Video from a camera inside one of the units:

https://twitter.com/_rosiesantana/status/1407970894924992512?ref_src=twsrc%5Etfw%7Ctwcamp%5 Etweetembed%7Ctwterm%5E1407970894924992512%7Ctwgr% 5E%7Ctwcon%5Es1_&ref_url=https%3A%2F%2Fd-13831536054085327483.ampproject.net%2F210612010700 0%2Fframe.html

Well, at least that last part is right.
I agree, he's totally crazy.

These are the 2 most important posts in this thread.
It was a sinkhole effect where the ground collapsed.
You can see the platform around the pool is caved in, yet the umbrellas are intact.
We can end the speculation now.

This may have implications beyond the 2 Champlain Towers

Faces of the "missing."
https://www.dailymail.co.uk/news/article-9729475/Faces-missing-Officials-searching-156-people-three-days-Miami-condo-collapse.html

These were not old geriatrics, but also real young vibrant people.

The following from the engineer's report led me to believe at least part of the area under the pool deck was open and/or underground parking:

http://forums.pelicanparts.com/uploa...1624815308.jpg

I'm not saying this was the case in the condo collapse. But some dodgy construction companies put less cement into the concrete mix to cheapen it. They also build the next floor (putting the lower floor under stress) before the previous floor has properly cured, to speed up the building progress.

The infiltration of water (seawater) into the concrete resulting in the corrosion of the rebar in addition to sketchy concrete recipes is what caused this.

Proper caulking of the balconies and other joints was (and is) absolutely crucial to maintaining the integrity of the structure.

My guess is, during construction, whomever did the caulking was completely unaware of the importance of what they were being paid the minimum to do.

now we know how to update Bleak House for TV

We have had our own high rise scandal here. Fire spreading upwards via external decorative cladding acting I think as a conduit. The cladding,sold for use this use, turns out to be highly inflammables. 70 odd people died in one building , but now hundreds of others with this cladding have been declared unsafe. The poor individual owners are having to pay huge sums, which most cannot afford, to have the buildings made safe. In the meantime, unsurprisingly, their properties are unsaleable. This aluminium cladding is supplied by a French company, although I think the ultimate owners are either from the US or Canada. I cannot understand why our Government isn't making this company pay for everything.

The lack proper building codes was the problem with that building.

This type of comment has no basis in fact.

Construction companies don't mix their concrete. They order it from a ready-mx company. The mix design is spec'd by the structural engineer. A testing company tests it on site and in the lab. All four of them are independent of each other.

Quite a bit of that going on in this thread...

From the incorrect statements about rebar...waterproofing, etc.

Usually the only variable to concrete delivered to a job site is the amount of water in the mix. Typically central mix concrete is batched with 90% water added at the plant.. A 10% window is allowed for adjustment at the site for workability, etc..

Of course sometimes a contactor will add water such that the mix now has 125% design water in it.. so the laborers and finishers don't have to bust ass so much.. even with extra added water , the concrete cylinder breaks exceed the design strength!

Now batching is quite accurate.. sand, stone, cement, admixtures are scaled and added automatically...in the 80's it may have been a guy watching from a dirty window, looking at scales.. and a guy climbing on a truck dumping some air entrainment or retarder in the drum..

Transit and truck mix concrete are rarities in the NYC area..

This failure will probably be blamed on lack of preventive maintenance... The building was probably shoddily built...but I bet little or no maintenance has ever been done..

I believe you’re referring to Aluminum Composite Panels. Very common in rain-screen systems. I think what you’re referring to is an unanticipated consequence. Most codes don’t contemplate a fire on the outside of the building unless another is immediately adjacent.

Modern specs for ACM call for a fire rated core for this reason.


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These closeups show rebar but I don't see post tension cable hanging anywhere.

http://forums.pelicanparts.com/uploa...1624839483.jpg


http://forums.pelicanparts.com/uploa...1624839503.jpg

Nor do I, and actually what I see of the rebar, it doesn't appear to be in bad shape, a little corrosion where the balcony meets the interior..

Post tensioned cables weren’t in widespread use in buildings like this one when this one was built. In any event, they wouldn’t have been in the columns and those were what failed. It’s obvious that there was some rusting of the rebar in the balcony slabs and the report indicated the previous repairs were done improperly.

I don’t think any of that matters. What looks most likely to me is that the foundation failed catastrophically. If that description by the woman in the building to her husband is correct and the slab adjacent to the pool collapsed before the building fell, then I think it is most likely that the failure was begun in whatever this building was built on. I have no idea if there are piers extending into limestone, or what the foundation might be.

This. Back in the 1970's and 80's I was involved with a lot of highway construction, and we used a lot of Portland. As I recall, the rebar back in those days was mostly uncoated, raw steel. As time and salt on the highways wore on, many bridge decks failed (not catastrophically, basically the surfaces spalled badly because of rusted rebar. Later on, factory coated rebar appeared reducing the rust problem. If the condo building was build in 1980 with uncoated rebar (seems likely) in a high salt environment and no one keeping up with the waterproofing, then eventually the salt will get to the rebar and rust would be unchecked. Eventually the concrete is damaged. The rebar is vital to the integrity of the structure.

Li batteries, damaged in all likelihood, and water are a bad combination.

The comment is based on fact. This is the reason buildings fall down in Italy. You guys obviously have checks and balances - that's good. But the comment certainly was based on fact.

The fire in the London tower block was started at a refrigerator inside the building. Somehow it spread to the outside,( maybe through an open window?) then rapidly spread upwards via the external panels.