Goodbye, Mr Roberts

[ThePythonicCow]

Re: Goodbye, Mr Roberts

I think it is safe to say Delpht was not significantly over the theoretical free fall time as is the smaller building video. And these weren't demo jobs.

If non-demo jobs can approach free fall speed, why not the WTC buildings? Note Delpht - the fire started on the 6th floor (out of 13).

Delpht wasn't a "falling anvil" collapse so as I can tell. It is entirely possible from what little I know so far that:

• Floors 6 and up all collapsed almost simultaneously, each floor having already been weakened by many hours of raging fire.
• Floors 1 to 5 did one of:
  • Collapse later that night, after the fire from the upper floor collapse had time to rage through the lower floors for a few hours, or
  • Some or all of them did not collapse (I can't tell what happened to the first floor or two from the pictures I've seen)
  • Some or all of them did collapse as if hit with the "Falling Anvil" of the upper floors, causing those falling upper floors to decelerate as they impacted those lower floors -- But you do not have the accurate measurements of the position, velocity and acceleration of any specific spot on an upper floor during the time period of the lower floors collapsing to determine the presence or absence of such deceleration during that collapse.

What we can see is the upper floors collapsing "quickly". Sure, no problem.

Floor 6 quite possibly did not collapse because it was impacted above from a falling floor 7, but rather because it was so weakened that it fell "out from under" floor 7, pulling it (and all the fire weakened floors from there on up) down on top of itself.

Floor 6, if it was any where close to as fire damaged as the floors above it (and I'm guessing it was) would have probably gone first, since it (1) was constructed the same way, but (2) bore more weight than the floors above.

This is not just a matter of how fast the building falls.
This is not just a matter of how fast the building falls.
This is not just a matter of how fast the building falls.

It is a matter of observing how much force a falling upper section is putting on a structurally sound (until the point of collapse) lower portion by observing the motion of that upper portion during some time interval in which it is claimed that the impacts of the falling upper section are causing the collapse of the lower section.

Given accurate measurements of that motion (multiple reliable position measurements over time) one can calculate (1) the upper portions position, (2) the upper portions velocity, (3) the upper portions acceleration, and hence finally (4) the force which the upper portion is placing on the lower portion during that time interval.

If, given all that, you find that the force (4) is less than the normal static load which the lower portion could support at that time, then that force did not and will not cause the collapse of the lower portion.

If the lower portion collapses anyway during that time interval, then there must be some other cause for its collapse.

[ThePythonicCow]

Re: Goodbye, Mr Roberts

In this video, the man stands on the board and even bounces a bit. He then runs, jumps up no more than 4 feet, and breaks the board. Impact vs. Static load.

Yes, Absolutely, Of course this can happen rather easily. No Problemo.

But, But, But if you had accurate measurements of the man's position over the time period in which his fall broke the board, you would see that the force (proportional to his deceleration, which is the second derivative of his position) that he exerted on the board exceeded his static weight, indeed that it exceeded whatever static load the board could have held.

Good Grief, C1ue -- How Many Times Do I Have To Explain This?

(I'm tempted to change the quote prompt for you at the top of this reply from c1ue to c1ueless , as you sometimes have fun doing on the global warming thread, but I'm trying to resist the temptation.)

[ThePythonicCow]

Re: Goodbye, Mr Roberts

Impact damage not evenly spread throughout the core - certainly most on one side.

Exterior columns showed visible deformation.

Slam dunk for collapse? No

Possibility for collapse? Absolutely

The Chandler work that I am focusing on for the last couple of days involves the mechanism for the collapse of the lower floors, below the impact zone in WTC1.

Yes, there is still a plausible argument that the floors on and above the impact zone collapsed due to the plane damage and fire, as the official story claims. I'd wager a pretty penny (gold coin?) this didn't happen, but I cannot prove that this didn't happen with what I know now.

[ThePythonicCow]

Re: Goodbye, Mr Roberts

As for Chandler - he makes a number of assumptions which bring his conclusion into doubt:

1) He assumes the entire force is evenly transmitted through the entire structure. This is the same error which skyson makes. ...

His model is quite simple, yes. He makes no effort to do a dynamic structural analysis, piece by piece. The upper building top (the portion that tilts) maintains sufficient integrity and his measured data over several seconds shows such an excellent fit to the constant acceleration downward, that the basic physics can be applied with a clear conclusion.

Even billiard balls bend a little.

2) His second conclusion is that the speed of the fall is such that the lower structure can't be resisting. ...

That looks like a misstatement or misreading to me. In WTC1, the lower structure resists, just at only 1/3 as much as it resisted while holding the normal static load. Something lowered the resistance of the lower structure by at least 2/3's (by quite a bit more, actually, if the lower level had a significant safety factor), and that something was not the impact of the upper section, because the upper section was only imposing a TOTAL force of 1/3 of its usual gravitational weight on the lower structure (which 1/3 the [supposedly] heretofore lower structure could very easily support.)

[ThePythonicCow]

Re: Goodbye, Mr Roberts

Confucius replied:"Don't you see the man is green color? He is a grasshopper. He will die at the end of autumn. How can you convince someone there are four seasons, while his whole life has only three seasons?"

I'm no Confucius, skyson. My waters run more shallow, more murky and more turbulent. Thus it shall be, until such time as it isn't.

[c1ue]

Re: Goodbye, Mr Roberts

Quote:

Originally Posted by c1ue 2) His second conclusion is that the speed of the fall is such that the lower structure can't be resisting. ...

That looks like a misstatement or misreading to me. In WTC1, the lower structure resists, just at only 1/3 as much as it resisted while holding the normal static load. Something lowered the resistance of the lower structure by at least 2/3's (by quite a bit more, actually, if the lower level had a significant safety factor), and that something was not the impact of the upper section, because the upper section was only imposing a TOTAL force of 1/3 of its usual gravitational weight on the lower structure (which 1/3 the [supposedly] heretofore lower structure could very easily support.)

The end of the Chandler paper is quite clear - not sure what you are implying:

Chandler paper end itulip format.jpg

As I noted before, this is the exact same fallacy as skyson keeps trying to peddle - to wit - that it is momentum that provides the energy.

It is not. It is gravitational potential energy. Gravitational potential energy is converted to kinetic energy by falling.

Kinetic energy is not the same as weight.

If Chandler were to calculate the gravitational potential energy of the upper floors then compare with the strength of the steel structure for varying lengths of propagation time, this would be more sensible.

Instead, he assumes the lower floors to be ideal conductors of force - a completely false assumption for a large moving object, especially so for the forces involved.

The conclusion to his paper is incorrect.

As an example let's calculate the force of the weight of the upper floors vs. the force of the upper floors falling 3 meters.

Assume 20,000 tons = 18.14 x 10exp6 kilograms

(Weight) mass * gravity = 18.14 x 10exp6 kg times 9.8 m/s-squared = 177.8 x 10exp6 Newtons

For kinetic energy of upper floors, we need velocity.

Velocity in free fall is: v-squared = gravity x distance = 9.8 x 3 = 29.4 (m/s)squared

KE = 1/2 mass * v-squared = 14.7 * mass = 266.7 x 10exp6 Newtons

The identical mass falling 3 meters exerts a Force 1.5x that of the exact same mass at rest, and furthermore this force is applied instantaneously as opposed to built up over a long period of time (WTC construction period).

Chandler doesn't get it. Skyson doesn't get it. And apparently you don't get it.

[Ghent12]

Re: Goodbye, Mr Roberts

Once you get the physics clear in your mind, (C) and (F) are rather obvious.

Only obvious if you start with the assumption that steel cannot be destroyed, or some similarly asinine assumption which you apparently are operating on.

Let's restart from the -6.31 m/s2 acceleration and see if I understand what you and Chandler are saying. Let's plug and play with different values. You said -3.2 m/s2 "indicate[s] less complete removal of lower material prior to the falling upper material impacting with it." Okay, so that means a falling acceleration of exactly 0.0 m/s2 would logically indicate, according to your physical world view, 'a complete non-removal of lower material prior to the falling upper material impacting with it.' Additionally, an acceleration of -9.81 m/s2 or greater would indicate no resistance from the lower structure.

Let's see...
Using Chandler's model of mg - N = ma, an a of exactly zero (see above) would mean a 100% application of the normal static force rather than just 36%. Yet clearly the structure should be able to support 100% of its static load, because it was doing so prior to the collapse. Therefore it is impossible under this physical world view for any structure to ever collapse, because any non-accelerated impact would simply apply the normal load over again. In fact, any structure designed to withhold a given weight should be able to withstand that same weight dropped from any height because the maximum force applied would just be the normal force.

This is Chandler's physical model and his view of the physical world. It neglects at least two very key elements of kinetics and kinematics; one which c1ue is focusing on and one which I focus on. Namely, it neglects energy involvement and the properties of materials when subjected to such energy over the time span in question.

[ThePythonicCow]

Re: Goodbye, Mr Roberts

The end of the Chandler paper is quite clear - not sure what you are implying:

You seem to be referring to the following paragraph, quoted from the end of Destruction of the World Trade Center North (pdf) by David Chandler (Journal of 9/11 Studies - Feb 2010). The image in your post is difficult to view, probably due to iTulip forum software compressing it.

Having assumed the existence of an indestructible falling block, with or without accretion, we have demonstrated that, given the observed acceleration, such a block could not possibly have destroyed the lower section of the building. When we turn to the video evidence we see that even the hypothesized existence of a persistent upper block is a fiction. Videos show that the section of the building above the plane impact point was the first section to disintegrate. It was significantly reduced in size prior to the onset of destruction of the lower section of the building. Once the roof line descends into the debris cloud there is no further evidence even of its continued existence. Whether or not it was completely destroyed early in the collapse is a moot point. We have shown that even if it continued to exist intact, it could not have played a significant role in the destruction of the building. A small section of a structure, consisting of a few floors, cannot one-way crush-down a significantly larger lower section of same structure by gravity alone.

I see nothing in this quote claiming (what you claimed was Chandler's second conclusion) that "the speed of the fall is such that the lower structure can't be resisting." I don't know why you present the above paragraph from the end of Chandler's report, apparently in evidence of your assertion that he made such a claim. The lower structure in WTC1 did resist (during the time period of Chandler's analysis), just not nearly as much as it normally resisted the static load on it. I doubt that Chandler claimed otherwise. I still hold your claim that Chandler presented this as his second conclusion is incorrect.

[ThePythonicCow]

Re: Goodbye, Mr Roberts

As I noted before, this is the exact same fallacy as skyson keeps trying to peddle - to wit - that it is momentum that provides the energy.

It is not. It is gravitational potential energy. Gravitational potential energy is converted to kinetic energy by falling.

If I understand this and the remainder of that post correctly, you are discussing the various kinds of energy and calculating that there is enough energy present to cause the collapse. You carefully demonstrate that a falling mass has greater impacting energy than the same mass at rest.

I entirely agree with all that.

We have an object with potentially enough energy to collapse another object, colliding with that other object. General collapse ensues.

Given those observations then, yes, no doubt, the most obvious and likely explanation is that the collision caused the collapse. Yup.

Looking at the evidence and analysis which you are considering, I entirely agree that your explanation of the collapse mechanism is the most plausible. No nano-thermite, death star rays or arch-angels required.

Let's take this one step at a time. Have I demonstrated at least a basic but adequate understanding of your understanding of this matter?

[skyson]

Re: Goodbye, Mr Roberts

As I noted before, this is the exact same fallacy as skyson keeps trying to peddle - to wit - that it is momentum that provides the energy.

It is not. It is gravitational potential energy. Gravitational potential energy is converted to kinetic energy by falling.

Kinetic energy is not the same as weight.

...............

The identical mass falling 3 meters exerts a Force 1.5x that of the exact same mass at rest, and furthermore this force is applied instantaneously as opposed to built up over a long period of time (WTC construction period).

Chandler doesn't get it. Skyson doesn't get it. And apparently you don't get it.

I don't know where you get that impression. As I have repeatedly stated: my focus is after the "initiation of collapse", which clearly involves only kinetic energy.

It was you who did not get what my position was.

If you are interested, see my post #170, as well as Ghent12, and give me your answers.

[skyson]

Re: Goodbye, Mr Roberts

Only obvious if you start with the assumption that steel cannot be destroyed, or some similarly asinine assumption which you apparently are operating on.

Let's restart from the -6.31 m/s2 acceleration and see if I understand what you and Chandler are saying. Let's plug and play with different values. You said -3.2 m/s2 "indicate[s] less complete removal of lower material prior to the falling upper material impacting with it." Okay, so that means a falling acceleration of exactly 0.0 m/s2 would logically indicate, according to your physical world view, 'a complete non-removal of lower material prior to the falling upper material impacting with it.' Additionally, an acceleration of -9.81 m/s2 or greater would indicate no resistance from the lower structure.

Let's see...
Using Chandler's model of mg - N = ma, an a of exactly zero (see above) would mean a 100% application of the normal static force rather than just 36%. Yet clearly the structure should be able to support 100% of its static load, because it was doing so prior to the collapse. Therefore it is impossible under this physical world view for any structure to ever collapse, because any non-accelerated impact would simply apply the normal load over again. In fact, any structure designed to withhold a given weight should be able to withstand that same weight dropped from any height because the maximum force applied would just be the normal force.

This is Chandler's physical model and his view of the physical world. It neglects at least two very key elements of kinetics and kinematics; one which c1ue is focusing on and one which I focus on. Namely, it neglects energy involvement and the properties of materials when subjected to such energy over the time span in question.

You are confusing me here. If something ever dropped from any height, would that render "a" positive? If "a" = 0, does it mean the structure has no acceleration?

If so, Chandler's conclusion is not challenged, because his analysis started when the structure moving at speed of zero.

[ThePythonicCow]

Re: Goodbye, Mr Roberts

Only obvious if you start with the assumption that steel cannot be destroyed, or some similarly asinine assumption which you apparently are operating on.

I'm thinking of writing a Greasemonkey script to delete the first sentence of your posts when I read them. They always seem to contain some outlandish, often insulting, dig at something or someone or other.

Skipping right along ...

Let's restart from the -6.31 m/s2 acceleration and see if I understand what you and Chandler are saying. Let's plug and play with different values. You said -3.2 m/s2 "indicate[s] less complete removal of lower material prior to the falling upper material impacting with it." Okay, so that means a falling acceleration of exactly 0.0 m/s2 would logically indicate, according to your physical world view, 'a complete non-removal of lower material prior to the falling upper material impacting with it.' Additionally, an acceleration of -9.81 m/s2 or greater would indicate no resistance from the lower structure.

Yes - that sounds exactly right to me (though I will confess to a fear that I will be eating my words of agreement sometime soon.)

Let's see...
Using Chandler's model of mg - N = ma, an a of exactly zero (see above) would mean a 100% application of the normal static force rather than just 36%. Yet clearly the structure should be able to support 100% of its static load, because it was doing so prior to the collapse. Therefore it is impossible under this physical world view for any structure to ever collapse, because any non-accelerated impact would simply apply the normal load over again. In fact, any structure designed to withhold a given weight should be able to withstand that same weight dropped from any height because the maximum force applied would just be the normal force.

Well, as I am sure we agree, structures can collapse.

Distinguishing three types of collapse should be sufficient to resolve the apparent conundrum you present. Consider a two story wooden frame building with termites eating just one of the two stories. Consider these three types of collapse:

1. In Type One, the termites eat the first story until it collapses, bringing down the second story on top of it.
2. In Type Two, the termites eat just the second story until it collapses, crushing the first story below it.
3. In Type Three, the termites eat just the second story until it collapses. That by itself would not have been sufficient to collapse the building, so the owner (trying to collect on an insurance claim that covers termite damage) planted dynamite in the first floor, triggered to go off when the second floor falls on it.

According to the official story, the WTC collapses are Type Two. Your conundrum is Type One. I claim that Type Three is closer to the WTC situation.

Chandler's analysis applies in the situation where you are analyzing the apparent destruction of one thing (WTC1 lower floors, for example) by throwing, dropping or otherwise colliding something else (WTC1 upper, say) with it. In that situation, if you are fortunate enough to be able to accurately measure the position of the moving object during the time that the impacted object does indeed collapse, you can then calculate the force which the collision imparted on the impacted object. If you happen to know enough else about the impacted object to show that the ACTUAL TOTAL FORCE imparted was not enough to initiate general collapse, then you have demonstrated that something else must have caused the collapse.

To repeat myself, I refer here to the ACTUAL TOTAL FORCE that was imparted as measured by the change in the moving body's velocity. I am not referring to what could have been imparted given the velocity and mass of the moving object.

If I fire a 50 caliber gun at a thick steel wall, the bullet imparts all its energy to the wall. If I fire that gun at what looks to be a steel wall, but turns out to be a piece of paper, the bullet doesn't impart much energy to the paper, which fact I could determine by noticing that the bullet didn't slow down much while piercing the paper.

Here's an interesting story for you which might explain this.

Imagine I build a house for my dog. I sit on top of the doghouse to test it's strength. The house holds. I then jump up and down on the house. The house collapses and I break a leg. This seems like an open and shut case of my stupidity. Clearly the house collapsed because I jumped on it, right?

Well, the plot thickens. It turns out that a relative of mine who is living with me really hates my guts. I guess he thinks I spend way too much time on iTulip instead of playing computer games with him. He helped that doghouse collapse by secretly tying a rope to its frame and pulling the rope just as I was jumping. He was quite hoping that I'd hurt myself and video taped the whole scene. He posts that video on YouTube, with a comment on what an idiot I was.

A bored physics student analyzes that video frame by frame (when he should have been studying for his upcoming thermodynamics exam.) He then posts in a YouTube comment that my jumping did NOT cause the collapse of the doghouse and explains why. His thermodynamics professor (when he should have been grading exams) reads that YouTube comment, recognizes that it is his student who wrote it, and flunks him, without even reading the students sorry excuse for an exam.

The student was right!

The student analyzed my vertical position, velocity and acceleration as I was jumping. He showed that I was only applying a force of only about 1/3 of my weight on the doghouse as it was collapsing. Clearly by jumping up and down I was potentially applying more force than just my weight, and clearly the doghouse might have collapsed under such an additional force. But his analysis showed the force I actually was applying, as the doghouse was collapsing, was but a third of my weight, which (absent some other reduction of the doghouse's structural capacity) was not enough force to collapse the doghouse.

Something else weakened the doghouse after I sat on it, before or just as I jumped on it.

This is Chandler's physical model and his view of the physical world. It neglects at least two very key elements of kinetics and kinematics; one which c1ue is focusing on and one which I focus on. Namely, it neglects energy involvement and the properties of materials when subjected to such energy over the time span in question.

If one method of analysis shows something could not happen, then just because some other method of analysis shows that something is plausible does not make the first analysis wrong.

In other words, I'm sorry (*) I'm not using your material property analysis or c1ue's total energy available analysis, but I don't need them. I've already shown (well, Chandler has) that which I wished to show.

(*) a white lie ;).

[Ghent12]

Re: Goodbye, Mr Roberts

If one method of analysis shows something could not happen, then just because some other method of analysis shows that something is plausible does not make the first analysis wrong.

In other words, I'm sorry (*) I'm not using your material property analysis or c1ue's total energy available analysis, but I don't need them. I've already shown (well, Chandler has) that which I wished to show.

(*) a white lie ;).

It matters when the method of analysis is improper for the application. In order to rule that there was insufficient energy to destroy a structure, you need to understand the energy involved and the strength of the structure. Chandler's high school physics don't attempt either.

In fact, according to his force-only analysis, no structure could ever collapse in history unless there was a demolition. After all, the maximum acceleration would be gravity, which would only impart up to 100% of its static force, i.e. the normal force. No matter what height it's dropped from, no matter what velocity it reaches before impact, his erroneous conclusion is that the smaller section can't destroy the lower section.

If you persist in relying upon Chandler's physical model of reality, instead of the generally agreed-upon model used by essentially all accredited engineers and physicists, then I cannot help you.

[ThePythonicCow]

Re: Goodbye, Mr Roberts

It matters when the method of analysis is improper for the application. In order to rule that there was insufficient energy to destroy a structure, ...

Not what he ruled. There might have been sufficient energy available. As you yourself noted elsewhere above, Chandler did not compute how much energy was available, much less make claims as to whether it was enough or not.

plonk

[ThePythonicCow]

Re: Goodbye, Mr Roberts

If I fire a 50 caliber gun at a thick steel wall, the bullet imparts all its energy to the wall. If I fire that gun at what looks to be a steel wall, but turns out to be a piece of paper, the bullet doesn't impart much energy to the paper, which fact I could determine by noticing that the bullet didn't slow down much while piercing the paper.

This example deserves further comment.

Imagine that someone painted a thin cardboard wall to look like a thick dense teak wood wall and that we fired a .45 caliber bullet at it. We observe this using a high speed camera. If one tracks the change in velocity (aka the acceleration) of the bullet as it enters the target, one can determine that the target resisted the bullet less than we expected, given that we thought we were firing at thick teak wood. The bullet will not have slowed up enough. We don't know from just this that the wall was thin cardboard, but we can conclude immediately and with confidence that it was not structurally sound thick dense teak wood.

The key is that by Chandler's analysis, one can measure how strong was the stationary target, when hit and penetrated or destroyed by an object in motion. One does this by observing the impact on the acceleration of the moving object. The greater the negative change to the moving objects acceleration, the more force was generated during the impact. This is simply an application of the classic vē = 2as, F = ma and ft = mv equations.

Chandler shows with his observations that the force generated by the impact of the upper and lower portions of the WTC1 tower and WTC7 building was substantially less that the static load of the upper portion (WTC1) or practically zero (WTC7).

Since we know from observing the buildings prior to their collapse that the lower portions could support the weight of upper portions, therefore something other than the force of impact from the upper portions caused the collapses the lower portions. The force of impact was substantially less than the force of the gravitational load, which we know the lower building portions could support, right up to the time they collapsed.