The influence of buckling

[rwguinn]

All I can suggest is that you read what I wrote over again.

I cannot take responsibility for your errant response but I will accept your apology for calling me ignorant when you have fully read my post.

I have read your post. As for an apology,now, There's something that ain't gonna happen.

 

[William Rea]

I have read your post. As for an apology,now, There's something that ain't gonna happen.

Yeah, I kind of figured you wouldn't have the class required to do an apology.

 

[rwguinn]

Yeah, I kind of figured you wouldn't have the class required to do an apology.

Wrong again.
You jst need to repeal all the rules of material science, substitute your own.
Being right would be helpful.

 

[William Rea]

Wrong again.
You jst need to repeal all the rules of material science, substitute your own.
Being right would be helpful.

Tell me which ones I have got wrong? I'm sure that when you really thoroughly read it through a light will come on somewhere.

Hint - You might want to read back through to the post I was answering.

 

[The Almond]

Tell me which ones I have got wrong? I'm sure that when you really thoroughly read it through a light will come on somewhere.

Hint - You might want to read back through to the post I was answering.

It's pretty clear to me what rwguinn was saying. Your first post implied that a moment was being applied at a pin connection. Now, if that's not what you intended to say, that's fine, correct it. Clearly, however, pin connections do not transmit moments, only x and y forces.

 

[William Rea]

William, are you suggesting that the WTC buildings may have been strengthened by the fires in them? If so, that's certainly a novel argument and I'd appreciate it if you could expand on it for a layman like me. And if you could explain how the top floors of the towers could have "toppled," that would be great.

No, I suggest you look up the terms strength and toughness in the engineering sense along with ductility if you want to understand what I said.

I have explained how the toppling is feasible in previous threads.

 

[William Rea]

It's pretty clear to me what rwguinn was saying. Your first post implied that a moment was being applied at a pin connection. Now, if that's not what you intended to say, that's fine, correct it. Clearly, however, pin connections do not transmit moments, only x and y forces.

Read it again. I'll quote you back what I said with some highlights to show you...

"And what you fail to point out is that Euler applies to slender columns where the length is a minimum of 30 times the width and no bending moments are applied at the joints. Where moments are applied at the pin joints (the columns are restrained at each end) the critical load rises by a factor of 4. For shorter columns P crit becomes so insignificant that they are more likely to fail in compression."

I think it speaks for itself when you read it with an open mind.

Enough distractions now?

 

[The Almond]

No, I suggest you look up the terms strength and toughness in the engineering sense along with ductility if you want to understand what I said.

Umm, pardon me for implying this, but this is a rather dishonest troll tactic. If you're not willing to define terms or provide more expanded explanations of your ideas, then how do you expect to engage anyone enough to do this research? If Gravy's analysis of your claim is wrong, explain why and provide a clear definition of terms. The contradictory "you just didn't understand me" is a rather childish form of debate.

 

[William Rea]

Umm, pardon me for implying this, but this is a rather dishonest troll tactic. If you're not willing to define terms or provide more expanded explanations of your ideas, then how do you expect to engage anyone enough to do this research? If Gravy's analysis of your claim is wrong, explain why and provide a clear definition of terms. The contradictory "you just didn't understand me" is a rather childish form of debate.

Ok so now it's dishonest and trolling to expect people to understand fairly basic engineering terms when discussing engineering structures but on the other hand it's acceptable for every idiot to come in and attack basic engineering principles that I put forward and then expect me to educate them! I love that.

I suggest you readjust your focus and withdraw the trolling accusation however cleverly cloaked you made it.

 

[The Almond]

Read it again. I'll quote you back what I said with some highlights to show you...

"And what you fail to point out is that Euler applies to slender columns where the length is a minimum of 30 times the width and no bending moments are applied at the joints. Where moments are applied at the pin joints (the columns are restrained at each end) the critical load rises by a factor of 4. For shorter columns P crit becomes so insignificant that they are more likely to fail in compression."

Your bolded part is exactly where the objection comes from. Moments can't be applied at pin joints. If the columns are restrained at each end, the moments are there. If you mean that the moments are applied infinitesimally close to the pin joint, then the positive moment will be applied to one side of the restraint and the negative moment will be applied to the other. This method of sectioning is commonly employed to solve indeterminate structures.

If, on the other hand, you mean that the column is restrained at both ends and a moment is applied at the center of the column, then that would certainly break no mechanical terminologies. It's simply a matter of expanding your explanation. Commonly, a joint implies that two pieces of, in this instance, steel are joined together. For simply supported beams, the end members are commonly called a pin connectors, not joints. It's also helpful to note that one of the end members is actually a wheel connector, not a pin.

I think it speaks for itself when you read it with an open mind.

Implying that close-mindedness is at issue is fallacious. Semantics, terminologies and the inherent weaknesses to text based debate are at issue.

Enough distractions now?

Distraction is not an issue when defining terms and analyses. If you wish to conduct a meaningful debate, this exchange is a necessary part of that.

 

[rwguinn]

No, I suggest you look up the terms strength and toughness in the engineering sense along with ductility if you want to understand what I said.

I have explained how the toppling is feasible in previous threads.

and I submit to you that toughness is a non-sequiter in the case of the towers collapse.
Certainly, you can bend steel a heckofa long way by local heating--any amateur blacksmith can tell you that. They will also tell you that it is easier to bend heatedmetal--a reduction in Young's Modulus. It also follows that if F remains constant, a reduction in Young's Modulus means it bends faster, and when a longitudinal load is also applied (like collumns holding up a building), the element (collumn) becomes well-nigh useless--and the load transfers to somewhere else, via a load path which was not designed to take that particular load, in that particular direction.

Yep, the top floors "toppled". More correctly, they rotated. The CG of those floors moved laterally between 6 and 12 feet before the bending moment in the hinge side of the building failed those collumns , and since the top floor's rotation had very little time to build up angular velocity, and since the failure would also cause an opposite rotation--about the laterally-displaced CG --the building came pretty much straight down

Any more "questions"?

 

[The Almond]

Ok so now it's dishonest and trolling to expect people to understand fairly basic engineering terms when discussing engineering structures

If you wish to discuss the basics of structural analysis, I suggest doing it at a professional convention or in an academic setting. This forum, like most others, is primarily staffed by the laity. It is not unreasonable, therefore, for someone in the laity to request a full and honest disclosure of terms and principles from an educated engineer. I would refer you to the ASCE's code of ethics for the factual and honest dissemination of knowledge from the engineering community to the laity.

but on the other hand it's acceptable for every idiot

Appeal to intelligence

to come in and attack basic engineering principles that I put forward and then expect me to educate them! I love that.

Perhaps you are unfamiliar with the nature of the James Randi Educational Foundation. It is absolutely acceptable for each member of this forum to expect you to educate them on basic engineering principles. If you find this part of the organization's mission unacceptable, you are free to leave.

I suggest you readjust your focus and withdraw the trolling accusation however cleverly cloaked you made it.

Suggestion noted and declined. I have noticed trolling behavior and made a full and honest accusation against its institution, not against you. Please refer to the forum rules regarding name calling and civil debate for further discussion.

 

[Darth Rotor]

a) the eccentric loading from the non-uniform damage across the floors (which should have resulted in the floors above the damage toppling off) and

You don't support this statement.

I fear that you are modeling the entire tower as a single column with a heavy load attached at the top (mushroom), when the model and method used to construct WTC 1 and WTC 2 was a three dimensional lattice. NIST describes the benefits of this design as allowing for more rentable area (fewer required vertical members) as it distributed about a fifth of the load bearing into the floor supports.

Except in the set of floors (from the pictures, it appeared to my eye that between three and six floors were directly influenced by the impact) where impact occurred, load distribution could be expected to perform as designed. In the damaged floors, loads were still distributed horizontally somewhat, though in a degraded lattice, which led to floor sag, failures, and some photographs indicate the internal buckling of vertical members associated with the forces from the floor.

For the top to fall off or topple, a significant number of vertical members would have to fail under tension, not in torsion. It doesn't appear that the loads (based on the tilt angles I have seen in various photographs) in the upward direction were sufficient to cause this mass failure (partly due to load distribution via the lattice) before the sag and buckling combination induced the failure in torsion and compression, leading to the "buckling" failure referred to in the OP.

For simplicity, it might be more productive to argue material science in one point, and separately describe why the toppling "should" have occurred.

DR

 

[William Rea]

Your bolded part is exactly where the objection comes from. Moments can't be applied at pin joints. If the columns are restrained at each end, the moments are there. If you mean that the moments are applied infinitesimally close to the pin joint, then the positive moment will be applied to one side of the restraint and the negative moment will be applied to the other. This method of sectioning is commonly employed to solve indeterminate structures.

If, on the other hand, you mean that the column is restrained at both ends and a moment is applied at the center of the column, then that would certainly break no mechanical terminologies. It's simply a matter of expanding your explanation. Commonly, a joint implies that two pieces of, in this instance, steel are joined together. For simply supported beams, the end members are commonly called a pin connectors, not joints. It's also helpful to note that one of the end members is actually a wheel connector, not a pin.

Implying that close-mindedness is at issue is fallacious. Semantics, terminologies and the inherent weaknesses to text based debate are at issue.

Distraction is not an issue when defining terms and analyses. If you wish to conduct a meaningful debate, this exchange is a necessary part of that.

I couldn't be sure but I was pretty certain that this thread would probably end up somewhere abouts in this zone when I first posted in it. It kind of proves to me what I have come to realise which is that this forum is more about politics than it is about truth.

I'll cite that not a single one of you asked Chippy to qualify any of his opening post because it agreed with your worldview. When someone doesn't agree with your worldview the pack of baboons races in and destroys the thread with inane interjections on topics they simply will never have the intelligence or education to grasp.

It explains to me why Christophera has been under constant hammering by you clowns.

Thanks for the entertainment.

 

[mcMike]

Design vs. yield strength is different, of course. The WTC core columns were apparently overdesigned by a factor of 1.67 (from F.R. Greening's letter "To Whom it May Concern", page 11, in the {ahem} Journal of 9/11 Studies, Sept. 2006), slightly higher than the typical 50% safety factor but still pretty average.

I would like to emphasise this point since in so many places the safety factor is mentioned all the way up to 6. Here's direct reference:

[ Federal Building and Fire Safety Investigation of the World Trade Center Disaster ]
Part III – Baseline Performance, April 5, 2005

"The allowable stress design method has an inherent factor of safety for structural components. For example, the safety factor for yielding and buckling is:

• 1.67 and 1.92 for core columns in the original design and SOP cases, and for all columns in refined NIST estimate case.
• 1.26 and 1.44 for perimeter columns in the original design and SOP case (discounting the 1/3 increase in allowable stress under wind loads).

Source: http://wtc.nist.gov/pubs/WTCPart III - Baseline Final.pdf (p. 35)

And the very same code in Canada:

[ Safety Factors in the National Building Code of Canada 1970 ]
Type of construction Basic Safety Factor Steel and Aluminum
Yield or plastic resistance 1.67
Elastic Buckling 1.92
Source: http://irc.nrc-cnrc.gc.ca/pubs/cbd/cbd147_e.html

Our "own" (in)famous Prof. Heikki Kurttila uses factor of 6 in his calculations to prove that the progressive collapse was impossible.

 

[The Almond]

I couldn't be sure but I was pretty certain that this thread would probably end up somewhere abouts in this zone when I first posted in it.

What zone is this?

It kind of proves to me what I have come to realise which is that this forum is more about politics than it is about truth.

Oh? How does one go about producing the truth? Does one ask for clarifications, explanations and definitions, or does one make pronouncements based entirely on strength of expertise and expect everyone to agree?

I'll cite that not a single one of you asked Chippy to qualify any of his opening post because it agreed with your worldview.

What does Euler's equation have to do with world view? He made an argument based on his understanding of Euler's equation. If you're going to challenge it, great, do so. Chippy is an ME student, and I'm certain he'd be more than happy to discuss the issue with you.

When someone doesn't agree with your worldview the pack of baboons races in and destroys the thread with inane interjections on topics they simply will never have the intelligence or education to grasp.

Wow, a lot of appeal to intelligence and name calling going on there. I wonder why you've resorted to this.

It explains to me why Christophera has been under constant hammering by you clowns.

Christophera has demonstrated over 200 pages in that debate that he is unwilling to yield to any form of counter-evidence, rather preferring to redirect questions and defer proofs to "common sense." Have you read that thread recently?

Thanks for the entertainment.

If you're interested in being entertained, we have an entertainment and humor subforum.

 

[William Rea]

If you're interested in being entertained, we have an entertainment and humor subforum.

Lol, this forum looks like an intellectual desert when compared to the entertainment and humour subforum, perhaps you're right.

 

[William Rea]

You don't support this statement.

I fear that you are modeling the entire tower as a single column with a heavy load attached at the top (mushroom), when the model and method used to construct WTC 1 and WTC 2 was a three dimensional lattice. NIST describes the benefits of this design as allowing for more rentable area (fewer required vertical members) as it distributed about a fifth of the load bearing into the floor supports.

Except in the set of floors (from the pictures, it appeared to my eye that between three and six floors were directly influenced by the impact) where impact occurred, load distribution could be expected to perform as designed. In the damaged floors, loads were still distributed horizontally somewhat, though in a degraded lattice, which led to floor sag, failures, and some photographs indicate the internal buckling of vertical members associated with the forces from the floor.

For the top to fall off or topple, a significant number of vertical members would have to fail under tension, not in torsion. It doesn't appear that the loads (based on the tilt angles I have seen in various photographs) in the upward direction were sufficient to cause this mass failure (partly due to load distribution via the lattice) before the sag and buckling combination induced the failure in torsion and compression, leading to the "buckling" failure referred to in the OP.

For simplicity, it might be more productive to argue material science in one point, and separately describe why the toppling "should" have occurred.

DR

Thanks for the well considered comments DR, I see where you are coming from and would love to discuss the merits of each paradigm that has been applied to the collapse but this won't ever be the place to do that as long as I have a hole in my ar*e.

 

[rwguinn]

Lol, this forum looks like an intellectual desert when compared to the entertainment and humour subforum, perhaps you're right.

Anyone else notice that when presented with a scenario argued from logic, design, and engineering, he quits answering and runs away?

 

[R.Mackey]

I couldn't be sure but I was pretty certain that this thread would probably end up somewhere abouts in this zone when I first posted in it. It kind of proves to me what I have come to realise which is that this forum is more about politics than it is about truth.

Look William Rea, this will certainly come true if you lead the conversation in that direction with these kinds of inflammatory and immature comments.

If you really want to discuss this, then all you have to do is ignore comments that are rude or unconstructive. And respond to comments that are reasoned and educational. Like mine, for instance.

Yet you choose to do the opposite. Well, it's your choice.