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wcelliott
QUOTE
in WTC 1 three to four floors were simultaneously in various stages of being crushed

That would tend to result in more of a "freight train" type noise, i.e., concatenation of wide-band noise plus impulses.

One of the towers was associated with the "BANG-BANG-BANG" at the initial part of the collapse, I think it was the other one, and that's more consistent with the mode I was talking about, where the near-simultaneous failures of the floor support structures would've acted like a speaker, with the floors acting like the diaphragm of a giant woofer.

I don't think the Giant Hands Clapping analogy would be quite applicable, as there was a lot of office furniture between the floors that would've crushed at different rates. It would be like trying to clap with corn flakes between your hands.

I did earlier attempt to explain to newton how/why things can collapse all at once without there being an outside source of synchronization, using the metaphor of six pallbearers trying to hold up a heavy casket as long as they could.

The weaker pallbearers would contribute as much as they could for as long as they could, and the stronger pallbearers would've compensated for the weaker ones not hauling their fair share of the load, but eventually, as soon as the net strength of the pallbearers dropped below the weight of the casket, that the casket would be dropped almost simultaneously by all the pallbearers at once.

A similar situation occurred with the WTC at the point of collapse. The overburden was distributed unequally among the remaining structural members, and as the fires weakened them, the most overstressed started giving way earlier than the least overstressed, but at some point the burden exceeded the capacity of the remaining structure, first by a pound (at which point the 150 million-pound block began descending at 1/150,000,000 g's), and later by a ton (2000/150,000,000 g's), and at the point where the block's displacement started becoming noticeable, the structural supports' geometry deviated from design enough that that further diminished the strength of the remaining structure. At some point, the pallbearers were all severely overstressed and they all dropped their loads essentially simultaneously.

I say "essentially simultaneously", but it's actually an ideal example of Chaos Theory, trying to predict which columns would fail first. Initial conditions would dominate in the order of column failure, but once the failures start, they proceed at a constantly accelerating rate until all structural members have failed. (Otherwise known as a "chain reaction".) Each failed structural member would've been stretched or compressed to its limit prior to failure, and the energy of the elastic deformation under load would've been released into the remaining structure when it failed. The structure was closely-coupled to a lot of large flat surfaces ("diaphragms"), so the shocks would've made loud impulse-driven sounds as the floor structures failed "essentially simultaneously".

When an impulse drives a diaphragm, it makes a "BANG!" noise.

Would anyone care to estimate how much energy was available for making those BANG!s? The area of the woofers' diaphragms would just be the office floor area provided above (associated with the lightweight concrete). Most speakers are concentric/circular, and this is more concentric/square, but that should only make a second-order difference. It'd still act like a big woofer.
metamars
QUOTE (NEU-FONZE+Oct 3 2007, 11:38 PM)
Metamars:

Thanks for that very interesting post. Having worked for a government-run nuclear research group in Canada, I can say the same thing happened to us. Nuclear energy is a VERY touchy issue and by the time I left in 2000 we had to be politically correct in everything we did. The main thrust of our work shifted towards producing documents to placate the regulators, not to do good science. Consensus was the order of the day; if you didn't toe the line, you got no funding - it was as simple as that!

You're welcome, but I did nothing but copy and paste. You, on the other hand, stood up for what was right in a professional setting, which entailed considerably more guts and, I suspect, sacrifice. So, thank you. I may not be Canadian, but in a worse case scenario, (core meltdown), I'm quite sure the winds could carry the contamination to Northeastern US (where I live).

We need more people like you in government....

Although it's off topic, do you have an opinion on the late-generation nuclear technology that President Clinton killed? I understand that it was fraught with technical problems, but successfully meeting those problems would have resulted in a nuclear industry that was more robust against subversion into nuclear weapons, and would have allowed the burning of pre-existing nuclear waste, to boot.
zoktoberfest
NEWS YOU WON'T FIND ON CNN

9-11, Six Years Later

By Paul Craig Roberts

09/11/07 "ICH" -- -- On Sept. 7, National Public Radio reported that Muslims in the Middle East were beginning to believe that the 9-11 attacks on the WTC and Pentagon were false flag operations committed by some part of the U.S. and/ or Israeli government.

It was beyond the imagination of the NPR reporter and producer that there could be any substance to these beliefs, which were attributed to the influence of books by U.S. and European authors sold in bookstores in Egypt.

NPR's concern was that books by Western authors questioning the origin of the 9-11 attack have the undesirable result of removing guilt from Muslims' shoulders.

The NPR reporter, Ursula Lindsey, said that "here in the U.S., most people have little doubt about what happened during the 2001 attacks."

NPR's assumption that the official 9-11 story is the final word is uninformed. Polls show that 36 percent of Americans and more than 50 percent of New Yorkers lack confidence in the 9-11 commission report. Many 9-11 families who lost relatives in the attacks are unsatisfied with the official story.

Why are the U.S. media untroubled that there has been no independent investigation of 9-11?

Why are the media unconcerned that the rules governing preservation of forensic evidence were not followed by federal authorities?

Why do the media brand skeptics of the official line "conspiracy theorists" and "kooks"?

What is wrong with debate and listening to both sides of the defining issue of our time? If the official line is so correct and defensible, what does it have to fear from skeptics?

Obviously, a great deal considering the iron curtain that has been erected to protect the official line from independent examination.

Some may think that the 9-11 commission report was an independent investigation, and others will protest that we have the National Institute of Standards and Technology analysis, which explains the collapse of the Twin Towers as a result of airliner impact and fire.

The 9-11 commission was a political commission run by Bush administration insider Philip Zelikow. The National Institute of Standards and Technology is an agency of the U.S. Department of Commerce, the head of which is a member of President Bush's Cabinet.

Zelikow was a member of President Bush's Foreign Intelligence Advisory Board, a neoconservative stronghold. In February 2005, Zelikow was appointed counselor of the U.S. Department of State. Obviously, there was zero possibility that the 9-11 commission would hold any part of the Bush administration accountable for the numerous failures of U.S. government agencies on Sept. 11, much less would the commission investigate for any complicity.

If one looks at the credentials of skeptics compared to the credentials of defenders of the official line, it is impossible to dismiss skeptics as kooks. There are many people with strong imaginations on the Internet, but serious skeptics stick to known facts, known violations of standard procedures and the laws of physics. The vast majority of the people who call skeptics "kooks" are themselves ignorant of physics and have little comprehension of the improbability that such an attack could succeed without either the complicity or complete failure of government agencies.

Over the past six years, the ranks of distinguished skeptics of the 9-11 storyline have grown enormously. The ranks include distinguished scientists, engineers and architects, intelligence officers, air traffic controllers, military officers and generals, including the former commanding general of U.S. Army Intelligence and Security Command, former presidential appointees and members of the White House staff in Republican administrations, Top Gun fighter pilots and career airline pilots who say that the flying attributed to the 9-11 hijackers is beyond the skills of America's best pilots, and foreign dignitaries.

Dr. Andreas von Buelow, former West German minister of research and technology and former state secretary of the federal ministry of defense, said: "The planning of the attacks was technically and organizationally a master achievement. To hijack four airliners within a few minutes and within one hour to drive them into their targets with complicated flight maneuvers! This is unthinkable, without years-long support from secret apparatuses of the state and industry."

Gen. Leonid Ivashov, chief of staff of the Russian armed forces, said: "Only secret services and their current chiefs -- or those retired but still having influence inside the state organizations -- have the ability to plan, organize and conduct an operation of such magnitude. ... Osama bin Laden and al-Qaida cannot be the organizers nor the performers of the Sept. 11 attacks. They do not have the necessary organization, resources or leaders."

Americans might concede that it is unusual that U.S. airport security would fail four times within a few minutes, that U.S. air defenses would fail across the board to intercept the hijacked airliners and that hijackers lacking in flight skills could conduct the exotic flight maneuvers that top gun fighter pilots say are beyond their own skills. Still, there is some possibility, however remote, that Allah could have blessed the hijackers with unbelievable luck.

But when we come to the explanation of the collapse of the Twin Towers, the official story lacks even a remote possibility of being true. Architects, engineers and physicists know that powerfully constructed steel buildings do not suddenly collapse at free-fall or near-free-fall speed simply because they were impacted by airliners and experienced short-lived, low intensity and limited fires.

Physicists also know that there was not enough gravitational energy to pulverize massive concrete into fine dust, to cut massive steel beams into appropriate lengths to be loaded and removed on trucks, and to eject dust and steel beams hundreds of yards horizontally. Physicists know that if intense fire were present throughout the towers sufficient to cause steel to weaken and suddenly collapse, such fires would not have left unburned and unscorched hundreds of thousands of pieces of paper, which floated all over lower Manhattan.

Physicists have raised unanswered questions about the official explanation's neglect of the known laws of physics. Recently, Dr. Crockett Grabbe, a Caltech trained applied physicist at the University of Iowa, observed: "Applying two basic principles, conservation of energy and conservation of momentum, the government explanation quickly unravels. NIST conspicuously ignored these principles in their reports. NIST also ignored the observed twisting of the top 34 floors of the South Tower before it toppled down. This twisting clearly violates the conservation of both linear and angular momentum unless a large external force caused it. Where the massive amounts of energy came from that were needed to cause the complete collapse of the intact parts below for each tower, when their tops were in virtual free fall, is not answered in NIST's numerous volumes of study."

Some of NIST's own scientists are questioning its reports. Dr. James Quintiere, former chief of the fire science division of the National Institute of Standards and Technology, recently said that "the official conclusion that NIST arrived at is questionable" and called for an independent review of NIST's investigation into the collapses of the WTC towers.

Quintiere has called attention to many problems with NIST's investigation and reports: the absence of a timeline, failure to explain the collapse of WTC 7, the spoliation of the evidence of a fire scene, reliance on questionable computer models, the absence of any evidence for the existence of temperatures NIST predicts as necessary for failure of the steel and a Commerce Department legal structure that instead of trying to find the facts "did the opposite and blocked everything."

On Aug. 27, 2007, a prominent member of the National Academy of Sciences and recipient of the National Medal of Science, Dr. Lynn Margulis, dismissed the official account of 9-11 as a "fraud" and called for a new, thorough and impartial investigation.

On Sept. 5, 2007, U.S. Navy Top Gun fighter pilot and veteran airline pilot Ralph Kolstad said that the flight maneuvers attributed to the 9-11 hijackers are beyond his flight skills. "Something stinks to high heaven," declared Kolstad.

When faced with disturbing events, the Romans asked a question, "Cui bono?" Who benefits? This question was conspicuously absent from the official investigation.

Who are the beneficiaries of 9-11? The answer is: the military-security complex, which has accumulated tens of billions of dollars in profits; U.S. oil companies, which hope to get their hands on Iraqi and perhaps Iranian oil; the Republican Party, which saved a vulnerable newly elected president, George W. Bush, viewed by many as illegitimately elected by one vote of the Supreme Court, by wrapping him in the flag as "war president"; the Republican Federalist Society, which used 9-11 to achieve its goal of concentrating power in the executive; Vice President *** Cheney and the neoconservatives, who used the "new Pearl Harbor" to implement their "Project for a New American Century" and extend American hegemony over the Middle East; and right-wing Israeli Zionists, who have successfully used American blood and treasure to eliminate obstacles to Israeli territorial expansion.

In addition to American troops and Iraqi and Afghan civilian casualties, a casualty of the neoconservative "war on terror" is the civil liberties that protect Americans from tyranny. President Bush and his corrupt Department of Justice (sic) have declared our constitutional protections to be null and void at the whim of the executive.

The greatest benefactors of 9-11 are the authoritarian personalities that John Dean says have taken over the Republican Party.

Paul Craig Roberts [email him] was Assistant Secretary of the Treasury in the Reagan Administration. He is the author of Supply-Side Revolution : An Insider's Account of Policymaking in Washington; Alienation and the Soviet Economy and Meltdown: Inside the Soviet Economy, and is the co-author with Lawrence M. Stratton of The Tyranny of Good Intentions : How Prosecutors and Bureaucrats Are Trampling the Constitution in the Name of Justice.

QUOTE
Why do the media brand skeptics of the official line "conspiracy theorists" and "kooks"?

Because they ARE.

QUOTE (->
 QUOTE Why do the media brand skeptics of the official line "conspiracy theorists" and "kooks"?

Because they ARE.

If the official line is so correct and defensible, what does it have to fear from skeptics?

As we have seen demonstrated OVER AND OVER,

NOTHING.

Since they keep coming up with idiotic statements like this:

"the official story lacks even a remote possibility of being true"

and

"Physicists know that if intense fire were present throughout the towers sufficient to cause steel to weaken and suddenly collapse, such fires would not have left unburned and unscorched hundreds of thousands of pieces of paper, which floated all over lower Manhattan. "

Or in this RACIST BS presented by the referenced Biologist Margulis:

QUOTE
19 young Arab men and a man in a cave 7,000 miles away, no matter the level of their anger, could not have masterminded and carried out 9/11

And then reiterated in this diatribe (which has something for everyone)

The Hijackers COULDN'T have flown the planes.

The 19 Arabs COULDN'T have planned it.

BUT

Even if they DID,

QUOTE (->
 QUOTE 19 young Arab men and a man in a cave 7,000 miles away, no matter the level of their anger, could not have masterminded and carried out 9/11

And then reiterated in this diatribe (which has something for everyone)

The Hijackers COULDN'T have flown the planes.

The 19 Arabs COULDN'T have planned it.

BUT

Even if they DID,

steel buildings do not suddenly collapse at free-fall or near-free-fall speed simply because they were impacted by airliners and experienced short-lived, low intensity and limited fires.

And the AMAZING thing is that after this level of BS that they profess to BELIEVE they still wonder why people consider them kooks?

Arthur
newton
QUOTE (wcelliott+Oct 3 2007, 05:47 AM)

Think this one through. You're supposedly some sort of "sound guy", right?

A speaker has a rigid diaphragm and a coil that drives it back and forth.

The better the speaker, the more rigid and bigger the diaphragm, and the more power available to drive that diaphragm back and forth.

You were the one who said your expensive speakers had better fidelity than headphones do, remember? Better at reproducing the sounds of explosions?

Do they run on C-4?

Or do they use electricity to shove that diaphragm?

So, HIGH FIDELITY "EXPLOSION" SOUNDS can come from RIGID DIAPHRAGMS being shoved suddenly by means OTHER THAN EXPLOSIVES.

Look at how those floors of the WTC Towers were made. LARGE FLAT DIAPHRAGMS supported around the middle and around the outside. Those core columns were failing under-load.

What, Mr. Sound Guy, would YOU expect that to sound like? Impulse-shocks delivered to large flat diaphragms? Those floors were like MEGA-WOOFERS being driven with MEGAWATTs of power.

Of course they sounded like explosions. Your speakers don't need explosives to make BANG! noises, and neither did the WTC towers.

Yes, and you're an idiot for believing him (if that's actually what he really said).

make a floor sound like a violin, then. or a triangle.

speakers reproduce soundwaves by moving back and forth at the same relative amplitude and frequency as the source.

floors hitting each other sound like floors hitting each other.

benson, it will only sound like a handclap if they hit perfectly parallel. a slight angle gives more of a crrrrrrassssssssshhhhhhhhh.

explosions have a HUGE percussive spike, followed by ringing in the ears.

"pop, pop, pop, pop" does not describe floor pans randomly hitting each other at angles.

it is the sound of explosions.

"a lie can walk half way around the world while the truth is still tying it's shoes." -mark twain
wcelliott
QUOTE
it is impossible to dismiss skeptics as kooks.

Watch me.

QUOTE (->
 QUOTE it is impossible to dismiss skeptics as kooks.

Watch me.

speakers reproduce soundwaves by moving back and forth at the same relative amplitude and frequency as the source

I know perfectly well how speakers work, newton, I have two degrees in Electrical Engineering, Signals and Sensors' emphasis in my Masters.

That's why I know what an Explosion sounds like. Small volume of explosives turns into big volume of gas, really quickly. At a distance, all you get is a sudden puff of air, the shockwave from the explosive changing from solid to gas, dispersed over the distance.

The amount of air displaced from a 208-foot-square diaphragm when a steel column supporting hundreds of tons could easily exceed the amount of gas produced by several pounds of explosives.

And the easiest way to understand this is to re-read my prior post. Your speaker doesn't run on C-4, does it? It's just a stiff diaphragm being driven mechanically by an electromagnetic coil.

And yet, it goes "BANG!!!".

So, if it goes BANG!!!, by CDiot-logic, that means someone planted EXPLOSIVES in your speaker! Because only explosives go BANG!!!, right?

Trippy
QUOTE (newton+Oct 4 2007, 03:50 PM)
make a floor sound like a violin, then. or a triangle.

Don't be stupid.

That would be physically impossible (well, without a dam site more energy then was available).

Ever wonder why Sub woofers have almost no highend response?
Or for that matter Tweeters have almost no low end response?

It's to do with the mass/volume of air that's required to be moved.

A shockwave sounds like a shockwave. It's that simple.

As WCElliot says, what we describe as sounding like explosives is, quite simply, a sudden displacement of air.
Al Khwarizmi - step-by-step
wcelliot - you were the one who stupefyingly twice asserted that your speakers could not accurately reproduce the sound of an explosion, because they "don't use C4."

I was going to highlight this absurdity by reminding you that my speakers don't run on Billy HOldiay, and therfore can't produce a sound that would be indentified as "the voice of Billy Holiday."

But, of course, my speakers can reproduce the easily identified signature of Billy Holiday.

My speakers can also reproduce, rather well, the signature of a high speed explosion.

Let me Arthurize these statements of fact again:

A LOUD BANG or a LOUD CRASH does NOT SOUND LIKE an EXPLOSION.

I heard the Westgate bridge fall - it DID NOT SOUND LIKE AN EXPLOSION.

Perhaps that is why you were not willing to listen to the recorded sequence of military explosions I offered for comparison to those recorded on 911.
Trippy
QUOTE (Al Khwarizmi - step-by-step+Oct 4 2007, 06:06 PM)
A LOUD BANG or a LOUD CRASH does NOT SOUND LIKE an EXPLOSION.

I heard the Westgate bridge fall - it DID NOT SOUND LIKE AN EXPLOSION.

And yet...

Something heavy dropped onto a large concrete floor produces a noise that sounds like a bang - especially if it happens to be a hard object.

And let me see, what did we have in the WTC? Why large, hard, heavy objects falling onto a concrete floor from a height of between 3 and 4 meters.

Hmmmm.

Collisions do sound like explosions.
wcelliott
QUOTE
My speakers can also reproduce, rather well, the signature of a high speed explosion.

So, if your SPEAKER can go "BANG!" without explosives, then the SOUND of an explosion DOESN'T imply that EXPLOSIVES WERE DETONATED!

GET IT?!?

CDiots have been asserting that because they heard BANG!s coming from the WTC towers, that meant that EXPLOSIVES were detonating.

The floor structure of the WTCs mimic speakers. All it takes to make an "explosion" sound is something driving that diaphragm system with a shock-impulse load.

Look at the "explosion" signal on an O-scope. (Your computer will probably already have that program to display the sound file on-screen.) The "BANG!" part of the explosion is just that first big spike. The rest is resonance, real-time echoes of that first spike that have nothing to do with the explosion itself, and only result because of the echoes in the structure. If the explosive charge were hanging from a string isolated from the surrounding environment (or in an anechoic chamber), the recording of the detonation would be a single, simple spike. How fast that spike rises and falls is more a function of the microphone's bandwidth than anything else (if it is a real explosive). It should be nearly vertical. If it's a low-bandwidth mike or a low-bandwidth recording, it'll have a noticeably slow rise-time.

Anything other than a spike in the "explosion" sound file is either artifacts of the recording system's inadequacies or the resonant characteristics of the environment (or both). But the explosion itself is a just spike, and that can be caused by anything, including a filing cabinet falling through the ceiling or a steel truss failing under load or a slab of concrete breaking in two. Anything that releases a lot of energy in a short amount of time, while connected to a large, flat surface, is going to sound like an explosive going off.

And there was plenty of that going in in the WTC towers as the floors collapsed.

And no explosives causing any of the BANG!s.
Al Khwarizmi - step-by-step
wcelliot:
QUOTE
Something heavy dropped onto a large concrete floor produces a noise that sounds like a bang - especially if it happens to be a hard object.

When a massive portion of the Westgate bridge broke from its connections and plummeted to the ground below, the resulting "bang" did not sound like "an explosion."

Why not?

"A loud bang" or "a loud crash" or "a catastrophic brittle failure" or "something heavy falling on the floor from above" does not adequately describe the sound reproduced by the 2-3 seconds of complex waveform that typically results from the recording of a high-speed explosion of significant magnitude.
High-amplitude very low-frequency artifacts, akin to those produced in the wake of a sonic "boom" or the deep "rumble" (reverberations) of rolling thunder, are not present in a "bang" or a "crash."

Trippy: Grain size in steel is determined not by the rate of cooling, but the temperature at which steel is held before cooling operations are performed.

Al Khwarizmi - step-by-step
wcelliot does 7:
QUOTE
The link has a bunch of interviews in it, including interviews with some of the fire officers that were actually in the WTC7 lobby when it was trashed.

"The building was leaning"
"I saw it bulge!"
" I saw a third of one side scooped out!"

QUOTE (->
 QUOTE The link has a bunch of interviews in it, including interviews with some of the fire officers that were actually in the WTC7 lobby when it was trashed.

"The building was leaning"
"I saw it bulge!"
" I saw a third of one side scooped out!"

================================
Charles Goyette vs. Popular Mechanics' Davin Coburn
================================

GOYETTE: You represent that there is a 3rd of the face to the center and to the bottom, app 10 stories, about 25% of the depth of the building that was scooped out beforehand.

COBURN: yeah - when the Nth twr collapsed, all of the debris and the wreckage from that collapse actually
took a massive chunk out of w.t.c.7, and the first time that, you know, FEMA released its initial report, that wasn't entirely clear.
It wasn't known exactly how much damage that building had sustained, uh, because obviously no planes hit that. It was sort of standing off to the side and then eventually collapsed. Uh, and what we've found through the NIST report and through talking to other experts was that, like you said, about 25% of the bldngs sth face had been carved away from it. And w.t.c.7 had a particularly unique construction because it was built over a Thomas Edison electrical substation. So when they built it up above that the way they aligned the steel columns made them particularly load bearing -- that's not a very good way to say it -- but they were each supporting an awful lot of weight, and so when you start carving away at those, each column that you remove that was destroyed by the wreckage from the Nth twr....

GOYETTE: Well as i describe myself, Davon, I'm an agnostic about a lot of this, and that would be very persuasive to me if it were true. And it may or may not be true, because I look at, so I go,
"Oh, that's interesting, if that's true that would go a long way to explaining what happened to building 7."
So I turn to your pictures in your book about building 7, you got a picture of building 7, but it doesn't show that. So I'm goin', "okay, well instead of someone just asserting that 1/3 of the building was scooped away,
show me the picture."

But you don't show me the picture.

COBURN: Well, you know here again there's an interesting issue that you brought up before.
We have seen pictures, uh, actually.
There are pictures that are the property of the NYPD and other various governmental agencies that we were not given permission to disseminate.
Uh, and that gets back to your original question.
I can not speak for "why"?

GOYETTE: But you got to see 'em?
Popular Mechanics got to see 'em, but the average American citizen can't see 'em?

COBURN: correct

GOYETTE:  Well that's a fine kettle of fish, isn't it?

COBURN: yeah, it certainly is. And that I guess gets back to us, uh, you know, us trying to do our homework, and having the authority to see the pictures -- though what we're allowed to show everyone else, what is chosen to become public domain isn't necessarily our question.

GOYETTE:  Did you see 'em?

COBURN: yeah.

GOYETTE:  Do we have to kill you now?

COBURN: Let's hope not!

GOYETTE: I mean, explain it to me: what did you see there that I can't see?

COBURN: Actually, it was pretty much just what was described, uh, it, you know..

GOYETTE: Well it must be something that would be dangerous for me as an American citizen or a voter to see.

COBURN: Uh, I can not, you know, tell you again...

GOYETTE: Your publishers, I mean, if anyone's concerned about evidence in a criminal case or something  they've done the worst possible thing --- they've shown it to a magazine publisher.

COBURN: Right, uh, and that was done for the purposes of our background research so we could ..

GOYETTE: What about my background research?
Do you see the source of my frustration here?

COBURN: I do.

GOYETTE: I didn't know that we had different classes of citizens.

Assuming for the sake of argument that these few faith-based claims are true, that the building was "scooped-out on one side" and was "leaning" precariously to one side with a "bulge", how would such damage effect the manner in which the building collapsed?

Columns severed on one side...scooped-out on one side....leaning to one side....

The post-911 physics of falling over:
QUOTE
Kausel addressed the oft-asked question of why the towers did not tip over like a falling tree.
"A tree is solid, whereas building is mostly air or empty space; only about 10 percent is solid material. Since there is no solid stump underneath to force it to the side, the building cannot tip over.
It could only collapse upon itself.
"
- When the Twin Towers Fell, Scientific American, October 09, 2001

The pre-911 physics of falling over:
QUOTE (->
 QUOTE Kausel addressed the oft-asked question of why the towers did not tip over like a falling tree."A tree is solid, whereas building is mostly air or empty space; only about 10 percent is solid material. Since there is no solid stump underneath to force it to the side, the building cannot tip over. It could only collapse upon itself."- When the Twin Towers Fell, Scientific American, October 09, 2001

The pre-911 physics of falling over:
Ideally, a blasting crew will be able to tumble the building over on one side,
into a parking lot or other open area.
This sort of blast is the easiest to execute, and it is generally the safest way to go.

Tipping a building over is something like felling a tree.
To topple the building to the north,
the blasters detonate explosives on the north side of the building first,
in the same way you would chop into a tree from the north side if you wanted it to fall in that direction.

Sometimes, though, a building is surrounded by structures that must be preserved.
In this case, the blasters proceed with a true implosion,
demolishing the building so that it collapses straight down
into its own footprint (the total area at the base of the building).[/i]
This feat requires such skill that only a handful of demolition companies in the world will attempt it.

-- How Building Implosions Work, Tom Harris, HowStuffWorks

Which kind of fall does 7 most resemble?
Al,

The first issue appears to be nothing more than COPYRIGHT issues.
I can SHOW you a picture that I have a copyright on but I may choose to not let you PUBLISH that picture.

QUOTE
The post-911 physics of falling over:

QUOTE
Kausel addressed the oft-asked question of why the towers did not tip over like a falling tree.
"A tree is solid, whereas building is mostly air or empty space; only about 10 percent is solid material. Since there is no solid stump underneath to force it to the side, the building cannot tip over.
It could only collapse upon itself."
- When the Twin Towers Fell, Scientific American, October 09, 2001

The pre-911 physics of falling over:

QUOTE
Ideally, a blasting crew will be able to tumble the building over on one side,
into a parking lot or other open area.
This sort of blast is the easiest to execute, and it is generally the safest way to go.

Tipping a building over is something like felling a tree.
To topple the building to the north,
the blasters detonate explosives on the north side of the building first,
in the same way you would chop into a tree from the north side if you wanted it to fall in that direction.

Sometimes, though, a building is surrounded by structures that must be preserved.
In this case, the blasters proceed with a true implosion,
demolishing the building so that it collapses straight down
into its own footprint (the total area at the base of the building).
This feat requires such skill that only a handful of demolition companies in the world will attempt it.

-- How Building Implosions Work, Tom Harris, HowStuffWorks

The FIRST quote was about WTC 1 & 2 and had to do with the physics of a top down collapse. And YES, it had to fall the way it did.

The SECOND quote is about a CD, where one CAN make a building fall somewhat directionally, by placement/timing of the charges.

Comparing the two quotes and thinking you have found "evidence" is SILLY.

Arthur
Grumpy
OneWhiteEye

QUOTE
There are anti-aircraft batteries in DC. I guess they were waiting for a rainy day or perhaps an errant Cessna to use them. No authority for shoot-down? Why the hell not? Does it make any sense to have batteries that can't be used without a lengthy approval procedure (obviously of the order of two hours)? Kinda reminds me of the Iraqi WMD that didn't get used as the country was overrun... except that we actually had such defenses.

I have to ask you where you got the idea that there were anti-aircraft batteries in DC??? Prior to 911 the only time I know of when missiles were stationed in DC was in 1963 during the Cuban Missile Crisis, and those missile could not have hit any missile fired at DC, but they might have been able to hit a plane. They were removed from DC and were not replaced by any other system until AFTER 911. The Pentagon had no air defenses, nor did the White House(well, maybe a Stinger or two in the closet somewhere). That DC had such permanent AA sites is a truther myth, not worthy of serious consideration.

Name a source.

Grumpy
Capracus
QUOTE (Grumpy+Oct 4 2007, 11:47 AM)
OneWhiteEye

I have to ask you where you got the idea that there were anti-aircraft batteries in DC??? Prior to 911 the only time I know of when missiles were stationed in DC was in 1963 during the Cuban Missile Crisis, and those missile could not have hit any missile fired at DC, but they might have been able to hit a plane. They were removed from DC and were not replaced by any other system until AFTER 911. The Pentagon had no air defenses, nor did the White House(well, maybe a Stinger or two in the closet somewhere). That DC had such permanent AA sites is a truther myth, not worthy of serious consideration.

Name a source.

Grumpy
You're essentially correct.
QUOTE
Among the questions being asked here: How could the Pentagon, the center of the U.S. defense establishment, not be prepared to defend itself against an attack by an airplane?

Spokesman Rear Adm. Craig Quigley said the Pentagon has no anti-aircraft defense system that he is aware of. The White House is assumed to have surface-to-air missiles available for protection. The problem, according to past and present government officials, is who makes a decision to fire a missile at an incoming airplane in the midst of downtown Washington.
http://www.usatoday.com/news/nation/2001/09/11/security.htm
wcelliott
QUOTE
When a massive portion of the Westgate bridge broke from its connections and plummeted to the ground below, the resulting "bang" did not sound like "an explosion."

Why not?

"A loud bang" or "a loud crash" or "a catastrophic brittle failure" or "something heavy falling on the floor from above" does not adequately describe the sound reproduced by the 2-3 seconds of complex waveform that typically results from the recording of a high-speed explosion of significant magnitude.
High-amplitude very low-frequency artifacts, akin to those produced in the wake of a sonic "boom" or the deep "rumble" (reverberations) of rolling thunder, are not present in a "bang" or a "crash."

Well, a bridge isn't like a diaphragm, is it? The point I've been trying to make, repeatedly, is that the floors of the WTC were supported around the perimeter and around the inner core, making the floor a suspended diaphragm (four inches thick, 208 feet wide), essentially free to move. Your speaker cone is supported around the perimeter and driven by the voice-coil support around the center. One's square, the other's circular, but that's a second-order effect.

There's nothing "speaker-like" about a bridge. There isn't a large, flat, relatively thin surface to couple the energy of the failing steel structure to the air.

And that "2-3 seconds of reverberations..." isn't part of the explosion, it's the response of the environment to the explosion. The explosion itself is the spike at the beginning. (Hint: How long does it take for C-4 to detonate?) Those reverberations will be there regardless of the source of the original driving impulse, whether it's from C-4 going off or from a steel strut bolted to the floor failing under-load.

And you, as a HiFi person, should appreciate the fact that the average person can't discern subtleties in really loud noises. (That's why bad musicians keep their amps cranked up.)
newton
all this comparing of floors to speakers is pretty lame.

a speakers can produce any sound. a floor makes a noise as it breaks. why bring speakers into this (non) argument at all?

the floors were not one big piece of continuous material that could have acted like a speaker diaphragm. they would break asymmetrically whether destroyed by debris from above, or explosions from below. they would sound more like an avalanche than an explosion, or series of explosions. the sound of thin floors hitting each other would be drowned out by the deafening 'clang' of heavy metal columns. concrete is would be inelastic in these collisions, but broken steel pieces could ring like bells once freed from connections.

maybe ella fitzgerald brought the towers down.

OneWhiteEye
QUOTE (Capracus+Oct 4 2007, 12:51 PM)
You're essentially correct.
http://www.usatoday.com/news/nation/2001/09/11/security.htm

Funny, it looks like I'm essentially correct, too, but I guess that doesn't count. Interesting. If it's the case I don't know what I'm talking about, it's quite understandable since all of this is so super-secret even a rear admiral can't know for sure.

What if I am wrong and am subscribing to a truther myth? After all, just because USA Today says there may have been air defense in DC doesn't make it true. I guess that would further serve to drive my point home - even Baghdad had anti-aircraft defense in its capital city. I ask again - what are the trillions going to if not simple, basic things like that?

Ah, but if you take the USA Today article at face value, what I said is likely true, save for the use of the term battery.

Who knows? Apparently you think you do, Grumpy. OK, I'll give you that one.

Well, Grumpy, while we're on the subject of myths, are you still peddling that nonsense about the floors collapsing many stories ahead of the visible front, thus causing the observed expulsions? You are the only person I've heard propose such a thing. This notion is a Grumpy myth, not worthy of serious consideration.

Name a source.
NEU-FONZE
Metamars:

As for US reactors I'm really no expert, but I do believe the US nuclear regulator, the NRC, operates much more at arms length than our Canadian counterpart, the CNSC. Ironically, oil man Bush looks all set to have the US "go nuclear" again, but what particular reactor design is favoured remains to be seen.

Anyway, back to NIST: I'm old enough to remember the old NBS. It really WAS a world class organization. It even had its own journal, (I used to read it!), and I certainly used to buy NBS analytical reference standards. But once politicians get their hands on something good they ALWAYS wreck it!
David B. Benson
QUOTE (newton+Oct 3 2007, 08:50 PM)
benson, it will only sound like a handclap if they hit perfectly parallel. a slight angle gives more of a crrrrrrassssssssshhhhhhhhh.

Over the entire 146 milliseconds it takes to crush one floor.

For everybody, the collapse picks up speed as it progresses. The first few impacted floors of WTC 1 might give distinguishable pop-pop-pop sort of sounds. But already by 1.6 seconds into the collapse, three or four floors are in some stage of being crushed.

However, perhaps only some of the floors produced explosive-type sounds.

And no, the floors in WTC 1 did not randomly strike one another. So long as the tilt was maintained each floor was struck first at the south edge and then progressively to the north.
David B. Benson
QUOTE (newton+Oct 3 2007, 08:50 PM)
explosions have a HUGE percussive spike, followed by ringing in the ears.

I'll certainly not take your word for it.

Pop pop pop is the sound of an exploding transformer. At least some of the witness accounts on Firehouse.com are clearly describing, both from the sound and the distinctive color, transformers exploding.

And no, I am rather convinced by now that the floors did not act as megawoofers:

(1) Could only do so one relatively intact floors. But these still had glass in the windows.

(2) Insufficient volume from the small displacements.

Much more interesting is attempting to determine what sound those momentary, ultra-high speed winds caused by 20 tonnes of air being rapidly expelled should produce and compare that with audio records.
David B. Benson
QUOTE (wcelliott+Oct 3 2007, 06:18 PM)
That would tend to result in more of a "freight train" type noise, i.e., concatenation of wide-band noise plus impulses.

I don't think the Giant Hands Clapping analogy would be quite applicable, as there was a lot of office furniture between the floors that would've crushed at different rates.  It would be like trying to clap with corn flakes between your hands.

Would anyone care to estimate how much energy was available for making those BANG!s?

Somebody might like to compare audio records from the collapses with freight train sounds.

Doesn't matter as at 25 m/s the entire collapse takes only 146 milliseconds. A very strong, fast Giant clapping hands.

The upper bound, all energy consumed per story, was about 348 megajoules from my computer program. No more than 12% of that was required to disconnect the office floor trusses from both the external and the internal truss seats. So far, all the rest is up for grabs.
Trippy
QUOTE (wcelliott+Oct 5 2007, 02:45 AM)
...making the floor a suspended diaphragm (four inches thick, 208 feet wide), essentially free to move... ...And that "2-3 seconds of reverberations..." isn't part of the explosion, it's the response of the environment to the explosion.  The explosion itself is the spike at the beginning.  (Hint: How long does it take for C-4 to detonate?)...

So, we have that something (essentially) flexible landed on something else, and that this process was asymetric, proceeding from south to north, the distance covered is (essentially) 208 feet, and the time it took to do this was 146 ms (provided by DBB).

Now, PETN has a detonation velocity of 8.28 (±0.1) mm/μs (J.J Dick et al, Journal of Applied Physics, July 1, 2000).

That means that it would take 525 ms for PETN to detonate along a 208 foot length.
Compare this to the 146 ms it took for the collapse to proceed along the same horizontal distance.

Still wonder why it sounded like a detonation?
David B. Benson
QUOTE (Trippy+Oct 4 2007, 11:08 AM)
So, we have that something (essentially) flexible landed on something else ...

The crushed block descending certainly was not very flexible, being entire stories each compressed into about half a meter vertically.

And it did not land on the trusses below, but rather crushed the ones below, to cause those to become the new crushing front.

Those minor corrections aside, I certainly like your most useful comparison!
Trippy
QUOTE (David B. Benson+Oct 5 2007, 06:30 AM)
The crushed block descending certainly was not very flexible, being entire stories each compressed into about half a meter vertically.

And it did not land on the trusses below, but rather crushed the ones below, to cause those to become the new crushing front.

Those minor corrections aside, I certainly like your most useful comparison!

You get my point though.

Mentally, I was picturing it as a piece of paper falling at an angle onto a floor.

Although perhaps a book falling at an angle onto a sheet of paper might be more accurate.

But, you're welcome.
David B. Benson
QUOTE (zoktoberfest+Oct 3 2007, 08:00 PM)
Physicists also know that there was not enough gravitational energy to pulverize massive concrete into fine dust, to cut massive steel beams into appropriate lengths to be loaded and removed on trucks, and to eject dust and steel beams hundreds of yards horizontally. Physicists know that if intense fire were present throughout the towers sufficient to cause steel to weaken and suddenly collapse, such fires would not have left unburned and unscorched hundreds of thousands of pieces of paper, which floated all over lower Manhattan.

Physicists have raised unanswered questions about the official explanation's neglect of the known laws of physics. Recently, Dr. Crockett Grabbe, a Caltech trained applied physicist at the University of Iowa, observed: "Applying two basic principles, conservation of energy and conservation of momentum, the government explanation quickly unravels. NIST conspicuously ignored these principles in their reports. NIST also ignored the observed twisting of the top 34 floors of the South Tower before it toppled down. This twisting clearly violates the conservation of both linear and angular momentum unless a large external force caused it. Where the massive amounts of energy came from that were needed to cause the complete collapse of the intact parts below for each tower, when their tops were in virtual free fall, is not answered in NIST's numerous volumes of study."

(1) If so, them is really stoopid, ignorant physicists. Even a chemist could work out a good first approximation for the concrete cominution; anybody with the slightest bit of sense expects the connections to fail, leaving the 'beams' the manufactured length; only high school physics suffices to explain the horizontal movement from a tower 415+ meters tall; the slightest bit of video viewing explains the paper as coming from other than fire floors. What a total, mindless idiot!

(2) As for Crockett Grabbe, he is out of his specialty. The "large exterior force" is called gravity and the asymmetric nature of the damage led to momentary torsional forces. The "massive amounts of energy" is called potential energy, which even a chemist used correctly. Good grief, Crockett Grabbe, have you lost your mind?

Finally, one who has. Lynn Margulis, in the past, did very important work in biology. She is out of her depth commenting on any aspect of the WTC events or the NIST report. But worse, far worse, are her recent comments within biology itself, even her specialty, evolutionary biology. It is clear that her mind is failing her. I am rather sad about it.
wcelliott
QUOTE
2) Insufficient volume from the small displacements.

The diaphragm of a bass drum when struck moves about a quarter-inch. Its diameter is a bit less than two feet, and the displacement varies from the maximum in the center to zero at the supported perimeter. The net displacement volume is surprisingly small, and the sound emitted is pretty loud.

I believe it was DBB who estimated that the compression of a structural column (core) due to the 30 floor overburden would be on the order of a foot or so, IIRC. (DBB - Please advise.) The floor area supported at the edges (core and perimeter) was 208feetx208feet minus the core-floor area (input welcome), and the force available for sudden displacement was the weight of 30 floors, so the last floor supported after the 30 floors "unloaded" from those same supports would, first-order, be available to accelerate the one remaining floor at ~30g's, if all columns unloaded themselves simultaneously/instantaneously. Granted that neither simultaneous/instantaneous/all columns unloading isn't what we'd expect, but it provides an upper limit that's easier to estimate, with the idea that if 1% of that applied to the real-world situation, that'd still be a lot of air displaced suddenly, and you can scale the displacement&energy to what comes from a struck bass drum and judge whether this is an insignificant acoustic effect.
David B. Benson
QUOTE (wcelliott+Oct 4 2007, 01:02 PM)
... judge whether this is an insignificant acoustic effect.

Floor 78 to the top of WTC 1: 33,200 tonnes
Next story down: 1530 tonnes
Elastic compression to the yield point of mild steel: 0.0002
Height of core columns: 438.3 for all 117 stories from the lowest sub-basement to the roof.

Maximum total compression before yielding: 0.877 meters
Estimated compression at floor 78: 33/117(0.877) = 0.247 meters maximum, might only be 1/3 of that: 0.08 meters

If the lower figure, about 3 inches. Even if the larger, the air is compressed to about 93% of its initial volume, right on the edge of breaking the glass in the windows.

I'll still assess this as insignificant compared to the rapidly descending upper block, which at the slowest (the start) voids the 20 tonnes of air from above floor 77 in about 1.2 seconds.

Edited to add: If this very first case actually broke windows via the sudden air compression then it is possible that the collapse of WTC 1 began with a bang. The NIST report does not mention such, AFAIK. Others may want to listen to the audio while playing some video to see if it does. Since nobody seems to have ever mentioned it, I currently doubt that such occurred.

Reedited to add: I forgot that the evidence strongly points towards a partial collapse of floor 77 before the prograssive collapse initiation. This makes it quite unlikly that sufficient overpressure to break glass could occur.
zoktoberfest
[removed]
David B. Benson
QUOTE (zoktoberfest+Oct 4 2007, 03:58 PM)
"(1) If so, them is really stoopid, ignorant physicists."

Smart enough to know who signs their paychecks.

[bafflegab]
by Kevin Ryan
[drivel deleted]

Wow! Are you completely confused.

Note than none of the people named in the deleted article are physicists.

And next time, kindly post a short quote and summary together with the link. So I'd don't have to delete all this nonsense which has been thoroughly debunked, several times over, on the three, count them three, threads devoted to this topic.
newton
QUOTE (David B. Benson+Oct 4 2007, 05:53 PM)
I'll certainly not take your word for it.

Pop pop pop is the sound of an exploding transformer. At least some of the witness accounts on Firehouse.com are clearly describing, both from the sound and the distinctive color, transformers exploding.

really?

and what causes these alleged popping transformers to pop off in a regular sequence?

david benson with his pants down.

transformers pop once.
David B. Benson
QUOTE (newton+Oct 4 2007, 04:31 PM)
transformers pop once.

Nope. Three phase transformers pop three times.

You should really take a little time to do some actual research before spouting off...
NEU-FONZE
Arthur:

Where is the evidence for NIST's "loss of insulation" theory when NIST admit in NCSTAR 1-2 that "NO VISIBLE INFORMATION COULD BE OBTAINED FOR THE EXTENT OF DAMAGE TO THE INTERIOR OF THE TOWERS"?

Where is the correlation between the alleged loss of insulation and the fires?

Do you have any comments on the level of damage to the core shown in Figure 9-31 of NCSTAR 1-2B?

Or a justification for assuming, as NIST does in NCSTAR 1-6A, that the debris impact damage to the SFRM was spread over an area FIVE FLOORS high and 45 meters wide?

Where is the estimate of how much impact energy was NOT used to damage WTC 2 but induce oscillations of the entire building?

Where is the evidence supporting the fire dynamic modeling?

Where is the evidence supporting the post-impact structural analyses?

wcelliott
QUOTE
and the changes in worldview that might be demanded of such an examination.

It would be especially traumatic for me to abandon all the physics I've ever been taught and have used, successfully, in my thirty years of engineering experience.

QUOTE (->
 QUOTE and the changes in worldview that might be demanded of such an examination.

It would be especially traumatic for me to abandon all the physics I've ever been taught and have used, successfully, in my thirty years of engineering experience.

Maximum total compression before yielding: 0.877 meters
Estimated compression at floor 78: 33/117(0.877) = 0.247 meters maximum, might only be 1/3 of that: 0.08 meters

If the lower figure, about 3 inches. Even if the larger, the air is compressed to about 93% of its initial volume, right on the edge of breaking the glass in the windows.

I think the key question (you may already have answered this) would be how much the top floor of the bottom block (top floor still intact) would recoil once the upper block's load was no longer being supported.

I can accept the 3 inches (or less), that's plenty for generating signficant displaced-air volume.

I'd also appreciate you taking a look at my simplistic calculation of how many g's that top floor would be subjected to once the overburden was "dropped". If it's anywhere near the 30g's, then we'd have a large area displaced rapidly.

It occurs to me that if that 30g figure is in the right ballpark, that'd probably launch the concrete of the floor straight up into the air at least a few feet. I wouldn't expect this to happen absolutely simultaneously, but locally to each column as its overburden was relieved.

For reference, even very loud sounds are associated with surprisingly small displacements. Normal conversation is associated with average air molecule displacements on the order of the diameter of an air molecule, IIRC.

I'm not saying that the 20tons of air exiting the floor in the time it took the first floor to fall 12 feet is insignificant, and I do understand the acceleration mechanism associated with the falling-piston as the two surfaces approach zero distance from each other. Another factor that would make it even louder would be the fact that the escaping air is metered through the gaps in the perimeter wall. (This also would exert significant aerodynamic forces on the perimeter columns, tending to splay them outward.) But what I'm trying to explore is the initial "BANG-BANG-BANG..." that was associated with the other tower's initial collapse which is what lead many of the CDiots to assume that they were hearing timed-explosions.

I think each of those BANGs was from structural failures coupled to large, flat surfaces that transformed the stored/released energy into loud noises. It should be noted that every surface in the tower was a large, flat surface that was connected to the structure, floors and perimeter walls, both. Explosions are impulses, and a sudden release of stored compression/tension (either way) coupled to a large, flat surface would generate an acoustic impulse that would be virtually impossible to differentiate between explosions.

The real distinction between the sound of an explosion and the sound of a sudden release of mechanical energy coupled to a large diaphragm would be in the frequency range that microphones and recorders don't record and speakers don't reproduce.
QUOTE (NEU-FONZE+Oct 4 2007, 07:46 PM)
Arthur:

Where is the evidence for NIST's "loss of insulation" theory when NIST admit in NCSTAR 1-2 that "NO VISIBLE INFORMATION COULD BE OBTAINED FOR THE EXTENT OF DAMAGE TO THE INTERIOR OF THE TOWERS"?

Its stated in the SAME paragraph.

From the Aircraft Imapact Analysis.

See NIST NCSTAR 1-6 for how they estimated the damage to the SFRM by the debris.

QUOTE
Where is the correlation between the alleged loss of insulation and the fires?

Not sure what you mean by correlation betweeen SFRM loss and the Fire but NCSTAR 1-5 details the fire reconstructions and discusses the impact of loss of SFRM.

Chapter 5 covers Heat Transfer Modeling including the impacts of SFRM loss.

Chapter 6 covers the Fire Simulations and Section 6.9 shows the temperature of the structural components over time which IS correlated to SFRM loss AND the thermal profile of the area of the building over time.

QUOTE (->
 QUOTE Where is the correlation between the alleged loss of insulation and the fires?

Not sure what you mean by correlation betweeen SFRM loss and the Fire but NCSTAR 1-5 details the fire reconstructions and discusses the impact of loss of SFRM.

Chapter 5 covers Heat Transfer Modeling including the impacts of SFRM loss.

Chapter 6 covers the Fire Simulations and Section 6.9 shows the temperature of the structural components over time which IS correlated to SFRM loss AND the thermal profile of the area of the building over time.

Do you have any comments on the level of damage to the core shown in Figure 9-31 of NCSTAR 1-2B?

As to the core damage in Base Case of WTC 2, Nothing strikes me as unexpected, particularly considering the other impact analysis that have been done showing MORE damage. What's your specific question?

QUOTE
Or a justification for assuming, as NIST does in NCSTAR 1-6A, that the debris impact damage to the SFRM was spread over an area FIVE FLOORS high and 45 meters wide?

The estimate of the size of the debris field was only used to come up with an AVERAGE energy of the debris they would use in the the simulated debris impact tests.

As usual NIST was used a fairly conservative value.

See NCSTAR 1-6A appendix C for details.

QUOTE (->
 QUOTE Or a justification for assuming, as NIST does in NCSTAR 1-6A, that the debris impact damage to the SFRM was spread over an area FIVE FLOORS high and 45 meters wide?

The estimate of the size of the debris field was only used to come up with an AVERAGE energy of the debris they would use in the the simulated debris impact tests.

As usual NIST was used a fairly conservative value.

See NCSTAR 1-6A appendix C for details.

Where is the estimate of how much impact energy was NOT used to damage WTC 2 but induce oscillations of the entire building?

Why do you think they are mutually exclusive? I certainly hope you aren't making the same mistake Kevin Ryan made?

QUOTE
Where is the evidence supporting the fire dynamic modeling?

This is covered in NIST 1-5 in general, but some specifics are mentioned is several places such as Sec 4.3.

QUOTE (->
 QUOTE Where is the evidence supporting the fire dynamic modeling?

This is covered in NIST 1-5 in general, but some specifics are mentioned is several places such as Sec 4.3.

Where is the evidence supporting the post-impact structural analyses?

NIST NCSTAR 1-6

Just telling.

Arthur

Trippy
QUOTE (David B. Benson+Oct 5 2007, 08:51 AM)
If the lower figure, about 3 inches. Even if the larger, the air is compressed to about 93% of its initial volume, right on the edge of breaking the glass in the windows.

That's one thing I never quite got.

Why does the yeild strength of the windows neccesarily have to limit the over pressure.

It's a shockwave, and it's being driven by the collapse of the floors. Even sans windows, there would still be an over pressure - it would be local, and unsustained, but it would be an over pressure none the less.
newton

benson, i know YOU can't watch videos, but for everyone else.

sounds like one explosion to me. three in slow mo.

however, you need a power surge to blow a transformer.
why would there be a SERIES of equally spaced in time power surges that progress down the tower as it collapses.

REACH for those pants.
An interesting paper on Bombs, sound and shock waves.

http://www.makeitlouder.com/document_bombs...estimation.html

It is the SHOCK wave that is the SIGNATURE of a High Explosive.

They should be EVIDENT on any decent recording because they are DIFFERENT than SOUND WAVES (and arrive much quicker) giving the characteristic CRACK sound we associate with real explosives.

I believe I've listened to all the publicly released recordings made that day and AFAIK there is not one CRACK in the bunch.

You can, on the other hand, hear it CLEARLY in the Hudson Building demolition.

BUT

There ARE quite a few demolitions where you can't here the CRACK.

Most likely due to the location of the HE in relation to the microphones/quality of the recordings etc.

SO, absense of CRACK does not mean there wasn't HE.

But, absense of CRACK means you can't tell if it was HE or just Explosive sounds of the building crashing down.

Arthur
wcelliott
QUOTE
however, you need a power surge to blow a transformer.

BS.

They blow for any number of reasons, but in this case, all it takes is a "crowbar short" caused by a hot wire touching a ground, like what you'd expect when a building collapses during a fire.
Alan (ex elevator man)
QUOTE (wcelliott+Oct 4 2007, 11:22 PM)
They blow for any number of reasons, but in this case, all it takes is a "crowbar short" caused by a hot wire touching a ground, like what you'd expect when a building collapses during a fire.

I agree, and starting at collapse initiation, the dead shorts could keep going all the way back to each one's source, including the main supply from Con-Ed under building 7.
NEU-FONZE
Arthur:

Thanks for the response, but you really have not answered my main question.

I was mostly asking for EVIDENCE.

Modeling is not evidence.

It appears to me that NIST has very little EVIDENCE to support any of its analyses.
For example, estimates of the damage to the insulation are arrived at by an ad hoc assumption tagged onto the aircraft impact MODEL - a model that does NOT include thermal insulation (See NCSTAR 1-6)!

A model is a model is a model. Oh, and by the way, Perdue's MODEL gives different results to NIST's MODEL.

EVIDENCE is based on physical observations... not virtual reality MODELS!

There is NO EVIDENCE for the state of the thermal insulation in the towers, as admitted by NIST in NCSTAR 1-2.

There is NO EVIDENCE to support the post-impact structural analysis.

There is NO EVIDENCE to support the fire dynamic modeling.

All NIST has to offer are models piled on models.

You see it goes like this:

NIST MODEL the jet fuel dispersion.

NIST model the distribution of the aircraft debris.

NIST model the spread of the fires.

NIST guess at the extent of the damage to the insulation.

NIST model the structural damage.

Any uncertainty in the jet fuel dispersion should be carried over into the modeling of the spread of the fires. Was it?

Any uncertainty in the distribution of the aircraft debris should be carried over into the structural damage model. Was it?

NIST guesstimate the damage to the insulation based on the way one of its models predicts the aircraft moved the furniture and the partitions around! What is the basis for the assumption that moving furniture and partitions damaged the insulation?

Arthur, all of these uncertainties must be added to the uncertainties in the predictions of the weakening of the structure.

Show me where NIST estimate the total uncertainty of its final conclusion and where NIST provide proof that it has considered all of the variables that could influence the model.

Arthur, simply quoting chapter and verse of the NISTIAN CREED does not make any of it true.

Grumpy
NEU-FONZE

Are you of the opinion that all of the 200+ scientists working with NIST are not as competent as you are???

Do you have any evidence that they DID NOT do as competent a job as it was possible to do, given the restrictions on the evidence they were working under???

Or do you just like to bitch??? Just asking.

Grumpy
QUOTE (NEU-FONZE+Oct 5 2007, 08:22 AM)
Arthur:

Thanks for the response, but you really have not answered my main question.

I was mostly asking for EVIDENCE.

Neu, once again you are acting SILLY.

Did that smoking pile of rubble that burned for 3 months not explain why NIST HAD to use MODELING?

Which is why they at the end they discuss PROBABLE causes.

We are all aware of the limitations of modeling.

Still their report remains the BEST overall description of what happened to the towers.

I'm sure that various aspects of the models could be refined further, but IMHO it would, in respect to the demise of the towers, rapidly reach a point of diminishing returns.

Arthur
Update on the Browns.

(Their standoff with the feds based on their belief that the Income Tax was illegal had been discussed here previously)

Arthur
David B. Benson
QUOTE (newton+Oct 4 2007, 09:15 PM)
... sounds like one explosion to me. three in slow mo.

About 15--17 years ago the nearby big step-down transformer, stepping down from transmission voltage to distribution voltage gave up the ghost.

This supplied about 1/2 the town, say 15--17 thousand people and their businesses.

It was a most spectacular fireworks shown, which I could watch from by porch.

I have ample opportunity to talk to the local power professors (Best in the West, fourth in the U.S., despite their being only 4--5 of them.)

Some transformers might blow as a single sound, but if you actually read accounts of the larger transformers blowing, you'll find plenty of examples of

pop-pop-pop as each phase goes, together with the characteristic white then orange of fairly modern transformer designs. This is exactly what was heard and seen in the witness accounts, although I disremember in connection with which tower.
David B. Benson
QUOTE (Alan (ex elevator man)+Oct 4 2007, 10:40 PM)
... the dead shorts could keep going all the way back to each one's source, including the main supply from Con-Ed under building 7.

Yes, but there are supposed to be competent circuit breakers at various points, especially the output side of the ConEd station.

But seeing how we are discussing NYC and especially ConEd, one might question the competence...
David B. Benson
QUOTE (Trippy+Oct 4 2007, 08:42 PM)
Why does the yeild[sic] strength of the windows neccesarily[sic] have to limit the over pressure.

It doesn't. All I was noting is that compressing the air to about 93% of its former volume isothermally raised the pressure to enough to possible break the quarter-inch plate glass windows.

If the windows did not break, little sound would be heard outside.

Edited to add: I forgot that many of the windows are this level of WTC 1 were already broken, if not by the impact, then by the resulting fires.
David B. Benson
QUOTE (wcelliott+Oct 4 2007, 04:48 PM)
I'd also appreciate you taking a look at my simplistic calculation of how many g's that top floor would be subjected to once the overburden was "dropped".  If it's anywhere near the 30g's, then we'd have a large area displaced rapidly.

...  Another factor that would make it even louder would be the fact that the escaping air is metered through the gaps in the perimeter wall.

(This also would exert significant aerodynamic forces on the perimeter columns, tending to splay them outward.)

But what I'm trying to explore is the initial "BANG-BANG-BANG..." that was associated with the other tower's initial collapse which is what lead many of the CDiots to assume that they were hearing timed-explosions.

This can be treated as an extended mass-spring system. Close enough, the effective mass is given by

M + 0.35 m

where M is the mass of the top block and m is the mass of the bottom block. Doing so, you'll find that the period is about 0.6 seconds, so the initial displacement upwards takes about (1/4)0.6 = 0.15 seconds, this for WTC 1.

Escaping air: yes, this is treated with some care in Bazant/Le/Greening/Benson, in an attempt to see just how fast the air had to move. The conclusion is that towards the end of crush-down some of the air is moving at Mach 1.0, necessary but not sufficient to produce a supersonic boom.

I would like to see some decent estimates for this push on the exterior wall panels.

?? By other tower do you mean the south tower, WTC 2. I do not recall any witness reports of the sort you mention for WTC 2. But maybe it is on some video or other...
NEU-FONZE
Grumpy and Arthur:

A couple more points for you to ponder:

NIST's modeling starts with the aircraft impacts and the fuel dispersion, correct?

Well, according to NIST, (See NCSTAR 1-2B):

"The physics of fuel impact and dispersion ... is complex and no appropriate validation data could be found. .... No single analysis technique is currently available that can analyze ... fuel dispersion without significant uncertainties."

So how does NIST arrive at a fuel distribution that is anything but a wild guess?

If step one of the process of deciding how and why the towers fell is based on guess work, how can we have any faith in the final conclusion?

So tell me, do you really think moving the furniture around removed all that insulation? And how many floors do you believe were affected?

As for the NIST Report being the best guess we have, well this may be true, but that does not make the Report true.
David B. Benson
QUOTE (NEU-FONZE+Oct 5 2007, 11:19 AM)
As for the NIST Report being the best guess we have, well this may be true, but that does not make the Report true.

I agree. It is only an approximation to the actual events.

However, the Purdue study tends to validate NIST's impact analysis as the conclusions are similar.

But more important, I think, it is clear from the videos that both towers ability to stand, resisting gravity, decayed over time. The innovative approach to video analysis first done by poster einsteen and being carried forward by poster OneWhiteEye certainly makes evident that the north tower was actually beginning to collapse several seconds before the exterior wall buckled. This, to me, helps to confirm that NIST's sequence of events given in NCSTAR1--6 and NCSTAR1--6D is more-or-less a good summation of this decay.

By the way, if you are looking for criticism of the study, consider what NIST authors have to say in the Executive Summary section of NCSTAR1--6.
Grumpy
NEU-FONZE

QUOTE
"...significant uncertainties."

...is not the same thing as...

QUOTE (->
 QUOTE "...significant uncertainties."

...is not the same thing as...

...a wild guess

...and you should know that!

And not only was debris from furniture involved, what about all the little shards of aircraft, fuel at high pressures and speeds and the pieces of those rapidly rotating turbofan blades all spraying out like a 125 ton shotgun blast, are you saying this WOULD NOT strip fireproofing foam with the density of Styrofoam??? That's not very reasonable to me.

No, NIST is not perfect. Yes, it would be better if we had more solid evidence, but we don't. And I do not think you could have done any better than they did, if you disagree, publish.

And it would bother me a lot to have these CTer nutcases using my statements about NIST this..., and NIST that...to support their lamebrain theories, why does it not bother you??? I mean, perchlorate mixed into the fireproofing??? I've had your words quoted to me, chapter and verse, by guys saying"See, NIST isn't true, Dr, Greening says so..." Is that what you want???

Grumpy
David B. Benson
QUOTE (Grumpy+Oct 5 2007, 02:46 PM)
... NIST isn't true ...

At which point you need to (once again) explain the contingent nature of all of science.

The technique which (sometimes) works for me is to remind the reader that in matters physical, there is only one vote: Nature's. All we can hope to do is develop good approximations, attempting to devise better ones when (and if) more evidence comes along.

Luck.
Trippy
QUOTE (David B. Benson+Oct 6 2007, 06:41 AM)
But more important, I think, it is clear from the videos that both towers ability to stand, resisting gravity, decayed over time. The innovative approach to video analysis first done by poster einsteen and being carried forward by poster OneWhiteEye certainly makes evident that the north tower was actually beginning to collapse several seconds before the exterior wall buckled. This, to me, helps to confirm that NIST's sequence of events given in NCSTAR1--6 and NCSTAR1--6D is more-or-less a good summation of this decay.

Minor point here, that I've pointed out before.

I have a feeling it was mentioned in the doco "The man who predicted 9/11" which, inspite of the title, was a doco examining the actions of Rick Rescorla - he was a brit who was a boy during WWII, and was a platoon commander (might be a little higher) during Veitnam, he was in charge of security for some big bank that was in the second tower to be hit (I forget the name of it) the bank had something like 2,700 employees of somethign like 30 floors of the tower, the top floors of which were just below the impact zone. Because of his training, out of the 2,700 odd employees under his supervision, all bar three or four of them survived (and he kept going back to help the fire service, he himself did not survive 9/11).

Anyway, I bring this up because I'm fairly sure that it's mentioned in the doco, as well as many of the interviews that I linked to (specifically, the one with the guy that was in charge of setting up the OEM center) that for both towers, they were getting reports from the police helicopters that the towers were looking like they were definitely coming down (or in the process of coming down?) for as much as 10 to 15 minutes before the collapses, it's just that with the inadequite communications equipment available (cell phones were out and there was too much interference between the cores and the lobby, let alone outside of the towers) the information wasn't getting where it was needed.
Trippy
QUOTE (NEU-FONZE+Oct 6 2007, 06:19 AM)
NIST's modeling starts with the aircraft impacts and the fuel dispersion, correct?

Well, according to NIST, (See NCSTAR 1-2B):

"The physics of fuel impact and dispersion ... is complex and no appropriate validation data could be found. .... No single analysis technique is currently available that can analyze ... fuel dispersion without significant uncertainties."

So how does NIST arrive at a fuel distribution that is anything but a wild guess?

Generally it's called 'Statistical analysis'

You examine all of the available models.
You use the available models to produce a variety of distributions.

Many of the distributions will be wildly different, but they will all have common features.

Doing this you can say that you are "95% confident that the fuel distribution looked like this."
David B. Benson
How tall was each story in WTC 1?

In order to properly treat the very gradual beginning of the collapse, before buckling, I'll need quite an accurate value. And there is a problem. Greening states that WTC 1 was 417 meters tall, that's from the ground up. From floor 1 to the roofline, a nominal floor 112, is 11 floors for an average height of each story of

417/111 = 3.7567 meters.

But all the readings claim 12 feet = 3.6576 meters.

So were the extra 0.099 meters per average story? That's about 3.9 inches. Were all the stories actually 12' 3.9" vertically from floor to floor or was the excess over 12 feet actually because the pairs of mechanical floors were more than 24 feet tall?

3.6576 x 111 = 405.9936 meters,

so about 11 meters are yet to be properly accounted for. There were four pairs of mechanical floors, giving an extra about 2.7516 meters for each pair. This is certainly a possible design, but I don't know.

Of course, another possibility is that floor 1, the concourse level, was actually somewhat above the nominal ground level, but seems unlikely to have been 11 meters above!
David B. Benson
QUOTE (Trippy+Oct 5 2007, 04:58 PM)
... the second tower to be hit (I forget the name of it) ...

... that for both towers, they were getting reports from the police helicopters that the towers were looking like they were definitely coming down (or in the process of coming down?) for as much as 10 to 15 minutes before the collapses ...

The south tower, WTC 2.

For the north tower, WTC 1, the police helicopter provided warning about 20 minutes before the collapse that they could detect signs of eminent collapse. (I've seen nothing about that regarding WTC 2 as far as I recall...)
OneWhiteEye
QUOTE (David B. Benson+Oct 6 2007, 12:05 AM)
How tall was each story in WTC 1?

Fascinating.

Edit: just amazing that fundamentals like floor height are yet TBD. Carry on, I'll follow very carefully the developments in that as you post them. Pixels are a really great domain to work in at this time.
Trippy
QUOTE (David B. Benson+Oct 6 2007, 12:13 PM)
The south tower, WTC 2.

For the north tower, WTC 1, the police helicopter provided warning about 20 minutes before the collapse that they could detect signs of eminent collapse. (I've seen nothing about that regarding WTC 2 as far as I recall...)

I've seen somethign similar for WTC2, but it was mor elike 6 minutes. wish I could remember more specifics.
David B. Benson
QUOTE (OneWhiteEye+Oct 5 2007, 05:23 PM)
Fascinating.

Well, I'd call it disturbing.

If it is possible to just use the horizontal distance across a wall, that might work, assuming pixels are square. Pixels are square, aren't they?
Trippy
I can think of two possible explanations.

The first one that springs to mind is the thickness of the floor pans (I know it's been stated how thick they were before, but my recollection of anything I read before 7am isn't the best most days) - as in are we talking 12 feet between the base of one floor pan, and the base of the next one, or 12 feet between the top of one floor pan, and the base of the next one.

Another posibility is ceiling space.

It makes sense (to me at least anyway) for there to be a few inches of space between the ceiling panels and the base of the next floor pan, gotta have some space for cabling and such after all.

But if somebody has misunderstood the space between the floor and the ceiling panels as being the space between the space between the top of one floor pan, and the bottom of the next one...
OneWhiteEye
QUOTE (David B. Benson+Oct 6 2007, 12:30 AM)
Well, I'd call it disturbing.

If it is possible to just use the horizontal distance across a wall, that might work, assuming pixels are square. Pixels are square, aren't they?

OK, disturbing it is.

No, pixels aren't always square. I can't say whether or not they generally aren't square, but I think it's the case. But 'pixel' as used loosely can mean different things. Generally pixels refer to the color information encoded in an array which is then mapped to a rectangular region by whatever display device is in use - monitor, printer, whatever. Ideally, the encoded info is represented correctly but I'm sure you've viewed or printed something that seemed to have the wrong aspect ratio.

There are DDBs (not to be confused with DBB here) and DIBs and it's too complicated to review in a paragraph, so I'm going to say the best answer to your question is: yes, they are.

Except the proportions they're representing may be altered. Resampling the frames to a different size (as I think happened with the WTC 24 video off the internet) makes the question moot. That's why you must always measure to scale horizontal and vertical independently, unless they happen to agree.

But even if they agree, the projection ends up not being rectilinear, so if you must measure across broad regions you really need to verify you can use the same number everywhere. Generally is not so. The geometry is conic section; the basis vectors are rarely orthogonal and parallel is just... a curiosity.
OneWhiteEye
This may help illustrate the effects of optics and resizing on the appearance and metrics of objects projected onto the image plane. I've produced a pair of images with a raytracer, the first with characteristics of what might be considered an average lens, the second like that of a wide angle panoramic lens. Both images are identical except for field of view and depict the view of a checkerboard plane with the same camera location and target point.

Pardons if some of this is painfully obvious.

Normal Lens
http://i21.tinypic.com/oiyiat.jpg

Panoramic Lens
http://i20.tinypic.com/2cwsgv4.jpg

In the first, lines appear straight but vertical lines are not parallel. The checkerboard, of course, consists of perfectly true squares but there isn't one that measures that way anywhere in the scene. The very center line cutting the picture vertically in the middle is a true straight, vertical line.

The second is a gross exaggeration but the effects displayed are always present to some degree, even if not measurable. It depends on the lens and distance from the camera. Zoom is an associated consideration but really is subsumed under distance, as more distant regions of small angle naturally project flatter whether they're zoomed or not (but the region does occupy more pixels when zoomed). The horizontal lines are complete smack in this wide-angle view, but that center vertical line is still good! I can fix that. Let me slide the camera over to the side just a little bit:

http://i21.tinypic.com/35bxwnm.jpg

Now there's not a straight line anywhere anymore. Bet you didn't notice that I also shrunk the horizontal dimension by 12% at the same time, something similar to what might have happened with the video I'm studying. The video is OK as a testbed because it's good, but has some flaws that can flesh out real world problems typically present in any image whether obvious to the eye or not.

These considerations are the ones that determine local or even global scaling. The pixel is faithful, but is a ways off from R3 space in meters.

PS check the difference in appearance between the thumbnails on this page and the full size at the links. This is an example of a 'clean' resize.
OneWhiteEye
By the way, it's obvious the images above have limited smear and no motion blur or noise, but did I mention that the camera's vertical orientation is perfect and there are no lens aberrations?

And the one vertical line in the center of the image I called 'true vertical' is actually true horizontal!
QUOTE (David B. Benson+Oct 5 2007, 08:30 PM)
Well, I'd call it disturbing.

If it is possible to just use the horizontal distance across a wall, that might work, assuming pixels are square. Pixels are square, aren't they?

It might be disturbing TO YOU, but that's ONLY because of YOUR METHOD of modeling the collapse requires this data.

It is NOT at ALL an issue to the NIST study since they modeled based on ACTUAL sizes of the columns for the floors involved.

Arthurd
Alan (ex elevator man)
As for floor height... my experience has been that all floors are typical except the lobby floors. Mechanical floors don't have to be taller because all the big equipment is dropped into place by crane before the next floor is built. WTC's mechanical floors could be different, I dunno. The two tallest buildings here in Houston I helped build the elevators on... one had typical floor height of 13-ft with a tall lobby on the first floor and a tall lobby on the 60th floor. Six high-speed elevators went from 1st to 60 without any stops in between. From there, people could go up or down in 2 banks of smaller elevators. That building was 75-floors. The other building was 72-floors, but only a few feet shorter. It's typical floors were 13'-1"... an inch taller. BUT, that building had 3 lobby floors. It had 2 banks or double-decker elevators that were express cars to the lobbies. One had folks getting on the same elevator at basement A and 1st floor, going straight to 34 and 35th level. It had 5 elevators in that bank. Then it had 6 cars that took passengers from basement A and 1st floor straight to 58 and 59th levels. So basically it had more taller lobby floors than the 75-floor building, so it was almost as tall with fewer floors. Neither of those two buildings had taller mechanical floors.
Just to be clear, as far as mechanical... the elevators had a "machine room" above each bank of elevators that are two levels above their terminal landing (top floor served), but again... those machines would've been dropped by crane on the beams we set going across the hatch... THEN the ironworkers could continue with the next floor... so it didn't have to be a taller floor.
One more thing... floors are "typical" as far as height because... before the plans are final, they can go a little higher or a little lower depending on how the leasing looks, because they are all the same and easy to 'plug in' or 'unplug'... a few.
*edited for one mispelled word... though there are probably more
Alan (ex elevator man)
Chase Tower (was Texas Commerce Tower when we built it). Notice 15-floors down from the top it is a taller floor (60th floor lobby)... windows are taller.

More pictures, including under construction at this link:
JP Morgan Chase Tower
===============================
Wells Fargo Tower (called Allied Bank Building when we built it.

That's 50-floor One Shell Plaza closer to the camera and 55-floor First Interstate Plaza on the other side.
Wells Fargo Plaza
Trippy
were the sky lobbies any taller then an average floor?
shagster
Video of a substation arcing. Watch what happens near the end. The white cloud is probably vaporized transformer oil.

http://s134.photobucket.com/albums/q91/sha...rrent=trans.flv

OneWhiteEye
Nice information posted recently.

More pictures. Image 1 is frame 800 of the video I've been looking at. Image 2 is a 3D rendering I've just done in trying to match the field of view and camera location. There are some other means to determine this info but this way is more entertaining than most.

http://i21.tinypic.com/97s7y9.jpg

http://i23.tinypic.com/11jvvjs.jpg

#declare camera_height=250;
#declare camera_horiz_distance=3700;
#declare camera_lateral_offset=150;
#declare camera_look_at_floor=103.7;

It's not quite there yet, but close. In order to get a better fit to the real picture, I did a 12% vertical stretch and recropped to the frame size - much closer. The wall texture needs some work and the antenna is a featureless cylinder. More detail and refinement coming.

I'd like to put a 3D animation together. Not a simulation, not some graphic artist's concept cartoon, but a scale rendering based on precisely extracted video motion. A 3D transcription of the actual event. It could be rendered with any camera path/view and any frame rate.

Some useful links for field of view, lenses and such:

http://en.wikipedia.org/wiki/Angle_of_view

http://photo.net/learn/fov/

http://www.tawbaware.com/maxlyons/calc.htm
QUOTE (Trippy+Oct 6 2007, 03:40 AM)
were the sky lobbies any taller then an average floor?

The first set of STANDARD external columns start on the 9th floor at an elevation of 55'11".

Standard external columns were 36' tall, 10' wide and spanned 3 floors.

This gives a STANDARD floor height of 12 ft.

Note the top of the floors are in line with the top of the spandrels, the top floor of a 36' column is 3'10" below the column splice.

See NIST NCSTAR 1-1A fig 5-1 and 5-2

The only major difference in the exterior columns occured at the Mechanical floors where the staggering of external columns ended and then restarted.

You can see that in this photo:

http://i117.photobucket.com/albums/o72/ard...ruction1505.jpg

Finally the very TOP of the towers were somewhat different, including the roofing area, though NIST obviusly used the proper dimensions in their model I haven't seen anything in their documentation about the roof and the top mechanical floors.

But building heights are to the TOP of that roof line, so NO, you can't divide by the number of floors and expect to come up with the height of one floor.

Note, NIST has released their DB of WTC structural members, so, given the material available in the NIST reports along with the structural DB, if anyone really cared to, one could build their very own version of the towers. There is NOTHING of any significance unknown about the materials, design or structure of the WTC towers.

Arthur
David B. Benson
QUOTE (adoucette+Oct 6 2007, 06:38 AM)
I haven't seen anything in their documentation about the roof and the top mechanical floors.

But building heights are to the TOP of that roof line, so NO, you can't divide by the number of floors and expect to come up with the height of one floor.

There is NOTHING of any significance unknown about the materials, design or structure of the WTC towers.

That's the only part which is of concern. Need it quite accurately to convert pixels to meters.

The roof isn't thick enough to matter. So yes, dividing by the number of floors gives the average floor height.

For NIST, yes. For me no.

But I'll go back to you comment regarding floor 9 later to try a different calculation.
David B. Benson
QUOTE (adoucette+Oct 6 2007, 06:38 AM)
The first set of STANDARD external columns start on the 9th floor at an elevation of 55'11".

[Compl;etely rewritten]

No, that is the height of the column trees.

From Figure 3--6, page 37 (71 ordinal), NCSTAR1--2A, floor 9 was at reference elevation 414 feet.

(Now all I have to do is find the reference elevation for floor 1.)
David B. Benson
Page 35 of the same document gives the reference elevations for floors 3 and 2. That works and the mystery of some of the additional 11 meters is explained.

As Alan suggested, some of this extra occurred via taller lobby floors.

Anyway, looking carefully through these pages strongly hints at the top part all being exactly 12 feet high, all the way to the roofline. (Although the roof might have been a few inches thicker, that won't matter.)

All of this is from an Elevator Layout sheet detail, drawn in 1963.

The reference elevation for the basement floor is 242'
The next floor up is 11' tall to 253'
The next floor up is 11' tall to 264'
The next floor up is 10' tall to 274'
The next floor up is 10' tall to 284'
The next floor up is 10' tall to 294
The next floor up is 16' tall, at the concourse elevation at 310' which is Floor 1.

Turns out the skylobbies were 14' tall and the Mechanical floors next to skylobbies were 26' tall. The first and last Mechanical floors were only 24' tall.

The towers weren't identical, but for Tower A, the Mech floor on 7 starts at an Elevation of 396.5'

This is followed by the first floor of bank 1 (floor 9) at an elevation of 420.5' (there is no skylobby)

Bank 1 consists of 32 floors at 12' per floor (384') ending at the second mechanical floor (26') and the first of 14' skylobbies.

Bank 2 starts at an elevation of 844.5 and has 31 floors at 12' per floor (372') ending with the third mechanical floor (26') and the second 14' skylobby.

Bank 3 starts at an elevation of 1256.5 and has 29 floors at 12' per floor (348') ending at an elevation of 1603.5'

Now we have either the observation deck or the Restauraunt, but in any case the next two floors take up 19'

This is followed by the 4th and last Mechanical floor, also 24' tall.

This is capped by the roof, but surrounded by a 10'6'' parapet. at an elevation of 1656'6".

http://i117.photobucket.com/albums/o72/ard...t-page146rb.png

Arthur
Trippy
I think that explains the missing height...

heh.
David B. Benson
QUOTE (adoucette+Oct 6 2007, 01:41 PM)
All of this is from an Elevator Layout sheet detailing from 1963.

The reference elevation for the basement floor is 242'
The next floor up is 11' tall to 253'
The next floor up is 11' tall to 264'
The next floor up is 10' tall to 274'
The next floor up is 10' tall to 284'
The next floor up is 10' tall to 294
The next floor up is 16' tall, at the concourse elevation at 310' which is Floor 1.

Turns out the skylobbies were 14' tall and the Mechanical floors were 26' tall.

The towers weren't identical, but for Tower A, the Mech floor on 7 starts at an Elevation of 396.5'

This is followed by the first floor of bank 1 (floor 9) at an elevation of 420.5' (there is no skylobby)

Bank 1 consists of 32 floors at 12' per floor (384') ending at the second 24 ft mechanical floor and the first of 14' skylobbies.

Bank 2 starts at an elevation of 844.5 and has 31 floors at 12' per floor (372') ending with the third 24' mechanical floor and the second 14' skylobby.

Bank 3 starts at an elevation of 1256.5 and has 29 floors at 12' per floor (348') ending at an elevation of 1603.5'

Now we have either the observation deck or the Restauraunt, but in any case the next two floors take up 19'

This is followed by the 4th and last Mechanical floor, also 24' tall.

This is capped by the roof, but surrounded by a 10'6'' parapet. at an elevation of 1656'6".

Arthur

Wow!

Just what I (and others) need! Thank you!

OneWhiteEye
QUOTE (adoucette+Oct 6 2007, 08:41 PM)
Sorry, poor use of the word 'elevation' on my part.

... at an elevation of 1656'6".

Arthur

Wow, that is a lot of detail. Thanks very much for that.

Arthur
David B. Benson
QUOTE (adoucette+Oct 6 2007, 01:41 PM)
Now we have either the observation deck or the Restaurant, but in any case the next two floors take up 19'

This is followed by the 4th and last Mechanical floor, also 24' tall.

This is capped by the roof, but surrounded by a 10'6'' parapet.  at an elevation of 1656'6".

For WTC 1, restaurant was story 107. Next pair of stories up are the upper mechanical floors. So are you saying that story 107 was 19 feet high?

Above 108--109, according to Appendix G of NCSTAR1--2A, was 110, TV/Storage. Above that was the PH Roof (core only) level.

Taking elevation 294 as the ground level (floor of the concourse), 1656.5 - 294 = 1362.5 feet, 5.5 feet shy of the widely advertised 1368 feet. Edited to add: Oh, perhaps the nominal ground level is 5.5 feet below the concourse floor level. From the plan it seems this might be so.

I do appreciate having the link, but unfortunately I don't know of any means to magnify it far enough to read it myself, so I can't resolve this discrepancy in the documentation regarding story 110 and the PH Roof levels.
Yes

The side views for the Observation deck and the Restaurant are not the same though.

The Observatation deck version is 19' tall, but the Restaurant version is only 15' tall but it appears to sit on a 4' raised floor. Thus they both take up the same net distance (19') and the Mech floor starts at the same elevation for both, 1622.5'

Interesting the elevator for both comes out on the raised floor level.

Too bad you can't view the PNG file, it allows you to expand it for viewing.

Can you not install a decent file viewer?

If not, what file formats can you view?

Arthur
shagster
Here's a portion of the master plan. The drawing is dated Dec 16, 1963.

http://i134.photobucket.com/albums/q91/sha.../elevation1.jpg

http://i134.photobucket.com/albums/q91/sha.../elevation0.jpg

David B. Benson
QUOTE (adoucette+Oct 6 2007, 03:32 PM)
Too bad you can't view the PNG file, it allows you to expand it for viewing.

I can and I can expand it. However, I cannot expand it enough to read the various numbers.

The only format I know how to expand indefinitely is .ps files. The reader, ghostview, will also handle some .pdf files. When it works properly, then those can be expanded as well.

My current concern is that, at the very top, the Elevator file and Appendix G of NCSTAR1--2A appear to be in fairly serious disagreement. As I read the Elevator file, there is no story 110. Right after the upper mechanical floor is the PH Roof level. (By the way, that is not a parapet, but the roof line which runs flat across the entire top.)
shagster
Another portion of the master plan drawing showing the top section.

http://i134.photobucket.com/albums/q91/sha.../elevation2.jpg

OneWhiteEye
That's great stuff, thank you both. The PNG file is 626x800, I couldn't make out the numbers either. The top and bottom corners, though, very legible.

Edit: shagster I'm encountering some of your work as I read the older threads, really nice stuff. I'm at the point where you post the curves for ejection distances. OMG. Brilliant.
David B. Benson
QUOTE (shagster+Oct 6 2007, 03:48 PM)
Another portion of the master plan drawing showing the top section.

Thanks!

Note that the PH Roof level is marked as story 106 and it is clear that on that plan there is no TV/Storage story above the upper mechanical floors and below the PH Roof.

So I am guessing that something changed between this planning stage and the final as-built plans.

Anyway, from the earlier expansion showing the near-ground levels, it does appear that the concourse is about 10 feet above the nominal ground level.
shagster
QUOTE (David B. Benson+Oct 6 2007, 10:56 PM)
Thanks!

Note that the PH Roof level is marked as story 106 and it is clear that on that plan there is no TV/Storage story above the upper mechanical floors and below the PH Roof.

So I am guessing that something changed between this planning stage and the final as-built plans.

That's why I mentioned that it was from Dec 1963.

I'm not sure when the decision was made to include the main antenna tower and radio equipment room. The main antenna tower wasn't installed until about 1978. One of the documentaries mentioned that residents in the area were concerned about the towers blocking their TV reception. The politicians and construction people said that they would insure that everyone would receive their TV signals ok. That was before construction of the towers was finished.

Incidentally, you can see some gaffs in movies that show the towers as they were supposed to look in the early 70s. For example, the documentary on the rock star Meatloaf shows stock footage of the WTC towers with the antenna on WTC1. This is supposed to be in the early 70s when the antenna tower wasn't there yet.
David B. Benson
From NCSTAR1--2A, page 35:

floor 2 at elevation 329.25, so if the concourse was still at elevation 310, floor 1 was 19.25 feet high.
floor 3 at elevation 350.25, so the lobby was 21 feet high.

Then adding up all the excess (deficit) heights of stories which had excess (deficit) heights, the excess was 25.75 up to the roofline.

25.75 + 111 x 12 = 25.75 + 1332 = 1357.75

leaving 10.25 feet for the distance of the concourse floor above the nominal ground level. This agrees with the plan within 3 inches, which is certainly good enough.

Ok, the part of greatest concern was above story 78, the upper skylobby. Above there all stories are 12 feet high until story 107, which was 19 feet high. Above that there are 24 feet of ventilators (no windows) on the upper mechanical floors. Above that was story 110, which I have taken to be 12 feet high (and had no windows?) Above that is the slightly inward sloping parapet up to the roof, taken as 10.5 feet vertically.

Now it would be nice to see a good shot of stories 106 up to the top to check that I have the window/ventilator layout down pat.
shagster
QUOTE (David B. Benson+Oct 5 2007, 06:41 PM)

But more important, I think, it is clear from the videos that both towers ability to stand, resisting gravity, decayed over time. The innovative approach to video analysis first done by poster einsteen and being carried forward by poster OneWhiteEye certainly makes evident that the north tower was actually beginning to collapse several seconds before the exterior wall buckled. This, to me, helps to confirm that NIST's sequence of events given in NCSTAR1--6 and NCSTAR1--6D is more-or-less a good summation of this decay.

I mentioned a while back that someone was trapped in WTC1 just above the impact level and on the phone with his father when the collapse started. The last thing he stated to his father was that parts of the ceiling were starting to fall down, so the collapse didn't start with no warning, as observed from the inside. He had at least a few seconds to report the damage as the collapse was starting.

That account was from testimony of the father that was on another DVD documentary that I have. I'd have too look it up again to see which one.
Al Khwarizmi - step-by-step
Arthur.

1) Is it easiest to
(i) topple a building over to one side, or
(ii) collapse it into its own footprint?

2) What method is used to topple a building?

3) What kind of structural damage did building 7 allegedly sustain?

4) What kind of collapse did building 7 resemble?

QUOTE
I believe I've listened to all the publicly released recordings made that day and AFAIK there is not one CRACK in the bunch.

exhibit A - a linear shaped charge:
http://www.whatreallyhappened.com/IMAGES/l...aped_charge.wmv

exhibit B - a 911 explosion:
or
http://www.whatreallyhappened.com/IMAGES/w...s_explosion.wmv

Hear no evil.
einsteen
Back to where I was, DBB I saw you agreed with the factor 3 between E1/h and the static force. I have this picture in mind

http://i21.tinypic.com/ekrxu9.gif

An average force model gives of course about the same answer because the end speed after an energy sink of E1 is independent on the way it is lost, the collapse time depends a little bit. But it is not really what happened, buildings are mostly air aren't they ? A monolith wouldn't collapse I assume therefore a realistic collapse model should take into account the complexity of the situation although it will be a hard problem.

The problem that I'm having is this: The fact that the initial acceleration is 2g/3 for wtc1 means that the whole structure is responsible for that, if the E1s are stronger to the bottom that might explain that why the top one fails first, but after that we have a new structure of one less story that gives a new resistive force, that force is the result of the shorter composite structure.

I still think that the problem in which one story is crushed and the parts below are not coupled is seriously questionable.
einsteen
I can't edit my post, but I mean that in the leading papers it looks like they only look at the underlying story if I'm right and not as the structure as a whole. A constant resistive force is more something you expect for a block falling in a electric field or through a dense liquid
QUOTE (Al Khwarizmi - step-by-step+Oct 7 2007, 04:26 AM)
Arthur.

1) Is it easiest to
(i) topple a building over to one side, or
(ii) collapse it into its own footprint?

2) What method is used to topple a building?

3) What kind of structural damage did building 7 allegedly sustain?

4) What kind of collapse did building 7 resemble?

exhibit A - a linear shaped charge:
http://www.whatreallyhappened.com/IMAGES/l...aped_charge.wmv

exhibit B - a 911 explosion:
or
http://www.whatreallyhappened.com/IMAGES/w...s_explosion.wmv

Hear no evil.

1) I'd assume its easier to make it go straight down.

Keeping it in its "own footprint" is certainly a challenge.

Of course NONE of the WTC towers fell in their own footprint.

WTC 7 damaged the buildings around it and a quite a bit of it fell South, across the street onto the already damaged WTC 5.

2) I'm not a demolitonist but it appears they make internal structural changes and then set a precisely timed series of asymetrical charges causing the structure to loose support first just on one side.

3) Unknown. NIST's working theory
QUOTE
An initial local failure occurred at the lower floors (below floor 13) of the building due to fire and/or debris induced structural damage of a critical column (the initiating event) which supported a large span floor bay with an area of about 2,000 square feet;

Vertical progression of the initial local failure occurred up to the east penthouse, as the large floor bays were unable to redistribute the loads, bringing down the interior structure below the east penthouse; and

Horizontal progression of the failure across the lower floors (in the region of floors 5 and 7, that were much thicker than the rest of the floors), triggered by damage due to the vertical failure, resulting in a disproportionate collapse of the entire structure.

4) EVERY collapse is unique. In the WTC 7 case it was one of the QUIETEST (no series of explosive CRACKS) and certainly one of the SLOWEST (~ 14-18 seconds) collapses I've ever seen. Unfortunately we don't get a view from the South, or of the lower 20+ stories.

As to that last video, its unsourced as to time and place, Interestingly it doesn't correlate with any other videos (same explosion at same time) and its clearly (based on shadows) after both towers had fallen, but well before WTC 7 has fallen.

Arthur

atmosphere
QUOTE (adoucette+Oct 1 2007, 01:44 PM)

So what?

You need MORE than that to say it was a CD.

Got ANYTHING?

Arthur

There is no proof for explosives but that also goes for the collapse theory.
In this case i cant see how fire was able to heat vertical columns that far that they failed. I red the NIST report on WTC 1 and 2 and 7. Their explanation on the towers collapsing make sense , but i have doubts about the way WTC 7 is analyzed.

The controlled demolition theory is backed up by an experienced undependent demolition expert . His company : www.jowenko.com
David B. Benson
QUOTE (einsteen+Oct 7 2007, 05:37 AM)
A monolith wouldn't collapse ...

The fact that the initial acceleration is 2g/3 for wtc1 means that the whole structure is responsible for that ...

I still think that the problem in which one story is crushed and the parts below are not coupled is seriously questionable.

Yes. Or rather, the entire bottom block.

Yes. However, the trussed floors were so weakly coupled to the exterior walls and also the core that crushing the trusses was almost independent. The undamaged portions of the exterior walls and also the core columns, below the damaged parts, obviously put up some resistance.

I don't yet see your difficulty, but I need to point out that your picture is wrong in an important detail:

F_stat = F_max,

just enough to fully resist the force of gravity.
David B. Benson
QUOTE (atmosphere+Oct 7 2007, 08:23 AM)
The controlled demolition theory is backed up ...

And denied in the B. Blanchard report, available from the Implosion World web site. Mr. Blanchard interviewed all the lead people working on cleaning up Ground Zero, including the remains of WTC 7.

No evidence of explosives, by people who use such professionally.

David B. Benson
QUOTE (einsteen+Oct 7 2007, 06:41 AM)
I can't edit my post, but I mean that in the leading papers it looks like they only look at the underlying story if I'm right and not as the structure as a whole.

A constant resistive force is more something you expect for a block falling in a electric field or through a dense liquid

In Bazant & Verdure, the resistive force is given as a function of the drop distance. For the first 3 seconds of the collapse of WTC 1 the approximation of a constant resistive force gives a very good fit to the data. In Bazant/Le/Greening/Benson the resistive force is estimated for the entire crush-down. For WTC 1 this gives a crush-down time of about 13 seconds, the good agreement with the seismogram and also with audio analysis.

For fluids the resistive force depends upon the speed raised to a power which increases with the speed. Hence for dense liquids the terminal speed is quickly reached. But for the crush-down equation there does not appear to be a terminal speed, as best as I can currently tell. In any case, the resistive force in the towers is not thought to depend upon the speed of the descending crushing mass.
einsteen
QUOTE (David B. Benson+Oct 7 2007, 04:50 PM)
F_stat = F_max,

just enough to fully resist the force of gravity.

That's true, but that is not what happens during the collapse. Once there is movement the maximum force can always be overcomed.

Assume you are able to increase the static force (not by dropping moving mass) then it will build up until a maximum value is reached and then the story will break. The story cannot break with a value which 1/3 of the static force. Now dropping a block this peak will be reached very quickly and as long as the area under the function is not more than the kinetic energy of the top block it will not stop. The height of Fmax is irrelevant. If one sets up a differential equation with that function then the velocity at a height 0<x<h can be determined using the kinetic energy left after some drop and that is the kinetic energy of the top block minus the area under the function at a certain place. I'm sure my function is a more realistic picture than an equal force model, that should be dropped.

For the first 3 seconds of the collapse of WTC 1 the approximation of a constant resistive force gives a very good fit to the data.

ok, but the reason is that the area is the same as I said, that does not mean the force is constant, that is very unphysical, in other words impossible.
David B. Benson
QUOTE (einsteen+Oct 7 2007, 10:34 AM)
The height of Fmax is irrelevant.

False.

It is much better for these considerations to use the normalized, nondimensionalized form of the crush-down equation, (22) in B & V:

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

where s is the stretch parameter, Z is the drop, Z0 <= Z <= 1, Z' is the speed and Z" is the acceleration. So if

F(Z0) = Z0

then the tower remains standing. The only way the tower can begin to accelerate when Z' = 0 is for the force to be less than Z0. Once Z' is great than zero, the collapse can still be stopped by a sufficiently large F(Z). Just study the differential equation.

Recall that the crush-down equation assumes homogeneous structure. For more detailed formulations, see B & V. However, from the actual data, homogenization gives a better fit to the data than a floor-by-floor approximation.

Edited to add: Consider the static, intact structure. The crush-down equation still applies at every elevation Z, 0 <= Z <= 1, with 0 being the top and 1 the bottom. At every Z, Z' = 0 and Z" = 0, so at every Z,

F(Z) = Z.

This even makes common sense. At the top there is no mass so nothing needs resisting. At the bottom there is the entire mass of the tower, so the resistive force has to be 1, the normalized form of Mg.
Trippy
QUOTE (adoucette+Oct 8 2007, 02:42 AM)
WTC 7 damaged the buildings around it and a quite a bit of it fell South, across the street onto the already damaged WTC 5.

So, WTC7 fell at least somewhat asymetrically, and it fell asymetrically in the direction of the face that the eye witness reports say had the most damage done to it.

Gee. Who saw that coming.
einsteen
QUOTE (David B. Benson+Oct 7 2007, 05:49 PM)
The only way the tower can begin to accelerate when Z' = 0 is for the force to be less than Z0.

That is for collapse initiation in that case the static force needs to be overcomed. But a constant force through the whole collapse is not realistic.
The velocity a story lower is independent on Fmax, it's the area under the function that matters.
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