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David B. Benson
QUOTE (shagster+Nov 8 2007, 04:34 PM)
"It remains for the user to decide whether the pancake collapse theory agrees with the recorded free fall times."

He needs to bring himself up to date.

Hiss e-mail address is listed on his site. You might want to inform him.
stundie
QUOTE

Yet you feel the need to respond to my posts!

QUOTE (->
 QUOTE Sorry Stundie, my life work is not to answer your questions.

Yet you feel the need to respond to my posts!

The facts are that a Plane carrying many THOUSANDS of gallons of JET FUEL crashed into the building that had ELEVATOR SHAFTS that went all the way to the BASEMENT.
This is not a fact then is it. Its YOUR ASSUMPTION!!Let me explain it too you Arthur as you are struggling here....

If it was a fact, then you would be able to provide the proof...You do not, so it's an assumption on your behalf....its what you believe!

QUOTE
The crash caused damage to the CENTRAL CORE which included the ELEVATOR SHAFTS.
How much damage?

QUOTE (->
 QUOTE The crash caused damage to the CENTRAL CORE which included the ELEVATOR SHAFTS.
How much damage?

The fuel entered the building at HIGH RATE OF SPEED and was thus mixed/distributed with great force.

Yes and most of it burned off in the initial impact fireball. So please tell us how much was left and where and how it traveled according to your crackpot theory??

QUOTE
There were fires seen near a number of Elevator doors (see NIST report)
And this proves what...there were fires near a number of elevator doors...nothing else?

QUOTE (->
 QUOTE There were fires seen near a number of Elevator doors (see NIST report)
And this proves what...there were fires near a number of elevator doors...nothing else?

There were fires seen coming out of Elevator shafts (see NUMEROUS reports)
Again, you should be able to source reports but for some reason, you cannot. I'm sure if you could, you would take the time to make me look stupid and prove me wrong.
QUOTE
There were people burnt by Elevator doors (see numerous reports).
People burnt by elevator doors?? That's a new one!! I though they were burnt by fire.

QUOTE (->
 QUOTE There were people burnt by Elevator doors (see numerous reports).
People burnt by elevator doors?? That's a new one!! I though they were burnt by fire.

We KNOW that fuel would be forced down the shafts and we know that fuel/air can be EXPLOSIVE.

Who is "We" which you are referring too when you says "We KNOW" ?? Where is your EVIDENCE again?? Lets face it, you assume this happened and yes we all know that fuel/air can explode, but you haven't a single piece of scientific evidence to prove this....and yet you BELIEVE it. Hilarious stuff!! hahahahahaha!!!

QUOTE
These FIRE related events all happened CONCURRENT with the plane's impact and ONLY in the tower where the impact intersected the Elevator Shafts.

Maybe you should try backing it up with this thing called EVIDENCE, which you tend to ignore when supporting your own loony theories but demand it for ANY other theories. Even if it's only to dismiss it when presented.

QUOTE (->
 QUOTE These FIRE related events all happened CONCURRENT with the plane's impact and ONLY in the tower where the impact intersected the Elevator Shafts.

Maybe you should try backing it up with this thing called EVIDENCE, which you tend to ignore when supporting your own loony theories but demand it for ANY other theories. Even if it's only to dismiss it when presented.

What we DON'T have any evidence for is any OTHER source of explosions.
NONE
ZERO
ZIP
ZILCH
So you admit (Finally!) that you do not have any evidence for the source of the explosions?? So how does this then disprove the explosives theory then?? hahahahahaha!!!

QUOTE
If you want to claim there were explosions then simply provide EVIDENCE to support your claims.

I have posted Sonograms which show similar spikes in the frequency to that of other Demolitions but you ignored it!!
I have posted video of explosions at GZ after the collapses of WTC 1 & 2 but before WTC 7 but you ignored it.
So if I post this video which shows plumes of smoke coming from the ground before the collapse of the WTC you will ignore it.
If I show you evidence that squibs can be seen detonating during the collapse and these are associated with controlled demolitions, you will ignore it.
If I post this video of WTC 7 in which you can hear 2 explosions before it collapses(Goto 4:28) you will ignore it.
You say the explosions could be anything, so when I ask for proof/evidence to support your claims, you ignore it.

What did George Orwell have to say about ignorance?? Please tell us Arthur, is it bliss??
stundie
It was me that mentioned the Sonograms in regards to a post that Arthur made and I agree with what you have said with the exception of this little nugget which I have major problems with. Trippy you say this...?
QUOTE (Trippy+)
Continued failure to do so can only be construed as an admission that you are wrong, we will be forced to interpret your unwillingness to do so as an admission that all single impulse sounds share the same features, irrespective of whether you're talking about a drum beat, or the detonation of C4, thusly claiming that a sonogram is evidence of controlled demolition because they "look the same" is significantly in error.

Would you agree a sonogram looks at the amplitude, frequency and time parameters?? A Yes or No answer will do.

If you are answering Yes, then for that statement to be correct, you are suggesting that a drum beat & detonation of C4 share the same frequency and amplitude?? Hence the sonogram can't detect the difference?? lol

If you are answering No, then please explain what a sonogram consists off and why it can't detect the difference between a drum beat and C4 exploding.

Because to be honest Trippy, I'm calling BS on you....again.

Another thing which makes your statement look EVEN more ridiculous is the wikipedia entry which states:-
QUOTE
http://en.wikipedia.org/wiki/Spectrogram
Spectrogram's are used to identify phonetic sounds, to analyse the cries of animals, and in the fields of music, sonar/radar, speech processing, etc

So it can be used for all these things, but according to you, it can't be used to detect the difference between a drum beat and C4 exploding?? hahahahahahaha!! lol

You should speak with Wcelliot too, according to him, he was working on a sonogram program which would be able to identify small aircraft by the engine/prop noise. http://forum.physorg.com/index.php?showtop...ndpost&p=275207
QUOTE (->
 QUOTE http://en.wikipedia.org/wiki/SpectrogramSpectrogram's are used to identify phonetic sounds, to analyse the cries of animals, and in the fields of music, sonar/radar, speech processing, etc

So it can be used for all these things, but according to you, it can't be used to detect the difference between a drum beat and C4 exploding?? hahahahahahaha!! lol

You should speak with Wcelliot too, according to him, he was working on a sonogram program which would be able to identify small aircraft by the engine/prop noise. http://forum.physorg.com/index.php?showtop...ndpost&p=275207
I was PROGRAMMING sonogram software for IDENTIFYING small aircraft by their engine/prop-noises back in 1985.

How the hell does a sonogram detect the difference between engine/prop noises, yet according to you Trippy, it can't detect the difference between a wire snapping, a drum beat and C4 going off??

That must mean they share the same frequency, amplitude etc etc.....lol

You are just a terrible liar aren't you Trippy??
QUOTE (Stundie+)
QUOTE (Arthur+)
The facts are that a Plane carrying many THOUSANDS of gallons of JET FUEL crashed into the building that had ELEVATOR SHAFTS that went all the way to the BASEMENT.

This is not a fact then is it. Its YOUR ASSUMPTION!!Let me explain it too you Arthur as you are struggling here....

If it was a fact, then you would be able to provide the proof...You do not, so it's an assumption on your behalf....its what you believe!

Stundie, considering the above statement, I just have to ask: Are you a "NO PLANE" CTer or a "It wasn't really AA11 that hit WTC 1" CTer????

My answer below assumes you aren't THAT dumb:

I recently provided a 3d layout of the Elevator shafts that showed shafts going from the impact floor all the way to the basement.

The layout of the elevators is well known (and I've in fact documented their layout in this thread (by elevator number, by floors served)

Live video from multiple sources showed the plane hitting the towers.

The amount of fuel the plane was carrying when it hit is well documented.

The amount of fuel burnt outside (~1/3) was calculated by NIST based on their impact analysis and visual analysis and I've seen no serious refutation of their estimates.

The amount of damage done to the core was derived from NIST analysis but is inline with other independent analysis done by the group at Purdue, MIT etc.

I gave links to stories of people burnt by the elevator shafts in the lobby of WTC 1, but others are easily found and have also been covered IN THESE THREADS.

QUOTE (Stundie+)
I'm sure if you could, you would take the time to make me look stupid

Why bother? You're doing a GREAT job all by yourself.

Arthur
wcelliott
QUOTE
So it can be used for all these things, but according to you, it can't be used to detect the difference between a drum beat and C4 exploding?? hahahahahahaha!! lol

You should speak with Wcelliot too, according to him, he was working on a sonogram program which would be able to identify small aircraft by the engine/prop noise. http://forum.physorg.com/index.php?showtop...ndpost&p=275207

QUOTE ("Wcelliot")
I was PROGRAMMING sonogram software for IDENTIFYING small aircraft by their engine/prop-noises back in 1985.

How the hell does a sonogram detect the difference between engine/prop noises, yet according to you Trippy, it can't detect the difference between a wire snapping, a drum beat and C4 going off??

That must mean they share the same frequency, amplitude etc etc.....lol

Well, Stundie, nobody can make you look as stupid as you can, yourself.

Trippy's statement is basically correct, impulse events all share the same basic characteristics visible in sonograms, and that is a simultaneous vertical stripe of energy across all frequencies from the zeroth-order all the way up. As I've explained to AlK ad nauseum, explosives detonate really quickly, a lot faster than any audio recorder can fully characterize. C-4 detonates at over 26,000feet/second, so a four-inch block (enough to transect a steel beam) would start-to-finish, detonate in 10 MICROSECONDS.

Maybe you can do the arithmetic that AlK hasn't been able to do, yet, and tell me what the sampling interval associated with a 40kHz sampling rate? (Hint: 1/sampling rate = sampling interval) So how many samples do you expect to have for a 10 MICROSECOND event?

Hint: ___________|_______________

That's what an explosive detonation looks like in the time domain, absent any reflections of the explosion off the local environment. Reflections will be attenuated by several factors, and will always be delayed, so that same ____|____ will bounce around off walls, floors, ceilings, etc., and each reflection will be delayed and smaller, and they'll all add up to that "characteristic N-shape".

The vertical spike is the detonation, the downward "\" slope is just the reflections off the environment, which means that it's ARTIFACT, not an intrinsic CHARACTERISTIC of the detonation itself.

All impulse-driven events have that _______|________ shape in time, and any impulse that reflects around inside a building will sound like an impulse reflecting around inside a building.

As I've explained to AlK a dozen times.

BTW, Prop aircraft have specific numbers of prop-beats/rotation of the engine, and engines in aircraft are either piston or jets, and each sound different. You can count the number of piston-engine exhausts per prop rotation, which will be characteristic for each type of aircraft manufactured, and jet engines have a characteristic frequency associated with the engine rpms and compressor blades/"exhaust buckets", and some planes have jet engines driving props, so there's that characteristic, and different planes have different numbers of engines. All of those sounds reflect off their airframes, which is aspect-dependent. That's how aircraft can be identified (mostly, some planes' characteristics overlap).

And the software that Trippy provided links to were pretty similar, basically, to the software that I'd written way back in 1985 when you were probably still in diapers (when I was a Senior Staff Scientist for Science Applications International Corporation). That was about the same time I designed a digital signal processor to do acoustic beamforming. From scratch, with adder-chips. Under a million-dollar contract based on a ten-page white-paper I wrote.
einsteen
There seems to be someone at the LC forum who went deep into the fuel and elevator shafts theory. It was also posted at the JREF, but due to insults etc it became closed. I'm not the kind of detective to read and go through this, but if anyone is interested
http://z10.invisionfree.com/Loose_Change_F...showtopic=18745
I've read it, but there is nothing new.

He apparently coined a new phrase "a Secret Controlled Demoltion"

Here's his conclusion

If one concedes that the Twin Towers were demolished, than it's safe to say that it wasn't a Controlled Demolition (CD) in the common manner. It was a Secret Controlled Demolition (SCD). A SCD requires a cover legend to make it not look like a demolition. This legend is that the impact damage of the planes and the subsequent fires brought down the towers.

This legend made it necessary to bring down the building from the top (impact zone) to the bottom - unlike most other, non-secret, Controlled Demolitions. To carry out this SCD successfully, it was also necessary that the fires could not have been exstinguished. Exstinguished fires would have destroyed the cover for the Secret Controlled Demolition. The explosions in the basement levels and on floor 22 secured the cover for the whole operation. And therefore were a necessary part of the SCD.

But it turns out, its all a long FAIRY TALE.

Like assuming that an elevator that is out of service IS IN THE BASEMENT.

Arthur
David B. Benson
QUOTE (adoucette+Nov 9 2007, 09:49 AM)
... its all a long FAIRY TALE.

Please do not insult fairy tales.
einsteen
I've not read it but I disagree that such a SCD didn't look like a CD. Wtc7's collapse looked exactly like a CD. For the twin towers there is nothing to compare them.
wcelliott
QUOTE
Please do not insult fairy tales.

LOL!!!

Trippy
QUOTE (stundie+Nov 10 2007, 01:53 AM)
It was me that mentioned the Sonograms in regards to a post that Arthur made and I agree with what you have said with the exception of this little nugget which I have major problems with. Trippy you say this...?

Would you agree a sonogram looks at the amplitude, frequency and time parameters?? A Yes or No answer will do.

If you are answering Yes, then for that statement to be correct, you are suggesting that a drum beat & detonation of C4 share the same frequency and amplitude?? Hence the sonogram can't detect the difference?? lol

If you are answering No, then please explain what a sonogram consists off and why it can't detect the difference between a drum beat and C4 exploding.

Because to be honest Trippy, I'm calling BS on you....again.

Another thing which makes your statement look EVEN more ridiculous is the wikipedia entry which states:-

So it can be used for all these things, but according to you, it can't be used to detect the difference between a drum beat and C4 exploding?? hahahahahahaha!! lol

You should speak with Wcelliot too, according to him, he was working on a sonogram program which would be able to identify small aircraft by the engine/prop noise. http://forum.physorg.com/index.php?showtop...ndpost&p=275207
QUOTE ("Wcelliot"+)
I was PROGRAMMING sonogram software for IDENTIFYING small aircraft by their engine/prop-noises back in 1985.

How the hell does a sonogram detect the difference between engine/prop noises, yet according to you Trippy, it can't detect the difference between a wire snapping, a drum beat and C4 going off??

That must mean they share the same frequency, amplitude etc etc.....lol

You are just a terrible liar aren't you Trippy??

This post almost completely lacks substance - except perhaps to serve as evidence of the depths of Stundies delusions.

Nowhere did I claim that a Sonogram couldn't tell the difference between a drum beat and C-4 going off.

What I did say was that there were similarities, because they were both single impulse sounds. I didn't, and have never claimed that they were identical. The only other thing I have claimed is that any other single impulse sound will share the same features that the website you linked to at one stage - including the single impulse sound that I posted an image of earlier.

So, I would appreciate it, and think it would be best if you would apologize for your baseless accusations, and kept your delusional ramblings to yourself.
QUOTE (einsteen+Nov 9 2007, 03:59 PM)
I've not read it but I disagree that such a SCD didn't look like a CD. Wtc7's collapse looked exactly like a CD. For the twin towers there is nothing to compare them.

Well one can't PRESUME its a SCD.

One needs EVIDENCE.

The fact that a building's collapse APPEARS to look somewhat like a CD is NOT evidence that it was a CD.

The FACT is though that WTC 7 only SUPERFICIALLY looks like a CD.

What it clearly does not look like is any CD I've ever seen (and over the last several years we've looked at a lot of CDs)

If you think it does then simply show us a CD of another large building where the building first BURNS out of control for ~ 7 hours before undergoing a multi-stage collapse that takes ~ 18 seconds, and includes structural failures on both sides of the building, evidenced by the rooftop penthouse mechanical sections falling into the building, followed by a kink developing 1/3 way across one side, all the while at least two curtainwall sides of the building show little apparent motion, before they collapse onto the pile created by the rest of the building.

Can't wait.

Arthur
einsteen
Those mechanical penthouses dropped right before the rest of the collapse. There has been
posted a new show somewhere where they told that probably fireproofing had been removed because
of the debris of the collapsing towers.

But if we look at differences between the collapse of wtc7 and a CD, I can help you, check this
flash video that Jowenko has on his page (an expert who you can always call, his phone number is on the website)

http://www.jowenko.com/gfx/intro/intro.flv , or
http://www.jowenko.com/

In this controlled demolition

- there are no fires on the floors where no charges are placed
- the building is completely stripped
- there is no damage from collapsing towers
- probably there is even a siren going off before the collapse
- there is no smoke because there is no fire
- there is no equipment
- there are even no windows that break
...how long do you want to have the list...

hence wtc7 was no CD.
QUOTE (einsteen+Nov 9 2007, 05:42 PM)
Those mechanical penthouses dropped right before the rest of the collapse.

Right before?

See http://www.911research.com/wtc/evidence/vi...s/wtc_7_cbs.mpg

Watch the penthouse on the right collapse ~ 7 seconds before the penthouse on the left collapses followed by the rest of the curtain wall.

Arthur
OneWhiteEye
QUOTE (einsteen+Nov 9 2007, 09:42 PM)
...how long do you want to have the list...

Hahahaha! Please, einsteen, surely you know that all you need to do is draw a breath and think of a reason, and it is sufficient to conclude:

QUOTE
hence wtc7 was no CD.
David B. Benson
Using the data provided by poster OneWhiteEye with a constant acceleration and no stretch model gives

a = 0.648 g

which is consistent with the figure of (2/3)g obtained with a stretch of 0.14 using the data provided by poster NEU-FONZE.
newton
QUOTE (einsteen+Nov 9 2007, 07:59 PM)
I've not read it but I disagree that such a SCD didn't look like a CD. Wtc7's collapse looked exactly like a CD. For the twin towers there is nothing to compare them.

exactly like a CD.

metamars
K.A. Seffen's (apparently a structural engineer) paper entitled "Progressive Collapse of the World Trade Centre: a Simple Analysis" is available at http://winterpatriot.pbwiki.com/f/seffen_simple_analysis.pdf

I haven't read most of the paper, but I appreciate the fact that he's trying to account for the effects of propagating instability. OTOH, he claims "The resulting impingement produced peak forces correctly identified by Bazant and Zhou (2002) to be far in excess of the design capactiy of these columns and hence, above the expected value of "Pmax" that could be reasonably carried by them, even if perfect and undamaged".

Which tells me that he is swallowing BZ's implicit assumptions of fixed lower column ends (without which calculations of quasistatic buckling equations make no sense), and ignoring the literature on impacts, just like BZ.

An initial strike of 8 m/s should be close to the elastic limit, so perhaps one can ignore plastic waves. Also, energy dissipated in overcoming lateral inertia is probably neglible.

However, other ignoring of dynamic effects suggests to me that this paper probably is useless for correcting the BZ scenario, per se. However, it seems a step in the right direction ito more realistic papers (which assume collapse initiation), that don't depend on axial symmetry.
David B. Benson
QUOTE (metamars+Nov 10 2007, 08:46 AM)
K.A. Seffen's (apparently a structural engineer) paper entitled "Progressive Collapse of the World Trade Centre: a Simple Analysis" is available at http://winterpatriot.pbwiki.com/f/seffen_simple_analysis.pdf

Thank you for posting this reference. I will shortly study this paper.

Dr. Seffen is a lecturer (Assistant Professor equivalent) at Cambridge. In the U.S., at least, he cannot call himself a structural engineer until he can put P.E., S.E. after his name. So he is a academic researcher, specializing in structures, just as is Professor Bazant.

As for your 8 m/s, from my older calculations, this did not occur until 1.2 seconds into the collapse, at which time the drop of the top was 4.87 meters at the center (using the B&V crush-down equation with a constant force and a constant stretch of 0.14). All elastic effects were gone in less than 0.2 seconds.
OneWhiteEye
einsteen -- your PM inbox has been full for a while. I know - diapers.
cheers.
OneWhiteEye
David B. Benson: though it may not seem so, I've payed attention to your various posts regarding data fit but I'm still putting it together inside that feeble knot at the end of my spine. The Bayesian reasoning is quite interesting and I get that OK. I was already familiar with Bayes networks and classifiers (which I will probably end up using in conjunction with various clustering techniques to implement true pattern recognition in my code).

One thing you might be able to help me with is the stretch factor. Can you give me a quick explanation of the underlying physical meaning and derivation of this term? I'm sure it's already written in multiple places but, if you can, it would certainly save me time digging around. Thanks.
David B. Benson
QUOTE (OneWhiteEye+Nov 10 2007, 01:19 PM)
... the stretch factor.

Of the entire floor height h = 12 feet, about half is just air. Gently setting a floor down upon the office furnishings and computer terminals below would produce about half that height; the stretch is s = 0.5 and the resulted 'crushed' mass is s*h = 6 feet high. When the collapse proceeds faster, the office furnishings are thoroughly crushed and the trusses are somewhat crushed,; the stretch is smaller, maybe s = 0.18. At the very end of the collapse it is possible to observe the 'pancaked' floors; the stretch is about s = 0.05.
OneWhiteEye
QUOTE (David B. Benson+Nov 10 2007, 08:41 PM)
Of the entire floor height h = 12 feet, about half is just air.  Gently setting a floor down upon the office furnishings and computer terminals below would produce about half that height; the stretch is s = 0.5 and the resulted 'crushed' mass is s*h = 6 feet high.  When the collapse proceeds faster, the office furnishings are thoroughly crushed and the trusses are somewhat crushed,; the stretch is smaller, maybe s = 0.18.  At the very end of the collapse it is possible to observe the 'pancaked' floors; the stretch is about s = 0.05.

Excellent! Thank you.

Edit: is the stretch applied to each floor successively during motion or does it also account for stretch of accumulated mass at the front?
einsteen
OneWhiteEye,

I'm sorry but my Inbox was completely full which I didn't notice, I've posted and logged in a couple of times, did you not get a bounced message ? I hope it is still in your SendBox so that you can resend.

Arthur,
You're right, I was confused and thinking about the other half of the penthouses that collapsed right before the rest of the building.
But if we look at those 7 seconds on a scale of 7 hours fire... that is 99.97% of the time no single movement.

All,
fyi, I've mailed Charles M. Beck if he liked to discuss here, but still no reply, holiday probably.
David B. Benson
QUOTE (OneWhiteEye+Nov 10 2007, 01:47 PM)
... does it also account for stretch of accumulated mass at the front?

In the equation there is a single number to account for the average stretch of the entire crushed mass, obviously a simplification. It is, I am strongly convinced, a completely harmless simplification.
QUOTE (einsteen+Nov 10 2007, 05:33 PM)
Arthur,
You're right, I was confused and thinking about the other half of the penthouses that collapsed right before the rest of the building.
But if we look at those 7 seconds on a scale of 7 hours fire... that is 99.97% of the time no single movement.

Only from the distance those videos were shot from.

The fact that the building was failing was more obvious to those at the scene.

And it was obvious HOURS before the building finally fell.

Arthur
David B. Benson
Figure 5 of Seffen's paper agrees with the values produced by my older simulation program: From the program, the acceleration starts at 0.83g and drops to 0.55g by 3.0 seconds.
NEU-FONZE
I e-mailed Dr. Seffen ~ a month ago about his paper ............ still no reply.........

Anyway, his paper is good applied math, but he really has nothing to say about collapse initiation except the usual "the uppermost parts of the WTC towers were falling freely due to the absence of column resistance...."

Where has anyone proved the truth of this statement?

I thought the tower's collapse started with a tipping motion...
David B. Benson
QUOTE (NEU-FONZE+Nov 10 2007, 06:36 PM)
... except the usual "the uppermost parts of the WTC towers were falling freely due to the absence of column resistance...."

Where has anyone proved the truth of this statement?

I thought the tower's collapse started with a tipping motion...

Yup.

Isn't true. The data shows that there was resistance at all times.

Yup.

=====================================================

Back to an equation for the stretch. I get good results using a equation for the stretch of the form

s(Z,S) = k*exp(-b*Z*S*S)

(Z is the drop, starting at some Z0 and growing; S is the speed) where the exponent then depends upon the energy available to do the crushing, but the idea is that the stretch can never become non-positive.

Nonetheless, this might not be the best physically motivated form. I would appreciate comments.
NEU-FONZE
DBB:

About the stretch. (And by the way, I dislike the term stretch .... "squash" would be more appropriate!) I prefer the term compaction ratio.

I am not sure that a stretch of 0.05 was physically possible for the WTC collapse. That would mean a floor was crushed to a height of 7 inches!

Large commercial trash compactors typically deliver a maximum compaction ratio of 9:1 and operate at pressures up to 3000 psi. It requires 3000 psi to crush a car to a height of about 8 inches. If we take a typical car height as 4 feet we have a compaction ratio of 6:1.

My guess is that the typical compaction ratio in the WTC was also about 6:1, or 12 feet -> 2 feet, giving a stretch of 0.167.

Remember too there was a lot of "void" space in the rubble pile.

0.05 would really be s-t-r-e-t-c-h-i-n-g it!
But Neu, in a typical office floor, probably about 1/2 that 12 foot space is probably empty to start with (or has things like a suspended cieling which is almost all air), so comparing it to the ratios of a trash compactor seems like a bad starting point for comparison.

I agree with you though, compaction ratio is a much better choice for the variable.

Stretch is counter-intuitive.

Arthur
wcelliott
I kinda like "squash", myself, but...

Another point should be considered, and that's that those thin floors aren't exactly like the pistons in trash compactors, either. At the time that the floors started collapsing, it's my belief that they were already broken up into random-sized slabs by the differential thrusts associated with the various columns either still intact (and compressed) or transected (and no longer compressed by >30 floors' weight, so those columns' compression was released suddenly).

Sorry for the dense syntax, it's early for me, but you get the idea. Floors start out flat, supported by hundreds of columns, each loaded equally, so compressed equally. Then, some of those columns get unloaded, and therefore uncompressed, and the floors are rigid, but their supports are no longer in a plane, so the floor snaps into hundreds of individual slabs, even prior to the collapse.

During the collapse, those broken slabs land on irregular objects, some higher, some more resistant to "squash", plus lots of mostly-unoccupied floorspace, and they further snap into smaller slabs. Eventually, the debris from the upper floors adds to the total weight, and eventually, it all gets squashed flat, but not at prior to the floor releasing from its supports. The floor supports would be subject to "unzipping" (shearing one after another) from the shock of the impact of the upper floors' material. You'd get some of the squash happening as the floor releases, some more as the kinematics of the higher-velocity falling material accelerates the just-released material to the same speed, and the final "squash" happening when the falling material encounters the rubble-pile and the lower stuff stops even though the upper stuff is still falling.

DBB - WRT to "other form of the equation", did you ever consider the form I suggested describing the balanced broomstick tipping-over? (Or the same basic idea of a column buckling?) Either/both seem more physical to me, given the circumstances, and both have the features we're looking for - a long period where there's almost no perceptible descent, followed by a noticeable descent rate that increases with time, transitioning to an almost-pure fractional-g descent. I'm not proposing this as a literal interpretation, but you can appreciate how an equation that describes one column failing under load might also describe a floor being supported by hundreds of columns, each failing under load...
David B. Benson
QUOTE (wcelliott+Nov 11 2007, 09:23 AM)
I kinda like "squash", myself, but...

DBB - WRT to "other form of the equation", did you ever consider the form I suggested describing the balanced broomstick tipping-over?

I agree that stretch is not the most intuitive term, but it is what B & V use for the compaction ratio.

I fail to see how this could apply to determining the instantaneous value of the stretch.

In principle, the stretch starts at about 0.5, maybe 0.55, given that the floors contained office furnishings, but otherwise vertically were about half just air. So 0.05 is only maybe 10:1 and indeed from the photographic evidence, that about how tall some of the pancaked floors at Ground Zero were. Except of course for the 'meteorite' stored in Hanger 17, where the stretch is much, much less. The voids might not be important in such a reckoning. In any case parameter estimation chooses an initial stretch of s = 0.42 from which value the exponential decay reduces the stretch somewhat as the speed of the collapse increases.

Edited to add: Some of the floor pans observed 'pancaked' in Ground Zero had essentially no concrete in sight. It may well be that not all parts of the actual trusses were present between those floor pans.
wcelliott
QUOTE
I fail to see how this could apply to determining the instantaneous value of the stretch.

Sorry, I switched subjects mid-post. The equation I was referring to was the one describing the descent-vs.-time from impact to collapse, which people were curve-fitting linear and exponentials with varying degrees of success. I'm thinking that an equation describing a broomstick falling over would be a more-likely fit, with an even better fit (probably) being two broomsticks connected with a hinge with friction, buckling. This would be mostly trig functions, so far as I can guess.
David B. Benson
QUOTE (wcelliott+Nov 11 2007, 11:49 AM)
The equation I was referring to was the one describing the descent-vs.-time from impact to collapse, which people were curve-fitting linear and exponentials with varying degrees of success.

Ah. The equation is the B & V crush-down equation

(1-s(Z,Z'))(ZZ" + (Z')^2) - Z = F(Z,Z')

where Z is the location of the crushing front, normalized to start at some Z0 and proceed towards one, Z' is the speed,Z" is the acceleration, s(Z,Z') is the stretch and F(Z,Z') is the resisting force.

The issue is not this equation, per se, but rather appropriate functional forms for the stretch function and the force function.

The conclusion, so far, is that non-constant functional forms for the stretch or force provides a strongly better fit to the data than using constant functions for both stretch and force.
metamars
The problem of a rod fixed at one end and struck longitudinally on the other end is solved in A Treatise on the Mathematical Theory of Elasticity by A.E.H. Love (p. 431 - 435). Further details to the theory are contained in references dated 1916 and 1919. This purely elastic theory assumes that all elastic wave energy is reflected back into the rod when the waves hit the fixed end.

Maximum compression occurs at the fixed point.

While not exactly applicable to a WTC scenario (since the rod is uniform, while a WTC 'rod' would vary in width by a factor of 16), it's still interesting to calculate 'as-if'.

max compression = MC = (1 + sqrt(m)) * V / a

where m is the ratio of the impacting mass to the mass of the rod
V is the velocity of the impacting mass (~ 8 m/s in BZ scenario)
a is the velocity of longitudinal waves in the rod (~ 5,000 m/s for steel)

The following is very rough.

Using Gurich's figures, which give

* total mass (above grade) 240 Ktons
* structural steel (above grade) 89 Ktons

percentage of structural steel = 89 / 240 = 37%
call it 18.5%, since our WTC base 'rod' is only comprised of part of the structural steel, viz., the columns

mass per floor ~ 240 ktons/ 111 floors = 2.16 KTON/floor

mass(top) = (16 floors of WTC top) * 2.16 kton/fl = 34.56 KTON

mass(bottom "rod") = (111 - 16 floors) * (18.5% guesstimated column weight %) * (2.16 kton/fl) = 37.96

Plugging in to :

max compression = MC = (1 + sqrt(m)) * V / a

we get

MC = ( 1 + sqrt(34.56 / 37.96)) * (8 / 5,000)

= 0.0031

Since the lowest column segments were something like 5x the cross sectional area of the impact column segments, I would guess that the elastic limit would not be surpassed. Unfortunately, I'm not clear on what the compression profile is like in the upper part of the lower WTC block. (I still need to study this more.)

This theory assumes that the impacting mass is rigid, an assumption which favors collapse.

Chainsaw,
QUOTE (Al Khwarizmi - step-by-step+Oct 31 2007, 04:39 AM)
Trippy:
====================
Having dealt with UV-VIS and NIR spectroscopy, I'm well aware of the distinction between Infra- and Ultra.
====================
Your spelling is marginally better than your comprehension skills: neither are particularly good.
My comment regarding the embarrasing inability to distinguish between sub and super sonic was directed at wcelliot, not at yourself.

Check the record.

chainsaw
you directed abuse at me for a whacky guitar string analogy that was actually produced by wcelliot - hence, I cannot consider your unreferenced and unsubstantiated arguments to be sound.

Learn to use a url.

The analogy was Wcelliot's that is true however your comments were to put it gently Ludicrous.

Sound waves in air can be generated by snapping metal and have almost identical signature to explosives dependent on how and when they are generated.

Any one who has done any work with heavy equipment can tell you that try setting on top of a D7 Caterpillar when the final drive shears you would think a bomb went of under your rear end.

Try a sidewinder bush hog on a large pipe like an oil well hidden in weeds, or an inch cable on an oil rig holding up about 800- 1000 feet of drill stem.

Wcelliot's point was that energy could be stored in metal structures and released as sound waves in air, the energy in the waves depends on the energy transfered to the air by the breakage of the metals, Larger pieces of metals store more energy.
It is a simple concept, the only way to tell an explosion from a super sonic sound wave generated by another source is to look in the sound trace for the detonation delay the small bang before the large bang.
The detonator goes off and then triggers the larger explosive, often that is the only way to tell that Super sonic sound waves are from an explosion.
As for your opinion of my arguments that does not really matter as you have no argument to begin with so your opinion is mute anyway.

David B. Benson
QUOTE (metamars+Nov 11 2007, 01:01 PM)
The problem of a rod fixed at one end and struck longitudinally on the other end is solved ...

Is the rod horizontal or vertical?

This appears to have very little, indeed almost nothing, to do with the collapse initiation of the towers. I've already given you the references to two books by Simitses. These contain work which is relevant.
David B. Benson
QUOTE
One worker said they saw 14 stories in 8 feet.

That's 6.86 inches per story. Call it 7 inches.
Chainsaw,
QUOTE (NEU-FONZE+Nov 11 2007, 02:44 PM)
DBB:

About the stretch. (And by the way, I dislike the term stretch .... "squash" would be more appropriate!) I prefer the term compaction ratio.

I am not sure that a stretch of 0.05 was physically possible for the WTC collapse. That would mean a floor was crushed to a height of 7 inches!

Large commercial trash compactors typically deliver a maximum compaction ratio of 9:1 and operate at pressures up to 3000 psi. It requires 3000 psi to crush a car to a height of about 8 inches. If we take a typical car height as 4 feet we have a compaction ratio of 6:1.

My guess is that the typical compaction ratio in the WTC was also about 6:1, or 12 feet -> 2 feet, giving a stretch of 0.167.

Remember too there was a lot of "void" space in the rubble pile.

0.05 would really be s-t-r-e-t-c-h-i-n-g it!

I have to agree with that from drop tests the squash would have been between 2-1.5 feet. Greater than that and a dieseling effect causes an increase in oxidation leading to expansion of the air in the structure from heat energy increasing the energy needed for compression-squash.
I would like to also point out that other reactions can greatly effect the squash so that an average for it may be hard to determine.
I do not do much on 9/11 any more but I still like to look in once and a while to see how the work is progressing. Basically I have run out of explosives to test and things to blow up!
wcelliott
DBB-

Once again, my-bad for not making my point clearer.

Remember the smear-o-grams? The height of the WTC tower descended too-slowly to measure from impact to the point where it was 20cm lower than it was prior to impact, and then the smear-o-grams provided a curve and you and others tried curve-fitting various equations looking for a good fit, and finding none that seemed linked to the mechanics of the collapse?

*That's* the equation I was suggesting you try the balanced-broomstick model for. And failing that, a more-likely dual-broomstick-with-a-hinge (with friction). When the broomstick is almost perfectly balanced, the descent is microscopic, at a snail's pace, but its angular rate increases as a function of the net angular displacement due to the increasing moment arm of the Cg as it gets farther from the balanced position. That would explain the long, flat part of the curve that eventually ends up 20cm below the original height. The farther that Cg gets from being directly over the point of support, the more torque it exerts and the faster the broomstick rotates.

The "two-broomsticks-with-a-hinge" is more sophisticated, but explains Marie Osmond's collapse rate as a function of time even better than the "Silent Covert Explosives" conspiracy theory.

Please note that I'm not saying it's a literal instance of anything "falling over", I'm just saying that the equations are probably more mechanically-related to trig functions than to exponentials.
OneWhiteEye
QUOTE (wcelliott+Nov 11 2007, 09:31 PM)
Marie Osmond's collapse rate as a function of time...

I believe that would be meatbag mechanics; think chicken cannon.
David B. Benson
QUOTE (wcelliott+Nov 11 2007, 02:31 PM)
The height of the WTC tower descended too-slowly to measure from impact to the point where it was 20cm lower than it was prior to impact, and then the smear-o-grams provided a curve and you and others tried curve-fitting various equations looking for a good fit, and finding none that seemed linked to the mechanics of the collapse?

... than to exponentials.

AFAIK I am the only one how attempted to fit functions for the collapse initiation phase. NEU-FONZE has a theory about this, which he said a bit about in an earlier posting. By that theory, one certainly expects to fit a exponential force in the crush-down equation. However, a linearly declining force is statistically indistinguishable from his model.

The problem is that, as of yet, there simply is not enough data. Adding another possible model won't change that fact.

metamars
QUOTE (David B. Benson+Nov 11 2007, 08:17 PM)
Is the rod horizontal or vertical?

This appears to have very little, indeed almost nothing, to do with the collapse initiation of the towers. I've already given you the references to two books by Simitses. These contain work which is relevant.

Oops, no mention of gravity, so "horizontal".
David B. Benson
Rather to my surprise, despite the fact that at the chosen t0 WTC 1 had dropped almost 20 cm, the data indicates that the speed was zero at that time. While this might be because I didn't smooth the data first, it indicates that the speed was very small. Eventually I'll print out some tables for drop and speed from t0-0.2 seconds to t0+0.6 seconds.

Also, NEU-FONZE choose t0 extremely well. The program only wants to adjust it by a small fraction of a millisecond.
wcelliott
QUOTE
Wcelliot's point was that energy could be stored in metal structures and released as sound waves in air

... via the connection of that steel under stress to a large diaphragm, which acts like the diaphragm of a speaker.

(just to clarify, Chainsaw, I'm not upset with you...)

There were lots of steel members connected to large diaphragms in the WTC that failed suddenly under stress during the collapse. Look at your woofer's speaker cone, and figure out how much air it moves when it's playing back the sound of an explosive detonation. How many square inches area of the cone times how many inches displacement? As big and as loud as your woofer gets, that number is in cubic inches, and the power driving it is in Watts, not kilowatts.

Now do a similar calculation for a floor of a WTC tower. How many square inches in that "speaker cone" floor area? From calculations already provided here, a column suddenly transected would shoot upward at 30gs over a distance of about an inch, not raising the whole floor, but it would raise the floor locally (unless it merely sheared the floor bracket outright) by, say, a half-inch or so. How much energy is stored in a steel truss? It's half the load the truss is carrying times the net displacement (compression or stretch) of the beam. The stretch/compression factor of 0.002 was cited earlier, IIRC, for structural steel under a working load. So take your pick of trusses, calculate how many thousands of pounds, and multiply its length by the 0.002 and there's your energy in inch-pounds. I trust anyone interested in the answer should be capable of doing the rest of the math, or they shouldn't be posting here.

Incidentally, let's not get the supersonic shockwave generated by the initial blast confused with the ultrasonic frequency components of a 10microsecond-duration detonation event. If you want to "characterize" what a block of C-4 sounds like, you'll need to sample it at a rate that's high enough to detect the C-4 going off, the initial rise-time (the "attack"), the central portion of the blast propagating through the block (the "sustain"), and the trailing edge of the waveform (the "decay"), but all of those events take place in 10 microseconds or so, so your sampling rate had better be close to a MHz, otherwise all aspects of the event have taken place in one sample interval, and all information about the "chracteristic waveform" will have been lost in the undersampling process.

How much information is there in this stack of numbers?

0000 0000 0000
0000 0000 0000
0000 0000 0000
1111 1111 1111 <-- The detonation
0000 0000 0000
0000 0000 0000
0000 0000 0000
...

This is what a 12-bit digital recording of a block of C-4 looks like when the sampling rate is 40kHz. (It's also what it looks like at anything up to 100kHz.)

Not much "characteristic" there to use to identify an event, is there?

If that top set of zeroes aren't zeroes, then that's background noise, not detonation, and if the bottom set aren't zeroes, they're background + reflections of the detonation off the local environment, attenuated by the reflection and delayed by the longer, less-direct route (due to the reflection) delayed by the speed of sound.

And it *is* sound that your microphone records, so please drop the "distinction between sound and shockwaves" bs.

(Aimed at AlK, not you, Chainsaw.)
David B. Benson
Consider again the question of the slow decay of WTC 1 until t0, the moment of collapse initiation.

We will use the crush-down equation in normalized form, with a stretch (squash) of 0:

ZZ" + (Z')^2 - Z = F(Z)

to first note that in the undamaged tower, F(Z) = Z is the situation with no drop. Now assume, from work of poster NEU-FONZE, that the drop grow exponentially over time,

Z = a*exp(bt)

where a = Z0 is the relative elevation (measured from the top) of the buckling portion of the exterior walls. We have

Z' = bZ and Z" = b^2Z

so pluging into the crush-down equation and re-arranging,

Z(2b^2Z - 1) = F(Z)

which holds until the capacity limit of the supporting structure is reached and collapse commences. Since the resisting force must be positive,

2b^2*a*exp(bt) > 1

and at t = 0,

b > sqrt(1/(2a)) = 1.69 (in normalized units).

Now this is not what I previously put into the program, so I'll retry it with this equation for the force.

I want to thank poster einsteen and also Carter Elliot for motivating me, each in their own way, to properly think this through.
David B. Benson
Oops. The resisting force must be negative (upwards), so

2b^2*a*exp(bt) < 1
David B. Benson
What a surprise!

There is enough data to show that the linear force hypothesis is strongly to be preferred to that worked out in the previous two posts. While this does not rule out the theory developed by NEU-FONCE, it strongly suggests that another hypothesis does about ten times as well in explicating the data.
OneWhiteEye
QUOTE (David B. Benson+Nov 12 2007, 09:10 PM)
There is enough data to show that the linear force hypothesis is strongly to be preferred to that worked out in the previous two posts.  While this does not rule out the theory developed by NEU-FONCE, it strongly suggests that another hypothesis does about ten times as well in explicating the data.

That sounds important. What sort of physical interpretation does the linear force hypothesis have considering the structure, etc? At least, how does it differ from NEU-FONZE's theory?

PS an extraction on the two center antenna dishes just finished as I wrote the above. No new technology employed yet, same stuff as the F4 tail work. We'll see how the data (in this case, frames 720-930) comes out - in just a few. (Edit: cruddy, in fact; re-running with new thresholds)
David B. Benson
QUOTE (OneWhiteEye+Nov 12 2007, 02:29 PM)
What sort of physical interpretation does the linear force hypothesis have considering the structure, etc?

At least, how does it differ from NEU-FONZE's theory?

It says that the force is F(Z) = Z(1-a(Z-Z0)) for parameter a such that the standard deviation is minimum, sd = 0.012 meters. Since F(Z) = Z describes a stable structure's resistance, it implies that the resistance has reached the critical maximum that the structure can supply and declines over time. Not what I had expected and indeed, there might be a better function to use for the force.

NEU-FONZE showed that under certain assumptions, Z is an exponential in time. I showed in the prior posts the consequences for the force.
OneWhiteEye
QUOTE (David B. Benson+Nov 12 2007, 10:02 PM)
It says that the force is F(Z) = Z(1-a(Z-Z0)) for parameter a such that the standard deviation is minimum, sd = 0.012 meters.  Since F(Z) = Z describes a stable structure's resistance, it implies that the resistance has reached the critical maximum that the structure can supply and declines over time.  Not what I had expected and indeed, there might be a better function to use for the force.

NEU-FONZE showed that under certain assumptions, Z is an exponential in time.  I showed in the prior posts the consequences for the force.

Ok, thank you, that helps. My understanding of the exponential form is that it is the failure of an ever increasing number of supports per unit time as the load is redistributed amongst the fewer remaining supports. The linear form - I'm not sure I have a mental picture of that (but is that even important?)

Does accurate subpixel data help? The next run was pretty good.

XY data (frames, pixels) for center two dishes - Frames 720-930 - X horizontal blue, Y vertical green

GIF animation showing calculated x,y center AND pixels contributing to calculation

There are known improvements to make, most notably on the technique itself as this is still one pass per pixel, no intelligence except channel brightness tests. Camera jitter can possibly be removed/minimized directly after analysis on the 101 AveofA facade. Despite the shortcomings, I believe it is the best to date and essentially correct wrt overall magnitude.
David B. Benson
QUOTE (OneWhiteEye+Nov 12 2007, 03:37 PM)
My understanding of the exponential form is that it is the failure of an ever increasing number of supports per unit time as the load is redistributed amongst the fewer remaining supports.

The linear form - I'm not sure I have a mental picture of that (but is that even important?)

Does accurate subpixel data help?

Yes. This is what everybody thought ought to occur.

At this stage, no, it doesn't matter.

Yes! Of course it will! Calculation is only conjecture without supporting data. (I'm not quite ready for it yet, however.)
OneWhiteEye
Doing only the top dish was even better, as the above animation would suggest (the self-checking feature of this analysis is a plus).

XY data (frames, pixels) for center TOP dish - Frames 720-930 - X horizontal blue, Y vertical green
David B. Benson
QUOTE (OneWhiteEye+Nov 12 2007, 04:09 PM)
Doing only the top dish was even better, as the above animation would suggest (the self-checking feature of this analysis is a plus).

XY data (frames, pixels) for center TOP dish - Frames 720-930 - X horizontal blue, Y vertical green

This is very good. Looking at it suggests that my t0 is a bit too late. This might explain some of the problems.
David B. Benson
Another poor fit: I used a S-curve, arctan. In detail,

F(Z) = Z(1- a*(pi/2 + arctan(b*(Z-c))))

The best bit occurs when b*(Z-c) is quite negative, so the arctan is almost -pi/2 and the 'curve' is essentially constant. So this looks just like the attempts to use F(Z) = kZ, and gives equally bad results, about the same as the exponential.

David B. Benson
Broomsticks don't work well either ---

Assume the south wall of WTC 1, in the bow-in area, can be simplified to two rods pinned top and bottom and to each other in the middle, as in

|
|

with a non-linear spring in the middle which holds the rods in the vertical position until enough load is applied at the top, at which time the spring allows the bow-in, as in

\
/

and holds that position so long as the load does not increase. But at that small angle, say x, the center of mass of the entire top block shifts slightly to the left, by (1/2)sin(x), increasing the load on the rods and spring. The larger load can equally well be viewed as a declining resistive force:

F(Z,x) = Z(1 - a*sin x)

for some parameter a.

The small angle x is given by

x = arccos(1-delta)

where delta = (Z-Z0)/b

for parameter b representing the length of each of the rods.

Simple, possibly even elegant, but it is substantially less explanatory of the data than the merely linear

F(Z) = Z(1- k(Z-Z0))

although no physical understanding of this equation seems to be forthcoming yet...
wcelliott
DBB -

I appreciate the fact that you derived the equation that I was too lazy to derive myself.

The notion that I'd had when proposing it was that it would (I'd guessed) have provided a descent-versus-time that would've described the interval prior to t0, where the height of the tower descended (somehow) by 20cm in the time between impact and t0. The notion being that it would start out immeasurably slow but would pick up speed until the collapse speeds were apparent.

The angle-rate in the two-broomstick model would be a function of the angle itself (from vertical), accelerating as the Cg (at the hinge-point) displaced from the vertical axis above the point of support.

It may well be that the solution to this problem is a differential equation, which would explain the exponential term in the curve-matched equation you derived.

Just a thought, and you have my apologies for my laziness. (It's an equation I should've derived myself when I proposed the model.)
David B. Benson
QUOTE (wcelliott+Nov 13 2007, 02:07 PM)
... the exponential term in the curve-matched equation you derived.

... you have my apologies for my laziness.

These are possible forms of the resistive force used in solving the B&V crush-down equation and finding the best fitting values of parameters. Earlier I tried a exponential form and that was strongly worse that the linear form. This sin form is better than that, but still substantially worse than the linear form.

David B. Benson
Just checked that at no time up to t0 was the (linearly declining) force zero. So there is never even a millisecond of free fall.
David B. Benson
Time in seconds; measured drop in meters; calculated drop (linearly declining force model) in meters; speed in meters per second.

CODE

-3.94 0.000 0.000 0.000
-3.28 0.022 0.000 0.000
-3.25 0.000 0.000 0.000
-2.70 0.039 0.000 0.001
-2.59 0.000 0.001 0.001
-2.46 0.000 0.001 0.002
-2.01 0.039 0.002 0.005
-1.90 0.022 0.003 0.006
-1.86 0.000 0.003 0.007
-1.54 0.058 0.006 0.014
-1.46 0.022 0.007 0.016
-1.28 0.000 0.011 0.025
-1.11 0.022 0.016 0.036
-1.05 0.058 0.019 0.041
-0.79 0.000 0.033 0.073
-0.77 0.022 0.034 0.076
-0.64 0.039 0.046 0.103
-0.45 0.065 0.070 0.156
-0.38 0.063 0.082 0.181
-0.25 0.106 0.108 0.238
-0.21 0.130 0.120 0.264
0.00 0.190 0.189 0.418
0.00 0.260 0.189 0.418

Note: The times for the second column is slightly different (up to 3 milliseconds) from the times for the third and fourth columns. This clearly makes little difference.
David B. Benson
Ignore the last line, a program oddity only.
David B. Benson
Seffen's equation (12) does such a bad job of matching the data that I may have misunderstood the role of beta, having taken it to be (Z-Z0).
einsteen
I forgot if someone already determined the acceleration of the Landmark tower ? I remember that OneWhiteEye's plots almost fitted perfectly but they were scaled.

ps. I've uploaded the "RAW" file again because the original one was expired http://www.megaupload.com/?d=6F72WLB8
David B. Benson
Aha! Seffen's beta = s(Z-Z0)
and with this, his equation (12) reduces to the B&V crush-down equation. So what he has is quite a nice bit of work.
wcelliott
It's probably already been posted, but does anybody know off the top of their head what the *max-load/sqft* was for the WTC towers? Plus some idea of what the design margin was...

You wouldn't expect a hi-rise like the WTC to allow a tenant to store gravel in their rental space, so I'd expect that figure to be somewhere in their lease agreement. Likewise, an average #/sqft would be one value, and a peak (for heavy office items like safes) to be another. It'd be a moot issue in most situations, but I'd think it'd be critical when slabs of concrete from the floor above would be landing on relatively strong pieces of office furniture, like safes, which would tend to focus the force into small footprints on the floor, exceeding peak load limits (including their margins).

Kinda like the "fat lady in high heels" leaving divots in marble floors.

(BTW, the safes I'm referring-to are the Moslers that look like filing cabinets, but are made of plate-steel, used routinely for storing sensitive/classified documents.)
David B. Benson
QUOTE (wcelliott+Nov 15 2007, 01:52 PM)
It's probably already been posted, but does anybody know off the top of their head what the *max-load/sqft* was for the WTC towers? Plus some idea of what the design margin was...

Whatever is standard for office space. Maybe 22 lb/sqft? It's in NCSTAR1--2A somewhere.

But I doubt it matters much. The truss seats were not designed to handle the excess energy provided by the impact of the crushed materials above.
wcelliott
QUOTE
But I doubt it matters much. The truss seats were not designed to handle the excess energy provided by the impact of the crushed materials above.

Agreed.
Al Khwarizmi - step-by-step
trippy - the THERMATE TORCH AT GROUND ZERO guy, lied again:
================
I find this part of the post especially amusing, because it was not that long ago that Al was trying to convince me that devices such as this did not exist, and were not used in the transport of materials out of ground zero.
===============

I find this lie particularly amusing.

Note the absence of direct quotations from the liar.

I think you should be warned against lying, Trippy, because lying for the purpose of character assassination isn't science.

Is it?

========================================

And I am still waiting from your references wcelliot
But I am not waiting for yet another authoritarian assertion.

I am not waiting for a chemical chain reaction either - I am waiting for a real world reference to a 10 microsecond duration for an explosive pressure pulse.

Note that your fellow conspirator Arthur posted a pulse that endured for 3.3 milliseconds, while your fellow conspirator Trippy posted a pulse that endured for .67 seconds.

Note that I will continue to request a reference until you provide one, or withdraw your claims.

Note that these requests will accumulate with your unsubstatiated claims, so that my list now includes
• a 10 microsecond pulse in air (not the chemical reaction - a chemical reaction isn't a shockwave)
• DARPAS request for a microphone tailored for recording explosions, and
• propagation of sound in air as Direct Current.

Note bene, wcelliot.
Trippy
QUOTE (Al Khwarizmi - step-by-step+Nov 16 2007, 04:25 PM)
trippy - the THERMATE TORCH AT GROUND ZERO guy, lied again:
================
I find this part of the post especially amusing, because it was not that long ago that Al was trying to convince me that devices such as this did not exist, and were not used in the transport of materials out of ground zero.
===============

I find this lie particularly amusing.

Note the absence of direct quotations from the liar.

I think you should be warned against lying, Trippy, because lying for the purpose of character assassination isn't science.

Is it?

========================================

See... Here's what's really amsuing.

First we have Alwhatshisname claiming the following in this post that:

QUOTE (Al Khwarizmi - step-by-step+Oct 22 2007, 07:48 PM)

Also, Trippy, learn to REFERENCE YOUR CLAIMS.

I can not find such a thing as a "thermate cutter" for sale anywhere on earth.
QUOTE
Did you mean: "thermite cutter"

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Forums - WTC molten metal question...
Thermate cutter charges, used by the US military, used on the WTC towers and ... There is no scientific way to disapprove that thermate cutter charges were ...
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Re: metallic microspheres 5% of WTC dust
But that would seem to imply that there were thermate cutter charges ... thermate cutter charges all over the place. Hence if the cutter charges ...
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and - "Your search - "thermite cutter torch" - did not match any documents."
and - "Your search - "thermate cutter torch" - did not match any documents."

Capice??

Then we have him making this post:

QUOTE (->
 QUOTE Did you mean: "thermite cutter"  In the Name of All who Died on 9/11, We Must Act Now « Friends of ...After all, how would the FDNY know that Building 7 was rigged with thousands of thermate cutter charges to “pull”? Does that not suggest that the FDNY ...21stcenturycicero.wordpress.com/2007/09/11/in-the-name-of-all-who-died-on-911-we-must-act-now/ - 156k - Cached - Similar pagesTruthBurn: Updates Sept. 6, 2007I did get one bid from a shadowy tech person with ex-defense contacts in Virginia to build 2 sol-gel thermate cutter charges. The price was \$10000.00 per ...911truthburn.blogspot.com/2007/09/updates-sept-4-2007.html - 91k - Cached - Similar pagesBPVideoI believe that the proposal I outline here can draw more attention to the notion of thermate cutter charges being used to bring down the World Trade ...bpathvideo.blogspot.com/ - 43k - Cached - Similar pagesForums - WTC molten metal question...Thermate cutter charges, used by the US military, used on the WTC towers and ... There is no scientific way to disapprove that thermate cutter charges were ...www.rottentomatoes.com/vine/showthread.php?t=480283 - 53k - Cached - Similar pagesRe: metallic microspheres 5% of WTC dustBut that would seem to imply that there were thermate cutter charges ... thermate cutter charges all over the place. Hence if the cutter charges ...sci.tech-archive.net/Archive/sci.physics/2007-06/msg00109.html - 10k - Cached - Similar pages

and - "Your search - "thermite cutter torch" - did not match any documents."
and - "Your search - "thermate cutter torch" - did not match any documents."

Capice??

Then we have him making this post:

============================
Flashback:
common sense:
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
Yet none of you can explain your thermite nonsense. How did the thermite burn SIDEWAYS through the steel?
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

Linear_Thermite.jpg

So as it turns out, it's not me that's lying after all.

In the first post he claims that no such device is for sale anywhere on earth, followed by an implication that such a device doesn't exist, period.

Then in the second post he posts a picture of this very type of device, and then goes on to accuse me of lying for pointing out the contradiction in his posts.
Trippy
I'm not going to dignify that second 'post' except to say that if Al had bothered to actually read the Wikipage it aknowledges the use of the term to also refer to a medical ultrasound.

None of this changes the fact that Sonogram, Sonograph, and Spectrograph are all used interchangeably.
wcelliott
QUOTE
And I am still waiting from your references wcelliot
But I am not waiting for yet another authoritarian assertion.

I am not waiting for a chemical chain reaction either - I am waiting for a real world reference to a 10 microsecond duration for an explosive pressure pulse.

Note that your fellow conspirator Arthur posted a pulse that endured for 3.3 milliseconds, while your fellow conspirator Trippy posted a pulse that endured for .67 seconds.

Note that I will continue to request a reference until you provide one, or withdraw your claims.

Note that these requests will accumulate with your unsubstatiated claims, so that my list now includes
a 10 microsecond pulse in air (not the chemical reaction - a chemical reaction isn't a shockwave)
DARPAS request for a microphone tailored for recording explosions, and
propagation of sound in air as Direct Current.

Note bene, wcelliot.

Note bene, idiot, I've explained ALL of this MORE THAN ONCE.

Are you DENSE?!?

When you take the 26,700 feet-per-second detonation speed WHICH I'VE ALREADY PROVIDED THREE REFERENCES FOR (AND YOU CAN GOOGLE A DOZEN MORE JUST AS EASILY AS I CAN) and you RUN THE CALCULATIONS for a FOUR INCH BLOCK - YOU GET 10 MICROSECONDS!!! MAYBE LESS, DEPENDING ON WHERE YOU PUT THE DETONATOR.

I'VE ALSO EXPLAINED THAT ANY RECORDING OF AN EXPLOSION THAT LASTS LONGER THAN 10 MICROSECONDS IS ARTIFACT, FROM THE REFLECTIONS OF THE INITIAL 10 MICROSECOND BLAST OFF THE ENVIRONMENT, AND ACTUALLY DERIVED THE "N-SHAPED" SLOPE. THE "N-SHAPE" IS WHAT YOU GET WHEN YOU GET REFLECTIONS FROM THE ENVIRONMENT. Whether that's 3.3milliseconds of artifact or 3.3seconds of artifact, it's all artifact except the first 10microseconds.

I said originally that I remembered the DARPA RFP but those go back a long way, I've been reading DARPA RFPs for twenty years, and they've only recently put up a website, and they don't archive everything. I already said that I wasn't having any luck finding that particular RFP. But I'll tell you what, I'm currently working on a DARPA program, so the next time I run into the DARPA program manager, I'll ask him about it and see if he knows where it is.

And I never said anything about sound generating electrical current, the "DC" term, as I've already explained (needlessly, for everyone BUT YOU). just refers to the zeroth-frequency component AS I'VE ALREADY EXPLAINED!

And, just so you know, I've reported you for calling people liars, when the real problem is that YOU'RE JUST TOO STUPID TO UNDERSTAND PLAIN ENGLISH!!!
QUOTE (Al Khwarizmi - step-by-step+Nov 15 2007, 10:25 PM)
Note that your fellow conspirator Arthur posted a pulse that endured for 3.3 milliseconds, while your fellow conspirator Trippy posted a pulse that endured for .67 seconds.

So Al, now you think we are CONSPIRATORS in 9/11?????

Whoooo Hoooo, break out the tin foil.

Arthur

wcelliott
QUOTE
Whoooo Hoooo, break out the tin foil.

Even people who are *nuts* are still supposed to be capable of doing simple math!

Hey Al, what's (0.25feet)/(26,700 feet/second) in YOUR universe?
Chainsaw,
QUOTE (wcelliott+Nov 16 2007, 08:33 AM)

Note bene, idiot, I've explained ALL of this MORE THAN ONCE.

Are you DENSE?!?

When you take the 26,700 feet-per-second detonation speed WHICH I'VE ALREADY PROVIDED THREE REFERENCES FOR (AND YOU CAN GOOGLE A DOZEN MORE JUST AS EASILY AS I CAN) and you RUN THE CALCULATIONS for a FOUR INCH BLOCK - YOU GET 10 MICROSECONDS!!!  MAYBE LESS, DEPENDING ON WHERE YOU PUT THE DETONATOR.

I'VE ALSO EXPLAINED THAT ANY RECORDING OF AN EXPLOSION THAT LASTS LONGER THAN 10 MICROSECONDS IS ARTIFACT, FROM THE REFLECTIONS OF THE INITIAL 10 MICROSECOND BLAST OFF THE ENVIRONMENT, AND ACTUALLY DERIVED THE "N-SHAPED" SLOPE.  THE "N-SHAPE" IS WHAT YOU GET WHEN YOU GET REFLECTIONS FROM THE ENVIRONMENT.  Whether that's 3.3milliseconds of artifact or 3.3seconds of artifact, it's all artifact except the first 10microseconds.

I said originally that I remembered the DARPA RFP but those go back a long way, I've been reading DARPA RFPs for twenty years, and they've only recently put up a website, and they don't archive everything.  I already said that I wasn't having any luck finding that particular RFP.  But I'll tell you what, I'm currently working on a DARPA program, so the next time I run into the DARPA program manager, I'll ask him about it and see if he knows where it is.

And I never said anything about sound generating electrical current, the "DC" term, as I've already explained (needlessly, for everyone BUT YOU). just refers to the zeroth-frequency component AS I'VE ALREADY EXPLAINED!

And, just so you know, I've reported you for calling people liars, when the real problem is that YOU'RE JUST TOO STUPID TO UNDERSTAND PLAIN ENGLISH!!!

Shh, AL does not need to see this, it might confuse him since he is an expert professional, just keep it to yourself.

the recording system, and the O.T. estimation is based on measuring the relative propagation time of shock waves to piezoelectric sensors (Δt = 0.445sec, see Fig. 7) and the absolute GPS time of the waves arrival to a hydrophone (see Fig.8), co-located with the sensors (see Chapter 7.2 below). For the largest explosion we obtained the exact moment of detonating electric fuses, connected to detonating cord, that initiated the charge (see Fig. 3). The finite detonation time of the detonating cord (the length of about 70-75 m), estimated as about 10 msec (~ 70m : 7000m/sec), was also considered. The recording system time was continuously synchronized with GPS and under 500 samples per second provided an accuracy better than 5 msec.

Remember reading about this when I helped Ashland oil company do sound studies from explosions on my own property in the late 1990s.

It takes 10 msec just for the detonation cord to go off, then the explosive has to follow that in another 10 msec or more!
wcelliott
Chainsaw -

I wasn't assuming that the C-4 charge was detonated by det-cord, but by an electric detonator.

If you have a recording of the det-cord-detonated explosive, then part of the recording is of the det-cord going-off (which isn't part of any "characteristic waveform for explosives", as AlK's been asserting exists), it would be an artifact of the specific instance of that particular set-up.

If the explosives detonated were blocks of C-4 of the size specified (about 4-inches), then the blocks detonated at the rate of 26,700 feet-per-second, and that ends up taking about 10 microseconds for the C-4 to go from solid to gas. Any sound recording of that blast would be one sharp spike associated with that 10 microsecond blast, plus the myriad reflections of that blast's shockwave reflecting off all surfaces of its environment, all those reflections delayed from the propagation-path, and attenuated by the reflection coefficient of the material, and also simply lower-intensity as the shockwave expanded spherically, given that the same amount of energy is being distributed over a spherical surface expanding at the speed of sound (once outside the immediate "blast zone").

The CENTRAL POINT of all these discussions that everyone else seems to miss is that all recordings of explosions provided are recording of the REFLECTIONS of the detonation off the surfaces of the blast's environment. Change the nature of the environment and you'll have a different-sounding explosion. No "characteristic waveform" for an explosion exists, other than a single spike that's on the order of 10 microseconds wide and too intense for most microphones to detect without saturation. Any audio digital recording will be undersampled (a 40kHz sampling rate is sufficient for 20kHz bandwidth, and 1/40kHz = 25 microseconds) so you get ONE SAMPLE that's at MAXVAL plus DEAD SILENCE before and after.

If someone wishes to assert that explosives have some "characteristic waveform", then they need to provide a recording that samples at a rate adequate to characterize the waveform that starts and stops in about 10 microseconds and has enough samples in that interval to pick up whatever waveform is "characteristic" to that blast. (Which, itself, will be driven by the shape of the charge - rectangular block/sphere/blob, and where the detonator was placed - center/edge/somehwere in between.)

Someone post a link to an explosive charge going-off that has no solid structures/materials within 100 feet (including the ground itself), and show me how that waveform compares to an explosive going off inside a structure. Aside from the initial spike, there will be NO CORRELATION.
David B. Benson
Turns out that Seffen's equation (12) expresses the same dynamics as what I have called modified Beck, not B&V. Since Seffen uses a compression ratio (inverse stretch), I went ahead to do a comparison of the two somewhat different dynamics. Other than slightly different parameters, the two models agree essentially equally well with the data.
David B. Benson
Only the Seffen crush-down equation or else the B&V crush-down equation correctly describes the dynamics.

But just now I cannot tell which.
wcelliott
Chainsaw, I just want to be clear that I didn't mean for my rant to sound like I was upset with you personally, I'm just psst that AlK will read what you posted and try to bludgeon me with a warped interpretation of it.
newton
QUOTE (David B. Benson+Nov 17 2007, 12:30 AM)
Only the Seffen crush-down equation or else the B&V crush-down equation correctly describes the dynamics.

But just now I cannot tell which.

David B. Benson
QUOTE (newton+Nov 16 2007, 06:43 PM)
...neither is right.

Then with your vast knowledge of Newtonian dynamics, you'll be able to write the paper proving that assertion and having it published in the ASCE J. Engg. Mechanics.

memeticverb
QUOTE (wcelliott+Nov 16 2007, 09:21 PM)
Chainsaw -

I wasn't assuming that the C-4 charge was detonated by det-cord, but by an electric detonator.

If you have a recording of the det-cord-detonated explosive, then part of the recording is of the det-cord going-off (which isn't part of any "characteristic waveform for explosives", as AlK's been asserting exists), it would be an artifact of the specific instance of that particular set-up.

If the explosives detonated were blocks of C-4 of the size specified (about 4-inches), then the blocks detonated at the rate of 26,700 feet-per-second, and that ends up taking about 10 microseconds for the C-4 to go from solid to gas. Any sound recording of that blast would be one sharp spike associated with that 10 microsecond blast, plus the myriad reflections of that blast's shockwave reflecting off all surfaces of its environment, all those reflections delayed from the propagation-path, and attenuated by the reflection coefficient of the material, and also simply lower-intensity as the shockwave expanded spherically, given that the same amount of energy is being distributed over a spherical surface expanding at the speed of sound (once outside the immediate "blast zone").

The CENTRAL POINT of all these discussions that everyone else seems to miss is that all recordings of explosions provided are recording of the REFLECTIONS of the detonation off the surfaces of the blast's environment. Change the nature of the environment and you'll have a different-sounding explosion. No "characteristic waveform" for an explosion exists, other than a single spike that's on the order of 10 microseconds wide and too intense for most microphones to detect without saturation. Any audio digital recording will be undersampled (a 40kHz sampling rate is sufficient for 20kHz bandwidth, and 1/40kHz = 25 microseconds) so you get ONE SAMPLE that's at MAXVAL plus DEAD SILENCE before and after.

If someone wishes to assert that explosives have some "characteristic waveform", then they need to provide a recording that samples at a rate adequate to characterize the waveform that starts and stops in about 10 microseconds and has enough samples in that interval to pick up whatever waveform is "characteristic" to that blast. (Which, itself, will be driven by the shape of the charge - rectangular block/sphere/blob, and where the detonator was placed - center/edge/somehwere in between.)

Someone post a link to an explosive charge going-off that has no solid structures/materials within 100 feet (including the ground itself), and show me how that waveform compares to an explosive going off inside a structure. Aside from the initial spike, there will be NO CORRELATION.

Good points.

Conclusive evidence for explosives isnt going to come through analyses of sound recordings, but in the proof of events like the basements getting shredded, and the squibs exceeding what was possible without them.

Video proof of Basement Explosions

Direct Evidence for Explosives, by Crocket Grabbe PhD.
wcelliott
Well, at least the author argued against the "High Energy Lasers" theory.

He missed out on a couple of other pretty obvious points, though, like considering what happened to the air inside the towers when the towers were collapsing. I supposed he expected to find dense layers of solidified air in the basement trapped between the floors' rubble.

Chainsaw,
QUOTE (wcelliott+Nov 16 2007, 09:21 PM)
Chainsaw -

I wasn't assuming that the C-4 charge was detonated by det-cord, but by an electric detonator.

If you have a recording of the det-cord-detonated explosive, then part of the recording is of the det-cord going-off (which isn't part of any "characteristic waveform for explosives", as AlK's been asserting exists), it would be an artifact of the specific instance of that particular set-up.

If the explosives detonated were blocks of C-4 of the size specified (about 4-inches), then the blocks detonated at the rate of 26,700 feet-per-second, and that ends up taking about 10 microseconds for the C-4 to go from solid to gas.  Any sound recording of that blast would be one sharp spike associated with that 10 microsecond blast, plus the myriad reflections of that blast's shockwave reflecting off all surfaces of its environment, all those reflections delayed from the propagation-path, and attenuated by the reflection coefficient of the material, and also simply lower-intensity as the shockwave expanded spherically, given that the same amount of energy is being distributed over a spherical surface expanding at the speed of sound (once outside the immediate "blast zone").

The CENTRAL POINT of all these discussions that everyone else seems to miss is that all recordings of explosions provided are recording of the REFLECTIONS of the detonation off the surfaces of the blast's environment.  Change the nature of the environment and you'll have a different-sounding explosion.  No "characteristic waveform" for an explosion exists, other than a single spike that's on the order of 10 microseconds wide and too intense for most microphones to detect without saturation.  Any audio digital recording will be undersampled (a 40kHz sampling rate is sufficient for 20kHz bandwidth, and 1/40kHz = 25 microseconds) so you get ONE SAMPLE that's at MAXVAL plus DEAD SILENCE before and after.

If someone wishes to assert that explosives have some "characteristic waveform", then they need to provide a recording that samples at a rate adequate to characterize the waveform that starts and stops in about 10 microseconds and has enough samples in that interval to pick up whatever waveform is "characteristic" to that blast.  (Which, itself, will be driven by the shape of the charge - rectangular block/sphere/blob, and where the detonator was placed - center/edge/somehwere in between.)

Someone post a link to an explosive charge going-off that has no solid structures/materials within 100 feet (including the ground itself), and show me how that waveform compares to an explosive going off inside a structure.  Aside from the initial spike, there will be NO CORRELATION.

Have you ever worked with explosives?
Detcord is used in conjunction with electric detonators the electric detonators only trigger the detcord or other initial shock charge.
There are detonators that trigger directly blasting caps, however they are seldom used with C4.
An electric detonator is only a way to ignite the inital shock charge that sets off the main explosive, usually detcord.

PS. I fully understand your post and it's intent and your right about the shock wave reflections except for the small spike of a detonator initiation like detcord that is often lost in the sound recordings.
wcelliott
In the "explosives brought-down the towers" theory, I've assumed that they aren't thinking that the explosive charges were detonated using det-cord, but rather electrically triggered detonators/"blasting caps".

If there are any loonies out there who want to correct me on their delusions, please advise, I just assumed you're all thinking of some sinister government agent in a trenchcoat and dark sunglasses with a handheld transmitter with a Big Red Button triggering the explosives.

Definitely, if det-cord is detonating the C-4 charge, it makes its own noise, and that would have its own acoustic contribution (which would change from one situation to the next, as its sound would be bouncing all over the environment, too).

I defer to Chainsaw's experience with explosives, which is vastly greater than my own, but I'm not totally ignorant of the subject. My first job out of school was working for Schlumberger Well Services which uses C-4 to perforate well casings, and studying explosives and safe-handling techniques was part of the 13-week training course. Subsequent to that job, I've worked in the defense industry, and have on-occasion interfaced with missile designers and warheads are part of (most of) the system concepts. I'm mainly a "sensors and systems" guy, and I've written software that does the "sonogram/spectrogram/voice-print" conversion from time-based digital signals to spectrum-based signal processing, I've designed a digital signal processor that did acoustic "beamforming", focussing sound from multiple sensors to create a "virtual microphone" positioned anywhere in the environment (software selectable position), and I've computer-modelled sound propagation through various environments. I've also designed acoustic transducers that don't look like acoustic transducers for security applications, so that people doing bug-sweeps wouldn't know what it was if they were handed one.

So I don't consider myself a complete idiot on this particular topic.
David B. Benson
A small point about the final stretch (crush, inverse compaction ratio):

A reasonable estimate for the maximum stretch is about 0.54. Using NEU-FONZE's 6:1 compaction ratio, the final stretch would be 0.09. However my program keeps selecting a starting stretch in the range 0.41--0.51. So saying that is 0.48, the 6:1 compaction ratio gives 0.08. The examples with a stretch of only 0.05 are likely to have been exceptional cases.
Chainsaw,
QUOTE (wcelliott+Nov 17 2007, 05:53 PM)
In the "explosives brought-down the towers" theory, I've assumed that they aren't thinking that the explosive charges were detonated using det-cord, but rather electrically triggered detonators/"blasting caps".

If there are any loonies out there who want to correct me on their delusions, please advise, I just assumed you're all thinking of some sinister government agent in a trenchcoat and dark sunglasses with a handheld transmitter with a Big Red Button triggering the explosives.

Definitely, if det-cord is detonating the C-4 charge, it makes its own noise, and that would have its own acoustic contribution (which would change from one situation to the next, as its sound would be bouncing all over the environment, too).

I defer to Chainsaw's experience with explosives, which is vastly greater than my own, but I'm not totally ignorant of the subject. My first job out of school was working for Schlumberger Well Services which uses C-4 to perforate well casings, and studying explosives and safe-handling techniques was part of the 13-week training course. Subsequent to that job, I've worked in the defense industry, and have on-occasion interfaced with missile designers and warheads are part of (most of) the system concepts. I'm mainly a "sensors and systems" guy, and I've written software that does the "sonogram/spectrogram/voice-print" conversion from time-based digital signals to spectrum-based signal processing, I've designed a digital signal processor that did acoustic "beamforming", focussing sound from multiple sensors to create a "virtual microphone" positioned anywhere in the environment (software selectable position), and I've computer-modelled sound propagation through various environments. I've also designed acoustic transducers that don't look like acoustic transducers for security applications, so that people doing bug-sweeps wouldn't know what it was if they were handed one.

So I don't consider myself a complete idiot on this particular topic.

wcelliott

I had always believed that you had some explosive knowledge, but most of the time C4 which requires a higher generation of energy in shock waves to cause it to explode, is exploded with either detcord or shock tubes not blasting caps.
Blasting caps usually are used on trinitrotoluenes not on C4 or RDX which require a stronger initial bang to ignite the charge than does TNT.
Some people confuse small shock tubes with blasting caps though, however they are not the same.
The benzene ring and three nitrogen covalent bonds make TNT inherently unstable, and easy to trigger, that is probably why the company that you worked for did not use Trinitrotoluene compounds.
You can at some instances recover a detonator signal, but only if the microphone that recovers it is withing very close range, the whole idea is to have the shock wave given off by the detonator, absorbed and trigger the main charge, so the shock waves from detonator do not travel well past the main charge and are extremely week.
All I was trying to point out is that it takes longer than AL claimed for a charge to ignite and burn and trigger the main charge.
I completely under stand what your saying about reflected shock-waves, I am just trying to limit the confusion, so that if some one does find a paper with a double peak, indicative of a detonator discharge before the main blast, it would help the readers of the forum to have an explanation of what they were actually seeing in the Data.
I just wanted people to know that such data does exist, and what it actually means.
Because I expect that AL will attempt to use such data in an argument against your sound argument.
Do not know if this is getting though clear and concisely though, I am just trying to save time by debunking a false argument before AL makes it!
Al Khwarizmi - step-by-step
QUOTE
...in a relatively rare variety of aphasia, jargon aphasia, patients seem to have no anxiety at all about about their verbal deficit.
Daniel Dennett, Consciousness Explained. p.249.

wcelliot
--------------------
______|_________
That's what an explosive detonation looks like in the time domain,

-------------------

That's an assertion you are clearly unwilling to reference. When Trippy and Arthur rushed to your aide as you floundered for evidence, they provided an infrasonic pulse with a duration of 670,000 microseconds, and a shockwave blast with a duration of 3,300 microseconds.

No amount of technical jargon woven into bafflegab can alter the fact that both of these cases contradict your baseless, anti-scientific claim.

When I ask you to reference your claims, you respond with hostility and abuse.

previously
wcelliot:
=========
A point (of many) that goes straight over your head (because it's untrue), is that the acoustic spectrum of a 10microsecond spike goes all the way from DC to a MegaHertz, so it includes spectral energy in all bands, including the audio band (40-20,000Hz).
=========
1) a blast "spike" is not a sound wave, but you still conflate the two.
2) you repeatedly assert a 10µs duration of "spike" without substantiation.
3) Trippy's infrasound N-"spike" endured to the contrary for 2,050,000µs.
4) Arthur's "Typical HE pressure/time curve" for a blast endured to the contrary for 3,300µs
WHY?
5) A 10µs "acoustic" (*cough*) "spike" that produced a wave of DC in the air would be quite fantastical and electrical, but it would not be acoustic.

subsequently:
wcelliot:
====================
And the "DC component" of a spectrum is routine language of the art, everyone (except you) understand it to refer to the zeroth-order component of a spectrum. Given the choice of "DC" or "zeroth-order component of a spectrum", I'll continue to use "DC" for the spectral component at zero frequency.
====================

Terms of the Art.
QUOTE (->
 QUOTE ...in a relatively rare variety of aphasia, jargon aphasia, patients seem to have no anxiety at all about about their verbal deficit.Daniel Dennett, Consciousness Explained. p.249.

wcelliot
--------------------
______|_________
That's what an explosive detonation looks like in the time domain,

-------------------

That's an assertion you are clearly unwilling to reference. When Trippy and Arthur rushed to your aide as you floundered for evidence, they provided an infrasonic pulse with a duration of 670,000 microseconds, and a shockwave blast with a duration of 3,300 microseconds.

No amount of technical jargon woven into bafflegab can alter the fact that both of these cases contradict your baseless, anti-scientific claim.

When I ask you to reference your claims, you respond with hostility and abuse.

previously
wcelliot:
=========
A point (of many) that goes straight over your head (because it's untrue), is that the acoustic spectrum of a 10microsecond spike goes all the way from DC to a MegaHertz, so it includes spectral energy in all bands, including the audio band (40-20,000Hz).
=========
1) a blast "spike" is not a sound wave, but you still conflate the two.
2) you repeatedly assert a 10µs duration of "spike" without substantiation.
3) Trippy's infrasound N-"spike" endured to the contrary for 2,050,000µs.
4) Arthur's "Typical HE pressure/time curve" for a blast endured to the contrary for 3,300µs
WHY?
5) A 10µs "acoustic" (*cough*) "spike" that produced a wave of DC in the air would be quite fantastical and electrical, but it would not be acoustic.

subsequently:
wcelliot:
====================
And the "DC component" of a spectrum is routine language of the art, everyone (except you) understand it to refer to the zeroth-order component of a spectrum. Given the choice of "DC" or "zeroth-order component of a spectrum", I'll continue to use "DC" for the spectral component at zero frequency.
====================

Terms of the Art. MARK LANE: What is a plausible denial?
E. HOWARD HUNT: Denial that is believable.
LANE: Is that a term of art within the CIA?
HUNT: In the intelligence community it means a story that is plausible, it could be believed by a substantial number of people. Plausibly denying, a denial that is believable, that is credible.
LANE: Do you recall testifying on June 28, 1974, in the case of United States versus Ehrlichman, page 761, were you asked these questions, and did you make these answers:

"Question. What was the reason given, or was any reason given, why you and Mr. Liddy couldn't perform this operation?
"Answer. Because of our connection with the White House and the fact that plausible denial would have to be maintained.
"Question. You said plausible denial would have to be maintained?
"Question. Would you explain what you mean by that?
"Answer. "The principle of plausible denial is simply if an operation or action is later disclosed, for example, as an action of the United States government, the government can plausibly deny it, deny any involvement or connection with the action."

Do you recall those questions and answers?

HUNT: Yes.
LANE: Would you accept as a fair definition which you gave, when you testified as to what a plausible denial is?
HUNT: Yes.
---Hunt. vs. Liberty Lobby, Plausible Denial, p.p. 261-262, Mark Lane, 1991

6) DC means Direct Current - it is a term of the electrical art.
7) DC is not part of the audio spectrum (or any spectrum), does not propagate in air, and by definition does not oscillate. A continuous non-modulated voltage that consumes dynamic range, when present in electrical signals used to produce and record sound, is thus represented on spectral distribution graphs as a zero frequency (no sound) component - a non-acoustic artifact of poorly engineered electrical equipment:
QUOTE
Many sound cards record with a slight DC offset, which means that direct current is introduced into the signal by the card, causing the center of the waveform to be off from the zero point in the waveform display. This is seen as the waveform being "shifted" above or below the center line in the Wave Display, and can cause a click or pop to be played at the beginning or end of the file.
---Cool Edit Pro, Glossary

The acoustic spectrum of an explosion will never contain DC, because DC is direct current.
A 10µs "acoustic" (*cough*) "spike" that propagates as DC in the air would be quite fantastical and electrical, but it would not be acoustic.

===================================
Fast Fourier Transform Spectrum Analyser applet: guidance notes
===================================
QUOTE (->
 QUOTE Many sound cards record with a slight DC offset, which means that direct current is introduced into the signal by the card, causing the center of the waveform to be off from the zero point in the waveform display. This is seen as the waveform being "shifted" above or below the center line in the Wave Display, and can cause a click or pop to be played at the beginning or end of the file.---Cool Edit Pro, Glossary

The acoustic spectrum of an explosion will never contain DC, because DC is direct current.
A 10µs "acoustic" (*cough*) "spike" that propagates as DC in the air would be quite fantastical and electrical, but it would not be acoustic.

===================================
Fast Fourier Transform Spectrum Analyser applet: guidance notes
===================================
Add DC level / random noise
You can optionally add a constant DC level (bias or offset) and/or simulated random noise to the signal by checking the appropriate checkbox and entering the amount of the DC offset or noise level (in volts) in the text field. The values chosen should reflect the fact that the basic signal amplitude is fixed [in this applet] at 1V. The effects of adding a DC offset or random noise are discussed later.
[...]

Effect of adding a constant DC level
Select a sine wave signal of frequency 1000 Hz. Check the "Add DC level" check box, enter a value of 0.5 (volts) in the text field for the amount of the DC offset, and plot the signal. The graph should show a sine wave shifted upwards by the 0.5 V offset (remember the sine wave itself has an amplitude of 1 V).
You should find that the spectrum consists of a line at 1000 Hz, due to the sine wave,
together with a line at zero frequency, with a height of 0.5 V.
This zero frequency component is due to the DC level.
--------------------------------------------------
http://www.dsptutor.freeuk.com/index.htm

The acoustic spectrum resulting from an explosion will never contain DC, because DC is electrical not acoustic (akoustikos - to hear).
DC offset is an artifact of poorly engineered equipment in the recording path.

Your calculation of the duration of a chemical reaction is not a reference to the duration of an expanding shockwave, nor is it a reference to the duration or properties of sound produced in the wake of the shockwave. In a world of cause an effect, the duration of a chemical reaction does not determine the duration of any resulting sound. The chemical reaction is not the sound of an explosion.
The shockwave resulting from the chemical reaction is also not the sound of an explosion: nevertheless, your 10 microsecond blast assertion -- contradicting Arthur's "typical" blast duration---requires a real world reference.

i) Please provide a 10 microsecond shockwave reference contradicting that supplied by Arthur, or withdraw your 10 microsecond claim.
ii) Please also provide a reference to DARPAs specification for development of a microphone for recording explosions.

These are your novel claims, and it is your scientific obligation to support them.

stundie
You introduced an analysis by a "sound engineer" who uses non-professional weird terminology (sonogram) and spends a lot of time analysing a fraudulent soundtrack.

The southtower collapse shot, showing rapid inward pull on the perimeter columns of the east face at collapse onset, is quite a famous one. But the soundtrack accompanying the original version of the clip does not include any obvious explosive noises, or crashes or pops. In fact, the original soundtrack has been stripped and replaced.
see for yourself:

When I find doctored recordings masquerading as evidence, I always ask: Who benefits?
Al Khwarizmi - step-by-step
Arthur
--------------------------
Since this time we have developed much better estimates of collapse time and clearly the RATE of fall of the towers was much slower than [Kausel's] free fall.
--------------------------
Did "we" slow down the video playback rate to achieve this miracle of Orwellian Revision?

--------------------------------
Yes, there were many more than 5 floors on fire in each tower.
So its no surprise that given the many shafts that ran all the way to the ground floor coupled with the rapid rate of collapse, that the air, at times, as it got expelled would have been very hot, to capable of creating burns.

--------------------------
You are invoking the same mechanism designed to account for high-velocity jets below the collapse front to explain why people were burnt and blasted by hot air at street level.
The temperature of the pistoned hot air and flames erupting at street level was hot enough to incinerate skin, but it was not hot enough to cause pyroclastic flows of dust and smoke?

Fantastic!

Arthur and the OCT team have done nothing to help us depict this amazing piston mechanism, so I composed this crude sketch based on their amazing powderizing piston-pancakes:

http://www.myfilestash.com/userfiles/alrea...ake_pistons.gif
Is this model hermetically sealed, or fulll of holes?

---------------------------
its HIGHLY LIKELY that at least one [linear thermite/thermate cutter] would have survived the collapse.
---------------------------

I find this claim surprising, given that the black box recorders were allegedly not found.

But since you are claiming that linear thermate cutters might survive collapse, it naturally follows that any linear thermate cutters ejected from the building as a consequence of the jetliner impact might also survive the fall.
I wouldn't think so, but there is a phenomena captured by the Naudet bros that requires some explaining.
Linear thermate cutters might work:

slow motion frames:
http://history-bytes.blogspot.com/2007/10/...-phenomena.html
============================

Also, my post defining the word [url=
http://dictionary.reference.com/search?q=sonogram]"sonogram" from dictionary.com[/url] (spectrum free) was deleted by an anonymous party without explanation or trace, and and I have received a 40% warning level in one installment, also without explanation.
Defamation and calumny and misrepresentation by government shills, on the other hand, is evidently quite acceptable.
Not a very transparent or fair forum, it would seem.
wcelliott
Alk -

You REALLY need to take a physics class.

After you take a remedial READING class.

I've already explained EVERY OBJECTION directed at me in your post, more than once.

None of the other recordings of "explosions" were of the explosives themselves detonating in-absence of reflective surfaces. A loud bang will echo off all surfaces in all directions. If you want to assert that explosives have a "characteristic waveform" then you should, first, record only an explosive going-off, not in a building, not on the ground, not in a bell factory, not in a church's organ pipe...

When you find a recording of an explosive itself going off, THEN let's talk about whether explosions have a "characteristic waveform".

And thanks, lots for your explanation of what "DC current" means. I must've missed that when I got my bachelors' in electrical engineering, and my Masters in electrical engineering.

And when you design sensors for a living, as I do, the term "DC" is routinely understood to refer to the zeroth-frequency component, which, when discussing sound, refers to the ambient pressure of the air (e.g., 14.7psi). Anything that creates more gas in the atmosphere will increase this number (ever so slightly, but it *is* a zeroth-order term).

With explosives, there are two principle characteristics that distinguish them - their energy density (how many Joules/kg they release when they detonate) and their *detonation rate*, which determines how fast the explosive changes from solid to gas, measured as a velocity. Detonation rate is exactly what it sounds like - the speed that the explosive detonates at. Initiate a detonation on one end of a block of C-4, and the detonation propagates from that end to the other at the *detonation rate*, of 26,700 feet/second (give or take). I've already posted a reference for this number. You can Google "C-4 detonation rate" yourself. The energy density of C-4 (or any other high-explosive isn't particularly remarkable, coal releases more energy when it burns than C-4 does when it detonates. What makes it capable of cutting steel is that it releases that energy is a very short amount of time (the "detonation rate"), which makes that unremarkable amount of energy a remarkable amount of *power*. If it released that amount of energy over the course of seconds or even milliseconds (as low-explosives do), it wouldn't do the slightest bit of damage to steel.

As for your continued assertion that a detonation isn't *sound*, OK, what did your microphone detect? Chi? Feng-sui? Prana? Or was the recording made using dowsing rods?

And BTW, you got the warnings for calling us liars, in two separate posts, which I reported. The moderators apparently agreed with me that your rhetoric was abusive and unwarranted.
Al Khwarizmi - step-by-step
metamars
--------------------
K.A. Seffen's (apparently a structural engineer) paper entitled "Progressive Collapse of the World Trade Centre: a Simple Analysis" is available at http://winterpatriot.pbwiki.com/f/seffen_simple_analysis.pdf
-------------------

The most impressive aspect of this paper was the fact that the BBC and this website both claimed that the paper was published when it wasn't. The BBC discretly corrected their report after the winterpatriot blog started making waves about that fact.
Meanwhile, Dr Seffen and the Journal of Engineering refused to answer emails requesting clarification of the publishing date.

And now the paper is available --- but not from the Journal of Engineering.
The paper, instead, can be found at winterpatriots' blog.
A BLOG!
http://winterpatriot.blogspot.com/search/l.../Keith%20Seffen

I am surprised that you don't consider this process to be unusual, metamars.
QUOTE
PhysOrg, September 11, 2007

http://www.physorg.com/news108737007.html
I wonder if Professor Jones could get this level of positive publicity for an unpublished paper?
Al Khwarizmi - step-by-step
http://dictionary.reference.com/search?q=liar
This definition exists for a reason - and I don't mince words.

wcelliot
i) Please provide a 10 microsecond shockwave reference contradicting that supplied by Arthur, or withdraw your 10 microsecond claim.
ii) Please also provide a reference to DARPAs specification for development of a microphone for recording explosions.

These are your novel claims, and it is your scientific obligation to support them.

When you have done so, I will attend to your previous post

If you continue to make unscientific claims without references, I will report you.

beijingyankee
Debate Online: Richard Gage, AE911Truth.org vs. Ron Craig, Explosives Engineer

For a list of upcoming appearances by Richard Gage, see Gage's Appearance Schedule

Chainsaw,
QUOTE (Al Khwarizmi - step-by-step+Nov 18 2007, 06:42 AM)
metamars
--------------------
K.A. Seffen's (apparently a structural engineer) paper entitled "Progressive Collapse of the World Trade Centre: a Simple Analysis" is available at http://winterpatriot.pbwiki.com/f/seffen_simple_analysis.pdf
-------------------

The most impressive aspect of this paper was the fact that the BBC and this website both claimed that the paper was published when it wasn't. The BBC discretly corrected their report after the winterpatriot blog started making waves about that fact.
Meanwhile, Dr Seffen and the Journal of Engineering refused to answer emails requesting clarification of the publishing date.

And now the paper is available --- but not from the Journal of Engineering.
The paper, instead, can be found at winterpatriots' blog.
A BLOG!
http://winterpatriot.blogspot.com/search/l.../Keith%20Seffen

I am surprised that you don't consider this process to be unusual, metamars.
I wonder if Professor Jones could get this level of positive publicity for an unpublished paper?

If Dr. Jones could do competent science I would say he could be published, I would really like to see actual impact studies from him on actual impacts, and how that affects many of his claims.
I would also like to see a more detailed description of the micro spheres, since they appear to be created from fly ash, from brown paper, I would like to know if it was a folder in a filing cabinet or some ones brown bagged lunch!

There are several claims I would like to see Dr. Jones actually back up with actual evidence.

IS it to much to ask that a scientist provide evidence to back up what he claims?
QUOTE (Al Khwarizmi - step-by-step+Nov 18 2007, 12:53 AM)
Arthur
--------------------------
Since this time we have developed much better estimates of collapse time and clearly the RATE of fall of the towers was much slower than [Kausel's] free fall.
--------------------------
Did "we" slow down the video playback rate to achieve this miracle of Orwellian Revision?

Nope.

Good try though.

Arthur
QUOTE (Al Khwarizmi - step-by-step+Nov 18 2007, 01:42 AM)
this website ... claimed that the paper was published when it wasn't.

No, METAMARS claimed it was published.

There is No Official stance taken one way or the other by Physorg.

Once again, trying to make a mountain out of a molehill I see.

Arthur
QUOTE (Al Khwarizmi - step-by-step+Nov 18 2007, 12:53 AM)
--------------------------------
Yes, there were many more than 5 floors on fire in each tower.
So its no surprise that given the many shafts that ran all the way to the ground floor coupled with the rapid rate of collapse, that the air, at times, as it got expelled would have been very hot, to capable of creating burns.

--------------------------
You are invoking the same mechanism designed to account for high-velocity jets below the collapse front to explain why people were burnt and blasted by hot air at street level.
The temperature of the pistoned hot air and flames erupting at street level was hot enough to incinerate skin, but it was not hot enough to cause pyroclastic flows of dust and smoke?

We have no idea what caused the jets below the collapse fronts.

I doubt it was caused in the manner you illustrated, but then who knows EXACTLY what was happening during that collapse? The fact is its FAR beyond our ability to analyse the chaotic nature of the multitude of tower components as they collapsed.
Which is why no one has done so.

My guess is it had to do with structural failures in the elevator system, but it could be no more than a dropping car. You are welcome to your own GUESS, but don't try to use your GUESS as EVIDENCE.

As to the FINAL second of the collapse, where the velocities were very high, then the expulsion rate would have been correspondingly very high, so that someone standing "downwind" from one of the many BURNING OBJECTS on the ground, (like the one you provided a picture of) could easily be BURNT by the flare up caused by this collapse generated wind. There are certainly other possibilities, since in that last second or so of the crush down portion of the collapse would be when the very hot/burning layers of the towers would reach the ground.

So while some small parts of the entire collapse could have had high temp elements associated with it, to catagoize the dust plume as a PYROCLASTIC flow, as has been REPEATEDLY done by the CT'er community is clearly FALSE.

Arthur
NEU-FONZE
wcelliott:

You recently posted:

"Incidentally, Al, I tutored twenty students in Physics in Engineering school, and 17 of them got "A's". The only one who flunked was named "Abdullah Azim". I had several Jewish students, too. I *never* had to explain anyting to them twice."

I don't think we need this kind of remark on a physics forum. Unless you can explain your point - which looks decidedly racist to me - I think you should withdraw it!

QUOTE (Al Khwarizmi - step-by-step+Nov 18 2007, 12:53 AM)
I find this claim surprising, given that the black box recorders were allegedly not found.

But since you are claiming that linear thermate cutters might survive collapse, it naturally follows that any linear thermate cutters ejected from the building as a consequence of the jetliner impact might also survive the fall.
I wouldn't think so, but there is a phenomena captured by the Naudet bros that requires some explaining.
Linear thermate cutters might work:

slow motion frames:
http://history-bytes.blogspot.com/2007/10/...-phenomena.html
============================

No, there would have been far more Linear Thermate cutters and they wouldn't have been riding on a ~ 500 mph jet and they wouldn't have spent over an hour on the fire floors.

So the POINT is, NO EVIDENCE of Linear Thermite cutters was found.

NONE

ZIP

ZILCH

ZERO

Which means any theory that requires Linear Thermate Cutters has to FIRST prove that they were NECESSARY for the towers to collapse.

As NIST, B&Z, B&V etc have shown, they were not.

Arthur

ps (and that picture HARDLY looks like a THERMITE ANYTHING, talk about DESPERATE )
beijingyankee
QUOTE (adoucette+Nov 18 2007, 02:52 PM)
No, there would have been far more Linear Thermate cutters and they wouldn't have been riding on a ~ 500 mph jet and they wouldn't have spent over an hour on the fire floors.

So the POINT is, NO EVIDENCE of Linear Thermite cutters was found.

NONE

ZIP

ZILCH

ZERO

Which means any theory that requires Linear Thermate Cutters has to FIRST prove that they were NECESSARY for the towers to collapse.

As NIST, B&Z, B&V etc have shown, they were not.

Arthur

ps (and that picture HARDLY looks like a THERMITE ANYTHING, talk about DESPERATE  )

"I find this claim surprising, given that the black box recorders were allegedly not found." Al

Ah, but they were found.Black Box Cover-Up

"A 9-11 rescue worker recently came forward to say he was told by FBI agents to “keep my mouth shut” about one of the “black boxes” a fellow firefighter helped locate at ground zero, contradicting the official story that none of the flight and cockpit data recorders were ever recovered in the wreckage of the World Trade Center (WTC) towers.

Honorary firefighter Mike Bellone claims he was approached by unknown bureau agents a short time after he and his partner, Nicholas DeMasi, a retired New York firefighter, found three of the four “black boxes” among the WTC rubble before January 2002..."

The criminal demeanor of the Bush administration is amazing.

No evidence of Linear Termite cutters?

" ABC News reported that, "the temperature at the core of "the pile," is near 2000 degrees Fahrenheit, according to fire officials, who add that the fires are too deep for firefighters to get to."