Collapse initiated at the damaged level. Even if this was only one storey tall (it was in fact taller), the gravitational energy released by the upper block moving down that one story is some eight times more than the energy required to buckle all the columns in a storey. Even on Q24's incorrect picture of equal damage to upper and lower blocks, that's four times more than required to crush both sides of the impact. This leaves you with 17% of the building falling on 83%, still with plenty of energy left over from the first impact and gaining energy with every storey it falls. Next one down is 18% on 82% and so it goes.
You've lost me. It's obviouse from watching the collapse that material is being shed to the sides. It sounds like you're making the claim that the further it collapses the more mass it has? Is that correct?
I've read the discussion on static vs solid material and Q24 nails it. We also have massive damage to the upper block as it tries to pile drive through the point of most resistance.
Edited by W Tell, 28 September 2012 - 11:04 PM.