Merged Applicability of Bazant's model to the real world

[femr2]

Citation or drop it.

No. Do you own fact checking.

I've got the original as well, the pulses are still there.

Awesome.

You don't think I double-checked?

No, I don't think you did.

Have a nice day.

 

[femr2]

You failed to back up your allegation. Nice.

Here's another version of the beginning. Cuts off early.

No, that's a totally different viewpoint.

Sloppy attempts at deceit. Tsk, tsk.

Have a nice day.

 

[alienentity]

My mistake. That's a 3rd clip, I can't find the longer version. Here's the clip with the firemen, different version.

http://www.mediumrecords.com/wtc/southtower.weststreet.mpg

If I have time I'll take the audio and enhance the lower frequencies to help distinguish the pulses. But there are many other examples.

 

[alienentity]

No, I don't think you did.

Wrong again. I did. And I even mentioned that the levels were altered. No deception.

 

[Major_Tom]

Bažant and Verdure were very clear on the status of their crush-up before crush-down abstraction: It's a deliberate simplification of reality, justified by the following:

• In their model, the physics of the crush-down phase imply the amount of crush-down is greater than the amount of crush-up. That's a consequence of the homogeneity, gravity, and the simple fact that the mass of section A plus B is always greater than the mass of section B A.
• In the motivating example of the WTC towers, the amount of crush-down that occurs during the crush-down phase of their model must dominate the amount of crush-up. That's obvious because the initial size of section A is less than the initial size of section C, section C was completely crushed, and the crush-down phase is defined to be the duration of section C's crushing.
• Crushing is assumed to occur only after some threshold for elastic deformation has been exceeded. Combining that with the fact that the crushing force is always greater at the lower crushing front than at the upper, that threshold amplifies the disparity between crushing at those two fronts beyond what would be expected without any threshold.
• Bažant and Verdure may appear to believe the threshold is pretty large because they still discuss their model in terms of one of the optimistic assumptions from Bažant and Zhou: that all of the impact forces go into the columns. So far as I can tell, however, that assumption is not part of the mathematical model in BV. A large threshold would increase the dominance of crush-down over crush-up during the crush-down phase, but crush-down would predominate even without a large threshold.
• Any disintegration of the upper section A that occurs for reasons other than crush-up during the crush-down phase would increase the predominance of crush-down over crush-up during the crush-down phase, thereby improving the model's assumption that crush-up is negligible during the crush-down phase.
• The crush-down before crush-up simplification of the BV model continues to apply even if there is nothing left of section A by the end of the crush-down phase. In that case, the crush-up phase happens to be trivial, with zero duration.

Disintegration of upper section A during the crush-down phase might lead to non-uniform lateral shedding, which could interfere with the model's assumption that all lateral shedding can be absorbed into a constant compaction ratio λ. So far as I can tell, that's the main problem the BV model might have with disintegration of section A during the crush-down phase.

There are a couple of people here who seem to think any disintegration of section A during the crush-down phase would invalidate the BV model's assumption that crush-up can be neglected during the crush-down phase. So far as I can tell, that's completely nuts.

Standard disclaimer: I am not an engineer. If some qualified person is willing to point out my mistakes, I will listen.

Sometimes I listen to unqualified persons who clearly don't know what they're talking about, but I'm likely to tune them out eventually if they disregard criticism of their errors or refuse to explain salient points of their argument(s).

You'd save a lot of time if you actually read the closure to BV, whick is BL. Please read BLGB also.

Every one of my questions posed to TFK have to do with BL and BLGB. Every one of femr's citations of Bazant are from BL and BLGB, not BV.

Is is impossible to understand the answers to the questions posed by reading and citing BV alone.

You have been commenting a few weeks but I can tell by your posts that you have read BV only.

And pretty much everything you wrote is wrong.

It's crush down before crush up. You have them reversed.

 

[pgimeno]

Any issue with the following interpretation...

"The aforementioned (calculated) distance of initial crush-up would be larger if the column cross sections (in the real building) changed discontinuously right below or right above the first collapsed storey (in the real building). However, this does not appear to be the case (in the real building)...(therefore the distance of initial crush-up is not larger.)"

The author is writing from a position somewhat in limbo between the virtual and real worlds, if you ask me (which you're not) but there you go anyway

I have no issue with that interpretation, and that's an excellent example of how to take the real parameters to feed them into the model. I don't share your conclusion that he's in a kind of limbo. The column cross sections are parameters of the building; when fed into the model, the behavior of the model is that the (calculated, as you point out) distance of initial crush-up is not larger.

If any of you folks misapply the details with the Bazant et al papers, then here is the logical place for highlighting such.

That's indeed what I have been doing with MT all this time, but he seems to have quite a big amount of difficulty in understanding the simple distinction between discussing the results of applying the parameters to a model, which is what BL does, and discussing the real collapse.

Anyway, I'll keep trying.

 

[beachnut]

Choice of ψ and all that, yeah, though exceeding Mach. 1 sounds like an interesting prospect. ROFL.

You really should pay more attention Beachnut. Mach 1 as conservative ?! Funny man.

Sooo Beachnut....

Where are all these multiple sonic booms in the real world A/V footage ? That's gonna be audible for, oooh, long distance

The simple point highlighted, again, is that not only is the crush front calculated value provably wildly inaccurate (at best), but the authors are applying a derived value to the real world and making conclusions from such. Not a good idea. N/A if you will.

Have a nice day.

I did pay attention, ... You said the speed, the velocity of falling was too fast, I said nothing about the model for ejected air, but the collapse velocity they have is low, the last floor was moving 51.4 m/s. That means there is more velocity to add to the ejection. But since this is a mathematical model I understand why you can't comprehend it, or 911. Your CD theory is a delusion fed by ignorance in engineering and the need to have paranoid crazy conspiracy theories. 19 terrorists simple plot is too hard to comprehend for most of 911 truth, over their heads, 2 steps too many.

Do you read your own posts?

Their calculated crush front propagation velocity is wrong

You are wrong. Don't let that stop your goal free step by step proof of CD and attack on engineering, Bazant, and NIST. Do you have plan to tie this tripe to your step by step proof of CD?

 

[TruthersLie]

You can't seriously be suggesting that the video is doctored ?

that THIS PARTICULAR video is doctored? I have no idea.
I am pointing out that xenomorph has several doctored videos of the collapse of wtc7 which he claims are original and are doctored. They include my personal favorite which starts AFTER the collapse of the eastern mechancial penthouse, and completely ignores that part of the collapse.

isn't it dishonest to have a shortened clip of the entire collapse and to then ignore the preceeding 8 seconds? The 8 seconds which show the start of the collapse progression?

When called on this his answer is rather amusing. The collapse of the eastern mechanical penthouse is not important nor is it a part of the collapse of the entire building.

Sorry. But your source is biased and shows doctored videos. If you still want to claim his videos know that the well there is not credible.

A video doctored to highlight a gravity driven crush front progression ? Hilarious.

I never said that THIS video is doctored. Just that your source has posted doctored videos and claimed them as originals.

Have a nice day.

I always do. If you aren't having a nice day you are doing it wrong.

 

[alienentity]

Frank Greening's calculations, which are compared to actual observed collapse times yielded:

Tower 2
Final impact velocity, v = 51.2 m/s

Tower 1
Final impact velocity v = 50.7 m/s

ENERGY TRANSFER IN THE WTC COLLAPSE


'The resulting calculated values of the collapse times, tc,
(12.5 seconds for WTC 1 and 11.5 seconds for WTC 2), are already quite close to the
observed collapse times '

Assuming the measurements of researchers at 9/11 Forums are accurate, and that the final collapse times of Greening are also accurate, then the final velocity has to be faster than what Femr2 is claiming (28.8 m/s or so).

Otherwise the collapses would've taken longer. QED

 

[pgimeno]

I acknowledge your premise - that there is a clear distinction between 'model' and 'real world' - and note that the OP is "Applicability to...real world'.

I also see that you attribute all or most of Bazant's references to WTC as applying the parameters of WTC to the Bazant model(s). Let's accept that for purposes of discussion.

So at the very least your position has a clear distinction between 'model' and 'real world'. And I draw the distinction between your position which is 'Bazant applied WTC to the model' and the alternate position which is 'applying the model to real world'. The reversal is significant.

Yes, and I have that distinction very clear in my mind. It's MT who doesn't, and I accepted his derailing in order to show him for the (N+1)'th time that he is making a wrong interpretation of the papers. He is believing all this time that BL is discussing how the WTC towers behaved in reality, when it's pretty clear when reading the text in its context that the authors are discussing the behavior of the model.

In the post you reply to, I was yet again drawing that distinction line to MT, who still seems to be having difficulty with it despite all my attempts at explaining to him, to the point that I'm starting to wonder if he's deliberately lying in order to push his agenda.

On the other hand, femr2 and alienentity ARE discussing exactly about the topic. The speed of the air is an application of the model to the real world, and the reliability of the conclusions in BLGB with regard to that topic depend in part on how well certain features of the model can match real quantities. I've stated as an example numerous times, that in BLGB page 11 of the PDF (902 of the paper) there are two sections dedicated explicitly to the application of the model to the real world.

...4. ROOSD is NOT a mathematical model, therefore, it's apples and oranges....

actually a poor analogy because it implies more than it can support. ROOSD is not an irrelevant consideration. It is a base explanation of a collapse mechanism just as Bazant's assumptions of a collapse involving 'homogeneous' blocks with columns offering resistance and no distinction between core, OOS, outer columns. That is the base for Bazant's model - not the base in the real world.

So Bazant builds such maths as he requires on the model he chooses. Major_Tom is exploring the real world and he defines his collapse mechanism which just happens to correspond with the most commonly accepted model. Don't be thrown by the ROOSD terminology. Recall babies and bathwater. ROOSD is the base for the real world, not the base for Bazant's model.

What does that have to do with how I respond to MT's original question? Namely this one:

4) Is ROOSD consistent the claims of crush down preceding crush up in BV and BL?

Do you think that the distinction between being consistent or not will have any significance?

 

[femr2]

You said the speed, the velocity of falling was too fast, I said nothing about the model for ejected air

Fair enough, you were not specific beyond *final velocity*.

but the collapse velocity they have is low, the last floor was moving 51.4 m/s. That means there is more velocity to add to the ejection. But since this is a mathematical model I understand why you can't comprehend it

Real-world equivalent velocity was ~28m/s.

Their calculated crush front propagation velocity is wrong

You are wrong.

Real-world equivalent velocity was ~28m/s.

 

[pgimeno]

End of the day you have not shown that Bazant or NIST didn't know what they were talking about.

Thats pretty much the conclusion of this rather long thread.

Spot on. But they keep trying.

 

[femr2]

your source is biased and shows doctored videos.

Not my source. Not a doctored video.

 

[femr2]

Frank Greening's calculations, which are compared to actual observed collapse times yielded:

Tower 2
Final impact velocity, v = 51.2 m/s

Tower 1
Final impact velocity v = 50.7 m/s

ENERGY TRANSFER IN THE WTC COLLAPSE


'The resulting calculated values of the collapse times, tc,
(12.5 seconds for WTC 1 and 11.5 seconds for WTC 2), are already quite close to the
observed collapse times '

Assuming the measurements of researchers at 9/11 Forums are accurate, and that the final collapse times of Greening are also accurate, then the final velocity has to be faster than what Femr2 is claiming (28.8 m/s or so).

Otherwise the collapses would've taken longer. QED

A fantastic example of repeating the same mistake over and over.

Dr G's 1D slab model does not, in a similar way that the Bazant et al model(s) do not, model the actual descent mechanism.

Your logic is very funny.

In the real world, the WTC1 SW crush-front reached effective terminal velocity of ~28m/s about 4 seconds after release.

The value can be checked and measured by anyone who wants to verify it. Simply trace the SW crush front ejecta from video and transform the position/time data into velocity/time.

The value is not contested by David Benson, one of the authors of BLGB.


Have a nice day.

 

[pgimeno]

With respect to the model's assumption of vertical homogeneity, I see two possible problems with applying that assumption to the WTC towers:

• The mechanical floors might have been different enough to matter.
• Differential collapse rates between the core and the area outside the core, if combined with significant interactions between the two, could conceivably invalidate the assumption of vertical homogeneity.

If I understand you correctly, your objection to vertical homogeneity may be based upon the second of those problems. If so, that's really a problem with the one-dimensionality of the model.

If we dismiss the failure of the outer flooring system, do you think the model can be more reliably applied to what is left?

 

[pgimeno]

You're claiming that the upper block, plowing its way thru the lower structure, created a front end that matched perfectly the inside dimensions of the peripheral wall???



And magically sheared all the internal floors perfectly from outer columns ??



And left a massively unstable external wall standing in place???

You have a point here. One thing that that study can't explain is why the outer columns didn't bend inwards as the floors fell. Your explanation that it's the pressure front makes much more sense to me.

MT?

 

[beachnut]

Fair enough, you were not specific beyond *final velocity*.


Real-world equivalent velocity was ~28m/s.


Real-world equivalent velocity was ~28m/s.

Wrong. No surprise you have a CD theory.

What is 28 m/s? The average speed of the entire collapse, the first impact, the last impact?

You can't use 28 m/s as the last floor collapsing. Your speed is the velocity of collapse for the 73rd floor. What is your problem with physics? Do you have problems with math?

 

[femr2]

You have a point here. One thing that that study can't explain is why the outer columns didn't bend inwards as the floors fell.

All pressure on perimeter from internal avalanche was outwards.

Your explanation that it's the pressure front makes much more sense to me.

Oh, come on. The North-South WTC1 crush fronts are well documented at The911Forum, and have been for quite some time. Pressure front that only affects one region (SW Face) ? With another trailing behind (NW Face) ? With *dust jests* being ejected both ahead of and behind the crush fronts ?

Have you read the thread I linked earlier ?

 

[femr2]

What is 28 m/s?

The general terminal velocity of the WTC 1 SW crush front propogation. Measured by tracing the SW ejecta. Not a single value, a trend.

The average speed of the entire collapse, the first impact

No Beachnut.

, the last impact?

Ish. And most before that up to about 4s after release.

You can't use 28 m/s as the last floor collapsing.

Maybe, if you're being pedantic about the lower storey not having any OOS flooring. And some variation of the value throughout. It's a trend.

Your speed is the velocity of collapse for the 73rd floor.

May well be, but not that floor only.

 

[pgimeno]

All pressure on perimeter from internal avalanche was outwards.

How did the trusses push outwards?

Assuming for a moment that you were right, why don't we see the walls bending outwards?

Oh, come on. The North-South WTC1 crush fronts are well documented at The911Forum, and have been for quite some time. Pressure front that only affects one region (SW Face) ? With another trailing behind (NW Face) ? With *dust jests* being ejected both ahead of and behind the crush fronts ?

I don't see why not. What I do see is that the runaway hypothesis is contradicted by the behavior of the outer walls.

Have you read the thread I linked earlier ?

No, I've seen no reason to bother yet.