is this the case?

[nagasama]

hello all.
first time poster here. i have been lurking for awhile now, and i could use some feedback at this point. i need the help of the professionals.
i have an acquaintance that is rather fond of slamming bazant's model. i am rather fond of using it to quiet the strange troothers (for a few minutes at least). he has brought up some points in PM to me that are pretty far over my head. im not an expert, by any means. i believe i understand bazant's model in a literal sense, but i am certainly not a physics genius. so, if you guys could take a look at this correspondence (sorry if it is too long for the forum), and let me know if what he says is true. part true? all true? if so, why? if not, why? i really have never heard anything like he is saying argued against bazant. also, i am not using the answers as cut/paste debate ammo. i informed him that his statements were beyond my grasp and that i would be bringing them here for advice. and then sharing you guys' thoughts. and i am looking forward to your replies.
muchos thanks for your time and everything i have learned here.
nagasama

NAGA: the columns span 3 stories. so a failure on one floor would obviously have an effect on (at least) two others.

MR S.: I think you're missing the problem, naga. It's not whether columns fail post impact, it's what is generating the impact. 85+% of columns are intact. Bazant treats the whole floor as falling. Ho? What causes the dislocation of the intact columns to precipitate impact? Bazant initially proposed 800C fires, but changed that to massive overload. However, there is NO reason to claim massive overload. He just waves a wand and poof! there it is. Naga, have you ever heard of GIGO? Garbage in, garbage out? That is the fundamental problem with Bazant. His input data is erroneous. Once that occurs, the 'black box' mathematics is irrelevant. It is the same with NIST: every computer simulation they have produced required manipulated input to achieve a pre-desired outcome. And Bazant uses NIST input data...
Bazant and NIST are feeding each other. It is erroneous iteration. It might be your bible, but, sadly, they're false prophets.

NAGA: bazant believes that his collapse model would share many characteristics with a model of a controlled demolition. one important difference, obviously...no explosives needed.

MR S.: which brings us back to gigo. The 'data' they are using is NIST invented, non forensic crap.
Apparently, a big, fat, fire-breathing dragon hidden above the crash site would produce just the right amount of overload and heat to cause the buildings to collapse. And, voila, no explosives!
If initial conditions are manipulated enough, a computer simulation, like monkeys at typewriters, will produce a 'sonnet'.
Bazant is head monkey.
Naga, you claim Bazant uses conservative collapse conditions by imagining all the columns hit square on at impact.
This is actually the opposite of the case. The pressure wave of a destructive, synchronised impact is FAR greater than an 'untidy', smeared impact. Bazant uses the most destructive, and unrealistic, scenario. In truth, impacts would be chaotic (as you have signalled), no synchronicity would ensue, and the impact impulse would be far less.
Bazant IS a cheeky monkey!

NAGA: i dont think that is the case. an axially aligned impact would favor collapse arrest more than an asymmetric, rotating collapse.

MR S.: I think you are missing the importance of impulse in an impact, Naga. In an inelastic collision, a 'shock wave' is produced. This is highly destructive, and the more synchronicity, the greater the destructive nature. Non-synchronicity (whether via vertical or rotational non-alignment) will act like a 'crumple zone', and the shock wave will be damped, and massively reduced. Collapse will halt.
Bazant deliberately ignores this. Bazant's model magnifies the impulse by synchronicity of impact, thus magnifying the induced pressure wave. His 'crumpling' is measured in INCHES, and bears ZERO resemblance to real world events.
Bazant has produced a whizz bang example of GIGO. It satisfies the Physics ignorant and the complicit.
I WILL accept any position supported by verifiable data.. I DON'T accept Bazant, because his theories appear either irrelevant or fraudulent.

 

[R.Mackey]

We've had a lot of discussion on Dr. Bazant's paper. This discussion follows a familiar pattern.

First, bear in mind that he wrote several papers. The one that gets all of the attention is the 2001 paper with Dr. Yong Zhou, which only considers the progressive nature of collapse. It was written only two days after 9/11. So it has a lot of simplifications.

Those simplifications include an assumption that the initial failure would be a drop of a complete story, after the columns (all of them) on that floor were weakened to the point that they yielded under the load. It also includes a "worst case" assumption that the structure below this failing floor was completely intact, unweakened, and would catch the falling mass on the columns, rather than on the much weaker floors. The point of the paper is to show that, even under this extremely optimistic case, the Tower would still not be strong enough to resist the momentum of the falling weight, and would collapse.

So now it's been eight years, and various people have studied every single frame of every video a hundred times. We now know that the initial collapse was a rotation, dipping one edge about three floors before the last supports yielded, rather than a single floor suddenly yielding uniformly. Not a big surprise. We also know, as we did all along, that the falling mass did not land squarely on the columns below. So we don't expect Bazant & Zhou to be a very good model of what happened.

It was never intended to be one. It's a limiting case. It proves that, no matter what, the Towers were going to collapse. What actually happened looks rather different, but was even harder to withstand than the limiting case they proposed.

So, to the questions: You've proposed failures in 3-story lengths. There isn't much support for that early in the collapse. We believe that some core columns actually tore, although the perimeter, the bowing sections, did fail in lengths of three or even six stories when they buckled. But that doesn't matter.

Your opponent is complaining that Dr. Bazant doesn't treat the cause of initiation in much detail. Of course not! He had almost no information about the Towers. He assumed that a temperature of 800^oC was one possible explanation, and that's all. We don't need his paper for this, we have NIST for this, and NIST demonstrates that a much, much lower temperature -- combined with impact damage, fireproofing damage, floor bowing, and creep -- is what started the collapse. Your opponent is complaining about something that isn't even important to the paper.

Dr. Bazant does not, as your opponent claims, assume the worst loading condition. If the lower columns are hit squarely and simultaneously, this allows them to generate the greatest impulse in response, and thus have the greatest chance of survival. What actually happened, however, is the impact was indeed "smeared." This is because of the tilting behavior. That tilt, unfortunately, put the weight not on the columns, but on the floors. Those floors were never designed to carry the upper portion. Even if they were fully intact, they could support at most about 40% of the weight that was gradually dumped on them, and they were heavily damaged besides.

As a result, there is no impulse loading needed. The upper mass settles on the floors, the floors fail, as the floors fail the perimeter columns are no longer stabilized and they break away through bolt failure instead of buckling. The core actually survives the collapse, punching its way through the descending mass, but it is unstable to begin with and being loaded strangely by the debris at the bottom, so it collapses too a few seconds later.

And no explosives. There's hundreds of videos of collapse, and not one recorded the unmistakable and extremely loud shockwaves of explosives. There's not one piece of steel that shows the unmistakable pattern of high strain rate steel recrystallization that would be there if it was destroyed by explosives. There's no leftover pieces of explosives or detonation cord or anything. There's no hypothesis involving explosives, ever proposed, by anyone, that makes a lick of sense.

Hope that helps. Around here, we settled this particular argument over three years ago, but some of them are simply too stubborn and/or too stupid to give it up.

 

[Brainache]

If there is any justice in this world, this will be the shortest thread ever.

Damn Mackey! Even I completely understood that, and I dropped out of an arts degree in second year...

 

[Horatius]

Dr. Bazant does not, as your opponent claims, assume the worst loading condition. If the lower columns are hit squarely and simultaneously, this allows them to generate the greatest impulse in response, and thus have the greatest chance of survival. What actually happened, however, is the impact was indeed "smeared." This is because of the tilting behavior. That tilt, unfortunately, put the weight not on the columns, but on the floors. Those floors were never designed to carry the upper portion. Even if they were fully intact, they could support at most about 40% of the weight that was gradually dumped on them, and they were heavily damaged besides.

I think this is the heart of the fellow's mistake. He assumes that his "smeared" out collapse will still be hitting the columns, with no justification for that. Just some simple trigonometry will show that that's highly unlikely in the case where the upper section tilts prior to impact.

With that mistake cleared up, his whole notion of "Non-synchronicity (whether via vertical or rotational non-alignment) will act like a 'crumple zone', and the shock wave will be damped, and massively reduced", becomes moot, because the "shock wave" and "crumple zone" will be impacting on the floors, not the columns, so the column's responses to these events would be irrelevant.

 

[nagasama]

thanks for the replies, guys. mr. mackey and horatius i would also like to personally thank you guys (and several others here) that have given me much, much ammo to combat the ignorance of these people. brainache sorry man if i ask a few more questions and make your brain ache more haha. and yes, mr mackey, your explanations are easy to understand. i tend to reference his 2007 paper with verdure more than the 2001 paper with zhou. i assume that the same principles stand, and from what i understand, they do. this fellow seems to think that every bit of his work is fraudulent, fed to him by NIST, which was also fraudulent, thereby rendering his results false. i just dont know how to argue the point any better...besides "show me the errors in the calculations and assumptions", which no one has done. i have read NCSTAR 1 & 1A, as much from bazant as i can find, dr greenings work, gregory uhrich's stuff from here at jref and a lot of your work on the subject, mr mackey. inclusing the physics of 9/11 work that is very informative.

in response to your comments:

thats what i continue to tell this gentleman. that the model was structured in order to give the "best case" scenario for collapse. at which point, as you can see, he continues to insist that is not the case, in fact, he insists it is opposite. he then proceeds to question me about bazants "ridiculous assumptions", but does not necessarily give me specifics.
one analogy he sent me was about hammers (humor me, please):
MR S.:
Quick analogy.

A flat faced hammer will deliver more instantaneous impact, and more importantly, more impulse, than a rough faced hammer.

while i do not see the relevance of this analogy, i have swung a hammer or two. every framing hammer i have ever used has a rough face. i know they make smooth faced heavy hammers, but framers tend to use the rough faced type.
totally irrelevant, i know.
any further input is greatly appreciated.

 

[Horatius]

MR S.:
Quick analogy.

A flat faced hammer will deliver more instantaneous impact, and more importantly, more impulse, than a rough faced hammer.

I'm pretty sure, as you suspect, that his analogy is flawed, but let's assume for the sake of argument that he's correct.

Even if he's correct, if the rough faced hammer can still deliver enough of an impulse, it will still drive the nail.

He needs to demonstrate not only that the "smeared" collapse produces less impulse, he must also demonstrate that that impulse is less than it would take to collapse the floors - which is where the impulse is being applied. If he can't show both those requirements, his whole argument is a waste of time, even if we provisionally accept his analogy as being useful.

 

[rwguinn]

thanks for the replies, guys. mr. mackey and horatius i would also like to personally thank you guys (and several others here) that have given me much, much ammo to combat the ignorance of these people. brainache sorry man if i ask a few more questions and make your brain ache more haha. and yes, mr mackey, your explanations are easy to understand. i tend to reference his 2007 paper with verdure more than the 2001 paper with zhou. i assume that the same principles stand, and from what i understand, they do. this fellow seems to think that every bit of his work is fraudulent, fed to him by NIST, which was also fraudulent, thereby rendering his results false. i just dont know how to argue the point any better...besides "show me the errors in the calculations and assumptions", which no one has done. i have read NCSTAR 1 & 1A, as much from bazant as i can find, dr greenings work, gregory uhrich's stuff from here at jref and a lot of your work on the subject, mr mackey. inclusing the physics of 9/11 work that is very informative.

in response to your comments:

thats what i continue to tell this gentleman. that the model was structured in order to give the "best case" scenario for collapse. at which point, as you can see, he continues to insist that is not the case, in fact, he insists it is opposite. he then proceeds to question me about bazants "ridiculous assumptions", but does not necessarily give me specifics.
one analogy he sent me was about hammers (humor me, please):
MR S.:
Quick analogy.

A flat faced hammer will deliver more instantaneous impact, and more importantly, more impulse, than a rough faced hammer.

while i do not see the relevance of this analogy, i have swung a hammer or two. every framing hammer i have ever used has a rough face. i know they make smooth faced heavy hammers, but framers tend to use the rough faced type.
totally irrelevant, i know.
any further input is greatly appreciated.

I'm pretty sure, as you suspect, that his analogy is flawed, but let's assume for the sake of argument that he's correct.

Even if he's correct, if the rough faced hammer can still deliver enough of an impulse, it will still drive the nail.

He needs to demonstrate not only that the "smeared" collapse produces less impulse, he must also demonstrate that that impulse is less than it would take to collapse the floors - which is where the impulse is being applied. If he can't show both those requirements, his whole argument is a waste of time, even if we provisionally accept his analogy as being useful.

The rough face is to generate friction, since the impact of the face on the nail is never going to be exactly square-there is always a lateral component of some kind.
The roughness keeps the hammer face from slipping off the nail, so that all the energy is delivered to the nail

 

[Furcifer]

Technically he is correct, there is a certain amount of energy going into deformation. A hatched face hammer would tend to deform the nail a tiny, very tiny bit more. The reason framers use them is because they tend to grab the nail better, and framers don't care about the marks they leave.

 

[triforcharity]

OT post deleated.

Why wouldn't the building collapse?? Fire+steel+no firefighting=MAJOR problems has been know in the fire service for many years.

 

[nagasama]

i dont know triforcharity. i have been arguing this issue for the past 3 months with this person. he is intelligent, but for some reason he just will not accept that the model favors collapse arrest, not collapse.
it was completely obvious to me the first time i read the paper. at least he doesnt use the old trid and true ammo, "pull it!" "fire doesnt have an effect on steel!" (gotta love that one), "no steel building in the history of mankind!" etc etc blah blah blah. he has a good head on his shoulders, but for some reason he seems to have a personal vendetta against bazant.
who knows?
i actually had one guy tell me that NCSTAR 1 said that the aircraft impacts were no a significant factor in the collapses. lolwut. and he stuck to his guns even after i gave him page number after page number in the report that stated exactly opposite. like talking to a fence post at times.