North Tower Acceleration

[jesters]

176. Okay I misunderstood about the double entry

But here was Seger's original statement:

"He had one line item for the energy lost in the inelastic collision and another line item for the energy required to fracture concrete."

The line item for concrete is for energy required to pulverize concrete. Pulverization and fracturing are not the same thing.


Greening seems to make a difference between fracture energy and that required to pulverize:

"...Because a single particle crushed into smaller particles exhibits a larger surface area, we need to multiply the fracture energy of 100 Joules/ m2 by the total surface area of the crushed particles to determine the minimum energy required to produce the crushed
particles. It is a minimum energy because we are neglecting any possible kinetic energy of the crushed particles in cases where particles are violently ejected from the original sample by the impact."

He also distinguishes between fracture and yield energy:

"...Ee(steel) is the elastic strain energy stored by the structural steel up to its yield point.
Ee(concrete) is the elastic strain energy stored by the concrete up to its yield point.
Ep(steel) is the plastic strain energy dissipated by buckling of the structural steel.
Ef(concrete) is the fracture energy associated with the crushing of the concrete...."

http://www.911myths.com/WTCONC1.pdf

Perhaps it's the yield energy that is found in the initial momentum loss and fracture energy needs to be accounted for on top of this.

"... As expected, the plastic strain energy dissipated by the buckling of columns (284 MJ) is confirmed to be the largest drain on the kinetic energy driving the collapse but clearly the energy to pulverize the concrete is comparable in magnitude..."