New collapse footage of WTC7 and North Tower - Nov 2008

[El Nino]

http://www.youtube.com/watch?v=oQeQi5XXfz0

On a side note: Vote O'Cain '08'
For More of the Same!

[yodajazz]

This reply puts it this way:

Re post the characteristics of controlled demolition for all the so called "Debunkers"

#1.Sudden onset.
#2.Symmetrical collapse
#3.Near free fall speed.
#4.Total collapse{Not partial or localized}
#5.Sliced steel.
#6.Pulverization of concrete.
#7.Pyroclastic dust clouds.
#8.Horizontal ejections.
#9.Demolition rings.
#10.Eyewitness testimony of explosions.
#11.Molten metal.

Good evidence listing. My question would be: Why was there a symetrical collapse of WTC 7 if the damage came from the side of the twin towers?

[thx1138]

More evidence of 9/11 pre knowledge:
http://www.prisonplanet.com/ex-cia-man-warned-top-executives-to-leave-new-york-on-911.html

[trish]

We had a discussion of this in this forum during the summer months. Since than I thought a little more about and came up with the following:

THE PIP MODEL OF TOWER COLLAPSE:
The following is a quick analysis of the physics, not the engineering, aspects of tower collapse. The model that is presented is an idealization based on the physics of Galilean free fall and Newtonian conservation of momentum. We ignore the engineering and architectural geometry because our concern here is merely with the physics of collapse, the order of magnitude calculations of the released energies and dynamics of the fall.

Let’s just consider for the moment the fastest falling pancake model of collapse. It’s an admittedly idealized model based on two assumptions:

1) When the falling upper segment of the tower crashes onto the floor directly beneath it, the collision is perfectly inelastic; the momentum of the upper segment before the crash is equal to the momentum of the moving augmented segment after the crash. (The falling portion of the tower before the crash is augmented by the floor it collided with after the crash).

2) Between crashes the upper segment of the tower free-falls one story to the next floor.

Let call this model the Perfectly Inelastic Pancake (PIP) model. It is the most idealistic of the pancake models of collapse and the fastest of all the pancake models.

Let M denote the mass of the tower. If f is the fraction of the tower that is falling at time t, and if u is its velocity at that time, then the momentum of the fall at that time is fMu. If at that moment the falling upper segment crashes onto the floor directly beneath it and sets it in motion with velocity v, then the momentum after the crash is (f + 1/N)Mv where N denotes the total number of floors the tower had. By the assumption of conservation of momentum,

fMu = (1 + 1/N)Mv.

This allows us to solve for v given f, M and N. Now if s is the spacing between floors and if Dt is the time it takes the falling portion of the building to drop through distance s to the next floor, then by assumption (1),

(-1/2)g (Dt)^2 + v Dt = s.

Here g is the acceleration due to gravity. Since s, g and v can be found, this can be solved for the time to fall one floor, Dt. Caution: the result will depend on the floor. The time between successive crashes (we will show) diminishes with the collapse of the tower.

Now that we know the initial velocity v of this interval of free-fall and its temporal duration Dt, we can compute the velocity u + Du at floor level using


u + Du = g Dt + v.

Now we can just repeat the calculations iteratively to model the folding up of the tower; i.e. reset u = u+Du and f=f+1/N etc.


Now to apply the model, let N=110, and suppose the collapse begins on the 80th story. Further suppose s = 12 feet, and M=0.5 million tons. The following Mathematica program (posted here as a jpg file below) iterates the above procedure starting with these initial conditions to produce a graph of the fall.

AN EXERCISE:
Imagine a 110 story tower. Let the total mass, M, of the tower be half a million tons and the spacing, s, between the stories be 12 feet. Suppose the supports of the 80th floor suddenly fail and the upper segment of the tower from the 80th floor up falls freely onto the 79th floor. Show that the velocity, u, at the time of collision with the 79th floor is 8.47 meters per second (18.9 mph). [Hint: Recall in free-fall u^2 = 2gs]. Show that the velocity, v, of the augmented segment from the 79 floor to the top after the collision is equal to 8.17 m/s (18.29 mph). [Hint: By the conservation of momentum ((110-80)/110)Mu = ((110-79)/110)Mv]. Show that the amount of energy "lost" during this collision is 304 million joules (equivalent to 146 pounds of TNT). [Hint: The kinetic energy before the collision is (1/2)((110-80)/110)Mu^2 and the kinetic energy after the collision is (1/2)((110-79)/110)Mv^2]. This is the energy made available by the collision. The presumption of this model is that this energy is sufficient to cause the immediate failure of the 79th story supports. Below we show each successive crash releases ever greater energies. The final supports are exploded by a collision that makes available an energy equivalent of 1.2 tons of TNT.

SUMMARY:
The above model assumes that each successive clash of tower with floor is completely inelastic; i.e. after the collision the two fall together at the same speed. Generally the sum of potential and kinetic energy is not conserved in inelastic collisions. The imbalance is due to the generation of heat, vibrations, breakages etc. For the example: the energy loss graph (posted here below) illustrates, in terms of tons of TNT, how much energy is released for these purposes with the passage of time. A more detailed model would have to include the geometry of all the support structures holding the floors in place and one would have to know all their physical thresholds. Because these features are not included in the model above, the PIP analysis will be the pancake model of quickest descent. The last graph above compares the PIP predictions with free-fall. Notice the time of fall predicted by PIP is 8.8 seconds compared to the time of free-fall which is 7.7 seconds. Free-fall is the idealization of collapse through well timed sequential demolitions. The idea is that explosives are used to knock out the supports of each floor before the falling segment actually crashes with floor below it. Hence there is nothing to interrupt its fall.
Obviously the example chosen above is similar in initial characteristics of the fall of the World Trade Center Towers in 2001. Those collapses, started between the 74 th and the 95th story and are reported to have taken 10 seconds. The free-fall model and the PIP model both give reasonably accurate predictions of this single temporal parameter. This doesn't mean that pancake models of collapse cannot be eliminated from consideration. But to do so one would have to show that no model of this family can 1) produce the energies required for support failure and at the same time 2) produce a collapse that concludes within the approximate 10 second window.

The PIP model obviously comes in under the window. Moreover, the available energy chart for the PIP model demonstrates that after one second each crash releases more energy than two tenth of a ton of TNT, enough to sustain the continued collapse of the tower. In the case of the WTC towers the initial collapse was preceded by a jet fueled fire. The melting point of steel is beyond the combustion temperature of jet fuel. However, for many centuries baker's have known that wood fueled brick ovens can be built to achieve temperatures well beyond the temperature of an ordinary campfire. This is because ovens are insulated and built of materials of high heat capacity. The heat of the wood fire accumulates within the oven, raising its temperature. There were 60 tons of jet fuel emptied onto the floor of the breached story of the first tower and the first few stories below it. One ton of jet fuel, when burned, will release an energy equivalent to 15 tons of TNT. Sixty tons will release the energy equivalent of 900 tons of TNT, or 3.6 billion BTU of heat energy. A tiny portion of this would be enough to raise the temperature of the steel girders, bolts, plates and other steel structures to the buckling temperature of 1500 degrees F. Once the heat expanded steel was weakened to this threshold, the damaged floor would simply fold away like tin-foil under the one eighth million tons of building above it, initiating a self-sustaining collapse of successively higher energy collisions.

[chefmike]

Thanks for putting it in terms I can understand, trish.

I know wood ovens.

Although I prefer a blend of hickory and oak instead of jet fuel.

[yodajazz]

...


Sound like you are saying that the official collapse version is possible, but I may be wrong. Is that what you are saying? Still I have a basic question. Why does jet fuel not melt the engine metal if it is hot enough to make the metal structure of the WTC? But now that I think about it, the plane crash did release a lot of energy at one time.

[thx1138]

Jet fuel burns very hot but only for a relatively short time. Once it's burned up the fire continued with the burning of the internal materials like wood, paper etc. The collapse could have neen facillitated by partially severing key steel connectors in the weeks prior to the event. A bush relative was in charge of building security at the time. An interesting coincidence. And very fortunate for Larry "pull it" Silverstein who then did not have to pay billion$ for asbestos remediation.

[trish]

Jet fuel burns fast when "fanned" by the air stream rushing through the turbines at hundreds of miles per hour (essentially matching the speed of the plane through the atmosphere). The high altitude air going into the turbine is cold and coming out it's hot. So not only does the airstream through the turbines provide sufficient oxygen for a quick burn, it carries away the tremendous heat of combustion (answering Yodajazz's question).

In the oven of the twin towers, there was much less oxygen and consequently a slower burn and the heat was confined by the insulated walls of the buildings. The heat was stored in the concrete and steel just as the walls of a wood fueled oven store up heat and reach temperatures many times higher than that of an open wood fire (as chefmike, being a chef, is aware...hi).

Yes, the pancaking model of collapse is consistent with the facts as I'm aware of them.

[thx1138]

Trish: how do you explain the pools of molten iron at the bases of the WTC towers after the debris was removed? Iron's melting point is far above the temperature generated by burning jet fuel according to what I've read.

[thx1138]

Less oxygen? the buildings had big holes and the wind was blowing into them fanning the fires.

[trish]

Trish: how do you explain the pools of molten iron at the bases of the WTC towers after the debris was removed? Iron's melting point is far above the temperature generated by burning jet fuel according to what I've read.

High heat capacity materials held the energy released via combustion. As the heat accumulated the temperature rose. For hundreds of years people have exploited this principle (and others) to melt metals using wood fuels which in the open air burn at temperatures too low to melt most metals.


Less oxygen? the buildings had big holes and the wind was blowing into them fanning the fires.

The speed of a jet airliner is hundreds of miles per hour. This is one to two orders of magnitude higher than the winds that normally blow through Manhattan. Of course the heat of the fire created some additional currents that entered the openings of the building below the fire and were drawn up as in a chimney. But these currents did not measure in the hundreds of miles an hour (otherwise the people escaping down the stairs would have been blown back up the stairwell).

The issue of the rate of combustion (not to be confused with the heat flux through the oven/building) is somewhat irrelevant. The same amount of energy is released (the equivalent of 900 tons of TNT) whether it took fifteen minutes to burn all the fuel, or an hour. That heat was stored in the walls and materials of the building turning those floors into a furnace hot enough to melt steel. That’s initially why the supports collapsed. When they collapsed the top segment of the building fell like an eighth of a million ton hammer twelve feet onto the next floor. With each successive crash the rate of fall accelerated, the hammer grew in weight and more energy was released. It’s physically possible for the entire fall to have taken less than nine seconds which in fact it did. Any liquid pools of steel that were on the breached floors would have still been liquid after those nine seconds.

[broncofan]

thx,
What's your theory? That the government did it as a justification for the wars (they were planning) in Afghanistan and Iraq or that Larry Silverstein did it as an insurance scam? Did Larry work with the government, who despite having a budget of billions and billions of dollars wanted to help this individual collect insurance money?

This is the biggest insurance scam in history. This one man, that the government was in cahoots with was able to pull the wool over everyone's eyes including the normally very vigilant insurance companies. You think the ceo's of these insurance companies have read Alex Jones and he should be brought in as an expert witness?

Seriously, tell us what happened. How did Larry do it and who's on his payroll?

[voy4her]

PNAC , a 90s conservative thinktank consisting of many future Bush cronies, had a number of goals for their Orwellian vision of a future America. As they stated in their report (which had the WTC in crosshairs on the cover) they could not achieve their goals without a "New Pearl Harbor".
Building 7 which was almost completely undamaged by falling debris just happened to house all of the SEC's paperwork on the cases they were investigating in order to prosecute. Add to that the billion dollar asbestos removal bill, and suddenly 3000 american lives dont matter so much to people like Dick Cheney, who can use their deaths to achieve further goals.
WHen you look at the fact that the WTC was built to withstand 2 plane collisions each, that jet fuel doesnt burn hot enough to melt steel, and that no steel skyscraper has ever collapsed due to fire damage, that everyone on the scene heard many explosions, that there were pyroclastic dust cloads, and that no evidence of a jumbo size plane was pulled from that tiny 18 foot hole in the pentagon, no titanium engines, and we are told that this titanium was incinerated but paper survived, when you look at the bullshit that is the shanksville story, you can only conclude that while we may not know exactly what happened, we can sure as hell figure out that the real conspiracy story is that 19 arabs with boxcutters who couldnt pass the necessary flying tests in a twin engine Cessna somehow evaded all our air defenses and flew passenger planes unchecked for over an hour before crashing them into some of the most sensitive targets in the country. Wake up and smell the flesh burning, people. Seriously.

[yodajazz]

But what about the fact that one of the hijacker's passport survived a steel melting collision, and was found outside the WTC?

[thx1138]

http://firefightersfor911truth.org/?cat=11 But then what do firefighters know about large conflagrations?

[hippifried]

Steel generates its own heat when under stress. That was a lot of stress.

I've never bought into the theory that the jet fuel melted anything other than some furniture & plastic plants. Especially on the second tower where most of the fuel blew out into the open air. It's kerosene & doesn't burn that hot. Not hot enough to melt a steel superstructure. I think the culprit that brought down the towers was vibration, & that the towers collapsing from the top is an optical illusion.

Highrise skyscrapers are designed to be partially fluid. They need to sway in the wind. An intense vibration, coupled with the immense weight of a building that big through a flexable structure, & you can create a liquefaction of the structure, the base, & the ground surrounding it. Basically a mini-earthquake, with the epicenter right at the building's foundation. Vibrations can & do intensify as they travel, like a cracking whip. I've personally seen a guy on a construction site shatter his wrist when the pick he was wielding hit some hard caliche. It was just vibration traveling through the handle. I've seen plastic bird protection balls on the guy cables of a radio tower set up a harmonic bounce that started the tower twisting to the point of extreme danger of collapse. When you take into account the prior damage to the foundation from the '93 bombing, the plausibility of my vibration theory becomes even more plausible. Well, in my mind anyway.

I'm not making any conspiracy claims. The planes brought down the towers. I just think the whole theory of burning kerosene melting steel & concrete makes no sense. The towers came straight down. No toppling, as would be expected if the collapse was from the point of impact. The collapse followed the pattern of an earthquake, & the first collapse would have started the process all over again at the base.

Just my 2 cents.

[El Nino]

But what about the fact that one of the hijacker's passport survived a steel melting collision, and was found outside the WTC?

Well, how ironically conveinent!

[daveskarety]

9/11? Total Inside Job! I am still amazed when I meet anyone who thinks otherwise. However it pays to consider the words of Arthur Schopenhauer;

'All truth passes through three stages. First, it is ridiculed. Second, it is violently opposed. Third, it is accepted as being self-evident.'

I reckon we are still somewhere in Stage 2, but the times they are-a-changin...

[trish]

Each plane was carrying 60 tons of jet fuel. Jet fuel will of course burn at a relatively low temperature. But jet fuel is energy dense. It carries more energy per ton (in the form of chemical bonds) than almost any other compound. That why it’s an ideal fuel. The 60 tons of fuel held an energy equivalent of 900 tons of TNT. The materials of each floor of the WTC have an approximate mass of 4550 tons. If all the energy of the jet fuel was held as heat by materials of the floor on which it burned, that would be about 100 kilocalories of heat per pound of materials. A back of the envelope calculation shows that amount of energy distributed as heat throughout the floor would raise the temperature of the whole to about 2700 degrees centigrade. The melting point of steel is about 1500 degrees centigrade.

The above is just a back of the envelope calculation. Of course the energy released by the burning fuel isn’t all stored in the surrounding materials as heat. Some heat is carried away by convection and some fuel is spilled outside the tower. Surely fuel was burning on more than one floor. However, the heat that is produced isn’t necessarily evenly distributed throughout the breached floors. The heat will be stored near the points of combustion, presumably where the fuel pools. These smaller regions could store even more than 100 kcal of heat energy per pound of material.

The theory that burning jet fuel in a partially enclosed building cannot possibly melt steel is busted.

Hippiefried offers an interesting theory that some sort of vibration plays a key role in bringing down the towers. It’s worth considering but I can’t find a satisfactory driver for such an oscillation. The original impact would’ve have created oscillations traveling around and down the tower, perhaps even reflecting off the bottom and traveling back up. But sure these would’ve dampened to nothing in the time it took the towers begin their collapse. Moreover, the energy of impact waves can’t exceed the energy of the impact which is relatively small in comparison to energies we’ve just been considering. It’s a bit like expecting a tree to be toppled by the impact of a bullet. Perhaps the initial oscillations were reinforced via resonance. But this theory would require some source that would continue to drive the oscillations. What source? I have no suggestions. But it’s an honest proposal.

It is not an honest proposal when someone claims it’s a “Total Inside Job!” without so much as giving a reason. Arthur Schopenhauer, by the way, was prone to dramatic overstatement. Most truths are in fact mundane, taken at face value and immediately accepted.

[hippifried]

Gravity isn't just a good idea. IT'S THE LAW!!

It isn't necessary for the oscillations to continue till the collapse. You just have to create enough damage at the foundation or throughout the central superstructure & let gravity do the rest. We're talking an enormous amount of weight, with 2 different structures holding it up. The elevator shafts in the center are a tubular concrete superstructure. The exoskeleton is tubular steel verticle ribs, surrounding the building & going all the way up. The individual floors span between the shafts & the exoskeleton, tying the 2 structures together & keeping everything plumb. Each story is a guy. It's a great engineering concept for keeping the building standing like it's supposed to with enough flexability to withstand high winds & other natural forces.

We're not talking natural forces here, are we? A direct explosive impact to the central superstructure at the upper floors is a whole different animal. There's no anchor at the top to dampen the reverberation from the impact. There would be whip action vibrations through each of the ribs in the exoskeleton. But the oscillations of the central structure would be a different frequency. Different material. Concrete is brittle. It can withstand tremendous downward pressure, but not shear pressures. It'll crack. The structural steel inside the concrete can't hold all that weight. It would tend to bend & twist at the shear points (cracks), adding even more stress to the concrete. I imagine the shafts were busted up from top to bottom, & so was the footing they were sitting on. The only thing holding it up was the rebar. Of course we'll never know for sure because anybody who was inspecting the superstructure at the time of the collapse is incapable of reporting their findings.

No structure is designed to take that kind of stress. They are however, designed to handle fire. Even if a case can be made for the blast furnace theory of intense heat, what's to melt? The exoskeleton didn't melt. It remained intact, despite the damage at the point of impact, right up till the collapse. I've heard claims that the structural steel inside the concrete melted. Huh? Concrete is an insulator. Besides, it's the concrete itself that's holding everything up. Not the steel inside of it. If the fire had attacked the shafts, it would have taken out the doors first & gone up the shafts. There'd be footage of flames shooting out the top of the building. Didn't happen. So far, I haven't had anybody try to insult my intellegence by telling me that this super kerosene could reach volcanic temperatures & melt or burn the concrete itself. That leaves the domino theory of melted floor anchors causing the floors to fall on top of each other, creating a chain reaction. This actually sounds plausible, but there's a problem with it. Such stress would tend to make everything push outward & away from the central structure. Steel bends. The exoskeleton would have buckled outward. It would have peeled back like a banana. The building would have exploded, leaving the elevator shafts intact. Like running your fingers down a twig & peeling off the leaves. That didn't happen. The buildings came straight down & stayed mostly within the skeletal structure until they crashed at the bottom. Every piece of footage I've seen tells me "implosion" & collapse of the central structure, dragging the skeleton down from the inside.

I'm no engineer, so I can't do the math on all this. But I'm thinking that the energy released from the burning jet fuel is miniscule compared to energy from harmonic reverberations through a hollow rigid shaft over 1500 or 2000 feet. Thump a tuning fork. You can barely hear it. But hold the base up to your forehead & the sound comes through clearly. What you're actually hearing is your skull vibrating. The forks vibrate through the base & the bone, despite the dampening from your fingers holding the base & the soft skin on your head separating the steel & bone. The frequency is controlled by the forks, & it'll keep going for a while.

It's not the 60 tons of burning fuel that brought down each tower. It's the 60 tons at high speed making impact that caused the collapse. There was no inside job. The only conspiracy was between the hijackers. The big mistake was convincing passengers to humor hijackers. That won't happen again.

Thank you thank you. I'm here all week. :D

[trish]

60 tons of mass flying at 300mph (using .5*m*v^2) has kinetic energy equivalent to 0.18 tons of TNT. Nowhere close to the to the energy equivalent of 900 tons of TNT that's released by burning the fuel.

Still, I now understand your theory a bit better. I'll try to find some time to give it some thought.

[trish]

Hi hippiefired,

I gave your proposal a little thought.

The first thing I should point out is that part of your theory seems to be based on a misconception about resonance. Let’s consider your tuning fork example. Strike the fork and it rings. A good fork will actually ring for a relatively long time. But the fact that you can hear it and the fact the you can feel its vibrations as you hold the base between your fingers shows that its energy is dissipating into the air and into your fingers. It’s also losing energy to internal friction between the very molecules of the vibrating fork. These drains dampen the oscillations until, for all practical purposes, the fork is still. Now strike the fork again. Place the base on a resonator, like the body of an acoustic guitar. Suddenly the sound is so much louder. It’s as if the resonator amplified and added energy to the output of the fork. In fact there is no more energy than the energy of you gave the fork by striking it. The energy that was lost to you fingers is not drain into the soundboard of the guitar and causing it to vibrate. So why is the sound louder now? The small arms of fork are inefficient movers of the air around them. On the other hand the broad flat surface of the resonator is quite good at moving air, causing it to vibrate. The greater the volume of vibrating air, the greater the volume of the sound you hear. Now that the tuning fork is driving the soundboard, it will lose energy and dampen more quickly.

The above example merely shows how soundboards are effective at “amplifying” an aural experience without adding energy to the system. A better example of resonance is a playground swing. A swing loses energy by wave propagation through the frame, through air resistance and friction at the joints. Nevertheless, by carefully timing your thrusts you can drive the swing to ever greater amplitudes of arc. Clumsy timing can have the opposite effect of actually dampening the motion. Each push does work on the swing, either to dampen its motion or amplify it depending on when and where one pushes. By careful timing one can accumulate and in a sense store energy in the swing. The more energy stored in the swing, the greater the amplitude of its motion. Bridges too can be made to vibrate. If driven at the right frequency a bridge can be made to collapse, as in the Tacoma disaster. Swings and oscillating bridges do not add to the energy that’s employed to drive them. If they are driven at their resonate frequency they will accumulate and store the energy. The greater the amount of stored energy, the greater the amplitude of motion. If the amplitude is high enough the swing will wrap around the pole or the bridge will crumble. [Just like storing energy as heat in an oven. The more energy stored, the higher the temperature, regardless of the low temperature required to burn the fuel].

Your suggestion is that oscillations initiated by the impact on the twin tower were amplified in the way a resonator amplifies the sound of a tuning fork. As I’ve tried to explain above, the resonator does not add energy to the oscillations; it only makes use of the energy provided by the tuning fork. The energy made available by a 100 ton aircraft flying at 500 mph is equivalent to the energy stored in about a half ton of TNT. This is small compared to 900 tons of TNT which is the energy equivalent to that stored in 60 tons of jet fuel. Still, a half ton of TNT is nothing to sneeze at and if placed correctly I imagine it could do considerable damage. A lot of the kinetic energy of the plane was expanded by breaching the building and stopping the plane. But some of that energy no doubt propagated through the structure as oscillations. I’m in no position to guess how much. Nor do can I guess how the waves might have propagated. (Actually at the moment I’m too lazy to guess).

I like the banana peel metaphor you engage were the towers to collapse pancake fashion (mmmm pancakes and bananas). But I’m not convinced it necessarily applies. As the top segment of the building drops like a hammer onto the next floor/ceiling, I expect that ceiling to buckle (at lightning speed) into the relatively hollow space between ceiling and floor pulling the sidewalls along with it before it crumbles and all is swept along by the plummeting hammer. Of course these sorts of details depend on the structural components of the towers with which I’ve been adverse to acquaint myself. My interest in these matters goes only so far.

I think I’ve established two things. First, pancake models can be nearly as speedy as free fall and indeed the observed ten second window is easily achieved by some pancake models of collapse like the PIP model I discussed in some detail on the first page of this thread. Second, were even a small fraction of the heat energy generated by burning 60 tons of jet fuel stored within the materials of the breached floors, temperatures exceeding the melting point of steel could be achieved. Hippiefried also points out the energy of impact is not unsubstantial: I personally don’t want to be anywhere near half a ton of TNT when it explodes.

One could go on forever debunking the so called physical evidence against the conspiracy theory; that after all is the nature of conspiracy theory...conspiracy theories have no “exit” strategy…there is no point at which the faithful are willing to say the evidence against them is conclusive. Evidence for the conspiracy is always undeniable and evidence against is always too convenient to be anything but a lie, a part of the conspiracy itself.

[hippifried]

Hi back atcha Trish,

The problem with the pancake theory is that WTC is the first ever claim of pancaking from the top. We've seen lots of pancaked buildings in the aftermath of earthquakes. Most of them happen after the quake subsides. There's that pesky gravity law again. They're all failures from the bottom. The ground floor collapses first. The footage I've seen of 9/11 shows the collapse starting above the impact floor. What broke the top floors loose? If it was a pancake, it would have started at the collision point. You know. Where all that burning kerosene melted the floors loose. A gap would have appeared, if only for a short time. Didn't happen. When the north tower goes down, there's parts of the exoskeleton still intact & waving in the breeze. Not for long of course because of all that debris at the bottom. The elevator shafts are gone. Pancaking might have finished off the collapse & even exaserbated it, but it didn't start it.

When the planes hit the towers, the fuel tanks ruptured & created a flash fire. The windows were shattered, & most of the burning fuel exited the building. Most of the fuel was gone in seconds & almost all of it gone in minutes. Black smoke denotes inefficient burning & the oven effect doesn't wash because the heat wasn't contained. By blowing out the windows, the floors were fully ventilated. See how hot your oven gets or stays if you leave the door open. Even if the fire storm was hot enough to melt steel (I'm still not convinved), there was lots of cool down time before the collapse. This theory of the jet fuel bringing down the towers started the same day, & has never set right with me. It makes so little sense that it drives the conspiracy theories by giving them credence.

Then there's this collapse of WTC 7. No jet fuel there. Debris? I don't think so. You can see it collapse from the center in. That reeks of implosion from collapse of the elevator shafts. The elevator shaft is always the central structure of any commercial building more than 1 story. The building comes straight down just as if it was a planned demolition, which adds more fodder to the tinfoil hat "inside job" speculators. The only other thing that explains it is shockwave liquifaction from beneath. The tower collapse could easily create that shockwave through the ground. How is that collapse different from the towers themselves?

Concrete is man-made limestone conglomerate. Artificial rock. Shock shatters rock. You can shatter a good size boulder into manageable muck with 2 or 3 sticks of primer (TNT) & a couple of sacks of powder covering it & just sitting on top of the rock & tied into the shot. The explosion of the jet fuel shotgunned out the windows, nullifying a big part of the compression effect. But the initial shock, along with the impact itself would have been enough to send a shockwave through the shafts that multiply in number as you go down, & create an amplified feedback with more than enough reverberation to crack the man-made rock that's hollow, only a couple of feet thick, & carrying a tremendous load. It doesn't have to shatter. It just has to crack & weaken. Gravity does the rest.

Now this is a nice conversation. Civility is so much more pleasant than name calling. Anyway, you're the egghead. Check out the math. I couldn't if I wanted to. I never studied law, judicial or physical. I'm sure there's some string theory that'll prove anything you want. :D

[trish]

I haven’t seen a lot of films of falling towers. The ones I have seen I just happened to catch on the news or in a movie. I can’t say that I personally have noticed they usually fall from the bottom up or from the top town. Most of the examples I’ve seen have been caused either my deliberate demolition or by seismic activity. In the former case, the collapse is designed and controlled. In the later case the collapse is driven by energetic oscillations that originate at the base of the tower. The twin towers may be an exception. The historical argument which goes, “most buildings don’t fall that way” doesn’t have a lot of validity. Most towers haven’t been penetrated by fully fueled commercial jetliners before collapsing.

In an attempt to remain at my most cautious I will say that pancake models of tower collapse are not physically impossible. Once initiated (i.e. once you drop the upper segment, weighing an eighth of a million tons, of a tower twelve feet onto the lower segment) pancake collapse is entirely powered by gravity and is self-sustaining. Each inelastic collision of upper segment onto next lower floor releases enormous energy; enough, in most cases, to cause the failure the next lower set of supports and continue the collapse. Moreover the energy released increases with each floor. For the mathematical details of one such model see my first post in this thread. This does not mean the twin towers fell in this way. But it does mean that one needs to do a lot more work to eliminate the possibility.

How would one eliminate all pancake models of twin tower collapse?
1. One could study video of the collapse and demonstrate pancaking did not take place; e.g. one might discover, as Hippiefried speculates, that the collapse was from the bottom up instead of from the top down.

2. One might attempt to demonstrate the impossibility of initiating a pancake collapse in the twin towers.

3. One might attempt to argue that in the specific structure of twin towers was such that the energy released by the initial fall of the top segment of the tower onto the lower segment was not sufficient to sustain further collapse.

4. One might propose a different theory that assumes less and explains more.

5. I’m sure I’m leaving out a few other strategies.



I confess, I haven’t studied the video of the TWC collapses frame by frame. Like most people, I’ve just seen them over and over again on the news. So I can only address (1) anecdotally. I can only say that if it’s an illusion they are falling from the top down, then it’s a good illusion.

Hippiefried and others have attempted to eliminate the pancake model of TWC collapse through route (2). The usual argument is that jet fuel doesn’t burn at high enough temperatures to melt steel. My counter is that the 60 tons of fuel carried by each airliner contained the energy equivalent of 900 tons of TNT (that’s just 10% short of the energy released by a kiloton bomb). The heat released by the burning fuel would not all dissipate but would be stored in the concrete and other materials of the breached floors creating an oven. Some have objected the breach floors were open to the wind which would’ve carried away the heat and Hippiefried has also objected that most of the fuel spilled outside the buildings and what remained burned away rapidly. To these objections I have countered that compared to the 300mph winds that are required to carry away the comparatively small amount of heat generated in a jet turbine, the wind blowing through the TWC could not have carried away 357 million BTU’s of heat (the equivalent of 900 tons of TNT). Hippiefried says the fuel was mostly lost and burned away quickly. From what I remember of the video I’ve seen, the fires on the breached floors lasted quite awhile. Perhaps that just what I want to remember. But suppose 99% of the jet fuel was spilled outside the building. That leaves 9 tons of TNT or 3.6 million BTU’s of heat. Depending on its distribution within the materials of the building, that’s still is enough heat to melt steel and crumble concrete into calcium oxides and carbon dioxide gas. I can’t say this is indeed what happened at the WTCs, but it seems to me to be a likely scenario and one that certainly hasn’t been eliminated by the current objections.

It should be clear my study of the WTC collapse is not a very serious one. So perhaps its not surprising I haven’t encounter anyone proposing strategy (3). Strategy (3) would require one to argue from the specific engineering design of the twin towers. Any such argument would be intricate and involve more detail than I would have the time and patience for.

Hippiefried, in proposing his oscillation theory of collapse, has opted for strategy (4). My objection to this theory is that even if we are very generous and assume the planes had a velocity of 500mph when they collided with their respective towers, the energy of impact is relatively small, a half a ton of TNT per impact. Most of this energy was used to penetrate the building and stop the plane. If there were lot’s of energy to spare the planes would’ve burst through the other sides of buildings and fallen to the ground. Any vibration caused by the initial impact would have died out in minutes, unless (and here I’m taking the liberty to modify Hippiefried’s proposal) there was another source of energy driving the vibrations. The only other source I can think of is the wind currents that must’ve been blowing through building from the bottom up. To make this proposal work one would have to show the towers had a design flaw; i.e. a natural resonate frequency and that the chimney currents somehow drove the building to oscillate just at this frequency. My current point of view is: I don’t think this theory assumes less and explains more. That doesn’t mean it isn’t true, but it doesn’t eliminate the pancake model.

[hippifried]

My counter is that the 60 tons of fuel carried by each airliner contained the energy equivalent of 900 tons of TNT (that’s just 10% short of the energy released by a kiloton bomb).
:shock: Squeeeeeze me????!!!!!??
Other way around maybe. If that were the case, we'd be taking down mountains with jet fuel instead of dynamite. Trinitrotoluenol (Al Nobel's weapon to end all wars) is basically just stabilized nitro glycerine. Takes a blasting cap to set it off. A half pound stick primer will take out the side of your house. The cap alone will take your hand off. Think you can do that with less than a gram of kerosene? Methinks it might be time to recheck your sources. TNT is an extremely fast accellerant.

The explosion from the fuel was caused by compression of the tanks just prior to the rupture. The fuel is liquid, so without compression, there's no explosion. It doesn't burn fast enough to explode in the open air. Most of the fuel shotgunned out the windows, but the initial shock could easily rupture the concrete shaft structure. Shock, not heat.


Once initiated (i.e. once you drop the upper segment, weighing an eighth of a million tons, of a tower twelve feet onto the lower segment) pancake collapse is entirely powered by gravity and is self-sustaining.
Ah so, Grasshopper! But now we're talking tower segments as opposed to floors. This is where the heat theory really breaks down. In order to cause the floor by floor pancake effect, you have to weaken the anchors all around the building & on the shaft structure. The floors are radial spans. Other than the shaft structure itself, there's no columns inside the building. If heat were the culprit, it would have taken out a couple of floors & only on one side of the building. The wingspan of the 747 is less than half the width of the tower.

Now to me, liquifaction makes sense & it's the only explanation I can see for the collapse of the 3rd building. But that said, the beginnings of the tower collapse doesn't have to start at the bottom. It could start at the point of impact. It has to start with the shaft structure though. That's how you pull it straight down from the top. I'm thinking the anchors held better than anyone would have thought. As the central structure collapses, it drags the floors down & they pull the exoskeleton inward. Since the shaft structure is hollow, the rest of it would shatter like an eggshell as all that weight came down pushing from all angles. It'd be like splitting a log with a wedge. The amount of energy released into the ground from the collapse is enormous. I wouldn't know how to do the math on it, but I imagine it was measurable on the richter scale. There's that liquifaction. Enough to shatter any weak point in the 2nd tower, & bring it down the same way, along with the 3rd building that collapsed while the 2nd one was going down. There was no toppling anywhere. The exoskeleton did a good job containing the collapse because the floor anchors held.

Just sowing the seeds of doubt. How'm I doin'? It must be my pyrronistic nature. Is it rubbing off? :D

[trish]

TNT is an extremely fast accellerant.

Exactly, it is in fact explosive…it releases it’s energy quickly. However, one ton of gasoline will release 15 times as much energy as one ton of TNT. Gasoline is extremely energy dense. That’s why it’s a great fuel.


The fuel is liquid, so without compression, there's no explosion. It doesn't burn fast enough to explode in the open air.

An explosion of the right magnitude would’ve dropped the top segment of the building onto the lower segment immediately. But if you got an hour or two to wait around, just one percent [of the fuel] that was in that airliner, will release 357 million BTU’s of heat. Enough to degrade the concrete, buckle and perhaps melt the steel.


Ah so, Grasshopper! But now we're talking tower segments as opposed to floors. This is where the heat theory really breaks down. In order to cause the floor by floor pancake effect, you have to weaken the anchors all around the building & on the shaft structure.

The heat of the fuel is ONLY required to degrade the support materials of the breached floors. The fact that those floors were also damaged by the penetration of the plane and the initial shock also helps. Once the top segment begins to fall, nothing can stop it, especially as it gathers up more mass and more speed on the way down. I agree the likelyhood of degrading all the supports [of the breached floors] decreases with amount of fuel that was spilled. I have no actual reported numbers on that. Do we in fact know how much was spilled outside the tower and how much remained inside?


That's how you pull it straight down from the top. I'm thinking the anchors held better than anyone would have thought. As the central structure collapses, it drags the floors down & they pull the exoskeleton inward. Since the shaft structure is hollow, the rest of it would shatter like an eggshell as all that weight came down pushing from all angles.

I agree that the relative hollowness of the towers is an important feature, it allows for the entire structure to be pulled inward as it falls.

[hippifried]

In order to release all that energy from a liquid fuel, it needs to be vaporized, aerated, & ignited under contained compression. What happened to the towers was not what happens in the combustion chamber of an internal combustion engine. No compression, no power.

To melt steel, you need sustained heat of nearly 2800 degrees F.

I found this:

Jet fuel (refined kerosene) boils at temperatures above 160 degrees Celsius (350 F) and the vapor flashes into flame at 41 degrees Celsius (106 F). In an environment of 1500 degrees F, jet fuel spread thinly on walls, floor, and ceiling would boil off very quickly. If there were sufficient oxygen, it would burn; otherwise it would disperse out the open windows and flame when it met oxygen in the open air -- as was likely happening in the pictures that showed flames shooting from the windows. Some New Yorkers miles distant claimed they smelled the fuel, which would indicate fuel vapors were escaping without being burned.
Here:
http://www.public-action.com/911/jmcm/physics_1.html

There's a lot of info in a tongue & cheek look at the jet fuel theory.

[trish]

In order to release all that energy from a liquid fuel, it needs to be vaporized, aerated, & ignited under contained compression.

Not true. A hurricane lamp that burns a gram of kerosene drawn by a wick from a reservoir at ordinary air pressure will release as much of its energy as a kerosene lamp that burns a gram of kerosene vapor drawn from a pressurized tank. The only difference is the rate of burning and therefore the brightness of the emitted light. If you’ve ever spilled a lit hurricane lamp you may have experienced first hand the fact that kerosene will burn even when not wicked and when not under pressure. Though all and all, it’s a relatively safe fuel; I’m told that decades ago it was used to clean and disinfect old wooden floors in public buildings. It’s true that in the WTC some jet fuel might have spill away without burning, some may have vaporized and escaped as fumes. But 60 tons of jet fuel equates to over one million kilowatt hours of energy. I cannot rule out the possibility that some portion of this enormous store of energy was principally involved in the initial stages of the WTC collapse; not without an account of what happened to all of that store of energy. Even if only one percent of that energy was actually stored in materials of the breached floors as heat, that would be 3.6 billion BTU’s of heat!!! Do you really believe more than 99% of the fuel fell away or evaporated before being consumed by flames? Perhaps you're right, but how would we know? It seems like a lot of stored energy unaccounted for.

[hippifried]

In order to make full use of any liquid fuel, it has to be contained & controlled. Just like your lamp. As long as the rate of fuel consumption is held to a minimum, you get light for a while. If you take that same amount of fuel & light it all at once, it burns up in seconds or minutes & is gone. In order to raise the temperature, you need to add more oxygen than is in the surrounding air. If you want it to explode, you have to contain the pressurized gasses from the burn until they build up enough to rupture the containment. Kerosene burns too cold to accelerate to explosiveness without containment.

In the WTC incident, the only containment was the windows. Once containment was breached (almost immediately) the fuel which was already ignited & expanding, along with most of that theoretically potential stored energy, blew out into the open air & dissipated.

If it takes 60 tons of fuel to drive 4 or 5 jet engines for a few hours, under controlled conditions, where's this stored energy equal to a kiloton TNT explosion, a million KWH, or 3.6 billion BTUs? Answer: The same place it's always been. In a theoretical formula on a piece of paper or a computer screen. There's loads of stored energy everywhere. The whole trick is to get it released efficiently.

:smh I'm not a kid & we're not talking potentials. I was under the impression that this was a discussion of the possibilities & probabilities of what really happened in a real event.

[trish]

In order to make full use of any liquid fuel, it has to be contained & controlled. Just like your lamp. As long as the rate of fuel consumption is held to a minimum, you get light for a while. If you take that same amount of fuel & light it all at once, it burns up in seconds or minutes & is gone. In order to raise the temperature, you need to add more oxygen than is in the surrounding air. If you want it to explode, you have to contain the pressurized gasses from the burn until they build up enough to rupture the containment. Kerosene burns too cold to accelerate to explosiveness without containment.

Mostly I agree. Temperature can also be raised without increasing the available oxygen density simply by storing the released heat of the combustion in high heat capacity materials, like brick and concrete.


In the WTC incident, the only containment was the windows. Once containment was breached (almost immediately) the fuel which was already ignited & expanding, along with most of that theoretically potential stored energy, blew out into the open air & dissipated.

I simply can’t confirm that. Sixty tons of fuel is a lot of fuel to get rid of. It’s not enough volume to rise to the windows and pour out. As it vaporizes some of it will chemically combine with the oxygen carried by chimney current (referred to in our prior postings) and add its released heat into the atmosphere and into the materials of the breached floors. A lot of the vaporized jet fuel will escape. But do we have any idea of the proportion of the energy that is actually released as heat and the proportion that remains stored in the chemical bonds of the fuel?


If it takes 60 tons of fuel to drive 4 or 5 jet engines for a few hours, under controlled conditions, where's this stored energy equal to a kiloton TNT explosion, a million KWH, or 3.6 billion BTUs? Answer: The same place it's always been. In a theoretical formula on a piece of paper or a computer screen. There's loads of stored energy everywhere. The whole trick is to get it released efficiently.

Actually the answer is that the energy is stored in the chemical bonds of the fuel. The only way to have an inefficient RELEASE of that energy is not to burn all the fuel; spill some or let some boil away…which I believe is your point. [But just in case you’re thinking something else let me remark that if all the fuel is burned (quickly, slowly, under pressure or not) ALL the energy available through oxidation will be released.] I believe your claim is that the release at the twin towers was nearly 100% inefficient. I have reservations about that claim and moreover, I propose that even 99% inefficiency releases enough heat to degrade the structure of the breached floor. On these points we seem now to be repeating ourselves. Let me be the first to admit that I haven’t added anything new to my argument in the last several posts. I’ve just been trying to make my position clear and trying to get clear on your position.


I'm not a kid & we're not talking potentials. I was under the impression that this was a discussion of the possibilities & probabilities of what really happened in a real event.

The question is what proportion of the initially available 3.6 billion BTU of potential energy was actually released and what proportion of that was stored as heat in the materials of the building? Was the heat density high enough in key areas to generate temperatures that would degrade the structure of the breached floors? I propose that even if a small fraction of the initially available potential energy was converted and stored as heat, it would have been enough to initiate collapse. That’s why I think proper energy bookkeeping is essential here. But I just don’t know how to verify the alleged and conflicting accounts of various scenarios.

Even if I am repeating myself, it is BTW refreshing to have a real and honest discussion on this topic.

[hippifried]

First: I have to admit that I was wrong about the toppling. The top 20 floors or so of the south tower ( the second one hit, but the first to collapse) did fall over as a unit. It got hit in the corner.
http://www.public-action.com/911/jmcm/BBCNews/DOCS/1538563t.jpg
I'm not sure how this affects my theory. So far, not much. In order for that to happen, the central load bearing tube structure had to snap. That's a lot of breaking.
http://www.civil.usyd.edu.au/latest/wtc_plan.jpg
As it falls over, the steel columns on the other side are stressed & pull the building in the direction of the topple. But Isaac Newton says "NO!". As the top falls to the south, it pushes the rest of the building to the north. Anybody who's ever topped a tree will vouch for this. Now I'm sure somebody (not me) could come up with loads of numbers on how these competing stresses are affecting each other. I'll simplify it. the building is bending & being forced to sway farther than it would under any stresses it was designed to handle. The steel exoskeleton has some flexibility but the concrete throughout the central load bearing core tube is shattering & being pulverized all the way to the footings on the bedrock because concrete can't hold up to shear.

My position is that it's shock that breaks everything loose. It was a shock wave through the air that took out the Murrah Bldg in OKC back in '95. From the street. Same with the Kobar (sp) towers in Saudi Arabia. Concrete shatters. When the south tower collapses, regardless of why, is sends a massive shockwave through the ground. If memory serves, the siesmic shock was recorded. The north tower was damaged at the base in the '93 bombing. I don't care how you fix it, it's still just a patch. It's not like you can just jack up the building & redo the footings like Norm & Tommy do to an old Victorian. The north tower came straight down, & so did WTC 7. The tremor is right at the surface & only needs to travel a couple hundred feet down. The depth of most earthquakes is measured in miles. I'm currently in Brawley CA. Check this out.
http://quake.wr.usgs.gov/recenteqs/Maps/116-33.htm
Just click on any little square to get the details. I know a little about liquifaction, just from the watching the furniture shift. Don't worry. You get used to it. The dogs never do though.

Off to bed. This is fun.