Miami Beach, Champlain Towers South apartment building collapse, Part 05 111

[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


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[MarkBoB2]

In the first frame of the surveillance video, the center of the building had already dropped down 2 to 3 floors. The parapet for the penthouse roof over the middle section of the building appears to be missing while the parapet for the roof of the 12th floor remains. Building on the narrative that warrenslo and Dold have elaborated, I believe that as a result of penthouse roof weakening induced by the recent installation of anchors close to column tops that may have compromised the rebar underneath and the additional load of roofing materials added to the already critical load of air conditioning units, the penthouse roof may have given way at the front causing the parapet for the penthouse roof over the middle section of the building to crash down behind the parapet for the 12th floor roof, leaving the rear part of the penthouse roof attached like a hinge. This would have caused the penthouse roof to tilt down at about a 20° angle (see photo). This amount of tilt would have caused some of the air conditioning units to topple over because they are already top-heavy as a result of their motors being near the top of the units and placing them even higher on raised metal frames would have caused their centers of gravity to extend over the footing of the frames. After toppling over, they probably rolled downward into the parapets, crashing through the parapets along with the green bag of roofing materials, and then falling further to the deck below right in front of the three critical columns holding up the middle section building. This would have caused the two columns K10 and L10 to punch through the pool deck, initiating the fall of the center section, which then caused more of the pool deck to fall as a result of the loading from the collapsing building.

If we now look at the frame of the TikTok video that Sym P. le has enhanced,

we see a round object inside a squarish frame near column 27 beside a second rectangular object and what appears to be two portions of a broken column. Sym P. le has speculated that the round object inside the squarish frame near column 27 and the second rectangular object to its right are an SUV (possibly a Ford Explorer) positioned head in to parking space 27 that knocked down the column behind it. SFCharlie has speculated that the round object is a washing machine, and JS5180 that is a ventilation fan. Sym P. le has also speculated that the green object is a planter from outside room 111. I believe that the round object inside the squarish frame near column 27 is an air conditioning unit originally installed on the penthouse roof over the middle section of the building. The color even matches the light color of some of the air conditioning units (see photo below). I believe that the rectangular object beside it may be another air conditioning unit and the two rectangular objects adjacent to it may be portions of the parapet for the penthouse roof. I join with warrenslo in believing that the green object is a carrying bag used by the crane to lift materials to the rooftop that was left on the rooftop overnight (see photo below). I believe that these objects slid off the penthouse roof when the roof tilted as a result of the rebars holding the penthouse roof to the front columns were weakened by drilling holes for anchor installation and gave way later during the night as the weaker penthouse roof was heavily loaded with air conditioning units, anchor materials, and roof repairing materials. This event would have happened before the TikTok video was taken seven minutes before the collapse of the entire building, and probably seven minutes before the entire pool deck collapsed. This event would have caused two loud crashing sounds, one when the penthouse roof collapsed onto the roof of floor 12 below, and one when the air conditioning units fell and crashed into the deck below along with sections of the penthouse roof parapet and the green tote bag carrying heavy roofing materials left on the roof overnight by the workers.

 

[Phil1934]

prompted by the Champlain collapse they just closed half the Miami/Dade courthouse for immediate structural repairs.

https://apnews.com/article/business-lifestyle-health-courts-miami-f2934f1febdb5e82eabe3be2bac0b026

 

[zebraso]

In the first frame of the surveillance video,.....

Really good job on that post. On Round object in tic toc being an a/c compressor unit: not sure but I think I see the fan blades.

 

[mb3928]

Yes. The fire pumps should have activated when the system lost pressure through the broken lines. The sensors were most likely not flow sensors, but low pressure sensors. Flow sensors might not trigger on a slow leak that might even drain the system after awhile. Pressure sensors don't distinguish between pressure lost due to a sprinkler activation by fire, or due to a broken feed line. Low pressure by any cause activates the alarms and turns on the fire pumps (if there were pumps required in that system, probably so for that height). It seems the fire system should have activated to flood any line breaks, if not from pumps, just by the city water pressure alone.

In residential & commercial buildings, almost always pressure is maintained by a "jockey" pump controlled by a pressure sensor. A second pressure sensor with a lower setpoint activates the fire pump, as you described. The flow switches are usually installed and wired to the fire alarm system, to detect activation of the sprinkler system - but they don't control any pumps.

Generally anywhere with over 20 sprinkler heads needs to have a flow switch, I'm surprised there was not one shown in the original sprinkler plans for the garage. Possibly a code violation, depending on what was in force at the time.

 

[julootamu]

Just wanted to comment with regard to A/C units on the roof(posted by MarkBoB2). I was an HVAC /Energy Conservation engineer. The units on the roof are small units like you would have in your home probably 3 to 5 tons (12000 btu/hr = 1 ton). Codes require them to be bolted down.

Also they are not top heavy, but bottom heavy with the compressor mounted at the bottom, the coil wrapping around horizontally. A small motor at the top of no more than 1/2 hp is on top that weighs about 20 lbs. I just sold the cond fan motor from my 3.5 ton Carrier on ebay.

Certainly all ac units in the collapsed section ended up on the ground.

 

[Spartan5]

I find it interesting that MarkBoB2 joined the forum to make that post. Where did all of those images come from? It’s like there’s some parallel world where this roof theory lives that bleeds into this one.

If the roof collapsed many minutes before the rest of the building, where are the panicked 911 calls from floors 9, 10, and 11?

If there was some cascade of debris coming off of the roof onto the ground below, how was it that no one observed this or reported noises coming from outside of the units?

Building on the narrative that warrenslo and Dold have elaborated, I believe that as a result of penthouse roof weakening induced by the recent installation of anchors close to column tops that may have compromised the rebar underneath and the additional load of roofing materials added to the already critical load of air conditioning units, the penthouse roof may have given way at the front causing the parapet for the penthouse roof over the middle section of the building to crash down behind the parapet for the 12th floor roof, leaving the rear part of the penthouse roof attached like a hinge

You reference a narrative about this roof collapse being built by warrenslo and dold… but I don’t recall seeing anything being said by dold to that effect. In fact, they had this to say:

That is interesting. I still have a hard time believing that hammerdrilling 4 ~3/4" diameter holes in the roof slab would cause the balcony/roof slab to collapse.

And

I see what you're getting after, but I still find it very unlikely that anything dealing with these davits/anchorposts/whatever, had anything to do with the collapse.

 

[spinspecdrt]

Isn't the view of the TikTok video approximately one column line east of where the AC units and roofing materials would have fell? If your your theory is correct, I think the ac units would be more to the right in the TikTok video???

 

[jbourne8]

MarkBoB2, this was already discussed in a previous thread btw. That circular object is actually the C in their gate. Personally, I think all the green objects down there are just greenery from the planters, because that's really the simplest explanation. I think the tiktok video was taken around 30-60 seconds before the surveillance video as she said when she ended it she walked back to her pool to take another video and when she got there the building started to collapsed. This progressed really quickly and a lot could have happened in that time.

Also, your pic of the surveillance photo is mislabled btw.. those lights that are on near the middle of the building must be for the 9th or 10th floor because they're right around where those vertical lines on the building end. It is a bit of a mystery on why the roof and penthouse aren't visible, but they could have fallen down to the 12th or 11th floors in the second before that video starts.

Also, according to that budget doc it does look like they had a security room btw.. they said that equipment was in the Central Recording Station and the photo they seem to show is of a second monitor. If you look at the Israeli 3D models of the site too, it looks like it went through several reconfigurations downstairs.

 

[SFCharlie]

How many units were there? It looks like the last ones sold went for about $700K. What was the square foot each floor?

Here is some recent info, please see attached pdf


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[SFCharlie]

we see a round object

The round object has already been identified as the garage ceiling ventilation fan.

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[zebraso]

this was already discussed in a previous thread btw. That circular object is actually the C in their gate.

I think he is referring to the other circular object apart from the gate Champlain "C" . It's been discussed here separately as being possible anything from a washing machine to a truck wheel well.

 

[jbourne8]

They also had round tables right next to the planters btw.. could easily be one of those.

 

[SFCharlie]

being possible anything from a washing machine to a truck wheel well

Yes, but then someone found a photo of the ventilation fans in the garage, and this is obviously one of them that was hanging from the ceiling right above where it fell.

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[spsalso]

If something fell from the top of the building and precipitated the collapse, that something should be found near the bottom of the debris pile.

spsalso

 

[SFCharlie]

Part 03

I’m thinking the round object is a ventilation fan, which the plans show as being in that general area.

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[1503-44]

In regards to continuation from Set 04

As I say all the time, Just because codes allow, or better said, do not prohibit a certain design, does not necessarily mean any particular design that meets code is a good idea. This design appears to have deficiencies and in the very least, fosters progressive failure. It may even be effectively unsuitable for use just because of that one characteristic alone. This design also appears to require intensive maintenance, far and above typical levels, especially given the severe environmental stress it has experienced. At the very least, it was not corrosion resistant in areas that it should have been. This design apparently did not incorporate any progressive failure mitigations. There appears to be no good reason why a design that allowed a pool deck collapse to take out 75% of the building was selected. A simple construction isolation joint might have limited damage to loss of the jacuzzi water.

It is also quite typical that codes do not recognise all design flaws, especially those that are still unknown to us as production line engineers faced with new materials, new fabrication and construction methods and what seems to always be more and more stringent economic limitations. Codes typically only cover things that are within our previous realm of collective experience. Seldom will they be adequate when stretching their provisions to the limits, nor exceeding any established practice of the past, maybe even including an architects wet dream trying to make you design your next slab with 2" thick floor slabs and 50ksi concrete. Will you do it if the numbers work based on present code allowables?

Codes change all the time to address new problems that come up as we move forward. Many of which were totally unexpected. We were designing and fabricating high pressure pipe walls with newer and stronger properties, all permissible under our existing codes at the time, only to realise too late that our quality testing methods were not sensitive to discovering laminations in the steel brought on by the new fabrication techniques. Other materials were found to become brittle under lengthy exposure to hydrogen compounds, especially at higher pressures and temperatures. The pipeline design codes were revised. Some materials were deemed unsuitable and prohibited from further use. Others were required to have different quality control procedures, others were required to be normalised by heat treatment.

It is my highly experienced intuition that is now telling me that we will soon see a number of revisions in building design, maintenance, inspection and occupancy codes due to the results we are talking about here today. Even if for some reason we don't, every structural engineer that's reading these now 5 sections will be thinking about how he/she will react the next time an architect or owner says thin slaps, no drop panels, capitals, or beams. If s/he isn't, it might be time to start.

[IEGeezer, No, I have not learned the whistling language Silbo. That is a specific peculiarity of Isla Gomera. Interesting that you know of it. All of these islands are quite different. I'm on Tenerife, la isla de los chicharreros.]

 

[gonefishing2]

WOW is all I can say about MarkBoB2's outstanding post!

 

[Spartan5]

it would not surprise me that most of those residential units are NOT tied down.

On the roof of a 12 story building in a hurricane zone?

I fully agree Penthouse and perhaps 12th floor in middle fell first. Something woke up the security camera to catch the scene after initial trigger.

That would have happened several minutes before the main collapse. When 111 and 611 were hearing noises before they fled the building. Wouldn’t that have all been captured by the security camera as well?

 

[gonefishing2]

If I heard the Penthouse roof crash down and got woke up in middle of night, the last thing I would do is call 911.

I would get my ASS moving fast