WTC Towers: The Case For Controlled Demolition  Hewlett Packard
This is a discussion on WTC Towers: The Case For Controlled Demolition  Hewlett Packard ; In this article we show that "topdown" controlled demolition
accurately accounts for the collapse times of the World Trade Center
towers. A topdown controlled demolition can be simply characterized
as a "pancake collapse" of a building missing its support columns.
...

WTC Towers: The Case For Controlled Demolition
In this article we show that "topdown" controlled demolition
accurately accounts for the collapse times of the World Trade Center
towers. A topdown controlled demolition can be simply characterized
as a "pancake collapse" of a building missing its support columns.
This demolition profile requires that the support columns holding a
floor be destroyed just before that floor is collided with by the
upper falling masses. The net effect is a pancakestyle collapse at
near free fall speed.
This model predicts a WTC 1 collapse time of 11.38 seconds, and a WTC
2 collapse time of 9.48 seconds. Those times accurately match the
seismographic data of those events.1 Refer to equations (1.9) and
(1.10) for details.
It should be noted that this model differs massively from the "natural
pancake collapse" in that the geometrical composition of the structure
is not considered (as it is physically destroyed). A natural pancake
collapse features a diminishing velocity rapidly approaching rest due
the resistance offered by the columns and surrounding "steel mesh".
DEMOLITION MODEL
A topdown controlled demolition of a building is considered as
follows
1. An initial block of j floors commences to free fall.
2. The floor below the collapsing block has its support structures
disabled just prior the collision with the block.
3. The collapsing block merges with the momentarily levitating floor,
increases in mass, decreases in velocity (but preserves momentum), and
continues to free fall.
4. If not at ground floor, goto step 2.
Let j be the number of floors in the initial set of collapsing floors.
Let N be the number of remaining floors to collapse.
Let h be the average floor height.
Let g be the gravitational field strength at groundlevel.
Let T be the total collapse time.
Using the elementary motion equation
distance = (initial velocity) * time + 1/2 * acceleration * time^2
We solve for the time taken by the k'th floor to free fall the height
of one floor
[1.1] t_k=(u_k+(u_k^2+2gh))/g
where u_k is the initial velocity of the k'th collapsing floor.
The total collapse time is the sum of the N individual free fall times
[1.2] T = sum(k=0)^N (u_k+(u_k^2+2gh))/g
Now the mass of the k'th floor at the point of collapse is the mass of
itself (m) plus the mass of all the floors collapsed before it (k1)m
plus the mass on the initial collapsing block jm.
[1.3] m_k=m+(k1)m+jm =(j+k)m
If we let u_k denote the initial velocity of the k'th collapsing
floor, the final velocity reached by that floor prior to collision
with its below floor is
[1.4] v_k=SQRT(u_k^2+2gh)
which follows from the elementary equation of motion
(final velocity)^2 = (initial velocity)^2 + 2 * (acceleration) *
(distance)
Conservation of momentum demands that the initial momentum of the k'th
floor equal the final momemtum of the (k1)'th floor.
[1.5] m_k u_k = m_(k1) v_(k1)
Substituting (1.3) and (1.4) into (1.5)
[1.6] (j + k)m u_k= (j + k  1)m SQRT(u_(k1)^2+ 2gh)
Solving for the initial velocity u_k
[1.7] u_k=(j + k  1)/(j + k) SQRT(u_(k1)^2+2gh)
Which is a recurrence equation with base value
[1.8] u_0=0
The WTC towers were 417 meters tall and had 110 floors. Tower 1 began
collapsing on the 93rd floor. Making substitutions N=93, j=17 , g=9.8
into (1.2) and (1.7) gives
[1.9] WTC 1 Collapse Time = sum(k=0)^93 (u_k+(u_k^2+74.28))/9.8 =
11.38 sec
where
u_k=(16+ k)/(17+ k ) SQRT(u_(k1)^2+74.28) ;/ u_0=0
Tower 2 began collapsing on the 77th floor. Making substitutions N=77,
j=33 , g=9.8 into (1.2) and (1.7) gives
[1.10] WTC 2 Collapse Time =sum(k=0)^77 (u_k+(u_k^2+74.28))/9.8 =
9.48 sec
Where
u_k=(32+k)/(33+k) SQRT(u_(k1)^2+74.28) ;/ u_0=0
REFERENCES
"Seismic Waves Generated By Aircraft Impacts and Building Collapses at
World Trade Center ", http://www.ldeo.columbia.edu/LCSN/Eq...C_LDEO_KIM.pdf
APPENDIX A: HASKELL SIMULATION PROGRAM
This function returns the gravitational field strength in SI units.
> g :: Double
> g = 9.8
This function calculates the total time for a topdown demolition.
Parameters:
_H  the total height of building
_N  the number of floors in building
_J  the floor number which initiated the topdown cascade (the 0'th
floor being the ground floor)
> cascadeTime :: Double > Double > Double > Double
> cascadeTime _H _N _J = sum [ ( (u k) + sqrt( (u k)^2 + 2*g*h))/g  k<[0..n]]
> where
> j = _N  _J
> n = _N  j
> h = _H/_N
> u 0 = 0
> u k = (j + k  1)/(j + k) * sqrt( (u (k1))^2 + 2*g*h )
Simulates a topdown demolition of WTC 1 in SI units.
> wtc1 :: Double
> wtc1 = cascadeTime 417 110 93
Simulates a topdown demolition of WTC 2 in SI units.
> wtc2 :: Double
> wtc2 = cascadeTime 417 110 77
By Herman Schoenfeld

Re: WTC Towers: The Case For Controlled Demolition
In schoenfeld.one@gmail.com writes:
>In this article we show that "topdown" controlled demolition
>accurately accounts for the collapse times of the World Trade Center
>towers.
[ snip of delusional rambling ]
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namely:
I'll provide you with a MetroCard and the address list
of the PBA (police union), UFA (firefighters), similar
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with all the people you are (mis)quoting or using
as reference data.
In fact, I'll splurge and pick up the costs for similar
transport on NJT and Metor North, thus giving you
the chance to go from New Haven to Trenton.
You game? Or are you a scaredy cat?

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