earnest research
galathaea
probably were those of bazant and zhou
they proposed the column collapse theory
which held that if one floor loses enough core column strength
possibly due the crash and fires
then that was enough to instigate a progressive collapse
in structures like the world trade towers
this is based on a basic inequality
if the energy released from the falling masses potential
during the fall of one story from rest
is greater than the energy used to pulverise and snap
the major structural supports enough to initiate lower story collapse
then the paper asserts
since next iterations mass and kinetic energy will be larger
it too will have enough energy to initiate lower story collapse
in the world trade towers
the center columns were the major structural support
and so if fire and collision were to lower
the central column's strength so one floor collapses
and that causes the impact to start another floor collapse
the process is necessarily complete
in their model
there is a basic separation into two components
an upper and lower
-----------
| | upper
| XXx |
XxxXXxxXXXxxx
XxXx XX Xx
| |
| |
| | lower
. .
. .
the lower response upon impact from upper
is modeled as a stiff spring
of stiffness approximately 71 GN/m
approximated from strength of lower columns
for the north tower 7
they calculate the upper mass as 5.8 x 10 kg
and make two calculations of overload ratios
at greatest 3.7m downward displacement on the stiff spring
an overload of 31
and initial impact overload of 64.5
whereas building infrastructure was built for 3-6 overload tolerance
( they state 2 and have been criticised for this biasing error )
however
in their fall time calculations
they discounted plastic energy losses
neglected all pulverisation energies
and neglected losses of mass from the upper section
from pulverisation and blowout
their initiation hypothesis requires at least 800 C temperatures
across the entire floor of collapse
which clifton and others have debated
and the fall will not distribute the load of the upper
in a single impact to spring response after the first floor collapses
as modeled in the paper
but crushes the bottom and distributes over an interval
cherepanov has shown that even excluding the plastic losses
even the standard pancake iterations must have geometric factors
of between '\/3 and greater to the fall time
and can be excluded by existing evidence of fall time
he suggests fracture waves
which would convert the initial impact into a progression of damage
that could effectively remove the dissipating forces
however
this model predicts a leading fracture pulverisation
and cherepanov incorrectly argues that this
would allow the building to collapse in the near free fall regime
the error is that the energetics still rob from kinetic
and much does not occur until we see it
any global impulse shattering is not seen
pulverisation process occur throughout the collapse
that energetic is taken from kinetic
no simulations using the accuracy of
for instance
sebastian and mcconnel's semiempirical finite element models
of steel, concrete, and composite structural elements
have been able to account such energetics and time-to-fall
it does not matter what mechanism of destruction is used
ultimately the fall time is purely an energetic calculation
a delta from initial to final state
that is why it is an interesting scientific mystery
to account for the collapse speed of the towers
&&&&&&&&&&&..
but the towers are only the more spectacular collapses of the day
and not the most interesting technologically
the fire safety journal has run a number of articles over the years
of tests at the cardington laboratory in bedfordshire
this facility features an 8-story steel building structure
on which fire tests are regularly performed
beam strengths at various temperatures are measures
slab response is observed
in october of last year for instance
wald, simoes da silva, moore, lennon, chladna, santiago, benes, and borges
reported on some local collapse tests
that have been suggesting that the physical structures
are performing better against fire than standard models
extreme temperatures of 1150 C were reached without local collapse
wtc7 has not had a published simulation for its collapse
yet it is a much more common and basic design
an october 2003 fire safety journal paper by usmani, chung, and torero
about some 2-d models of initiation for the tower collapses
mentions
" Although the Twin Towers themselves had sustained considerable
structural damage, WTC 7 which had not, also collapsed (being
the first recorded case of the collapse of such a structure
entirely because of fire). This poor response from composite
steel frame structures is not in accordance with the findings
of Cardington [1]. "
it is wtc7 that provides the most relevant information to engineers
because it is buildings like wtc7 that are more commonly built
yet most of the events of its collapse are unaccounted for
progressive collapse phenomena in steel frame buildings
has almost always initiated locally to a section
in small buildings with only one load bearing section
this is equivalent to complete collapse
but in larger structures this often means
only that local section collapses progressively through its vertical load
there are many examples from bombing and other concussive attacks
like the murray building in oklahoma
of these sectional failures
and even the two towers can be seen as single sectional collapses
due to the monofloor structure
when the progressive collapse is complete across multiple sections
this usually proceeds through a wave of sectional collapses
one section falls providing asymmetric loading
causing the neighboring section to then fall
and these progressions of sectional collapses
continue in a wave across the structure
a sudden complete catastrophic failure
for these common construction steel skeletons
is unknown outside wtc7 and unsimulated
earthquake and hurricane regularly produce only localised structural damage
in structures greater then 5 stories
and although there have been a number of lower level structure breakages
sometimes overturning the entire building
and collapsing it into neighbors
there is normally the major portion of skeleton still intact
even dissertations with good review of the field
like ruangtananurak nara's dissertation for the university of tsukuba
describes only local mechanisms for possible failures
where progressive collapse again occurs in sections
as observed outside wtc7
global analyses have so far failed to describe what was observed
|
~~~~~~~~~~..
there are legitimate structural engineering questions
still unanswered from the tragedies of the 11th, september 2001
and despite a vocal group who regularly attack questioning the collapse theories
there are major scientific and technological reasons to continue the questions
and there is even a greater reason why it is important to follow the debate
outside the research community
this is because there have been theories that do describe the collapses
those theories describe intentional collapse mechanism
through the use of explosives
which easily accounts all energetics
and it becomes extremely important to consider such possibilities
when it may be factions in the american government behind such mechanisms
this is something americans need seriously consider
is our government out of our control?
will our government work against us?
other governments get out of their populace's control
all the time
they are the aristocracies
the theocracies
the dictator monarchs
the privileged
americans cannot pretend that such investigations are foolish
or "crazy"
"unthinkable"
they happen
often
and operations like gladio show our government may hurt our friends
and ones we didn't know we were supposed to hate
and fund terrorist groups we were allegedly against
like the contras and the other bush
and now with many leaks of greater population surveillance
and greater use of marketing and propaganda
intentional misdirections regularly revealed
that indicate an us-them positioning by government structures
the comparisons with nazification
mostly surround this elitisation process of power
but each are their own distinct approaches to the process
as was stalinisation
showaism
or the yahyaine
things really can get out of our hands
they do often
and vigilance means
whether republican or anarchists or libertarian or guns and dope
all must understand the extent of america's own elitisation
these catastrophes must be investigated through the methods of science
developing mathematical models for prediction
and technology
so citizens can engineer a healthier america
if our air defense was vulnerable that day
what was the mechanism of that vulnerability
and what process changes have been made to resolve the vulnerabilities
and increase robustness of response
it is possible to open up process to inspection
without revealing secret data
that is the point of opensource cryptography
it is possible to investigate many horrible possibilities
without being "paranoid" or "senseless"
it is possible to to try to earnestly understand
when there earnestly are reasons to understand what is going on
is our process breaking?
how can we measure it?
--
-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
galathaea: prankster, fablist, magician, liar
quasi
wrote:
Yes, the energy required to break the support beams has to come from
somewhere.
If we assume the collapse of the supports for the lower floors is
completely explained by the impact of the falling floors, then the
energy required to break the lower supports must _subtract_ from the
kinetic energy of the falling floors.
Of course, there can be other sources of energy as well. For example,
the fires themselves are certainly a source of energy. Estimates would
be needed for these additional effects.
To my view, it's intuitive that there should have been visible
resistance. The apparent lack of such resistance calls for an
explanation. The analysis should be based on laws of physics, together
with potentially realistic quantitative estimates, as opposed to just
speculative handwaving.
quasi
Brian Whatcott
...
>To my view, it's intuitive that there should have been visible
>resistance. The apparent lack of such resistance calls for an
>explanation. The analysis should be based on laws of physics, together
>with potentially realistic quantitative estimates, as opposed to just
>speculative handwaving.
>
>quasi
A physics teachers' list [PHYS-L) analyzed a movie sequence of the
falling tower at the time - to tabulate the displacement of the top
story visible in the sequence with time. This was input to a non
linear regression, initially supposing a uniform acceleration.
There was a pause detectable as a sine wave
in the analytical waveform synthesis after one story, indicating a
square wave pause This gave the best fit to the data on hand..
Further pauses were so small as to be undetected by the technique.
Brian Whatcott Altus OK
galathaea
[...]
> Yes, the energy required to break the support beams has to come from
> somewhere.
>
> If we assume the collapse of the supports for the lower floors is
> completely explained by the impact of the falling floors, then the
> energy required to break the lower supports must _subtract_ from the
> kinetic energy of the falling floors.
>
> Of course, there can be other sources of energy as well. For example,
> the fires themselves are certainly a source of energy. Estimates would
> be needed for these additional effects.
>
> To my view, it's intuitive that there should have been visible
> resistance. The apparent lack of such resistance calls for an
> explanation. The analysis should be based on laws of physics, together
> with potentially realistic quantitative estimates, as opposed to just
> speculative handwaving.
i mentioned that i would post some of my basic calculations
and wanted to follow up
i will give some basic calculations for the towers
because those are easiest to find
but my real interest lies
in the many more interesting questions of wtc7
material pulverisation has a simple model
the increase in surface area due to breakage
is linearly proportional to the force needed to break
this type of model is a simple solid-state approximation
based on the observation that outside the atomic regime (>100nm)
area is proportional to the intermolecular bonds that must be broken
for concrete
a value i have seen is 100 J/m^2
when the area created is much larger than the original area
one can take as a first approximation just the total area of
particles created
and focus on getting a good understanding of particle sizes detected
with the assumption that spherical area approximation
gives a good first order term
( and roughness would increase such an estimate )
the mass of a tower's concrete was 7.5 x 10^7 kg
one way to help ensure that calculation does not bias too large
is to only account for the dust found outside the footprint
as that excludes the large pieces that include most of the original
surface area
and helps assure a lower bound
there are many studies on the sizes of these particles
because such data was necessary for the evaluation of health issues
of the mass of concrete
2/3 was in the footprint
and of the remaining third
7% was to 200m but outside footprint
11% was 200m to 400m
19% was 400m to 800m
37% was 800m to 1600m
and 25% was beyond 1600m
so total mass per tower outside 400m is
82% x 1/3 x 7.5 x 10^7 kg = 2.05 x 10^7 kg
it is known that 400m outside the footprint
95% of the dust particles were in the 0.3 to 20 micron range
with median of 3 microns
just taking the median value 3 microns as an initial guess
( accepting that the contributions from lower sizes are much larger
than the corrections from larger sizes
so we are still trying for a lower bound here )
surface area of 3 microns = 4 x pi x ( 3 x 10^(-6) )^2 =
1.13 x 10^(-10) m^2 / particle
and a particle will have volume 4/3 x pi x ( 3 x 10^(-6) )^3 =
1.13 x 10^(-16) m^3 / particle
now the density of concrete is around 1750 kg/m^3
so the volume of concrete in the > 400m region is
2.05 x 10^7 kg / 1750 kg/m^3 = 1.17 x 10^4 m^3
which gives the number of particles as
1.17 x 10^4 m^3 / 1.13 x 10^(-16) m^3/particles =
1.04 x 10^20 particles
and so the total pulverisation energy per tower is
100 J/m^2 x 1.13 x 10^(-10) m^2 / particle x 1.04 x 10^20 particles
=
1.2 x 10^12 J
already this is becoming a problematic calculation
because the potential energy of a tower
with center of mass at half height
is
m x g x h_center = 4.5 x 10^8 kg x 9.8 m/s^2 x 207 m =
9.1 x 10^11 J
and notice that the previous calculation does not account
more than 2/3rds of the actual concrete
or any of the structural steel breakage
or inelastic heating
and so on
i'll post steel numbers in a little while
quasi
The above are some very concrete calculations (just kidding).
But seriously ...
I'm not qualified to judge either the quantitative estimates or the
calculations, but this is the type of analysis that's needed to help
resolve the controversy.
However let me see if I understand the gist of it ...
(1) You make rough estimates for the amount of concrete pulverized and
dispersed, stratified by distance.
(2) Base on those estimates, you then estimate the energy required to
accomplish such the pulverization as approximately 1.2 x 10^12 J.
(3) You then estimate the potential (gravitational) energy of the
tower as approximately 9.1 x 10^11 J
So the immediate problem, based on your estimates, is that the
available potential energy is not enough to accomplish the
pulverization. But those numbers are roughly the same order of
magnitude. Still, even if we ignore the above deficit, there would be
no energy left to do anything else (for example, breaking the steel
beams).
>i'll post steel numbers in a little while
If the formulas require division, brace for some tough calculations --
dividing steel numbers can be difficult.
quasi
galathaea
> On 28 May 2007 12:23:58 -0700, galathaea <galath...@gmail.com> wrote:
>
> >i'll post steel numbers in a little while
steel is similar to concrete
but there is deformation to consider
in particular
one must account
- breaking of steel exterior columns
- bending/deformation of steel exterior columns
- breaking of steel interior core columns
- bending/deformation of steel interior core columns
- breaking of steel floor structure
- bending/deformation of steel floor structure
wierzbicki has given the value
6.19 x 10^7 J/m^2
as a typical value for the steel used
( there were actually 12 grades used
with a distribution of 30-100 ksi
but distributed asymmetrically throughout )
for the exterior columns at 0.0184 m^2 crossection
we can take this as best case transverse breakage
at 1.14 x 10^6 J/column
now the estimates i have seen
greenings for instance
use the assumption that all columns
were broke once every story
there was likely a spread
but i know from pictures
there were not more than a handful
of 2 or 3 story structures
so one story breaks seem a useful starting mean
with the above exterior column energy
and that there are 236 exterior columns
the calculation gives
1.14 x 10^6 J/column x 236 columns/floor x 110 floors
or
2.96 x 10^10 J
similarly for the 47 core columns
at 0.1236 m^2 crossection x 6.19 x 10^7 J/m^2
x 47 columns/floor x 110 floors
3.96 x 10^10 J
to maintain debris size distribution at the story level
for the acre-sized floors
this requires quite a number of breaks
to get pieces averaging 1 floor
with about 480 trussed cells per floor outside the core
if one break is assigned per cell
this gives breaks of about one per story length
the steel is the same grade as the exterior columns
so this is
6.02 x 10^10 J
now it is difficult to estimate deformation energies
but deformations must reach yield forces
just as breaks
and looking at some representatives
shows that representative beams did suffer measurable deformation
a very rough estimate can be taken by assuming
given a continuous span of column
it on average been damaged 3 times
by impulses 1/3 required to break
which is a simple visual and energetic model
there are better methods using
semiempirical energy distributions
but this basic heuristics gives a duplication
of all energies calculated so far
2.96 x 10^10 J towards deformations of exterior columns
3.96 x 10^10 J deforming core columns
6.02 x 10^10 J deforming floor trusses
all accounted
the steel energies total
2.59 x 10^11 J
or 28.5% of the potential energy
if we assume breakage that occurs
at angles not completely transverse
and try to take into account the spread of sizes
with smaller sizes contributing more as in concrete
then this may be a good lowerbound
and the actual value will likely be higher
but already again the value seems significant for fall times
quasi
I don't know if your analysis is right, however I think these
questions need to be asked.
Total near-footprint collapse in near free-fall time is a very
surprising phenomenon. It calls out for a scientific explanation.
Can the total energy required to explain what transpired be accounted
for by the energy of the fires plus the gravitational potential
energy? According to your calculations, the answer appears to be "no".
I'm not qualified to judge the validity of your results, but at least
you've provided actual numbers and calculations. Perhaps your
calculations can be disputed -- fine, but then let's see the critique.
In any case, as I see it, what you've done is far more valuable than
all of the various speculative claims, proclaimed confidently as if
they were facts.
quasi
galathaea
[...]
> questions need to be asked.
>
> Total near-footprint collapse in near free-fall time is a very
> surprising phenomenon. It calls out for a scientific explanation.
>
> Can the total energy required to explain what transpired be accounted
> for by the energy of the fires plus the gravitational potential
> energy? According to your calculations, the answer appears to be "no".
well
the answer is always open
one of the problems with these discussions
is that so many from each side
try to pretend the other side is "obviously wrong"
barriers to communication form
and no one considers what the other side offers
you have been very careful to avoid this
but it still occurs with others
and it is so damaging on all sides
in my opinion
these calculations show only this:
the current best theory of wtc tower collapse
is controlled demolition
that is all
it could change tomorrow
with some new demonstrated property of matter
allowing weak brittle collapse
but no such behavior has yet been demonstrated
> I'm not qualified to judge the validity of your results, but at least
> you've provided actual numbers and calculations. Perhaps your
> calculations can be disputed -- fine, but then let's see the critique.
> In any case, as I see it, what you've done is far more valuable than
> all of the various speculative claims, proclaimed confidently as if
> they were facts.
actually
quasi
i believe you are eminently qualified
many of us on the newsgroups
have seen you answer in-depth cohomology questions
following kernel relations
with the eye of an expert
by comparison
the physics requires a basic knowledge of units
and very simple geometric intuition
i have no doubt you have followed
i have also seen those with relevant degrees
make unsubstantiated leaps
that is the nature of this chaos
for posterity
it is more about the confidence
than it is about the result
which is sad
because the result is so important:
the current best theory of wtc tower collapse
is controlled demolition
that should make all americans think
Anthony G. Rubino
>galathaea
>
> the current best theory of wtc tower
>collapse is controlled demolition
>that should make all americans think
>
observations of previous uncontrolled demolitions?
I remember reading an article a long time ago that considered all the
then known principles of aerodynamics to prove that bees can't fly.
Tony, philosopher
http://www.geocities.com/trisector/
So many misconceptions, so little time.
galathaea
> >galathaea
>
> > the current best theory of wtc tower
> >collapse is controlled demolition
> >that should make all americans think
>
> How was the knowledge to control demolitions developed if not by the
> observations of previous uncontrolled demolitions?
>
> I remember reading an article a long time ago that considered all the
> then known principles of aerodynamics to prove that bees can't fly.
i believe that is almost an urban myth
or a telephone-game interpretation of a result in
a 1934 book by antoine magnan
but there are plenty of similar stories from actual scientific debates
lord kelvin made many ludicrous statements
about the impossibility of heavier-than-air flight
and so on
yes
science has controversies
science is controversy
it is the challenging of accepted beliefs
i was very interested in cherepanov's fracture wave model
and it is still possible that some related mechanism " solves " the
mystery
and it is very important for science to investigate such possibilities
however
it is also important for science to consider what current models are
suggesting
and it appears the subject matter may be important to others as well
..
when i first investigated this
i had a secret motive of money
this friend of mine
who coincidentally also regularly asks me about perpetual motion
ideas
was trying very hard to have me use my simulation engine
to make a model of wtc7
she eventually pointed out that since no one else
had published a simulation that worked to explain its collapse
that this could be my chance to make an entry into professional
simulations
and that is what convinced me to do some simulations
the idea was if the collapse progression was studied fully
it could give suggestions on engineering safer building
so i actually started trying to show how collapse was possible
because that is what would get noticed and show my simulations engine
was good
and i still think if anyone can write such a program
with valid scientific models controlling dynamics
it could make them money
but i couldn't do it
and neither has nist
or any other agency or simulations company
and when i have asked for access to the simulations done for the
towers
even though i have a degree in physics simulations
and have asked researchers for source access a number of times
before
i got nothing
its all so surreal
and of course
when the immediate response to 9/11 by the american government
was to foment the bloodlust of the event
into attacking an unrelated country
and doing very little to apprehend the stated perpetrator
i really don't know what to think
there were more soldiers on the ground hunting saddam in iraq
than hunting osama in afghanistan...
i don't know
i just want people to understand it is alright to ask questions
if we simply continue test our models and adapt when issues are
discovered
we will continue to learn
whatever way the questions are answered