Reply #9: You mention the 'piledriver' effect

[DoYouEverWonder]

'Second, what we saw on 9/11 was the upper floors disintegrating and turning to dust, with concrete being pulverized at each floor-- such that there really was relatively little of a "piledriver" effect.'

That's right the floors apparently were pulverized and did not slam down on top of each other.

However, the collapses were designed to take advantage of existing objects, in order to create this piledriver effect. I believe this is why WTC 1 was hit at a higher point, then WTC 2. WTC 1 had the antenna and so they had to take this out first along with the hat truss that it sat on. This heavy object had no were else to go but down the center of the building. Then they blew out the first set of mechanical floors, then the 2nd set and then the core. Using the plumes of debris to cover up the sequenced blow outs on the way down.

In WTC 2, they didn't have this natural 'piledriver' so they needed to use just the elevator hoists that were on the 81st floor, so they had to start the collapse at the floor below, in order to take out these 24-ton weights first and then from there the same sequence of event occurred has in WTC1.