Once Again for the Physics Challenged
In order for a demolition's procedure to cause 8 storeys to go into free fall it would be required to remove the support NOT just of one or two storeys but all columns in all 8 storeys.(Seems to me I counted well over 100 required, very closely timed, severings)
This amounts to many dozens of cutting charges of some sort. Explosives will HAVE TO be large enough to sever these columns, some of which are quite large. A thermite melting is a slow process and cannot be timed.
Thermitic material used in an EXPLOSIVE will increase the heat output and the velocity of the expanding gasses which will still make a very very loud BOOM!
However, if the core columns failed, and they most certainly did as evidenced by the progression (yes Bill, it did progress) of central collapse seen at the rooftop prior to the collapse of the north face, then the cantilever trusses over the pre-existing Con-Ed building will have lost their major support at their south end. This would cause the lower 8 storeys to buckle outward(to the north) and at some point the remaining columns on the north side of the building would be basically useless with the vast majority of the weight above them no longer bearing anywhere close to axially on them.
SO, Nist says col 79 failed initiating a vertical progression(there's that word again Bill) at the location of col 79 and up to the roof where we see the east penthouse fall in. The debris from this vertically progressing (there it is again) failure is impacting proximate areas of the floors and columns and failing them resulting in a horizontal progression (wow its still there and we have not even gotten to the final 3 seconds of the collapse yet) which sees the core structure being badly damaged and failing.
Had this been a typical post and beam construction this might have ended there BUT it was far from that. The cantilever (look up that word) trusses were required to take the added weight of 40 more storeys and keep that added weight from crushing the Con-Ed structure. The existing columns of the Con-ed were bolstered as well but were never expected to have to hold the entire mass of 40 storeys. As progressive supports at the south end of the cantilever trusses fail, more and more mass is now being supported by columns never designed to do so. At some point during this horozontal progression
eye-poppi)of core failure the south most columns of the Con-Ed structure will fail adding more load to the remaining ones and so on, which means a very quick tilting of the cantilever trusses, the northward buckling of the north wall below the 8th floor and the essentially zero load bearing capacity of , now, radically tilted, and/or buckled, and/or snapped columns.
The rest of the building goes BOOM.
In fact had Bill or cmatrix bothered to peruse the thread discussing Chandler's use of the physics tool kit they would know by now that a period of free fall does indeed indicate very little(or nothing at all) about what caused the global collapse.
There IS one way for some nefarious planting of column severing devices to cause this to occur exactly as seen;
simply fail col 79 and then , progressively, the other core columns.
Of course you come right back to the problem of silent explosives or remarkably timed thermite severing of vertical structures.
