aka
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Definitely this one:Do you have any other models that should be included in the list?
Definitely this one:Do you have any other models that should be included in the list?
Definitely this one:
It's a total, progressive, axially symmetrical top-down collapse of a slender tower without explosives, so in a sense, it is a token of intellectual honesty often forwarded by some members of the "9/11 truther community".Why that one? I know you've mentioned it before, but what exactly about it is relevant to the WTC collapses?
The idea for this thread is to just get a comprehensive overview of the state of thinking of the 9/11 truther community - and to a lesser extent the skeptic/debunker communities.
The domino tower experiment defuses the somewhat common misconception that 9/11 skeptics claim it is outright impossible to achieve such a total progressive collapse without explosives. It does however demonstrate that, if not explosives, certain other, additional, assumptions must be made about the structure to allow for its self-disassembly.I'm mostly interested in the models that demonstrate progressive collapse (and/or arrest)
The domino tower experiment defuses the somewhat common misconception that 9/11 skeptics claim it is outright impossible to achieve such a total progressive collapse without explosives.
It does however demonstrate that, if not explosives, certain other, additional, assumptions must be made about the structure to allow for its self-disassembly.
The debate consists of two diametrically opposed views:It seems like an attempt to dismiss models that do fall down as "domino towers".
By falling, by and large, just as the Twins fell.How does it?
That the Twins were extremely metastable systems which had the energy needed to overcome the force that held them up already built in - in one form or another - and required only very little energy input to powerfully release all their potential energy.And what are these assumptions?
2.) the Twins' fall was entirely natural, expected and inevitable
It's radically different though. No connections at all, just toppling. It models non of the aspects of the towers beyond being tall and composed of parts. It's like comparing an actual row to dominos toppling to cars being rear-ended in a domino effect.By falling, by and large, just as the Twins fell.
That the Twins were extremely metastable systems which had the energy needed to overcome the force that held them up already built in - in one form or another - and required only very little energy input to powerfully release all their potential energy.
To the extent that planes have become quite "natural" ever since the Wright Brothers' first takeoff, and to the extent that building fires have been quite "natural" ever since humans have decided to engineer their dwellings outside of caves, it is, for all intents and purposes, quite "natural" to expect a plane crashing into a building every now and then and a fire to ensue in the process.What's natural about a plane crashing into it, then fires raging for an hour?
It was intended as a summary of the argument presented by supporters of the official explanation and/or opponents of alternative explanations. Close study of the threads "Use of scale modeling", "Deny the inevitability" and "Rate of Crush" - or the official literature, for that matter - will surely reveal that this is the gist of the message, not a misrepresentation, nor an invalid paraphrasing of the viewpoint taken by "debunkers". Once initiated, there was no way the lower part could have arrested the progression of collapse - "there is no way to deny the inevitability". There is, as far as I can see, not much room for interpretation errors in this matter, which does not mean I am not open to correction.Some loaded words there. Perhaps you could define them in this context?2.) the Twins' fall was entirely natural, expected and inevitable
The point is that the domino tower falls like the Twins. Whether or not the Twins were built and engineered like a domino tower is a different matter. If those who deny the presence of steel-eating termites and space alien laser beams also dismiss a domino/Rube Goldberg machine/house of cards/any other form of chain reaction mechanism and dismiss Bazantian crushing scenarios -- what else can possibly explain that and how the Towers fell in a reasonable manner? I have only one last analogy left, and that is Genady Cherepanovs Dutch Tear hypothesis - but that would be worth its own thread, if anyone is interested.It's radically different though. No connections at all, just toppling. It models non of the aspects of the towers beyond being tall and composed of parts.By falling, by and large, just as the Twins fell.
We are, however, not operating in an information vacuum, we are making a comparison. The 500mph plane crash and the ensuing kerosene deflagration triggering one hour of office fires are "very little energy" compared to the powerful energy conversion they - as some claim, they alone - caused: all potential energy was converted into kinetic energy and deformation.Again some leaded words. "Very little energy" applies to a slight nudge of a domino. It does not apply to a 500mph plane crash, massive explosion, and an hour of large fire.That the Twins were extremely metastable systems which had the energy needed to overcome the force that held them up already built in - in one form or another - and required only very little energy input to powerfully release all their potential energy.
This kerosene deflagration indeed looks like only very little of the chemical energy was available to cause much damage to the steel structure of the building, other than blowing out the window panes on three (!) sides of a few floors, ripping off a few aluminium panels and leaving a few scorch marks - and getting the office fires started. But if I understood correctly, this thread is about the collapse progression - I will gladly share some salient features of the fireball in a different discussion.Does this look like "very little energy"?
That is the point made by those who claim that explosives (or other forms of additional energy that do not traditionally belong into an office building) were needed to bring down the Twins the way they came down, yes.The towers were not made of dominos. They were made of steel, welded and bolted.
The collapse is - in proportion - a little on the slow side, I confess, but other than that, I have yet to find anything remotely resembling the Twin Tower collapses as much as the domino tower collapses do in terms of axial symmetry, lateral distribution, smoothness of progression and completeness.Their collapse is nothing like your domino tower.
The point is that the domino tower falls like the Twins. Whether or not the Twins were built and engineered like a domino tower is a different matter. If those who deny the presence of steel-eating termites and space alien laser beams also dismiss a domino/Rube Goldberg machine/house of cards/any other form of chain reaction mechanism and dismiss Bazantian crushing scenarios -- what else can possibly explain that and how the Towers fell in a reasonable manner?
(Note, by the way, that it does not suffice to build a tower from dominos to ensure progression of collapse. They must be arranged intelligently, meticulously and purposefully to achieve that aim. The approach to building a stable tower is a completely different one, even with dominos, and arrest of a top-down collapse could easily be achieved, even without welds and bolts - solely through the friction between the dominos).
I am indeed reminded of the old results by the the911forum guys (achimspok? femr2? reported by Major_Tom) who claimed, IIRC, that the WTC collapse front reached a terminal velocity (not acceleration) - something which I have aways doubted, as my own spreadheet sims of a CoM-driven pancaking of floors tends to converge on a final acceleration.
Is there any analog, a similar physical phenomenon, is there anything this process, this sequence of action of an object upon itself can be compared with?Simple: Each floor slab could not support a large mass falling on it, so the floor slabs were rapidly stripped away, the outer walls fell away, and the core followed.The point is that the domino tower falls like the Twins. Whether or not the Twins were built and engineered like a domino tower is a different matter. If those who deny the presence of steel-eating termites and space alien laser beams also dismiss a domino/Rube Goldberg machine/house of cards/any other form of chain reaction mechanism and dismiss Bazantian crushing scenarios -- what else can possibly explain that and how the Towers fell in a reasonable manner?
I have offered, as working analogue physical processes and phenomena, so far:The fact that this is utterly unlike the domino tower means the domino tower is simply a poor visual analog.
That is indeed a hypothesis that has been in circulation for a while.This seems like you are suggesting that since the domino towers were designed to fall like this, then progressive collapse would have to have been deliberately built into the WTC towers?
...which is a beautiful way to explain the concept of metastability.I think you are conflating "a stable tower" with "a tower in which progressive collapse is arrested". These are two different things. The WTC towers were very stable, able to withstand hurricanes, bombs, and planes flying into them. They also did not arrest progressive collapse.
I largely agree, but please clarify: does setting up the tower deliberately in a very special and completely counterintuitive way (from the viewpoint of building a stable tower) to ensure its collapse not qualify as "messing" with the standing structure on every level all the way?The domino tower is enough to refute a couple or so of the most fundamental errors made by a number of CD truthers.
You probably recognize the class of "Newton's law" arguments, populated e.g. by David Chandler, that roughly go like this:
The premises of these arguments are all true[ETA: See footnote] for the domino tower, but the experimental result refutes the conclusion.
- On each level, the structure could bear the full load above, plus some nice margin of error / factor of safety.
- As the collapse progresses, the standing part would alway exert the full force of m*g upwards against the falling mass, of not messed with.
- Since that falling mass accelerates at 0 < a < g, the lower part actually only exerts an upward force of 0 < m*(1-a) < m*g
- Therefore, the standing structure must have been messed with - on every level all the way to the ground, or else the collapse would have arrested
Measurement would be futile with all the fine granularity involved, but merely from eyeballing I would agree and even say that is another good reason to find that actually, the domino tower seems to mimick the real thing quite well - it also reaches a "terminal velocity" (if the uppermost "fountain" is counted - I think Chandler shows in Acceleration and Serendipity that the ejecta from the windows continue at the initial roofline acceleration or so).Different mechanism, different results. Bazant's methodology converges on g/3 (that's you, too, right?), Seffen on g/2, and reality 0. Or so it seems.[...] that the WTC collapse front reached a terminal velocity [...]
This is the analogue I offered at physorg in 2008. It was not well-received; ignored at best. There's little effective difference between no connections and trivial ones.I have offered, as working analogue physical processes and phenomena, so far:
- A house of cards.
Is there any analog, a similar physical phenomenon, is there anything this process, this sequence of action of an object upon itself can be compared with?
akaREYON?PS: Hi OWE
The one, at your service!aka?
There should be a discernible difference between a building being in the way all the way and a building getting out of its way to get out of its way...?There's little effective difference between no connections and trivial ones.
1. A demolition methodVerinage demolition
None getting anywhere near the similarity the domino tower has with the Twins' collapse pattern.Some of the instances of progressive collapse here: https://en.wikipedia.org/wiki/Progressive_collapse#Initiating_factors_behind_notable_examples
A bookshelf held together with magnets so wobbly and delicate it can rise to 18 floors at most and only if nobody sneezes (no offense, really not - you know I think it's great, the first of its kind, unique, the magnets were a brilliant idea and you have all my respect for all the work, time and money you put into it, and I'm not dissing you at all with this - but in comparison with the domino tower, as far as visual similarity with the Twins goes, it really still needs a lot of work and fine-tuning).My model
Just for clarity, verinage is not a method that would work on steel frames.
Greetings!The one, at your service!
Maybe. I'm still trying to get my head around the statement.There should be a discernible difference between a building being in the way all the way and a building getting out of its way to get out of its way...?
Hi OWE - this series of related discussions more your area of interest than mine for reasons which should be obvious to you.Different mechanism, different results. Bazant's methodology converges on g/3 (that's you, too, right?), Seffen on g/2, and reality 0. Or so it seems. There's velocity dependence involved.
I agree there, yes. Verinage (a form of controlled demolition) is much more comparable to the WTC collapses than the "natural" collapse of a tower of dominoes.The point here is that it's vastly more comparable to the WTC collapses than a tower of dominoes. It's better scale-wise, and construction-wise.
Yes. femr2, achimspok and I all measured and got roughly the same result. Of course, measuring the leading front is not the same as an aggregate metric, but for an extrema it suffices. And, if you extrapolate the constant velocity from the region measured to ground level, it's within an acceptable band of collapse time.Save me scouring the sources - isn't the BIG difference that femr et al measured the real event and others did theory calculations?
Emphasis mine - that is the key here, you know how to name things. I would say it "liquefies", except that the top would buoy in a liquid that is denser. So it either must turn into a gaseous state or densify first (also according to Newton's impact depth formula).It is the propagation of a defect. I'm not sure that treating it like a building is proper, once the phase transition starts.
Exactly!It's something else entirely.
I disagree! I was incorrect when I thought vérinages start in the middle - in fact, the patent says the top 1/3 would be enough - and that they expect something remaining upright and needing an excavator. And as Chandler shows, the roofline and collapse front decelerate - whereas the real towers' collapse front - and the dominos - hit terminal velocity and keep it up until the bitter end.I agree there, yes. Verinage (a form of controlled demolition) is much more comparable to the WTC collapses than the "natural" collapse of a tower of dominoes.
Are there any regulations or benchmarks on how fast a building is allowed to disassemble itself before it becomes "unacceptable"?it's within an acceptable band of collapse time.
Haha! I just meant that if one adds the time the measurements started to the extrapolated time to reach ground, the figure is close to generally accepted values for the collapse time. I mention this because it might seem that a terminal velocity would lead to a collapse time longer than observed.Are there any regulations or benchmarks on how fast a building is allowed to disassemble itself before it becomes "unacceptable"?
I agreed with Mick on the basis of verinage being a form of controlled demolition.I disagree! I was incorrect when I thought vérinages start in the middle - in fact, the patent says the top 1/3 would be enough - and that they expect something remaining upright and needing an excavator. And as Chandler shows, the roofline and collapse front decelerate - whereas the real towers' collapse front - and the dominos - hit terminal velocity and keep it up until the bitter end.
Thanks - my "Old Farts" memory vindicated.Yes. femr2, achimspok and I all measured and got roughly the same result. Of course, measuring the leading front is not the same as an aggregate metric, but for an extrema it suffices. And, if you extrapolate the constant velocity from the region measured to ground level, it's within an acceptable band of collapse time.
Understood of course. BUT - As always - my problems arise when the relationships are not "connected' - not defined and there are lots of loose hanging inferences that the theory somehow is relevant to whatever. Mostly my focus on the real WTC events but same goes for anyone's abstract model - if the logic is loose or none existent discussion can wander all over the planet.So that's reality compared to theory, correct. However theory need not be so disconnected from reality.
I think you mean WHAT the theory says - not WHO wrote it - i.e. how well the theory ties to either reality or the model.Depends on whose theory it is.
Yes, although the exception is that if I say it, it's better.I think you mean WHAT the theory says - not WHO wrote it - i.e. how well the theory ties to either reality or the model.
Modesty inhibits several responses.Yes, although the exception is that if I say it, it's better.
Except for the "deliberately" part, I agree with this sentence fragment....progressive collapse would have to have been deliberately built into the WTC towers...
Agreed. The vulnerability to progression arose from the OOS Tube in Tube design. A deliberate feature of design. But not intended to ensure progressive collapse. The building design intended that it not reach progression within the design parameters. But under the massive trauma - way outside design parameters - progression and progression to global collapse were both inevitable. Easily demonstrated/explained/proved by direct access to the physics of the real event. Hence my concerns that models can demonstrate what happens but the quantitative physics is easily applied directly to the real event.Except for the "deliberately" part, I agree with this sentence fragment.
I am not aware of when, where and through what mechanism Bazant arrived at g/3, but that's what I got: By modelling pure momentum transfer of floors pancaking inelastically. No strength, force or energy of anything considered (connections can be thought of as holding the floors just barely, but requiring practically zero force/energy to disconnect once tapped on ever so lightly). That seems as far away from anything Bazant has modeled in his WTC papers as I can think of. Or I missed that part (quite likely, given that I never truly studied any of them after B&Z )Different mechanism, different results. Bazant's methodology converges on g/3 (that's you, too, right?), Seffen on g/2, and reality 0. Or so it seems. There's velocity dependence involved.
The reason you get the same result is that the discrete algebraic solution in the limit of infinite stories / infinitesimal story height reduces to the continuum solution of Bazant. Plus the fact that realistic structural dissipation functions do not contribute to the acceleration limit, just prolong getting there as the structural resistance increases. Your model is the Greening model, and is exceedingly useful for exploration of the solution space, as it's a great deal more flexible than the analytic approach (which ends up having to be solved numerically anyway).I am not aware of when, where and through what mechanism Bazant arrived at g/3, but that's what I got: By modelling pure momentum transfer of floors pancaking inelastically.
...
That seems as far away from anything Bazant has modeled in his WTC papers as I can think of.
The key is there has to be a natural dynamic equilibrium, which means drawing in velocity as a term somehow. As velocity increases, resistive force increases. Mass shedding (as you note below) is a parameter which can drastically alter the characteristics of the dynamics, and it is physically reasonable to suppose a velocity dependence of some sort.I am of course aware that my model is missing a great deal of reality - mostly the columns, but also elastic components, mass shedding, etc. I would not be surprised in the slightest if someone added one or several of these factors to my model and came up with a terminal acceleration of 0.
Excellent point. Clearly the mechanism is entirely different than the tower collapses, which might lead to premature dismissal of the instructive value it offers.I think in the domino tower, the main reason why collapse doesn't accelerate on average is that all the descending mass is shed as fast as it acrues.
Both do demonstrate, as Oystein pointed out above, the fallacy of the supposed violation of Newtonian physics.Is there any analog, a similar physical phenomenon, is there anything this process, this sequence of action of an object upon itself can be compared with?
I have offered, as working analogue physical processes and phenomena, so far:
- A house of cards
- A domino tower
Demonstrate propagation of compressive forces. Since there is no evidence of shattered columns I don'the see how this relates to the TTs except perhaps how the seismic record shows the entire collapse.- A Dutch Tear
- A slinky dropped from the roof
By definition it can be anything arrangement you wish. OK it's a propagation of energies.- A Rube-Goldberg machine
Now that's reaching. Is this supposed to bolster a Judy Wood argument?- The sped-up footage of a burning candle
Never intended as an analogue to collapse but as a demonstration of a single aspect, dynamic forces...and it is with some conviction that I say they beat:
- A hammer dropped on a glass table
- A barbell dropped on a soda can
Same as previous with added emotional aspect.- A bowling ball dropped on the head of a truther
Yes,,,, IF the tower is tall enough.The key is there has to be a natural dynamic equilibrium, which means drawing in velocity as a term somehow. As velocity increases, resistive force increases. Mass shedding (as you note below) is a parameter which can drastically alter the characteristics of the dynamics, and it is physically reasonable to suppose a velocity dependence of some sort.
Indeed. The Tacoma Narrows Bridge was not deliberately designed for failure either but it's design led to its failure.Except for the "deliberately" part, I agree with this sentence fragment.
Here is how I understand "Mechanics of Progressive Collapse" and I hope OWE will be so kind to correct me where I'm wrong.I am not aware of when, where and through what mechanism Bazant arrived at g/3
That's a nice strawman you're building there, it would be a shame if somebody came to knock it over!Both do demonstrate, as Oyster pointed out above, the fallacy of the supposed violation of Newton an physics.
Explaining the WTC collapse with the Tacoma Narrows Bridge is like explaining zero point energy with a steam engine. When Galloping Gertie fell, she fell like other suspension bridges fell. The Twins fell unlike anything ever.The Tacoma Narrows Bridge was not deliberately designed for failure either but it's design led to its failure.
The strawman is simply a result of misapplication of physics by others. I guess you also missed it when Oystein ( I now note my new tablet'so annoying autocorrect) said the same thing.That's a nice strawman you're building there, it would be a shame if somebody came to knock it over!
Explaining the WTC collapse with the Tacoma Narrows Bridge is like explaining zero point energy with a steam engine. When Galloping Gertie fell, she fell like other suspension bridges fell. The Twins fell unlike anything ever.
Pet peeve:
Deceleration is NOT imho, a reduction in acceleration, but rather a change in the sign of acceleration.
To use it for both situations just makes the term horribly ambiguous.
And since the area under F(u), let us call it E[elasticplasticpot], is smaller than E[gravpot], this is in essence a mathematical way of saying "for every meter height, there is on average less Newtons upwards force in the way than necessary to decelerate the kilograms of the tower against the gravity of the planet."
I understand. And I refute it by pointing out, by means of the domino tower model, that there is a measurable, energetic difference between "shit happening" and "a plan coming together", between failure due to stupidity and neglect and a perfect chain reaction, between dumb accident and blatant purpose, between ordo ab chao and intelligent design. .I am not "explaining" the WTC collapses with the TNB collapse. I am pointing out that a design peculiarity that allows for collapse need not be a deliberate feature the engineer built in.
So far so good. (How do you do subscript?)The forces are in equilibrium, that's all. The acceleration is zero because the net forces are zero. Remember that F=ma refers to the NET force, and is more correctly written F[net]=ma