Martin Sheen: 9/11 Questions 'Unanswered,' Building 7 'Very Suspicious'

[William Seger]

98. Bazant doesn't actually use any estimate of the acceleration in his analysis

This is from the first 2002 paper:

The downward displacement from the initial equilibrium position to the point of maximum deflection of the lower part considered to behave elastically is h (P/ C) where P maximum force applied by the upper part on the lower part and h height of critical floor columns height of the initial all of the upper part 3.7 m. The energy dissipation, particularly that due to the inelastic deformation of columns during the initial drop of the upper part, may be neglected, i.e., the upper part may be assumed to move through distance h almost in a free fall (indeed, the energy dissipated in the columns during the fall is at most equal to 2 pi times the yield moment of columns, times the number of columns, which is found to be only about 12% of the gravitational potential energy release if the columns were cold, and much less than that at 800°C). So the loss of the gravitational potential energy of the upper part may be approximately equated to the strain energy of the lower part at maximum elastic deflection. This gives the equation m g {h + (P / C)} = P^{[font size=1]2[/font]} / 2C in which m mass of the upper part of (North Tower) ~5810 kg, and g gravity acceleration. The solution P = P_{[font size=1]dyn[/font]} yields the following elastically calculated overload ratio due to impact of the upper part:

P_{[font size=1]dyn[/font]} / P_{[font size=1]0[/font]} = 1 + sqrt(1 + (2 C h / m g)) ~ 31

where P_{[font size=1]0[/font]} m g = design load capacity. In spite of the approximate nature of this analysis, it is obvious that the elastically calculated forces in columns caused by the vertical impact of the upper part must have exceeded the load capacity of the lower part by at least an order of magnitude. {Emphasis added}

So, the "almost in a free fall" part is really an inference based on the primary assumption: "The energy dissipation, particularly that due to the inelastic deformation of columns during the initial drop of the upper part, may be neglected." If anyone wants to argue that the fall was significantly less than free fall, then they have to give some reason for believing there was a significant amount of energy dissipated in that initial deformation, because the crux of Bazant's argument is that the lower structure must absorb the remaining energy in order to halt the collapse. The analysis does not attempt to actually quantify the acceleration of the fall and then, for example, to use that to calculate an impact velocity and then use that to calculate the kinetic energy. Rather, he is going for a more direct estimate of the gravitational potential energy released and comparing that to the energy that could be absorbed. "Almost free fall" is really the result of there being a large disparity between the two, according to Bazant, not the other way around. Anyone who thinks that's the flaw in Bazant's argument is free to attempt to refute it, but that would need to be done quantitatively, using actual structural mechanics and actually addressing Bazant's technical argument, not just by asserting it's wrong.

The salient point is that if conspiracists like Gourley and Bjorkman want to find fault with Bazant's analysis, then they must begin by either finding significant energy sinks that he does not include or by finding major faults in his energy estimates. They did neither, and arguing about the difference between "free fall" and "almost free fall" is a red herring. And since Bazant is already assuming conditions that would tend to maximize the energy absorbed, that's going to be a tough row to hoe. Gourley and Bjorkman are spectacularly bad examples of any serious attempt, as Bazant was gracious enough to phrase politely in his Closures.