Post by kirtlandPost by B1ackwaterPost by kirtlandPost by B1ackwaterPost by kirtlandOn Tue, 02 May 2006 19:07:10 GMT, Roedy Green
Post by Roedy GreenPost by B1ackwaterKeep believing that Roedy, just keep believing ...
It is not a matter of belief. In grade 11, I got the top mark in
North America on a physics exam. I still remember my grade 11
Newtonian physics.
That is the other reason I say those towers did not fall naturally.
Where can I find information on why WTC7 fell? Any government info
seems to have gone down the memory hole.
WTC7 fell because it was badly designed - the structure
was compromised by the need to span over existing
structures. This concentrated stresses. When the fire
progressed far enough - boom.
There were very few fires and they had not spread much. This can be
seen from different views of the building before it fell. It fell
straight down which is wierd because of its aspect ratio - the ratio
of height against width and length.
Consider too the earthquake-like effects of the nearby
towers falling. Not only was there a huge shake, but
the foundations themselves would have suffered since
the buildings were kind-of tied together by all sorts
of tunnels, tubes and even bedrock.
The fires weren't THAT weak either.
I've yet to see a slo-mo of that particular building
falling. I'm sure they're out there, I just never came
across one. Fair chance it didn't fall QUITE as
uniformly as you think.
It didn't fall in slow-mo. It fell at the same speed a rock would if
dropped of the top of a 47 story building.
I was referring to a slow-motion video of the collapse.
I've seen a regular-speed vid, but nothing slowed-down
enough to really get a handle on whether everything
went splat in one instant - suggesting the thing was
laced with explosives - or whether there was a primary
structural failure point from which everything else
proceeded. Lots of vid on the BIG towers, but WTC7
was kind-of "incidental" and under-reported.
Post by kirtlandPost by B1ackwaterA weakness of modern structures is that in order to cut
material requirements they depend a great deal on mutual
support between load-bearing structural components. If
one element goes, the rest suddenly become severely
un-braced or de-tensioned. Older "stack-o-bricks" buildings
were a bit different in that respect, each wall had to
be largely self-supporting. Look at pix of old medieval
castles ... one wall may have collapsed from war or
subsidence, but often three walls are still standing strong.
WTC7 was a boxed steel framed structure. All the bottom supports
needed to collapse at the same instant for the building to fall so
straight. If it started at one edge or corner, it would look more like
a domino effect traversing horizontally and would fall unevenly.
That's why I want to see the slo-mo ... what first seems
to be "one instant" may in fact be a complex, orderly
series of events that just SEEMED to happen all at once.
BTW, you CAN create the appearance of instant collapse in
such a structure - if a critical number of the hidden
central supports fail. A wave of collapse will move from
the center outwards. But, since the outer shell is the last
to go and the only part we can SEE, it APPEARS that the
structure just went 'plop' all at once.
And finally, as I mentioned before, WTC7 was an OBSCURE
building - worthless for propaganda purposes to both
terrorists and any hypothetical evil US or Israeli govt
conspirators.
Post by kirtlandBesides, there was a recorded TV interview that told the building was
"pulled" by the fire dept. How the firemen managed to get the
explosives downtown and installed in less than six hours is beyond me.
Well, six hours is a long time - although things WERE very
confused that day. Assuming they had explosives nearby they
COULD have retrieved them and installed charges at least on
some of the aforementioned central supports in order to
induce an 'implosion' of sorts.
However, I seem to remember rather a lot of firemen and
such being fairly NEAR the building when it went. Any
demolition team would have pulled everybody WAY back
before they pushed the button.
Post by kirtlandPost by B1ackwaterYou couldn't pull one wall out of the WTC towers and expect
them to stand for long. Indeed, they didn't. Parts that
relied on tension were left danglin' in the breeze, parts
the relied on constant compression found only empty space
beneath their feet. Then the remaining steel got softer ...
The heat wasn't enough to melt the internal massive box beams under
compression. The "official" version shows it was the bending of the
floor joists that connect the internal boxed core to the outside steel
cage.
They don't HAVE to "melt". Steel suddenly becomes MUCH more
plastic at just a dull red heat. Buy a Benz-o-Matic torch
and a strip of steel from your local "Home Depot" and do
some experiments. If you really want to be sophisticated
buy a 50 lb spring "fish scale" and one of those IR non-
contact thermometers too. Clamp about an 18" long piece of
the steel strip (a 1x1/8" is commonly availible) flatside
down so one end is in a vice and the scale pulls down on
the far end. Draw about 30 lbs of tension on it and then
proceed with the heating.
You will be able to see that the tension initially holds -
but then suddenly diminishes as the steel approaches the
point where it's visibly hot. If you've got an assistant
or computer aid you can plot the temperature against the
percentage-strength-remaining. By the time you're at dull-red,
the steel can be folded double quite easily. At red-red it's
pretty floppy and can be formed easily with hand pressure
or a hammer. (Great-grandpappy was a blacksmith)
I encourage you to actually DO the hands-on experiment. However
if you MUST cheat, below is some of what you'd expect to see -
A handy guide to temperatures and other steel stuff is at :
http://www.threeplanes.net/toolsteel.html
And this from a fire faq :
http://www.corusconstruction.com/en/company/business_units/fire_engineering_home/who_is_fire_engineering/faq/
For hot rolled structural steel the yield strength reduces as the
temperature increases dropping to about 60% of its ambient
temperature strength at around 400°C and approximately 10% at
800°C. However the stress at 2% strain (normally reached when a
steel floor beam attains its permitted limit of deflection)
initially increases with increasing temperature reaching a peak
value at around 250°C. The reason for this can be explained using
metallurgical theory and involves a combination of work hardening
and dynamic strain ageing.
More info at :
http://irc.nrc-cnrc.gc.ca/fulltext/nrcc41506.pdf
Figure 4 is of relevance here.
And the WTC floor joists were steel too.
Remember also that there was some concrete in that building, in
the floors especially, and that provided stiffening between the
steel structural beams. As the steel gets hotter, it EXPANDS
and can CRACK the concrete (an insulator, so it doesn't heat
up at the same rate). This further weakens the entire structure.
About 15 minutes before the first tower fell, the TV images
showed how the section above the damage had actually settled
down a bit, slightly tilted, where the damage was greatest.
That meant the remaining weight was being held up by relatively
few beams - they were under a LOT of stress, both end-on and
in terms of lateral deflection. The upper floors were rather
like a long balcony, sticking out over a void, held up only
at the far end.
As the beams nearest the center failed, the remaining beams
had to hold more and more of the weight at a less and less
advantageous angle. Then there was an abrupt failure and the
far end plopped down all at once - a powerful blow striking
several lower floors compromised by impact damage and heat -
starting the chain-reaction collapse. Once everything was in
motion, nothing in that building was strong enough to stop it.
No explosives or thermite charges required.
A lot of people seem to think tall buildings should fall OVER
like a tree and this misleads them terribly. The WTC towers
were NOT trees, their structural strengths and weaknesses were
MUCH different and thus they FELL differently. Even if the base
of the tower had been blasted out, the rest STILL would have
fallen almost straight down.
Post by kirtlandPost by B1ackwaterPost by kirtlandPost by B1ackwaterActually WTC7 is pretty good evidence AGAINST a vast
konspiracy. It was a (relatively) small and hidden
building. Unless you worked in the area you probably
didn't even know it was there, or part of the WTC
complex. As such it had NO propaganda value - either
for bin-Laden OR a vast right-wing konspiracy. Only
the two BIG buildings were important.
What were the offices in that building?
Irrelevant. As it was not targeted by an airliner there was
plenty of time to grab the backup disks, lock the safes and
evacuate the building.
I found some very interesting material here.
http://911research.wtc7.net/mirrors/guardian2/wtc/WTC_ch5.htm
Post by B1ackwaterPost by kirtlandPost by B1ackwaterPost by kirtlandAre there any sites that explain the "pancake effect" AND take into
consideration the fact that the towers were mostly supported by the
internal core and NOT the outer steel framework?
The outer frame served as a 'guide' for the collapse,
tending to channel forces inwards toward the center.
The pancaking was expected, indeed the building was
designed to fall that way if it ever DID fall.
Your answer doen't answer my question.
You've kinda asked a lot of questions ...
As for web sites ... use Google and search for yourself.
The BEST solution is to get access to professional
structural design software. Plug in the parameters
for the towers and then simulate the damage and
loading situation.
Are the structural drawings available? Everything I've read tells me
they're not.
They USED TO be public-domain ... filed with the NYC building
department. Many copies must have been made before the first
terrorist attack in the basement garage. Any contractor bidding
on any sort of repair or maintenence deal would have pulled a
copy so they'd know what they were dealing with. The data is
"out there" somewhere - many somewheres. Now that the buildings
are no more, there's no point in keeping the designs secret.
Post by kirtlandPost by B1ackwaterPost by kirtlandPost by B1ackwaterPost by kirtlandIf anyone here has walked around the ground level concourse of the
trade towers, you will realize the above.
You'd realize that WTC7 wasn't WORTH anyone knocking down.
What were the offices in that building?
Again irrelevant. They lived. The hit was very indirect.