Originally posted by 12m8keall2c
Floors:
Corrugated, and typically galvanized, steel decking spot-welded to the joists. Wire mesh is layed upon the decking. While pouring the concrete you
"lift" the mesh, as you go, to ensure in is IN the concrete to enhance strength and prevent shifting/cracking.
The gauge of the wire mesh is much smaller (1/8" to 1/4") than the rebar used in vertical columns pours.
Thanks for the info, man.
Let's consider the implications of a reinforced concrete core, that supported the majority of gravity loads.
First of all, the cores didn't pancake. So we already know that pancake theory did not apply to the cores. And now it looks like the cores were
reinforced concrete too. Aside from claiming the cores were reinforced concrete, I've also seen articles claim that the cores held most of the
gravity loads. This makes sense to me, considering that the perimeter columns were mainly designed to handle wind loads. The core had to be
non-flexible so that the lateral loads transferred to it via the trusses wouldn't cause the cores to move around (again, reinforced concrete?).
Assuming that the cores did handle the majority of the gravity loads (something we've yet to show of course), what would happen if the perimeter
columns and trusses failed on any given floor?
Nothing!
Proving that the cores actually did support that much of the gravity loads would obviously be hard, if not impossible, but if the cores were
reinforced concrete, then they look, at least to me, to have been massive enough to handle much more of the gravity loads than the perimeter
columns.
Maybe a structural engineer would be able to estimate dimensions, get some psf info (a document posted in another thread may help with this) and be
able to give us a rough estimate on how the gravity loads were divided between the core/perimeter? This would be making some assumptions, but would at
least give us a rough figure to see if the cores would've held much more than the perimeter columns vertically.
Handling that much of the gravity loads, the failure of most of the perimeter columns and trusses on any given floor wouldn't result in the collapse
of anything other than that particular floor. All of the floors above would still have the cores to support them vertically. Pancake collapse
could've never happened like this, only a
localized collapse, just like skyscrapers are supposed to be built for.
Anyone following? Think it's worth looking into?
