire alarm system to that exhaust fan. A fire alarm system should never be wired in a manner that could interfere with the normal operation of any other buildings systems. If a fire alarm relay was wired to control this fan it would be so that if it lost power it would revert to normal operation of the fan.

In a fire event, most AHU fans will be stopped and fire dampers closed to prevent them from spreading fire through their ducts. Exhaust fans may be started by the fire alarm system to evacuate smoke from some parts of a building but it is above my pay grade to determine which fans that might be. I have wired supply fans to start from a fire alarm system to pressurize stairwells with fresh air so that occupants have a safe egress path. It would not make any sense to shut down any of the exhaust fans in this parking deck for a fire event or any other reason. Fresh air enters via the ramp and smoke or fumes (car exhaust and pool room) are expelled by exhaust fans. The only exits were through the lobby, to the pool deck and out the parking deck ramp, therefore, operation of the exhaust fans should have been a maintenance priority. We all know maintenance was sometimes lacking here but if you have any evidence that fans were not working for years, feel free to post it.

Perhaps the pool chemicals evaporate slowly enough and are diluted enough by the fans airflow that they are not as hazardous as you seem to believe they are. We dilute these chemicals with dihydrogen monoxide to make them safe enough for our kids to swim in them and with air to expel their fumes to the atmosphere.

[sub]Move along, nothing to see here.
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[Nukeman948]

I would like to share the image below to illustrate the dust I am thinking about.

Just speculating but high local humidity from vegetation and pool equipment room fan may have caused condensation to form on that column causing the dust to stick there more than the other ones.

[sub]Move along, nothing to see here.
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[IanCA]

@MaudSTL following on from my earlier comment: "volume and speed at which air was expelled when the deck collapsed".
I did a quick calculation and I suspect the airspeed associated with deck collapse and exhaust through the garage entrance could have been as high as 200mph.

All figures approximate
Area of deck that collapsed: 9,287 sqft
Reduction in height: 5ft
Reduction in volume: 46,436 cuft.

Area of exhaust: 144 sqft.
Based on a width of 22' 6" and posted clearance height of 6' 5".

If the deck collapsed in one second the airspeed necessary to force 46 thousand cubic feet of air through an area of 144 square feet could be as high as 321 ft/sec or 219 mph. Assuming the air is incompressible.
I appreciate that not all of the air expelled passed through the garage entrance, as soon as gaps open in the deck they offer an alternative route but that aspect is somewhat accommodated by the reduction in height figure being conservative.

 

[FJBnomics]

Blah, Blah, Blah……

 

[Nukeman948]

Assuming the air is incompressible.

Non-Newtonian air molecules?

Wait 'til Thermopile hears of this.

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[IanCA]

Non-Newtonian

Speaking of which: video link

Could that mean piles driven into saturated silt and sand would be somewhat less supportive than expected? I wonder...

 

[IanCA]

Perhaps the pool chemicals evaporate slowly enough and are diluted enough by the fans airflow that they are not as hazardous as you seem to believe they are. We dilute these chemicals with dihydrogen monoxide to make them safe enough for our kids to swim in them and with air to expel their fumes to the atmosphere

I put salt in my food, swim in, and even drink chlorinated water at times, how harmful could they possibly be?

At this point I would like to bring back the entire post by Vance Wiley:

Vance Wiley (Structural)12 Jul 21 03:45

I apologize for being off in the weeds a bit but this has haunted me for 35 years. I had nothing to do with this event but "Who Woulda Thought?"
The use of stainless steel to support a ceiling over an indoor pool sounds like a good idea, right? Not so much.
Corrosion-doctors.org - swimming pool collapse.

To bring this into focus with the present topic, it is common to spec stainless expansion bolts when exposed to weather. Is that a good idea in a seaside environment?

If this is too far astray just trash it. I will understand.
Thanks,
Vance

From the report:

The Federal Materials Testing Institute, based in Duebendorf, Switzerland, and the Federal Materials Research and Testing Institute of Berlin concluded that the collapse was the result of chloride-induced stress corrosion cracking. The steel rods had been pitted, causing the roof to cave in. The roof collapsed in a zipper-like fashion, starting with the corroded rods. The collapse continued as the remaining rods were unable to bear the increased load. Chloride is a major factor in corrosion of reinforced concrete, as in the case at Uster. The chloride was either already present in the concrete or came from the pool via water vapor. (figure courtesy)

Chloride can overcome the passivity of the natural oxide film on the surface of the steel. The steel, lacking its passive film, readily releases iron atoms into solution (in this case, moisture is present in the concrete due to the humid environment).​

Although that report specifically mentions stainless steel the condition can also apply to carbon steels:
Stress corrosion cracking (SCC) in low and medium strength carbon steels

 

[Jeff Ostroff]

In San Francisco, they build on top of clay and use friction piles that don't go all the way down to the bedrock, too deep. So they rely on the friction to hold the piles in place, and thus create a stable building on top. As a matter of fact what I have found to my dismay too many times, the strongest friction force in the universe is the friction force that keeps two Lowe's 5 gallon buckets stuck together.