On Mon, 8 May 2017 10:54:54 -0700 (PDT), Steve
wrote:



I had recalled reading that somewhere, but after doing some research,
it appears that the exterior diagonalized tube is is the structural
system in most common use for tall buildings.

What I had earlier read was that some buildings have a concrete
structural core, and the floors are cantilevered from the core.

Thumbs up! I appreciated your reply and I was quite curious myself. I had a little time last night, I did some research and found that Mid-rises may or may not have a core, and that in some instances, the cores ARE structural components, and others not, just like you noted.

Yes, often the core supports the building's static load and the
bracing at the edges keeps it all "rigid". There was one building
where I used to live where they put up piers (every 20'?) to support
the building, poured each floor jacked them into position one at a
time - top floor first (obviously). The floor slabs were hanging from
the piers and everything else was just partitions.

Tall buildings are designed to flex, some more than others. SF codes,
thus designs, are way different than NY codes.

All buildings are unique, that's for sure. Thanks for the follow up!

That's why we have architects and civil engineers. ;-)

Remember, any old fool can build a building or bridge that'll stand
up. It takes an engineer to design one that barely stands. ;-)