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

[tomk52]

97. He does, but its irrelevant

I need to go thru them carefully. It's been awhile.

Most complete info in BLGB, JoM (2008)

Provisionally, IIRC...
Bazant uses free fall for his first story collapse. Measured acceleration, averaged over ~15 stories, was about 0.7g.

But the impact velocity, for a fixed distance drop, goes as (a)^0.5, which would be .85*(velocity if free fall). When you square the velocity to get kinetic energy (1/2 m v^2), you get right back to 0.7.

So, given an accel of 0.7G, the kinetic energy after 1 story free fall would be 0.7 times the kinetic energy attained in free fall.

But there are SO MANY factors that Bazant has introduced favoring collapse arrest**, and the overload factor is so great (multiple of 31, IIRC), that this small percent change is noise level.

If you look at BLGB, there are some curves that show timing of collapse compared to free fall collapse. You can see that slight deviations to acceleration at the start of the collapse will become irrelevant once the collapse gets moving.

I'll go thru these sometime in the next week & get back if I need to include any corrections.

tk

** biggest factors:
a. column on column impact. wholly impossible, but still "limiting case".
b. one story fall: The columns were built in 3 story lengths, they failed in 3 story lengths.
c. column stagger: huge impact. As the descending mass reached each floor, that floor had already lost >2/3rd of its supports because of the stagger, and the 1/3rd remaining was massively compromised.
d. Real failure mode was snapped welds & bolts, whose energy to break was ~1/1000th energy to buckle columns.