Chandler: "On this kind of a graph, a straight line indicates constant acceleration."

What's wrong with that statement, wildbill? If you can figure our what's wrong with that statement, you'll also know one reason why his entire argument fails, badly, but there is actually a second reason, just as good.

What's truly pathetic about the stupidity of this argument is that Chandler is one of the few AE911truth guys who even attempts to make technical arguments.

That sentence wouldn't be bad if he was simply trying to explain a velocity graph. What he actually tries to do with it is bewildering.

Let's see, am I getting this right? (1) The "upper block" is falling at 0.64g, which means that the downward force it exerts on the rest of the building is 0.36g, so it is exerting less force on the rest of the building than if it were standing still. (2) The acceleration is (purportedly) constant, which means that the rest of the building isn't exerting any resistance.

Is that really, more or less, what he said?

nt

Look, it's OK with me if you aren't interested in discussing the catastrophic events of 9/11, but then what is your point?

It's actually hard to untangle what he says, but the apparent argument is that columns which had been designed to hold 300% of the weight above them were only providing a resistance of 64% of the weight, which implies (ta da) controlled demolition.

He can't even seem to decide whether or not the lower part of the building is providing resistance. Apparently, the "constant acceleration" is supposed to prove that it isn't, even though it is at less than g.

You tell us what's wrong with it william.
His argument doesn't fail, yours does however!
How would that graph look if it did represent constant acceleration in your opionion?

Last edited Wed Dec 28, 2011, 12:44 PM - Edit history (1)

A constant acceleration would produce a straight line on that velocity graph, yes, but imposing a straight line on measurements every 0.2 seconds, with no indication of the error in the measurements, cannot tell you with any accuracy that the acceleration was really constant. You might say it's approximately constant, at some scale, but the difference between that and truly constant gets you into trouble if you try to apply that over-simplification the way Chandler does to say that the resistance of the lower structure was only 36% of the weight of the upper structure. Tracking the roofline falling is to track the aggregate result of thousands of individual failure events, and the acceleration that Chandler is measuring is just the AVERAGE result of all of them. In failure events where a column buckled, there is no reason to think that, locally, the acceleration was anything resembling constant: The column only provided it's maximum resistance for a few inches of downward deflection, followed by rapidly decreasing resistance (and increasing acceleration) as the column went into plastic deformation and buckling, possibly followed by zero resistance (and local free-fall) if the column broke. If all the column failures were due to buckling, then all you could say from Chandler's measurements would be that the columns allowed an AVERAGE acceleration of 64% g through that entire fall to the next floor, not that the column only resisted 36% of the weight. In fact, we know that most columns did not fail from buckling, and that's the second problem with Chandler's argument: Most columns were simply pushed aside after the floor structure was ripped away from them. Again, the maximum resistance was only for a few inches of floor and column deflection, at most, followed by zero resistance (and local free-fall) once the floor broke free, so that's certainly not a constant acceleration, either. Chandler's 64% g, then, is the net AVERAGE of everything from the acceleration through maximum column resistance to free-fall, but by inaccurately claiming constant acceleration, Chandler uses it to claim that the maximum column resistance was only 34% of the weight. It's an idiotic argument.

Place a 10lb weight on top of a 1ft stick that is capable of supporting 20lbs without buckling and breaking - so far so good.

Now lift that 10lb weight 1ft above the top of the stick, and place it on top of another similar stick connected to the first stick. The weight will be 2ft off the ground now. Now break the top stick, which will drop the 10lb weight on top of the lower stick. What do you think will happen?

The weight will accelerate through the lower stick and break it. The weight will hit the ground a little slower than if the lower stick wasn't there at all - let's say at 90% of free fall speed. The 10lb weight would then average .9g acceleration

By David Chandler's logic, the lower stick only provided .1W (1lb) resistance, which means that the weight only provided .1W (1lb) of worth of force. Since 1lb is 90% less than 10lbs, the lower stick must have been broken by some other means - perhaps an explosion.

He then goes into some nonsense about its constant acceleration - and whatnot.

My analogy isn't perfect. As the towers collapsed, the falling sections gathered more mass from the lower sections of the building as they fell. The mass from the lower sections of the buildings started at an initial zero velocity, which slowed down the acceleration of the falling sections.

thanks for the laugh!
ironic you post such nonsense and the go on to call a physics teacher's efforts nonsense. thanks again..

Good to know.

the rebuttal is in the videos!

If that's your only response, I don't believe you really understand what the video says OR the arguments you've been given.

Prove me wrong by stating both in your own words, and then try to substantiate your claim that "the rebuttal is in the videos!"

Oh, I forgot: You're not under any obligation to prove any of the, uh, "truth" you post.

I cannot help that you can't/won't see it!
Believe what you will but don't piss down my leg and tell me it's raining.

Why should we? If you made an argument, we could assess it -- but if the best you can do is to assert that someone else came up with an argument for you, well, would you buy that if I tried it? I don't think so.

cpwm17 took the time to write a serious response to your comment. If you've got nothing, you've got nothing.

nt

Posting unsupported assertions may undermine your credibility, but you have never demanded to be treated as credible. I just don't see the point in it.

You're not quite sure about that, are you? If you can't describe this "rebuttal" you see in the videos, maybe it's a figment of your imagination, huh?

But you don't understand what he's talking about. That's why you can't post a rebuttal to my comment.

David Chandler's physics is way off. He doesn't indicate that he understands the collapse, or even basic physics.

Try reply #5 for starters.

Less nonsensical on its face. If the poster wants to redo his scree to make it
more readable, I'll give it another try.

* clerical edit

You can't read it because you can't decide where the paragraph breaks should go? And that makes Seger's post "nonsensical on it's (sic) face"?

Last edited Thu Dec 29, 2011, 02:04 AM - Edit history (1)

1) Chandlers measurements do not (and cannot) support the assertion that the acceleration was constant.

2) There is absolutely no reason to expect that the acceleration was constant, given that no conceivable failure modes would produce that result, even if it was a controlled demolition. (It's actually kinda funny that Chandler just blows right past that minor problem with his theory.)

3) If the acceleration was not constant, then Chandler's inferences about the maximum resistance being 36% of the weight are ridiculous, and that make him look rather like an idiot.

4) I can't think of anything less relevant to the issues than your inability to even comprehend what I'm saying. If you want to "give it another try" then good luck, but if you still don't even understand it, perhaps you should consider not responding.

... and it's always interesting to get some insight into who is falling for his nonsense.

And, it is those who support, or pretend to support, the Bush administration's preposterous hoax who are "falling for" nonsense. That's in quotes because I think in some cases, proponents
of the Bush administration's hoax theories know full well the extent of the 9-11 fraud. However, I'm satisfied that you're not among that group, William.

... and virtually NONE of what we know about 9/11 came from the "truth movement." As someone who supports Chandler's nonsense even though you don't understand it, you're hardly in a position to be taken seriously when you accuse thousands of people of being accomplices to a mass murder, without a shred of credible evidence. Since you call Chandler's nonsense "evidence" I'm not at all sure you know what the word means.

supported by?
more opinion!

Take this:

was what the data points plotted.
what may I ask would have been the correct way?
No it is seger's opinion! Where is seger's corrected graph?

Chandler says, "as long as the top section of the building is in uniform downward acceleration, it cannot possibly be providing sufficient force to destroy the building."

But has Chandler proven that the top section of the building is in uniform downward acceleration? Hell, no. His points don't even form a straight line, although they're pretty close. (Of course Chandler imposed that line; if you connected different dots, you'd get a different line. Again, fact, not opinion.)

If Seger estimated Chandler's measurement error, you would say that was just opinion -- and you might even be right. But if you construe that those points are pretty much in a straight line, then you can start to get a feel for the problem by sketching (or imagining) lines connecting each pair of adjacent dots. For instance, in the screen shot I just took, one circle is about 14 pixels below the one to its left, and about 32 pixels above the one to its right. So, one line will be about twice as steep as the other.

For Chandler, apparently, an apparent doubling in acceleration is within the range of measurement error -- and it probably is. I'm certainly not convinced that the actual acceleration of his reference point changed in that fraction of a second; maybe it did, maybe it didn't. But if an apparent doubling in acceleration is within measurement error, then how could anyone say that the top section (or even his reference point) is in uniform downward acceleration?

One need only view the videos of the tower's descent to understand the absence of the necessary deceleration. Mapping it out on a graph is basically just spelling it out in crayon for those who can't see that an under-15-second plummet to the ground with massive expulsion of matter all the way down is not possible gravitationally for a steel-framed, highrise superstructure.

The other point being entirely missed here is that in order for the upper portion of building to exert the kind of force that can destroy as well as completely pulverize the much taller, heavier and intact lower structure it would need to decelerate (to use the lay term). Visibly. You can't have that kind of force exerted without visible decelerations. This would be multiple punctuations in the building's descent, most likely resulting in collapse arrest before the ground is reached.

This isn't difficult, folks.

You can't actually rebut previous studies of the collapses by saying, nuh-uh. An under-15-second collapse "is not possible gravitationally"? Why not?

The upper portion of the building doesn't have to "destroy as well as completely pulverize the much taller, heavier and intact lower structure." The upper portion isn't the only thing that falls.

You think that the upper portion is the only thing that falls? And you think I'm the one who doesn't understand the collapses and the official explanations?



Care to try again?

As you scale up the size of any object its strength to size (and mass) ratio goes down. This means that there is a lot of stress on large, tall buildings. So during a collapse of a large, tall building, depending on its construction, there is a lot of potential for a rather violent collapse. The towers weighed around 500,000 tons. There is a lot of potential energy being converted to kinetic energy during the collapse. That's the energy of a very large bomb.

The only way for there to be any deceleration during the collapse would be for the resisting force of the intact section of the lower block to be greater than the force of the falling upper block striking the lower block. That certainly didn't happen during the collapse. The lower block only slowed down the acceleration of the upper block's mass. The force after the upper block's mass fell a dozen feet between the floors is far greater than the resisting force of the intact section of the lower block. So it must accelerate all the way down, especially after the debris between the blocks increases during the collapse which provides more mass to accelerate the collapse.

"...The force after the upper block's mass fell a dozen feet between the floors is far greater than the resisting force of the intact section of the lower block."

First of all, the upper portion was never in free fall. (In fact, haven't 9/11 "debunkers" spent ten years arguing this very point??) So that is a deliberate miscalculation right off the bat. Secondly, and this apparently needs to be repeated across the internet: For the upper portion to EXERT THAT FORCE would REQUIRE IT TO DECELERATE. IF IT'S NOT DECELERATING, IT'S NOT EXERTING A FORCE. Because there's nothing to exert it against.

"So it must accelerate all the way down, especially after the debris between the blocks increases during the collapse which provides more mass to accelerate the collapse."

You're just repeating Bazant's cartoon model which has largely been discarded by both sides of the debate now. No, it would not accelerate all the way down. There's no model that has been put forward anywhere that can explain a debris-driven, top-down destruction (and pulverization) of an intact steel-framed skyscraper. If you know otherwise, please refer us to it.

Really? "Both sides"? Sounds like hyperbole to me.

Anything less than an acceleration equivalent to the local gravitational constant is an indication of an opposing force. After all, m*a = the net force on a body. Struggling with the concept? Try drawing a free body diagram of the upper portion.

1) We are talking about the smooth motion of the upper block in its initial collapse stages. No visible decelerations as it meets the stronger, intact lower block. Indeed, it destroys itself. Where does the core structure go?

2) We are talking about a force that needs to destroy all the connections of 80 - 90 intact steel-framed stories, while pulverizing all contents at the same time, at the average rate of 0.17 seconds per floor. The upper portion of building does not have this energy through gravity. How could it? It did not free fall during collapse initiation. It did not free fall at any time. Right there, it does not have the energy to complete collapse, and it only loses energy through each successive floor gravitationally, as it must. On top of this, you are requiring it to pulverize all the building contents at the same time. This is never going to happen gravitationally. Further, the top portion has destroyed itself in the first three seconds of collapse. Where is the model for a debris-driven, top-down, total destruction of a steel-framed super highrise?

Please include in your reply an answer to the last question.

You haven't explained your claim that no visible decelerations means the upper portion is not exerting a force on the lower portion. This claim is not compatible with basic physics principles.

Your #2 is nonsensical. A rational reply is not available.

"You haven't explained your claim that no visible decelerations means the upper portion is not exerting a force on the lower portion."

As I stated in the very post you are replying to:
[quote=jesters]... 2) We are talking about a force that needs to destroy all the connections of 80 - 90 intact steel-framed stories, while pulverizing all contents at the same time, at the average rate of 0.17 seconds per floor. [/quote]

You are attempting to suggest that the 30% resistance provided by the bulk of the intact structure, which, by standard engineering, was capable of providing 300%, is due to gravity acting on the upper block. This point of view apparently does not understand that the force exerted in this instance, as measured by the resistance seen, is not enough to destroy the building, even if it did initially drop in free fall (which it didn't). Not to mention that the upper block destroys itself in the first few seconds of collapse.

"Your #2 is nonsensical."

I've now explained it twice. What part don't you understand?

And can you point us to a credible model of a debris-driven, top-down total destruction of a steel-framed super highrise?

It is not the case that the upper portion needs to "destroy all the connections... while pulverizing all contents." But even if it were, the question remains whether you stand by your assertion that "IF IT'S NOT DECELERATING, IT'S NOT EXERTING A FORCE." You can't explain that claim by repeating the other claim.

Please provide an explanation. A properly labelled free body diagram would be acceptable in lieu of a narrative.

to put numbers onto your point.

Can you do that?

Do you really need one to understand this concept?

Do you know of other kinds of collisions between similar bodies where decelerations do not occur?

Well, if you can, please do.

I personally don't see the issue. Bazant Zhou (which, despite your assertion above, no one outside of 9/11 Truth has discredited) shows that the upper section would have had ~31 times the energy necessary to overwhelm all structural support below. Even you admit that the upper section is only accelerating at 70% of freefall. That other 30% is going somewhere - that energy is doing something.

Basically put, 9 times the energy to overwhelm the lower structure completely is not present in the descent of the lower section. My answer would be it's going to tear apart the lower structure and pulverize building contents. Your milage may vary.

Also, there is no reason to think that each individual collision between the upper and lower section would propagate to the top of the upper section. Since they are not rigid blocks but complex structures hitting each other off-center, any expected "jolt" would actually only be seen at the point of contact, ripping one or the other structural element loose. And after the center debris field was developed, no such jolt should even further not be expected.

Because they assume free fall during collapse initiation, ignore Newton's third law in the subsequent collisions, and (later) invent a magic carpet of rubble that the fictional upper block rides all the way down to the ground before getting eaten by it at the end.

Are you seriously using this model?

Bazant Zhou is a limiting case, using the best case scenario for WTC tower structure survival, and still the building falls. This is of immense importance to understanding why total collapse was inevitable after collapse initiation. It lays a framework for speaking about and understanding all similar types of collapse.

Where do you think the kinetic energy not being used to accelerate the upper sections is going and doing, jesters?

I take it you refuse to offer the properly labeled free body diagram that has been asked of you.

"Where do you think the kinetic energy not being used to accelerate the upper sections is going and doing, jesters? "

This is a bizarrely phrased question. What extra energy are you referring to? The only energy available to pull the top section of building through the lower is through gravity. Bazant and Zhou assume a free fall initiating impact which did not occur, and then ignore the absorption of kinetic energy by the lower, much more intact, much larger structure. That's where they get their "inevitability", their "overwhelming" force. This is hardly a best case scenario. It's a fabrication. The best case scenario for collapse arrest is reality: the buildings remained standing after the plane impacts. Were it not for incendiaries, they would have remained standing or at most suffered partial collapses in the upper portions.

Bazant's model has been shown to be wrong by numerous independent analyses, on both sides of the debate.

Bazant's analysis IS an energy argument: It calculates how much energy the falling mass had and how much could be absorbed by the lower structure. I really don't understand why "truthers" think it's okay to slander one of the country's leading theoretical structural engineers without having the first fucking clue what he's even doing in that analysis.

And, btw, Bazant assumed one story of fall because that's the minimum possible. In fact, the initiating event was the floor pulling the perimeter wall in until it buckled, not buckling between floors, so the initial fall was really two stories rather than one. Furthermore, Bazant's calculations can be worked backwards to show that a fall of only about one foot would have put more impact energy on the lower structure than it could absorb. As Bazant says in a later paper, that's all a structural engineer needs to know.

> Bazant's model has been shown to be wrong by numerous independent analyses, on both sides of the debate.

Utter bullshit. Bazant's model has only "been shown to be wrong" by the kind of imaginary physics and hand-waving assertions that you're tossing around, and generally by people who know as little about the analysis as you. Out in the real world, it appears that Bazant's analysis is well accepted among those who actually understand the subject.

" It calculates how much energy the falling mass had and how much could be absorbed by the lower structure."

No, it does not.

And I love how you brush over his assumption of free fall in the initiating collapse.

"Bazant's calculations can be worked backwards to show that a fall of only about one foot would have put more impact energy on the lower structure than it could absorb."

And that would also be fantasy. It's astonishing that anyone would even try to make this claim.

> " It calculates how much energy the falling mass had and how much could be absorbed by the lower structure."

> No, it does not.

Utter bullshit; it does exactly that, as is perfectly clear to anyone who actually reads it and tries to understand at least the narrative if not the math. Do you really think you can bullshit your way around what's actually in that paper?

> "Bazant's calculations can be worked backwards to show that a fall of only about one foot would have put more impact energy on the lower structure than it could absorb."

> And that would also be fantasy. It's astonishing that anyone would even try to make this claim.

Well, it's not the least bit "astonishing" to claim that Bazant's calculations can be worked backwards to find the minimum fall that would produce an overload, nor is it a "fantasy" that the answer is about one foot, since those are just simple statements about the math. I assume what you mean is that your imaginary, factless, mathless physics says otherwise. The part you're leaving out, however, is any reason why a rational person should care about your imaginary, factless, mathless physics.

Really, reading the section titles would seem to suffice.

It would be better, to be sure, if would-be rebutters read "we are not attempting to model the details of the real failure mechanism," and correctly inferred that they can't rebut the paper by complaining that it doesn't model the details of the real failure mechanism.

... that's an analysis of how much gravitational energy had been converted to strain energy (and thus removed from the falling mass) when the columns reached their maximum elastic deformation. It shows that there was about 31 times more energy available than was necessary to push the columns through elastic deformation and into inelastic deformation, a.k.a permanent damage. If the structure had been able to absorb that excess energy by inelastic deformation, however, then the collapse would have halted at that point, so Bazant calculates that energy in the section you referenced. That analysis shows the maximum energy that could have been absorbed, best case, was only about 1/8th of the energy of the falling mass.

Anyone who wants to challenge Bazant's conclusion must do exactly one thing: Show that the structure should have been able to absorb the gravitational energy of the falling mass. The only person I know of who actually attempted to do that was Gordon Ross, and he seems to have disappeared from the "truther" scene after his "momentum transfer" analysis was shown to be fatally flawed.

"It shows that there was about 31 times more energy available than was necessary to push the columns through elastic deformation and into inelastic deformation,"

No, it does not, and no there wasn't.

"Anyone who wants to challenge Bazant's conclusion must do exactly one thing: Show that the structure should have been able to absorb the gravitational energy of the falling mass."

This has already been done. First by engineers who design steel-framed highrises, second by those who point out the flaws in Bazant's analysis. Gordon Ross is one of them. Where has his analysis been shown to be flawed and by whom?

> "It shows that there was about 31 times more energy available than was necessary to push the columns through elastic deformation and into inelastic deformation,"

> No, it does not, and no there wasn't.

That's exactly what the calculation shows, and your pretense of contradicting a leading theoretical structural engineer with nothing but naked assertion and imaginary physics would be laughable if it weren't so pathetic. Your arguments by assertion are getting tiresome. If that's all you've got, maybe you should stop and consider WHY you can't actually support any of the nonsense you're dumping all over the board.

> "Anyone who wants to challenge Bazant's conclusion must do exactly one thing: Show that the structure should have been able to absorb the gravitational energy of the falling mass."

> This has already been done. First by engineers who design steel-framed highrises, second by those who point out the flaws in Bazant's analysis. Gordon Ross is one of them. Where has his analysis been shown to be flawed and by whom?

Utter bullshit again. Nothing of the sort has been done by any qualified person, and "truthers" pretending to do so with imaginary physics and naked assertion don't even begin to count. In fact, if you know of any serious attempt besides Ross' then you really need to reference them, for a change. As for Ross, there were several minor problems with Ross' analysis that were noticed almost immediately, such as the fact that the columns were not continuous pieces of steel, and the joints every three stories would have caused some reflection of the elastic strain waves, so his strain propagation model was flawed. But the analysis lost any credibility when it was discovered that his "energy balance" had counted some energy twice: He had one line item for the energy lost in the inelastic collision and another line item for the energy required to fracture concrete. But those are the same thing: The energy lost in the inelastic collision IS the energy that breaks and deforms stuff. That's WHY it's lost, and that's the only energy available to do that work. With just that one error corrected, Ross' "energy deficiency" disappears. Some people hoped that Ross could re-do the analysis and find another "deficiency" but that entire enterprise seems to have come to an end when Bazant himself pointed out something that should have caused Ross the mechanical engineer to smack himself in the forehead at his own stupidity: A column cannot transmit more force than it takes to fail the column. It's like trying to push a car with a soda straw: No matter how much force you apply, and no matter if you do it slowly or quickly, the maximum force transmitted to the car is the force present just before the straw collapses. That meant that Ross' huge transfer of momentum through those failing columns was almost entirely imaginary, and Ross went MIA immediately thereafter.

Please don't bother responding if all you've got to say for yourself is "no it didn't." That's a pointless waste of time and bandwidth.

"With just that one error corrected, Ross' 'energy deficiency' disappears. "

I don't think so. But a source for this claim would be great. Thanks.

"Some people hoped that Ross could re-do the analysis and find another "deficiency" but that entire enterprise seems to have come to an end when Bazant himself pointed out something that should have caused Ross the mechanical engineer to smack himself in the forehead at his own stupidity: A column cannot transmit more force than it takes to fail the column. "

Who are the "some people" and in what paper did Bazant "point this out" re: Ross's analysis?

And then perhaps you can answer for us:

How the upper section has 31 times the energy that the lower section can absorb, while not assuming a free-fall initiating impact, using the correct mass value for the upper block, and calculating the energy loss in both colliding masses.

Since I can easily predict your knee-jerk reaction to posting links to that site, I'm not much inclined to waste time digging them up -- go find it, if you're really interested. But anyway, Ross' paper itself is the only source necessary to prove that it includes both energy losses from pulverizing concrete and energy lost due to the inelastic collision, as if they were two different things. Remove that double-counting, and Ross' claimed energy deficiency disappears.

And Bazant's observation about the maximum force a column can transmit to the structure below was not a response to Ross' paper; it was part of his response to a Discussion (a letter to the editor) concerning his last paper published in the ASCE Journal of Engineering Mechanics. Since Ross apparently never made any attempt to get his paper published in a peer-reviewed journal, Bazant has never had any reason to pay any attention to it, but his observation nonetheless pulls the rug out from under Ross' momentum transfer analysis by exposing a fatal assumption.

It's pretty strange that we're not only debating Bazant and Zhou, but debating whether they offer an energy argument.

SECOND time you've repeated this assertion. I don't care about any "shown to be wrong" from your side of the debate - show me the "numerous independent analyses" on my side.

I clearly stated what extra energy I was referring to. If the upper section is falling at 70% the acceleration rate of gravity, then the energy that would be creating the other 30% is going somewhere. Yes, it would be only available from gravity, but gravity doesn't accelerate at one rate sometimes and another rate at others. You know full well that gravity is a constant. Since the upper section is falling at an acceleration 30% slower than the acceleration of gravity, that 30% is going somewhere and doing something.

I'm asking you where and what you think that energy is doing.

to a free fall acceleration is not only physically and mathematically impossible when you consider energy absorption by the columns, column deformation, pulverization of the concrete and other building contents, but you're forgetting that the upper block also could only then offer 30% resistance to the impact.

Why is it that so-called skeptics cannot see that an impact is shared equally by both colliding bodies? Why do you ignore this physical fact? How can you claim to speak for science or engineering with such nonsense?

I prefer actual arguments, not hand-waving. Feel free to submit drawings and calculations, as these are typical methods for communicating technical arguments.

Or you could just admit your so-called impossibility is not necessarily so.

I've asked twice now for evidence of your assertion that independent analyses from both sides of the discussion have discredited Bazant Zhou. You've provided none. This is my third request, and if you ignore it again, I'll take from that you have no actual independent analyses from my side of the discussion and you're just asserting a falsehood.

You've also been asked for a properly labeled free body diagram, which would even help your attempt to explain to all of us "so-called skeptics" just what you mean in your description of the physics of this fall. And yet you will not do that either. I don't understand why you resist putting numbers and labels to a free body diagram.

Please provide your evidence for your "both sides discredit Bazant" assertion and a properly labeled free body diagram, if only to facilitate the discussion.

I think I've explained my objection to your theory about this pretty well. The upper section is falling, but is only accelerating at 70% of freefall. Since gravity is the only factor in this collapse and it's a constant, a large chunk of energy is being siphoned off to do something. You now say that this diverted energy is not enough to account for "energy absorption by the columns, column deformation, pulverization of the concrete and other building contents". Your calculations on that, please? And you are taking into account the fact that the upper sections in both buildings have twisted and are not hitting the structure below dead on? Pushing columns away is a lot less energy consuming than forcing them to buckle.

I have already explained it several times, Boloboffin, in lay terms. The calculations have been done by many others. You are now also pretending the crush-down model is actually a floor failure model, which Bazant did not talk about. So you are introducing some new hybrid theory of your own which has not been tested or proven; it's simply hypothetical. Even if they were correct, you cannot use Bazant's false energy calculations for column-on-column impact and crush-down for now a floor failure model.

The fbd you seek is provided in the OP. And here's perhaps a better explanation for you:

Last edited Wed Jan 4, 2012, 11:53 AM - Edit history (1)

At this point, all I can say is either a) your assertion of Bazant debunked by both sides is false because you actually have no links to provide or b) the instant you provide these links, you know full well the ridicule the links will justly inspire. So you just keep on saying Bazant's been debunked all you like, but until you give up some links to these debunkings, we will all know you're just whistling past the graveyard.

Bazant Zhou is a energy calculation. If the lower structure can't absorb the energy, something's breaking. When the upper section has 31 times the energy than the lower section can absorb, something's definitely breaking.

"you cannot use Bazant's... energy calculations for column-on-column impact and crush-down for now a floor failure model"

The hell I can't. Column-on-column is in the building's favor. If the Bazant Zhou limiting case of column-on-column impact can't absorb the resulting energy, do you think the motherlovin' floor connections could have? And you're calling my posts ridiculous? Give me a break.

"If the lower structure can't absorb the energy, something's breaking."

The lower structure can absorb the energy. That's what I've been saying for the last 18 posts.

Bazant's calculations are based on an initiating free fall impact which did not occur, apparently a doubling of the mass of the upper block, and completely ignoring the energy absorption by both colliding masses.

I've listed these points now three or four times. You have yet to address them, instead merely repeating false points from a single model you're relying on that doesn't work. How about addressing these points?

"When the upper section has 31 times the energy that the lower section can absorb, something's definitely breaking. "

Explain in lay terms how the upper section has 31 times the energy that the lower section can absorb, while not assuming a free fall initiating impact and calculating the energy loss in both masses. eta: And what mass value you are using for it.

Where did you raise a finger to demonstrate that the lower structure can absorb the energy?

and stop trying to reverse the burden of proof.

It isn't a matter of reversing anything. Unsupported assertions are unsupported assertions; you might as well be making things up as you go. No one should have to bear the burden of proving that they actually are wrong.

how so-called debunkers and skeptics never answer your questions?

It almost makes you wonder if it's because they can't actually defend their bizarre theories.

Then, when asked to back up that evidence they whine that the other side doesn't answer questions.

Well, so much for this discussion, as far as it went. Instead of providing the things and links you've been asked for, you've taken the asinine tactics of pretending I'm the one not answering questions and stating more and more ludicrous comments like the one I quoted above.

When you decide to get serious, I'd be happy to discuss these issues with you.

P.S. Anyone interested in the ~31 figure can find the calculation in Bazant Zhou.

http://www.civil.northwestern.edu/people/bazant/PDFs/Papers/405.pdf

It is formula number (1).

You're apparently replying to my post #92, but completely ignoring my request for you to:

Explain in lay terms how the upper section has 31 times the energy that the lower section can absorb, while not assuming a free fall initiating impact and calculating the energy loss in both masses. eta: And what mass value you are using for it.

Which would actually answer most of your questions.

I'll take this to mean you can't explain how the upper section has 31 times the energy that the lower section can absorb, while using an accurate estimate of the upper block's mass, not assuming a free-fall initiating impact and calculating the energy loss for both building sections in the subsequent collisions.

Kind of as I suspected.

I don't see the problem.

The top section didn't have to crush the entire bottom section. It only had to crush the one floor below it. It gained that mass and proceeded to crush the very next floor. Rinse and repeat 80 times.

The bottom floor had the weight of 109 floors fall on it.