How do you mean this is not up to interpretation? If you say it is not up to interpretation you are saying it is meaningless and irrelevant. In an "evidence-based discussion" you are prohibited from making such claims.
Really? Then what's your interpretation?
I really do think that you guys need to take a little time out of seeing whatever it is that you obviously think each other is obviously seeing and expressing precisely IN WORDS such that the average idiot on the street can understand, when sober, not only what it is that you are seeing, but also what you think the conclusions are that you think can be justifiably drawn from it.
I see a big sheet being pushed out by the upper block which is tipping and has slipped behind it. You see something else?
I for one would be happy to see a modelling of the suggested behavior in such a program. However one has to be wary: This starts with granules, when what we are more interested in is "rubble".
True, but don't worry too much about terminology. These same methods are used in soil mechanics where the grain sizes range from sand and silt to large boulders.
In rubble the granule sizes are stochastically distributed, but what is even worse is that in our rubble it needs to start off as coherent solid bodies that are broken up first and then behaves as a rubilized flow.
Yes, that's tougher, having fracture create the distribution instead of assignment. Probably a long ways off.
That is the essence of the problem in this case, so such granular flow models can only ever be a starting point, only a device to aid the visualization of these sorts of processes.
Darkwing wrote:These models are always, by necessity, founded on pure reason. They cannot be substituted for empiricism.
Agreed, the models cannot be substituted for all empiricism, but the empiricism which takes precedence is observation of the actual system being described and to the extent possible similar systems. Wildy undirected empiricism can be useless or worse misleading. Not every physical experiment has valid analogy just because its maker claims it.
Case in point, psikeyhackr's physical model. From the beginning, I've explained what must surely be the reason for his arrest result and have recently load tested paper loops made to his specification to prove that I was right all along.
That's empiricism, though it was entirely unnecessary since the theory already handled it quite nicely. The purpose of doing the physical test was simply to demonstrate the validity and power of the theory in a way (the only way) psikeyhackr believes in: physical experiment.
Needless to say, it had exactly zero impact on him. He retreated to his mantras and pretended it never happened, which is exactly what he would do if confronted with a physical model of progressive collapse. This sort of dodgy ideological crap is a waste of time for any serious researcher. It is because of these ongoing experiences with people who can't tell when a virtual model is preferred to a physical model that I can only spend so much time in the future explaining it.
A real bag of marbles is preferred for bag-of-marbles systems. A framework which can simulate a bag of marbles and thousands of tons of random-size spheres equally well is preferred to a bag of marbles for general modeling.
One thing that seems to be overlooked by people not familiar with analytical and computational modeling is that these are based on hundreds of years of empiricism! They do not come out of thin air. It's not necessary to start from scratch and reinvent every wheel along the way. Ignorance of the empirical foundation of these methodologies does not constitute valid criticism. Caution is advised, of course, but verification of principles already verified by others is a waste of time.
I see a big sheet being pushed out by the upper block which is tipping and has slipped behind it. You see something else?
That is happening way to slowly for this to be the cause.
Remember that the ROOSD driver is by this time well below this event.
The only way that this analysis could make any sense is if the upper block which had been rubilized has once again coalesced into a semi-solid object. I'm sorry if I find that hard to believe.
The much simpler explanation is that the ROOSD driver severed the connection between the floors and the perimeter, leaving the perimeter to take it's merry old time to fall.
Maybe there is an itsey bitsey push from residual material, but it can't be much more significant than making the difference between falling inward and outward.
Either way, the fact that the ROOSD driver (and the most violent expulsion) is no longer connected to this event means that the only thing this allows us to conclude is that there was far less mass available to the ROOSD driver than almost all models assume.
This video tells the story:
Particularly telling is the piece of perimeter right at the closest corner top through the first half of the video.
You can clearly see three phases of debris flow: 1) The leading, already falling material which is slightly ahead of the main phase. 2) The main phase progressing down the building side presumably producing most of the rubble. 3) The trailing phase of perimeter elements.
If it was the ROOSD driver pushing the the perimeter off it should have sheared immediately and hence kept pace with the main phase.
Two further observations:
A) Even the most generous reading indicates that the percentage of mass available to the ROOSD driver is a very tiny proportion of the total indeed. B) It appears that this may be a two phase event with the phase change happening at top of the pointy building to the right of that video.
This last observation sounds a lot like what SanderO was saying, except that the phase change occurs well after the initiation has occurred and the building has been torn apart by the ROOSD driver internally.
the empiricism which takes precedence is observation of the actual system being described
That is not empiricism.
Past events have no physical reality anymore.
Empiricism relies on making falsifiable predictions of FUTURE physical events on the basis of a pre-established model.
You can use the videos of the building to construct your analytical model, but you cannot validate that model by it. That is simply because of post hoc ergo propter hoc, affirming the consequent, is-ought and a slew of other logical reasons to preclude that chain of reasoning from ever being valid.
They do not come out of thin air.
The equation, yes surely. But not the model you use for connecting the equations together in the form of an explanation of any one particular event.
Engineering is a discipline which works precisely by selectively constraining the conditions so that the equations derived through empiricism can be applied.
But in our problem there is no such constraint. There is no physical physical reason why moonbeams and mini-fart bombs could not have produced the destruction as observed. We exclude them because if fart bombs DID cause the collapse then everyone would have smelt it. Okay that is a crude analogy to detecting radiation after a "mini-nuke", but the point is that we exclude causes because their expected effects do NOT occur.
But we cannot logically INCLUDE causes because there expected effects occurred.
In engineering you can say: I take local conditions ABC with foundation MNO put it with building blocks QRS in XYZ configuration, therefore (the empirically derived equations tell us) I will get building EFG.
But doing the reverse is a logical fallacy.
Put another way: Every time you design and build a building you are attempting to falsify the physical models from which the engineering equations were derived. You are doing the second half of empiricism. The fact that buildings based on these models generally don't fail is taken as support for the correctness of those principles.
In this case however there is no model, we are deriving the initial conditions from observation and positing a model to explain it. That model cannot be validated by reference to existing models precisely because there is no existing model that explains these conditions.
I suspect the perimeter "peeling" does not occur immediately as the front passes it. I would think the facade hang together as panel assemblies until sufficient lateral forces present which then causes it to break free... sort of like the sand poured inside a carton will bust out the bottom first leaving the top connected. In this case the bust out pushes the panels which appear to standing as walls and not rigid corners in most cases.
It seems that whatever the lateral forces as play are ... they would be greater pushing out aside from wind pressure. The collapsing floor IS forcing the air out ahead of it and so this is providing the energy to eject debris and bash against the inside of the facade.
The collapsing floor IS forcing the air out ahead of it and so this is providing the energy to eject debris and bash against the inside of the facade.
That is fine, but if the collapsing floor is now well below the falling facade what is making the floor collapse if the main body of mass is still up there knocking the facade off?
Darkwing wrote:That is happening way to slowly for this to be the cause.
No, it's not. Back that very same video up a few seconds and you'll see the upper block slipping behind that sheet with your own two eyes. Like I say, not subject to interpretation at all, but you do have to look to see.
Remember that the ROOSD driver is by this time well below this event.
Yes, and OOS collapse is not the driver here, the upper block is.
The only way that this analysis could make any sense is if the upper block which had been rubilized has once again coalesced into a semi-solid object. I'm sorry if I find that hard to believe.
You might find it easier to believe if you skip your assumed but non-existent prior rubblization. The upper block is the south tower is getting trashed as that gif plays, not before.
The much simpler explanation is that the ROOSD driver severed the connection between the floors and the perimeter, leaving the perimeter to take it's merry old time to fall.
It may be the simpler explanation, but it's wrong. Watch the videos.
Darkwing wrote:Past events have no physical reality anymore.
Oh, for God's sakes. Neither do future events have physical reality yet, and the present is infinitesimal. So what?
You can use the videos of the building to construct your analytical model, but you cannot validate that model by it.
Some things don't need a model. Somethings you can simply see if you look, and I'm going to have insist that you do look, if you must continue to talk about it.
No theory, no model, just observation. Just like I don't need a "model' to figure out who stopped when at a four-way stop. Really, JUST LIKE IT. Exactly like it. If you insisted I couldn't possibly know whose turn it is to go at a four-way without resorting to Popper, Kant and Latin, I'd push you out of the car and just go when my turn came.
The equation, yes surely. But not the model you use for connecting the equations together in the form of an explanation of any one particular event.
Engineering is a discipline which works precisely by selectively constraining the conditions so that the equations derived through empiricism can be applied.
Yeah, read this to get a good idea of how this is done sans stumbling in the dark.
few seconds and you'll see the upper block slipping behind that sheet with your own two eyes.
But by that time the actual damage is way below what the upper block is doing. If the upper block is not doing the damage then it is not relevant and should be ignored.
Some things don't need a model.
Everything needs a model.
Not stating your model is simply implying an unstated model.
If you insisted I couldn't possibly know whose turn it is to go at a four-way without resorting to Popper, Kant and Latin, I'd push you out of the car and just go when my turn came.
That is a social model not a physical model. And no, there is no way of knowing who should go first in a four-way without knowing the social model (or guessing it) beforehand.
Yeah, read this to get a good idea of how this is done sans stumbling in the dark.
Fine and well except that we ARE stumbling in the dark. No use pretending otherwise for the sake of simplicity.
The collapsing floor IS forcing the air out ahead of it and so this is providing the energy to eject debris and bash against the inside of the facade.
There is another, far more devastating problem with this:
If the air is pushing the debris out what is turning solid reinforced concrete slabs into debris in the first place. It is clearly dust, not office material coming out the windows.
OWE's debris model relies on the debris already being disjointed and sitting on a solid surface being pushed aside by further debris.
But that can't be the case here because events are happening way to fast. When you see the debris coming (using OWE's model) what must have already occurred was for a significant amount of debris to have collected on the floor to be pushed aside and that THAT debris cannot be enough to break the floor.
But if that debris was not enough to break the floor it was not enough to break the previous floor, so how did it get there to be pushed aside by the thing that IS breaking the floor.
That means that the highest level where we can see debris coming out of the windows is ALREADY several stories ABOVE where the actual action is happening.
Now we are talking about ROOSD happening virtually at the speed of the outside free-falling material.
Oh, for God's sakes. Neither do future events have physical reality yet, and the present is infinitesimal. So what?
I apologize for quoting from wikiedia here:
"Empirical is used in conjunction with both the natural and social sciences, and refers to the use of working hypotheses that are testable using observation or experiment. In this sense of the word, scientific statements are subject to and derived from our experiences or observations. In a second sense "empirical" in science and statistics may be synonymous with "experimental". In this sense, an empirical result is an experimental observation. The term semi-empirical is sometimes used to describe theoretical methods that make use of basic axioms, established scientific laws, and previous experimental results in order to engage in reasoned model building and theoretical inquiry."[my boldface]
Notice the distinction between "testable" and "derived form". These two things are not interchangeable.
You derive from the past to predict the future. You cannot predict the past.
Also notice the central role that model building (meaning conceptual model building) plays in even the semi-empirical mode?
The basic idea behind empiricism is that knowledge can be derived through careful observation and cataloging of phenomena and extrapolating laws or principles from these observations
The reason Van Fraassen (1980, p. 81) uses the distinction between observable and unobservable entities to formulate his brand of empiricism, and not the distinction between observational and theoretical statements, is his conviction that every term in our language is theory-laden; he thinks this entails that there are no observation statements. Van Fraassen does not explain what he means by “theory-laden,” perhaps because this position is so familiar from the work of Kuhn (1962) and others. The thought may simply be that each term in our language requires knowledge if we are to apply it. We can’t tell whether the term “apple” applies to something by just looking at it; we need to have beliefs about what an apple is. If these beliefs comprise a “theory of apples,” then Van Fraassen’s claim that all empirical statements are “theoretical” is correct. If all statements are theory-laden in this sense, how can there be observation statements? The answer is to relativize the notion of an observation statement to a testing problem. The difference this makes can be understood by considering the following two claims, which differ in terms of the order of the quantifiers used: (EA) There exists a set of observation statements that presuppose no theories whatever, and these can be used to evaluate any theories we wish to consider. (AE) For any set of competing theories, there exist a set of observation statements that presuppose none of the theories under test, and these can be used to evaluate those theories. The statement (EA) characterizes absolute theory neutrality, while (AE) defines relative theory neutrality. The claim that all statements are theory-laden impugns (EA), but leaves (AE) untouched. (AE) expresses the important point that observation statements need to be epistemically independent of the hypotheses they are used to test (Sober 1990a, 1993).
Darkwing wrote:But by that time the actual damage is way below what the upper block is doing.
There is actual damage propagating below this but the perimeter sheet is different damage and it's caused by being pushed out by the upper block.
If the upper block is not doing the damage then it is not relevant and should be ignored.
The upper block is the cause of this particular damage therefore cannot be ignored.
Everything needs a model.
I knew you'd say that. This doesn't need a model, the four way stop doesn't need a model (pushing you out of car now).
Not stating your model is simply implying an unstated model.
Yes, and what an excellent way to go anytime the model is self-evident. You know, there is such a thing as too abstract, to the point where nothing at all gets done.
That is a social model not a physical model.
One car physically arrives at the stop first. Then another and another. The social part is: one who stops first goes first, or if two stop at the same physical instant the one physically located to the right (USA) goes first. I'm only talking about the physical part and that should be PAINFULLY OBVIOUS at this point. I don't need a frikking model to tell me which car stopped first!!!! Just my eyes.
Neither do I need a frikking model to tell me the upper block is behind that sheet pushing!!!! Just my eyes.
And no, there is no way of knowing who should go first in a four-way without knowing the social model (or guessing it) beforehand.
Correct. Just as there is no way of knowing who should go first without the physical fact of who stopped first; the social convention is insufficient. If you don't look you won't know. If you do, you will.
Fine and well except that we ARE stumbling in the dark. No use pretending otherwise for the sake of simplicity.
Doing computational experiments is not stumbling in the dark, it's stabbing in the dark. Difference being the experiment is highly directed and exact; its application a vague art left to the reader at their own risk.
OWE's debris model relies on the debris already being disjointed and sitting on a solid surface being pushed aside by further debris.
