Moderated Steel structures cannot globally collapse due to gravity alone

[Christopher7]

Since thermate/thermite/nano-anything can't "propel" anything and nobody heard any man-made explosives go off, what else is there besides gravity ?

You missed the point. Bazant did not include the energy necessary to eject the debris in his calculations.

Where did the "600 ft' claim come from? Cite, please.

http://www.internationalskeptics.com/forums/showthread.php?postid=4451000#post4451000

 

[Dave Rogers]

Shall we try some actual calculations here, children? After all, Christopher7 himself pointed out that equations are meaningless unless you plug in some actual numbers.

Let's take the mass of each tower as 250,000 tonnes, which is at the low end of the estimates. Let's take the height as 417 metres. Let's assume the mass distribution decreases with height, so we'll assume the centre of gravity is about 1/3 the way up. We therefore have a total potential energy of 250,000,000 x 9.81 x 417 / 3 = 340897500000, or about 340GJ, all of which was released during the collapse. Now, let's assume that, for steel section to fall up to 200 metres from the footprint, they had to be ejected at up to 22m/s and fall for up to 9 seconds in freefall. Therefore, the maximum energy to be imparted to a single piece is 4000 x 22^2 / 2 = 968000, or about 1 MJ. That's right; for the sharp-eyed, this means that each piece ejected soaks up a massive three thousandths of one per cent of the energy available. So we could have over three hundred four-ton slabs each ejected 200 metres, and 99% of the energy released in the tower is still available for collapse propagation.

"Substantial" is not exactly the word.

Dave

 

[HawksFan]

Sorry, but not one of those pictures shows anything being "hurled" any distance. Got some evidence of things being "hurled" and not of things that landed there after falling over from great heights?

 

[Christopher7]

Chris, do you still maintain that, in a gravitational collapse, the 30,000 ton upper section should have been ejected 208 feet so as to fall off the top of the lower section?

I said it toppled off because one side collapsed faster than the other.

Do you understand that Bazant did not calculate the energy necessary to eject all the debris and factor that in to his equations?
Furthermore, he did not subtract the weight of that debris in his equations.

"l = height of compacted layer B, μc = specific mass of compacted layer B per unit height, which is considered to be constant and equal to the maximum possible density of compacted debris; m(z) = cumulative mass of the tower above level z of the crushing front (m(z) = m0 + μcl); and Fc = resisting force = energy dissipation per unit height;"

 

[GStan]

I said it toppled off because one side collapsed faster than the other.

Do you understand that Bazant did not calculate the energy necessary to eject all the debris and factor that in to his equations?
Furthermore, he did not subtract the weight of that debris in his equations.

"l = height of compacted layer B, μc = specific mass of compacted layer B per unit height, which is considered to be constant and equal to the maximum possible density of compacted debris; m(z) = cumulative mass of the tower above level z of the crushing front (m(z) = m0 + μcl); and Fc = resisting force = energy dissipation per unit height;"

Have you asked Bazant why he did not do these things? Since you really aren't listening to anything anyone here is saying anyway, why don't you ask him why he felt this was not necessary, or explain to him why you think it was necessary?

There is nothing extraordinary about the distribution of the debris field that would require such a calculation in a document meant for an audience full of people who already know why there was nothing extraordinary about the distribution of the debris field (and the amount of energy required to produce it as compared to the amount of energy released during the collapse.)

What is extraordinary is that someone can seriously argue that a wide debris field and an inside its own footprint debris field are BOTH hard evidence of a CD and pretend to mean it.

 

[BigAl]

You missed the point. Bazant did not include the energy necessary to eject the debris in his calculations.

http://www.internationalskeptics.com/forums/showthread.php?postid=4451000#post4451000

To keep the math simple, at WTC, a beam falls from the top in ~10 seconds.
That means that the object needs a horizontal V of ~60 ft/sec/ to follow a parabolic path that reached the spot.

How much TNT, as calculated in joules does it take to accelerate a ton to 60 ft/sec? It's too early for me to do the math, but I don't think it's that much given that hundreds of tons of TNT (equiv) were converted from potential energy to kinetic energy at WTC.


BTW; the building at 600ft is (was) a greenhouse structure. The object wouldn't have to be thatlarge to crash through the roof. I'm more impressed by the large beam that is stuck in an adjacent building and I would take to be ~400 ft.

See page 25, here.
http://mceer.buffalo.edu/publications/wtc/02-SP02Screen.pdf

 

[Dave Rogers]

I said it toppled off because one side collapsed faster than the other.

That still would have required it to move 208 feet laterally in under 10 seconds, requiring about a 6.4m/s velocity and hence about 614MJ of kinetic energy. You have no problem handwaving 614MJ into existence, yet you're querying every single megajoule that you don't like the look of.

Do you understand that Bazant did not calculate the energy necessary to eject all the debris and factor that in to his equations?

Possibly because he knew it was negligible, as I showed a couple of posts ago. Thousandths of percentage points don't qualify as "substantial".

Furthermore, he did not subtract the weight of that debris in his equations.

Even if true, that's hardly relevant. As I understand it, Frank Greening's done calculations of mass shedding and found that it doesn't increase the collapse time significantly (i.e. the final predicted collapse time is still within the error margins of the time determined from videos and seismic data). I believe Gregory Urich has reached the same conclusion. I repeat my suggestion that you join http://the911forum.freeforums.org/ and ask them yourself. Until you've done that, I suggest you stop blathering about a subject that you haven't bothered to research adequately.

You seem to be making the error that if you can find an error in one specific calculation, that invalidates the entire principle. There is a larger body of work on the dynamics of the WTC collapses, and the broad consensus is that collapse propagates. Unless and until you can do a calculation that shows, correctly, that the towers should not have collapsed within any resonable scenario, you're just nitpicking.

Dave

 

[Christopher7]

Let's take the mass of each tower as 250,000 tonnes, which is at the low end of the estimates. Let's take the height as 417 metres. Let's assume the mass distribution decreases with height,

Bazant didn't do that. He used the cumulative mass in his equations. His calculations are therefore incorrect.

so we'll assume the centre of gravity is about 1/3 the way up. We therefore have a total potential energy of 250,000,000 x 9.81 x 417 / 3 = 340897500000, or about 340GJ, all of which was released during the collapse. Now, let's assume that, for [a] steel section to fall up to* 200 metres from the footprint, they had to be ejected at up to* 22m/s and fall for up to * 9 seconds in freefall.
Therefore, the maximum* energy to be imparted to a single piece is 4000 x 22^2 / 2 = 968000, or about 1 MJ. That's right; for the sharp-eyed, this means that each piece ejected soaks up a massive three thousandths of one per cent of the energy available. So we could have over three hundred four-ton slabs each* ejected 200 metres, and 99% of the energy released in the tower is still available for collapse propagation.

"Substantial" is not exactly the word.

Dave

Your off-the-cuff math for 300, 4 ton pieces traveling 600' after being ejected from the top of the building is silly.

Most of the debris fell outside the footprint.
Your off-the-cuff math does not give a reasonable estimate of how much energy it would take.

 

[DGM]

.
Most of the debris fell outside the footprint.
Your off-the-cuff math does not give a reasonable estimate of how much energy it would take.

Please show how you came to this assertion.

(why do I get the feeling he'll show me pictures with no data to back them up )

 

[Gravy]

You are OT as usual. Copy/paste anything I write in my articles and prove it wrong!

Wrong again. I'm responding directly to your claims on the previous page, as you know.

Let's watch you flee from reality again. Here's a video of a real event in the real world, not in your fantasy world. Exactly when did the detonations occur that brought down this tower?

http://video.google.com/videoplay?docid=2873871255585611926#1m10s

As a reminder, here's 34 kg of RDX detonating.

I'm waiting. Don't be afraid, Anders. Being wrong isn't the worst thing in the world, and learning can be enjoyable.

 

[Sunstealer]

Your off-the-cuff math for 300, 4 ton pieces traveling 600' after being ejected from the top of the building is silly

Could you please refute his of the cuff calculations by doing some substantial calculations of your own?

Until you do, you are making yourself look extremely foolish. If you are going to critique his numbers then you need to do that mathematically. Secondly he states his assumptions which are perfectly valid. If you have problems with these assumptions then do some calculations of your own.

He has done a significantly greater quantity of mathematics and of higher quality in his rough, quick off the cuff calculations than you have managed in all of your posts on JREF. Either put up (do the maths) or shut up.

Sits back to watch C7 run and hide, hand wave, or totally ignore this post or move the goal posts. Nothing new there then.

 

[beachnut]

Bazant didn't do that. He used the cumulative mass in his equations. His calculations are therefore incorrect.

Your off-the-cuff math for 300, 4 ton pieces traveling 600' after being ejected from the top of the building is silly.

Most of the debris fell outside the footprint.
Your off-the-cuff math does not give a reasonable estimate of how much energy it would take.

Take some junk and place it on your head; pretend you are 1300 feet tall. Drop the junk off your head. How far does it fall from your feet?

You have 3 story tall spandrels, and aluminum cladding impacted with tons of debris that can easily reach 300 to 600 feet. You lack of knowledge and inability to do math is holding you back from breaking through to reality. 7 years you could have an engineering degree by now.

 

[Wolrab]

Where did the number 300 beams traveling 600 feet come from?

 

[Christopher7]

tripple post. sorry bout that. it just kept me on hold.

 

[Christopher7]

double post

 

[Christopher7]

I said it toppled off because one side collapsed faster than the other.

That still would have required it to move 208 feet laterally in under 10 seconds, requiring about a 6.4m/s velocity and hence about 614MJ of kinetic energy.

The top was not being pushed to the side, it was falling to the side. That doesn't require any energy.

he did not subtract the weight of that debris in his equations.

Even if true, that's hardly relevant.

It is true and it is very relevant. Bazant used the cumulative mass in his calculations.

As I understand it, Frank Greening's done the calculations of mass shedding

No, he did not.

Pg 3 We will use this law for the non-elastic collision where the colliding masses essentially merge into a single mass that continues to descend.

Pg 4 We now apply this simple model to the WTC collapse. We assume that both WTC building collapses began with an upper block of n floors collapsing onto a series of lower floors as in the “domino effect”. We shall refer to this process as the first stage of collapse. For this stage, (see equation 1), we have an initial mass nmf falling onto the floor below and becoming mass (n+1)mf. This new, enlarged, block of floors descends with velocity v2= {n/(n+1)}v1 through a distance hf at which point it trikes the floor below and becomes mass (n+2)mf moving at velocity {n/(n+2)}v2, and so on. This implies a first stage collapse sequence for WTC 1: all floors from 110 to 96 (= 14 floors) collapse onto floor 95; all these floors collapse onto 94 > 93 > 92 and so on to 3 > 2 > 1; for WTC 2 all floors from 110 to 81 (= 29 floors) follow the same sequential pocess.

Greening used the cumulative mass in his calculations too.

 

[Christopher7]

Please show how you came to this assertion. (why do I get the feeling he'll show me pictures with no data to back them up)

There is no data and you know it.

Brent Blanchard made a stab at it:
"A review of all photographic images clearly show about 95% of falling debris being forced away from the footprint of the structure"
http://www.jod911.com/WTC COLLAPSE STUDY BBlanchard 8-8-06.pdf

 

[Gravy]

Sorry, but not one of those pictures shows anything being "hurled" any distance. Got some evidence of things being "hurled" and not of things that landed there after falling over from great heights?

Yeah, the old retreat into "Don't look at all the evidence! Just Look at these few still photos of a dynamic event!" A classic example of this is Tony Szamboti's "upward moving banana peel plumes," which he sees in still photographs and says is evidence of explosives. The videos tell an entirely different story.

Any video of the collapses shows how ridiculous is the claim that explosives threw thousands of tons of steel around the site. Um, where are the enormous detonations that would be necessary to do that – detonations thousands of times larger than in any building demolition? And why would anyone employ thousands of times more explosives than is necessary to destroy a building? Remember, the truthers who aren't no-planers think the planes were employed as a cover for what really brought the buildings down. The "controlled demolitions" are supposed to be hidden! What howling lunacy.

Why does the heavy falling steel always precede the lighter dust and debris, which would be impossible if explosives propelled both? Where is the lighter shrapnel being blasted all over lower Manhattan?

Where are the secondary effects of these gigantic blasts: the broken windows for miles, the deaths and injuries from barotrauma and shrapnel?

Christopher 7 and Heiwa cannot answer these basic questions while keeping their fantasies intact, without invoking even greater absurdities. So they simply avoid addressing the questions. It's a pathetic spectacle.

Let them go. They have no influence on anyone but a handful of kooks, and are only here for attention.

"To be ruled by ideas for which you have no evidence (and which therefore cannot be justified in conversation with other human beings) is generally a sign that something is seriously wrong with your mind." –Sam Harris

 

[bje]

Heiwa is the nice guy that participates on JREF with funny parables and analogies of pizza boxes, sponges, lemons and so on that are supposed to be crushed by gravity alone according NIST (PE > SE). So Heiwa apply the Bazant model to these easy to visulize objects ... and nothing is crushed by gravity. Why is that. He never gets any sensible answers.

Reason is that pizza boxes, sponges, lemons and so on are quite difficult to crush at all and that gravity alone cannot do it.

So Heiwa, are you telling us that we could scale pizza boxes up and build skyscrapers out of light-weight cardboard?

Or are you just showing us why you know nothing about gravity and structural engineering?

 

[Christopher7]

Yeah, the old retreat into "Don't look at all the evidence! Just Look at these few still photos of a dynamic event!" The videos tell an entirely different story.

You ignored the point which is:

There were numerous 4 ton framing sections ejected up to 600 feet along with a great deal of other debris.

Bazant and Greening did not calculate the energy necessary to eject all this material.

Furthermore, they both failed to subtract the ejected material in their calculations.

Their theories are just that, theories. they did not take all the facts into consideration and therefore their theories don't prove anything.