WTC Towers: The case for controlled demolition

WTC Towers: The case for controlled demolition
By Herman Schoenfeld

In this article we show that "top-down" controlled demolition
accurately accounts for the collapse times of the World Trade Center
towers. A top-down 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 pancake-style 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 top-down 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 ground-level.
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 (k-1)m
plus the mass on the initial collapsing block jm.

[1.3] m_k=m+(k-1)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 (k-1)'th floor.

[1.5] m_k u_k = m_(k-1) v_(k-1)


Substituting (1.3) and (1.4) into (1.5)
[1.6] (j + k)m u_k= (j + k - 1)m SQRT(u_(k-1)^2+ 2gh)


Solving for the initial velocity u_k

[1.7] u_k=(j + k - 1)/(j + k) SQRT(u_(k-1)^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_(k-1)^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_(k-1)^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 top-down demolition.
Parameters:
_H - the total height of building
_N - the number of floors in building
_J - the floor number which initiated the top-down 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 (k-1))^2 + 2*g*h )


Simulates a top-down demolition of WTC 1 in SI units.

wtc1 :: Double
wtc1 = cascadeTime 417 110 93

Simulates a top-down demolition of WTC 2 in SI units.

wtc2 :: Double
wtc2 = cascadeTime 417 110 77

Your tinfoil hat is Too Tight its cutting the blood from your brain and
making you post Nonsensical BS thats not even true.

On Sat, 9 Feb 2008 05:41:41 -0800 (PST),
wrote:

WTC Towers: The case for controlled demolition
By Herman Schoenfeld

snip


http://zapatopi.net/afdb/
---
Peter

Who's this conspiracy nutcase?

wrote in message
...
WTC Towers: The case for controlled demolition
By Herman Schoenfeld

In this article we show that "top-down" controlled demolition
accurately accounts for the collapse times of the World Trade Center
towers. A top-down 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 pancake-style 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 top-down 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 ground-level.
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 (k-1)m
plus the mass on the initial collapsing block jm.

[1.3] m_k=m+(k-1)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 (k-1)'th floor.

[1.5] m_k u_k = m_(k-1) v_(k-1)


Substituting (1.3) and (1.4) into (1.5)
[1.6] (j + k)m u_k= (j + k - 1)m SQRT(u_(k-1)^2+ 2gh)


Solving for the initial velocity u_k

[1.7] u_k=(j + k - 1)/(j + k) SQRT(u_(k-1)^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_(k-1)^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_(k-1)^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 top-down demolition.
Parameters:
_H - the total height of building
_N - the number of floors in building
_J - the floor number which initiated the top-down 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 (k-1))^2 +
2*g*h )


Simulates a top-down demolition of WTC 1 in SI units.

wtc1 :: Double
wtc1 = cascadeTime 417 110 93

Simulates a top-down demolition of WTC 2 in SI units.

wtc2 :: Double
wtc2 = cascadeTime 417 110 77

There is no way that a bilting where thousands worked every day could
be prepped for demolition with no one noticing. I am serious, find
anyone that ever did demolition and ask them how tough it is to
prepare a building. It can take months of partly cutting columns,
stripping furniture, cutting concrete, etc.

The 9/11 "internal demolition" conspiracy theorists have their heads
in the sand when it comes to reality.

On Feb 9, 2:00*pm, "David E. Powell" wrote:
There is no way that a bilting where thousands worked every day could
be prepped for demolition with no one noticing. I am serious, find
anyone that ever did demolition and ask them how tough it is to
prepare a building. It can take months of partly cutting columns,
stripping furniture, cutting concrete, etc.

The 9/11 "internal demolition" conspiracy theorists have their heads
in the sand when it comes to reality.

No, no! Two huge planes filled with combustible fuel had nothing to do
with it! Can't you see??

On Feb 9, 3:50*pm, "Jeremy Q." wrote:
"David E. Powell" wrote in news:e414af78-4bf3-
:

The 9/11 "internal demolition" conspiracy theorists have their heads
in the sand when it comes to reality.

It's seven years after the fact and you're *still* replying to every 9/11
conspiracy thread that gets xposted to risparew. There's clearly something
about the issue that has captured your imagination, just as it has theirs.

Because someone has to point out fallacy lest future people believe
the nonsese. It is the same reason there are organizations dedicated
to record keeping about the Holocaust, the Nanking massacre, etc.

David E. Powell wrote:
On Feb 9, 3:50�pm, "Jeremy Q." wrote:
"David E. Powell" wrote in news:e414af78-4bf3-
:

The 9/11 "internal demolition" conspiracy theorists have their heads
in the sand when it comes to reality.

It's seven years after the fact and you're *still* replying to every 9/11
conspiracy thread that gets xposted to risparew. There's clearly something
about the issue that has captured your imagination, just as it has theirs.

Because someone has to point out fallacy lest future people believe
the nonsese. It is the same reason there are organizations dedicated
to record keeping about the Holocaust, the Nanking massacre, etc.

the evidence of the holocaust wasnt immediately recycled.
though the german govt sure tried their best to do it.

now, where are the orgs devoted to record keeping about the truth of
the reichstag fire and documented pretext operations like
"northwoods"?

you are trying to whitewash the truth for future generations. the
american revolution was for nothing

Terry Austin wrote:

"David E. Powell" wrote in news:e414af78-4bf3-
:


There is no way that a bilting where thousands worked every day could
be prepped for demolition with no one noticing. I am serious, find
anyone that ever did demolition and ask them how tough it is to
prepare a building. It can take months of partly cutting columns,
stripping furniture, cutting concrete, etc.

The 9/11 "internal demolition" conspiracy theorists have their heads
in the sand when it comes to reality.


That's a polite way of saying "they're mentally ill and retarded."

I was sworn to secrecy but I'm now speaking out. I was one of the
contractors that put up the twin towers and we prepared them for
demolition as we built them. The plan was to bring them down about 25
years later.

Contractor Bob wrote in
:

Terry Austin wrote:

"David E. Powell" wrote in
news:e414af78-4bf3-
:


There is no way that a bilting where thousands worked every day could
be prepped for demolition with no one noticing. I am serious, find
anyone that ever did demolition and ask them how tough it is to
prepare a building. It can take months of partly cutting columns,
stripping furniture, cutting concrete, etc.

The 9/11 "internal demolition" conspiracy theorists have their heads
in the sand when it comes to reality.


That's a polite way of saying "they're mentally ill and retarded."

I was sworn to secrecy but I'm now speaking out. I was one of the
contractors that put up the twin towers and we prepared them for
demolition as we built them. The plan was to bring them down about 25
years later.

Yeah, and if pixies flew out of your ass, you could fly.

--
Terry Austin
"Dude, we're all your bitch, but only Ken's wearing the juice."
- tussock

"Just throw a rock, and what screams will probably be a moron."
- Elvis (no, not that Elvis)