9/11 Collapse Theory Discussion Thread II

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Fidel
9/11 Collapse Theory Discussion Thread II
jrootham

Ok, now that we have this thread, I will make the (short) substantive response to Fidel and jas.

They were complaining about my use of the term massive with respect to the fires in athe WTC.

I will restate my position.  The towers came down as a result of large airplanes hitting the towers and subsequent fires.  The NIST analysis is correct.

The pictures posted in the earlier thread showing truly massive fires are quite impressive.  The difference between those buildings and the WTC is that they were not hit by large aircraft, so there was no initial structural damage and the fire insulation on the structural steel was intact.

The photos are an impressive demonstration of the value of insulating structural steel.

 

Fidel

Even though far more severe fires have never ever not once caused a single steel column to collapse in hundreds of other fires that  raged in other steel frame high rises - all of which were 15 floors or more and with some fires lasting hours longer than the ones that felled WTC buidlings 1, 2, and especially #7 and regardless of the impressive 9/11 photos? We wish we could be that confident in the official conspiracy theory, but a number of things prevent truth seekers from jumping to that conclusion.

Fidel

Pants-of-dog wrote:
[url=http://rabble.ca/babble/humanities-science/911-collapse-theory-discussio... Griscom's delta-t and Garcia's delta-t seem to tb ethe same. Yours is not. Please note that Griscom and Garcia's definitions both involve a change in the velocity during a transfer of momentum. Your right angle calculation and the subsequent calculation assume a constant velocity and do not mention momentum at all.

So does Garcia use velocity. We're using his equation for force balance after all. Let's try applying simple logic to this one, because you still don't seem to be very confident in your assessment of delta t no matter whose number it is, whether it's Garcia's or Griscom's. Because when you say "seem to be the same", it tells me you're not sure and not trusting anyone on this, and especially not me.

[url=http://rabble.ca/babble/humanities-science/science-fail-nist-physics-tel... here[/url] you say:

Pants-of-dog wrote:
And so how does Dr. Griscom arrive at dt = 0.14 second? That's the $64,000 dollar question. I have no idea. In that respect, he is as uninformative as Dr. Garcia.

In that post you were absolutely not sure how either Griscom or Garcia arrived at delta t. And I had just finished saying that neither Griscom nor I were sure how Garcia determined that dt=0.01s. Actually, I did have some idea but wasn't revealing it to you at the time in favour of being just another game contestant on $64000 dollar question.

So to summarize, none of Griscom, you nor I claimed to know how Garcia calculated dt=0.01s.

On the other hand, both Griscom and I think one degree of tilt would result in dt=0.14s. I've shown my work but he has not. It's the same value to two or three decimal places as Griscom's number and for whom figuring delta t at one deree of tilt is a no-brainer. He's prolly done it in his sleep thousands of times before. However, you are not included in this sub set of those who understand how Griscom arrived at dt=0.14s, . because as you said before, it's a $64,000 dollar question. So in your case, you and you alone have no idea how either Garcia or Griscom calculated dt in either case. I know how Griscom calculated dt when upper block is rotated on the horizontal axis to one degree of tilt.

In other words, I am absolutely sure of how both Griscom and I arrived at dt=0.14s. I would bet the farm on it because I am that confident in my own understanding of this math problem laid out and explained to some extent by Dr. Garcia himself. Are you sure of yourself, Pants? Can you hazzard a guess as to how dt was calculated by either Garcia or Griscom? What makes you believe the answer to this expression is no longer the $64,000 dollar mystery you previously believed it to be? Or is this just another $64,000 dollar question?

siamdave

jrootham wrote:

Ok, now that we have this thread, I will make the (short) substantive response to Fidel and jas.

They were complaining about my use of the term massive with respect to the fires in athe WTC.

I will restate my position.  The towers came down as a result of large airplanes hitting the towers and subsequent fires.  The NIST analysis is correct.

The pictures posted in the earlier thread showing truly massive fires are quite impressive.  The difference between those buildings and the WTC is that they were not hit by large aircraft, so there was no initial structural damage and the fire insulation on the structural steel was intact.

The photos are an impressive demonstration of the value of insulating structural steel.

 

- I will try to deconstruct and disprove this idea. I need a bit more information. Step by step. First - how do you feel the fireproofing was disldoged? From the 'vibrations' or something caused by the impact, or by direct impact of flying debris?

Second - how much of the fireproofing was dislodged? That is, only at or around the direct area of impact, or did this dislodging of fireproofing somehow affect those central core beams throughout large parts of the WTC 1 and 2? There were some 47 columns in the central core - are you suggesting the fireproofing was dislodged from all or most of these columns? A bit of special attention to the south tower where the corner imact was would be appreciated - it is hard to see how any more than a small handful of central columns would have been affected in any way from this crash.

(you can be thinking about WTC7, which we will maybe get at later - small fires, no plane impact, yet it collapsed like the other two ...)

 

 

Pants-of-dog

Fidel wrote:

.....

So does Garcia use velocity. We're using his equation for force balance after all. Let's try applying simple logic to this one, because you still don't seem to be very confident in your assessment of delta t no matter whose number it is, whether it's Garcia's or Griscom's. Because when you say "seem to be the same", it tells me you're not sure and not trusting anyone on this, and especially not me.

....

In that post you were absolutely not sure how either Griscom or Garcia arrived at delta t. And I had just finished saying that neither Griscom nor I were sure how Garcia determined that dt=0.01s. Actually, I did have some idea but wasn't revealing it to you at the time in favour of being just another game contestant on $64000 dollar question.

So to summarize, none of Griscom, you nor I claimed to know how Garcia calculated dt=0.01s.

On the other hand, both Griscom and I think one degree of tilt would result in dt=0.14s. I've shown my work but he has not. It's the same value to two or three decimal places as Griscom's number and for whom figuring delta t at one deree of tilt is a no-brainer. He's prolly done it in his sleep thousands of times before. However, you are not included in this sub set of those who understand how Griscom arrived at dt=0.14s, . because as you said before, it's a $64,000 dollar question. So in your case, you and you alone have no idea how either Garcia or Griscom calculated dt in either case. I know how Griscom calculated dt when upper block is rotated on the horizontal axis to one degree of tilt.

In other words, I am absolutely sure of how both Griscom and I arrived at dt=0.14s. I would bet the farm on it because I am that confident in my own understanding of this math problem laid out and explained to some extent by Dr. Garcia himself. Are you sure of yourself, Pants? Can you hazzard a guess as to how dt was calculated by either Garcia or Griscom? What makes you believe the answer to this expression is no longer the $64,000 dollar mystery you previously believed it to be? Or is this just another $64,000 dollar question?

Then it should be easy for you to show me where you discuss momentum in your calculations. Since Griscom and Garcia are looking at momentum, and since your math is supposedly dealing with the same thing, you should be able to show how your calculations deal with momentum.

Pants-of-dog

Fidel wrote:

Even though far more severe fires have never ever not once caused a single steel column to collapse in hundreds of other fires that  raged in other steel frame high rises - all of which were 15 floors or more and with some fires lasting hours longer than the ones that felled WTC buidlings 1, 2, and especially #7 and regardless of the impressive 9/11 photos? We wish we could be that confident in the official conspiracy theory, but a number of things prevent truth seekers from jumping to that conclusion.

The WTC buildings are not the only steel frame buildings to have suffered structural collapse by fire.

There is the McCormick Place fire in Chicago:

http://www.time.com/time/magazine/article/0,9171,843401,00.html

Here is a pdf detailing a partial structural collpase caused by a fire in a steel framed building:

http://www.usfa.dhs.gov/downloads/pdf/publications/TR-061.pdf

jrootham

There is no direct evidence on how much insulation was damaged.  However, having a large aircraft hit a building would seem really likely that there was some damage.  We know that the structure did not fail immediately, but only after burning for some time.  Given what we know about steel and fire the implication is that the insulation was damaged.

WTC7 was hit by aircraft parts that passed through one of the towers.  It's collapse was a little more surprising in that there was less immediate damage, but the NIST model showed that there were some critical parts of that building, which apparently failed.

 

Pants-of-dog

siamdave wrote:

....

- I will try to deconstruct and disprove this idea. I need a bit more information. Step by step. First - how do you feel the fireproofing was disldoged? From the 'vibrations' or something caused by the impact, or by direct impact of flying debris?

Second - how much of the fireproofing was dislodged? That is, only at or around the direct area of impact, or did this dislodging of fireproofing somehow affect those central core beams throughout large parts of the WTC 1 and 2? There were some 47 columns in the central core - are you suggesting the fireproofing was dislodged from all or most of these columns? A bit of special attention to the south tower where the corner imact was would be appreciated - it is hard to see how any more than a small handful of central columns would have been affected in any way from this crash.

(you can be thinking about WTC7, which we will maybe get at later - small fires, no plane impact, yet it collapsed like the other two ...)

Fireproofing is applied in two ways: It is either built around the steel structure, or it is sprayed directly on the structure. Gypsum sheathing and concrete sheathing are built around th esteel, while spray on cemetitious mixtures and intumescent paint are spray applied.

Concrete is heavy, so I do not think it would have been used in the WTC. Intumescent paint is expensive, and I am not sure you can get a 3 hour fire resistance rating (as required by the NYC building codes at the time of the WTC construction) with them anyway. Spray on fire proofing is usually applied with a big truck with a hose attached. It would had to have been an incredibly long hose to reach the 78th floor. Perhaps there are different apllication methods for using spray fire proofing in high rise buildings, but I do not know them.

This leaves gypsum sheathing, which would have been dislodged when the supporting structure was impacted.

Pants-of-dog

jas wrote:
Here is another video of WTC1

http://www.plaguepuppy.net/public_html/video%20archive/Shaking%20before%...

that shows more clearly that it is the upper block disintegrating before the lower block begins to fall. I hold my cursor icon at the last level of damaged floor (see the tiny line of windows dotted with orange fire that we also see in our above gif) so I have a steady point from which to gauge the shortening of the upper block before it is obscured by the dust clouds. We see that dotted line of orange fire stay in place and turn into large bursts of flame as the collapse progresses.

We also see the antenna tilt over, suggesting complete disintegration.

This seems to be yet another episode of each of us seeing waht we want to see. To me, it clearly shows the destrcution of the impact zone, and then the dust cloud gets so thick that you can't see anything else. The object that you believe is the antenna may or may not be the antenna. It is impossible to tell.

Pants-of-dog

http://www.rabble.ca/comment/1164827/Well-Pants-and-NIST

Fidel wrote:
Well since Pants (and NIST, Bazant and Greening by wild coincidence) are simply skipping over "CI" so conveniently, I think they used either a military grade spray-on nanothermite on the steel columns, or they used hydraulics as per the ABC building demo in France. One of those two methods or perhaps even a combination.

What do you mean by "they used hydraulics as per the ABC building demo in France"?

Fidel

Pants-of-dog wrote:
Then it should be easy for you to show me where you discuss momentum in your calculations. Since Griscom and Garcia are looking at momentum, and since your math is supposedly dealing with the same thing, you should be able to show how your calculations deal with momentum.

Jeez, I was under the illusion that we were working with Garcia's equations, the ones where he sets them up to include no air resistance, and absolutely zero resistance from the 47 massive steel inner core columns and none from the 200 outer columns at the peripheries of each floor? Is this now not the case, Pants?

Does this equation look familiar to you, Pants?:

[m*v(final) - m*v(initial)]/dt = F - m*g

Pants-of-dog

Fidel wrote:
Jeez, I was under the illusion that we were working with Garcia's equations, the ones where he sets them up to include no air resistance, and absolutely zero resistance from the 47 massive steel inner core columns and none from the 200 outer columns at the peripheries of each floor? Is this now not the case, Pants?

None of this is relevant to my post.

Fidel wrote:
Does this equation look familiar to you, Pants?:

[m*v(final) - m*v(initial)]/dt = F - m*g

Yes. That is Garcia's equation. Please show how the change in time that you calculated with your right angle calculation is the same change in time that Garcia mentions here.

Also, please note that Garcia's equation concerns momentum (m*v). I would like to see how your calculations also deal with this quantity.

Thank you.

jas

Pants-of-dog wrote:

This seems to be yet another episode of each of us seeing waht we want to see. To me, it clearly shows the destrcution of the impact zone, and then the dust cloud gets so thick that you can't see anything else. The object that you believe is the antenna may or may not be the antenna. It is impossible to tell.

http://www.plaguepuppy.net/public_html/video%20archive/Shaking%20before%...

You "can't tell" what is happening to the antenna? I'm sorry that you don't see very well. Either that, or you're simply not capable of properly interpreting visual evidence.

As you know, I posted a second link to a better video which shows the upper block crushing itself, losing half its mass before the building begins to fall:

http://www.plaguepuppy.net/public_html/collapse%20update/close-up_north_...

I probably won't be wasting my time with your arguments in this thread. Let me know when you find visual proof that Bazant's "piledrivers" ever existed.

Fidel

Pants-of-dog wrote:

http://www.rabble.ca/comment/1164827/Well-Pants-and-NIST

Fidel wrote:
Well since Pants (and NIST, Bazant and Greening by wild coincidence) are simply skipping over "CI" so conveniently, I think they used either a military grade spray-on nanothermite on the steel columns, or they used hydraulics as per the ABC building demo in France. One of those two methods or perhaps even a combination.

What do you mean by "they used hydraulics as per the ABC building demo in France"?

Lookup Balzac-Vitry demolition or Balzac-Vitry verinage. Apparently it's a method of demolition using hydraulic jacks. But remember, the A&Es only have to provide reasonable doubt surrounding the official conspiracy theory for collapse initiation in order to warrant a real and transparent investigation. They don't have to actually do NIST's job for them and discover the real cause. That would require a real and transparent investigation and with people held accountable.

jas

jrootham wrote:

I will restate my position.  The towers came down as a result of large airplanes hitting the towers and subsequent fires.  The NIST analysis is correct.

So you're changing your position from "massive" fires to "subsequent" fires. Good. Is that because you finally looked at some pictures of the actual event? Or is it because I pointed out to you that all the fires occurred in the upper blocks?

Pants-of-dog

jas wrote:

You "can't tell" what is happening to the antenna? I'm sorry that you don't see very well. Either that, or you're simply not capable of properly interpreting visual evidence.

As you know, I posted a second link to a better video which shows the upper block crushing itself, losing half its mass before the building begins to fall:

">http://www.plaguepuppy.net/public_html/collapse%20update/close-up_north_...

I feel somewhat foolish. The movie that is the post of yous that I quoted was not the one I was commenting on. I was actually commenting on the second one. I have now watched both videos. Let us be a bit more clear on which is which.

In one (the one that has shaking in the title) we clearly see the antenna tilting at the beginning of the collpase, though it seems to stop rotating right before it is engulfed by the dust cloud.

In the other one (let's call it close-up) there is an element that may or maynot be the antenna that has definitely fallen off the upper block or impact zone.

In both movies, we see the upper block demolish the impact zone. We do not see the upper block itself demolished.

jas

If that's the case, the impact zone is half the height of the upper block. So your calculations would need to be changed.

jrootham

No I am modifying my language to avoid nit picking objections.  As in, it depends on what the meaning of "is" is.  I have not changed my substantive position one iota.

 

jas

Actually, it depends on what the meaning of "massive" is, jrootham. Smile

Pants-of-dog

Fidel wrote:

Lookup Balzac-Vitry demolition or Balzac-Vitry verinage. Apparently it's a method of demolition using hydraulic jacks. But remember, the A&Es only have to provide reasonable doubt surrounding the official conspiracy theory for collapse initiation in order to warrant a real and transparent investigation. They don't have to actually do NIST's job for them and discover the real cause. That would require a real and transparent investigation and with people held accountable.

Is ABC short for Balzac-Vitry?

Anyways, does verinage demolition use hydraulic jacks?

Fidel

Pants-of-dog wrote:

Fidel wrote:
Jeez, I was under the illusion that we were working with Garcia's equations, the ones where he sets them up to include no air resistance, and absolutely zero resistance from the 47 massive steel inner core columns and none from the 200 outer columns at the peripheries of each floor? Is this now not the case, Pants?

None of this is relevant to my post.

But with a bit of logic above I explained how you previously had no concept of delta t or how it's derived. Now you seem to be sure that I don't know. How is this possible that you didn't understand before, but now you're sure that I am wrong? It seems to me that you are a master of confusion. Some might even call it trolling.

Pants-of-dog wrote:
Fidel wrote:
Does this equation look familiar to you, Pants?:

[m*v(final) - m*v(initial)]/dt = F - m*g

Yes. That is Garcia's equation. Please show how the change in time that you calculated with your right angle calculation is the same change in time that Garcia mentions here.

Also, please note that Garcia's equation concerns momentum (m*v). I would like to see how your calculations also deal with this quantity.

Thank you.

I am using Garcia's equations as he accounts for momentum and force: "time rate of change of momentum = sum of forces" Is there something wrong with that, Pants? Wouldn't it be easier to admit that you're completely lost?

Fidel

TROLL-o-rama!

Pants-of-dog

Fidel wrote:
But with a bit of logic above I explained how you previously had no concept of delta t or how it's derived. Now you seem to be sure that I don't know. How is this possible that you didn't understand before, but now you're sure that I am wrong? It seems to me that you are a master of confusion. Some might even call it trolling.

Your confusion is based on the incorrect assumption that I was unaware of how delta-t may be calculated using calculus to do so. You just think I have no calculus experience. Though I will admit it has been years since I used it.

Let us say that calculus is necessary to calculate delta-t.

Fidel wrote:

I am using Garcia's equations as he accounts for momentum and force: "time rate of change of momentum = sum of forces" Is there something wrong with that, Pants? Wouldn't it be easier to admit that you're completely lost?

Your calculation for delta-T involved no calculus. You claim (and I agree) that calculus is used to calculate delta -T, and then you assume that your delta-T is the correct one, even though you didn't use calculus to figure it out.

Do you see how you are contradicting yourself?

Pants-of-dog

Fidel wrote:

TROLL-o-rama!

Perhaps you should flag the appropriate post as questionable.

writer writer's picture

I know I have.

Pants-of-dog

jas wrote:

If that's the case, the impact zone is half the height of the upper block. So your calculations would need to be changed.

Sure. The added distance would add a lot to the impact velocity, which is far more important than the mass of the upper block. This is because kinetic energy is directly proportional to the mass, but is also directly proportional to the square of the velocity. This would mean that the upper block had even more kinetic energy at the moment of impact.

Fidel

Pants-of-dog wrote:

Fidel wrote:

TROLL-o-rama!

Perhaps you should flag the appropriate post as questionable.

I've shown that you are not debating so much as using circular argument and contradicting yourself in the process. And sooner than admit to having already admitted that you don't know what you're talking about, you call me a liar in so many words. That's trolling in my opinion. It would be a lot easier for you to take an upper level math course and master that than trying to untwist your own spaghetti logic you've tried to confuse us with here. I think you have a wonderfully nimble mind, Pants. You're wasting it though.

Pants-of-dog

Speculating about my math education, or lack thereof, is not an argument.

My observation concerning the fact that you did not use calculus to determine your delta-T is completely independent of my math skills.

jas

I don't think your analysis is or would be correct, pants.

But it does appear that you are stating that Bazant's initial calculations are incorrect and that they do not describe the reality.

Pants-of-dog

jas wrote:
I don't think your analysis is or would be correct, pants.

Feel free to show me how it would be incorrect.

jas wrote:
But it does appear that you are stating that Bazant's initial calculations are incorrect and that they do not describe the reality.

No, I am saying that even if you are correct about your observations and Bazant is not (which I do not agree with), gravitational collapse would still occur.

jas

Bazant is clearly not correct if he hasn't accounted for the upper block losing half its floors. That is elementary.

Pants-of-dog

jas wrote:

Bazant is clearly not correct if he hasn't accounted for the upper block losing half its floors. That is elementary.

I think that Bazant is correct and that you are mistaken about the number of floors in the upper block that were destroyed.

Fidel

Pants-of-dog wrote:

Speculating about my math education, or lack thereof, is not an argument.

My observation concerning the fact that you did not use calculus to determine your delta-T is completely independent of my math skills.

Oh you can prove dt with simple trig even with Garcia's dt=0.01s. It works for both values of dt. What are the odds, Pants?

And I didn't use the calculus. I used simple trig and laid it out for you easy peasy. So did Griscom use trig. I am friends with David Griscom on FaceBook, and he confirmed it for me. The internet really does make it a smaller world, Pants.

You're trolling in my opinion.

jas

Pants-of-dog wrote:

I think that Bazant is correct and that you are mistaken about the number of floors in the upper block that were destroyed.

You just finished saying that the larger impact zone would increase the velocity of the "fall" of the upper block. Are you now recanting that?

Pants-of-dog

Fidel wrote:

Oh you can prove dt with simple trig even with Garcia's dt=0.01s. It works for both values of dt. What are the odds, Pants?

And I didn't use the calculus. I used simple trig and laid it out for you easy peasy. So did Griscom use trig. I am friends with David Griscom on FaceBook, and he confirmed it for me. The internet really does make it a smaller world, Pants.

You're trolling in my opinion.

I see. Well, perhpas it would be best if you simply showed me how your calculations deal with momentum, then.

Fidel

I already did. They are Garcia's own equations, the person YOU are supposed to be defending and not me you troll. And in case you haven't realized it, Garcia is the one who attempts "proof by intimidation" of Bazant's collapse theory. Zdenek Bazant is that other person whose collapse theory you allege to support.

Pants-of-dog

jas wrote:

Pants-of-dog wrote:

I think that Bazant is correct and that you are mistaken about the number of floors in the upper block that were destroyed.

You just finished saying that the larger impact zone would increase the velocity of the "fall" of the upper block. Are you now recanting that?

No. I am making what is called a conditional statement.

To be honest, I think that the Bazant model simply errs on the conservative side. By that I mean that if there is a confusion about a certain number (e.g. the number of floors in the impact zone), Bazant chooses the number that is least likely to cause gravitational collapse(e.g. only one storey). He does this so that when his math shows that gravitiational collpase is possible for his model, he can be sure that it is also possible in reality.

Pants-of-dog

Fidel wrote:

I already did. They are Garcia's own equations, the person YOU are supposed to be defending and not me you troll. And in case you haven't realized it, Garcia is the one who attempts "proof by intimidation" of Bazant's collapse theory. Zdenek Bazant is that other person whose collapse theory you allege to support.

I'm sorry. I should have been clearer. I want to know how you deal with momentum in your equations you sue to calculate delta-t. I am already aware of how it works with the momentum after that.

Fidel

You want me to explain Garcia's equations for you?  What part of Garcia's force balance equations are you unsure of now? Can you give us a clue? Perhaps you should just stop supporting Garcia's defence of Bazant at this point since you clearly have no idea what anyone is talking about period. My god, poor Canada.

Pants-of-dog

Pants-of-dog wrote:

...

Anyways, does verinage demolition use hydraulic jacks?

I have been unable to find any information on the internet. I am willing to concede that it does for the sake of argument. It is a logical assumption.

Where would they be installed?

Fidel

You have many questions, Pants. They could be answered with a legitimate investigation of ALL of the events surrounding 9/11. 

Pants-of-dog

Fidel wrote:

You want me to explain Garcia's equations for you?  What part of Garcia's force balance equations are you unsure of now? Can you give us a clue? Perhaps you should just stop supporting Garcia's defence of Bazant at this point since you clearly have no idea what anyone is talking about period. My god, poor Canada.

I am not discussing how Garcia got his delta-t. I am talking about how you got yours.

This is how you calculate delta-t, correct?:

Quote:

Rt-Angle triangle calculator here

Using the right angle triangle calculator on that page,

1. Use 63.4 for side "c", which is the length of the floor in metres
2. Use 1°  for angle "A" and click calculate. It should give you 1.106 or 1.11 for side "a", or the distance in metres which the high end of the tilted floor has yet to fall after the lower end makes initial contact with the top floor of the lower block.

From your post here:

http://www.rabble.ca/comment/1162759/Pants-dog-wrotePlease

I want to know how you factor in momentum (m*v) in this part of your calculations.

I ask this because delta-t is defined as a very brief time interval during which the impact occurs and the momentum changes from m*v(initial) to m*v(final). This is Garcia's exact definition, bad grammar and all.

Therefore any calculation of delta-t depends on the transfer of momentum. Please show me how your calculation depends on momentum transfer.

Pants-of-dog

Fidel wrote:

You have many questions, Pants. They could be answered with a legitimate investigation of ALL of the events surrounding 9/11. 

I think the jacks would have to be installed wherever the collapse started, right? Because the collapse starts when you get rid of the supporting jacks.

oldgoat

Oh for gods sake Fidel this is fucking math we're talking about here!  MATH!!

 

I know that if you enter .7734 into a calculator and turn it upside down it says hello.  (you probably have proof that it says hello from aliens, but we won't go there :p )That is the outer extent of my sophistication at math.

 

Stop taking things so freakin' personally and calling people trolls. 

jas

Pants-of-dog wrote:

if there is a confusion about a certain number (e.g. the number of floors in the impact zone), Bazant chooses the number that is least likely to cause gravitational collapse(e.g. only one storey).

No number of destroyed upper floors above the halfway point of the building would cause gravitational collapse, but, that aside, are you saying that Bazant calculates for collapse based on one storey being damaged? Do his calculations not have to reflect how many storeys were in the upper block piledrivers? Were the calculations you showed us not Bazant's?

jas

oldgoat wrote:

I know that if you enter .7734 into a calculator and turn it upside down it says hello.

Oooo...

* shivers *

....ghost in the machine....

Pants-of-dog

jas wrote:

No number of destroyed upper floors above the halfway point of the building would cause gravitational collapse, but, that aside, are you saying that Bazant calculates for collapse based on one storey being damaged? Do his calculations not have to reflect how many storeys were in the upper block piledrivers? Were the calculations you showed us not Bazant's?

Please provide evidence for the bolded claim.

The calculations I was basing my math on were actually Greening's, if I recall correctly. He calculates for the upper block falling through one storey. This is because the upper block must have had to fall through at least one storey. It probably fell more, in reality.

Bazant's model may be more accurate in this respect, as it has been so far, but I would have to check that again.

Fidel

Pants-of-dog wrote:
I want to know how you factor in momentum (m*v) in this part of your calculations.

I ask this because delta-t is defined as a very brief time interval during which the impact occurs and the momentum changes from m*v(initial) to m*v(final). This is Garcia's exact definition, bad grammar and all.

And note that you cut off the rest of Garcia's compound sentence which went on to say: "...and F is the force of resistance by the lower structure." Impact occurs and moment changes from m*v(i) to m*v(f) within the upper and lower limits for duration of impact. Iows, you can't remove dt from the equation and demand to know where the expression dt itself accounts for momentum. That makes no sense. Delta t is part of the larger equation describing the impulse momentum form of Newton's 2nd Law.

Pants-of-dog wrote:
Therefore any calculation of delta-t depends on the transfer of momentum. Please show me how your calculation depends on momentum transfer.

Garcia's value for dt is 0.01s, if we can agree on this much. He is assuming some negligible angle of tilt that amounts to nothing substantial. Impact occurs in a nearly straight line of contact between upper and lower blocks with minimal duration once contact is made after a 3 metre fall that is unimpeded by either air resistance or by any of the approximately 250 steel columns. Failure of all 47 massive inner core columns and 200 outer steel support columns occurs simultaneously for all intents and purposes. I remember you suggested before that this could not be what Garcia is suggesting with his force balance equations. And I am saying, yes, he does imply this. Because both of you insist that all of the steel columns were overwhelmed by a massive and rigid upper block. There is no estimation for the resistive upward force of the 250 steel columns, because according to Bazant and Garcia, it doesn't matter apparently. And if you still don't believe me, then it's clearly up to you to show us where in Garcia's force balance equations that he factors in resistance by 250 steel columns or even air.

jrootham

This is not what the NIST report claims.  To the extent that they describe what happens after the initial failure.

Order of events is as follows:

First floor fails, it pulls on vertical columns, they fail (as in break horizontaly) , the first floor falls on the floor below, it fails, it pulls on the vertical columns (some of which have already failed) somewhere along here all the vertical columns have failed.  the second floor down (and all the stuff above it) falls on the third floor down, which then fails.  etc.

It's like a zipper, pull all of the teeth, it's tough, pull one at a time it's easy.  The floors failed one at a time (but very quickly in each case).

 

Pants-of-dog

Fidel wrote:

And note that you cut off the rest of Garcia's compound sentence which went on to say: "...and F is the force of resistance by the lower structure." Impact occurs and moment changes from m*v(i) to m*v(f) within the upper and lower limits for duration of impact. Iows, you can't remove dt from the equation and demand to know where the expression dt itself accounts for momentum. That makes no sense. Delta t is part of the larger equation describing the impulse momentum form of Newton's 2nd Law.

Perhaps it would be best if you could show us how Griscom calculates delta-t, then?

Fidel wrote:
Garcia's value for dt is 0.01s, if we can agree on this much. He is assuming some negligible angle of tilt that amounts to nothing substantial.

I am not at all certain that Garcia's impact time has anything to do with tilt angle.

 

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