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WTC7 and the girder walk-off between column 79 and 44

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You don't believe that someone could come up with James Quintiere, Les Robinson, Tom Eager, several names from AiA, SEoNY, Purdue, LERA Associates, Weidinger Associates, etc. etc. etc
No, no. List the names please.

ETA: Quintiere
"Little did I realize that the NIST heart was not in it, and its efforts would not be proactive, but reclusive. While NIST had public hearings during the course of discharging their findings, they were limited to 5-minute presentations by the public, and no response to submitted questions or comments. There was no transparency of their effort, and even their Advisory Board did not know when they would finally release conclusions until October of 2004.

In October of 2004 their conclusions on the cause of the building collapse was a surprise to me. While I can find issues with their investigation of the event in assembling information through the lack of calling witnesses, issuing subpoenas, and applying normal proactive legal processes, I will primarily focus on the issues related to the fire and the collapse of WTC 1 & 2.

Specifically I will demonstrate why I believe the NIST conclusion is deficient and I will offer an alternative conclusion. The significance of these two conclusions is significant, as it bears on the responsibility for the collapse of the towers. The NIST conclusion essentially puts the primary cause on the impact of the aircraft, while the alternative conclusion lays it at the feet of fire safety design. The correct answer bears on the practice of fire safety.

The NIST investigation was done in virtual secrecy with periodic hearings to give progress. It was not until October in 2004 did NIST present a conclusion. Up until that time, it was not clear what they would conclude. NIST has not responded to written questions

"What is lacking from NIST is a clear account of the logic they used in explaining the collapse mechanisms. It is one thing to state the cause and imply their computation by computer codes; it is another to clearly illustrate the physics behind the collapse mechanisms."

"The stripping of the core column insulation is critical to the NIST conclusion, and without it they cannot get the buildings to collapse. No scientific justification was give for the stripping except that it was in the path of the aircraft.


Pretty incompetent response, Tony.

Why would a competent engineer give a rat's ass about what you believe "counts".

How many incompetent, identified engineers is one competent anonymous engineer worth, Tony?

You think that this citation shows anything but stupidity, Tony?
Total lack of respect for and adherence to Rule 12 noted.

Unfortunately for your Appeal to Amateur Laziness, it took video analysis and a little calculus to figure out that it was NOT "coming down uniformly at freefall acceleration."
That is an erroneous interpretation of the data that only the fanatically faithful on this forum support.

What distinguishes competent engineers from incompetent ones is the tools & analyses that we use.
Real engineers give their real names and credentials. You are just an anonomous poster and not an engineer - except in your own mind.
 
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Its not my misinterpretation, its from femr2's accurate analysis. And yes, it is possible if the falling structure inside is yanking down the exterior.
Possibly, but only for the first split second. Once the things falling at slightly different speeds equalize, everything is falling at the same acceleration and there are no internal forces, nothing pulling on anything else.
 
Bolding mine...

Once the things falling at slightly different speeds equalize, everything is falling at the same acceleration and there are no internal forces, nothing pulling on anything else.

Your terminology is bizarre.....care to rephrase whatever point you are pretending to make?
 
The upper portion of WTC 7 fell AT FFA for about 100 feet. Even if your misinterpretation of the data points were correct, the average was still FFA and that is not possible unless all the supporting structure is removed. Buckling columns provide resistance as Sunder said at the Tech Briefing and Bazant showed in Fig. 5d of his 2002 paper.

[qimg]http://img213.imageshack.us/img213/7157/bucklinggraphics.jpg[/qimg]
You "forgot" the text that accompanies the illustration:
[...] which defines the curve plotted in Fig. 5. This curve is an optimistic upper bound since, in reality, the plastic hinges develop fracture (Bazant and Planas 1998), and probably do so already at rather small rotations.
That's dishonest.
 
So why didn't the the building, after the failure, fail/fall in the path of least resistance?

Hope Horatius doesn't mind...
well-duh.png

(Credit: Horatius)
 
So why didn't the the building, after the failure, fail/fall in the path of least resistance?

Because it would have needed even more resistance to make all that debris shunt off sideways. The path of the collapse was the path of 'least resistance' (if we absolutely must use that damn phrase).

The Horatius cartoon, though, is much funnier :)
 
You "forgot" the text that accompanies the illustration:
[...] which defines the curve plotted in Fig. 5. This curve is an optimistic upper bound since, in reality, the plastic hinges develop fracture (Bazant and Planas 1998), and probably do so already at rather small rotations.
That's dishonest.
No, this is the only data on buckling that I know of. Bazant does not say how much the fracturing would affect the resistance curve and he does not suggest that it could suddenly go to zero.

The exterior columns were typically W14x500. The flanges ares 17" wide and 3.5" thick. The Web is 2.19" thick and the column is 19" high.

These columns were held together with moment frames so they were mutually supporting each other.

To suggest that they would snap like sticks is baseless and erroneous.
 
Because it would have needed even more resistance to make all that debris shunt off sideways. The path of the collapse was the path of 'least resistance' (if we absolutely must use that damn phrase).

The Horatius cartoon, though, is much funnier :)
Frankly my dear, I'm sick of that one too. Things fall . . . . . down. :D

When they hit resistance they slow down, deflect to the side or stop.
 
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With that said, it is simply incredible that you would then indulge yourself in the above comment, when you admittedly wouldn't have a clue of what you are talking about.
Careful where you point that finger, dude.

You're the one who seems to think that fire does not damage concrete.
 
No, this is the only data on buckling that I know of. Bazant does not say how much the fracturing would affect the resistance curve and he does not suggest that it could suddenly go to zero.
He does on a later paper:

The high-strength steel has a much lower ductility, which must have caused fractures (with a drop of axial force to zero) very early during buckling, and must have been the cause of formation of large multistory fragments seen to fall from the lower part of the tower. Consequently, the energy dissipated (which is equal to the area under the load-displacement curve of the column) was probably about the same for high- and normal-strength columns.
(already quoted before, just with a bit more context now)

Still, omitting the part you omitted is dishonest, because you implied that Bazant supported the idea that the steel provided significant resistance when he actually says the opposite.


The exterior columns were typically W14x500. The flanges ares 17" wide and 3.5" thick. The Web is 2.19" thick and the column is 19" high.

These columns were held together with moment frames so they were mutually supporting each other.

To suggest that they would snap like sticks is baseless and erroneous.
Do you know what fracture is?

Remember the failing crane video. Once it fails, It just hinges without any significant resistance, even being unable to hold its own weight any longer. And it is steel. That's probably because the arm develops fracture at the hinge point. The only significant difference with a snapping stick is that the two parts do not become separated. But the loss of strength is similar.

Your claim that it is baseless and erroneous is what is baseless and erroneous. The base is the existing studies, and there is visible proof in the crane video.
 
Gravity didn't build it either. That's how searing your logic is here.

It looks right to me. It looks exactly like a controlled demolition, as it does to millions of others, including those in the building and demolition professions.


Probably closer to a billion or more.

http://en.wikipedia.org/wiki/World_population



World population estimates from 1800 to 2100, based on UN 2004 projections (red, orange, green) and US Census Bureau historical estimates (black).

The world population is the sum of all humans on Earth. As of today, it is estimated to number 7.008 billion by the United States Census Bureau (USCB).[1] The USCB estimates that the world population exceeded 7 billion on March 12, 2012
 
Frankly my dear, I'm sick of that one too. Things fall . . . . . down. :D

When they hit resistance they slow down, deflect to the side or stop.
Right.

WTC 7 was a gutted, empty shell, with nothing supporting the north wall when it snapped and dropped. Eight stories down, it hit the rubble pile and slowed down.

What is so damned mysterious?
 
Things fall . . . . . down. :D

When they hit resistance they slow down, deflect to the side or stop.

Exactly, apart from the bolded bit :rolleyes: (their acceleration might simply be reduced but with no reduction in velocity). Apart from that, where have I stated otherwise? If it's easier to smash the building below then that's what will happen. Like a brick dropped from 3' will smash through a greenhouse roof whereas a piece of gravel dropped from 3" might well bounce off.
 
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Not when the steel is already hotter than the gases. All the windows on the north side of floor 12 were broken right up to where the fire was [between columns 52 and 53]. Cool air was mixing with the hot gasses that were blown thru the building and out the south side. This was an hour and a half before the collapse.

[qimg]http://img691.imageshack.us/img691/4135/firesimcompare97.jpg[/qimg]

C7 demonstrates how a plentiful supply of oxygen will cool down a fire :cool:
 
C7 demonstrates how a plentiful supply of oxygen will cool down a fire :cool:
Apparently, he is ignorant of the fact that hot gases, adequately aerated, are a very efficient fuel.

This, of course, is irrelevant if there is a roaring fire on the down-wind side of the building.
 
Right.

WTC 7 was a gutted, empty shell, with nothing supporting the north wall when it snapped and dropped. Eight stories down, it hit the rubble pile and slowed down.

What is so damned mysterious?

Sure it was.

It is interesting that you and NIST have the interior completely collapsing on the east side first and then moving westward, but the east side exterior columns don't collapse until the entire interior is going, with the reason given that all of the the exterior columns were then unsupported and slender.

Why would the east side exterior have to wait for the west if they were already unsupported and slender seconds before?

Let's see if you can do something besides making incoherent comments like your one about concrete failing at high temperature where you provide no values or analysis to make it germane to the argument with the temperatures that were actually involved.
 
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You "forgot" the text that accompanies the illustration:
[...] which defines the curve plotted in Fig. 5. This curve is an optimistic upper bound since, in reality, the plastic hinges develop fracture (Bazant and Planas 1998), and probably do so already at rather small rotations.
That's dishonest.

There is no chance that ASTM A36 or ASTM A572 steel columns fractured at rather small rotations. This is nonsense propagated by Bazant.

This type of steel is used for its ductility for safety reasons. Go look up how much elongation both of those materials have and see for yourself.
 
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