Reply #246: Various

[Kevin Fenton]

I also seem to recall venting on floors which are not mechanical floors.

Localisation
Generally the claim is that there were rows of explosives, so if this is a squib from an explosive, then it must be firing both out of sequence regarding the fall of the towers and indpendently of the other explosives on the row (unless there were no other explosives there because it was a mechanical floor, which might also explain why it was firing out of sequence, although I'm not sure how exactly).

If it's venting, should the venting be going down the towers as they fall, or both up and down?

Is there any reason to think that if the towers were demolished by explosives that there would be no venting?

Although I have not read every single page of the NIST report (didn't bother with the recommendations, etc.), I don't recall much (if anything) about wind load. They said the collapse was preceded by bowing in both cases. Why do you think the wind load is significant for the two towers, given the collapse initiation was supposedly different for both of them? Or do you think it might have been significant for just one of them?
I checked the seven factors decisive for the collapse of WTC 1 on page 34/88 and wind load is not mentioned there. Neither is it mentioned for WTC 2 on page 45/99. So they either didn't think about it or did think about it, but thought it was not significant.

The point with the 10 severed core columns in the south tower core is that the collapse (if it is a "natural" collapse) is a product of various factors (I'm aware this is a simplification): primarily the external impact damage to the perimeter columns and flooring (which is discernable from evidence), the damage to core columns and other members, fireproofing knocked off members and the heaping of combustibles (the last two factors help determine how the fire acts on the steel). NIST seems to have arrived at what I'll call "values" for these four factors given which the tower collapses after 56 minutes. If you think one of these "values" is too high, then surely you must think one of the others is too low, otherwise the tower would not collapse after 56 minutes, but after a longer time. For example, if less core columns were severed than NIST claims (but its claims regarding the other factors influencing the collapse are correct), it should follow that the tower would have stood for longer - say 10 minutes more for each extra column, for the sake of argument. So if you think 10 is a little high, which NIST estimate do you think is a little low? For example, do you think they underestimated the amount of fireproofing knocked off members?

Elements of the plane (e.g. engines and landing gear) clearly retained their ability to sever some columns even after crashing through the perimeter, but the right wing of United 175 (enigne and landing gear) only severed 2 further columns (in the permieter on the other side). NIST claims American 11 severed 6 columns in the north tower core (which it hit head on in the middle). United 175 was travelling faster than American 11 at the moment of impact and the core was closer to the south wall of the south tower than the north wall of the north tower, but the core columns got thicker the lower down they went. The figure of 10 seems more than a little high to me.

Why is the corner core column more significant? Because it's bigger than the others?
Why do you believe it was taken out by the plane? Which bit of the plane?

btw, According to NIST in addition to severing 10 core columns, United 175 also stripped 39 of them of their insulation, in some cases on multiple floors.