Miami Beach, Champlain Towers South apartment building collapse, Part 04 49

[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

SF Charlie
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[SFCharlie]

Please allow me to move the discussion to Miami Beach, Champlain Towers South apartment building collapse, Part 05,
Thank-you.
Someone Please close this post to new postings, or message me how to do this, Thanks.

SF Charlie
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[Awestruc]

The building had no beams because it is a 2-way flat plate design. It was not a mistake as eluded to in the video. This design and construction method is very popular in the US because it simplifies the formwork, uses less concrete, and therefor is faster and cheaper. I’d be willing to bet the new condo next door is built with 2-way flat plate construction, although it’s probably post-tensioned with better connections.
With that said, the governing failure mechanism is punching shear, which is not a ductile failure mode…it happens suddenly. Beams, drop panels, and shear walls would have helped. There are many ways this building could have been better, stronger, more redundant. But developers want the cheapest building allowed by code. Contractors want the easiest building method. Architects love the ceiling height and views created by this method too. The end user, whom the building is supposed to protect, is not involved in the building process. So what incentive is there for an engineer to design something better if it costs more and is more difficult to build?
People assume that if it meets code then it’s safe.
But life safety is only one goal of the code committee’s who write the code and it is balanced with cost of construction. Concrete has to stay competitive with steel and vice versa. Post-tension has to be competitive with steel and RC concrete,etc. There appears to be a false presumption by the public that buildings are over-designed and redundant, but that’s not really the case. In reality they are rarely, if ever, tested to design loads and can generally sit there half empty with poor maintenance for a long time.

 

[SFCharlie]

and therefor is faster and cheaper

Ture, but sad. 105 or so lives lost. Probably about $300M in liability. (Yes the concrete was "soft", Yes the re-bar was under-nourished, still)

SF Charlie
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[gonefishing2]

Awestruc, thanks for your response. What I was leading into was residents reporting the building was shaking, perhaps when they drove sheet piles within 10 feet of garage wall. The movement could have been floor slab deflections, beam deflections or column movements. Point being, there without sufficient lateral bracing and rigid enough floors, it appears this is over time loosening up what little reinforcement there is at flat slab interface with columns. Thus time and cycles as mentioned in forum is weakening structure. With sufficient minimum lateral support and reasonable deflection it does not seem building should be moving?

The penthouse, stair tower and elevator shaft don’t appear to have reinforcement in CMU in fill walls. I would think sway from wind or construction next door, or 3.9 bomb effect would cause a more dynamic input into structure than wind loads against apparent sufficient shear resistance from East?

Hope this helps explain my train of thought.

 

[Vance Wiley]

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

 

[boo1]

Mechanical equipment located at height more than 100 feet shall comply with FMC 301.15,
have a site-specific design (signed and sealed) by a Florida Professional Engineer, indicating
the location of mechanical equipment, the required design pressures and the installation
method.

Page 19

 

[waross]

SFCharlie (Computer)
(OP)
10 Jul 21 17:31
Please allow me to move the discussion to Miami Beach, Champlain Towers South apartment building collapse, Part 05,
Thank-you.
Someone Please close this post to new postings, or message me how to do this, Thanks.

SFCharlie (Computer)
(OP)
10 Jul 21 17:58

Quote (Awestruc (Structural)10 Jul 21 17:47)
and therefor is faster and cheaper

Ture, but sad. 105 or so lives lost. Probably about $300M in liability. (Yes the concrete was "soft", Yes the re-bar was under-nourished, still)

David and 1503-44; Resistance is futile. You will be ignored!

Bill
--------------------
Ohm's law
Not just a good idea;
It's the LAW!