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Building Collapses in Rio

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posted on Feb, 4 2012 @ 10:23 AM
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Originally posted by DrEugeneFixer

Originally posted by samkent
reply to post by psikeyhackr
 





The horizontal beams kept the columns from bending.

When will you realize that there were no horizontal beams? They did not exist! The design did not use them!
And that was the problem with the design. That's why no new sky scrapers will use that method of construction ever again.


Well, I hate to do this, but I'm going to have to jump in and defend psikeyhacker's quote that you are disputing.

There were horizontal beams in the WTC 1&2, but they were located only in the core area surrounding the elevators and toilet rooms. It's pretty much accurate to say that the horizontal beams (and also the composite slab and truss system) prevented the columns from bending,but we would usually say "buckling" rather than bending.


If by "composite slab and truss system" you are talking about the floor assembly outside of the core I disagree. That had nothing to do with the structural strength of the core. The idea that the core needed anything outside of itself for support is nonsense. The core provided the rigidity of the building. The perimeter columns provided the vertical support to the outer edge of the floor assemblies. The wind impacted the perimeter but the force was transferred to the core via the floor assemblies.

The difference between bending and buckling is so important. The "jargon" that experts insist on using is so much crap. The objective is to get as many people as possible to UNDERSTAND as much a possible. But then that would make it more difficult for experts to talk bullsh#.

psik




posted on Feb, 4 2012 @ 10:25 AM
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reply to post by IrishWristwatch
 





3) That a conceptual model that requires (or implies) a decrease in entropy in a system is always incomplete even if the system is not closed in reality.


Do not agree for the general case. If the system is open with external inputs defined, there can be a decrease of entropy within the system boundary. That's what external inputs are about! If you meant that an open system which has no external input defined which can legitimately account for entropy decrease is an incomplete description, I agree.


Wait, what?

I missed this one.

There is no such thing as a logically valid open conceptual model Irish. Either it conforms to the laws of logic and it is closed (which is another way of saying it conforms to the laws of logic) or it does not.

You really haven't taken the "paradox of analysis" thing to heart have you?

This is why I say that you expect to defy logic with math. Either everything needed to explain the behavior of your model is explained or it is not. There is no third option. Of course you can make simplifications, but you can't include miracles in your description. "External inputs" are not external to the logic of the model, they are only external to some pre-defined subsystem within the model.

Again, this is why plans for perpetual motion machines are all "closed models" that obey all the laws of mechanics in the sense you are using the word. The "external input" is the guy standing behind the curtain churning the crank.
edit on 4-2-2012 by Darkwing01 because: (no reason given)



posted on Feb, 4 2012 @ 10:45 AM
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Originally posted by Darkwing01
I want you to commit to a model.


Heidi Klum?


What you ultimately want is for IWW to construct a replica of the WTC, because anything else won't do in your opinion. You've already derided computer simulations, without so much as a whimper of expertise in the matter. I do have that whimper of expertise in the matter, and I say you are mistaken.

Computer models are the only way to go, since only computer models can simulate on the scale required. If they are open source, nobody can appeal to obscurity if they don't like the outcome. They must follow up with scientific critique that addresses specific concerns rather than esoterics. NIST has not, in all cases, given us their parameters and the software used is closed source.

I find your support for the primitive collapse models proposed by truthers so far to be naive, and your neglect of e.g. this:

forums.randi.org...

and this:



...is unacceptable.
edit on 4-2-2012 by snowcrash911 because: (no reason given)



posted on Feb, 4 2012 @ 10:54 AM
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Originally posted by snowcrash911

Originally posted by Darkwing01
I want you to commit to a model.


Heidi Klum?


What you ultimately want is for IWW to construct a replica of the WTC, because anything else won't do in your opinion. You've already derided computer simulations, without so much as a whimper of expertise in the matter. I do have that whimper of expertise in the matter, and I say you are mistaken.

Computer models are the only way to go, since only computer models can simulate on the scale required. If they are open source, nobody can appeal to obscurity if they don't like the outcome. They must follow up with scientific critique that addresses specific concerns rather than esoterics. NIST has not, in all cases, given us their parameters and the software used is closed source.

I find your support for the primitive collapse models proposed by truthers so far to be naive, and your neglect of e.g. this:

forums.randi.org...


But if the computer model is accurate how can we possibly not be able to determine the tons of steel and tons of concrete on every level of the towers?

How could we possibly not determine if the core could hold itself up without the floors and perimeter?

I agree that an ACCURATE computer model is the way to go. But a computer model does not really do physics. It simulates physics according to its programming. So it can be just a complicated way to lie. We already know the Purdue simulation does not match a real building impact because the NIST measured the deflection and oscillation of the south tower due to the plane impact but Purdue's computer simulation does not move.

So what is everyone going to say if a good computer simulation will not collapse?

Could that be why we don't have one after TEN YEARS?


psik



posted on Feb, 4 2012 @ 11:00 AM
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reply to post by psikeyhackr
 





It does not change the fact that various SCIENTISTS and EXPERTS have not been demanding accurate steel and concrete distribution data on the towers for the last TEN YEARS.

Because they have it.



posted on Feb, 4 2012 @ 12:21 PM
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Originally posted by Darkwing01
reply to post by IrishWristwatch

Gah! The forum ate my enormous post...

Excellent.


First if you are sincere in your affirmations of the principles outlined above I apologize, I am not going to quote-mine old conversations.

I am sincere and I don't care about your apology. It means nothing.





Good enough. That will do, and you just said it can be done.


I have been trying to convince you of just this point for more than a year now and that is the best you can muster?

I see you can't muster the calculation you claimed you could do. Big surprise.



In real systems once the useful energy of a component is used it cannot be used again.

You mean when the mechanical energy is dissipated into thermal energy, it cannot be used to do mechanical work? Unless, of course, the thermal 'waste' heats a cylinder which expands a gas which pushes on a piston and does mechanical work.

You need to be clear what 'used' means in a thermodynamic context. Perhaps you'd like to be more precise in your terminology.


When the falling indestructible block passes through the building in Bazant's model it gains useful energy which is dissipated when the block itself is destroyed.

The block in Bazant's model is effectively rigid, not indestructible. That's your word you spuriously inserted into your interpretation of his model. Effectively rigid is not the same as rigid. Learn the difference.

In B&L, Bazant reworks the equations of motion without the assumption of rigidity for the crush down phase. The solution - for his initial conditions and assumptions - is that crush-up into the upper block occurs only until near the end of the peak plastic deformation phase, whereas it pushes past the plastic peak entirely on the lower section. That means the now compromised lower section is not capable of providing the same resistive force as the upper, so it crushes the now weaker section until the next 'impact'.

At next impact, conditions have become more favorable for exclusive crush down.

The reason this happens is because the initial defect story is fully compacted and is moving at an average speed of half the upper block speed, therefore has momentum at the time of first impact. The mass of the interstitial story applies force to the lower from its own static weight (mg) plus any change of its momentum on impact (d(mv)/dt). Therefore, the lower section experiences MORE force than the upper at first impact, and Newton's third law is obeyed at all points in the structure.

There goes the (stupid) Newton's 3rd law objections, out the window. These objections are stupid because all you have to do is READ the paper to see the upper block is not in direct contact with the lower, therefore the notion that the forces at their contact interface (which does not exist) must be equal and opposite is entirely meaningless. It's logically equivalent to demanding Newton's 3rd be obeyed at the contact interface of my fist in your face right now - we're not in contact.

Now, having called it stupid, I will tell you how I was stupid. I DID read the paper, but I missed the implication of the assumption of linearly distributed momentum in the initial crushed layer, and the implications for the initial conditions of the solution of the equation of motion. You see, all of my models (PLURAL) showed a propensity for bidrectional crush; not exclusively, but under a wide parametric range including conditions I felt were more representative than those where exclusive crush down occurred. Therefore I suspected his analysis to be in error, and set about replicating every jot and tittle of his setup to find the error. This was a part-time project, not a whole lot of hours total, but it stretched out over a couple of years.

Then, as I was re-reading to get some specific detail for the recreation, I saw it and got it. Damn. It was there all along, and it explains things perfectly. The project stopped right there, with me red-faced.

I don't find Bazant's initial conditions to be at all realistic, so I reject the conclusion in general, and naturally reject exclusive crush down for anything outside of those admittedly narrow and contrived conditions. All the same, his analysis is self-consistent, while you (who haven't read it) are trying to claim it isn't.

This justifies the assumption of a rigid block since it IS effectively rigid. Effectively rigid means strong enough to crush the lower, not indestructible. Shall we now proceed?


edit on 4-2-2012 by IrishWristwatch because: (no reason given)

edit on 4-2-2012 by IrishWristwatch because: (no reason given)



posted on Feb, 4 2012 @ 12:31 PM
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Originally posted by -PLB-
a pointless exercise.


Accounting for the laws of physics is only a pointless exercise in your mind PLB.

You have made that more than obvious.

You need to account for the 'equal opposite reaction', and 'momentum conservation', of the impacting floors.
Something we've been asking you to do ever since you started posting here. You haven't even made it clear you understand those laws, let alone address them.


edit on 2/4/2012 by ANOK because: typo



posted on Feb, 4 2012 @ 01:02 PM
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reply to post by ANOK
 


Its indeed a pointless exercise to explain simple physics to people who don't understand simple concepts such as a catenary, or who think that potential energy pushes up, or the top section can be without potential energy. The number of times I have explained it to you, with the result you just ignored the post without any response, is considerable. It is an interesting phenomena, people who are in denial.
edit on 4-2-2012 by -PLB- because: (no reason given)



posted on Feb, 4 2012 @ 01:02 PM
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Originally posted by Darkwing01


Good enough. That will do, and you just said it can be done.

At the first impact there is insufficient useful energy to destroy the block, the block consumes the building, gaining in useful energy as it does so.

Correct.


When it reaches the bottom there is no more useful energy to gain, so where does the additional useful energy to effect the transition from solid unbreakable rigid block to frangible collapsing body come from?

First off, it need not gain energy, it already HAS energy.

Your assertion is the same as saying that every bullet violates the laws of thermodynamics because it 'uses up' all its energy in the flight to its target and has none left to penetrate. It's exactly the same. Maybe you think there's some fundamental difference between traveling through air and crushing/accreting concrete and steel, but there is no difference in this regard. There are just forces.

Is it motionless when it hits bottom? No. What is the expression for energy of motion and what is this quantity called?

You've done nothing, no calculations and not even a hand wave, to show the energy has been 'used up' as in GONE. It isn't gone. YOU are violating the laws of physics by not adhering to conservation of energy!


All you have is the block now...

Along with its momentum.


...but in order for the block to be broken it must be subjected to a larger impact than each previous impact required to break each successive floor on the way down.

No - you forgot about the debris layer, which is also in motion until impacting bottom - the 'immutable' ground. The debris layer is what impacts the lower section. It is, as I explained above, THE reason for the survival of the upper section, even at first impact. Without it, there would be bidirectional crush in most circumstances.

The upper block, because of the thin debris layer, survives first impact. Each subsequent impact adds more debris layer and shields the upper block further, not only by virtue of physical barrier but more importantly by its inertia. In order to mediate a force from the lower to the upper block, the inertia of debris layer must first be overcome, that's force x distance, which is energy of mechanical work. This does happen, of course, but each successive impact results in less and less impulse actually applied to the upper block.

When the debris layer hits ground, ignoring further compaction, it is brought to rest immediately as it cannot penetrate the more rigid ground. The upper block crushes itself against the compacted debris like a bullet hitting armor.


You could move the transition up, but once the unbreakable block starts breaking it must progressively lose capacity to destroy the remaining structure, so slowing the collapse.

It is NOT unbreakable.

Capacity has nothing to do with the ability to destroy something, the impulse does. Rubble, according to the laws of physics of which you know nothing, can apply impulse, therefore can do damage.

Regardless, there IS a MUCH bigger impact at bottom than the initial. How do you miss it? By violation of conservation of energy; you magically and MIRACULOUSLY stop the moving block at the bottom without any application of force.

My models (PLURAL, and you'll have to go with mine because there are no other 2DOF crush models out there), show an increase in roofline velocity when birdirectional crushing occurs. I'm quite sure that violates your intuition, but don't feel too bad, I got that wrong, too. It does result in a slower crush front descent, which reaches ground later than the equivalent exclusive crush down, and that's where the intuition comes in. However, with the upper crush going concurrently in the beginning, the upper section is already crushed when the crush front hits bottom. In total, there is very little practical difference in the total collapse time.

Let's not lose sight of where you ****ed up in your exposition: you assumed there was no energy available to do mechanical work on the upper block at the end of crush down. You forgot it was moving very fast at that point, and had tremendous KE, and is now ramming compacted debris on ground (effectively rigid by comparison).

It then crushes up, simple as that. No violations of thermo, none of that. It can't withstand the impact. Just like a bullet which is still in motion can deform itself against a hard target, so the upper block crushes against ground.

I don't feel this 1D model captures collapse mechanics. I must've said that, oh, a thousand times already. But it is this model you're criticizing. You understand very little of it and, in the process of trying to unsuccessfully refute it, you committed an egregious violation of thermodynamic law - you threw a huge amount of energy away, arbitrarily. The reason is you have no clue how to do mechanics, and you can't even tell when you're making the biggest schoolboy error of all, failing to conserve energy.
edit on 4-2-2012 by IrishWristwatch because: (no reason given)



posted on Feb, 4 2012 @ 01:03 PM
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Originally posted by ANOK
You need to account for the 'equal opposite reaction', and 'momentum conservation', of the impacting floors.

Ironically, something I did in the post right above yours.



posted on Feb, 4 2012 @ 01:23 PM
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Originally posted by psikeyhackr
If by "composite slab and truss system" you are talking about the floor assembly outside of the corepsik

Of course I am.

Originally posted by psikeyhackr
I disagree. That had nothing to do with the structural strength of the core. The idea that the core needed anything outside of itself for support is nonsense.

You're just wrong about that.


Originally posted by psikeyhackrThe core provided the rigidity of the building. The perimeter columns provided the vertical support to the outer edge of the floor assemblies. The wind impacted the perimeter but the force was transferred to the core via the floor assemblies.
psik

All wrong and backwards. Look at any decent source. They will tell you the lateral forces were borne 95% by the Perimeter colums and spandrels. The core columns were designed to hold vertical loads only.


Originally posted by psikeyhackrThe difference between bending and buckling is so important. The "jargon" that experts insist on using is so much crap. The objective is to get as many people as possible to UNDERSTAND as much a possible.
psik


No doubt, jargon can be confusing and exclusive to outsiders. However, especially in structural design and analysis, precise use of language is a necessity. the term ,"bending" conveys much less information than the term "buckling". You'd do well to bone up on a little jargon so you could follow the conversations of experts.



posted on Feb, 4 2012 @ 01:34 PM
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Originally posted by Darkwing01
You ask what I want from you Irish?

I want you to commit to a model.

Well, thanks for telling me, but pardon me if I don't honor your request. I have MANY models, and I plan to add more, not reduce to one. The reasons are simple. Each model is crafted to answer a certain set of questions or explore a particular facet of dynamics. Many of the models have nothing directly to do with collapse at all (like 1D gases), but provide a computational means of exploring the dynamics of multibody sytems which are far too complicated for an analytic solution.

I use models to explore and learn, not satisfy your demented need to be right in a subject for which you have no skills.


You have your observations, and they are not getting any more precise.

You know, I stopped making measurements about three years ago. But, no, you wouldn't know that because YOU DON"T READ MY STUFF, you just criticize what you IMAGINE it to be.


The idea that there is some level of precision in measurement that will grant you insight is grand fallacy.

I've never said that it would, I'm not that stupid. The fact is, you have strenuously objected to ALL measurement and observation. You accept AE911Truth's talking points, like all three buildings fell at freefall, but reject measurements which show this to be unequivocally false.

You prefer the imaginary dynamics to REAL dynamics, because the imaginary dynamics dovetails with your preconceived belief the towers were demo'd. And you criticize me for being anti-scientific, because I've made measurements to show these beliefs false?

But let's not toss away precision.

Better precision is like putting on glasses when visual acuity is lacking. It reveals IMPORTANT details, such as whether or not local creeping motion preceded gross global motion. This is extremely important to resolve what happened, so that what happened can be modeled, not some imaginary AE91Truth or Darkwing bull****. You want a model? Helps to know WHAT you're modeling! Turns out, by having initial creep deformation displacement mapped, it was possible to fit the actual displacement to a textbook model of column creep buckling.

A fit does not mean the explanation is found, but it is suggestive and does effectively rule out mechanical deformation which cannot be fit to creep.

Beyond that, precision in measurement is paramount in this context. The mesurement being made is displacement versus time. In order to get velocity, you have to do first differences. Acceleration, second differences. Each differencing emphasizes error over signal, such that the acceleration trace from video will be horrendously noisy - you won't even see the signal without filtering (+/- 2500 g's, anyone?). Increased precision mitigates this problem and allows me to finally say AE911Truth is full of ****.

Those with skills in this field know this, and would never disdain greater precision.

Nevertheless, the period of measurement (for me) has been mostly done for years, but you have no clue of that.


I want you to move on to the next step in the scientific method: Postulate a theory and test it.

I've got a better idea: you want it, YOU do it. Not that I haven't done this very thing time and time again, which you've studiously ignored, but I do it to analyze and solve small (tractable) problems. In doing so, I've gained more insight into the larger problem than you will ever hope to have. I have no interest in some overarching theory, even if you do. By all means, overstretch the bounds of what's reasonably possible, if you like. But it will be your time wasted, not mine.



posted on Feb, 4 2012 @ 01:38 PM
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Originally posted by IrishWristwatch

Originally posted by ANOK
You need to account for the 'equal opposite reaction', and 'momentum conservation', of the impacting floors.

Ironically, something I did in the post right above yours.


It seems to me that disconnect is due to the fact that some view a hammer resting on a nail the same as a hammer that has been swung to hit the nail. They are using the same equations to model/explain the forces at time of impact. I think that once that it is understood to be a different physical system and requires different analysis then the "physics were violated" meme will go away. Also I think I'm oversimplifying the two models which means my statements are not strictly true from an engineering/science perspective but may be close enough from a conceptual grasp perspective.



posted on Feb, 4 2012 @ 02:03 PM
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Originally posted by Darkwing01
Even if there is more accurate data to be gained simply interpreting historical data as being caused by gravity is not scientific.

But, Darkwing, I don't do that. I don't put the cart before the horse. If you ask me "is it possible for gravity alone to be responsible for the collapse progression observed?", my answer will be "I believe it is possible based on analysis to this point." If you ask me "did gravity alone cause the collapse progression observed?" my answer would be "I don't know, but I believe so."

Huge ****ing difference. You get it? So, why are you saying these things? Do you presume, because I (sometimes) correct the fallacy that Newton's 3rd means 'equal and opposite destruction', that I believe gravity-driven collapse is proven? Have you ever heard me say that? No, you haven't, because I haven't.

I can't deny that an overloaded floor can fail. That's not only unscientific, it's stupid. I can't deny there is sufficient potential energy to account for overloading steel columns. I can't deny that it was a messy collapse and design FOS is meaningless. But I also can't claim gravity-driven collapse is proven, and I don't.

So, why do you ride my ass on this point?


You have to pick your position BEFORE you start to measure and look for data that FALSIFIES your position.

More pseudoscientific bull****. Does it matter if the precession of Mercury's orbit was known prior to or after the formulation of General Relativity? Predictability of a theory is independent of any and all observations made. Measurements can be made anytime, and excluded from consideration as needed. Working scientists know this.

All the same, my work in measurements is entirely unrelated to my work in mechanical modeling. I have NEVER applied measurements to my models or vice versa. The models are constructed and trials run without ever considering actual data in ANY way. That there happens to be a good fit here and there may be unavoidably noticeable, but no effort is ever made to link the two, let alone drive a model by data. EVER.

The reason you don't know this, and assume the complete opposite, is because you have no idea what I do and have no interest in remedying that. Fine. But you can't criticize what you don't know. You take very precise aim on strawmen, time and time again.

If I did what you say, that would be one thing. But I don't. Wake the **** up, I've been telling you this for more than a year. It's gotten very tiresome and regrettably I've just burned another hour repeating myself.


Once the measurements are in you cannot use those measurements anymore to test your theory.

Yes, but now that I've told you for the nth time that I don't do that, can you finally give it a rest?


You may be wrong, but that is the risk.

I'm wrong at least half the time. It doesn't bother me in the least, I simply strive to be as correct as possible. If I'm wrong, and you can show me, I don't fight it. So far, you've never shown me wrong because you've never addressed my methods, only the methods you ascribe to me out of ignorance and thin air.


Sitting on the sidelines and sniping at everybody else's ideas while you refuse to commit yourself to a position is a cop-out and sheer intellectual laziness in my opinion.

You're welcome to your opinion, but I do not value it at all. You are utterly incompetent in all things science and engineering and are a poster boy for flaming pseudoscience. I don't want your approval, because it would suggest I'm doing something wrong, as you are almost always 180 degrees off the mark. You are a walking litmus test for wrong.

To say that I sit on the sidelines when you've never contributed a single thing to this subject is just more of the same trademark offensive Darkwing prattle. You don't know what I've done, you prove that every time you type.

My refusal to commit, as you call it, is simply an admission of things I don't know, because there is plenty I don't know (even though I know a hell of a lot more than you). It is necessary humility; I don't have the all answers, only some and not enough to make a grand theory. You, on the other hand, could do with some of that humility. You believe you already have the big answer without ANY observation or analysis.

So you're all up in arms because some "internet hero" has thus far not put forth the Grand Theory of All Things 9/11? Get a life.
edit on 4-2-2012 by IrishWristwatch because: (no reason given)



posted on Feb, 4 2012 @ 02:33 PM
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Originally posted by Darkwing01
reply to post by IrishWristwatch
 




3) That a conceptual model that requires (or implies) a decrease in entropy in a system is always incomplete even if the system is not closed in reality.


Do not agree for the general case. If the system is open with external inputs defined, there can be a decrease of entropy within the system boundary. That's what external inputs are about! If you meant that an open system which has no external input defined which can legitimately account for entropy decrease is an incomplete description, I agree.


Wait, what?

I missed this one.

There is no such thing as a logically valid open conceptual model Irish.

'System' and 'model' are not synonymous in this context. A model may be of an open system or a closed system, and logical closure of the model is an entirely different thing than open or closed systems.

There really is no such thing as a true isolated system, except perhaps the universe as a whole, although many systems fairly well approximate a closed system. When open systems are studied, boundary conditions are defined which account for the matter and energy exchange across the boundaries of the system. This provides logical closure for the model, though the system remains open.

I'm sick of playing remedial science tutor. Battle of scientific wits with an unarmed man. Go back. Read. Study. Learn. Then I won't have to hand you your ass on a daily basis, because we'll be on the same page - the page which the scientific community at large is on.

You seem to think having a coffee table book by Penrose and Wikipedia at your fingertips a scientist makes. Not in your case.


Either it conforms to the laws of logic and it is closed (which is another way of saying it conforms to the laws of logic) or it does not.

You really haven't taken the "paradox of analysis" thing to heart have you?

It doesn't apply to what I do, only what you think I do.


This is why I say that you expect to defy logic with math.

Above I explained why a statement like this is based on a false premise. If I DID the things you say, I would be guilty of the (legitimate, though not gulity of illegitimate) infractions you claim. But I don't, and I'm not.

If you persist in clinging to this false notion, you can easily put to rest the question of which of us is right: SHOW ONE INSTANCE WHERE I'VE DEFIED LOGIC WITH MATH.


...you can't include miracles in your description.

Strawman again. SHOW ONE INSTANCE WHERE I'VE INCLUDED MIRACLES.


"External inputs" are not external to the logic of the model, they are only external to some pre-defined subsystem within the model.

NO NO NO! See above. Model and system are not the same. The model models the system, the sytem is modeled by the model. External inputs are part of the boundary conditions of the system, both of which are part of the model. The whole is not the same as its parts.


Again, this is why plans for perpetual motion machines are all "closed models" that obey all the laws of mechanics in the sense you are using the word. The "external input" is the guy standing behind the curtain churning the crank.

Failure to account for boundary conditions is a classic and common mistake. That does not change the nature of the system itself. Once the guy churning the crank is accounted for either by extending the system boundaries OR as a boundary condition imposed externally on the system. the paradox is resolved. As someone who has zero experience in the application of the scientific method, you erroneously believe only the first option exists when the second option not only exists, it is typically used.

Here's some irony:

In making your (incoherent) argument based on entropy, not the first one but the second one, you made this mistake. You treat the towers as an isolated system, ignoring the boundary condition of coupling to ground, and arrive at a paradox exactly like the perpetual motion machine. You accuse Bazant of being in error because you think his model proposes a perpetual motion machine because YOU failed to include the guy churning the crank as a boundary condition. But he didn't.
edit on 4-2-2012 by IrishWristwatch because: (no reason given)



posted on Feb, 4 2012 @ 02:46 PM
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Originally posted by huh2142

Originally posted by IrishWristwatch

Originally posted by ANOK
You need to account for the 'equal opposite reaction', and 'momentum conservation', of the impacting floors.

Ironically, something I did in the post right above yours.


It seems to me that disconnect is due to the fact that some view a hammer resting on a nail the same as a hammer that has been swung to hit the nail. They are using the same equations to model/explain the forces at time of impact. I think that once that it is understood to be a different physical system and requires different analysis then the "physics were violated" meme will go away. Also I think I'm oversimplifying the two models which means my statements are not strictly true from an engineering/science perspective but may be close enough from a conceptual grasp perspective.

You've hit the nail on the head, so to speak!

This is exactly Darkwing's mistake: he believes the energy of the hammer is used up swinging through the air, therefore it magically comes to rest at bottom with no impulse.

"But, but, but, ..."

No buts. Even though structure is being crushed versus air being pushed out of the way, the analogy holds. There is a resistive force, being it air drag or structural/inertial resistance. It is only the magnitude of these force that dictate the swing of the hammer or the crush down. If velocity remains at final impact, there will be impulse.



posted on Feb, 4 2012 @ 03:14 PM
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Darkwing, I told you once that, of all the people I've run across who've rejected what the engineering mechanics community has to say about the collapses, you are best equipped intellectually to get over the hump and see why the accusations of physics violations don't hold up.

That was a long time ago, when I was impressed with your vocabulary. A lot has transpired since then to convince me I was totally wrong in that initial impression. You may indeed have to intellect to figure out where you are (so) wrong on all these points we discuss, but I doubt that your ego and stubborn nature will allow this to happen.

I argue with some of what you say because you are making accusations against me which don't apply. If they did apply, you would be correct. This is my first frustration. You don't know what I do, but you presume to know and are wrong. This has nothing to do with intellect and everything to do with willful ignorance.

I argue with the rest of it because you are simply wrong in those cases. Like conflating the model with the system being modeled, or thinking Bazant violated physical laws, or miraculously assuming the upper block stops without impulse. These are very bad mistakes, and show you have no skill whatsoever in these subjects. Yet, your ego tells you that you not only understand these principles without A) ever learning them and B) without ever working with them, it tells you that you know them better than I because you're so ********* smart that you absolutely couldn't be wrong!

Together, these two categories of wrong account for almost everything you've ever said to me.

Most of this has been said on both sides umpteen times. You are never going to understand physics, engineering mechanics, or my work. Not that you don't have the intellect, you've shown you haven't the desire.

Enjoy your tilting at windmills.
edit on 4-2-2012 by IrishWristwatch because: (no reason given)



posted on Feb, 4 2012 @ 03:20 PM
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Oh, and by the way, I gave you the suspension at 9/11 Forum, I didn't "pussy out" and have someone else do it. You think I'm afraid to push a button? I let you hang on there without suspension so long to avoid the appearance of bias, but after a point I lost sight that my greater obligation is to protect the forum from the tyranny of one.

You're not banned, just suspended for 90 days. Your suspension ends on April 1st. Please feel free to indulge in any unintentionally ironic posting at that time.



posted on Feb, 4 2012 @ 04:08 PM
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Originally posted by DrEugeneFixer

Originally posted by psikeyhackr
If by "composite slab and truss system" you are talking about the floor assembly outside of the corepsik

Of course I am.

Originally posted by psikeyhackr
I disagree. That had nothing to do with the structural strength of the core. The idea that the core needed anything outside of itself for support is nonsense.

You're just wrong about that.


Originally posted by psikeyhackrThe core provided the rigidity of the building. The perimeter columns provided the vertical support to the outer edge of the floor assemblies. The wind impacted the perimeter but the force was transferred to the core via the floor assemblies.
psik

All wrong and backwards. Look at any decent source. They will tell you the lateral forces were borne 95% by the Perimeter colums and spandrels. The core columns were designed to hold vertical loads only.


I have seen a number of sources making such idiotic claims. They are obviously full of crap.

The perimeter columns and spandrels are four two-dimensional arrays of steel. They can withstand forces from directions parallel to the surface. The downward force due to gravity from all of the attached floors is the primary one. A perpendicular force would make them bend. The concrete slabs were a big square donuts. If the core applied outward stress on opposite sides it would cause cracks in the floor. The core was a THREE-dimensional array of steel It could take stresses from any direction, like from the wind. The wind impacted the perimeter. But the force was transferred to the core via the floor assemblies. And the visco-elastic dampers attached to each end of all of the trusses helped absorb energy to damp out the building's oscillation begun by the wind under normal circumstances.

We are being handed tons of BS about those buildings when the physics is quite elementary.

psik



posted on Feb, 4 2012 @ 04:47 PM
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Originally posted by IrishWristwatch
Ironically, something I did in the post right above yours.


And yet hilariously you didn't.

Bazant does not account for the fact that the top would receive as much damage as the bottom during impact.

You can't just throw Newtons 3rd law away, and pretend it doesn't matter because of momentum, that is completely stupid. Momentum will change the forces on BOTH objects, the forces are ALWAYS equal...


For every action, there is an equal and opposite reaction.

The statement means that in every interaction, there is a pair of forces acting on the two interacting objects. The size of the forces on the first object equals the size of the force on the second object. The direction of the force on the first object is opposite to the direction of the force on the second object. Forces always come in pairs - equal and opposite action-reaction force pairs.

www.physicsclassroom.com...

Bazant ignores that, or more accurately wiggles around it, you are making excuses for it.

When a hammer hits a nail the forces on the hammer and the nail are the same, equal opposite reaction. If you hammer a nail into wood, the forces between the nail and the wood are equal, it will be driven in because the nail has more mass than the wood. Try driving a nail into steel, the nail will bend, you can't drive the nail into something with more or equal mass (Mass being the density of molecules, mass per unit volume, not weight). When two floors impact each other the forces on both are equal, the difference is MASS (and other variables that are not relevant in this context).


edit on 2/4/2012 by ANOK because: typo



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