Merged Applicability of Bazant's model to the real world

[Major_Tom]

Later in BL:

5. Why Can Crush-Up Not Begin Later? The discusser fur-
ther states that “it is difficult to imagine, again from a basic
physical standpoint, how the possibility of the occurrence of
crush-up would diminish as the collapse progressed.”

Yet the discusser could have imagined it easily, even without calcu-
lations, if he considered the free-body equilibrium diagram
of compacted layer B, as in Fig. 2͑f͒ of the paper.


Here, James Gourley actually says something useful, his only such comment in the paper that I could see. He was confused why crush up cannot occur during crush down.

It is difficult to imagine, no? Here is figure 2:

Blocks.


Guys, they are talking about WTC1. I don't think you realize that this is Bazant's collapse progression model. He claims to prove in all three papers, BV, BL and BLGB that crush up cannot happen before crush down is complete.


This is pure fantasy land.

Here I have to inform you what your theory is because you don't even know.

 

[femr2]

I didn't say from the top of *WTC1*. I said from the top of *a building*.

So ? Makes no odds. Your error is the silly assertion that you'll get a decent approximation to the speed of the fall of an apple falling from the roof of a building without including air resistance.

Please show your working.

You're doubting the value for what reason ? Bizarre.

Here y'are...


Interractive calc here...
http://hyperphysics.phy-astr.gsu.edu/hbase/mechanics/fallq.html#c1

End of.

 

[pgimeno]

Later in BL:

5. Why Can Crush-Up Not Begin Later? The discusser fur-
ther states that “it is difficult to imagine, again from a basic physical standpoint, how the possibility of the occurrence of
crush-up would diminish as the collapse progressed.”

Yet the discusser could have imagined it easily, even without calcu-
lations, if he considered the free-body equilibrium diagram
of compacted layer B, as in Fig. 2͑f͒ of the paper.


Here, James Gourley actually says something useful, his only such comment in the paper that I could see. He was confused why crush up cannot occur during crush down.

It is difficult to imagine, no? Here is figure 2:

[qimg]http://www.sharpprintinginc.com/911/images/photoalbum/13/BV_fig2.png[/qimg]

Blocks.


Guys, they are talking about WTC1. I don't think you realize that this is Bazant's collapse progression model.

I think it's you who doesn't realize. In all the examples you bring, he's describing his model, not the actual collapses.

(Edited to highlight another sentence)

 

[Major_Tom]

Not an apple. It's WTC1., It's your theory even though you can't read it.

You don't even know what your own theory is.

Pgimeno, you are so, so wrong.

 

[Dave Rogers]

You're doubting the value for what reason ?

Because I like to check you've understood the problem, since you've showed some serious misunderstandings of basic physics in past discussion. All fine this time.

Dave

 

[Major_Tom]

I could show you these all day long...

Title of paper: (BLGB)What Did and Did not Cause Collapse of WTC Twin Towers in New York

BLGB is not about Bazant's model, it is about WTC1 and 2. He is applying his model to the towers quite literally throughout the whole paper.

Bazant's rendition of the collapse of the WTC towers:

The whole paper is about WTC1 and 2, just like BL.

Crush down, then crush up.


BLGB: "An accurate analysis of simultaneous (deterministic) crush-up and crush-down is reported in Ba?zant and Le (2008) and is reviewed in the Appendix, where the differential equations and the initial conditions for a two-way crush are formulated. It is found that, immediately after the first critical story collapses, crush fronts will propagate both downwards and upwards. However, the crush-up front will advance into the overlying story only by about 1% of its original height h and then stop. Consequently, the effect of the initial two-way crush is imperceptible and the hypothesis that the crush-down and crush-up cannot occur simultaneously is almost exact."

 

[pgimeno]

MT, I will believe you as soon as you show us where Bazant compares the crush direction predicted in his model side-by-side with the real event.

And I mean a true comparison, such as that done in BLGB p.902 (11 of the PDF), in figure 7. Not a description of how his model behaves when applied to the WTC1 parameters.

Until then, let me buy some popcorn to see you handwave, misrepresent, distort, and smear.

 

[femr2]

Because I like to check you've understood the problem

Wonderful. Let's hope that pgimeno takes heed eh

 

[femr2]

the effect of the initial two-way crush is imperceptible and the hypothesis that the crush-down and crush-up cannot occur simultaneously is almost exact."

In a paper discussing WTC 1 & 2, and the indication of almost exact match, funny stuff.

They don't want to hear, see, speak

 

[Major_Tom]

So the comments in BLGB, by Bazant, on WTC1 and 2, are insufficient for you?

You don't believe Bazant's own words?

It's a mental cocoon. That is what JREF is, a mental cocoon.

 

[pgimeno]

In a paper discussing WTC 1 & 2, and the indication of almost exact match, funny stuff.

Match? I don't see the word match. Care to point it to me, please?

 

[pgimeno]

So the comments in BLGB, by Bazant, on WTC1 and 2, are insufficient for you?

You don't believe Bazant's own words?

I do believe Bazant's words and I think they are an accurate description of his model.

Care to point out where he compares his prediction of the crush direction with the real crush direction?

 

[femr2]

Match? I don't see the word match. Care to point it to me, please?

ROFL.

Almost exact in comparison to WHAT exactly ? (...in a paper discussing WTC1 & 2 )

 

[pgimeno]

ROFL.

Almost exact in comparison to WHAT exactly ? (...in a paper discussing WTC1 & 2 )

In comparison to considering a downwards-only crush direction propagation in the model, of course.

Are you really this thick?

 

[femr2]

In comparison to considering a downwards-only crush direction propagation in the model, of course.

Oh, come on.

The paper is discussing WTC 1 & 2 using the model, and making the various mistakes previously highlighted in this thread about applicability.

The particularly stupid one way crush simplification is one of those. It's nonsense. It didn't happen in the real world.

The simplification is crap.

I really don't care if you want to defend the model.

One way crush is fiction.

MT has highlighted numerous instances in which the authors are applying the model incorrectly to reality.

Was there enough energy available for propogation to ground given the initial assumed simplified conditions...yes.

End of. Drawing further conclusions from the model is walking into grey area from that point on imo.

Any conclusion beyond that must account for the actual behaviour which the model WAS NEVER ORIGINALLY INTENDED to be able to match.

ANYONE doing so is walking a VERY fine line on misapplying it.

One way crush is nonsense. Didn't happen. Is wrong.

 

[pgimeno]

The paper is discussing WTC 1 & 2 using the model, and making the various mistakes previously highlighted in this thread about applicability.

The particularly stupid one way crush simplification is one of those. It's nonsense. It didn't happen in the real world.

What an absurd misrepresentation of the papers.

The model is a simplified one.

Crush direction is a consequence of the simplified model, not a simplification per se. [ETA: except where the model predicts a small two-way crush at the beginning but it's disregarded; that *is* a simplification]

And, as I have repeatedly stated, that doesn't prevent the model from being applied to the real world.

Your statement that there were "various mistakes previously highlighted in this thread about applicability" is totally wrong. There's no such mistake previously highlighted in this thread with respect to applicability.

Such a statement would have a form similar to this:

"The [magnitude A] predicted in the model can't be derived from it because the [related magnitude B] used in the model can't match reality can have a significantly different behavior in maybe X% of the cases, because ____________."
[Edited as indicated by the strike/underine]

And that's the whole point of this thread. Yet again, let me repeat it: even if the crush direction, which is a consequence of the model, does not accurately match the real behavior, that doesn't invalidate in itself neither the model nor its applicability. It's merely an example of a magnitude not accurately predicted by the model.

Drawing further conclusions from the model is walking into grey area from that point on imo.

Your opinion is noted. Care to defend it with more than handwaving?

 

[pgimeno]

I skipped this sentence:

MT has highlighted numerous instances in which the authors are applying the model incorrectly to reality.

No, he hasn't. He has highlighted numerous instances in which the authors are describing the behavior of the model.

 

[femr2]

And, as I have repeatedly stated, that doesn't prevent the model from being applied to the real world.

This is going round in circles. Let's try it t'other way around...

In what way(s), or for which specific observations, do you think the model CAN be applied to the real world...beyond the original scope and intention of determining that, given the simplifying assumptions, there is enough energy available for propogation ?

Your statement that there were "various mistakes previously highlighted in this thread about applicability" is totally wrong. There's no such mistake previously highlighted in this thread with respect to applicability.

Nonsense.

 

[pgimeno]

This is going round in circles. Let's try it t'other way around...

In what way(s), or for which specific observations, do you think the model CAN be applied to the real world...beyond the original scope and intention of determining that, given the simplifying assumptions, there is enough energy available for propogation ?

I don't know, that's the objective of the discussion. Do you have objections to these sections in BLGB?

"Comparisons of Calculated Motion with Video Record"

"Comparison of Collapse Duration with Seismic Record"

Do you have a statement in this line that poses a significant objection to the validity of these comparisons?

"The [magnitude A] predicted in the model can't be derived from it because the [related magnitude B] used in the model can have a significantly different behavior in maybe X% of the cases, because ____________."

Is there a statement similar to that one along the thread? Because if there isn't, you have no basis to claim this:

Your statement that there were "various mistakes previously highlighted in this thread about applicability" is totally wrong. There's no such mistake previously highlighted in this thread with respect to applicability.

Nonsense.

So, care to point it to me, to show me the "nonsense" in my words?

 

[W.D.Clinger]

the effect of the initial two-way crush is imperceptible and the hypothesis that the crush-down and crush-up cannot occur simultaneously is almost exact."

In a paper discussing WTC 1 & 2, and the indication of almost exact match, funny stuff.

They don't want to hear, see, speak

Following femr2's link, we find the context as quoted by Major_Tom:

BLGB: "An accurate analysis of simultaneous (deterministic) crush-up and crush-down is reported in Ba?zant and Le (2008) and is reviewed in the Appendix, where the differential equations and the initial conditions for a two-way crush are formulated. It is found that, immediately after the first critical story collapses, crush fronts will propagate both downwards and upwards. However, the crush-up front will advance into the overlying story only by about 1% of its original height h and then stop. Consequently, the effect of the initial two-way crush is imperceptible and the hypothesis that the crush-down and crush-up cannot occur simultaneously is almost exact."

From that context, it seems clear to me that the conclusions quoted by femr2 are consequences of the differential equations and initial conditions. Those differential equations and initial conditions are part of the model, not the event. If they were talking about the event, they'd have said "propagated" and "advanced" instead of "will propagate" and "will advance".

It's perfectly fair to note differences between their model and the event, but those differences do not automatically settle the question of whether the model is adequate for the purposes to which it is put (which was the original topic of this thread). If femr2 and Major_Tom were engineers, they'd understand that all engineering models are simplifications.

It appears, however, both femr2 and Major_Tom are making an even more elementary mistake: They are misrepresenting the quotation by pretending it was meant to describe the actual event, not the consequences of a model:

So the comments in BLGB, by Bazant, on WTC1 and 2, are insufficient for you?

You don't believe Bazant's own words?

It's a mental cocoon. That is what JREF is, a mental cocoon.

ROFL.

Almost exact in comparison to WHAT exactly ? (...in a paper discussing WTC1 & 2 )

It looks like femr2 and Major_Tom are ignoring the actual words they quoted. Maybe they just don't realize that differential equations come from models, not from sub-pixel measurements.