Miami Beach, Champlain Towers South apartment building collapse, Part 13 44

[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
Miami Beach, Champlain Towers South apartment building collapse, Part 05
Miami Beach, Champlain Towers South apartment building collapse, Part 06
Miami Beach, Champlain Towers South apartment building collapse, Part 07
Miami Beach, Champlain Towers South apartment building collapse, Part 08
Miami Beach, Champlain Towers South apartment building collapse, Part 09
Miami Beach, Champlain Towers South apartment building collapse, Part 10
Miami Beach, Champlain Towers South apartment building collapse, Part 11
Miami Beach, Champlain Towers South apartment building collapse, Part 12


SF Charlie
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[Reverse_Bias]

Re liquefaction or other ground issues: There were some reasonable hypotheses in this area, but as the critical columns in the pool deck collapse appear to be intact, and the basement slab looked in good condition after the clearance, I think we can take any foundation-based theory off the table.

Re the concrete being apparently sub spec or degraded: why, then, is nobody scared about CTN? It was built pretty much at the same time by the same people, so if the worry is the structural elements of the building, you'd expect that to be true there, too (and in fact in every 1970s/80s reinforced concrete structure in the area ...).

> If this were the case, there should have been those bars still connecting each "side" of the slab. They would now be found surrounding the bottom of the columns.

All the pool deck columns, and the ones under the surface parking like @AusG's photo, had their slab around the base. I'm sure NIST had a good look at those bits of slab before clearing the site.

The foundation was leaking and causing corrosion at the base of some of the columns. K and L where the standing water was had a lot of corrosion at the base.

As far as uneven subsidence, liquification or a sinkhole, those can probably be ruled out. I've seen no evidence of it and it is also not consistent with a collapse starting at the deck, it probably would have started on the more heavily loaded columns under the building if this were the case.

 

[SFCharlie]

Well, the slow boat from ACI arrived in the mail. It came well protected in a cushioned paper mailer and a flexible Blu-ray style box. The thumb drive itself is compact and folds, pocketknife style, into a sturdy steel key ring cover, perfect for taking to the job site.
It took a call to support. John promptly sent me a zip file of the latest .pdf files and now everything works fine. Please find an extract of a few pages attached. edit Images Only

 

[dik]

The corrosion was likely caused by inadequate concrete strength coupled with inadequate concrete cover to the reinforcing. Even the later patch repair details didn't reflect good corrosion resistance.

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

 

[SFCharlie]

Fixing Florida’s aging condo mess after the Surfside collapse means changing the laws | Opinion

David B. Haber specializes in condominium law and represents condominium associations. His other practice areas include construction, complex business litigation and real estate law.

 

[MaudSTL]

The archived version. A condo lawyer proposes legislation to allow forced sales in order to facilitate condo terminations. The author doesn’t include a proposal that facilitates relocation of fixed income elders. Fixing Florida’s aging condo mess after the Surfside collapse means changing the laws | Opinion

 

[SFCharlie]

Here in the SF bay area, relocation often includes some allowance for relocation expenses paid buy the landlord.

California Now Requires Relocation Assistance Payment to Tenants for Allowable No-Fault Evictions.

Although the new law essentially prohibits a California residential landlord from terminating a tenancy without just cause, as set forth above, there are some exceptions.

A Landlord may initiate a no-fault termination of tenancy with the payment of Relocation Assistance for any one of the following reasons:

The Owner seeks to owner-occupy the residential property, or have their spouse, domestic partner, children, grandchildren, parents or grandparents occupy the premises, but for leases entered into on or after July 1, 2020, owner occupancy shall only be allowed IF either: (a) the tenant agrees, in writing, to the termination, or (b) a provision in the lease allows the owner to terminate the lease if the owner, or their spouse, domestic partner, children, grandchildren, parents, or grandparents, unilaterally decides to occupy the Premises;
The Owner seeks to withdrawal of the residential property from the rental market;
The Owner is complying with any of the following: (a) a government order to comply that necessitates the tenant vacate the premises; (b) a government or court order; or (c) a local ordinance; OR
The Owner is seeking to demolish or substantially remodel the rental property (Note: substantial remodel is defined to mean upgrading structural, electrical, plumbing, or mechanical system that requires a permit from a governmental agency, or the abatement of hazardous materials, including lead-based paint, mold, or asbestos, in accordance with applicable federal, state, and local laws, that cannot be reasonably accomplished in a safe manner with the tenant in place and that requires the tenant to vacate the residential real property for at least 30 days. Cosmetic improvements alone, including painting, decorating, and minor repairs, or other work that can be performed safely without having the residential real property vacated, do not qualify as substantial rehabilitation.
The amount of relocation assistance, or rent waiver, required is one month's rent as in effect when the owner issued the notice to terminate the tenancy and must be paid to the Tenant within 15 calendar days of service of the Notice Terminating the Tenancy.

Some local jurisdiction demand more, for example 120% one months rent.

 

[Vance Wiley]

Many thanks for posting the ACI thumb drive section, Charlie.
The section had reinforcing cover and placements defined, but no limits for column reinforcing.
Paragraph 7.7.5 addresses "corrosive environments or other severe exposure conditions" and suggests (? requires?) greater cover and more dense concrete or other protection.
If I recall, column design and limits of reinforcing was addressed in Chapter 10.

 

[SFCharlie]

If I recall, column design and limits of reinforcing was addressed in Chapter 10.

The paragraph numbers seem to have changed since 1977?
Please find attached a few page images from chapter 10.


SF Charlie
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[Optical98]

More shots fired at the NYT's article via Kilsheimer >>

Question of what caused Surfside, Florida, condo to collapse remains unresolved

https://www.wsws.org/en/articles/2021/09/10/surf-s10.html

 

[Vance Wiley]

That's it !!
Sectiom 10.9.1 LIMITS FOR REINFORCEMENT OF COMPRESSION MEMBERS.
10.9.1 Area of longitudinal reinforcement for non-composite compression members shall not be less than 0.01 not more than 0.08 times gross area Ag of section.

I see nothing mentioning lap zones. It is my thought that the columns that I have investigated so far met requirements of the then current ACI code as regards minimum and maximum amounts of main reinforcing.

 

[SFCharlie]

Back in 1977 the ACI published the Commentary as a separate Document. Here are images from an excerpt of the commentary on chapter 10.

SF Charlie
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[Spartan5]

More shots fired at the NYT's article via Kilsheimer >>

If he’s that wound about about the NYT, I can only imagine what he has to think about the jokers here!

“You wouldn’t believe some of the stuff people are writing,”

Ain’t that the truth.

 

[Demented]

If he’s that wound about about the NYT, I can only imagine what he has to think about the jokers here!

Ruptured aneurysm territory.

Precision guess work based on information provided by those of questionable knowledge

 

[SFCharlie]

This is from the SunSentinel via MSN
Building code board struggles with making inspection changes

SF Charlie
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[AutisticBez]

Jeff, 4 inches makes a huge difference to vehicle impact. 12 inches puts you around the 40km/h mark. 16 inches starts to make bottom shear impossible without high impact speeds. With increased concrete strength the required impact speed to bottom shear column increases exponentionally. If anything 12 inch column thickness is what I feel is a vulnerable weak state where vehicle impact data becomes impossible to ignore.

 

[Vance Wiley]

OOPS. Spoke too soon.
The Commentary on Column Reinforcement in the 1977 ACY 318 DOES address a 4% maximum reinforcing limit as follows:
10.9.1 The percentage of reinforcement in columns should usually not exceed 4 percent if the column bars are required to be lap spliced.

So does the term "should usually" define a violation of the code?
I would point out that procedures are and were available to ensure good concrete and full bonding of reinforcing in areas of congestion and bars were spliced while in contact - but the use of such techniques was probably beyond the capability of the contractor, if other conditions and results are any indication.
Then the next point becomes 'did the escess reinforcing cause the collapse'?

 

[SFCharlie]

I thought we had been through this before...
A violation of the Commentary is not a violation of the code.
The 4% is so that the lap spices will not exceed 8%

SF Charlie
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[Demented]

If I am not mistaken, water has been spotted wicking it's way up rebar at the slab/column connections. Several columns also having fully rusted through rebar at the base. Not sure which columns, but it does seem to be situated around crowded columns.

Precision guess work based on information provided by those of questionable knowledge

 

[AusG]

Iirc the congestion issue arose not because it would by itself threaten the building but that crowded joints at the lower floors might present the contractor's people with excuses to leave out or mis-position some of the slab reinforcing at the column joints.

 

[Vance Wiley]

Sorry - I missed the consensus on Commentaries. But as far as I know the "double area" of bars at a lap splice was not defined prior to ACI 318-77 and it was later editions which defined the reason and application, with the concern being congestion and correct concrete placement.
It is a fine point, but attorneys make their livings on fine points.
From the viewpoint of amount of effective reinforcing contributing to the performance of a column I do not see an issue. As one bar loses load in a lap splice the lapping bar gains force. And I note that tests of columns with 12% reinforcing effectively performed like those having reinforcing within current limits.