Originally Posted by stateofgrace
Well, if you look carefully on the video, the roof line displaces 33 meters down during 3.17 seconds and there is no destruction taking place below floor 98! Only conclusion is that the upper part
IF there is a collision/impact it can only be between columns/floors, NOT columns/columns. You are right that the floors cannot stop the columns so the columns of the lower structure should destroy the floors of the upper part - but it does not happen! The floors of the upper part seems to have disappeared before that!
NIST has two suggestions; on the one hand the upper part
is a rigid box that crushes the structure below, on the other hand the upper part
is not rigid and 10 floors of the upper part
drop down and overload the top floor of the lower structure. In the latter case, the columns are not affected at all.
The collapse has everything to do with two ships colliding. Two structural assemblies contact and cause local failures to each other. And the momentum, energy and force involved in the WTC1 destruction are much less than at serious ships' collisions. Regardless, you have to check where the force and momentum are applied and what failures are caused by the energy available. Evidently the upper part
of WTC1 would have been seriously damaged or destroyed first, IF a collision took place. And a destroyed upper part
cannot drive a collapse.
It's like bouncing a ball on a floor! If the floor destroy the ball, well, that's it! The ball does not bounce any more!
The MacQueen/Szamboti paper is excellent. It explains really what happens 3.17 seconds prior any destruction of the WTC1 below floor 93 incl. the fact that no jolt occurs = no collision of any type takes place.
You know, when ships collide, you feel it as a jolt! Same when a ship is subject to a wave impact. BANG - you feel (and hear) it. Basic physics at work.