Apartment Building Collapsed Near Miami

NationalTitles18

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At least one dead, but likely many more will be found. Tragic.

A wing of a 12-story beachfront condo building collapsed in a town outside Miami early Thursday morning, killing at least one person while trapping residents in rubble and twisted metal. Scores of rescuers pulled survivors from the debris as a cloud of dust floated through the neighborhood.

Surfside Mayor Charles Burkett warned during a news conference that the building manager told him the tower was quite full and the death toll was likely to rise.

“The building is literally pancaked,” Burkett said. “That is heartbreaking because it doesn’t mean to me that we are going to be as successful as we wanted to be in finding people alive.”
Rescuers have pulled 35 people from the building and were continuing to look for more, Raide Jadallah, assistant fire chief of operations for Miami-Dade Fire Rescue, said at a news conference.
 

dayhiker

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Work is currently being done on the building’s roof, but Burkett said he did not see how that could have caused the collapse. Authorities did not said what the cause may be.
I speculated with friends earlier that I bet it was flat plate construction and that renovations were being done on the roof resulting in some sort of opening being added close to the column. A fast failure like in that type of construction usually means a shear failure. Flat plates failure mode is typically a punching shear failure. The video I saw was clearly a top down collapse and it sure it sure seemed like a sudden punching type failure.
 

NationalTitles18

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I speculated with friends earlier that I bet it was flat plate construction and that renovations were being done on the roof resulting in some sort of opening being added close to the column. A fast failure like in that type of construction usually means a shear failure. Flat plates failure mode is typically a punching shear failure. The video I saw was clearly a top down collapse and it sure it sure seemed like a sudden punching type failure.
Why would roof work cause this kind of failure, for laymen such as myself?
 

dayhiker

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Why would roof work cause this kind of failure, for laymen such as myself?
If it's flat plate construction, that means a concrete plate with no beams. You have to proportion the slab thickness and column size so that the slab doesn't punch through the column. Picture a wet paper towel oriented horizontal and you push it down on a finger that's oriented like a column. It punches through. If your finger is bigger, you have to push harder for it to punch through. Now take a hole punch and put a hole right by where you're going to poke the paper towel. Now try to push the paper towel down on your finger. Does it punch through easier with the hole really close to the column/your finger? If they added penetrations for HVAC or piping, etc, and put it close to a column, then that COULD cause what we witnessed.

It could also be that they used something called shear rails to increase that punching shear capacity, but they were corroded because of proximity to the beach. The openings were checked, everythign is fine, then you get a failure because you didn't have the shear capacity you thought you had.

It could also be that equipment was being stored on the roof for whatever work they're doing and they stored it where they shouldn't have. I've had a job where they stacked material 4'-5' high in one section of the roof and then bad things happened. Something like that could have happened. Those type of things are still punching shear failures, it just means they overloaded the roof capacity and not the result of cutting holes anywhere.

I should add, cutting holes in floors/roofs after the fact is pretty common. If that was a PT slab, then that's different. You try to avoid cutting a PT slab whenever possible.
 

dayhiker

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(something I love about TideFans is the number of people heavily involved in very specific fields that can come along and very clearly explain things like @dayhiker has recently in this and the I40 bridge thread)...
Thanks. I'll admit that I was really guarded in my speculation on the bridge since I don't do that type of work. I was pretty relieved that my SWAG's wound up being what was described in that video that was later posted. :)
 

NationalTitles18

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If it's flat plate construction, that means a concrete plate with no beams. You have to proportion the slab thickness and column size so that the slab doesn't punch through the column. Picture a wet paper towel oriented horizontal and you push it down on a finger that's oriented like a column. It punches through. If your finger is bigger, you have to push harder for it to punch through. Now take a hole punch and put a hole right by where you're going to poke the paper towel. Now try to push the paper towel down on your finger. Does it punch through easier with the hole really close to the column/your finger? If they added penetrations for HVAC or piping, etc, and put it close to a column, then that COULD cause what we witnessed.

It could also be that they used something called shear rails to increase that punching shear capacity, but they were corroded because of proximity to the beach. The openings were checked, everythign is fine, then you get a failure because you didn't have the shear capacity you thought you had.

It could also be that equipment was being stored on the roof for whatever work they're doing and they stored it where they shouldn't have. I've had a job where they stacked material 4'-5' high in one section of the roof and then bad things happened. Something like that could have happened. Those type of things are still punching shear failures, it just means they overloaded the roof capacity and not the result of cutting holes anywhere.

I should add, cutting holes in floors/roofs after the fact is pretty common. If that was a PT slab, then that's different. You try to avoid cutting a PT slab whenever possible.
I appreciate the explanation. That is helpful in understanding what may have happened.
 
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bvandegraff

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I agree and until seeing this I didn't really understand how bad this was. I thought a small part of the fascia had collapsed not half the building
Looks like more than 2/3's of the building went down. That video is remarkable - it took less than 30 seconds to collapse.

Thanks dayhiker for the highly informed speculation. With all the topics discussed (and discussed thoughtfully and rationally) here, this is truly a year-round board. Look forward to your analysis and that of our other engineers as we learn more.
 

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