Apartment Building Collapsed Near Miami

[92tide]

from the ajc this morning. what a horrible tragedy

Building collapse near Miami: Live updates - June 24, 2021

At least one person was killed early Thursday after a high-rise condo partially collapsed near Miami Beach, Florida.

www.ajc.com

 

[Bamaro]

It seems pretty obvious from the video that, for whatever reason, this building's foundation gave way. It was built on reclaimed wetlands so that probably had something to do with it. There was also a small amount of yearly subsidence measured over its 40 year existence.

 

[Bamaro]

Its now 4 dead, 159 missing

 

[dayhiker]

It seems pretty obvious from the video that, for whatever reason, this building's foundation gave way. It was built on reclaimed wetlands so that probably had something to do with it. There was also a small amount of yearly subsidence measured over its 40 year existence.

It's not obvious to me. There's a big difference between 2mm/year settlement and a sudden free fall like that. Unless that was on limestone and a sinkhole developed, I'm not sure how a foundation suddenly fails to cause what that video showed. I need to watch that video again.

 

[dayhiker]

Initially, I thought it was a top down type collapse. Looking at it again, eh, maybe not. Maybe a foundation did break through a lower layer and give way. Maybe a column suddenly failed. The photo above shows a column out on a corner. Could a column have been hit hard, like full speed hard, by a vehicle and caused the collapse?

 

[dayhiker]

Thinking back to the flat plate construction, in the last 15 years or so, there have been code changes in the concrete code about redundancy steel. There is steel required to be continuous to adjacent supports so that if there is a problem at a support, the slab can still span temporarily to adjacent spans for safety. This type of steel/failure is referred to as running time. I'm serious about that. The member has technically failed, but it hasn't collapsed. Basically, it's sagging like crazy and is obvious that bad things are happening, but it hasn't collapsed. It gives people time to get the heck out of there.

EDIT: I realized I'm using the term steel in multiple usages that's probably confusing. In this instance, I'm saying steel for the rebar that's in the concrete. The code changes mainly have to do with how the rebar is oriented in a slab. In a flat plate, you have a mat of rebar at the top of the slab over the columns. Between columns in both directions, you primarily have steel in the bottom of the slab with very little bottom steel extending to the columns. The code change required a higher percentage of steel, or maybe it was a minimum bar quantity to extend through the column and out into the adjacent span. I don't recall which way it is specified off the top of my head.

 

[dayhiker]

I should add again, all of my comments are based on the speculation that this is a very specific type of construction. I'm going to be really curious to find out what actually happened.

 

[dayhiker]

If that was a structural steel building, then I'm going to blame corrosion. It's much more common to build condos out of concrete though because you can have lower floor to floor heights because the floor structure is thinner.

 

[TexasBama]

Initially, I thought it was a top down type collapse. Looking at it again, eh, maybe not. Maybe a foundation did break through a lower layer and give way. Maybe a column suddenly failed. The photo above shows a column out on a corner. Could a column have been hit hard, like full speed hard, by a vehicle and caused the collapse?

It hard to judge anything from the one video

 

[dayhiker]

It hard to judge anything from the one video

Absolutely.

 

[Bamaro]

If that was a structural steel building, then I'm going to blame corrosion. It's much more common to build condos out of concrete though because you can have lower floor to floor heights because the floor structure is thinner.

When I said probably a foundation collapse I was including (maybe not technically correct) salt water corrosion of below ground rebar etc. as 'foundation'.

 

[TexasBama]

Absolutely.

It does look like the upper floors are intact when the collapse is occurring, which would lead you to believe that its a problem at the bottom. This is a better version of the video. You could reasonably assume the section on the right was undercut by the collapse.

EDIT - it looks like the section on the right was hit near the top and actually twisted before collapsing a few seconds later

https://nymag.com/intelligencer/2021/06/miami-beach-building-collapses.html

 

[TexasBama]

Missing Woman Made Ominous Phone Call Before Miami Collapse

"In hindsight, you always wonder," her son said after the Surfside condo building caved in.

www.yahoo.com

 

[dayhiker]

When I said probably a foundation collapse I was including (maybe not technically correct) salt water corrosion of below ground rebar etc. as 'foundation'.

But the foundation would have to go somewhere. You're probably envisioning a footing at a column when you say that. It's more likely that it's some type of deep foundation, like an auger cast pile. It could be any number of things. Say it's a footing and the rebar has rusted. Yes, the foundation could fail, but then the column starts to push down on the soil and act like it's own foundation, just with a smaller contact area. It's not likely that it would just drive into the soil dropping feet over a second to cause this were corroded rebar be the sole cause.

 

[TexasBama]

But the foundation would have to go somewhere. You're probably envisioning a footing at a column when you say that. It's more likely that it's some type of deep foundation, like an auger cast pile. It could be any number of things. Say it's a footing and the rebar has rusted. Yes, the foundation could fail, but then the column starts to push down on the soil and act like it's own foundation, just with a smaller contact area. It's not likely that it would just drive into the soil dropping feet over a second to cause this were corroded rebar be the sole cause.

WRT corrosion, I’d assume you have to consider what cement they used. Class H is typical in Well design if there is evidence that there may be higher than normal chlorides in any of the water bearing sands that are penetrated.

 

[dayhiker]

I keep thinking about all of this. I remember walking under a condo after Hurricane Ivan. The sand had been scoured out to about 6' below the bottom of the ground floor. If you had a pile cap failing due to a variety of reason and the column started to drop through the pile cap, maybe the column movement creates the sounds the tenant reported. Say the column dropped 2", each floor to column connection now moves. The bending and shear that causes likely induces slab cracking which creates sound. The next day the column/pile cap finally gives way and you have a free fall in that scenario. That's based on there being a large void from scouring due to hurricane, wetlands subsidence, etc. I need to quit blindly speculating about it.

 

[TexasBama]

I need to quit blindly speculating about it.

yeah, it’s not like you’re a structural engineer

 

[TexasBama]

A bid was out for repair/maintenance of the building, and there was a prebid conference at the building last week.

Surfside Condo Plans Reveal Scope Of Concrete Repair Needs Before Collapse

Drawings and bid documents obtained by NBC 6 reveal the scope of the concrete restoration and other work the Champlain South condo association was soliciting for the Surfside building, even as a catastrophic structural failure brought nearly half of the building crumbing to the ground. More than...

www.nbcmiami.com

 

[TIDE-HSV]

I keep thinking about all of this. I remember walking under a condo after Hurricane Ivan. The sand had been scoured out to about 6' below the bottom of the ground floor. If you had a pile cap failing due to a variety of reason and the column started to drop through the pile cap, maybe the column movement creates the sounds the tenant reported. Say the column dropped 2", each floor to column connection now moves. The bending and shear that causes likely induces slab cracking which creates sound. The next day the column/pile cap finally gives way and you have a free fall in that scenario. That's based on there being a large void from scouring due to hurricane, wetlands subsidence, etc. I need to quit blindly speculating about it.

Actually, there was a structural engineer on CNN, who blamed it on a base column. He analyzed the video of the floors collapsing, He concluded that it occurred as a consequence of subsidence but admitted that he didn't know the ultimate cause...

 

[UAH]

I keep thinking about all of this. I remember walking under a condo after Hurricane Ivan. The sand had been scoured out to about 6' below the bottom of the ground floor. If you had a pile cap failing due to a variety of reason and the column started to drop through the pile cap, maybe the column movement creates the sounds the tenant reported. Say the column dropped 2", each floor to column connection now moves. The bending and shear that causes likely induces slab cracking which creates sound. The next day the column/pile cap finally gives way and you have a free fall in that scenario. That's based on there being a large void from scouring due to hurricane, wetlands subsidence, etc. I need to quite blindly speculating about it.

I have been in many of these multi story complexes at various stages of construction from pile drilling and pouring to completed construction. With the redundancy that should have been built into the structure it is difficult to comprehend such a failure would not have been visible in normal day to day occupancy of the building. The failures that led to the catastrophic pancaking of the floors is fairly straightforward. My question is how the long term failure that led to this was ignored until it failed in such a disastrous way.