Originally Bazant, using his pile-driver theory of collapse of the Twin Towers, glibly asserted that the top block would remain rigid and act as a hammer, destroying the lower unheated, undamaged portion of the tower, storey by storey. When that was finished the top block would destroy itself. He called the first phase “crush down” and the second phase “crush up”.

As already stated, this explanation must be false as his “crush down” phase flies in the face of the observed disintegration of the top section before the lower section started to move. The “hammer” is destroyed before it strikes! His explanation also fails to take into account Newton’s third law, which states that the forces between two contacting objects will be equal and opposite. We can deduce from this that if the impact is sufficient to destroy the upper storey of the lower section it will also destroy the lower storey of the upper section. Apparently Bazant became troubled by criticism of his earlier work and in 2008 brought out a paper which made a number of adjustments to his original explanation.

Firstly he backed away from his earlier assertion that a temperature of 800 degrees C occurred. Instead he made claims that viscoplastic creep could cause failure when substantial loads were applied for long periods at moderate temperatures. He was hoping this would would get him past the obvious lack of evidence for 800 C to initiate the collapse. This is clearly far-fetched as we have a photo showing a woman leaning against a column shortly before the building collapsed. The steel could not have been more than comfortably warm, at which temperature viscoplastic creep would not be significant. Even if the core, out of sight, had been red hot at that time (and there is evidence indicating otherwise from NIST’s steel samples from the fire-damaged region) the outer columns, with a design safety factor of 5, would have held the building up by themselves.

Secondly Bazant allows that at the first impact there will be some effect on the upper block but asserts that it will be negligible and that only the lower portion of the building will be damaged in the crush down phase. He is thus still denying that Newton’s third law will be operating.

Following further criticism of his work Bazant brought out yet another paper in 2010 which again asserted that the damage above the impact interface would be small. We will look into this more closely. Imagine for a moment the scene which Bazant sets for the north tower: the columns separating two floors have buckled and the upper section is falling. At the bottom of the falling section is floor number 98. At the top of the lower section is floor 97. When these two floor contact, the force due to deceleration will be applied downward against the structure below and upward against the structure above. It has been argued that the downward force will be larger as it will be augmented by gravity acting on the mass of the debris in the buckling region. This is a false argument because it ignores inertia. During the approach to impact, and during the impact itself, the debris in the buckling region has to be accelerated downward. The force required for this acceleration diminishes the forces generated in the impact. That is all it does. There is no augmentation of the downward force due additional mass. The additional mass is distributed equally over both the descending and stationary surfaces. If it provides a cushioning effect it will be equal for both surfaces.

The storey above will have been heated more by the fires than the storey below and the columns in the storey above may be thinner by design as they are higher up in the building. Clearly if any buckling occurs it must be observed in the weakened falling upper block. Videos show that the upper block does disintegrate before the lower structure starts to give way. Any theory based on a hammer-like action of the top block on the lower section of the building is thus proved false. Discussion should stop at that point and an alternative explanation for the collapse of the upper section should be sought.

For the sake of argument however, let us imagine that explosives were not employed to cause the observed disintegration of the upper part of the building and that it did not disintegrate but fell as a block, in accordance with Bazant’s claim, acting like a hammer. Let us further suppose that the successive impacts were sufficient to destroy the supports of the lower, undamaged portion of the building, as Bazant claims. From the argument set out above we know that if the lower structure is destroyed by the impacts the upper, falling section must also be destroyed in the same way. In fact it would be preferentially destroyed.

As the second impact is approached the situation is different from the first impact in that the columns of two storeys must buckle, one above and one below the region where the first buckling took place. The first buckling was between floors 97 and 98. These floors, together with the remnants of the columns previously holding them apart, will form a mass of material which Bazant likes to call “Zone B.” During the second impact this material will be augmented by material between the next two floors, 96 and 99. The volume that would be defined as Zone B will alternately contract during compression and expand due to collecting additional floors. It is important to note that these two sets of buckling columns will be involved in progressive collapse; “everything will not be instantaneous” (to borrow a phrase from Shyam Sunder, a NIST team leader). During each collapse the force required to continue the progressive buckling will be approximately equal above and below Zone B, hence its centre of mass will be held roughly halfway between the upper and lower structures.

Here is where Bazant applies a conjuring trick. He asserts that Zone B will fall in contact with the top section and will provide a cushion, thus protecting it from further impact damage. This sounds reasonable until one recalls that Zone B was not simply in contact with the top section but was spread between the upper and lower sections. It would be as much in contact with the lower section as the upper section. Its cushioning effect will therefore be felt equally by both sections. Newton’s third law will of course apply at this impact, as it did at the first. Let us continue to ignore the fact that the upper section is weaker and more likely to collapse than the lower section and assume the columns above and below Zone B collapse equally. At each subsequent impact exactly the same thing will happen and both the falling top block and the structure below will be shortened by one storey. As there were only 12 storeys in the top section to begin with, the collapse must soon come to an end, due to its weight diminishing and the cushioning effect of Zone B increasing. A Bazant-style collapse below floor 84 is impossible.

Dissatisfaction with Bazant’s explanations has been widespread. Numerous writers have pointed out their failings, as can be seen in the Journal of 9/11 Studies and elsewhere. The most recent is a paper by Tony Szamboti and Richard Johns, submitted to the Journal of Engineering Mechanics (JEM) in May, 2011. Without touching on the mechanistic impossibility of the Bazant pile-driver concept, they dispute his paper by showing that it contains several incorrectly calculated inputs and thus cannot produce a correct result.

Here we find something rather surprising, interesting and, if it continues much longer, highly unsatisfactory: the paper has still not been published. Could it be that Bazant is finding it impossible to refute the work of Szamboti and Johns? Could the JEM be deliberately stalling to protect Bazant?

This particular journal has certainly been shown to be biased against fair treatment of 9/11 arguments in the past. James Gourley provides a thorough discussion of his experience at 911Blogger.