One must assume the building wasn't on fire at the time the explosives were placed. Had to have been the weeks and months before.
And you are going to tell us that explosives technicians are going to go into a building next to one of the most powerful transmitter signals in all of NYC, possibly in the country and set blasting caps without shutting down those transmitters for the duration of the operation. Riiiiight.
I aint gettin on board with that outfit.
Then there is the problem that every form of explosives that I know of burn or melt when exposed to the kinds of temperatures that prevailed over several floors of the buildings. In the towers, those temperatures far exceded what would be needed to destroy the charges on precidely those floors on which the charges that initiated the collapse sequence. In WTC7, the fires were observed to be in flash-over, thus well over the temperatures needed to destroy the charges in places over more than long-enough periods. After the whole south face was ventilated by ballistic impacts, the locations of the fires was entirely a matter of random chance. This is totally not conducive to the sort of precise planning that would be needed to take out exactly the right columns.
Then there is the problem of disguising what they had done. There were a lot of cops and fire fighters and iron workers looking at the steel in the rubble pile. Many, if not most of them, would have had military experience, many in fields in which they would have gained some knowledge of the effects of demolitions charges. That none of them saw anything consistant with such blast effects implies that it is highly unlikely that any were there.
Further, charges adequate to take out a steel column would also have taken out the glass over entire floors all around the building. The only glass observed breaking between the impact of the tower on WTC7 and the initiation of collapse was the result of fires. Nearly all of the glass on the north side remained in tact until after the wall had started to buckle, long after the mechanical towers had fallen into the interior of the building. I see no way that this would be possible, given the over-pressurization of the structure which would neccessarily have followed the detonation of charges. Perhaps one might think that the vast gash taken out of the front might have relieved this over-pressurization, but that would also have amplified the horrendous explosives sounds of the detonating charges like a fire cracker in a paint can.
There is an absence of evidence for explosives and a mountain of evidence of their absence.