"Inside Job": Hidden energy in reports by Prof. Bazant, Dr. Greening and D. Thomas

Originally posted by ANOK
First off how did you calculate the Pe?

Secondly where do you account for the FoS?

Thirdly, you do not account for the loss of Ke to deformation, sound, heat etc.

We are discussing Bazants work, so all values come from his paper.

reply to post by -PLB-


...and what about the loss of Ke to deformation etc. Where does it address the FoS? Without knowing how much pressure the connections could withstand before failure, any calculations are meaningless.

Here is the problem, you don't know enough to know if Bazants calculations are valid obviously, because you can't explain where those figures even come from.

Those calculations ignore the fact that when the first two floors impacted Ke was lost to deformation, heat, sound etc. Ke was LOST, not gained.

So if the floors continued to fall then Ke is gained once again but it is NOT added to the Ke you lost. So the Ke, even IF the floors continued to collapse, would not be progressively gained, it would be lost at every impact. So no, Ke would not be increased as you want to believe.

The collapses did not show any sign of slowing due to floors impacting, it seem as if Ke did in fact increase, and was not lost. There is only one way that can happen, an outside energy was acting on the collapses that has not been addressed.

reply to post by ANOK

Here is the problem, you don't know enough to know if Bazants calculations are valid obviously, because you can't explain where those figures even come from.

From what I can gather all of their calculations are based on their interpretations of the impact videos and the one or two images available of the impact damage. Their models are built to reach a predetermined conclusion. They start at the end and work backwards, hiding their dissembling behind a blizzard of calculations.

reply to post by ANOK


If you disagree with the values used by Bazant, calculate your own values, get it published, peer reviewed, and I will use those instead.

reply to post by septic


It is explained in the paper how he got those values. Unfortunately, how the values for energy consumed were derived is not included. For that we have to rely on the expertise of Bazant. He says the following about it:

due to un- availability of precise data, an approximate design of column cross sections had to be carried out for this purpose

Since the topic we are discussing is the collapse mechanism, and not the precise values of the energies involved, I don't think it is relevant for the discussion. Or to put it differently, we are discussing if the collapse would progress given the values derived by Bazant.

Whether the values he uses are correct is another discussion. I am of course open to discuss that to, but I don't think it is useful to jump from subject to subject without concluded any of them. I must say though that I have never seen anyone ever made a good estimate. The ones by Bazant are grossly overestimated, which he openly agrees to.

Originally posted by septic
From what I can gather all of their calculations are based on their interpretations of the impact videos and the one or two images available of the impact damage. Their models are built to reach a predetermined conclusion. They start at the end and work backwards, hiding their dissembling behind a blizzard of calculations.

Yeah the whole OS, NIST report etc., were all built on predetermined conclusions.

Whether the "government" planted the explosives, or "Arab terrorists" did, the NIST report is a whitewash. Which means the "government" is involved either way, they're obvioulsy covering for somebody. Why would they lie to protect the terrorists?

But regardless of whether they're covering up for themselves, or someone else, they lied about what happened.

Peace, friends, I think you got it.

What's the difference between thinking of a container full of stuff on the rooftop, then lifting and dropping it from a crane so it crushes through all floor slabs into the basement ('nuff icejumping for today) and the whole building coming down? The volume, the area affected and the pressure. That's the difference between a katana and a hug. Now I also understand what OneWhiteEye is trying to say on the 9/11 forums, his steam models made me think. Nobody's talking about pressure and tension. May I call to the witness stand: Blaise Pascal (thank you, Mr. Newton).

Pressure, Tension, Compression, Strain and Stress.

What happens to the spring?

I see this discussion has progressed nicely (for the most part). -PLB-, I think you're doing a great job of interpreting and explaining Bazant in a very straightforward way. Akareyon, I can count on one hand the number of times I've run across a "heretic" who understands the papers as well as you; for that matter, it's very rare to run across a "shill" who has your depth of understanding. You've got skills. I think you're perhaps a stone's throw away from an aha experience on this.

This is the point where I usually play armchair psychologist. It never works. I say something like "you don't have to give up any conspiracy beliefs because of Bazant" and it's supposed to ease the transition to the dark side. Hahhaha. Well, all the same, it's true. Take a minute to think about it and if it doesn't come to you, I'll explain what I mean. It's better when you come to certain realizations yourself. It usually comes easier and sticks better.

Since this is going so swimmingly, I'm going to stay out of the way for the most part except for maybe some comments here and there.

Originally posted by Akareyon
Now I also understand what OneWhiteEye is trying to say on the 9/11 forums, his steam models made me think.

Steam? Heh, heh, like a steam engine? Like this steam engine?

Actually, I've mostly used PhysX for the physics engine sims because I've got a PhysX coprocessor on my video card. Less than 4K elements can be solved in hardware, very nice speedup and okay for simple systems.

Originally posted by ANOK
reply to post by -PLB-

 

...and what about the loss of Ke to deformation etc. Where does it address the FoS? Without knowing how much pressure the connections could withstand before failure, any calculations are meaningless.

Wait, wait, it's there. Didn't we touch on this briefly in another thread recently? The figures Bazant arrived at can be quibbled over but none of these are omitted.

Here is the problem, you don't know enough to know if Bazants calculations are valid obviously, because you can't explain where those figures even come from.

The load displacement function, really the primary input since it describes the structural response over the whole range of compaction, comes from this formula:



It's a quite generic textbook formula (as best as I remember, came from one of Bazant's textbooks, maybe not), which has pluses and minuses.

The obvious plus is that it's an analytical expression which can be implemented in a solver as opposed to being megabytes of table data - which isn't readily or completely available anyway. It would be a huge amount of effort and expense to fabricate both test columns to match specs and the test jig to crush them, then reduce all that data. My opinion is that isn't worth it. The properties of failure in axial compression have been studied for centuries, it's important to many fields not the least of which is construction. If the formula is derived from a huge body of empirical study, as it is, it will be reasonably representative of the various column configurations in the tower.

The drawback is that it can't be 100% accurate. Really that's all. It might be (e.g.) 10% low for one set of stories and 12% high for another set. Most of the discrepancy will come out in the wash if looking at the entire collapse.

Those calculations ignore the fact that when the first two floors impacted Ke was lost to deformation, heat, sound etc. Ke was LOST, not gained.

This is not true. Read the most recent posts. You're saying stuff is not accounted for right after posts with calculations showing the very thing you claim isn't there. How is this advancing the discussion?

So if the floors continued to fall then Ke is gained once again but it is NOT added to the Ke you lost. So the Ke, even IF the floors continued to collapse, would not be progressively gained, it would be lost at every impact. So no, Ke would not be increased as you want to believe.

Only one response seems to be necessary here. Read the last series of posts. It's ALL right there, how did you miss it?

And how did you miss the word "deformation" in the Bazant papers? Nine occurrences in BLGB, one in BL, six in BV and nine times in BZ. Pretty central to all the work. I'm sorry to say but you're making things up and stating them as fact.

Irish, welcome back : )

Speaking of tension: where have the 600,000 square feet of glass from the Window on the World gone?

Okay. I promise I will stop to believe in aliens, intelligent design, growing earth, morphogenetic fields and the moon hoax and never wear a tin foil hat again if we can figure this out.

I've been thinking about the energy that we need to "contain" the potential energy. Is it a fluid, the bottom of a lake, a drinking glass, a plastic bag, the knobs on lego bricks, pasta, paper loops, steel bolts, chains, ropes, joints, levers, glue, a balloon, a capacitor?

Sure: in Bazants model, kinetic energy keeps increasing. Just a second before, it was potential energy. That's exactly the problem! Where's u_0 then in Fig. 3?

For we now have found out that this energy (strain energy mayhaps?) containing our potential energy was just 0.5GJ * 109 floors = 54.5 GJ.

Among my first approaches was this one:

E_decelerating = 500,000,000 kg * (9.81-4.08)m/s² * 400m / 2 ≈ 573 Gigajoules.

If you've been there before, show me the way, please.

reply to post by Akareyon

Speaking of tension: where have the 600,000 square feet of glass from the Window on the World gone?

Glass is removed from buildings about to be demolished.

Originally posted by Akareyon
Speaking of tension: where have the 600,000 square feet of glass from the Window on the World gone?

First off, I don't have all the answers; very few of them, actually. Now, I'll take a guess. The windows were a secondary component of what looks like dust and clouds in videos taken from what was necessarily a pretty good distance (in order to live). If you watch the Mark Heath video, you'll hear the sound of what could be thousands of chips raining down and bouncing around. Could be glass.

Okay. I promise I will stop to believe in aliens, intelligent design, growing earth, morphogenetic fields and the moon hoax and never wear a tin foil hat again if we can figure this out.

Ah, but those things are true.

I've been thinking about the energy that we need to "contain" the potential energy. Is it a fluid, the bottom of a lake, a drinking glass, a plastic bag, the knobs on lego bricks, pasta, paper loops, steel bolts, chains, ropes, joints, levers, glue, a balloon, a capacitor?

If you mean how the self-destruct mechanism was held back from going off, it's by way of another potential, the strain potential. The peak in the load displacement curve is the "potential barrier" (to borrow a QM idea) which needs to be overcome to release energy on the backside. That's the structural integrity of the building, and it's really quite strong. It has limits, though.

Sure: in Bazants model, kinetic energy keeps increasing. Just a second before, it was potential energy. That's exactly the problem! Where's u_0 then in Fig. 3?

Uhh, lower left corner? Hahaaha, I don't think I understand the question.

For we now have found out that this energy (strain energy mayhaps?) ...

Yes, exactly.

...containing our potential energy was just 0.5GJ * 109 floors = 54.5 GJ.

Yes, pretty much. All those peaks have to be overcome; if not, it arrests. The premise is, PE lost per unit drop length is greater than KE consumed, so it gets easier and easier to climb those peaks as it goes down, even though the capacity is increasing.

Among my first approaches was this one:

E_decelerating = 500,000,000 kg * (9.81-4.08)m/s² * 400m / 2 ≈ 573 Gigajoules.

If you've been there before, show me the way, please.

You are so close to setting up a stepwise model for calculation. Just handle this one story at a time, it's easier and will let you test for arrest at a story granularity. Assume for the moment that all energy is dissipated in the crushing front, then one story at a time is a tight approximation to the dynamics. Seems like you were going that way at one point.

Do you have a programming language of choice?

Haha, that's the problem. Commodore 64 BASIC V2.0 and POV-Ray script, that's all (quite mighty, though!).

But I guess I'll understand fake code or some Java pidgin so I can translate.

May I recommend Ruby for this sort of thing if you're not already in committed relationship? You'll never outgrow it. Version 1.8.6, not 1.9.x, because RMagick is not yet supported in 1.9, and you may at some point want to draw some pretty graphs straight from code.

Let me dig something up.

Ruby looks sexy.

No second line needed, but I'm coming with you just to see where we're going

The 5000 character posting limit is a drag. I wanted to post this very short script with BBCoded syntax highlighting, makes it easier to read. And ****ing indents(!), which is practically mandatory to be able to read it.

class Collapse
attr_accessor :height, :stretch, :block, :stories
def initialize(height, stretch, block, stories)
@height = height;
@stretch = stretch;
@block = block;
@stories = stories;
@distance = dropDistance(height, stretch);
@compacted = @stretch * @height;
@block_height = @block * @height;
puts("nFloors,t,crush_y,v,B_thickness,roofline");
step(0.0, (@stories - @block)*@height, 0.0, @block);
end
def step(t, y, v, nFloors)
b_thickness = (nFloors - @block) * @compacted;
roofline = y + b_thickness + @block_height
y = 0.0 if y < 0.01;
puts([nFloors, t, y, v, b_thickness, roofline].join(","));
td = timeToDisplace_freefall(v, @distance);
preVelocity = v + velocityGain_freefall(td);
postVelocity = postCollisionVelocity(preVelocity, nFloors);
return if nFloors >= @stories;
step(t + td, y - @height, postVelocity, nFloors + 1);
end
def g
9.81
end
def dropDistance(height, stretch)
(1.0 - stretch)*height
end
def timeToDisplace_freefall(v0, y)
(-v0 + Math.sqrt(v0*v0 + 2.0*g*y))/g
end
def velocityGain_freefall(t)
g*t
end
def postCollisionVelocity(v, nFloors)
v*(nFloors.to_f/(nFloors.to_f + 1.0))
end
end

stretch = 0.2; #or zero
height = 3.7;
block = 12;
stories = 110;

Collapse.new(height, stretch, block, stories);

This is a 'slab model' and basically the shortest chunk of code I've written to do this. Recursion is not my thing but it made this ultra compact versus iteration through the floors. It's momentum-only, no energy sinks except inelastic collisions between slabs. Uniform story masses and height. One step at a time.

Originally posted by Akareyon
Ruby looks sexy.

Yes, but well-used, if you get my meaning.

Just for the gurus out there, my main squeezes are C++ and C# (ick, M$) but Ruby is best for these little one-night stands. C# is pretty expressive, but not nearly so as Ruby. Ruby is very slow, but makes for extremely compact code which is more important here - because, as you can see, there isn't much going on there.

Edit: oh, and I wrote this a long time ago so it's not very Ruby-esque in its styling. Couldn't make up my mind whether I like camel case or underscores; all runs the same.

There are a lot of ways to do this. This is just an example and it's meant to be very simple. It is a storywise (discretized) model with very little to tweak. Rigid upper block is used.

There is one class called Collapse. This shows the data members:
[font=Courier New]
[color=#349d58] 01 [color=#fca8ad]class Collapse
[color=#349d58] 02 attr_accessor [color=#a9fcf7]:height[color=#b0b0b0], [color=#a9fcf7]:stretch[color=#b0b0b0], [color=#a9fcf7]:block[color=#b0b0b0], [color=#a9fcf7]:stories
...
[color=#349d58]40 [color=#fca8ad]end[/font]


The members are the input parameters. As you can see, there are only four in this very simple representation.

height: height of one story
stretch: inverse of compaction ratio (e.g, debris compacts to 1/5 original height => stretch = 0.2)
block: size of upper block in number of stories
block: total number of stories in building

What I haven't seen so far in this thread is actual coupling between the floors due to columns running the height of the building and being rather violently deformed. When you forcible move columns around, it's simply impossible that the integrity of various connections of structural elements on a few layers below would somehow persist. On a sad note, I witnessed the collapse myself. To me it looked like peeling a banana. If the columns are being peeled away, I can't imagine you can consider the strength of the next layer at the nominal level.