CTist's computer simulations of collapses

[Pardalis]

As anybody seen these (http://www.gnn.tv/threads/18598/Engineer_s_Remarkable_WTC_Collapse_Simulations)?

Who is this "mmmlink"?

And if you look at his/her subscribers at youtube, you get... a certain Truthseeker (http://www.youtube.com/profile?user=truthseeker9112001).

I dare you to look at his myspace page.

"World Can't Wait", skeptigirl?

[Oliver]

As anybody seen these (http://www.gnn.tv/threads/18598/Engineer_s_Remarkable_WTC_Collapse_Simulations)?

Who is this "mmmlink"?

And if you look at his/her "subscribers at youtube, you get... a certain Truthseeker (http://www.youtube.com/profile?user=truthseeker9112001).

I dare you to look at his myspace page.

"World Can't Wait", skeptigirl?

The simulations are a littlebit older and there was a thread about it.
But the whole video is new to me:

ExmSMU9ls-w

[Pardalis]

The simulations are a littlebit older and there was a thread about it.

I must have missed it. Was it recently?

[Anti-sophist]

The end is classic. He zooms into the basement where you see a curious blue box. Then as you get closer, you see a nuclear symbol on it. THE END. *anticipate*

[Anti-sophist]

Debunked: http://www.youtube.com/watch?v=2ows-BQqFTg

Sorry, I just can't resist.

[Oliver]

I must have missed it. Was it recently?

Maybe it came up within a discussion but i´m pretty sure i did read about the simulations in here. Don´t know what thread it was. :boggled:

@Anti-sophist

Use the (yt) tag to imbed youtube videos within your message. Description here:
http://forums.randi.org/misc.php?do=bbcode

[gumboot]

The simulations are a littlebit older and there was a thread about it.
But the whole video is new to me:


Wow. That was lame.

-Gumboot

[Oliver]

Wow. That was lame.

-Gumboot

Why was it lame? Someone mixed the clips together in Hufschmid-Style and accompanied it with cool music. :D

[Anti-sophist]

This is a far more legitimate analysis than I've ever seen by a CTer. (I don't mean accurate, mind you.)

The real question here is why he isn't publishing these results.

Did he make any of his model and it's parameters public?

[Pardalis]

I wonder who that mmmlink is.

[tacodaemon]

Why was it lame? Someone mixed the clips together in Hufschmid-Style and accompanied it with cool music. :D

What is it with CTists and videos that take for-freaking-ever to get to the point? That slowpoke 10-minute video could easily have been cut down to three or less.

[gumboot]

The majority of the video seemed to be to demonstrate explosive charges being placed in his model of the WTC. I really don't understand how there's anything even remotely scientific about that.

Are we meant to automatically believe the explosives theory just because it uses a model to demonstrate it?

-Gumboot

[Pardalis]

At least it denies the "concrete core" theory... :D

[MRC_Hans]

A fundamental problem with his model is that he assumes that the structure elements are infinitely strong. He only uses their elastic deformation. For instance, he has a point where he has removed all core supports but one, and all outer supports but one side, and then he shows the whole thing flexing. However, that scenario is certain to load not only the supports, but also the floor elements far above their breaking strength.

As for his analysis of how high the remains should be, he conviniently forgets the many storeys of subterran structure: The piles of debris were much "higher" than you see above the ground.

After that, of course, he goes off in pure fiction.

Hans

[Shrinker]

I'm confused by one thing. He says because the model is large it has to be scaled down? Huh? Was it too big to fit on his monitor? Computers don't care about size. It's complexity they have a problem with.

He says his floors are 420mm wide. In another thread the good people here were able to confirm for me that a 1:100 scale model would be 100 times stronger than the real thing. In this simulation has he scaled down the material strengths appropriately?

Admittedly I know nothing about finite state analysis. Does this scale thing strike anybody else as odd?

[MRC_Hans]

Yes, it does. You are right about strengths. If he simply scaled it down, material strengths and elasicities may have been affected.

I don't know why he had to scale it. Perhaps his analysis tool has some internal finite scale that limits the size of the objects it can handle. I expect a floating scale (gridless) will make the calculations more complex by adding an overhead of scale calculation to each iteration. Since this type of analysis is intrinsically limited by your computing capacity, there is bound to be some built-in simplifications to speed it up. A basic fixed grid could be one such simplification.

Basically, you can never just scale a structure, because areas increase with the square of the scale and volumes (and hence weights) increase with the power of 3. To illustrate it, if you were to take practically any structure and double its size by simply scaling everything, the resultant strucure would collapse under its own weight (this may not apply to structures with a high strength redundancy, like bunkers, taks, etc.)

Hans

[uruk]

I think he scaled it down beause, more than likely, he ran the simulation on a PC. The full scale calculation would probably have taken days or weeks to run.
I do some CG stuff at home on a standard PC. Some images and animations can take a really long time to render (days) depending on what kind of simulation your runninng. (i.e. particle/fluid sim, global and caustic illumination..etc)

And from what he mentions in his description, he seems to be assuming the outcome , so he sets up his initial parameters appropriately.

[Shrinker]

I do some CG stuff at home on a standard PC. Some images and animations can take a really long time to render (days) depending on what kind of simulation your runninng. (i.e. particle/fluid sim, global and caustic illumination..etc)


I do the same thing at the office everyday :-)

My point is that scale is irrelevant. Extra scale does not necessaily mean extra complexity. If I asked you to render and image of Jupiter or an image of a snooker ball, you'd need about the same level of computation.

I've never used the kind of software they use for this analysis. If they operate in a grid based system where the grid components are always of a fixed real-world size then I guess that would explain the scaling.

[uruk]

I do the same thing at the office everyday :-)

My point is that scale is irrelevant. Extra scale does not necessaily mean extra complexity. If I asked you to render and image of Jupiter or an image of a snooker ball, you'd need about the same level of computation.

I've never used the kind of software they use for this analysis. If they operate in a grid based system where the grid components are always of a fixed real-world size then I guess that would explain the scaling.

Thats cool! A fellow pixel pusher.

Your right about the scaling down of the grid. that's more than likely what he means.

Rendering an image, no matter how complex the image takes the same amount of computation power and time. The computer is just determing what the color of a pixel should be. What adds complexity is any physical computations that determin what the pixel should be. This adds up if you have run the simulation for a large sample area.

You know that the rendering time of a single frame of an animation doubles and quadruples if you add things like global illumination, caustics, ray tracing, or ambient occlusion. That not to mention other CPU intensive physics based motion algorithyms like motion blur, fluid dynamics, particle simulation, soft and rigid body collision detection and cloth and hair dynamics. The more particles or vertices you have to calculate for the longer it takes the CPU to crunch through the numbers.

And ofcourse all this is nothing compared to physicy accurate computer simmulations. look here for example:
http://www.physorg.com/preview4343.html
I know it is a simulation about galactic formation. But it is essentialy a particle dynamics sim. (That may be oversimplifing it bit!) It took a super computer over a month to run the simulation!


Here are some links concerning the software and algorythims used by the author of the vid.
http://en.wikipedia.org/wiki/ProEngineer
http://en.wikipedia.org/wiki/Finite_element_analysis
http://en.wikipedia.org/wiki/Finite_element_method

[Oliver]

I have some expiriences with finite element calculations and for me it does not make sense at all. Especially that they don´t tell what software is used or how accurate it is - bending of the floors like in this video is beyond reality and if they scaled the model down, wich also makes no sense, then any calculations based on heat must be corrected, too. Finally the simulation says nothing at all about the real circumstances on 9/11.

[Shrinker]

Thats cool! A fellow pixel pusher.

Your right about the scaling down of the grid. that's more than likely what he means.

Rendering an image, no matter how complex the image takes the same amount of computation power and time. The computer is just determing what the color of a pixel should be. What adds complexity is any physical computations that determin what the pixel should be. This adds up if you have run the simulation for a large sample area.

You know that the rendering time of a single frame of an animation doubles and quadruples if you add things like global illumination, caustics, ray tracing, or ambient occlusion. That not to mention other CPU intensive physics based motion algorithyms like motion blur, fluid dynamics, particle simulation, soft and rigid body collision detection and cloth and hair dynamics. The more particles or vertices you have to calculate for the longer it takes the CPU to crunch through the numbers.

And ofcourse all this is nothing compared to physicy accurate computer simmulations. look here for example:
http://www.physorg.com/preview4343.html
I know it is a simulation about galactic formation. But it is essentialy a particle dynamics sim. (That may be oversimplifing it bit!) It took a super computer over a month to run the simulation!


Here are some links concerning the software and algorythims used by the author of the vid.
http://en.wikipedia.org/wiki/ProEngineer
http://en.wikipedia.org/wiki/Finite_element_analysis
http://en.wikipedia.org/wiki/Finite_element_method

Thanks uruk, I think we're in agreement but you're missing my point a little (or maybe I'm missing yours). Simulating the movement of a million stars isn't much different from simulating the movement of a million dust particles. The scale is massively different but you're still just calculating the forces acting on 1 million points.

As for finite element analysis, I assumed the principles were similar to the dynamcs engines you and I are familiar with; that you could simulate a structure of any size, so long as the dataset doesn't get out of hand. In a grid based simulation (like fluid dynamics) that's achieved by scaling the grid along with your model. If the software only supports grid divisions of say 1m x 1m x 1m then I can understand the problem, but I would find that quite surprising.

[rwguinn]

Thanks uruk, I think we're in agreement but you're missing my point a little (or maybe I'm missing yours). Simulating the movement of a million stars isn't much different from simulating the movement of a million dust particles. The scale is massively different but you're still just calculating the forces acting on 1 million points.

As for finite element analysis, I assumed the principles were similar to the dynamcs engines you and I are familiar with; that you could simulate a structure of any size, so long as the dataset doesn't get out of hand. In a grid based simulation (like fluid dynamics) that's achieved by scaling the grid along with your model. If the software only supports grid divisions of say 1m x 1m x 1m then I can understand the problem, but I would find that quite surprising.
notes on "too big"
Since this is what I do for a living, I thought I'd put my .02 n here.He's probably referring to the size of the arrays (matrices) and number of degrees of freedom...
In a Finite Element model, there are 6 degrees of freedom(dof) for each node. A length of beam requires 2 nodes. In order to exhibit bending or buckling behavior, you need a minimum of 2 beams,end to end--18 dof. For non-linear(Post failure) analysis, it takes 3 nodes per beam.
A shell element requires 4 nodes. bending and buckling require at least 2 elements--10 nodes, 30dof. Buckling requires 8 nodes per shell element, or 13nodes, 78 dof.
Put these in an array to generate the stiffness matrix, and a mere 200 nodes is now 1200x1200 mass array, and a 1200x1200 stiffness array. Invert a 1200x1200 array.
and you cannot describe much with 200 nodes.In order to get a moderately accurate description of the WTC, for 1 floor, you are looking at on the close order of 100,000 nodes--for 1 floor! you'd have to make some pretty iffy assumptions to do that, even.
To model all the joints, welds, and other incidentals, such as studwork, walls, etc--
I wouldn't tackle it with anything less than a big honkin' CRAY, and billions of gB of swap space...

[Shrinker]

Thanks rwguinn. Can you think of any reason why he would say 'the model is too big therefore I have scaled the floors to 420mm per side'? He doesn't say anything about reducing complexity, just reducing the actual size.

[rwguinn]

Thanks rwguinn. Can you think of any reason why he would say 'the model is too big therefore I have scaled the floors to 420mm per side'? He doesn't say anything about reducing complexity, just reducing the actual size.

:shocked: No legitimate reason. These things DO NOT SCALE WORTH an ED!
Believe it or not, in the real world, size matters
you cannot make a scale model and expect it to behave like the full scale device/building/whatever.
Gravity is not scalable. Molecules are not scalable (nor are atoms)
420mm is less than the width of a vertical beam (Aka a collumn)

My response to the video/whatever--I can't look at it at work) would then be:

:dl:
and MRC_Hans--
He started with a work of fiction, if all the above is true...

[gumboot]

bending of the floors like in this video is beyond reality


I really didn't get his point...

He seemed to be suggesting there would be no sagging, etc...

He also seemed purely to be using sagging based on removal of structural supports.

It is my understanding that the floor sagging occured due to heat, not removed supports.

Indeed, given that the sagging floors pulled the exterior columns inwards to cause collapse, the supports NEED to stay intact for collapse to occur.

In addition, NIST haven't claimed enormous sagging. A structure like that will only sag so far - the exterior columns were reported as having bowed a matter of inches before failing.

Even minor sagging would exceed integrity and result in failure, I would think. On a graphic as small as that one was on my screen, I wouldn't be surprised if failure occured at a level of movement too small for my eyes to detect.

-Gumboot

[rwguinn]

As anybody seen these (http://www.gnn.tv/threads/18598/Engineer_s_Remarkable_WTC_Collapse_Simulations)?

Who is this "mmmlink"?

And if you look at his/her subscribers at youtube, you get... a certain Truthseeker (http://www.youtube.com/profile?user=truthseeker9112001).

I dare you to look at his myspace page.

"World Can't Wait", skeptigirl?
ok--
I cannot view the video. I can, however, comment on what he says.
I created them using ProE and have been working on them for about nine months now. I used a modeling program to produce the animation. They are to scale down to a mm based on drawings/literature from NIST and FEMA. There were many iterations. The original only had the upper floors. I was going to try and perform a Finite Element Analysis on fires bringing them down but found out quickly how big the model would become and that it would not demonstrate the collapse. First off, he is claiming accuracy of 1mm over a length of 416160 mm, or 2.4 parts per million (0.000024 % out of 100%), which is ridiculous.
The last sentence is key, here, however. What that says is " I couldn't do an actual analysis using science and engineering math, so I used an animation to present what I think should have happened" He states his working hypothesis in NIST and FEMA were very careful to only show 2D drawings and illustrations because showing a realistic 3D model would make it even more difficult to explain fires causing the collapses (which after $20 million, is yet to be simulated).If he wee a FEM'er, he would know that Pro-E, Algor, I-Deas, and NASTRAN--and their ilk--will only show you where the first failure will occur to go beyond that requires lots and googles of computer power and scratch space. He admits this in the first paragraph- it would not demonstrate the collapse. The obvious "This is what I think should have happened" clue comes from I am confident office fires did not weaken the steel causing a sudden global collapseIf he had done any actual analysis, with temperature reduction factored in, that FS of 5 which is (Allowable stress)/(actual stress) very quickly becomes <1. That means the actual is higher than the allowable, and things start bending. Once bending starts, with nothing to stop it, things begin to break.
(I actually prefer to use "Margin", which is (FS-1). 0.0 margin and up lives, Margin<0.0 dies)

so, in short, what he did was, as we call it, "make pretty pictures" There is no analysis involved that I can discern.

[gumboot]

so, in short, what he did was, as we call it, "make pretty pictures" There is no analysis involved that I can discern.


That's the impression I got. It seemed a bit of a "I say the building didn't collapse from fires and I would know because I did this cool model" even though the model doesn't seem to actually show anything at all.

-Gumboot