leftysergeant
Penultimate Amazing
- Joined
- Jul 13, 2007
- Messages
- 18,863
Any way you slice it, Bazant is still closer to the absolute truth than little Dickie Gage will ever come.
Merged Applicability of Bazant's model to the real world
- Thread starter pgimeno
- Start date
bill smith
Philosopher
- Joined
- Feb 14, 2009
- Messages
- 8,408
Bazant is finished. He was only ever a distraction anyway. Though I would be happy for Major Tom or Femr2 to explain why we have been arguing Bazant and mixing up his hypotheses (like the ridiculous rubble layer) with the real event for so long.
The REAL problem:-
What exactly happened to the 250 massive columns connecting the top and bottom parts.allowing the top part to go into freefall in the first place.
Last edited:
leftysergeant
Penultimate Amazing
- Joined
- Jul 13, 2007
- Messages
- 18,863
They got knocked catawampus by a hundred-ton hammer and their crystal structure was compromised by extreme heat and joints were broken by thermal creep.
There was never a sound that could indicate explosive demolitions, nor any sign of damage such as would be associated with any form of thermite of which I have any knowledge.
(Nor have any of the thermite believers come near to explaining why they would put kaolin in a thermite charge.)
bill smith
Philosopher
- Joined
- Feb 14, 2009
- Messages
- 8,408
That is ludicrous Sarge, those 250 columns were not heated anything like evenly and would therefore have failed unevenly causing the top part to visibly lean before falling. (Like WTC2 did for instance)
leftysergeant
Penultimate Amazing
- Joined
- Jul 13, 2007
- Messages
- 18,863
Neither of them fell straight down.
bill smith
Philosopher
- Joined
- Feb 14, 2009
- Messages
- 8,408
Well....maybe we better not drift too far off topic Sarge.
leftysergeant
Penultimate Amazing
- Joined
- Jul 13, 2007
- Messages
- 18,863
They all started falling crooked and straightened out as collapse progessed.
More consistant with Bazant than with little Dickie.
ozeco41
Philosopher
Bill you persist in trying to "black or white" the issue.
It is really quite a simple question of how far the grey goes and how far can Bazants valid work be extended into the grey for the WTC Towers where it does not fit with accuracy.
BZ 2002 said "there was more than enough energy to ensure that the collapse of the twin towers progressed to completion without stopping half way (AND without needing any demolition)" That claim was true. It remains true. BZ even assumed the worst case - that when the top block started to fall it fell a distance - he initially said one floor but modified that so say one metre or less. Then the columns in the top block landed on those of the lower bit so that the top bit of those columns all lined up with the columns in the bottom block. Call that point "A". Even with the strength of those columns allowed for there was still enough energy for complete collapse and without demolition. (Note and remember that his estimate of "overload" said thirty one (31) times.)
Now the WTC Twin Towers did not fall with top column parts sitting on bottom column parts. So Bazant's conservative assumptions proved the towers would collapse and without need of explosives/thermate/laser beams from space etc. And that was his main purpose back then in late 2001 early 2002.
He used a conservative model which was more conservative for the Twin Towers than it would be for most other buildings because of the tube in tube construction and the manner that collapse of twin towers was started.
Then Bazant ad various colleagues wanted to develop a general model for building progressive collapse. They developed the model using concepts of "crush up/crush down" and supported those concepts using a lot of complicated looking mathematics and confusing language. Typical academics. However they never explicitly (as far as I can see) moved away from the original assumption of axial contact between columns.
So the model is not accurate in detail for WTC Towers as far as I can see. Recent discussions have been about "how far you can take it" given the base assumptions. You can take it a long way for general buildings which are not "tube-in-tube" like the twin towers. Not so far for the WTC Twin Towers.
I have no real interest in how far to take Bazant and remain valid. I have no interest in the academic competition sideline of countering with peer reviewed papers. I am satisfied by simple observation of the video and picture evidence that the progressive global collapse of the Twin Towers was inevitable and without demolition assistance.
Bazant got 31 times overload. Just for interest when I first answered the question back in early 2008 I guestimated it was in the order of 20 times to 50 times overload. Without the complicated maths.
Now recall my suggestion to "remember point A". The "jolt" which Bazant's conservative model predicted as the top block struck at "point A"? That is the "Missing Jolt" which Tony Szamboti went looking for in his paper of that name. He took Bazant's worst case as gospel. But the WTC Twin Towers did not start to collapse by the worst case of Bazant's model. Hence the futility of Tony's search for a jolt which wasn't needed. It wasn't there because it wasn't needed.
ozeco41
Philosopher
...or Heiwa.
The box on box models are pure dishonesty (or incompetence).
The real contact of the twin towers was more like two parts of a cut wire basket coming into contact. Think about that. And, yes, very thick wires.
bill smith
Philosopher
- Joined
- Feb 14, 2009
- Messages
- 8,408
In the part I have highlighted is it assumed that the upper columns remain in contact with the lower columns all the way down or would they slip off ? For the purposes of BZ and BV xombined ?
ozeco41
Philosopher
BZ has top block falling inside lower tower tube once the global collapse is under way. (See Figure 1, Stage 5) and Bazant's comments:
Ozeco post #128: "Then Bazant ad various colleagues wanted to develop a general model for building progressive collapse. They developed the model using concepts of "crush up/crush down" and supported those concepts using a lot of complicated looking mathematics and confusing language. Typical academics. However they never explicitly (as far as I can see) moved away from the original assumption of axial contact between columns."
That is correct. In BV they derive crush up and crush down equations of motion based on successive upward and/or downward axial impacts. The concept of "crush down before significant crush up" was introduced in that paper. Almost nobody seemed to notice that the justification for no significant early crush up is that there is insufficient upwards force to buckle columns in the up direction.
The concept of crush down, then crush up is just a math trick, the result of an up-down 1-D successive axial impact model.
It is not a property of real buildings and observation of verinage style demos have yet to produce one actual example to my knowledge.
Then the strangest thing happened: People began to imagine that crush down then crush up was a real physical property of buildings. The quotes I provided by R Mackey and Dave Rogers show that even people with experience in physics could easily mistakenly believe that crush down before crush up, surviving upper blocks and magic zone Bs must exist for real buildings because Bazant proves it in BV and removes all doubt in BL.
You are the first person I have seen in this forum that recognizes this.
That is correct. In BV they derive crush up and crush down equations of motion based on successive upward and/or downward axial impacts. The concept of "crush down before significant crush up" was introduced in that paper. Almost nobody seemed to notice that the justification for no significant early crush up is that there is insufficient upwards force to buckle columns in the up direction.
The concept of crush down, then crush up is just a math trick, the result of an up-down 1-D successive axial impact model.
It is not a property of real buildings and observation of verinage style demos have yet to produce one actual example to my knowledge.
Then the strangest thing happened: People began to imagine that crush down then crush up was a real physical property of buildings. The quotes I provided by R Mackey and Dave Rogers show that even people with experience in physics could easily mistakenly believe that crush down before crush up, surviving upper blocks and magic zone Bs must exist for real buildings because Bazant proves it in BV and removes all doubt in BL.
You are the first person I have seen in this forum that recognizes this.
Last edited:
I think it is quite good an approximation, though. If you observe the crush front, you can see that the height from it to the top is more or less constant (the horizontal ejection of dust gives you a good estimation of where the crush front is). It's also evident that the visible part of the top of the building remains undamaged at all times during crush-down.
The red line superimposed here has the same height in all frames. Note that in the first frame, it doesn't reach the crush front, meaning that at least one more floor is crushed afterwards.
That question is interesting in view of the recent attacks to his work, though, as they are based on a wrong understanding of how models work. Also for people to understand that it's not necessary for the real world to behave exactly like the model in order for the model to be applicable to the real world. And also for people to understand that in spite of that, there are limits to that applicability itself.
When the limits of the model are not well known or understood, a comparison with the real world is helpful to see how good an approximation the model is. If the model gives a decent approximation of a certain parameter when compared to the real world, there is a basis to think that it can give approximate predictions in other real world cases. It may seem random, but in some cases having that approximation is better than having nothing at all.
In the real WTC case, the comparison of the model with the real world shows little difference in expected (by the model) vs. real collapse time, for example. That hints towards the utility of Bazant's model to estimate collapse times to a certain accuracy. Two specific and very similar cases are not enough to be convinced, but the material is now on the table for other engineers to use it as a basis and make their own comparisons.
ozeco41
Philosopher
# I noticed that comment when the paper was first published. Disagreed with it then for a couple of reasons and decided that I did not agree BUT could not be bothered to follow the argument through to see if I could justify a different assumption and thereby rebut Bazant. No way would I be up to decrying a highly regarded academic unless the grounds were clear and clearly winnable. So totally different to my approach to (say for example) Tony Szamboti's work and David Chandler's. Both of them make easy to see false assumptions as premises for their analyses and are therefore (relatively) easy to rebut.
...amd I have long suspected that the conclusions they draw are artefacts of the base assumptions but I do not have the energy or interest to prove that so have never previously commented on it. I simply do not rely on Bazant for my own explanations as explained in previous posts.
...I have no basis for comment either way.
...In my career as a practising engineer then as a manager of engineers I have on several occasions seen belief in authority figures taken too far by disciples who were using the work of the authority. Two of those involved structures related to the main water supply pipeline serving Sydney. Neither world shattering but on both occasions I got no thanks for identifying fundamentally wrong reasoning. One case mattered. The other didn't.
The underlying problem IMNSHO is that people so often get too close to the detail and lose the big picture or context and/or base assumption. A lot of the "discussion" (confrontation) truthers v debunkers on WTC matters is about detail out of any rational context.
Without going to too much derailing detail the big picture for WTC 7 makes any suggestion of demolition ridiculous. It is an ancillary event to aircraft strikes on each of the twin towers. The idea that anyone could pre-plan to demolish WTC 7 under the cover of a couple of aircraft strikes it ludicrous. The idea that anyone could expediently arrange demolition at the last moment seeing how good a scene the Twin Towers were setting is beyond any sense of possibility. So there is no point arguing about free fall. And no point bothering to counter the "truthers" ploy of making the stupid claim that FFA == demolition. The whole idea of demolition is beyond any possibility. But the reason I state that is as an example of "losing the plot" --- "forgetting the context" -- losing sight of the premise assumptions OR "not seeing the forest for the trees"
End of adrenaline rush. 
Blush
ozeco41
Philosopher
...understood.
Certainly..
..BUT (Make that a big BUT ) Always keep in mind that wrong methods which on one or two occasions give correct answers for wrong reasoning are a trap waiting for the unwary...All too often the wrong method can give right answers for the wrong reasons..(And don't ask me for a foolproof way to check -- just never forget your framing assumptions. Never let use of those assumptions become so routine that you forget how vulnerable they are. End of sermon from old fart.
)
...yes but see previous sermon
Fully agreed. It's easy to lose the big picture and assume omnipotent properties on the details...BUT (Make that a big BUT ) Always keep in mind that wrong methods which on one or two occasions give correct answers for wrong reasoning are a trap waiting for the unwary...All too often the wrong method can give right answers for the wrong reasons..(And don't ask me for a foolproof way to check -- just never forget your framing assumptions. Never let use of those assumptions become so routine that you forget how vulnerable they are. End of sermon from old fart.
ozeco41
Philosopher
Here is an example of Newton's Bit conjuring up a surviving upper block and the magic zone B in his description of how real buildings would collapse.
From page 2 of the OOS model thread
I asked him:
"1) In BL, can you explain why Dr Bazant insists that crush down must be complete before crush up occurs. Does he mean this literally?
2) Do you consider the equations of motion in BV, equations 12 and 17, to be accurate considering the information in the ROOSD study?"
He answered: " ffs Read the paper. Here, let me explain it to you:
The upper block is accelerating at near g. This means that there is very little force being applied to it. We can imply that the absolute maximum height of destruction occurring through the upper block will happen at a rate equal to (g - a). However the upper block has some residual strength. This force is much less than the original capacity upper block which is somewhere in the neighborhood of 3*m*g.
There will be, during the initial stages of the collapse that forms the rubble layer, destruction on both the upper block and lower block. But once it gets moving? Not so much.
You've provided no information on how this is incorrect."
Original post http://www.internationalskeptics.com/forums/showpost.php?p=5938765&postcount=77
I have given direct quotes from R Mackey, Dave Rogers and Newtons Bit applying the concept of crush down, then crush up, the surviving upper block and the magic zone B introduced in the BV progressive collapse model to descriptions of how they believe real buildings behave. 3 examples from 3 different posters who have experience problem-solving using the tools of physics.
They all have a good level of education but they all made the same mistake. Just a coincidence? Where did all three posters get the idea that crush down, then crush up and upper block survival can be applied to real buildings?
(Hint: Originally from Bazant's progressive mechanics derived in BV, proven "beyond doubt" in BL and applied to the WTC towers in BLGB)
From page 2 of the OOS model thread
I asked him:
"1) In BL, can you explain why Dr Bazant insists that crush down must be complete before crush up occurs. Does he mean this literally?
2) Do you consider the equations of motion in BV, equations 12 and 17, to be accurate considering the information in the ROOSD study?"
He answered: " ffs Read the paper. Here, let me explain it to you:
The upper block is accelerating at near g. This means that there is very little force being applied to it. We can imply that the absolute maximum height of destruction occurring through the upper block will happen at a rate equal to (g - a). However the upper block has some residual strength. This force is much less than the original capacity upper block which is somewhere in the neighborhood of 3*m*g.
There will be, during the initial stages of the collapse that forms the rubble layer, destruction on both the upper block and lower block. But once it gets moving? Not so much.
You've provided no information on how this is incorrect."
Original post http://www.internationalskeptics.com/forums/showpost.php?p=5938765&postcount=77
I have given direct quotes from R Mackey, Dave Rogers and Newtons Bit applying the concept of crush down, then crush up, the surviving upper block and the magic zone B introduced in the BV progressive collapse model to descriptions of how they believe real buildings behave. 3 examples from 3 different posters who have experience problem-solving using the tools of physics.
They all have a good level of education but they all made the same mistake. Just a coincidence? Where did all three posters get the idea that crush down, then crush up and upper block survival can be applied to real buildings?
(Hint: Originally from Bazant's progressive mechanics derived in BV, proven "beyond doubt" in BL and applied to the WTC towers in BLGB)
Last edited:
Here is a good example of how easy it is to mix the 2002 BZ argument and the 2007 BV crush down and crush up equations of motion if you are not careful:
Myriad wrote: "Bazant's model is a limiting case representing the most favorable assumptions for collapse arrest. Among those assumptions is that all the weight of the falling mass -- even the already crushed and broken rubble -- somehow lands squarely on columns.
In that model, meaning under those assumptions, crush-down precedes crush-up. Bazant shows how and why.
The extent to which crush-down did not precede crush-up in the actual collapse indicates only that those favorable assumptions for collapse arrest were not true, so collapse arrest was even more impossible."
original post http://www.internationalskeptics.com/forums/showpost.php?p=5940324&postcount=86
Here Myriad freely mixes the BZ argument (2002) and it's simple one collision model with the crush up, crush down progressive collapse model presented in BV (2007).
A main purpose of BV (2007) was to derive the crush down equation (eq 12) and the crush up equation of motion (eq 17) for the crush front and roofline to accurately predict the movement of real buildings. The phrase "limiting case representing the most favorable assumptions for collapse arrest" has no meaning in the 2007 paper because BV equations 12 and 17 are derived to predict real motion of real buildings, not some theoretical extreme limiting case only.
Bazant talks about assumptions most favorable for survival in the one collision model in BZ (2002). It is a mistake to assume the same assumptions are applied to the crush up crush down model in BV published 5 years later with a very different purpose stated clearly in the introduction.
You cannot just mix all 4 Bazant papers together like you are making mashed potatoes. BZ gives one argument while BV, BL and BLGB develop equations of motion to describe real movement of real buildings, and we can see the equations applied to the WTC towers in BLGB.
You cannot quote about the assumptions most favorable for survival from the 2002 paper to refute my arguments against collapse progression model from a different paper describing a different model from a 2007 paper.
In the quote can you see how he mixes the two models without realizing it?
Myriad wrote: "Bazant's model is a limiting case representing the most favorable assumptions for collapse arrest. Among those assumptions is that all the weight of the falling mass -- even the already crushed and broken rubble -- somehow lands squarely on columns.
In that model, meaning under those assumptions, crush-down precedes crush-up. Bazant shows how and why.
The extent to which crush-down did not precede crush-up in the actual collapse indicates only that those favorable assumptions for collapse arrest were not true, so collapse arrest was even more impossible."
original post http://www.internationalskeptics.com/forums/showpost.php?p=5940324&postcount=86
Here Myriad freely mixes the BZ argument (2002) and it's simple one collision model with the crush up, crush down progressive collapse model presented in BV (2007).
A main purpose of BV (2007) was to derive the crush down equation (eq 12) and the crush up equation of motion (eq 17) for the crush front and roofline to accurately predict the movement of real buildings. The phrase "limiting case representing the most favorable assumptions for collapse arrest" has no meaning in the 2007 paper because BV equations 12 and 17 are derived to predict real motion of real buildings, not some theoretical extreme limiting case only.
Bazant talks about assumptions most favorable for survival in the one collision model in BZ (2002). It is a mistake to assume the same assumptions are applied to the crush up crush down model in BV published 5 years later with a very different purpose stated clearly in the introduction.
You cannot just mix all 4 Bazant papers together like you are making mashed potatoes. BZ gives one argument while BV, BL and BLGB develop equations of motion to describe real movement of real buildings, and we can see the equations applied to the WTC towers in BLGB.
You cannot quote about the assumptions most favorable for survival from the 2002 paper to refute my arguments against collapse progression model from a different paper describing a different model from a 2007 paper.
In the quote can you see how he mixes the two models without realizing it?
Last edited: