--- Eugen Leitl <[EMAIL PROTECTED]> wrote: > On Wed, 19 Mar 2003, Tim May wrote: > > > I think the nearly perfectly vertical collapse of > the WTC towers was > > because of the pancaking of each floor into the > floors below, as shown > > in the videos. Whether removal of one support > triggers pancaking or > > toppling is more complicated than the blocks > example, of course. > > The collapse is self-aligning due to the delay > occurring at each subsequent > segment. I think you'll get a toppling only in > small/extremely > overengineered structures after at an explosion at > the base.
This seems reasonable. As a large structure topples, the sheer stress across the long axis of the building will inexorably increase as the upper floors retard the downward progression of the lower floors (caused of course by gravity). I suspect that a large structure such as a WTC tower would cant no more than a few degrees before loading stresses opposite to the design of the compression structure caused a series of gross structural failures -- which would allow the building to fall mostly `in place'. That is only my intuitive take on the physics of the moments in question. Someone with real knowledge could easily disagree with my naC/ve oversimplification I'm sure. Regards, Steve ______________________________________________________________________ Post your free ad now! http://personals.yahoo.ca
