Actually, I will go along with this statement. If explosives were planted to cause the top 14 floors of one of these towers to drop down onto the floor below, global collapse would be inevitable. It would also look a lot like what we see.
But you're not claiming that - you seem to be claiming that this resulting global collapse would not be sufficient to pulverize as much non-metallic material as we see being pulverized, therefore much more explosives were needed. Let's call this claim "T."
Our refutation of this claim is that if the gravitational potential energy (GPE) of just the falling building is not enough, it would take on the order of a million pounds of C4 be significantly greater than the building's GPE. Since there seem to be very few people kooky enough to believe that a million pounds of high explosives could have been used, your claim, claim "T," has been refuted.
The pulverized concrete and wall board, and other material, are a complete red herring. Why are we wasting our time with this? The transmission of dynamic load through out the weakened structure, and the serial dynamic loads can be modeled, but NIST didn't do it because their aim is to look at better building and structural methods for the future.
There has got to be some college professor somewhere who can assign to some of his grad students the modeling of the dynamic loads on each floor below the failed floors, and the serial effects.
What I am curious about is whether or not many lower floors, below say 40-50 50, didn't fail early due to the rapid serial transmission of massive impact loads, a vertical sheer load on a lot of attach points, bolts, and welds, throughout the structure. These shear loads would sever, not bend, the connections between the upright and horizontal members. At what point would load absorbtion lead to failure as and initiate a lower floor collapse in parallel after X number of floors above them collapsed one at a time.
Back to "just blow a few floors" theory.
This plan presumes that both aircraft were aimed at specific, but different by about 10 floors of separation, floors on each tower. The aircraft impact is aimed at providing a smoke screen, a cover up to the single floor demolition that was intended to trigger the collapse, top down, of the 12 or 20 story building section (the top of either tower) above undamaged floors. Also to trigger emotional outrage at rag heads, which I have been harboring since about the summer of 1979. (Teheran)
This destructive scheme would require analysis done during mission planning such that the detonation, by remote or by clock timer, is synchronized to the time-on-target aircraft attack, + XX minutes, and was rigged such that the trigger device would be protected from the initial impact damage/shock at > 90% confidence. Subsequent collateral effects, fires for example, could be assumed with a reasonale fuel load on any aircraft, and the plethora of combustible office materials in any office.
The next rational step is having more than one floor riggedto ensure (redundancy is part of any sound plan) that if one floor's rig was damaged or a pilot slightly missed the target floor (see the turning impact at WTC 2) a few other floors would still be available to be triggered, and thus the global collapse triggered. This all assumes away the seismic evidence against explosions.
Thus, none of the three-five floors that were initially hit, and thus explicitly targeted to be hit, could be rigged without risking the integrity of the explosive demolition. This raises the question: why not hit both towers at about floor 80-90, to ensure a 20+ story pile driver as the active destructive mechanism? You want it to work, you stack the odds for success in your favor.
Why the assymetrical destruction pattern? Well, silly me, to fool people into thinking amateurs pulled this off!

Muahahahahahaha!!!!
How many floors actually had to be rigged? Probably 4-6 per building, each begining a floor or two below the planned impact floor. How to dispose of the evidence of charges not detonated, the redundant charges? Rigging for such a task in floors below burning floors would not necessarily burn, so there might be considerable explosive left over for forensic analysis.
Where did it all go? Right, "plants" in the forensic analysis teams, all of whom cleverly secret away all traces of explosives found during rubble clean up.
No inadvertent explosions of c4 (or what have you) during rubble clean up? ?? ?? ??
What trigger mechanism, and what fusing would be needed? How would it be implanted without notice? How many months and weeks of various "maintenance workers" to slowly and methodically place these charges in corner offices, where big wigs worked?
Most of these witnesses would be presumed casualties: since dead men tell no tales, they'd not be available later for testimony, eh?

Oh wait, not everyone who works in every office was at work that day, eh? So, all the folks on floors rigged, below burning floors, who were either out of town, or were able to get out . . . they report no odd maintenance activity? They are all in on it? What?
Of all the conspiracy theories available, this would have a hope in hell of standing up (still requires suspension of disbelief on the rigging phase) in terms of the "aiding and abetting the weakening of the structure by impact, fire, and fire proofing coating" with a little nudge from some C4 or other suitable demolition material.
Seismic record still not answered, of course.
OK, I can come up with this off the top of my head in about 15 minutes. How is it that any CT advocate doesn't approach this with similarly rational analysis? Is it due to the overwhelming emotion involved in the CT position?
Look at how much more complicated their theories are than a simple, cold hearted analysis by someone whose profession included thinking about how to kill people and blow things up.
I am still at a loss to explain WTC 7 in this "plan," other than a planning assumption that enough junk would fall on all and sundry nearby buildings to ensure the kind of damage needed to initiate collapse, or permit Mister SilverSatan to appeal to the Port Authority when all the other rubble had cleared to demolish a bulding too far gone to be salvaged. He could go either way.
*scratches head*
Going into the mind of CT is a strange thing.
I'd rather drink a toast in honor of my fallen comrades at the Pentagon.
*raises a glass of Kentucky Boubon*
DR