You can't count, Heiwa. Here's a screen shot of the beginning of the CD :
The CD does not begin at floors 4-6, and the top section is a fraction smaller than the lower section.
[Moderated] Steel structures cannot globally collapse due to gravity alone
- Thread starter Heiwa
- Start date
You can't count, Heiwa. Here's a screen shot of the beginning of the CD :
The CD does not begin at floors 4-6, and the top section is a fraction smaller than the lower section.
Prove it. Provide some calculations then. But please don't just expect us to take your word for it.
Gravy, in your usual style you continue to misquote. Two miles drop? Do I say that? Regardless of drop height impact force F equals reaction force -F in size (but not direction). Applies to anything incl. the Vitry concrete building.
From an exchange on and around post #744 in this thread :
GlennB said:
So ... you did say it, both then and long before. Why can't you just admit it?
*The two-mile drop.
BenBurch
Gatekeeper of The Left
So, then no amount of snow applied (slowly) to a all-steel roof can ever make it collapse?
What I said discussing something from a theoretical point of view was:
"No - not really ... even after a two mile drop and a plenty of energy/forces at impact. As the upper part C is smaller (1/10th of A) and can absorb less strain energy than the lower, bigger part A on ground, the upper part C is destroyed completely before part A is totally destroyed. After part C is totally destroyed it does not apply any force on what still remains of part A.
You see, you cannot destroy a structure by dropping a piece of it on the whole.
But if part A had enough strain energy and was elastic enough to absorb all energy involved at the contact and that also part C could absorb that energy (or half of it! and no local failures develop), then part C would bounce - maybe a mile and 3/4 up. Big bounce. "
You see, Glenn B, you have to quote properly!
Actually - according to NIST and Bazant & Co the drop height doesn't matter as they assume that the upper part C is rigid during crush down and does not get affected at all. It remains intact! But after part C has crushed part A, part C is not rigid anymore ... and crushes up = gets destroyed by contact with the ground (or the rubble of part A). Quite unscientific. Part C cannot be rigid at one moment and not rigid another but that is the ONLY way NIST and Bazant & Co can explain the crush down of WTC 1. According basic structural damage analysis (and a small drop 0.5 or even 3.6 m) part C of WTC 1would just get stuck on top of part A! Both parts C and A would be damaged at the interface and the damages would mirror each other.
Had the structure been more like a sponge part C (a small piece of sponge) would just bounce on part A (the bigger piece of sponge) ... and that would be it.
NIST and Bazant & Co cheat: part C is assumed to have a different (rigid) structure than part A (not rigid) and then, OF COURSE, part C can crush down part A. Cheat? It is criminal falsification of a technical report or model to explain something.
It seems I have won the discussion about the subject of this thread. Only you, Architect and Gravy (of course) try in vain still to change the subject. So I will not respond to your nonsense any longer. Real comments are of course still welcome.
twinstead
Penultimate Amazing
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- Apr 8, 2005
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- 12,374
Here's a real comment: nobody whom I have showed this thread to, and that includes people who I know are experts, thinks you know what you are talking about. Until you can convince a real expert you are right, all we have are your opinions.
Opinions don't "win" debates.
Actually, it was you who specifically raised the claim that "FoS>3" first on this thread, all I have done is ask you to provide calculations to prove that and - as a starting point - given you some figures which quite clearly show that the safety factor was nowhere near 300%. You in turn stated:
I've challenged you to prove this. If your concern is derailing of the current thread, however, then you'll be delighted to know that I've started a thread so you can cover it.
Gravy
Downsitting Citizen
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- Mar 27, 2006
- Messages
- 17,078
Yes, and you repeat it below. Now show your math. Don't make me ask again.
So -- you still maintain that a two-mile drop of a smaller upper section will not destroy the lower section ?
This position is exactly what you have denied making, and here you are making it again. In plain view.
Do you ever listen to yourself?
Bump for Heiwa. Point not yet answered.
You have misunderstood the subject - drop a piece of structure on a bigger piece of similar structure and see what happens! As far as I am concerned snow is slightly different from steel. Try to keep on topic, pls.
As far as I am concerned it was not snowing on 911
phunk
Illuminator
- Joined
- Aug 10, 2007
- Messages
- 4,127
The sum of all forces on the upper block is only m*g if it's in freefall, it's impossible for it to be m*g during a collision with the lower block.
The force upper, moving part C applies on lower part A at contact is ideally the potential energy applied divided by the distance displaced during contact, i.e. a dynamic phenomenon. Evidently the lower part A applies an opposite reaction force on part C at the same time.
The pressure upper, moving part C applies on lower part A at contact is the potential energy applied divided by the volume compressed during contact, a similar dynamic phenomenon. And again lower part A applies an opposite reaction pressure on part C.
Thus the force/pressure developed at contact depends on the displacement/compression during the event ... so you have to keep an eye on those. As potential energy is transformed into other forms of energy, e.g. heat, elastic (can be stored in the structure) or plastic structural deformation or failures, during the event, you can be sure that it will be arrested after a while, particularly when parts A and C have same structure, and a static equilibrium state develops where the force of upper part C, i.e. its mass times g, on part A is balanced by an opposite reaction force of same magnitude by part A on part C. Part C gets stuck on top op part A.
NIST in its infamous report (read conspiracy theory) about the WTC 1 destruction assumes that part C is rigid - indestructible - and that part A is non-rigid - easily destructible - and that the potential energy applied by part C exceeds the total strain energy that part A can absorb and that therefore part A is destroyed in 1000000's of pieces - global collapse ensues - except that then part C is never destroyed. It is Bush nonsense of course. Part C is not rigid.
Bazant & Co assume the same in their conspiracy theory except that part C becomes non-rigid after crush down and is destroyed in a crush up due to contact with ground. It is a variation of the NIST Bush nonsense but ensures that part C is actually destroyed, which NIST forgot to explain.
For more info about the NIST and the Bazant & Co conspiracy theories, pls visit the Gravy web site
Edited by Gaspode:
Removed personal remarks
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rwguinn
Penultimate Amazing
Duh.
Correct. F=m*g-Fult
It can be damn close, though--and was, especially once the first 10 or 20 floors below the damage went...
Gravy
Downsitting Citizen
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- Mar 27, 2006
- Messages
- 17,078
Third time: you claim that 30 stories of a Twin Tower, if dropped from a height of two miles, would not destroy the lower 80 stories.
Prove it. Show your math, or retract your claim.
While you're at it, please respond to the demolition video posted above, which shows a smaller (or at best, equal-sized) section destroying a lower section that likely is of equal or stronger construction.
Heiwa
A separate thread has been started for you to defend your position on safety factors. You might wish to raise the relevent polints there rather than run the risk of derailing this thread again.
http://www.internationalskeptics.com/forums/showthread.php?t=137095
A separate thread has been started for you to defend your position on safety factors. You might wish to raise the relevent polints there rather than run the risk of derailing this thread again.
http://www.internationalskeptics.com/forums/showthread.php?t=137095
Last edited by a moderator:
rwguinn
Penultimate Amazing
Even there, he blows it, and does not comprehend his error:
"You have misunderstood the subject - drop a piece of structure on a bigger piece of similar structure and see what happens! "
Except what he keeps ignoring (intentionally, it would seem) is that each floor below the initial damage area must be treated as a seperate entity.
thus, you are not dropping "a piece of structure on a bigger piece of similar structure and see what happens!"--you are dropping a large piece of the structure (the upper part above the initial damage) onto a smaller part--ONE FLOOR!
Actually, that's not entirely correct. You are dropping a piece of structure on a lower structure which depended on the upper for overall stability in the first place. By ignoring the important structural contribution posed by the building as a whole he makes a fundamental error.
Gravy
Downsitting Citizen
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- Mar 27, 2006
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- 17,078
I've been giving him the benefit of the doubt and assuming that he's arguing along the lines of the first Bazant paper: that here's what would happen if the load was evenly distributed across the structure. Of course that doesn't reflect reality, but I'm asking that Heiwa support his claim using the most basic model and math. Perhaps he's too busy jumping on his bathroom scale, scratching his head, and wondering what's wrong with the scale.
rwguinn
Penultimate Amazing
I was merely trying to keep it simple...
Troofers refuse to recognize the concept of a structural system, so I thought a simple "demo" of the false assumptions would suffice to point out the Basic error.
Heiwa refuses to think of the building as a system, except when the "small part" falls as a system on the "large part" as a system...
Heiwa,
I've noticed that you've declined to respond to my posts. I'd hate to think that it's because I'm a mechanical engineer, and you'd rather not talk to other MEs. I have to tell you that I found your last response ("read my paper") to be completely unsatisfactory. Since your paper & subsequent postings are riddled with errors.
I'm sure that others have given you their take. Here's mine.
Fundamental flaws in your analysis (i.e., "tripod" paper).
The "strain energy per floor" is significant to the total energy balance. It is irrelevant to the question of whether or not the collapse is halted. The only strain energies that play a part in halting the descent of the upper block are the local strain energies at the contact points between the upper & lower blocks.
A "rigid block" is not equivalent to a block with "infinite strain energy". It simply means that it moves as a unit. (An "indestructible rigid body" would fit your description.) Your objection to Bazant's "no crush up" simplification is correct. FOR THE MOMENT. When crush happens, it progresses both upwards and downwards. But very quickly after the crush begins, the open structure of the upper block becomes "impacted" with the debris of the collapse. The bottom edge of the upper block becomes almost a solid surface of impacted debris. This phenomenon does not occur for the lower block, because each floor's debris starts from a zero velocity. Since the upper block has been falling for several floors, it sweeps thru the crushing floor faster than the debris from that floor are descending, thereby incorporating its debris into the mass of the descending block or ejecting it sideways.
As a direct result of this, Bazant's assumption of a rigid upper block turns out to be very reasonable.
Nonetheless, he has incorporated improvements to this assumption, that allow immediate crush both upwards & downwards, in his 2008 paper.
In your tripod paper, you state: The amount of potential energy, PE, due to downward movement of the WTC 1 upper part mass was definitely too small to turn the lower structure into 100 000's of tiny pieces and dust.**
This is true. It is also irrelevant.
The KINETIC energy of the upper block did NOT break all of the lower block's pieces into dust & tiny debris. Neither did the kinetic energy of the upper block have to exceed the strain energy of even one single story in order to continue the crush. It did have to exceed the strain energy of a small portion of the structure that was far, far less (perhaps on the order of 10,000x less) than the total strain energy of one single story.
In order for the collapse to continue, the kinetic energy of the upper block had to exceed the sum of the strain energy of the thousands of comparatively small points of contact between the upper block & the lower block. For gross simplification, let's assume that these points of contact are principally 290 column stub ends contacting 290 thin concrete floor slabs. In all of these cases, the limited strain energy capacity of the concrete is going to result in a prompt failure of the concrete. Subsequent entrapment of the column end in the fractured concrete debris (e.g., rebar or cross trusses) will then torque the column one direction or another, fracturing its restraints (bolts and welds). And the descent of the upper story continues.
Again, the strain energy capacity of these small segments of the concrete floors and the bolts and welds is a miniscule portion of the total strain energy of all the components structures of that floor. And yet, once these components have been destroyed, the crush down continues.
In order for the collapse to be arrested, two requirements must be met.
1. The maximum local stress generated at each contact must be less than the ultimate strength of both contacting components.
2. The local strain energy in deformation at each contact must not exceed the strain energy capacity of the less "tough" structure.
If BOTH of these conditions are met at a sufficiently large number of points such that the sum of all the forces EXCEEDS the weight (m x g) of the upper block for a sufficiently long time that the integrated impulse, (the sum of forces - weight) x time, exceeds the momentum of the upper block, THEN the upper block will be brought to a halt.
In math terms, IF Integral[(Fi - mg) dt] > m v then the upper block will be brought to a halt, where Fi = local force, m = mass of upper block, v = downward velocity & g = grav. constant.
You must include the weight term in this equation because gravity is a force that is acting on the block throughout the collision. Viz., if v is epsilon greater than 0, then the force necessary to arrest the upper block is not zero. It is a value slightly greater than mg.
In energy terms, if the sum of all the individual strain energies of all the surviving contacts exceeds the kinetic energy PLUS the strain energy of static loading, then the block will be brought to a halt.
Again, if Integral[Ui] > KE + Us, then the block will be brought to a halt. Where Ui = all the local strain energies, KE = the kinetic energy of the upper block, and Us = the strain energy associated with the statically loaded case.
Note that in ship collisions, all the significant forces act horizontally. The weight & buoyancy forces cancel each other out. This is not true in a falling collision.
In summary, your errors are:
1. You can not determine global forces, stress, or strain energy a priori. You MUST determine them locally, and sum them to determine the global result (crush or no crush).
2. You can not AVERAGE forces, stresses or strain energies over bigger or smaller portions of the building. This ignores stress concentrations and local strain energy concentrations, which are absolutely crucial to progressive collapse.
3. You can not use the load carrying capability of the a column or beam that is properly constrained to determine the load carrying capacity of columns and beams that have had one or more connections removed. You implicitly do this when ever you bring up the issue of the Factor of Safety built into the structure. The factor of safety has meaning ONLY when the columns are undamaged and properly constrained. Without those constraints, the load carrying capacity of those beams drops by orders of magnitude. Especially for lateral loads. This is, BTW, the precise reason that the structures failed at the crush zone and not above or below it.
Other important issues you've not addressed in this paper:
4. The initial failure involves 3 floors, not one. The failure of a single column compromises the entire column, which is 3 stories high.
5. Your analysis does not allow for the significant effects of the stagger of adjacent columns. In other words, by the time that the crush down has reached any particular floor, fully 2/3rd of the columns and trusses supporting that floor have already been severely compromised. This damage occurred because those columns reach up 1 & 2 stories higher, and were damaged when those higher stories were destroyed.
These are the major errors in constructing your analysis. There are others.
Some examples:
1. "no evidence that the core structure displaced downward". Nonsense. The roof displaced downward. If the core did not, it'd be sticking out of the roof.
2 "no evidence of any simultaneously buckled visible, outside wall columns in the fire zone". Nonsense. Clear, unequivocal video images of massively buckled exterior columns.
3. All of your "rigid body" objections are straw-men arguments, since neither NIST nor Bazant intended them as any more than simplifying approximations. Rigid bodies are NOT required for either NIST's or Bazant's conclusions.
4. No "solid, intact columns below were overloaded by gravity only". Heated (ie., weakened), bent (i.e., unstable) columns buckled and had their connections snapped to initiate the collapse (or crush). After the crush down began, columns that had been massively compromised (by damage to already crushed upper floors) had their few remaining connections destroyed. The columns themselves were almost never overloaded, as proven by the absence of columns with massive plastic strain left in the debris.
5. The specific (& a bit deceptive, on your part) reason that your analysis says that the upper block collapses initially is that you've drawn the bottom "green line" that defines the upper block too low. You've drawn it to encompass the upper block, all of the impact floors, plus (it appears to me) a couple undamaged lower floors for good measure. You should redraw the blocks to define an undamaged upper block, an undamaged lower block and a damaged group of impact floors. If you do it like this, you'll find that the impact floors crush first. The upper block descends because the impact floors crush, the upper floors pack in, and the lower floors start to crush down.
Just about like Bazant's model says. How 'bout that?!
There's lots more that's flawed. That's enough for now.
___
** The source of energy to pulverize the contents and their contribution to slowing the descent of the upper block.
For any piece of the tower that was thrown clear of the footprint, the deformation that occurred when it hit the street (or other object) obviously did NOT contribute to slowing the descent of the upper block.
The energy to pulverize the contents into tiny pieces and dust was provided by the EXCESS potential energy of all the mass above any given piece, less the energy lost to disassembly, PLUS the potential energy of that piece above the ground.
A large portion of the concrete was held within the footprint of the towers by the intertwined rebar and was ground to dust within the churning mass of the crushing tower, thereby contributing to slowing the upper block. A smaller portion of the concrete was thrown clear of the towers and was reduced to dust as it collided with the street.
The bolts and welds were snapped as each floor disassembled, slowing the descent.
Most of the external columns were thrown out of the footprint, and their bending & damage did not contribute to the slowing of the upper block at all.
Almost all of the core beams were contained within the footprint. While the disassembly of the upper core columns may have contributed to the slowing the upper block, the lower 40 stories or so did not, as they were seen still standing in the North Tower.
The grinding into small pieces of the contents of the towers did contribute to slowing the descent of the towers.
tom
I've noticed that you've declined to respond to my posts. I'd hate to think that it's because I'm a mechanical engineer, and you'd rather not talk to other MEs. I have to tell you that I found your last response ("read my paper") to be completely unsatisfactory. Since your paper & subsequent postings are riddled with errors.
I'm sure that others have given you their take. Here's mine.
Fundamental flaws in your analysis (i.e., "tripod" paper).
The "strain energy per floor" is significant to the total energy balance. It is irrelevant to the question of whether or not the collapse is halted. The only strain energies that play a part in halting the descent of the upper block are the local strain energies at the contact points between the upper & lower blocks.
A "rigid block" is not equivalent to a block with "infinite strain energy". It simply means that it moves as a unit. (An "indestructible rigid body" would fit your description.) Your objection to Bazant's "no crush up" simplification is correct. FOR THE MOMENT. When crush happens, it progresses both upwards and downwards. But very quickly after the crush begins, the open structure of the upper block becomes "impacted" with the debris of the collapse. The bottom edge of the upper block becomes almost a solid surface of impacted debris. This phenomenon does not occur for the lower block, because each floor's debris starts from a zero velocity. Since the upper block has been falling for several floors, it sweeps thru the crushing floor faster than the debris from that floor are descending, thereby incorporating its debris into the mass of the descending block or ejecting it sideways.
As a direct result of this, Bazant's assumption of a rigid upper block turns out to be very reasonable.
Nonetheless, he has incorporated improvements to this assumption, that allow immediate crush both upwards & downwards, in his 2008 paper.
In your tripod paper, you state: The amount of potential energy, PE, due to downward movement of the WTC 1 upper part mass was definitely too small to turn the lower structure into 100 000's of tiny pieces and dust.**
This is true. It is also irrelevant.
The KINETIC energy of the upper block did NOT break all of the lower block's pieces into dust & tiny debris. Neither did the kinetic energy of the upper block have to exceed the strain energy of even one single story in order to continue the crush. It did have to exceed the strain energy of a small portion of the structure that was far, far less (perhaps on the order of 10,000x less) than the total strain energy of one single story.
In order for the collapse to continue, the kinetic energy of the upper block had to exceed the sum of the strain energy of the thousands of comparatively small points of contact between the upper block & the lower block. For gross simplification, let's assume that these points of contact are principally 290 column stub ends contacting 290 thin concrete floor slabs. In all of these cases, the limited strain energy capacity of the concrete is going to result in a prompt failure of the concrete. Subsequent entrapment of the column end in the fractured concrete debris (e.g., rebar or cross trusses) will then torque the column one direction or another, fracturing its restraints (bolts and welds). And the descent of the upper story continues.
Again, the strain energy capacity of these small segments of the concrete floors and the bolts and welds is a miniscule portion of the total strain energy of all the components structures of that floor. And yet, once these components have been destroyed, the crush down continues.
In order for the collapse to be arrested, two requirements must be met.
1. The maximum local stress generated at each contact must be less than the ultimate strength of both contacting components.
2. The local strain energy in deformation at each contact must not exceed the strain energy capacity of the less "tough" structure.
If BOTH of these conditions are met at a sufficiently large number of points such that the sum of all the forces EXCEEDS the weight (m x g) of the upper block for a sufficiently long time that the integrated impulse, (the sum of forces - weight) x time, exceeds the momentum of the upper block, THEN the upper block will be brought to a halt.
In math terms, IF Integral[(Fi - mg) dt] > m v then the upper block will be brought to a halt, where Fi = local force, m = mass of upper block, v = downward velocity & g = grav. constant.
You must include the weight term in this equation because gravity is a force that is acting on the block throughout the collision. Viz., if v is epsilon greater than 0, then the force necessary to arrest the upper block is not zero. It is a value slightly greater than mg.
In energy terms, if the sum of all the individual strain energies of all the surviving contacts exceeds the kinetic energy PLUS the strain energy of static loading, then the block will be brought to a halt.
Again, if Integral[Ui] > KE + Us, then the block will be brought to a halt. Where Ui = all the local strain energies, KE = the kinetic energy of the upper block, and Us = the strain energy associated with the statically loaded case.
Note that in ship collisions, all the significant forces act horizontally. The weight & buoyancy forces cancel each other out. This is not true in a falling collision.
In summary, your errors are:
1. You can not determine global forces, stress, or strain energy a priori. You MUST determine them locally, and sum them to determine the global result (crush or no crush).
2. You can not AVERAGE forces, stresses or strain energies over bigger or smaller portions of the building. This ignores stress concentrations and local strain energy concentrations, which are absolutely crucial to progressive collapse.
3. You can not use the load carrying capability of the a column or beam that is properly constrained to determine the load carrying capacity of columns and beams that have had one or more connections removed. You implicitly do this when ever you bring up the issue of the Factor of Safety built into the structure. The factor of safety has meaning ONLY when the columns are undamaged and properly constrained. Without those constraints, the load carrying capacity of those beams drops by orders of magnitude. Especially for lateral loads. This is, BTW, the precise reason that the structures failed at the crush zone and not above or below it.
Other important issues you've not addressed in this paper:
4. The initial failure involves 3 floors, not one. The failure of a single column compromises the entire column, which is 3 stories high.
5. Your analysis does not allow for the significant effects of the stagger of adjacent columns. In other words, by the time that the crush down has reached any particular floor, fully 2/3rd of the columns and trusses supporting that floor have already been severely compromised. This damage occurred because those columns reach up 1 & 2 stories higher, and were damaged when those higher stories were destroyed.
These are the major errors in constructing your analysis. There are others.
Some examples:
1. "no evidence that the core structure displaced downward". Nonsense. The roof displaced downward. If the core did not, it'd be sticking out of the roof.
2 "no evidence of any simultaneously buckled visible, outside wall columns in the fire zone". Nonsense. Clear, unequivocal video images of massively buckled exterior columns.
3. All of your "rigid body" objections are straw-men arguments, since neither NIST nor Bazant intended them as any more than simplifying approximations. Rigid bodies are NOT required for either NIST's or Bazant's conclusions.
4. No "solid, intact columns below were overloaded by gravity only". Heated (ie., weakened), bent (i.e., unstable) columns buckled and had their connections snapped to initiate the collapse (or crush). After the crush down began, columns that had been massively compromised (by damage to already crushed upper floors) had their few remaining connections destroyed. The columns themselves were almost never overloaded, as proven by the absence of columns with massive plastic strain left in the debris.
5. The specific (& a bit deceptive, on your part) reason that your analysis says that the upper block collapses initially is that you've drawn the bottom "green line" that defines the upper block too low. You've drawn it to encompass the upper block, all of the impact floors, plus (it appears to me) a couple undamaged lower floors for good measure. You should redraw the blocks to define an undamaged upper block, an undamaged lower block and a damaged group of impact floors. If you do it like this, you'll find that the impact floors crush first. The upper block descends because the impact floors crush, the upper floors pack in, and the lower floors start to crush down.
Just about like Bazant's model says. How 'bout that?!
There's lots more that's flawed. That's enough for now.
___
** The source of energy to pulverize the contents and their contribution to slowing the descent of the upper block.
For any piece of the tower that was thrown clear of the footprint, the deformation that occurred when it hit the street (or other object) obviously did NOT contribute to slowing the descent of the upper block.
The energy to pulverize the contents into tiny pieces and dust was provided by the EXCESS potential energy of all the mass above any given piece, less the energy lost to disassembly, PLUS the potential energy of that piece above the ground.
A large portion of the concrete was held within the footprint of the towers by the intertwined rebar and was ground to dust within the churning mass of the crushing tower, thereby contributing to slowing the upper block. A smaller portion of the concrete was thrown clear of the towers and was reduced to dust as it collided with the street.
The bolts and welds were snapped as each floor disassembled, slowing the descent.
Most of the external columns were thrown out of the footprint, and their bending & damage did not contribute to the slowing of the upper block at all.
Almost all of the core beams were contained within the footprint. While the disassembly of the upper core columns may have contributed to the slowing the upper block, the lower 40 stories or so did not, as they were seen still standing in the North Tower.
The grinding into small pieces of the contents of the towers did contribute to slowing the descent of the towers.
tom
Thanks for long post.
Rigid means that it cannot be deformed at all! If it cannot be deformed it cannot fail. If it cannot deform, it apparently can absorb infinite strain energy or none at all. The question abt. where the strain energy goes becomes irrelevant. NIST and Bazant & Co assume that the upper part C is rigid while the lower part A is not. This is the basic error in their calculations and models.
You say:
These are the major errors in constructing your analysis. There are others.
Some examples:
1. "no evidence that the core structure displaced downward". Nonsense. The roof displaced downward. If the core did not, it'd be sticking out of the roof.
2 "no evidence of any simultaneously buckled visible, outside wall columns in the fire zone". Nonsense. Clear, unequivocal video images of massively buckled exterior columns.
3. All of your "rigid body" objections are straw-men arguments, since neither NIST nor Bazant intended them as any more than simplifying approximations. Rigid bodies are NOT required for either NIST's or Bazant's conclusions.
4. No "solid, intact columns below were overloaded by gravity only". Heated (ie., weakened), bent (i.e., unstable) columns buckled and had their connections snapped to initiate the collapse (or crush). After the crush down began, columns that had been massively compromised (by damage to already crushed upper floors) had their few remaining connections destroyed. The columns themselves were almost never overloaded, as proven by the absence of columns with massive plastic strain left in the debris.
5. The specific (& a bit deceptive, on your part) reason that your analysis says that the upper block collapses initially is that you've drawn the bottom "green line" that defines the upper block too low. You've drawn it to encompass the upper block, all of the impact floors, plus (it appears to me) a couple undamaged lower floors for good measure. You should redraw the blocks to define an undamaged upper block, an undamaged lower block and a damaged group of impact floors. If you do it like this, you'll find that the impact floors crush first. The upper block descends because the impact floors crush, the upper floors pack in, and the lower floors start to crush down.
Sorry - if you read my article again and study the photos and links you clearly see that upper part C is destroyed prior to any local failures of lower part A:s upper stories take place. Pls don't call upper part C a block! It is an assembly of strong (columns) and weak (floors) elements full of furniture and plenty of air (>95%). Such a structure, part C, is not rigid and cannot crush anything without getting damaged itself. Compare ship collisions between a small ship C hitting a big ship A of similar structure. You always find C being damaged. You cannot assume that C is rigid and A is not. C may also be driven by a horizontal propulsive force F that may be greater than the one provided by gravity in a vertical collision, so the analogy is very valid. Evidently C must be subject to a force F! Otherwise it cannot collide. To provide that force F energy E is required (F times distance equals E). When E is transformed into heat (friction) and elastic (deformation) and plastic (failures) strain, the destruction is arrested. It always happens in both horizontal and vertical collisions.
Thanks again for your post.
Sorry for not responding to your posts.
Good that you agree that 290 column stub ends will destroy the floors. It is actually 580 column stub ends involved! I broken column = two ends
. The energy required to fracture only one column completely is considerable. Before that happens you have to bend the column so that it kneels, etc. You need energy for that too. So what does these 580 column stub ends then do. Well at least 240 of them will not contact anything for obvious reasons! So they will not get entrapped in anything and will not be subject to any torque, etc.
Of the remaining 340 column stub ends 170 are really awful! They will destroy the upper part C floors! The part C that is rigid according NIST and Bazant & Co and that is not getting damaged. And where does the energy come from that destroys part C? Right, it is provided by part C + gravity.
With these basic observations, you can then start real structural damage analysis.
Let's assume that negligible energy is required to slice apart 14 part C floors and the hat truss on top, what happens then? Well - part C is then sliced into two parts, one of which (two outer walls!) will drop to the ground.
But I can assure you that part C cannot produce so much potential energy that it slices itself into two parts! So what happens then? Right! Part C gets stuck up on top of 170 column stub ends of part A.
Actually, the damaged floors of both parts A and C get entangled into one another - FRICTION develops - and that's it. Destruction is arrested. NIST and Bazant & Co ignores FRICTION.
The 170 column stub ends of part C inside part A will then either rest against floors in part A or nothing - like the other 120 part C column stub ends on the outside of part A.
You see, it is impossible that a part of a structure (part C) can penetrate a bigger part of the same structure (part A) due to gravity alone and at say 0.7 g acceleration, leaving only 0.3 g*m force to plough throw the structure.
I understand why so many real experts in the USA shut up about this obvious fact. They have seen their colleagues being fired from the their jobs and thrown into the street when they point this out. It is like the German Democratic Republic 1949-1989! That's why I like Richard Gage and AE911truth.org so much. They have the guts to point out the obvious without fear. Join them!
Heiwa,
Tell me that you seriously don't believe this nonsense?
Well, apparently you are not sorry enough to exhibit the common courtesy to YET answer any of my questions. I've read your manifesto. I've read dozens of your posts. I recognize that you are the local whipping boy, a title well-earned in my estimation, and you are a bit overwhelmed answering lots of antagonists. But, again, after putting in several hours reading and digesting (no small task, that) your "analysis", I've pointed out numerous errors.
You MIGHT be so kind as to address my points. Instead of producing more smoke & mirrors like this post.
Yes, but - to a close approximation - 1/2 of them are hanging in air & don't contact anything. So you are back down to - exactly as I stated - "290 columns that impact cement."
Please show me any significant percent (say, 30%, 50%, 75%) of "fractured columns" in the debris field. I am NOT talking about twisted end plates or pulled out screw holes. I am talking about truly deformed, i.e., pretzeled or "kneeled" columns. I went thru the hi-resolution images under a microscope, and found EXTREMELY few. The ones I found looked like they were NOT fractured as part of the disassembly, but rather had been mangled in the collapse debris. We are trying to capture the PRINCIPLE failure modes and energy sinks. That means correctly identifying the failure mode: which is NOT fractured columns. It is fractured bolts, sheared & torn welds, and fractured (not pulverized) concrete.
I saw no columns in the towers that showed signs of "kneeling". The only ones that bent & bowed & ultimately became unstable were in the fire zones. And you do NOT have to consider the energy in their bowing in the energy balance, because it happened before the collapse began. (You CAN consider it if you want to complicate your analysis. You do not HAVE to consider it.)
The ones that failed in the crush down did not have a chance to buckle, because their bolts & welds gave way first. They were not sufficiently constrained to buckle. This is UNCONTESTABLE. By the time a beam has truly buckled, it has gone thru massive plastic deformation. There was no massive residual plastic deformations in the columns. (In the trusses, yes.)
OK, you're back down to my "290" approximation. And you may have noticed that the upper block did NOT slide down on linear bearings, missing everything on the way. It was a somewhat chaotic process, and YES, in fact they DID, ultimately, get subjected to torque.
Please explain EXACTLY why the 170 stub ends pointing upwards were "more awful" than the 170 stub ends that were pointing downwards.
Please explain to me why it is that you conclude that if several thousand tons of debris are going to be created on the 85th floor of ANY structure, the SIGNIFICANT damage that you are going to address is to the structure ABOVE that debris? Did no one point out to you in physics class that things have a very strong tendency to fall downwards?
Finally, you were right that the damage goes BOTH upwards & downwards. Bazant & NIST were "more right" in that your objection becomes moot after about 3-5 floors have collapsed, because the upper block ONLY will fill in with debris.
Why is it now that you turn your back on your own correct statement and assert something that is COMPLETELY and utterly wrong: that "the damage ONLY goes upwards". This is ludicrous. It is ludicrous no matter HOW the failure initiates. Thermite, thermate, termite or hack saw. Or damage, heat, creep & unanticipated load condition.
I haven't seen any evidence of it yet.
And you REALLY think that the top portion of the lower block A, with a jagged row of (relatively weak, at that height) vertical columns that has had their supports ripped apart, been bent over, is going to be able to somehow perform this Ginzu slicing & dicing?? And remain intact??
The answer is "Hell, no". You have conveniently (some have suggested "fraudulently") ignored the action of the upper column stubs perforating & destroying the Block A upper floor. This WILL happen, and the upper floor of Block A will NOT survive.
Now what happens?
Utter nonsense.
I FIRMLY believe, although it is just an opinion, that if Block C were displaced to drop on the ground from 10' height, it WOULD disassemble itself. But that is irrelevant.
No, it ONLY gets stuck on top of part A IF AND ONLY IF Part A can survive the collapse of Part C.
Part A cannot. YOU have agreed (and it's true even if you subsequently choose to disagree) that the ONLY portions of Part A & C that need to be destroyed are small sections of the cement floor and a a bunch of small bolts & welds. This takes VERY little energy. As long as these components are destroyed, the top floor disassembles. If it disassembles, it will hold up NOTHING.
They do get entangled. Friction does develop. They become an agglomeration of debris.
And GRAVITY still works. The agglomeration FALLS. Because it is made out of the destroyed components of the ONLY thing that was capable of stopping its fall, the columns & cross trusses.
You fail to acknowledge that the ONLY thing that gives the structure its integrity is the cross trusses & flooring. This keeps the columns in alignment. As soon as those constraints are removed, the columns cannot even hold up their own weight, much less the loads of the rest of the building.
Nonsense.
And this is what has me shaking my head in disbelief.
You are suggesting that a body that is descending at 0.7g can only impress a force of 0.3g*m on any object on which it lands??
Are you suggesting, therefore, that something descending at 1g can only exert 0 lbs force anything on which it lands? That something accelerating downwards at 2g will impart a force of MINUS 1g*m?
Drop a weight onto you bathroom scale. Watch THE TRANSIENT. A 20 pound weight dropped from a height of about 4 feet will exert over 80 pounds on the scale that I probably just ruined. (The stiffer the spring, the higher the peak load.)
This is madness that you say this, and also claim that you are a Mechanical Engineer.
tk
PS. Again, you might actually consider addressing some of the trivial, glaring errors in your "analysis" that I pointed out to you.
Tell me that you seriously don't believe this nonsense?
Well, apparently you are not sorry enough to exhibit the common courtesy to YET answer any of my questions. I've read your manifesto. I've read dozens of your posts. I recognize that you are the local whipping boy, a title well-earned in my estimation, and you are a bit overwhelmed answering lots of antagonists. But, again, after putting in several hours reading and digesting (no small task, that) your "analysis", I've pointed out numerous errors.
You MIGHT be so kind as to address my points. Instead of producing more smoke & mirrors like this post.
Yes, but - to a close approximation - 1/2 of them are hanging in air & don't contact anything. So you are back down to - exactly as I stated - "290 columns that impact cement."
Please show me any significant percent (say, 30%, 50%, 75%) of "fractured columns" in the debris field. I am NOT talking about twisted end plates or pulled out screw holes. I am talking about truly deformed, i.e., pretzeled or "kneeled" columns. I went thru the hi-resolution images under a microscope, and found EXTREMELY few. The ones I found looked like they were NOT fractured as part of the disassembly, but rather had been mangled in the collapse debris. We are trying to capture the PRINCIPLE failure modes and energy sinks. That means correctly identifying the failure mode: which is NOT fractured columns. It is fractured bolts, sheared & torn welds, and fractured (not pulverized) concrete.
I saw no columns in the towers that showed signs of "kneeling". The only ones that bent & bowed & ultimately became unstable were in the fire zones. And you do NOT have to consider the energy in their bowing in the energy balance, because it happened before the collapse began. (You CAN consider it if you want to complicate your analysis. You do not HAVE to consider it.)
The ones that failed in the crush down did not have a chance to buckle, because their bolts & welds gave way first. They were not sufficiently constrained to buckle. This is UNCONTESTABLE. By the time a beam has truly buckled, it has gone thru massive plastic deformation. There was no massive residual plastic deformations in the columns. (In the trusses, yes.)
OK, you're back down to my "290" approximation. And you may have noticed that the upper block did NOT slide down on linear bearings, missing everything on the way. It was a somewhat chaotic process, and YES, in fact they DID, ultimately, get subjected to torque.
Please explain EXACTLY why the 170 stub ends pointing upwards were "more awful" than the 170 stub ends that were pointing downwards.
Please explain to me why it is that you conclude that if several thousand tons of debris are going to be created on the 85th floor of ANY structure, the SIGNIFICANT damage that you are going to address is to the structure ABOVE that debris? Did no one point out to you in physics class that things have a very strong tendency to fall downwards?
Finally, you were right that the damage goes BOTH upwards & downwards. Bazant & NIST were "more right" in that your objection becomes moot after about 3-5 floors have collapsed, because the upper block ONLY will fill in with debris.
Why is it now that you turn your back on your own correct statement and assert something that is COMPLETELY and utterly wrong: that "the damage ONLY goes upwards". This is ludicrous. It is ludicrous no matter HOW the failure initiates. Thermite, thermate, termite or hack saw. Or damage, heat, creep & unanticipated load condition.
I haven't seen any evidence of it yet.
And you REALLY think that the top portion of the lower block A, with a jagged row of (relatively weak, at that height) vertical columns that has had their supports ripped apart, been bent over, is going to be able to somehow perform this Ginzu slicing & dicing?? And remain intact??
The answer is "Hell, no". You have conveniently (some have suggested "fraudulently") ignored the action of the upper column stubs perforating & destroying the Block A upper floor. This WILL happen, and the upper floor of Block A will NOT survive.
Now what happens?
Utter nonsense.
I FIRMLY believe, although it is just an opinion, that if Block C were displaced to drop on the ground from 10' height, it WOULD disassemble itself. But that is irrelevant.
No, it ONLY gets stuck on top of part A IF AND ONLY IF Part A can survive the collapse of Part C.
Part A cannot. YOU have agreed (and it's true even if you subsequently choose to disagree) that the ONLY portions of Part A & C that need to be destroyed are small sections of the cement floor and a a bunch of small bolts & welds. This takes VERY little energy. As long as these components are destroyed, the top floor disassembles. If it disassembles, it will hold up NOTHING.
They do get entangled. Friction does develop. They become an agglomeration of debris.
And GRAVITY still works. The agglomeration FALLS. Because it is made out of the destroyed components of the ONLY thing that was capable of stopping its fall, the columns & cross trusses.
You fail to acknowledge that the ONLY thing that gives the structure its integrity is the cross trusses & flooring. This keeps the columns in alignment. As soon as those constraints are removed, the columns cannot even hold up their own weight, much less the loads of the rest of the building.
Nonsense.
And this is what has me shaking my head in disbelief.
You are suggesting that a body that is descending at 0.7g can only impress a force of 0.3g*m on any object on which it lands??
Edited by Tricky:
Edited for civility
Are you suggesting, therefore, that something descending at 1g can only exert 0 lbs force anything on which it lands? That something accelerating downwards at 2g will impart a force of MINUS 1g*m?
Drop a weight onto you bathroom scale. Watch THE TRANSIENT. A 20 pound weight dropped from a height of about 4 feet will exert over 80 pounds on the scale that I probably just ruined. (The stiffer the spring, the higher the peak load.)
This is madness that you say this, and also claim that you are a Mechanical Engineer.
Edited by Tricky:
Edited for civility. To summarize, tfk is unimpressed.
tk
PS. Again, you might actually consider addressing some of the trivial, glaring errors in your "analysis" that I pointed out to you.
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Gravy
Downsitting Citizen
- Joined
- Mar 27, 2006
- Messages
- 17,078
Bolding mine.
We know your opinions. Now show that you're capable of "real structural damage analysis" and present your math. We're still waiting, engineer.
We know your opinions. Now show that you're capable of "real structural damage analysis" and present your math. We're still waiting, engineer.
The 170 stub ends pointing upwards of part A evidently contact the lowest floor of upper part C that is supposed to drop down and crush lower part A.
What happens is that it is part C that is being crushed by these awful stub ends and not part A.
According NIST and Bazant & Co it should be the opposite!
I thought that would be pretty clear!
Reason why a thin, weak, concrete floor of upper part C is not damaged by 170 stub steel column ends of part A is that NIST and Bazant & Co assume that the floor is rigid, i.e. cannot be deformed, and that the stub end are weak. Under such outrageous assumptions evidently the thin floor may destroy the columns below or would get stuck on top but the floor can never get damaged.
I just suggest the opposite. The part C floor gets damaged and then the next part C floor, etc, etc, until part C is sliced in two unless the destruction is arrested.
If you agree with that you understand that there are no other errors in the article. Thanks for your comments.
No, it is Newton that suggests that - but only during free fall. An object with mass m is always subject to gravity force F = m*g, as you know.
If you drop this mass m, F ensures that m accelerates with g. If, when dropping, you apply a force -F = 0.3m*g on this mass (air resistance?) then the mass accelerates only with 0.7g. It goes faster and faster but not so fast as with g. Do not ask me about -F! It is quite tricky to apply a constant force on an object that is dropping faster and faster.
It is quite elementary.
When object m lands or contacts ground, you have to establish the speed v it has, or rather its energy E = mv²/2 . This energy E will produce a dynamic contact force G applied m/ground and ground/m. G depends on how m and ground deforms. If total deformation is d, average G is something like E/d .
If m is a rubber ball, it may bounce on the ground! All explained at http://heiwaco.tripod.com/nist3.htm .
Pls read my article before asking questions.
Heiwa,
Your definition of "rigid" is false. You've been told this several times. Engineers use the term to mean that it moves as a single piece. It does NOT mean that it is indestructible or undeformable.
"It cannot deform, it apparently can absorb infinite strain energy or none at all"...??? You don't know the right answer to this for an undeformable object??
And you call yourself a mechanical engineer?? Big hint. It AIN'T "infinite strain energy".
Nonsense. Your article is so full of errors that it is worse than meaningless.
You have artificially included the entire impact & fire zone with the upper part A. THIS is exactly what causes the initial collapse to be in YOUR definition of the upper part.
This is a GROSS error. If you'd included the impact & fire zone with the lower part C, then THAT part would have been first to collapse.
BOTH of these approaches are completely wrong. The impact & fire zone should be it's OWN section, because its properties are unlike either the upper or lower parts.
Your claim that the entire upper block is destroyed before the lower section begins to collapse is unsupported by any video evidence. The only thing visible is the top of the tower descending into an impenetrable cloud of debris. This does NOT support you contention.
Well, "Duh".
You seem to make a habit of focusing on trivial semantics ("collapse" vs. "crush", "part" vs. "block"), while remaining conveniently mute on substantive issues.
Is there any particular reason for this?
Nope. In order for this discussion to be meaningful in the slightest, the damage area MUST be defined as its own part (Part D). The crush does NOT happen in either Part A OR in Part C. It happens in Part D. This is not trivial or capricious.
Part D constitutes about 6 - 8 stories, the part with physical and fire damage. After Part D has collapsed (or crushed), then Part C begins to cruse. NOT Part A.
A vertical collapse and your ocean collision have some elements in common. And some are completely different.
In this case, they are completely different. GRAVITY makes the damage to Part A & Part C asymmetric. Part A packs in with debris and the bottom becomes almost solid, while the top floor of Part C always remains an open structure. This fact, along with the effects outlined by Bazant in the reference below, causes Part C to be destroyed.
NOBODY is doing this except for you. There are specific reasons - NOT based on arbitrary assumption - that, AFTER a couple of floors of crush, part C is damaged and part A is not. I've already explained one important reason - Debris pack-in.
Here is Bazant explaining another. Try to follow along and learn something from someone who knows a BOATLOAD more about structural mechanics than you do.
http://www.civil.northwestern.edu/people/bazant/PDFs/Papers/D25 WTC Discussions Replies.pdf
Read the discussion on page 917, entitled "Can Crush-Up Proceed Simultaneously with Crush Down?"
As soon as you get the WEIGHT vector for ALL components & debris to act horizontally, then you have a chance to generate a similarity between these systems. I wouldn't count on your ability to do so, at this point.
Well, let's see how many undergraduate level mistakes you make in this paragraph, shall we?
1. Reversed cause & effect. The forces that are generated in Part C (& A & B & D) are all A RESULT of the collision. Not the cause of it.
2. The forces are generated as a result of both gravity and the inertial of the colliding bodies.
3. The energy dissipated is the result of the deformations and destruction in the colliding components.
4. In mechanical engineering, elastic strain is NOT defined as deformation.
5. In mechanical engineering, plastic strain is NOT defined as failure.
6. The destruction is not arrested.
7. The destruction does not necessarily arrest. In either horizontal or vertical collisions.
Seven errors in one paragraph. On a topic that you've been thinking about & discussing for extended periods of time. That's not very good for someone who claims to be a professional.
Now say it like you mean it.
While you're at it, in my LOOOOOONG post to you, I pointed out approximately 15 fundamental flaws in your assertions. You have ignored each and every correction. And simply repeated the inane "read my (massively flawed) paper".
Less than technically impressive.
tom
Your definition of "rigid" is false. You've been told this several times. Engineers use the term to mean that it moves as a single piece. It does NOT mean that it is indestructible or undeformable.
"It cannot deform, it apparently can absorb infinite strain energy or none at all"...??? You don't know the right answer to this for an undeformable object??
And you call yourself a mechanical engineer?? Big hint. It AIN'T "infinite strain energy".
tomk said:
Nonsense. Your article is so full of errors that it is worse than meaningless.
You have artificially included the entire impact & fire zone with the upper part A. THIS is exactly what causes the initial collapse to be in YOUR definition of the upper part.
This is a GROSS error. If you'd included the impact & fire zone with the lower part C, then THAT part would have been first to collapse.
BOTH of these approaches are completely wrong. The impact & fire zone should be it's OWN section, because its properties are unlike either the upper or lower parts.
Your claim that the entire upper block is destroyed before the lower section begins to collapse is unsupported by any video evidence. The only thing visible is the top of the tower descending into an impenetrable cloud of debris. This does NOT support you contention.
Well, "Duh".
You seem to make a habit of focusing on trivial semantics ("collapse" vs. "crush", "part" vs. "block"), while remaining conveniently mute on substantive issues.
Is there any particular reason for this?
Nope. In order for this discussion to be meaningful in the slightest, the damage area MUST be defined as its own part (Part D). The crush does NOT happen in either Part A OR in Part C. It happens in Part D. This is not trivial or capricious.
Part D constitutes about 6 - 8 stories, the part with physical and fire damage. After Part D has collapsed (or crushed), then Part C begins to cruse. NOT Part A.
A vertical collapse and your ocean collision have some elements in common. And some are completely different.
In this case, they are completely different. GRAVITY makes the damage to Part A & Part C asymmetric. Part A packs in with debris and the bottom becomes almost solid, while the top floor of Part C always remains an open structure. This fact, along with the effects outlined by Bazant in the reference below, causes Part C to be destroyed.
NOBODY is doing this except for you. There are specific reasons - NOT based on arbitrary assumption - that, AFTER a couple of floors of crush, part C is damaged and part A is not. I've already explained one important reason - Debris pack-in.
Here is Bazant explaining another. Try to follow along and learn something from someone who knows a BOATLOAD more about structural mechanics than you do.
http://www.civil.northwestern.edu/people/bazant/PDFs/Papers/D25 WTC Discussions Replies.pdf
Read the discussion on page 917, entitled "Can Crush-Up Proceed Simultaneously with Crush Down?"
As soon as you get the WEIGHT vector for ALL components & debris to act horizontally, then you have a chance to generate a similarity between these systems. I wouldn't count on your ability to do so, at this point.
Well, let's see how many undergraduate level mistakes you make in this paragraph, shall we?
1. Reversed cause & effect. The forces that are generated in Part C (& A & B & D) are all A RESULT of the collision. Not the cause of it.
2. The forces are generated as a result of both gravity and the inertial of the colliding bodies.
3. The energy dissipated is the result of the deformations and destruction in the colliding components.
4. In mechanical engineering, elastic strain is NOT defined as deformation.
5. In mechanical engineering, plastic strain is NOT defined as failure.
6. The destruction is not arrested.
7. The destruction does not necessarily arrest. In either horizontal or vertical collisions.
Seven errors in one paragraph. On a topic that you've been thinking about & discussing for extended periods of time. That's not very good for someone who claims to be a professional.
Now say it like you mean it.
While you're at it, in my LOOOOOONG post to you, I pointed out approximately 15 fundamental flaws in your assertions. You have ignored each and every correction. And simply repeated the inane "read my (massively flawed) paper".
Less than technically impressive.
tom
Heiwa,
The force balances "when falling" are relatively inconsequential. The force balances during collisions is important.
In dynamic collisions, the force imparted from a falling object onto the object onto which it falls can far exceed the falling object's weight.
Or do you REALLY believe that if you jump onto your bathroom scale, it will not produce a transient load that if far greater than the ultimate static reading?
It ain't that hard at all. Retro rockets seem to do the job just fine.
Yes, it is quite elementary. It's rather surprising that, after a dozen people have explained it to you, you still don't seem to understand it.
It appears that you don't understand the difference between average and instantaneous forces.
It appears that your understanding of engineering mechanics stops with statics. You show no appreciation of that whole other field called "dynamics".
If one of my engineering students had been unable to master these concepts, I would have recommended a change in major.
Yeah, but the maximum resisting force and the maximum strain energy that any object can sustain without failing is limited by its materials and shape. If those quantities are exceeded by the max force generated in the collision and kinetic energy of the falling object, then the call will NOT be halted.
I don't need to read your article or ask you questions to learn any of this.
I learned it when I got my degree. I've used it for almost 35 years. I've taught Engineering Dynamics to university level engineering students.
And I can tell you that your analysis is rife with fundamental errors. I put in a fair amount of time listing about 15 of them. You've replied to virtually none of my comments.
Not particularly neighborly.
tk
The force balances "when falling" are relatively inconsequential. The force balances during collisions is important.
In dynamic collisions, the force imparted from a falling object onto the object onto which it falls can far exceed the falling object's weight.
Or do you REALLY believe that if you jump onto your bathroom scale, it will not produce a transient load that if far greater than the ultimate static reading?
It ain't that hard at all. Retro rockets seem to do the job just fine.
Yes, it is quite elementary. It's rather surprising that, after a dozen people have explained it to you, you still don't seem to understand it.
It appears that you don't understand the difference between average and instantaneous forces.
It appears that your understanding of engineering mechanics stops with statics. You show no appreciation of that whole other field called "dynamics".
If one of my engineering students had been unable to master these concepts, I would have recommended a change in major.
Yeah, but the maximum resisting force and the maximum strain energy that any object can sustain without failing is limited by its materials and shape. If those quantities are exceeded by the max force generated in the collision and kinetic energy of the falling object, then the call will NOT be halted.
I don't need to read your article or ask you questions to learn any of this.
I learned it when I got my degree. I've used it for almost 35 years. I've taught Engineering Dynamics to university level engineering students.
And I can tell you that your analysis is rife with fundamental errors. I put in a fair amount of time listing about 15 of them. You've replied to virtually none of my comments.
Not particularly neighborly.
tk
Re 'dynamic collisions' (sic) - yes, the force applied exceeds the weight of the falling object. It is clear from my article. That's why rubber balls bounces, etc. I remind the readers about it in the introduction of my paper.
Engineering Dynamics is probably a fascinating subject but has little in common with structural damage analysis.
I always attend to comments about errors in my observations/papers as long as they are presented politely (of course) and with a logical explanation. You fail in both respects.
twinstead
Penultimate Amazing
- Joined
- Apr 8, 2005
- Messages
- 12,374
You do NO such thing. You tend to totally ignore ANY comments about errors in your observations/papers, whether they are presented politely and with a logical explanation or not. Do you not think we have been reading your posts for the last few months?
peteweaver
Graduate Poster
- Joined
- Mar 1, 2007
- Messages
- 1,006
The twin towers were designed to bend in the wind, they were NOT "rigid".
Furthermore they were built from the same things electric guitar strings are made from: steel, which is maleable and ductile.
Steel can bend stretch sag and snap.
Want to see some proof that steel is not rigid ? Listen to Eric Clapton's solo on the song "White Room"...
SteveAustin
Critical Thinker
- Joined
- Mar 3, 2009
- Messages
- 494
Hmmm well, are you talking about this video http://www.911research.com/wtc/evidence/videos/docs/north_tower_collapse.mpeg ?
I can't post links yet so I hope this partial gets through. Just add the www
I look at that video and it is quite clear that the top portion turns nearly completely to dust before the bottom section begins to falls.
You can also view multiple frames from that video here http://911research.wtc7.net/wtc/evidence/videos/north_tower.html (no www in this one just the http )
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Heiwa,
It's not "dynamic collisions". ALL collisions are, by definition, dynamic processes.
It is the "dynamic forces" that arise during collisions. That is, the transient forces that are, for any collapsing building, typically far greater than the static forces.
Just as soon as the upper portion of the building starts to descent, the entire system becomes a dynamic, not a static, problem. As a direct result, a static analysis will fail to capture the MOST important features.
A correct damage analysis will recognize, acknowledge and account for all the important effects. One that ignores the most important features is doomed to failure.
Good. There are about 20 errors that I listed when I was still being polite to you. How about addressing those points?
BTW, "polite" is a concern for the academics, Topix administrators and wimps overly concerned with their "self esteem".
Real engineers have neither the time, the disposition nor the inclination for "polite". Especially when dealing with the resolutely, determinedly foolish. We are generally blunt & care about one thing only - the correct answer.
You should try it some time.
tk
It's not "dynamic collisions". ALL collisions are, by definition, dynamic processes.
It is the "dynamic forces" that arise during collisions. That is, the transient forces that are, for any collapsing building, typically far greater than the static forces.
Just as soon as the upper portion of the building starts to descent, the entire system becomes a dynamic, not a static, problem. As a direct result, a static analysis will fail to capture the MOST important features.
A correct damage analysis will recognize, acknowledge and account for all the important effects. One that ignores the most important features is doomed to failure.
Good. There are about 20 errors that I listed when I was still being polite to you. How about addressing those points?
BTW, "polite" is a concern for the academics, Topix administrators and wimps overly concerned with their "self esteem".
Real engineers have neither the time, the disposition nor the inclination for "polite". Especially when dealing with the resolutely, determinedly foolish. We are generally blunt & care about one thing only - the correct answer.
You should try it some time.
tk
A
Thanks for polite comments. Re 20 errors, I do not agree with you, particularly your 6. The destruction is not arrested.
Apparently you have not tried to drop a part C of a structure A on itself or even done the basic calculations of such event. The energy applied by C at collision contact is evidently also absorbed by part C! Compare two cars colliding. NIST, Bazant & Co and other fools assume (sic) that part C is rigid and remains undamaged during crush down.
Even worse, no upper part C ever collided with lower part A at WTC 1 on 9/11. Part C was destroyed prior to that. Just watch the videos ... and read my papers again. And join AE911truth.org .
Thanks for polite comments. Re 20 errors, I do not agree with you, particularly your 6. The destruction is not arrested.
Apparently you have not tried to drop a part C of a structure A on itself or even done the basic calculations of such event. The energy applied by C at collision contact is evidently also absorbed by part C! Compare two cars colliding. NIST, Bazant & Co and other fools assume (sic) that part C is rigid and remains undamaged during crush down.
Even worse, no upper part C ever collided with lower part A at WTC 1 on 9/11. Part C was destroyed prior to that. Just watch the videos ... and read my papers again. And join AE911truth.org .
Steve,
Thanks for that 911research link. I was looking for that.
And I disagree with you.
If you divide up the building like Heiwa did (putting the damaged 8 floors into the top section, Part C), then I can see where it appears as you describe.
Of course, if you divide up the building putting the damaged 8 floors into the bottom section (Part A), then it appears that the bottom section collapses first.
BOTH of these are erroneous, of course.
The damaged 8 floors need to be considered their own section (call it Part D), because the weakened properties of its supports are different than either Parts A or C. Once you do this, and look at the collapse carefully, you find that Part D is the first part to collapse. And BOTH Parts A & C remain undamaged as Part D crushes down.
Further you will see that just as Part A reaches the bottom of Part D, it is obscured by the dust & debris cloud. So, from this view, it becomes impossible to tell which (A or C) begins to crush first at this point. I am quite sure that it is Part A (the bottom) that should, and did, crush first. Heiwa is equally certain that Part C should have crushed first. You'll have to ask him which he thinks DID crush first, and why.
tom
Thanks for that 911research link. I was looking for that.
And I disagree with you.
If you divide up the building like Heiwa did (putting the damaged 8 floors into the top section, Part C), then I can see where it appears as you describe.
Of course, if you divide up the building putting the damaged 8 floors into the bottom section (Part A), then it appears that the bottom section collapses first.
BOTH of these are erroneous, of course.
The damaged 8 floors need to be considered their own section (call it Part D), because the weakened properties of its supports are different than either Parts A or C. Once you do this, and look at the collapse carefully, you find that Part D is the first part to collapse. And BOTH Parts A & C remain undamaged as Part D crushes down.
Further you will see that just as Part A reaches the bottom of Part D, it is obscured by the dust & debris cloud. So, from this view, it becomes impossible to tell which (A or C) begins to crush first at this point. I am quite sure that it is Part A (the bottom) that should, and did, crush first. Heiwa is equally certain that Part C should have crushed first. You'll have to ask him which he thinks DID crush first, and why.
tom
SteveAustin
Critical Thinker
- Joined
- Mar 3, 2009
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Thanks for that reply Tom.
So from what you are saying that means that the top portion that fell and caused all that destruction on the lower 96 floors was only 8 floors then, since the 8 floors in-between were the damaged floors that got "crushed" in the beginning.
So how does that jive with the NIST theory? Does the NIST "FINAL" report say it was only 8 floors that crushed the bottom 96 floors? Or does NIST claim it was 16 floors (which according to your theory Tom would be erroneous) that crushed the bottom 96 floors?
Is there enough "energy" in just those 8 floors to do the trick?
So from what you are saying that means that the top portion that fell and caused all that destruction on the lower 96 floors was only 8 floors then, since the 8 floors in-between were the damaged floors that got "crushed" in the beginning.
So how does that jive with the NIST theory? Does the NIST "FINAL" report say it was only 8 floors that crushed the bottom 96 floors? Or does NIST claim it was 16 floors (which according to your theory Tom would be erroneous) that crushed the bottom 96 floors?
Is there enough "energy" in just those 8 floors to do the trick?
Heiwa,
It is neither clear nor correct.
I have mentioned to you at least 4 times now that your model is flawed. In many ways.
But the most important way is to NOT represent the damaged & weakened 6 - 8 stories. You erroneously include them into the top section, part C. And then you claim that the collapse occurs with the telescoping of Part C. This is correct, but it a meaningless artifact of your erroneous model.
If I were to simply redefine the parts to include the damaged stories in Part A, then the initial telescoping would occur in Part A. And this would be equally meaningless.
Refer to the damaged, uncollapsed section as Part D. Once any floor has collapsed, then it becomes Part B, the collapsed rubble.
The initial collapse does not happen in parts A or B. It happens in the middle of Part D, centered around floor 95. But, because the core & peripheral columns were 3 stories high, the immediately damaged floors extended from the 93rd to the 97th. Virtually all of the columns on the 95th floor were destroyed, as were about 2/3rds the columns on the 94th & 96th floors, as well as about 1/3rd the columns on the 93rd & 97th floors.
Approximately half of the peripheral columns get thrown clear of the building. So the real number is far less than the 240 (peripheral) and 47 core columns. It's most likely something like 100 peripheral (50 sticking up & 50 sticking down) and about 46 of the core (23 up & 23 down).
Neither NIST nor Bazant assume that the top section, C, is undamaged or cannot be deformed. This is not what the mechanical term "rigid body" means. If that were the assumption, then Part C would be sitting on top of a rubble pile at the end of the collapse.
BTW, Bazant (2007) includes crush down to upper section.
http://www.civil.northwestern.edu/p...TC Collapse - What Did & Did Not Cause It.pdf
Yeah, I've noticed. And your unsupported "suggestion" is ludicrous.
Specifically, Part C never touches Part A. It is always separated by either Part B (later in the collapse) or Part D (the uncollapsed part that you omit from your analysis) early in the collapse.
It is also absurd to suggest that the fractured, unsupported, stub ends of the columns sticking up from Part A could survive the impact of Part C.
Your assertions are silly. You haven't even bothered to try to defend them.
Your article is rife with errors.
tom
It is neither clear nor correct.
I have mentioned to you at least 4 times now that your model is flawed. In many ways.
But the most important way is to NOT represent the damaged & weakened 6 - 8 stories. You erroneously include them into the top section, part C. And then you claim that the collapse occurs with the telescoping of Part C. This is correct, but it a meaningless artifact of your erroneous model.
If I were to simply redefine the parts to include the damaged stories in Part A, then the initial telescoping would occur in Part A. And this would be equally meaningless.
Refer to the damaged, uncollapsed section as Part D. Once any floor has collapsed, then it becomes Part B, the collapsed rubble.
The initial collapse does not happen in parts A or B. It happens in the middle of Part D, centered around floor 95. But, because the core & peripheral columns were 3 stories high, the immediately damaged floors extended from the 93rd to the 97th. Virtually all of the columns on the 95th floor were destroyed, as were about 2/3rds the columns on the 94th & 96th floors, as well as about 1/3rd the columns on the 93rd & 97th floors.
Approximately half of the peripheral columns get thrown clear of the building. So the real number is far less than the 240 (peripheral) and 47 core columns. It's most likely something like 100 peripheral (50 sticking up & 50 sticking down) and about 46 of the core (23 up & 23 down).
Neither NIST nor Bazant assume that the top section, C, is undamaged or cannot be deformed. This is not what the mechanical term "rigid body" means. If that were the assumption, then Part C would be sitting on top of a rubble pile at the end of the collapse.
BTW, Bazant (2007) includes crush down to upper section.
http://www.civil.northwestern.edu/p...TC Collapse - What Did & Did Not Cause It.pdf
Yeah, I've noticed. And your unsupported "suggestion" is ludicrous.
Specifically, Part C never touches Part A. It is always separated by either Part B (later in the collapse) or Part D (the uncollapsed part that you omit from your analysis) early in the collapse.
It is also absurd to suggest that the fractured, unsupported, stub ends of the columns sticking up from Part A could survive the impact of Part C.
Your assertions are silly. You haven't even bothered to try to defend them.
Your article is rife with errors.
tom