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Originally Posted by caligrad
Well that's even worse. You have a giant reinforced concrete box that's tilting. Major cracks in the foundation around the building and in the building itself, which obviously means the steel inside the concrete is contracting/expanding and under severe stress. Yet..... Engineers are allegedly saying "its fine"...…. And now we're supposed to believe that simply digging under the building and adding new piles to support one of the heaviest buildings on the west coast in earthquake country should do the trick.....
Ok i'll bite. But what about the tilt ? will digging down to bedrock correct the tilt? and the fact that the developer had the nerve to say that construction nearby is to blame because they shifted dirt around.....What happens when there's an earthquake??? Both LA and SF have seen sooooooo much new construction in terms of high rises and its been nearly 30 years since both have suffered major earthquakes. If shifting dirt is to blame for this towers lean, lets pray that other developers don't have the same mindset.
at this point I vote tear it down and start over. I feel bad for all those tricked into buying a condo there.
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As a general rule of thumb, in San Francisco office towers are structural steel-framed with concrete elevator cores, of course, but residential buildings are nearly all reinforced concrete like the Millennium tower. I believe it's because the flexibility and swaying that's unavoidable in steel buildings during "minor" tremors would unnerve residents in buildings full of them.
The architects/engineers of the Millennium surely did some testing and concluded, wrongly as it has turned out, that
"friction" piles that do not go all the way to bedrock would be adequate. I do remember watching when they poured the foundation pad and 2 things stood out: (1) The foundation/below grade work on the typical SF tower takes a LONG time--maybe 2 years is typical--and this one took nothing like that but (2) The foundation pad--not the piles but the slab--was exceptionally thick. So evidently they thought they could avaoid the time and expense of drilling to bedrock with those 2 features: Friction piles that do not go to bedrock and an unusually thick, heavy slab.