Engineer Warned About ‘Major Structural Damage’ Before Miami Condo Tower Collapsed

[railfancwb]

As Ronald Reagan has been quoted as saying: “The most frightening words in the English language ‘I’m from the Government and I’m here to help you.’”

[crockett]

It's pretty simple. Florida consists out of beach sand and not much else, even in central Florida. We have the worst soil for any type of construction. The sand shifts, even when compacted for days. Basically all buildings end up with cracks in the foundation, slabs and often walls as well. Relief cuts are EVERYWHERE and you will still find cracks outside the cuts after a couple decades. All those big concrete chunks are only held together by rebar at some point. Many times they use plain steel rebar, and that rusts even when not exposed, especially in coastal regions.

The building code in the US is already highly questionable (compared to Germany for example), and Florida was never known for buildings that are supposed to last. All our cookie cutter homes with that thin layer of stucco built ever since the late 80s will start failing in 10 to 20 years, to the point that most will take them down and start all over with proper building materials and techniques.

Edited July 2, 2021 by crockett

[railfancwb]

10 hours ago, crockett said:

It's pretty simple. Florida consists out of beach sand and not much else, even in central Florida. We have the worst soil for any type of construction. The sand shifts, even when compacted for days. Basically all buildings end up with cracks in the foundation, slabs and often walls as well. Relief cuts are EVERYWHERE and you will still find cracks outside the cuts after a couple decades. All those big concrete chunks are only held together by rebar at some point. Many times they use plain steel rebar, and that rusts even when not exposed, especially in coastal regions.

The building code in the US is already highly questionable (compared to Germany for example), and Florida was never known for buildings that are supposed to last. All our cookie cutter homes with that thin layer of stucco built ever since the late 80s will start failing in 10 to 20 years, to the point that most will take them down and start all over with proper building materials and techniques.

You were doing good until your final six words. 

[crockett]

52 minutes ago, railfancwb said:

You were doing good until your final six words. 

You are right. Most will rebuild with comparable crap.

Awesome throw-away-society we have.

[crockett]

Just an example.

 

Typical framing in Florida, done with cheap ass 2 by 4s:

 

 

 

Framing in Germany. Those are 5" by 10".

 

 

One will last around 40-60 years (if no storm hits it), the other will last generationS (plural).

[Brad]

On 6/30/2021 at 11:03 AM, SC Tiger said:

Would love to hear what one of our resident structural engineers has to say on this.  @BradI think is one. 

On the weatherstripping - that could be an issue IF it allowed for corrosion or damage to the structural elements of the building.

One resident hits one column, and causes all of that hell?  I'm not seeing that.  Maybe I'm misunderstanding your meaning.

Not only does it seem like a building that size shouldn't be that dependent on a single column, but I would also think that a column in a parking garage would have to be able to take a car impact without destroying it.

I'm not saying that such an impact wouldn't cause a structural ISSUE, but to cause over half the building to collapse?  I'm not seeing that.  

Sorry, I'm late to the party although that's a weird word for the topic. I just have some general thoughts. Without really digging in, my guesses would probably not be very good.

There are a couple of threads at the following engineering forum. https://www.eng-tips.com/threadminder.cfm?pid=815

The attached file has a typical architectural floor plan and selected structural sheets. I extracted them from a huge and disorderly set that's available online. The structure was a pretty typical looking conventional flat plate, meaning that there are only concrete slabs and columns, and no beams, drop panels, or column capitals. The spans were pretty short and the slab thicknesses (9 in. and 9.5 in. at the lowest levels and 8 in. typical) looks normal.

The widespread collapse is weird for this system, which is known for its redundancy due to the continuity of slabs in each direction. The collapse must have start with a column or two. If a slab failed in one span, one would expect a localized collapse. Concrete columns aren't very slender, so a failed slab resulting in a longer column unbraced length doesn't seem likely.

They're obviously zeroing in on corrosion in the salty environment down there. In the concrete standard, ACI 318, the required clear cover of rebar isn't different in such an environment, or in northern places with deicing salts. I find that a little odd, considering how detailed the concrete standard is nowadays. It's enormous. Surely a concrete researcher is writing a proposal to research this now. LOL

Champlain_Towers_South_-_Selected_Arch_and_Strl_Sheets.pdf

Edited July 5, 2021 by Brad

[Brad]

Good animation of the likely cause. Started by punching shear of the Lobby Level slab and then the slab pulls laterally on the edge tower columns, failing them in combined axial and bending. Makes perfect sense to me.

I am still surprised that could take down such a large part of the building.

 

[Huaco Kid]

 I saw Bush taking loaded pallets into the pool chemical-room.