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gyroscope
(1,443 posts)- cars and trucks smash into each other without slowing or stopping
(car A just keeps moving right through car B without slowing at all as if the latter were made of paper and disintegrates into dust)
- billiard balls strike each other without slowing or stopping.
- the top half of a building falls through the lower half, at freefall speed, without slowing or stopping...without the aid of CD.
- the precision art of controlled demolition is rendered obsolete, as is common sense along with Newtonian physics. from now on to bring down a modern high-rise neatly and symmetrically more or less into its own footprint, all you need is a cigarette lighter and a can of gasoline or kerosene.
- NIST scientists are awarded the Nobel Prize for discovering new laws of physics. Newton's laws of motion are renamed the Bush Laws of Motion. If they can give one to Obama for peace, why not?
wildbilln864
(13,382 posts)
gyroscope
(1,443 posts)to demonstrate how everything changed on 9/11, including the laws of physics.
that explains it! lmao
(The Who has one too)
newfie11
(8,159 posts)The non believers will be here soon, beware.
William Seger
(11,047 posts)... he says, and then proceeds to do exactly that. 
gyroscope
(1,443 posts)like calling you a genius for instance.
when you finally figure that out your beautiful mind may explode like a ripe melon, or the twin towers. 
William Seger
(11,047 posts)... which is why his schoolbus analogy broke my irony meter.
It isn't just the rather obvious structural differences between a schoolbus and the WTC towers, or the difference that scale makes, that make the analogy so absurd, although those are certainly relevant. The irony is that this guy is so completely clueless about the basic nature of the problem yet is pretending to understand physics. To a physicist, the question of whether an impacting object would destroy the impacted object is not answered by silly and invalid analogies. It's just a question of how much energy was involved in the impact and how much would be necessary to do the destruction. What if the VW was moving at 500 mph; would that be enough momentum and impact energy to destroy the schoolbus? A physicist would attempt to estimate the forces and resistances involved in a particular case to answer the question, whereas this guy doesn't seem to understand why that's necessary. And if he doesn't even understand that concept, then it isn't surprising that he doesn't understand Bazant's argument for why total collapse was unavoidable after it got started.
But the real irony of his "lesson" is that his "students" apparently don't understand it either.
gyroscope
(1,443 posts)he isn't comparing cars to buildings. he's comparing a car to another vehicle.
when a car collides with another vehicle it will be halted in its tracks.
it doesn't just keep going after the impact, without drastically slowing.
apparently you've been watching too many cartoons.
any two objects of similar structure and materials cannot fall through the other as if the other wasn't there.
the top half of a building cannot freefall through the bottom half, destroying it in the process UNLESS:
1. the lower half was made of jello
2. it was compromised by timed explosive devices placed at key locations (CD)
3. you believe in cartoon physics
if you believe otherwise, then provide a real life example. this should be good.
William Seger
(11,047 posts)... and you completely ignored my reasons for saying that. An example? If your imaginary physics were valid, then this would be impossible:
Verinage demolitions work without explosives by simply dropping the top of the building onto the bottom. Obviously, your imaginary physics don't explain the real world.
gyroscope
(1,443 posts)Last edited Thu Nov 13, 2014, 02:05 PM - Edit history (1)
you just proved the case for CD at the WTC, because verinage is a type of controlled demolition. they just use non-explosive means to pre-weaken the supports. and the method does not work on steel-frame buildings, only on buildings made of brick or concrete masonry.
William Seger
(11,047 posts)the top half of a building cannot freefall through the bottom half, destroying it in the process UNLESS:
1. the lower half was made of jello
2. it was compromised by timed explosive devices placed at key locations (CD)
3. you believe in cartoon physics
Verinage demolition uses hydraulic jacks and cables to collapse parallel load-bearing walls, after which gravity alone proceeds to do exactly that which you claim is impossible. Since it works by pulling in parallel walls, of course that means it's limited to structures with load-bearing walls. That's what excludes using it on steel-framed structures, not Gyro's Law. You deliberately fail to understand how much impact force is generated by having that much mass fall even one story, and how far beyond the capacity of the typical building it would be. Any competent structural engineer will tell you that buildings are simply not designed to withstand that sort of abuse, but you'd rather invent imaginary physics to protect your delusions.
> you just proved the case for CD at the WTC, because verinage is a type of controlled demolition.
I defy you to restate that conclusion in the form of a logical argument, because that certainly isn't one.
gyroscope
(1,443 posts)the building in your video did not collapse because of fire. the point is devices were used in key locations to weaken the supports and initiate a symmetrical collapse, just as with any other controlled demolition.
give an example where fire has caused a building to collapse on itself (without any kind of CD) completely and symmetrically and you would have an argument.
rewinn
(23 posts)...of any visible significance?
The mass of an airliner, even one going 500 MPH, is not enough to move the mass of WTC very much.
It takes energy to move a building. Where would the energy to create an assymetry come from?
You may be fooled by the fact that at human scales, such as boxes of Cheerios or refrigerators, things topple over if you push them hard enough. But WTC is a lot heavier than a fridge.
(Moreover, if a building were to start to topple over, the unsupported part would fall, ending the topple, because walls are not built strong enough to bear the buildings above them at a crazy wrong angle. That's just physics.)
wildbilln864
(13,382 posts)
goddamn that's got to be the most ridiculous nonsense I've seen written here lately! Congratulations and welcome to the DUngeon. Response to wildbilln864 (Reply #42)
rewinn This message was self-deleted by its author.
rewinn
(23 posts)...people who don't know physics keep insisting that there's something suspicious because stuff falls down.
They insist the top 30 floors of WTC should have rotated at the point of impact and maintained its structural integrity so that it came sideways in one piece.
Just thinking how the building would have had to be constructed to do that makes one laugh. It's certainly POSSIBLE to build walls that keep 30 stories together at a 45 degree angle, but you have to design for it.
wildbilln864
(13,382 posts)over 2300 architects & engineers disagree with you. 
zappaman
(20,617 posts)
OBenario
(604 posts)Of course not.
wildbilln864
(13,382 posts)the collapses were like sledge hammers hitting Steuben glass? That one really cracked me up!
William Seger
(11,047 posts)... that once the collapse started, there was nothing that could prevent total collapse. After 13 years, the idiocy of this video isn't much worse than even the best arguments the "truth movement" has come up with to disbelieve that conclusion.
gyroscope
(1,443 posts)and proven wrong.
once the process is started, total or symmetrical collapse is certainly not inevitable.
William Seger
(11,047 posts)... and furthermore, his arguments are logically sound, unlike Gyro's Law and the other imaginary physics you've posted, or anything yet produced by Gage's "experts." Someone who doesn't even understand Bazant's arguments is in no position to even discuss them intelligently, much less refute them. Calling Bazant an idiot just because he contradicts your imaginary physics tells us something about you, not about Bazant.
As for this video, let me repeat what I said before: To a physicist, the question of whether an impacting object would destroy the impacted object is not answered by silly and invalid analogies. It's just a question of how much energy was involved in the impact and how much would be necessary to do the destruction. A physicist would attempt to estimate the forces and resistances involved in a particular case to answer the question. Like the "professor" in your OP video, you don't seem to grasp that simple and obvious point, yet you call someone who has done exactly that an idiot.
OBenario
(604 posts)No, he isn't. He's barely known outside US borders.
William Seger
(11,047 posts)https://en.wikipedia.org/wiki/Zden%C4%9Bk_Ba%C5%BEant
wildbilln864
(13,382 posts)paid some tool to write it!
wildbilln864
(13,382 posts)Bazant is wrong! Either incompetently or criminally!
William Seger
(11,047 posts)... underestimating the strength of a particular structure. The irony here is that successful demolitions demonstrate that Bazant is quite correct about what happens when the falling building (regardless of why it started falling) generates more impact force than the structure can absorb: Blowing out some columns starts the fall but gravity does the rest. Gage's "experts" have had 13 years now to become instantly famous by demonstrating that the WTC towers had enough strength to withstand even a one-floor collapse. If you believe Bazant seriously underestimates the strength of the WTC towers, let's see a better one. There's a reason you and gyroscope can't find a scientifically valid argument that contradict's Bazant's conclusion: It doesn't exist. So, instead we get Gyro's Law. 
eomer
(3,845 posts)He didn't do any calculations to determine whether the top would crush the bottom. He instead just assumed it. Nothing there to refute - he just assumed what he wanted to be true, without demonstrating it.
Not going to go into depth on this - as you're aware we've been through this here in this group. But I don't want your statement to stand without saying I disagree with it.
William Seger
(11,047 posts)What Bazant assumed was the collapse initiation: The load redistributions after columns were destroyed by the plane impact caused some columns to be loaded to near their limit, which was followed by viscoplastic (creep) buckling caused by the heat of the fires.
> He didn't do any calculations to determine whether the top would crush the bottom.
Yes he did exactly that, even in his first paper:
...
The details of the failure process after the decisive initial trigger that sets the upper part in motion are of course very complicated and their clarification would require large computer simulations. For example, the upper part of one tower is tilting as it begins to fall (Appendix II); the distribution of impact forces among the underlying columns of the framed tube and the core, and between the columns and the floor-supporting trusses, is highly nonuniform; etc. However, a computer is not necessary to conclude that the collapse of the majority of columns of one floor must have caused the whole tower to collapse. This may be demonstrated by the following elementary calculations, in which simplifying assumptions most optimistic in regard to survival are made. (Emphasis added)
That introduction is followed by calculations that show that the energy that would need to be absorbed was more than 8 times what the columns could have absorbed under optimistic assumptions. You can "disagree" with his calculations and his argument all you like, but I won't let your denial that they even exist stand without saying that you are simply wrong.
eomer
(3,845 posts)What they did instead was assume a highly idealized proxy and then they did calculations of that idealized model. But what they didn't do was demonstrate that the proxy says anything definite about what the real life process would have done. They claim to have established a limiting case by making assumptions that only go against collapse but that's not true. They assume that the top piece imparts all its force onto the lower part at one single instant, as a rigid monolithic object. This assumption is clearly not true and it clearly goes in favor of collapse of the idealized model, not against collapse. So in fact they have a combination of some assumptions that go against collapse and at least one major one that goes in favor of collapse. They have provided no answer for how one would resolve those assumptions working in opposite directions against each other and see what would happen in the real physical process. It is smoke and mirrors, designed to seem physics-y but is not a calculation of the actual physical reality and not a real limiting case since their statement about assumptions all going against them is not true.
AZCat
(8,345 posts)The assumption about the top piece and the bottom piece instantaneously impacting is in favor of collapse arrest, in my opinion, because it increases the bottom portion's ability to resist the force as that force is spread across the entire impact face. A non-simultaneous impact would result in force being applied to individual members in the bottom part in succession rather than concert, and therefore would increase the chances of failure and collapse continuation because it is much easier to overload a single structural member than it is to overload several.
William Seger
(11,047 posts)> They assume that the top piece imparts all its force onto the lower part at one single instant, as a rigid monolithic object. This assumption is clearly not true and it clearly goes in favor of collapse of the idealized model, not against collapse.
If you believe that, then here is the specific part of Bazant's argument that you need to address:
forces, it would fail under any other distribution.
As I said, you can disagree all you like, but you can't use your own contradiction as proof that "Bazant has no argument that needs refuting." Yes he does, and you haven't done so.
In order to halt the collapse, all of the kinetic energy of the falling mass needs to be absorbed or dissipated, so Bazant and Zhou take the crushing of all the columns on one floor as the limiting case that absorbs the most energy. If you know how the structure could absorb more energy than that in that initial collision, you haven't shared it. Their calculations then show that the total kinetic energy available in the top block was 8.4 times more than the column could resist. (And that, by the way, is irrespective of the "equal and opposite reaction" in the top block.) That calculation does not "assume that the top piece imparts all its force onto the lower part at one single instant, as a rigid monolithic object." Rather, it shows how much excess energy must go somewhere if the collapse is to be halted. Hand-waving doesn't make it disappear.
eomer
(3,845 posts)Their highly idealized model is not based on the maximum ability of the lower structure to resist all the kinetic energy. Rather it is based on the maximum ability of the lower structure to resist all the kinetic energy if it were delivered all at a single instant.
Here is a different way of thinking about it that shows their flaw. Assume that you can remove the upper structure and cut it into very small pieces. Then assume that you can drop each of those pieces, one at a time, from the appropriate height above the lower structure, approximately one floor's height, onto the lower structure. This will take a long time but when you've finished the lower structure will have absorbed the same amount of kinetic energy that Bazant purportedly proved it can't.
Clearly if that same amount of kinetic energy is delivered in this fashion the lower structure has no problem resisting it. No columns will be crushed. Why is this result different than Bazant's? Because Bazant assumes, without justification, that all the kinetic energy is delivered at one single instant. But the result under that assumption is not necessarily the same as the result if application of the kinetic energy is spread out over time.
Bazant has not demonstrated, has not attempted to demonstrate, the relationship between his idealized model that unrealistically delivers all the kinetic energy at once and the real life process in which the kinetic energy was delivered over some span of time.
cpwm17
(3,829 posts)In an idealized symmetrical collapse, the energy of the collapse would be spread out evenly throughout the lower structure, maximizing the ability of the lower structure to resist collapse.
In an asymmetrical collapse, as happens in the real world, the same kinetic energy will focus its destructive powers on a much smaller area of the lower structure, greatly reducing the ability of the lower structure to resist collapse.
The potential energy of different sections of the top structure aren't going to magically wait their turns. Once the supporting columns for a floor are greatly compromised, and the collapse begins, the potential energy of the top structure very quickly gets turned into kinetic energy.
eomer
(3,845 posts)It's purpose was to debunk a very specific claim and nothing other than that. The claim it debunks is that the lower part had to collapse due to the kinetic energy of the top part, no matter how that kinetic energy was applied. That claim is clearly not true, as demonstrated by cutting it up into many small parts and dropping them sequentially. Same amount of kinetic energy, no collapse, claim debunked.
But of course the different sections aren't really going to wait their turns. The hypothetical wasn't trying to say anything at all about how the real event would play out.
What seems to me would have happened in the real event is that the columns of the lower part would mostly pierce the upper part and the columns of the upper part would mostly pierce the lower part. Many of them would probably be broken by sideways and twisting forces and few if any would buckle by being subjected to the kind of straight on energy that the idealized model assumes. And I think the lower part would likely be crushed and collapse would likely occur. That's my own personal best guess as a layperson of what would have happened. But to demonstrate through engineering principles that it definitely would have happened has not been accomplished by Bazant. He has done some somewhat fancy calculations but hasn't demonstrated the relationship between those calculations and the real event. He assumed the relationship to be that of a limiting case but he hasn't shown why that has to be the case.
William Seger
(11,047 posts)> ... that it definitely would have happened has not been accomplished by Bazant. He has done some somewhat fancy calculations but hasn't demonstrated the relationship between those calculations and the real event. He assumed the relationship to be that of a limiting case but he hasn't shown why that has to be the case.
That's why I say that you've never understood his argument. What his calculations show is that even if all of the columns had been able to absorb a maximum amount of energy by buckling, that would have not have been nearly enough to halt the collapse, and all the "real event" failure modes would have absorbed even less energy. Arguing about how his simplified model is not "realistic" completely misses the point: His argument is that there is no "realistic" scenario that could have possibly absorbed all that energy. The only challenges I've seen to that argument, which certainly is based on engineering principles, are based on hand-waving assertions, imaginary physics and personal incredulity.
William Seger
(11,047 posts)If you drop the building one piece at at time, then the structure has time to absorb the kinetic energy as strain energy and then release it again by rebounding like a spring. That's not what happened. Bazant does not need to assume that the energy was delivered "all at a single instant." He only needs to assume that it was delivered before the columns could rebound; otherwise, the strain energy simply accumulates as more load is added. If you think that's the flaw in his argument, then you are the one in need of a demonstration: Explain how, in that first collision of the entire falling top block with the intact structure, the columns had any time to rebound.
Furthermore, once again, the calculation simply compares the total kinetic energy to the maximum that could be dissipated by column buckling. It does not "assume" that 8.4 times load capacity was actually delivered to any column "all at a single instant" or spread out over time. Regardless of how you spread it over time or over the entire 3D structure, that's how much energy needs to be absorbed or dissipated, one way or another, or else the collapse must continue. You have not even begun to challenge Bazant's estimate of how much energy total column buckling could dissipate or his justification for using that estimate as a limiting-case maximum. You have simply claimed that "Bazant has no argument that needs refuting" and when challenged on that, only pretended to have a refutation.
eomer
(3,845 posts)that it matters over what time span the energy is delivered. It seems we've agreed on that. So now we've move past (by abandoning it) the earlier claim that the kinetic energy of the upper part had to collapse the lower part no matter how it was delivered. That claim was clearly incorrect.
Now the claim (which isn't Bazant's claim) is that we can assume that all the kinetic energy of the upper part was delivered in less time than it would take the lower part columns to rebound. I don't see how anyone can justify such an assumption. If it went against collapse then maybe there's an argument but it doesn't - it goes in favor of collapse. And we know that in the chaotic real life event it obviously wasn't true in at least some cases. In some cases the structures of the upper part would have failed first so that they would have delivered some fractional part of the overall kinetic energy during this new time interval that we're considering. So if in some cases in real life it wasn't the case then what justification can we find for assuming it in the idealized proxy? I'm not seeing it. In any event this isn't what Bazant's idealized model was based on.
William Seger
(11,047 posts)> So now we've move past (by abandoning it) the earlier claim that the kinetic energy of the upper part had to collapse the lower part no matter how it was delivered. That claim was clearly incorrect
You persist in arguing against straw-men. What I've said, repeatedly, is that all the energy must go somewhere in order to halt the collapse, which is quite true even if you spread it over any amount of time. Yes, if you do it in pieces such that no single impact is large enough to push the columns into plastic deformation and then allow them to rebound before dropping more, then yes collapse would be avoided. My claim is, then, so what? That has nothing to do with what actually happened: the whole top block fell at the same time.
> Now the claim (which isn't Bazant's claim) is that we can assume that all the kinetic energy of the upper part was delivered in less time than it would take the lower part columns to rebound.
That's two straw-men: (1) It isn't just a matter of spreading the energy transfer over time, because rebounding would also require periods when there was no force to resist rebounding; and (2), once again, there is no assumption that "all the kinetic energy of the upper part was delivered." Despite your repeated assertions that Bazant's analysis "assumes" all of it was delivered, what it actually shows is that only 1/8th of the total energy would be enough to crush all the columns, so that's all that needs to be transferred to justify the conclusion. So, at least you are correct that it isn't Bazant's claim either.
> I don't see how anyone can justify such an assumption.
In a word: momentum. If a column could not completely absorb or dissipate the energy transferred in the initial collision, then momentum would carry the falling mass right through the failing column, giving it no opportunity to rebound.
> In some cases the structures of the upper part would have failed first so that they would have delivered some fractional part of the overall kinetic energy during this new time interval that we're considering.
And again, "some fractional part of the overall kinetic energy" would be all that's necessary to crush all the columns.
> So if in some cases in real life it wasn't the case then what justification can we find for assuming it in the idealized proxy?
Because you haven't proposed any realistic way that all of the kinetic energy could possibly have been absorbed or dissipated, which is the crux of Bazant's argument. It's one thing to imagine (without evidence) that there were localized cases where the initial impact force was less than the failure load and then a column had some time to rebound before being hit again, but you have not even begun to demonstrate a realistic scenario where that mechanism could dissipate enough energy to make a difference in Bazant's conclusion. Assuming that not all of the available energy was transferred in the initial collision doesn't doesn't really do the trick, because any energy that wasn't transferred in that initial collision was still available for the next collision.
Any time that you base a conclusion on a simplified model, you should ask if the conclusion might be changed by a more precise model. If the collapse/no-collapse decision here was a close call, then we should indeed make the model more comprehensive and realistic before deciding. But it's nowhere near being a close call, which is the basis of Bazant's conclusion that total collapse was unavoidable -- not any assumption that "the top piece imparts all its force onto the lower part at one single instant, as a rigid monolithic object," as you misrepresented the argument. To make a more realistic model, you would need to include cases where floors and beams were ripped from columns -- failure modes that happened precisely because they required less energy than buckling the column that supported them. That is Bazant's justification for taking full column buckling as the upper-bound limit for how much energy could be dissipated. If you think you can dissipate any significant amount of energy by rebounding, then I'm afraid you'll need to show your work.
William Seger
(11,047 posts)The B&Z paper does have an elastic dynamic analysis, by the way. It's relevant to your rebound hypothesis because the only energy that could be dissipated by rebounding is the energy that was stored elastically, before reaching the "yield" point where plastic deformations won't rebound (by definition). B&Z give a rough estimate that the total energy of the top block was 31 times more than the columns could absorb elastically, if all of them were stressed to their maximum elastic limit. Even if all of that energy was dissipated by elastic rebounding, it wouldn't matter to the B&Z calculation of how much energy could be absorbed by plastic deformation -- less than 1/8th of the total energy -- so it does not actually affect the conclusion that collapse was inevitable.
wildbilln864
(13,382 posts)fucking unscientific nonsense! Bazant and Zhou are fucking liars and buffoons!
zappaman
(20,617 posts)Really a fantastic reply to the thoughtful, detailed information by Seger.
13 years and still nothing?
No wonder you're frustrated!
gyroscope
(1,443 posts)who starts with a conclusion and tries to twist everything to fit that conclusion, while totally ignoring the relevant facts.
that's not science, its science fiction.
Gee I wonder what Bazant has to say about the unprecedented total collapse of Building 7?
"Oops no plane hit Bldg 7, there goes our stupid pancaking/pile driver theory, so lets just
ignore it and hope no one notices."
AZCat
(8,345 posts)It's been a decade of slightly mystified frustration. There's nothing like discussing something technical with a layperson who is convinced their time spent watching YouTube videos trumps your professional expertise to make you feel somewhat pessimistic about the human race.
You can't even spell buffoon right.
You CT truther's amuse me to no end.
13 years later and you're still trying to push this nonsense, meanwhile, the rest of America has moved on.
William Seger
(11,047 posts)...and the WTC towers were probably two-floor collapses. Your reply insults this board even more than it insults B&Z.
But speaking of liars and buffoons, look on the bright side: That means that BushCo didn't need to plant magical silent explosives all the way down the building. They only needed those magical suck-bombs that bent the floors and buckled perimeter columns inward, over a period of 20 minutes, to initiate the collapse. And since magical suck-bombs would presumably be silent, that explains why we don't hear anything resembling a controlled demolition in any WTC videos. Mystery solved.
wildbilln864
(13,382 posts)there are no previous examples of any building ever in history that collapsed completely to the ground just because one part of it may have collapsed be it a floor or what ever. But you keep on carrying that H2O man.
William Seger
(11,047 posts)... it's much more effective if you can then say something sensible. "Things can't happen if they haven't happened before" doesn't qualify, even without considering that your premise is false:
> there are no previous examples of any building ever in history that collapsed completely to the ground just because one part of it may have collapsed be it a floor or what ever.
Skyline Towers, 1973.
GGJohn
(9,951 posts)But you know the old saying, there are none so blind as those that won't see.
wildbilln864
(13,382 posts)see post 46!
GGJohn
(9,951 posts)You've convinced me with this post.
wildbilln864
(13,382 posts)This proves colllapse was not "inevitable"!
William Seger
(11,047 posts)In a post above I said, "To a physicist, the question of whether an impacting object would destroy the impacted object is not answered by silly and invalid analogies. It's just a question of how much energy was involved in the impact and how much would be necessary to do the destruction." Obviously, this demolition failed because of bad estimates (if any were actually made) of how much energy it would take for the falling block to destroy itself, versus how much was available.
You seem to be very determined to not understand this.
wildbilln864
(13,382 posts)If the whole building would collapse completely from removing just one floor then they wouldn't need to rig the whole building.
AZCat
(8,345 posts)I've been away from good internet connections so I've avoided watching the video until now, which is why I was unaware he references Anders Bjorkman's heiwaco website. That just further confirms the author of the video is as unskilled in engineering and physics as I had thought.
RoccoR5955
(12,471 posts)zappaman
(20,617 posts)wildbilln864
(13,382 posts)wildbilln864
(13,382 posts)the debris encountered increasingly larger and larger structural members that were undamaged below the impacts.