Question for Apollo20

[Golden Bear]

Well Golden Bear, please come up with a better calculation if you can.

Anybody can mouth off, but remember the story of The Little Red Hen.

Nice try. The burden isn't on me, it's on you because you are the one trying to get a paper published that credibly explains the collapses. Should I just accept your flawed mathematical model simply because I can't come up with a better one?

 

[Gravy]

Nice try. The burden isn't on me, it's on you because you are the one trying to get a paper published that credibly explains the collapses. Should I just accept your flawed mathematical model simply because I can't come up with a better one?

Says the one who hibernates during "basic questions about his absurd controlled demolitions claims season."

Keep impotently whining and running away from facts, Ursus patheticus. That productive behavior will surely change the world for the better.

 

[beachnut]

no proof from you, then the paper stands! that was easy

Nice try. The burden isn't on me, it's on you because you are the one trying to get a paper published that credibly explains the collapses. Should I just accept your flawed mathematical model simply because I can't come up with a better one?

Wrong, the burden is on you. You said it was flawed but can not produce any work to show it! You failed! You are unable to back up your talk, you failed to even try to prove your claim of his flawed mathematics. I doubt you can come close to anything resembling a paper on the WTC as the one you failed to produce evidence against, can you?

Look above my post, you can see a photo reflecting the progress on your rebuttal paper!

 

[Golden Bear]

Well Golden Bear, please come up with a better calculation if you can.

Anybody can mouth off, but remember the story of The Little Red Hen.

Also, respectfully, I don't think you answered my question about what you think a finite element analysis would show. Do you think the upper block of floors would remain rigid as it crushes down through the lower structure?

 

[uk_dave]

Surely a man of your intelligence can see that the upper floors would, in fact, not crush the entire lower structure as a rigid block, but instead would be just as likely as the lower floors to deform and "crush up", you know, seeing as how the upper and lower floors were very similar to each other structurally and materially speaking. What I mean is, if the columns and connections comprising the lower structure are likely to fail when the upper floors impact it, doesn't it just make sense that the columns and connections comprising the upper floors are just as likely to fail at impact? If not, why do you think not?

But there is a big difference between the forces acting on the upper block and those on the lower block.

The upper block no doubt sustains damage to it's leading edge during the collapse but is able to maintain some structural integrity during the fall because the lower block has some 'give' to it.

The lower block, however, is not destroyed as one entity but rather floor by floor. The upper block is destroying each floor as it progresses down through the building and each destroyed floor is adding to the mass which is falling. So the amount of free material which is destroying the lower block is increasing as the collapse progresses, but the forces acting on the upper block are pretty much constant until it comes to a stop, in other words there is no more 'give' below it, and this stop is what destroys what remains of the upper block.

 

[Max Photon]

Did you hear? Max said we should all study the collapse progression. Bust out FEA!

Like fruit flies to brown bananas...



For the life of me I can't figure out what everyone's obsession is with collapse progression.

Collapse progression is a secondary - heck - tertiary problem. Save it so you have some thought-snacks while flossing or something.

The question of interest is what INITIATED collapse.

Get that? INITIATED

I-N-I-T-I-A-T-E-D

WHAT --- INITIATED --- COLLAPSE?


The question of interest is: What initiated collapse?

 

[Apollo20]

Golden Bear:

I would be the first to admit that the calculations I, David Benson and Prof. Bazant have done on the collapse of WTC 1 & 2 are crude approximations to what actually happened. However, I believe that finite element calculations for the entire 15 or so seconds of each collapse are simply not feasible. NIST's finite element calculations only covered the moments just before collapse initiation mainly because even this short time span required massive programs and processor times. It was not practical to do more. Hence, "simple" analytical modeling of the collapse is all that can realistically be done for the full 15 seconds of descent of the upper sections. However, the nice thing about this approach is that it is quite flexible so that mass shedding can be included as well as the increasing strength of the structure as you move from the upper floors to the lower floors. I have varied these parameters over a wide range of realistic values and found that there is a large window of conditions for which a collapse, once initiated, would be self-sustaining. I really urge you to write one of these programs and prove for yourself that what I am saying is true. Seeing is believing!

The destruction of the upper block during collapse is a very interesting question. Certainly there was some crush-up occurring during crush down of the lower section, but it's the mass of the upper section that counts. I also believe that the hat truss and mechanical floors near the top of the towers gave additional strength, mass and rigidity to the upper block compared to the lower section, creating a "pile-driver" effect. However, once crush down was completed, the upper block was moving so fast (~ 50 m/s) the total destruction of the upper section was assured.

 

[uk_dave]

The question of interest is: What initiated collapse?

Oh that's easy, plane crash, structural damage, damage to the fireproofing of the floor trusses and widespread fires.

You can go home now.

 

[The Almond]

Also, respectfully, I don't think you answered my question about what you think a finite element analysis would show. Do you think the upper block of floors would remain rigid as it crushes down through the lower structure?

FEA isn't sufficient to model the entire collapse. You would also need a kinetic reaction simulator that is capable of calculating the position of every single element in the WTC as it tumbles, rotates, breaks, fractures and linearly translates. As each impact is analyzed, you need to do the FEA to determine what areas, if any are likely to fracture or bend. Now that would require models for, conservatively, about 100 different isotropic, composite, brittle and elastic materials.

The point is that FEA isn't some magic answers system where you can input a collapse time and some random variables and expect a fully modeled collapse. The WTC is a highly chaotic system and isn't likely to be bounded to only one solution in the analysis.

 

[Max Photon]

Maw, have you seen my total collapse attractor?

Golden Bear:

I would be the first to admit that the calculations I, David Benson and Prof. Bazant have done on the collapse of WTC 1 & 2 are crude approximations to what actually happened. However, I believe that finite element calculations for the entire 15 or so seconds of each collapse are simply not feasible. NIST's finite element calculations only covered the moments just before collapse initiation mainly because even this short time span required massive programs and processor times. It was not practical to do more.

Plus, if one browned out the left half of the universe to run the 15 seconds, all one would produce is noise. One noisy run. Great.

Hence, "simple" analytical modeling of the collapse is all that can realistically be done for the full 15 seconds of descent of the upper sections.

That's not going to stop the FEA crowd. They loooove their compooters and the cartoons they produce.

However, the nice thing about this approach is that it is quite flexible so that mass shedding can be included as well as the increasing strength of the structure as you move from the upper floors to the lower floors.

Here comes the interesting part...

I have varied these parameters over a wide range of realistic values and found that there is a large window of conditions for which a collapse, once initiated, would be self-sustaining.

Exactly! Apollo20 is saying that total collapse is a very strong attractor.

I really urge you to write one of these programs and prove for yourself that what I am saying is true. Seeing is believing!

This is a profoundly important point. Simple analytical techniques quickly reveal that total collapse was a very strong attractor. Apollo can see it. He is saying you can see it.

If Apollo can see it, and if you can see it, demolition planners could see it.

This means that demolition planners only needed to solve the problem of how to get the towers moving - a vastly simpler problem than using high explosives throughout the towers to cut steel or break steel connections.

How to get the towers moving? Well, no doubt demolition planners could see what Bazant could see: that only half the perimeter columns on one storey need creep to get the towers moving. Once the towers get moving - once the towers get pushed over the abyss, they are caught in the maw of the total collapse attractor.


Now, about that collapse initiation...

 

[Crazy Chainsaw]

Golden Bear:

I would be the first to admit that the calculations I, David Benson and Prof. Bazant have done on the collapse of WTC 1 & 2 are crude approximations to what actually happened. However, I believe that finite element calculations for the entire 15 or so seconds of each collapse are simply not feasible. NIST's finite element calculations only covered the moments just before collapse initiation mainly because even this short time span required massive programs and processor times. It was not practical to do more. Hence, "simple" analytical modeling of the collapse is all that can realistically be done for the full 15 seconds of descent of the upper sections. However, the nice thing about this approach is that it is quite flexible so that mass shedding can be included as well as the increasing strength of the structure as you move from the upper floors to the lower floors. I have varied these parameters over a wide range of realistic values and found that there is a large window of conditions for which a collapse, once initiated, would be self-sustaining. I really urge you to write one of these programs and prove for yourself that what I am saying is true. Seeing is believing!

The destruction of the upper block during collapse is a very interesting question. Certainly there was some crush-up occurring during crush down of the lower section, but it's the mass of the upper section that counts. I also believe that the hat truss and mechanical floors near the top of the towers gave additional strength, mass and rigidity to the upper block compared to the lower section, creating a "pile-driver" effect. However, once crush down was completed, the upper block was moving so fast (~ 50 m/s) the total destruction of the upper section was assured.

IT is so simple the top block is free to oscillate as one piece, however the bottom blocks components are fixed and oscillate individually, it is the oscillations do to impact that destroys the lower structure first, because they can not be effectively dissipated by rebounding motion.
By the time the bottom of the tower is strong enough to resist the oscillations the mass is already critical and the tower is gone, the final phase is the top block crushing itself against solid mass of the rubble pile.

 

[Major_Tom]

Golden Bear, You, too, see the upper portion as a "block" rather than a latice structure of "matchsticks". The "block" consists of mostly empty space.

If you imagine the core of the upper and lower sections as they really were, a "matchstick" lattice structure, you will see problems in how the weight of the upper portion even makes firm contact with the core columns of the lower portion.

Upper portion core columns will crash through floor panels and simply "bypass" the lower columns.

And this is true only after the first buckles form. You then have more buckes form and the probability of direct transfer of the kinetic energy of the top portion to the lower core columns becomes absurdly low.

The only reason people can begin to take the Bazant analysis seriously is that they have greatly oversimplified the "physics problem" into a "block" (it's not a block, folks), and a "spring", hence "physics 101".

 

[Golden Bear]

But there is a big difference between the forces acting on the upper block and those on the lower block.

The upper block no doubt sustains damage to it's leading edge during the collapse but is able to maintain some structural integrity during the fall because the lower block has some 'give' to it.

Please explain how the lower block has more "give" to it than the upper block, seeing as how the upper and lower block were both part of the same building, made of the same materials and designed by the same engineers. From a physical standpoint, why would the lower structure be more likely to fail than the upper structure? You can't just say the lower structure had more give to it without proving it.

 

[DGM]

Golden Bear, You, too, see the upper portion as a "block" rather than a latice structure of "matchsticks". The "block" consists of mostly empty space.

If you imagine the core of the upper and lower sections as they really were, a "matchstick" lattice structure, you will see problems in how the weight of the upper portion even makes firm contact with the core columns of the lower portion.

Upper portion core columns will crash through floor panels and simply "bypass" the lower columns.

And this is true only after the first buckles form. You then have more buckes form and the probability of direct transfer of the kinetic energy of the top portion to the lower core columns becomes absurdly low.

The only reason people can begin to take the Bazant analysis seriously is that they have greatly oversimplified the "physics problem" into a "block" (it's not a block, folks), and a "spring", hence "physics 101".

So are you saying the core itself should have remained standing?

 

[uk_dave]

Please explain how the lower block has more "give" to it than the upper block, seeing as how the upper and lower block were both part of the same building, made of the same materials and designed by the same engineers. From a physical standpoint, why would the lower structure be more likely to fail than the upper structure? You can't just say the lower structure had more give to it without proving it.

You have say a block of 15 floors bearing down upon one floor. That floor gives. You now have effectively 16 floors bearing down on one floor.

And so forth.

The upper block is moving downwards, the lower block aint going anywhere, therefore the lower block, not able to be hammered into the ground, instead is going to be destroyed floor by floor, whereas the upper block is falling but since everything is moving downwards as one entity it is able to maintain the majority of it's cohesion until it finally hits the the solid, unmovable mass that is the pile at ground level. Then the cohesion is lost and the upper block smashes itself to pieces.

 

[Golden Bear]

Golden Bear:

I would be the first to admit that the calculations I, David Benson and Prof. Bazant have done on the collapse of WTC 1 & 2 are crude approximations to what actually happened. However, I believe that finite element calculations for the entire 15 or so seconds of each collapse are simply not feasible. NIST's finite element calculations only covered the moments just before collapse initiation mainly because even this short time span required massive programs and processor times. It was not practical to do more. Hence, "simple" analytical modeling of the collapse is all that can realistically be done for the full 15 seconds of descent of the upper sections. However, the nice thing about this approach is that it is quite flexible so that mass shedding can be included as well as the increasing strength of the structure as you move from the upper floors to the lower floors. I have varied these parameters over a wide range of realistic values and found that there is a large window of conditions for which a collapse, once initiated, would be self-sustaining. I really urge you to write one of these programs and prove for yourself that what I am saying is true. Seeing is believing!

The destruction of the upper block during collapse is a very interesting question. Certainly there was some crush-up occurring during crush down of the lower section, but it's the mass of the upper section that counts. I also believe that the hat truss and mechanical floors near the top of the towers gave additional strength, mass and rigidity to the upper block compared to the lower section, creating a "pile-driver" effect. However, once crush down was completed, the upper block was moving so fast (~ 50 m/s) the total destruction of the upper section was assured.

First, I never said FEA would be feasible. I simply asked what you think one would show if it were performed.

Second, I do hope the revised version of your paper shows some calculations that prove the upper floors would remain a rigid block during the entire crush down phase. Anything short of this is just hand waving justification.

For example, you should at least try and quantify how much you think the hat truss strengthened the upper floors. You cannot simply say "well, the hat truss kept the upper block of floors together as a rigid block" without justifying that statement.

It's my understanding that the hat truss comprised only the top few floors and was meant to transfer loads between the exterior and core columns due to wind forces. You have to explain exactly how such a truss would prevent the buckling of the lowest floor of the upper block of floors when it impacts the lower structure. Bazant's theory seems to allege that only a single floor at a time in the lower structure is available to dissipate energy during crush down, therefore if you wish to keep your theory internally consistent, you have to allow the lowest floor of the upper structure to dissipate energy as well. The analysis might change once the crush up reached the floors comprising the hat truss, but again, under Bazant's theory you can't allow the hat truss to help keep the upper block of floors together unless you also allow the huge and in tact structural steel lattice below the highest floor of the lower structure to keep the lower block of floors together and rigid.

In other words, if the structural lattice below the highest floor of the lower structure is not available to help resist destruction of the lower structure, then the structural lattice above the lowest floor of the upper structure is not available to resist the destruction of the lowest floor of the upper block.

And again, I will keep coming back to the following salient point: the upper block of floors was very similar to the lower structure from a material, engineering and construction standpoint. It only stands to reason that whatever destruction occurs at impact between the upper and lower floors must be shared roughly equally between the upper and lower blocks of floors. There's simply no way around it. Bazant's theory doesn't take account of this fact, so it is incorrect.

Also, were the upper floors the only floors with mechanical floors, or did the lower structure include mechanical floors as well?

 

[Dave Rogers]

First, I never said FEA would be feasible. I simply asked what you think one would show if it were performed.

If it's not feasible, how do you propose to perform one?

Stundied.

Dave

 

[uk_dave]

And again, I will keep coming back to the following salient point: the upper block of floors was very similar to the lower structure from a material, engineering and construction standpoint. It only stands to reason that whatever destruction occurs at impact between the upper and lower floors must be shared roughly equally between the upper and lower blocks of floors. There's simply no way around it. Bazant's theory doesn't take account of this fact, so it is incorrect.

It's been explained to you.

Your failure to understand appears to come from your failure to imagine the collapse as anything but an extremely simplistic meeting of two buildings.

The falling upper block has the freedom to move, to tilt and rotate if necessary. This freedom of movement reduces the damage it sustains on the way down.

The lwoer block is fixed and rigid. It cannot accept the amount of load being placed upon the floors in the path of the falling block, so it disintegrates.

And as it disintegrates the addition of this wreckage increases the speed of the failure of the next floor and so forth.

You have to try to imagine the extremely chaotic environment during the collapse. Beams flying all over the place, floor trusses pulling the perimeter columns and some failing at the joints and some holding on to the columns and causing them to fail. Nothing is clean and neat about the collapse. It's violent and dirty and full of variation.

 

[Major_Tom]

ukDave writes:

The upper block no doubt sustains damage to it's leading edge during the collapse

This "leading edge" is single greatest "magic trick" in the Bazant model.

The "leading edge" is not a solid object. It is simply the cross section of the tower at the first floor that "gave".

It is mostly 4" thick flooring with the columns acting as "spears".

A more accurate model would be as if you were dropping one "bed of nails" upon another.

What is the probability that the nail heads will make firm contact with one another, thereby "transferring a blow" to the nails underneath.


The nails will probably bypass one another.


So ukDave, what "leading edge" are you talking about? The 4" flooring?

 

[Crazy Chainsaw]

ukDave writes:



This "leading edge" is single greatest "magic trick" in the Bazant model.

The "leading edge" is not a solid object. It is simply the cross section of the tower at the first floor that "gave".

It is mostly 4" thick flooring with the columns acting as "spears".

A more accurate model would be as if you were dropping one "bed of nails" upon another.

What is the probability that the nail heads will make firm contact with one another, thereby "transferring a blow" to the nails underneath.


The nails will probably bypass one another.


So ukDave, what "leading edge" are you talking about? The 4" flooring?

Actually I expect folding in the damaged Columns, causing pull in forces on the other beams in the core, so that core falls on core, in fact some of what you say probably happened however it was hidden lower down in the collapsing mass, however it is evident from photos that some of the damaged columns actually folded, near the impact zones.
Remember this happened on a floor by floor process and compression energy travels though steel at about 5100 meters per second.
Each pounding makes the lower structure weaker because it can not dissipate the energy though motion, it has to absorb it though deformation.