Twoofers Only: The Mark Roberts Factual Error Thread

[metamars]

Do you know the difference between a rigid body and an elastic body?

Do you know the difference between an ideal, pefectly rigid body as used in theories vs. a body which is described as "rigid" by a layman, but is actually an elastic solid? You know, like a steel column? You do know that steel behaves elastically up to a point before plastic deformation also occurs, correct?

I don't know about Bazant's approach. I thought you were trying to assail my formula for impact. Since you are not, I will bow out as it has gone beyond my expertise but if you feel comfortable, carry on.

Both Bazant and, almost certainly, your formula incorporated assumptions of rigid masses impacting steel rods or columns. Before you "bow out", you should at least follow up on your word to tell us what assumptions were used in deriving the formula you quoted.

Was the mass that impacted the rod an ideal, rigid body or wasn't it?

Was the base that the rod rested upon an ideal, rigid body or wasn't it?

The difference between us being that I actually studied from teh book that I took that formula from. I actually studied the very chapter and formula in class. Meanwhile, you did take your formula from a book which I doubt you took the class in. The danger being you are misapplying a formula. My point was about impact.

No I didn't take a class in elastic theory. Since you have taken a class, you should be able to answer my question, which you have already said you would do, regarding whether or not the impacting mass was an ideal, rigid body or not. Surely, your class experience informed you as to what that is, no? Surely you are capable of answering this simple question.

I am not arguing whether the equation is sound, but whether it is applicable. By YOUR equation, if a body is moving at a constant velocity of 100000000 m/s or whether it is moving at 1 m/s makes no difference in the force transferred.

Huh? I don't think you you understand what I've written, at all. Perhaps another JREF'er with a technical background can explain it to you, better than me. You know, somebody like Mackay or Newton's Bit.

Does that sound right to you?

No. See above.

No, it is clear you are applying the formula in a way not intended.

Really? Would Mackay and Newton's Bit agree with this? Frankly, the formula is rather simple. What is there not to understand?

I was waiting for your big reveal on why the impact formula was wrong.

I've already done so. I also asked you specific questions to help you clarify your thinking. All for nought.

Glad we have established that your scale is insufficient to the task.

I'm not aware that we have established this, although the scale is quite up to the task of showing me that I failed to follow my diet.

 

[funk de fino]

That IDEAL, RIGID just jumped out of the bushes eh?

 

[Lurker]

Do you know the difference between an ideal, pefectly rigid body as used in theories vs. a body which is described as "rigid" by a layman, but is actually an elastic solid? You know, like a steel column? You do know that steel behaves elastically up to a point before plastic deformation, correct?

LOL. Yes, I know all about steel. Elastic deformation, yield point, 2% offset, strain hardening region, UTS, necking, break.

I use abstractions as perfectly rigid bodies all the time. I model elastic behavior as well as hyperelastic and viscoelastic behaviors on a regular basis, and to a lesser extent I use elastic-plastic models too. I didn't mean to get you upset, I just wanted to ensure we were both on the same wavelength.

Both Bazant and, almost certainly, your formula incorporated assumptions of rigid masses impacting steel rods or columns. Before you "bow out", you should at least follow up on your word to tell us what assumptions were used in deriving the formula you quoted.

Was the mass that impacted the rod an ideal, rigid body or wasn't it?

Was the base that the rod rested upon an ideal, rigid body or wasn't it?

I thought it was obvious that it was based on elastic bodies. You did see that "k" term in there, right? For a structure that would be analagous to EI, or the material and geometric stiffness of the body.

No I didn't take a class in elastic theory. Since you have taken a class, you should be able to answer my question, which you have already said you would do, regarding whether or not the impacting mass was an ideal, rigid body or not. Surely, your class experience informed you as to what that is, no? Surely you are capable of answering this simple question.

I thought it was obvious when the "k" term was included. My mistake. Classes in elasticity are graduate level Civil Engineering classes. I sat in on a couple of lectures to see if I wanted to take the class but my schedule was already pretty full of other graduate classes so I passed on the Elasticity class.

Huh? I don't think you you understand what I've written, at all. Perhaps another JREF'er with a technical background can explain it to you, better than me. You know, somebody like Mackay or Newton's Bit.

Perhaps. I am not all that conversant with wave propogation theory so that is why I attempted to bow out of the discussion. I do think the equation you are trying to use is being misapplied though.

Really? Would Mackay and Newton's Bit agree with this? Frankly, the formula is rather simple. What is there not to understand?

Formulas, formulas, everywhere. Some are deceptively simple in appearance. But it is in understanding how and when they apply that the expertise comes in. I never claimed to be an expert in the formula you provided so can only make uninformed remarks about it. If I am wrong, that is fine. But to me, it does not seem a good model of what we are examining. You still have to explain why velocity makes no difference in your formula.

I've already done so. I also asked you specific questions to help you clarify your thinking. All for nought.

I guess I will remain in ignorance then.

I'm not aware that we have established this, although the scale is quite up to the task of showing me that I failed to follow my diet.

I would have thought the club hopping would keep you in better shape.

 

[Lurker]

By the way, metamars, why are you using a formula that has the ratio of Fmax(elastic) versus Fmax(rigid)?

In the case of the WTC, wouldn't both the top and bottom be elastic bodies? Neither appears to be rigid so why are you trying to use this formula?

Just wondering...

 

[metamars]

I am sure they do, which contradicts the equation you provided earlier. Anyway, how about the problem that actually relates to the WTC collapse where the impact is in the vertical direction where gravity needs to be considered? Surely you agree that you have two forces acting here:

1. The gravity pulling the piledriver down onto the lower section
2. The force from velocity

As you can see, both are considered in Shigley's equation.

I haven't correctly solved the problem for mass in a gravitational field, nor found the solution. I have found a couple of analytic solutions for a rigid mass hitting an elastic rod, resting on a rigid base, but not in a gravitational field.* Also, the Gul, et. al. paper has a solution, with numerical algorithm, for solving elastic/plastic equation(s), for slender columns, impacted by a rigid mass, and with a gravitational field.


Of course a solution with gravity is desired. That doesn't mean that if you find a solution to a similar problem, yes even one involving gravity in your very own textbook, that it is the correct one. In particular, I have indicated to you why it cannot be the correct or final solution, and in what direction it is wrong or inaccurate.


It's quite possible that, even assuming a reasonable amount of deviation from plumb in the topmost impacted columns, if you solve the problem numerically, you will not even surpass the elastic limit for all of the column segments except the topmost one, and that this one will only get insignificantly bent. Or even, possibly, not plastically, additionally bent, at all.

It's also possible that the topmost column will get bent to the point of failure, but that remains to be seen. Perhaps if would have been seen, by now, had Bazant and Zhou not published their mistaken paper.



* Using rough numbers for a WTC scenario, I came with with something like a maximum compression of .003. If we assume that the real figure would have been about half of this, had the calculation been done with non-rigid impacting masses, then we will not exceed the elastic limit of .002. I.e., Bazant Zhou's conclusion would be reversed.

 

[metamars]

LOL. Yes, I know all about steel. Elastic deformation, yield point, 2% offset, strain hardening region, UTS, necking, break.

Then you know more about this stuff, in general, than I do!

I thought it was obvious that it was based on elastic bodies. You did see that "k" term in there, right? For a structure that would be analagous to EI, or the material and geometric stiffness of the body.


I thought it was obvious when the "k" term was included. My mistake. Classes in elasticity are graduate level Civil Engineering classes.

So does the "k" in:

F = W +W[1+(2hk)/W]^0.5

refer to the rod, only, or both the rod and the impacting mass that hit the rod? If the impacting mass that hit the rod was an ideal, rigid mass, then either it doesn't have a k or it's k-> infinity.

 

[Lurker]

Of course a solution with gravity is desired. That doesn't mean that if you find a solution to a similar problem, yes even one involving gravity in your very own textbook, that it is the correct one. In particular, I have indicated to you why it cannot be the correct or final solution, and in what direction it is wrong or inaccurate.

I apologize. Can you reiterate why you think Shigley's formula is incorrectly applied ro incorrect?

 

[Lurker]

So does the "k" in:

F = W +W[1+(2hk)/W]^0.5

refer to the rod, only, or both the rod and the impacting mass that hit the rod? If the impacting mass that hit the rod was an ideal, rigid mass, then either it doesn't have a k or it's k-> infinity.

Good point. The "k" refers to the impacted body. I'll have to think on the implications of the W portion being elastic vs rigid and what difference, if any, it makes on the the equivalent static force of impact.

 

[Lurker]

Metamars:

Have you tried the simple book drop experiment I outlined yet? Clearly as h rises the force on your arm rises when you try and catch it. I think that illustrates the problem pretty well. You may disagree with the amount of increase in force but Shigley specifically states that if h=0 then F = 2W.

 

[Dave Rogers]

Good point. The "k" refers to the impacted body. I'll have to think on the implications of the W portion being elastic vs rigid and what difference, if any, it makes on the the equivalent static force of impact.

It shouldn't have any effect at all. The spring comprising the upper mass is compressed by the same force as the one compressing the lower mass, so in the case of a zero distance drop both will compress together to twice the equilibrium compression, at which the loading will be twice the static loading.

Dave

 

[cmcaulif]

Maybe someday. If you feel motivated enough to do so now, and post the answer(s), feel free.

I'm not sure why you wouldn't, he is quite helpful.

I know nothing about dynamic snapthrough. I took a course dynamical systems many moons ago, so I have a hazy remembrance of stable limit cycles, but frankly don't know if this is the same as "limit point stability".

Well, If you have Bazant and Cedolin, it is right there in section 4.4. 4.8, on snapdown is also interesting and helpful when you get the time.

Limit point stability is merely another name for snapthrough because the structure will be stable up to some limit, at which an infinitesimal amount of load will cause the structure to be unstable, and thus snapthrough.

Thus, I am in no position to evaluate theory regarding same, though in order for me to have faith in it, I'd have to see some sort of experimental verification.

Just fiddle with a light switch, pg 236:

"Other examples of snapthrough instability are found in various switches (e.g,) the standard wall switch for electric lights)."

The classic example for snapthrough seems to be the flat arch, and for experimentation, Bazant cites Roorda, J. (1965), "stability of Structures with small Imperfections," J. Eng. Mech. (ASCE), 91(1):87-106

I note with some amusement, though, that when I talked with my mathematician cousin last Thanksgiving, I noted that some of the papers on column buckling that I've seen involve Liapunov functions. He told me "Lyapunov functions are BS". I didn't take this as gospel truth, but note that Bazant/Cedolin covers Liapunov theorems (p. 182).

The only point of mentioning this (beside amusement) is that perhaps what my cousin meant is that Liapunov theory is not very insightful for physical systems, in his experience. However, he normally studies things like fluid flows, not collapsing steel.

Its a book on theory, not on code, or practice. There are equations in fluid mechanics that have very limited physical usefulness as well, though I wouldn't say BS.

Can you summarize for us whatever experimental evidence exists for theoretical calculations of "snapthrough" load? Evidence via computer simulation that had been previously validated against real physical columns and rods would also be of interest.

I am still trying to fully wrap my head around some of the theory, but Roorda is cited quite frequently. I have to return my copy of Bazant and Cedolin(interlibrary loan) and I'll see if I can get a copy of the Roorda paper at that time.

 

[Lurker]

"Other examples of snapthrough instability are found in various switches (e.g,) the standard wall switch for electric lights)."

The classic example for snapthrough seems to be the flat arch, and for experimentation, Bazant cites Roorda, J. (1965), "stability of Structures with small Imperfections," J. Eng. Mech. (ASCE), 91(1):87-106

I have worked on some snap through problems myself in the past. Under keys on a keyboard there can be metal snap domes - essentially an arc dome such that a certain amount of force is required before the dome snaps through to the other side and thus completing the circuit and registering a keystroke. The force deflection graph of this would initially have a positive slope but once that force was achieved would rapidly change to a negative slope (or derivative if you would rather).

 

[Disbelief]

Oh, sure! And it's not logical, if I tell you repeatedly that your wife is cheating on you, or driving on the left-hand side of the road, or running naked in the city parks, for you to confront her, either, now is it? Benson and Greening are co-authors with Bazant, you know. Your 'logic' seems rather ad-hoc and self-serving, does it not?

You assume incorrectly. But if I ever come across documentation that says "I, Dr. Bazant, cherry picked rigidity assumptions deliberately, so as to deceive", I will be sure to post it. I find it hard to believe that it wasn't deliberate, but that is not the same as claiming I have proof of same, or even believing that it was.

I certainly suspect it, though, to the point that I have tentatively concluded it was so. Nevertheless, I could be wrong about that.

It isn't necessary for Bazant to have deliberately sought to deceive. I have read both Not Even Wrong and The Trouble with Physics, and am well aware of the capacity of very bright people, such as theoretical physicists, to deceive themselves

Also, in the area of the foundations of physics, in Speakable and Unspeakable in quantum mechanics by J. S. Bell

(emphasis mine)

Nowhere does Bell say that the physicists who produced impossibility proofs for deterministic hidden-variable theories of qm, up to 26 years after they were shown to be wrong, intended to deliberately deceive anybody. Since I assume their proofs were mathematically sound, I can only assume that their physical assumptions were wrong.

It's interesting, isn't it, how many of your presumptions are wrong? It's also interesting how you don't care to address the the key issue I raise concerning the validity, or lack thereof, of Bazant's paper.

Apparently, I can expect nothing more.

Let me see if I follow your logic here. You say you have tentatively concluded that Bazant has deceived, while alos noting that Dr. Greening is a co-author. Therefore, Dr. Greening would have to be in on the deception since he would have done a review of the work. Have you witnessed Dr. Greening's postings here and the nitpicking he does with people? Do you think he would allow the same of a fellow scientist, especially if his name would be linked to it? Why not ask him yourself?

 

[Swing Dangler]

From Mark's Paper:

In his March, 2006 presentation “9/11 - A Closer Look,” Ryan misrepresents Silverstein’s statement “And I said, 'We've had such terrible loss of life, maybe the smartest thing to do is pull it. And they made that decision to pull and then we watched the building collapse."
Kevin Ryan, March, 2006

What could be Ryan’s reason for omitting “We’ve had such terrible loss of life,” which was the basis for Silverstein’s statement? We shall see.
Months later, in a presentation remarkably subtitled “A New Standard of Deception,” Ryan makes a serious error of commission and says, "Larry Silverstein, the leaseholder for all three buildings, essentially admitted to demolishing the building." Meanwhile, this slide appears on screen, to include Silverstein ("and I") as a decision-maker:
Kevin Ryan, May, 2006

Ryan changed “They” to “He,” and then to “We.” He is blatantly lying to try to support his claim.

---First error is a spelling error. I don’t think Mark meant to say Ryan makes a serious error of “commission” but this is the factual error thread.

Now lets examine Mark’s other statement: in light of the facts -

“Ryan changed “They” to “He,” and then to “We.” He is blatantly lying to try to support his claim. “

Here is the public release statement provided by the State Dept's site posts a statement released by Silverstein Properties spokesperson, Mr. Dara McQuillan, on Sept. 9, 2005 that says the following:

In the afternoon of September 11, Mr. Silverstein spoke to the Fire Department Commander on site at Seven World Trade Center. The Commander told Mr. Silverstein that there were several firefighters in the building working to contain the fires. Mr. Silverstein expressed his view that the most important thing was to protect the safety of those firefighters, including, if necessary, to have them withdraw from the building.
Later in the day, the Fire Commander ordered his firefighters out of the building and at 5:20 p.m. the building collapsed. No lives were lost at Seven World Trade Center on September 11, 2001."

In Kevin Ryan's slide presentation, the change from “he” to “we” simply reflects the updated information as released to the public by Silverstein’s own office via the State Department.
But in the deceptive world of Mark Roberts, this is Kevin Ryan lying to support a claim.

No, Mark, Kevin updated his slide because of new information. “We” refers to Mr. Silverstein and the Fire Chief. It is too bad Mark doesn’t do the same with his unfounded assertions and character attacks of Kevin Ryan.

Mark will you do the honorable thing and retract your unfounded accusation and update your research?

 

[RedIbis]

There's also the sticky issue that "pull it" is unlikely to refer to the firefighting operation since there were no firefighters in WTC 7 since 11:30am.

 

[GStan]

---First error is a spelling error. I don’t think Mark meant to say Ryan makes a serious error of “commission” but this is the factual error thread.

Now lets examine Mark’s other statement: in light of the facts -

Here is the public release statement provided by the State Dept's site posts a statement released by Silverstein Properties spokesperson, Mr. Dara McQuillan, on Sept. 9, 2005 that says the following:

In the afternoon of September 11, Mr. Silverstein spoke to the Fire Department Commander on site at Seven World Trade Center. The Commander told Mr. Silverstein that there were several firefighters in the building working to contain the fires. Mr. Silverstein expressed his view that the most important thing was to protect the safety of those firefighters, including, if necessary, to have them withdraw from the building.
Later in the day, the Fire Commander ordered his firefighters out of the building and at 5:20 p.m. the building collapsed. No lives were lost at Seven World Trade Center on September 11, 2001."

In Kevin Ryan's slide presentation, the change from “he” to “we” simply reflects the updated information as released to the public by Silverstein’s own office via the State Department.
But in the deceptive world of Mark Roberts, this is Kevin Ryan lying to support a claim.

No, Mark, Kevin updated his slide because of new information. “We” refers to Mr. Silverstein and the Fire Chief. It is too bad Mark doesn’t do the same with his unfounded assertions and character attacks of Kevin Ryan.

Mark will you do the honorable thing and retract your unfounded accusation and update your research?

Yes, Mark, please just rectract it and spare us the 5 to 10 pages of pointless semantic arguments over the differences between a fact and an opinion.

Swing, what are you doing? Mark's assertion about Ryan lying is clearly his opinion of his motives for the change, not a presentation of fact. Even if one could prove that that was not the reason for the text change, it would still not represent a factual error, just that his opinion was incorrect. As a truther, I assume the difference between fact and opinion will not matter to you.

Page 18
Factual Errors = 0
Accusations of Factual Errors that, if true, would even matter to any theory or interpretation of the events of 9/11 = 0

 

[TimB1]

There's also the sticky issue that "pull it" is unlikely to refer to the firefighting operation since there were no firefighters in WTC 7 since 11:30am.

But there were some in the area of WTC7, trying to put the fires out. There had to be, remember, to hear the countdown to the demolition which broadcaster Amy Goodman also heard and covered up, since she's in on the plot.

 

[Dave Rogers]

---First error is a spelling error. I don’t think Mark meant to say Ryan makes a serious error of “commission” but this is the factual error thread.

What is the spelling mistake here? "Error of commission" is a perfectly acceptable term, the antithesis of "error of omission", i.e. Ryan has done something erroneous rather than failed to do something correct. Google it.

For the remainder, I assume you're arguing that the decision to pull the firefighters was a joint one between Silverstein and the Fire Department Commander.

"[...] Mr. Silverstein expressed his view that the most important thing was to protect the safety of those firefighters, including, if necessary, to have them withdraw from the building.
Later in the day, the Fire Commander ordered his firefighters out of the building and at 5:20 p.m. the building collapsed."

Silverstein expressed a view. The Fire Commander gave the order later, having heard Silverstein's views. That clearly shows that it was not a joint decision, but a decision by the Fire Commander prior to which he listened to Silverstein's opinions. As usual, your own quote refutes your argument.

Dave

 

[Belz...]

There's also the sticky issue that "pull it" is unlikely to refer to the firefighting operation since there were no firefighters in WTC 7 since 11:30am.

So the firefighters aren't in on it, after all ?

 

[RedIbis]

So the firefighters aren't in on it, after all ?

One of the more distasteful strategies of the debunker crowd is to suggest that such scrutiny of the bldg collapses encompasses firefighters being "in on it."

If you can't quote me making such an absurd claim, please keep that rule 8 away from me.

Thank you.