Some Misunderstandings Related to WTC Collapse Analysis

[Tony Szamboti]

Jeffrey, I call your attention to post #319. Lot's of stuff happened in between and you probably missed it.

I continue to ponder the Top Down cartoon in the light of your explanations.

Question: Tony and Jeffrey: common sense would dictate, to me at any rate, that the weakness in the core if great enough would pull the building down dragging down the floor joists and ultimately the roof. Why isn't this possibility, which seems to me to be the most compelling, put forth by NIST and Orling?

Think of another strange event. A person is standing comfortably on a level surface. Suddenly, his leg just below the knee disappears adding no momentum to his otherwise stable body. Why would he fall? According to NIST and Jeffrey, it would not be because he no longer is supported by his now missing leg. It would be because the load would be transferred via the pelvis to the other lag causing instability leading to collapse.

I say he falls because his leg is missing.

And I say the top portions of WTC 1 and 2 collapsed due to core weakness. What caused the weakness is what is at issue.

But once again, why did NIST and you, Jeffrey, or more correctly Major Tom, chose not to go this route?

Jeffrey, that's how I read your cartoon and understand both your words and those of NIST.

The core did pull down the building, but it wasn't because of weakness. There is no physical evidence of high steel temperatures on core columns and the rapid acceleration through the first story of the fall is too high for heat weakening induced buckling.

Of course, Jeffrey does admit the core went down first. His problem comes in when he attempts to say its load was transferred to the perimeter through the hat truss, which could not possibly do it, and the perimeter columns would not buckle under the addition of the core load as a purely vertical load.

NIST doesn't admit the core went down first, but say it had some level of failure due to heating causing it to expand and then buckle under the compression due to the heat caused expansion being constrained and causing partial load redistribution through the hat truss to the perimeter, which are nowhere near enough to cause perimeter failure. However, it isn't their primary failure mode. Theirs is truss sagging causing perimeter inward bowing leading to perimeter failure of the south wall, in the case of WTC 1. However, in that case the load redistribution wasn't enough to fail either the core or the adjacent perimeter walls. NIST seems to be trying to use a shotgun approach where everything fails a little bit, but they never do make a case where they have high enough combined redistributed loads to cause additional failures.

The reason both Jeffrey's and NIST's explanations are confusing is that they aren't real and there was nowhere near enough load redistribution to cause additional failure in their scenarios.

The real failure was due to something causing the core to fall other than heat and the falling core pulling the perimeter walls in through the floors causing them to buckle. The late Danny Jowenko showed how to do it at a little after three minutes into the video here http://www.youtube.com/watch?v=k3DRhwRN06I