Miami Beach, Champlain Towers South apartment building collapse, Part 03 148

[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

Thank you

SF Charlie
Eng-Tips.com Forum Policies

 

[Mark R]

This event has obviously raised concerns elsewhere. Here's a video from the parking garage of a condo complex in Key Biscayne that was built in 1971.
Key Biscayne

 

[charliealphabravo]

Ok, why is it so hard to find aerial photos of the new pile?

My experience is that the rescue team will be getting daily updates to aerial photography through Pictometry. It may be flown privately or by a commercial source but access to this new imagery may be limited during the declared emergency.

 

[Vance Wiley]

Speaking of photography and videography, it would have been cool if they had placed some sacrificial cameras in critical locations inside the building and broadcast video while it was collapsing.
It was an opportunity to see just how this building collapses, by viewing an actual part of the original building as it failed and fell.

 

[JohnRBaker]

Who says they didn't?

John R. Baker, P.E. (ret)
EX-'Product Evangelist'
Irvine, CA
Siemens PLM:
UG/NX Museum:

The secret of life is not finding someone to live with
It's finding someone you can't live without

 

[SFCharlie]

Who says they didn't?

Yes!

demolition companies often document their "shots"

SF Charlie
Eng-Tips.com Forum Policies

 

[Lizard7709]

warrenslo (Structural)4 Jul 21 23:56
Apparently as of May 26, 2021, there was a crane on 88th (north side of building) with outriggers sitting on the garage structure carrying roofing supplies and "tar" to the roof. Maria Notkin of Apt. 302 made the initial complaint - she appears to be the same unit who called their relatives from their landline multiple times after collapse. They were asking for the crane to be moved from 88th to Collins, the association said they needed the crane on 88th to reach the entire roof. See page 40 of email communication documents uploaded by the city. Link

Reading through this I’m wondering if they could of overloaded the garage ceiling with the tar kettle. I’m having a hard time finding what the weight of a tar kettle is full. The weights I’m finding is up to 5000 lbs but I’m not clear on if that’s full. The way Maria describes the location of the kettle I’m guessing it to be on the red in the graphic. She describes the kettle being under the condo units. I’m assuming that to mean under the balcony or close to the building.

I’m guessing based on her living in a 2 bedroom 2 bath and the fact she is on the north side that her condo is located in the yellow.

I wish there was a diagram showing how it all went together. I did a bit of guessing so take this with a grain of salt.

 

[spsalso]

I agree, Mr. Wiley.

NIST has been there a week. They have had enough time to act on ideas such as yours. As true professionals from the Federal government, I have no doubt they have done those very things. And we will eventually, in a year or five, see them

Too much? Yeah. I couldn't help myself!


spsalso

 

[SFCharlie]

controlled-demolition.com/media
CDI doesn't seem to have this up on their site yet, but how can they resist posting such a text book example of what they can do?

SF Charlie
Eng-Tips.com Forum Policies

 

[SFCharlie]

How the Surfside tower was imploded in just days: Hours of drilling, 128 lbs of dynamite
(nice ground level shot of the "new" pile)

SF Charlie
Eng-Tips.com Forum Policies

 

[SFCharlie]

Watch Live: Champlain Towers South Aftermath
YouTube channel BecauseSurfside has a live feed looking down on the recovery effort

SF Charlie
Eng-Tips.com Forum Policies

 

[Js5180]

Lizard - there were two tar kettles on the roof at the time of the collapse. They aren’t heavy. They are under the DOT limit for trailers requiring their own brakes - this includes tar kettles, air compressors, small household trailers, etc.

 

[FacEngrPE]

Link to 12 years of CDI Demolition Videos
The Art of Demolition, a compilation, 10 minutes of clips of jobs back onto the 1980's, and perhaps older. One of these is from my employers site.

 

[Mark R]

Lizard - there were two tar kettles on the roof at the time of the collapse. They aren’t heavy. They are under the DOT limit for trailers requiring their own brakes - this includes tar kettles, air compressors, small household trailers, etc

Those are tar buggies and are just used to transport the tar that has already been heated. The one in question is the larger type that have all the heating equipment built into them etc. I've never seen them place on the roof they are usually placed on the ground in the heated product is either piped to the roof or dumped into buggies like are shown on the roof and lifted to the roof or other place they are being used. They are much larger and heavier.

 

[LittleInch]

I can understand that many people here are searching for a trigger event, but I think we're all missing the point here.

What ever scenario anyone is coming up with - column being hit by a truck, something falling off the roof, sea level etc, unless there was a fairly large scale subterranean collapse / sink hole, this building should not have collapsed.

It is only because there were multiple failings and damage from corrosion to the structure, almost certainly starting somewhere on the pool deck slab, combined with some spectacularly weedy reinforcement / punching effect that as someone posted early on that this building had simply reached a level of terminal overall fabric damage and hence some minor event, or simply final failure of a highly corroded reinforcement triggered progressive collapse of the parking roof structure and finally pulled over two or three of the columns or they failed in buckling due to lack of support.

The building nearly survived lets not forget looking at the tik tok video apparently showing at least one column collapsed, but the building just started to find alternative load paths which then failed due to the overall poor design and maintenance of the structure.

This then is the conundrum for many structures - outwardly they seem perfectly serviceable with no one doing a design check to todays standards for the basic design, damage that can't be seen or required destructive investigation to a living building and a very slow gradual deterioration and reduction in the factor of safety until it gets to less than 1. I don't find it difficult to believe that the owners didn't really want to or couldn't find the additional capital required to essentially half re-build the structure. I can imagine mortgage companies are suddenly thinking to themselves how can we lend money to buy something which may fall down or may become essentially worthless if you then need to spend 30-50% of the "value" of the property after 30-40 years to stop it falling down.

So yes, in the fullness of time someone might find the smoking piece of straw that broke this camel, but that shouldn't obscure anyone from thinking we can just fix that issue and it will be alright. It won't as some other straw could have easily brought this building down.

I don't know enough about design of buildings like this to know if what appears to be a major factor - the pool deck and first floor being designed and built as one monolithic slab - is common place or not. If it is then lots of buildings are in trouble down there, but if this is a bit of an oddball design then it might be ok.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[gonefishing2]

https://www.enr.com/articles/52048-...earch-for-victims-of-champlain-towers-tragedy

Article where CDI mentions soft concrete and as built not matching 1979 plans in basement area

 

[gonefishing2]

Quote: "Concrete testing at the Champlain Towers South condo last year “yielded some curious results,” engineering company Morabito Consultants wrote in an October 2020 report obtained by The Miami Herald."

Could curious have something to do with CDI's Soft Concrete Comment?

 

[tmwaits1]

A comment was made earlier that people are spending too much time looking for the straw that broke the camels back and I agree. We need to focus more on the original design and mistakes there that made the building so vulnerable to collapse. There are many indications in the original plans that the design was inadequate including punching shear of the pile caps and floor slabs and generally weak connections at the columns.
One thing that you can see in the news right now are statements from structural engineers that the north building is safe because “we did an inspection blah blah blah...”. It is not appropriate for engineers to make a statement like this about the north tower being safe without definitively knowing the cause of the south tower collapse. Remember that despite the media’s interpretation that poor maintenance caused the collapse there really is no documented evidence from morabito that shows spalling and rebar corrosion of such severity that collapse would occur in three years. This is a very strong indication that the underlying cause was a design flaw which by logic is in both the south and north towers.

 

[Murph 9000]

I think it's useful to identify as many potential triggers as possible. Some may be relatively easy to eliminate or mitigate in the future. Understanding the collapse from beginning to end is how we learn to prevent it in future. We shouldn't put all the focus on the trigger, as there are other very important contributing factors, but it's wrong to ignore it.

In the Swiss cheese model, every hole you plug stops the disaster if they align. The trigger is one of the holes.

 

[warrenslo]

We need to focus more on the original design and mistakes there that made the building so vulnerable to collapse. There are many indications in the original plans that the design was inadequate including punching shear of the pile caps and floor slabs and generally weak connections at the columns.

The building code has changed significantly since this building was built - methods used then aren't allowed today. With that said, if those methods were inadequate, it would have collapsed during or shortly after construction when loaded. The discussion I put forth in prior posts is why is a modern roof anchor loading test being performed on an older structure which may not be able to withstand such test. These inspections (which typically consist of tests) were done 14 hours prior to collapse per the city.

One thing that you can see in the news right now are statements from structural engineers that the north building is safe because “we did an inspection blah blah blah...”. It is not appropriate for engineers to make a statement like this about the north tower being safe without definitively knowing the cause of the south tower collapse. Remember that despite the media’s interpretation that poor maintenance caused the collapse there really is no documented evidence from morabito that shows spalling and rebar corrosion of such severity that collapse would occur in three years. This is a very strong indication that the underlying cause was a design flaw which by logic is in both the south and north towers.

It is perfectly ok for a licensed engineer in their best judgment to state a building is safe for occupancy. Otherwise, many older buildings in this country would not be allowed occupancy. Safe for occupancy doesn't mean compliant with all current codes, it's not feasible to upgrade every older building to today's codes, that's why generally only the most important buildings are constantly upgraded (i.e. hospitals, 911 call centers, etc.) The remaining are upgraded for important elements (i.e. sprinklers, fire protection, electrical, backup power, etc.) This building had extensive concrete repairs less than 10 years ago per drawings uploaded by the city - it was not in as bad of shape as everyone makes it out to be.

Remember that despite the media’s interpretation that poor maintenance caused the collapse there really is no documented evidence from morabito that shows spalling and rebar corrosion of such severity that collapse would occur in three years. This is a very strong indication that the underlying cause was a design flaw which by logic is in both the south and north towers.

The media's interpretation is because Morabito immediately hired a PR firm (their name is in all their statements) after the collapse. The media typically just reports these press releases verbatim - they are pretty lazy. The north tower is in much better shape according to those who have inspected it and had a different design (studio vs. 2br at x10 unit) at/near the point of collapse. The north building does not appear to have any fall protection installed (none really is needed, the building can be accessed from a cherry picker as we saw after collapse) and the east building appears to have a different type of fall protection system from aerial photos.

 

[warrenslo]

https://www.enr.com/articles/52048-implosion-enabl...

Article where CDI mentions soft concrete and as built not matching 1979 plans in basement area

In one area, for example, the columns measured 24 in. in diameter, while the plans showed them to be 16 in. in diameter. On the other hand, Loizeaux reported, columns in one section of the building should have been constructed with 6,000-psi concrete, according to the plans. Instead, he estimated—without verifying via testing—the concrete’s actual strength was “not even close” and “much softer” than 6,000 psi.

Loizeaux did not observe much corrosion in the reinforcing steel. “I didn’t see any poor construction methods," he adds. "I didn’t see anything like that.”

Interesting larger columns, softer concrete, and rebar in good shape.