http://www.9-11commission.gov/report/911Report.pdf

Anyone care to challenge any of the assertions of the 9/11 Commission report? Please give page number, quote and an evidenced refutation.

Kat Dorman wrote:

psikeyhackr wrote:I put up a physical model that doesn't collapse.

Neither will 4 bricks dropped on 29. Shall we have a parade?

Of course, it's another example that you are wrong.

But it is not a very useful example because of the square cube law.

http://en.wikipedia.org/wiki/Square-cube_law

That is why my model needs the WEAK paper loops to collapse properly.

Enough loops get crushed to absorb the kinetic energy. If I had used slices of metal conduit instead it still would not have collapsed but the conduit would be so strong that the test would be totally meaningless. But it cannot be made weak enough to completely collapse but still be strong enough to support the static load.

So until someone builds a physical model that can completely collapse all of the chatter is just about CARTOON PHYSICS.

http://www.youtube.com/watch?v=mTqwXb98giY

So engineering schools have spent NINE YEARS talking trash and making themselves look silly. So now they must keep everyone from understanding grade school physics for the next 1000 years. It's the Physics Reich. Heil Cartoon Physics.

psik

PS - Happy New Year of BAD PHYSICS!

Kat Dorman wrote:You not only don't understand what potential energy is (ref this thread), you don't know what mechanical work is. Just like PE, there is a simple formula to use. You only need multiply two numbers together! I'm aware of your fundamental distrust of anything mathematical or remotely scientific, instead preferring your own imagination of how things must be, but this is really simple arithmetic.

Work = Force x Distance

That equation assumes the force can MOVE some mass over that distance.

The towers stood for 30 years while being under the influence of gravity all of that time. So the "Net Force" was not just Gravity. The supports designed to hold up the building were canceling out the effect of gravity. The force of gravity was not being applied over any distance.

The supposed collapse scenario would mean the falling mass could destroy all of the supports which got stronger hand heavier all of the way down. But then you don't even expect accurate data about that from Official Sources.

I could do two potential energy calculations on my model. From the mass to be dropped to that top of the stationary portion. Or from the falling mass to the base of the model. But the kinetic energy on impact is determined by the fall through EMPTY SPACE. Computing Potential Energy through distance that is NOT EMPTY is useless mathematical delusion. And yes that is how our schools teach physics. But none of those schools have built a model that can collapse completely now have they?

psik

Kat Dorman wrote:psikeyhackr wouldn't know whether or not I'm a CD proponent, or adhere to a position he's too afraid to commit to, because he simply assumes that anyone arguing the physics of models or disagreeing with him must necessarily be in mindless lockstep with some monolithic official story. It's pathetic. He has accused people who do believe in assisted demolition and have had the guts and integrity to say so - where he won't take such a stand, as seen above - of the very same faith in the official story as he did with me in his last post.

When have I talked about Controlled Demolition?

I don't know how the towers were destroyed and don't much care who did it. After NINE YEARS this is the problem of the engineering schools. Like Purdue that can make a SCIENTIFIC SIMULATION where the core columns don't move when a 140 ton airliner crashes into a skyscraper at 440 mph.

I have just been saying that airliners could not do it because the top of the north tower could not crush everything below and that is what my model is designed to demonstrate. My comments about the 9/11 Religion are about everyone that BELIEVES the top of the north tower could come straight down and destroy the rest. I don't recall saying anything specifically about you.

Not because I am such a nice guy of course but simply because I DON'T GIVE A DAMN.

psik

Psikeyhackr - you still haven't answered my question: what is the highest static load each of your paper loops is capable of carrying? One washer? Two - three - more?

Weaver wrote:Psikeyhackr - you still haven't answered my question: what is the highest static load each of your paper loops is capable of carrying? One washer? Two - three - more?

Between 12 and 17 washers, from what I can tell.

Durro wrote:Got it out of your system now Kat ?

No, but either I'll play nice or go away.

Kat Dorman wrote:

Weaver wrote:Psikeyhackr - you still haven't answered my question: what is the highest static load each of your paper loops is capable of carrying? One washer? Two - three - more?

Between 12 and 17 washers, from what I can tell.

I tested the loops under static loads. Single loops collapse with a minimum of 12 loops and a maximum of 17 I tested at least 20 loops but I didn't keep a record of how many collapsed with how many washers, just the minimum and max. That is why I use 11 single loops. I originally tried the tower with 19 double loops but after standing over night the bottom two double loops collapsed. So I went to 5 triples, 17 doubles and 11 singles.

The thicknesses of the washers vary. I sorted them and put the thickest at the bottom. Two if the thickest washers are the same as three of the thinnest. The average weight is 1.7 oz So the thickest should be 2.1 and the thinnest 1.4 oz.

So this nonsense has been going on for NINE YEARS and people claiming to know physics all over the world haven't been demanding accurate info on the distribution of steel but the CN Tower shows how the support steel would need to be arranged. But the WTC would have even more of a wind load problem since it did not get narrower toward the top.



psik

psikeyhackr wrote:

Kat Dorman wrote:

psikeyhackr wrote:I put up a physical model that doesn't collapse.

Neither will 4 bricks dropped on 29. Shall we have a parade?

Of course, it's another example that you are wrong.

You mean I'm wrong in saying that 4 bricks dropped on 29 will arrest? Well, if that's the case, I submit 4 bricks dropped on 29 as my collapsible physical model. Since you already know it will, I don't actually need to build it. Guess we're done here.

But it is not a very useful example because of the square cube law.

http://en.wikipedia.org/wiki/Square-cube_law

That is why my model needs the WEAK paper loops to collapse properly.

The square-cube law refers to the ratio of surface to volume under uniform length scaling. Perhaps you could elaborate on how this applies. I would say a principle that counts much more, perhaps infinitely more, is the simple property that both bricks and your paper loops exhibit: they require more energy to crush than is lost as PE by the impacting load through a drop of the same height. Pay close attention to that last statement, if you will; it's what I've been saying to you from the beginning, it's never changed one iota. I try rephrasing it, repackaging it, giving concrete examples, doing calculations, making graphs, citing sources, etc, but the message is always the same.

Enough loops get crushed to absorb the kinetic energy.

And that amount exceeds the PE liberated by crushing through a unit drop distance, therefore it will arrest. That's why it arrests. The reason there is no expectation of arrest with steel columns is that they have the opposite property: more PE is liberated dropping through the crushing distance than is required to do the crush. This according to a titan in the international engineering mechanics community, and you've done no corresponding analysis to show otherwise. Paper loops (by definition) cannot prove or disprove anything about the dynamic properties of steel columns.

If I had used slices of metal conduit instead it still would not have collapsed but the conduit would be so strong that the test would be totally meaningless.

Why metal conduit instead of filament? For the perimeter at the story height scale of your model, the filaments would be hollow rods less than 0.07" in diameter, with average wall thickness of between 1/5th and 1/50th of that. And its not like there would be 236 of those plus 47 beefier filaments (if you can call anything with wall thickness measured in mils "beefy")... there would be precisely as many to achieve a DCR in accordance with estimates for a tower but based on the masses of the washers.

I would pay very close attention to the behavior of such a model under a drop height of one level.

Even so, if your metal conduit were tall and slender enough to buckle (making for a very tall scale model), and well-loaded metal plates were used as slabs instead of metal washers, there's very likely a DCR range in which it will be self-supporting yet progressively collapse from a drop height of only one story.

But it cannot be made weak enough to completely collapse but still be strong enough to support the static load.

See above. But I've told you all this before. I won't make any suppositions about what you did with that information since I'd rather play nice than go away (for now). I'll explain it to you again in a bit.

So until someone builds a physical model that can completely collapse all of the chatter is just about CARTOON PHYSICS.

There's no possibility that it's just physics and you're wrong? Rhetorical question. But, if you'd be so kind to answer this: Have you ever considered the possibility that you're wrong? I've asked you straight out what would happen if someone did build "a physical model that can completely collapse" - would you admit you're wrong about anything you've claimed - and you declined to answer.

-----


When you say "a physical model that can completely collapse", I realize this is informal discussion and that there are constraints on the model that are implied, such as "self supporting" and "top 15%", but you've refused to specify any additional constraints. Therefore, I consider your challenge met by my previous submission of a house of cards collapse. Whether or not you accept it is unimportant, it meets your stated criteria in every way.

- physical model
- self-supporting
- collapses completely
- (no more than) the top 15% as driver

Moreover, it resembles the towers in physical appearance/layout and apparent collapse mode far more than your model.

- tall rectangular box aspect
- interior and exterior vertical supports
- unconstrained 3D dynamics
- initial defect but NO initial drop
- mass shedding

It's done.

Feel free to formally move the goalposts.

psikeyhackr wrote:That equation assumes the force can MOVE some mass over that distance.

Yes, of course. Here's where I'm going to respectfully ask you to put your thinking cap on.

If a support has been crushed, the load has dropped the crushing distance.

A static load within capacity will not cause the supports to collapse, so at static equilibrium there is no motion, no PE loss, no work done. But if a load is dropped, it already has energy of motion. If this is sufficient energy to deform the support, there will be loss of elevation and therefore loss of PE versus the static reference height. The PE is not subtracted before the crushing occurs, it is subtracted AS the crushing occurs.

How can a load begin to move when initially static and supported? When the capacity has been degraded such that the support can no longer hold the load; i.e., when it ceases to be a support.

Anything that can support a given static load will require more energy to crush than is lost in PE by the corresponding crush distance FOR SOME LENGTH, that's why it can support the load. Some types of supports have a well defined yield stress at which the situation reverses and less energy is consumed in crushing than is liberated in dropping. Vermicelli strands break at about 10% axial shortening with ends free to rotate. That means any impactor with KE sufficient to break the strand will then have 90% of the strand's length to drop with NO resistance.

If the load can get over the strain potential barrier, it will continue to fall.

A steel column under axial deformation will not reach this condition until well into the plastic deformation phase. If it is deformed past that point, it will no longer be able to support the load even statically so the load will drop. Next iteration.

The one thing your experiment definitely proved: Paper loops in your configuration require more energy to crush than is lost in PE by the load in dropping the same distance. Therefore it arrests, therefore it's not a suitable analog for steel columns as used in the towers according to undergrad structural engineering textbook knowledge, as well as by direct calculation from foremost authorities on the subject.

You can always try to prove that steel columns of the configuration in the towers do not have this property. Good luck. There's been an awful lot of physical experiments with real steel columns in the last 100 years that say you're wrong. Paper loops don't cut it.

The towers stood for 30 years while being under the influence of gravity all of that time. So the "Net Force" was not just Gravity. The supports designed to hold up the building were canceling out the effect of gravity. The force of gravity was not being applied over any distance.

All correct. See above for why it's so and why this is irrelevant to the collapse conditions.

The supposed collapse scenario would mean the falling mass could destroy all of the supports which got stronger hand heavier all of the way down.

Yes, yes, yes. See above. All of my statements apply to constant DCR/FOS/capacity all the way down unless otherwise noted.

But then you don't even expect accurate data about that from Official Sources.

No, I don't. But I do expect accurate mass breakdown of the Saturn V to the kilogram. Where is it? A moon launch vehicle and we don't know the exact masses? How many years has it been?

I could do two potential energy calculations on my model. From the mass to be dropped to that top of the stationary portion. Or from the falling mass to the base of the model.

This is why you distrust math. Stop stumbling around and frame the problem according to simple principles of mechanics as best as possible and then execute the correct math. The PE is subtracted when the distance is traveled. The distance is traveled at a rate governed by the instantaneous force and load it acts upon. The mass changes as mass is accreted and/or shed. Mechanical work is done in crushing as the crushing occurs. Energy is lost to inelastic accretion as it occurs. Other sinks can be assumed, with or without physical motivation so long as they are reasonable and documented. It's how mechanics is done, and how it's been done since Newton (a name you like to drop).

But the kinetic energy on impact is determined by the fall through EMPTY SPACE. Computing Potential Energy through distance that is NOT EMPTY is useless mathematical delusion.

NO. IT. IS. NOT. It's perfectly valid and the ONLY correct thing to do. My analytical and computational models do not have a concept of space that is 'empty' or 'filled', only of sources and sinks (in an energetic formulation) or forces (in F=ma eqs of motion) and the bodies and distances to which they apply.

And yes that is how our schools teach physics.

Thank goodness, because it is correct. The rest of the untold number of institutions and individuals who know that it is correct, versus you.

If an object loses elevation, it loses gravitational potential, period. It doesn't matter whether the space below is empty or not, that's an absurd notion. The top bearing plate of a 50-ton press loses the same PE over its travel downward whether it's crushing metal scrap or if there's nothing but empty space.

But none of those schools have built a model that can collapse completely now have they?

Not to my knowledge, and I do find that curious. It would seem to be a good engineering challenge in an undergrad program.

I said I would explain the difference in static capacity and energy to crush, one more time. I don't know why. I believe it will be greeted with "TALK,TALK,TALK,TALK,TALK,TALK,TALK,TALK,TALK,TALK" but, knowing that, it's no one's fault but my own that time is being committed to ferreting out truth from BS. A lot of people subscribe to the BS, and I don't owe them a damn thing, but here goes.


The graphs below illustrate the difference between a support's static capacity and the energy required to crush it, and the relation between the two. The graphs are load-displacement graphs for three different contrived cases of abstract supports, the same type of graph Bazant supplied in his paper to describe the load response of a typical steel column in axial compression (posted twice several pages back).

The horizontal axis is displacement of an imposed load through distance to fully compact a crushing support. The vertical axis is the resisting force provided by the support. Units are fraction of the total support crushing distance h and multiples of a hypothetical nominal design load mg for horizontal and vertical, respectively. These are natural and convenient units for the problem, which is expressed independent of any particular mass or support height.

Each graph has areas shaded in a color and a gray texture. The latter will be explained in a moment. The height of the color portion represents the resistive force given by the support at each position as it's crushed, a simple graph of force versus position. There are only two force values, high/low (or OK/fail), to eliminate irrelevant detail. The force is higher than the imposed load in the first segment of travel then drops at some point to less than the load.

Static Capacity:
The support's maximum static capacity is the high value at the beginning. Units of force.

Crush Energy:
The work (mechanical energy) done in fully crushing the support is given by W = ∫F(h)dh which is the shaded area under the force curve. Units of energy.

The static capacity says what load can be supported by an intact member. The crushing energy is PART of what dictates motion over time of a collapse in progress. Two different things that cannot be rolled together into the single psikeyhackr criteria of "as weak as possible". Turning to the graphs:





Each of these cases represent a support which, while intact, has the capacity to hold a static load of mg with some amount of reserve. None of these supports will fail with a static load of mg, but all will fail and even crush completely if the load is impacting at sufficient (as yet undetermined) velocity.

Case 1 at the top depicts a support which will yield under a static load 1.5 times the design load, so I'll loosely refer to it as having a factor of safety (FOS) of 1.5. Case 2 has a greater static capacity with an FOS of 2.0, Case 3 greater still at FOS of 2.5.

Clearly, the first of the three is weakest in terms of static capacity, having only a 50% margin of safety, but we'll see that it is the strongest in terms of energy to crush - which is the quantity of interest in a progressive collapse. Case 1 provides its peak resistive force over the first half of travel (even though it's being crushed) whereas Case 2 has peak capacity for 10% of the travel; Case 3 is a blip at only 2%.

Recall the shaded areas are the work done in crushing - force times distance - and it's obvious that Case 1 consumes much more energy in crushing because it maintains its somewhat lower initial capacity for a much longer period of travel, then drops to a lower capacity which is still 50% of the load. By contrast, supports in Cases 2 and 3 fail abruptly and more decisively, dropping quickly to very low capacity (zero in Case 3) for most of the travel.

Case 1 could be thought of as an approximation to stiff gel eventually going into shear fracture. Case 2, a steel column. Case 3, a glass rod. Just to put faces on the abstract properties.

Now for the rectangular gray bands. Each of these have the same area as the regions shaded in color, therefore represent the same amount of energy. The height of this rectangular gray band is the equivalent average resistive force over the entire crushing distance. If a support is crushed to full compaction, the dynamics at the beginning and end of this interval are the same as if there were this average force acting on the impacting load the entire time.

Note in Case 1 that the average force is equal to the load mg, meaning there is (over the entire displacement) no net average force acting on the impacting load. Gravity pulls downward, and the support pushes back by exactly the same amount. What would actually happen is the load would decelerate in the first half of travel, then accelerate in the last half. On the whole these alternating regions would balance and the load neither gain nor lose velocity as the collapse progresses were it not for losses due to inelastic collision. If the load impacts with insufficient momentum to crush a Case 1 support past half compaction, the collapse will arrest without the support being fully crushed.




In summary, these three cases show how static capacity has no direct relation to energy of crushing. The support which holds the greatest load crushes most easily, and vice-versa.

psikeyhackr wrote:Single loops collapse with a minimum of 12 loops and a maximum of 17 I tested at least 20 loops but I didn't keep a record of how many collapsed with how many washers, just the minimum and max.

You mean there aren't detailed accurate records of the capacity at each level?

The thicknesses of the washers vary. I sorted them and put the thickest at the bottom. Two if the thickest washers are the same as three of the thinnest. The average weight is 1.7 oz So the thickest should be 2.1 and the thinnest 1.4 oz.

You're doing linear interpolation? You mean there is no accurate table of masses for your own experiment??? Hahahahah...

psikeyhackr wrote:When have I talked about Controlled Demolition?

You don't, and as I pointed out in the passage you quoted, I find that cowardly. All you do is deny principles of elementary physics which are not up for debate, and proclaim via incredulity that it can't happen due to impact/fires/gravity when the science says exactly the opposite.

I don't know how the towers were destroyed and don't much care who did it.

It shows. I hope your cheering sections at various forums are clear on that.

After NINE YEARS this is the problem of the engineering schools.

In less than two days, a first approximation to the collapse was formulated. It's only improved since then. You've done absolutely nothing to advance the science.

Like Purdue that can make a SCIENTIFIC SIMULATION where the core columns don't move when a 140 ton airliner crashes into a skyscraper at 440 mph.

To hell with Purdue and their simulation.

I have just been saying that airliners could not do it because...

Drum roll...

...the top of the north tower could not crush everything below...

Unsupported assertion which the best engineering analyses compellingly show to be false.

...and that is what my model is designed to demonstrate.

But it does not for the myriad detailed and sound fundamental reasons I've provided. So you've got nothing, except a lot of time wasted on forums proclaiming falsehoods.

My comments about the 9/11 Religion are about everyone that BELIEVES the top of the north tower could come straight down and destroy the rest. I don't recall saying anything specifically about you.

Another cowardly discussion tactic. I believe "the top of the north tower could come straight down and destroy the rest" so you are not only talking TO me when you say it, you're talking ABOUT me. Have the integrity to take less wishy washy stands, if you're so certain of your position.

Not because I am such a nice guy of course but simply because I DON'T GIVE A DAMN.

No comment.

Kat Dorman wrote:

psikeyhackr wrote:Single loops collapse with a minimum of 12 loops and a maximum of 17 I tested at least 20 loops but I didn't keep a record of how many collapsed with how many washers, just the minimum and max.

You mean there aren't detailed accurate records of the capacity at each level?

The thicknesses of the washers vary. I sorted them and put the thickest at the bottom. Two if the thickest washers are the same as three of the thinnest. The average weight is 1.7 oz So the thickest should be 2.1 and the thinnest 1.4 oz.

You're doing linear interpolation? You mean there is no accurate table of masses for your own experiment??? Hahahahah...

My experiment did not cost $300,000,000 and require the coordinated actions of thousands of people to construct and did not have to be designed like people's lives depended on it ahead of time.

It did not have to withstand 100 mph winds.

But then it did not collapse like something much stronger supposedly did. Since it behaved in a physically rational manner the unknowns don't really need to be investigated though anyone that wants to can duplicate it, more or less. If they buy a different brand of paper the results could vary somewhat. But only one person has reported duplicating the experiment. He admitted the results were the same as mine. He seemed disturbed though and has not responded since September.

But the model is being used to demonstrate the physical irrationality of something else. So maybe it bothers people that have decided what they WANT TO BELIEVE. It is not my fault that you can't build anything reasonable that does collapse. It's just physics. It does not care what anybody BELIEVES.

psik

psikeyhackr wrote:It is not my fault that you can't build anything reasonable that does collapse. It's just physics.

I submitted a physical model that someone else built which collapses. Your challenge has been met because physics does not care who builds the model. Acknowledge your challenge has been met or move the goalposts, one of the two.

To hell with Purdue and their simulation.

http://www.youtube.com/watch?v=cddIgb1nGJ8

Well I am somewhat inclined to agree with that but supposedly it is a well regarded school.

It got 8,000,000 views on Youtube. I haven't gotten my first million.

So how do they not only make such a DUMB MISTAKE but where is the criticism of such absurdity?

psik

Purdue... I'm not really in a position to comment on their simulation. All I can say is I wouldn't be surprised if it wasn't worth a bucket of spit. Fine institutions can produce crap, for sure.

So how do they not only make such a DUMB MISTAKE but where is the criticism of such absurdity?

I've seen some, but not from official corners. There is a lack of criticism of "official" efforts from "official" circles all around. I agree that's weird, and not good. I've developed my own criticisms of Bazant and Seffen, criticisms which challenge them on their own turf, and seen the work of a few others which do the same. No one with so-called creds (unless you count Benson's avalanche model), though.

But it's weirder that I spend a lot more time these days tackling your misconceptions than theirs. Think about that.

Bazant's model is NOT a model of the tower collapses, it's a bounding case. Mixed crush direction, even using Bazant's formulation, is almost assured for anything but the narrowest parametric ranges, coincidentally containing the values Bazant chose rather arbitrarily to prove one-way crush. Seffen found that momentum-only converges on g/2, whereas Bazant and I say g/3. We're right, I'm pretty damn sure, and Seffen is wrong, but Bazant has no comment. Bazant also has no comment on WTC7, incidentally. The NIST physics simulation of WTC7 fails on a number of basic kinematic checks and apparently has nothing to do with the mechanics of the actual collapse. No one has produced an engineering mechanics analysis of the actual collapse constraints as observed, BLGB is the closest but built on a limiting case and thus is inapplicable.

In other words, there is no mathematical or computational model in existence to describe the collapses of any of the three buildings!

There's plenty to criticize using legitimate principles and methods. Or we can argue about whether a descending mass is losing PE if the space below is not empty. Doi.

You impede efforts to peel away the layers of the mechanical onion by spamming distractions that have nothin' to do with nothin'. Is that your goal?


PS. I notice 95% of my comments do not merit a response from you. So I'm going to reiterate one very important one:

Your physical modeling challenge has been met.

cursuswalker wrote:http://www.9-11commission.gov/report/911Report.pdf

Anyone care to challenge any of the assertions of the 9/11 Commission report? Please give page number, quote and an evidenced refutation.

I won't challenge any of the assertions but I will note that it's written like a bad TV show treatment. Short attention span theatre, I guess.

Rippingly good post over here, econ41.