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pres·sure ( P ) Pronunciation Key (prshr)
n.

1.
a. The act of pressing.
b. The condition of being pressed.
2. The application of continuous force by one body on another that it is touching; compression.
3. Abbr. P Physics. Force applied uniformly over a surface, measured as force per unit of area.
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They also don't seem to consider the idea that the steel in the buildings was weaker the higher up they went- this was apparent to the engineers constructing them in the 1970s and was a distressing fact to all of those who worked in them until 2001.

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Back in the early 1970s when the World Trade Towers were built, the WTC was the tallest building that had ever been built in the history of the world. If we consider the architectural engineers, suppliers, builders, and city inspectors on the job, we can imagine they would be very careful to overbuild every aspect. If one bolt was calculated to serve, you can bet that three or four were used. If there was any doubt about the quality of a girder or steel beam, you can be sure it was rejected. After all, any failures would attract the attention of half the civilized world, and no corporation wants a reputation for that kind of stupidity — particularly if there are casualties.

I do not know the exact specifications for the WTC, but I know in many trades (and some I've worked), a structural member must be physically capable of three times the maximum load that will ever be required of it (BreakingStrength = 3 x WorkingStrength).

According to Engineering and Technical Handbook by McNeese and Hoag, Prentice Hall, 3rd printing, September 1959: page 47 (Table) Safety Factors of Various Materials, the mandatory safety factor for structural steel is 600%. That is, a steel structure may be rated for a load of only one sixth the actual theoretical limit.

Given that none of those floors was holding a grand piano sale or an elephant convention that day, it is unlikely that any of them were loaded to the maximum. Thus, any of the floors should have been capable of supporting more than its own weight plus the two floors above it. I suspect the WTC was engineered for safer margins than the average railroad bridge, and the actual load on each floor was less than 1/6 the BreakingStrength. (emphasis mine)

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...but something was still burning inefficiently, leaving soot (carbon) in the smoke. A fire with sooty smoke is either low temperature or starved for oxygen — or both.

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The temperature then reached depends on the combustion rate (which depends on the oxygen supply) and the rate at which the heat generated can be dispersed. Videos of the Twin Towers show that the fires were moderate (certainly not of the "raging inferno" type) and the large volumes of black, sooty, smoke show that the fires were oxygen-deprived, not the sort of combustion that will generate high temperatures. Moreover, the jet fuel burnt itself out in about ten minutes (see below), and both buildings stood for over forty minutes thereafter.

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Using jet fuel to melt steel is an amazing discovery, really. It is also amazing that until now, no one had been able to get it to work, and that proves the terrorists were not stupid people. Ironworkers fool with acetylene torches, bottled oxygen, electric arcs from generators, electric furnaces, and other elaborate tricks, but what did these brilliant terrorists use? Jet fuel, costing maybe 80 cents a gallon on the open market.

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But let us return our attention to the fire. Liquid fuel does not burn hot for long. Liquid fuel evaporates (or boils) as it burns, and the vapor burns as it boils off. If the ambient temperature passes the boiling point of the fuel and oxygen is plentiful, the process builds to an explosion that consumes the fuel.

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.

Note that jet fuel burning outside the building would heat the outside columns, but would not heat the central load-bearing columns significantly. Following this reasoning, the jet fuel fire does not adequately explain the failure of the central columns.

Whether the fuel burned gradually at a temperature below the boiling point of jet fuel (360 C), or burned rapidly above the boiling point of jet fuel, in neither case would an office building full of spilled jet fuel sustain a fire at 815 degrees C (1500 F) long enough to melt 200,000 tons of steel.

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Steel is an excellent conductor of heat, so when you apply heat to a steel structure the heat spreads quickly. So the heat from the fires would have spread through the entire steel structure of each tower. The Twin Towers contained 200,000 tons of steel. Are we expected to believe that the fires from two loads of jet fuel provided sufficient heat to raise 200,000 tons of steel to the point where it became critically weak?

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..."stacked trays" are similar to "piston heads," which would lower the pressure, cause a vacuum, and up the temperature significantly; the buildings would implode like a soda can that has had the air removed from it-the force of these "trays" hitting each other would be sufficient to cause major shattering and cracks.

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Just an observation but have you ever watched how a building actually falls?

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* Nearly all the buildings that claim earthquake victims are heavy masonry low-rise structures, not steel-framed high-rise structures.
* Collapses of buildings of any type of construction are rare in the developed world, whose building standards anticipate severe stresses.
* Nearly all building collapses not involving controlled demolition are partial rather than total.

Excepting the 9/11/01 anomaly, the only documented cases of high-rise buildings undergoing complete collapse involved either controlled demolition or severe earthquakes. Of those, only controlled demolitions have caused such buildings to fall vertically into their footprints, leaving relatively small rubble piles, as was the case with WTC 1 and 2, and Building 7. In fact there are numerous observed characteristics of the destruction of the Twin Towers that have not been observed in natural collapse events

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Everything has inertia so the top of a building actually only starts to move when the area lower down has already started moving. Like you say you cant really see the roofline start to move for the dust, that dust came from lower floors that had already colapsed.

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Observation no 2. After the first WTC bombing there was a "modern marvels" show on the construction of the towers. It refutes the primary core of your argument. The WTC was not the strongest building ever made, or over engineered. Far from it. Very tall buildings have the same problems that aircraft have, their principle enemy is their own structural weight. Every pound higher up the building is supported by every foot of the building bellow it. This structure itself adds weight. The trick to big buildings is to keep the weight down, especially the higher you go, consequently the towers were not over engineered, every unnesccessary ton of "over engineering" actually costs tens of tons extra in the structure. You actually engineer it to just have enough strength to do the job plus a safety margin for worse envisaged weather otherwise the materials lower down would have to be "Unobtainium" or so dense that there would be no space for offices.

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The central support columns in the South Tower were mostly in tact due to the angle at which the plane crashed into the building, so they were still doing a large percentage of their job. Why didn't the North Tower collapse in 1975 if the fires were the chief cause of collapse in 2001?

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Originally posted by RolandReynolds:
Then there were the "carpets, wallpaper, filing cabinets, occasional desks..." Fires from these sources could not have had such a drastic effect on the central support columns, which were mostly in tact after impact. How can we draw this conclusion? In 1975 a fire started on the 11th floor of the North Tower, burning over 6 floors for 3 hours (as opposed to the 56 minutes of the South Tower).

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So, we know that just after impact, the majority of steel columns were in place in the South Tower, and that they were able to support the weight of the upper floors.

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The photos featured in the article, and just about anywhere else you can find them, confirms that it was black smoke pouring from the Towers. Black smoke = oxygen deprived = not an efficiently burning fire = not a high temperature fire.

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The next argument is that the steel did not have to melt, and jet fuel wasn't the only fuel for the fire.
From http://www.serendipity.li/wot/pop_mech/reply_to_popular_mechanics.htm :

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Steel is an excellent conductor of heat, so when you apply heat to a steel structure the heat spreads quickly. So the heat from the fires would have spread through the entire steel structure of each tower. The Twin Towers contained 200,000 tons of steel. Are we expected to believe that the fires from two loads of jet fuel provided sufficient heat to raise 200,000 tons of steel to the point where it became critically weak?

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A vacuum is necessarily air-tight, and lacks oxygen, which is required for combustion, which is what would raise temperature, so I think your analogy may be flawed. I do not think the environment of the collapsing Towers was an air-tight environment at any stage.

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Forgetting that we've established that none of the fires could have weakened 200,000 tons of heat-conductive steel, let's say the columns that were closest to the fire did weaken enough to buckle (and all buckle at exactly the same time).

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The fires were confined to the floors around the impact (around 4 floors, see the Loose Change documentary), so we can assume that the sections of column in the lower floors still had their original integrity. If certain floors gave way, and crashed into lower floors, in a domino effect, these lower floors would necessarily offer resistance to the falling floors above.

If you've ever played with one of those apparati with multiple swinging pendulums, you know how the transfer of momentum works - the first body transfers its gained energy onto the next. This means that every time a new floor was encountered, the upper floors would transfer their energy to the lower ones, and would then have to build up energy once again to obtain the speed they were travelling at before they hit the lower floor.

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That's physics, and they don't lie. However, you need to ask the right questions to get the relevant results. If anyone sees important questions that have not been addressed here that would influence the understanding of the outcome, I again invite you to bring them to the table.

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As of now the conclusions seems clear: The fires could not have weakened 200,000 tons of steel throughout the whole Tower enough so that it would offer no resistance during the whole collapse.

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1) You had structural damage to the building that meant that some structural elements were now missing and others were bearing unexpected loads and crossloads they were not designed for.

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As to the 707 comment. The case the towers were designed to meet was an impact like the one where the Army bomber flew into the Empire State building. Ie, lost pilot in fog flying relatively slowly and accidentally hiting the building. This was not a design envisioning a fully fueled jetliner ramming the building at close to maximum velocity (and much faster than a 707.) The design considerations dealt only with the initial impact, and as we can see that worked really well. Had there not been a fire chances are the buildings would have stayed up.

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3) Most fires start small in a small area and then spread. Fuel air explosions, or situations where an airborne accelerant are ignited cause a wall of flame that can have evrything in the area on fire in miliseconds. It could take several hours for a regular fire to spread as far and effect as much of the building as the explosion could ignite in one instant. A bigger area of fire gets hotter quicker.

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Still, it is amazing that the towers survived the initial impacts at all—even if they were designed to be hit by aircraft—considering the fact that the Boeing 767's involved in the terrorist attack were notably larger and traveling much faster than the 707 considered in the design of the World Trade Center. The 707 was assumed to be coming in for a landing when it would hit one of the skyscrapers (707's were the standard airliner at the time when the World Trade Center was built). This meant that the plane would be traveling at a low rate of speed—about 180 miles per hour—and have minimal fuel. On the other hand, the 767's were carrying enough fuel for transcontinental flights (about 10,000 gallons each) and were flying far faster. The airspeeds of the jets as they impacted the buildings were estimated at about 470 and 590 miles per hour, approximately 2.6 and 3.2 times faster than the 707 (FEMA 1.17). In addition, the 767 is about 25 percent larger than the 707, with a wingspan of 156 feet, a length of 159 feet, and a height of 53 feet (1.19). Considering the size and speed of the airplanes that crashed into the World Trade Center towers, it is remarkable that they stood at all.

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The tower didn't have a great big hole in it from a plane crash though did it. Apart from that something catastrophic, like a plane crash for instance, does a lot more damage to the structure of a building than the hole it leaves behind. It's fair to say the entire structure would have been weakened by a plane hitting it. There are incidents where planes have hit tower blocks, the buildings haven't fallen, they've sustained the impact but they are condemned afterwards because the structure is weakened.

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That doesn't mean the remaining supports can be considered as strong as they were pre-crash. There's also a reason why we stay well below stated maximums, in the real world materials never achieve them.

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You can get black smoke from Blast furnaces at 1500c. Black smoke can also indicate WHAT is burning; like for instance black smoke is what you get from burning foams used in furniture, like that which you find in say, an office. Your whole chain of causality is fallacious.

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Erm no. You don't have to raise the temperature of the entire structure, that's ridiculous. Physics (material and thermal dynamics) are on my side here. You can test it your self, take a metre pipe of steel, cut the end off with an oxyacetylene torch, and then touch the other end. Notice how you can melt the end without noticeably raising the temperature of the entire bar.

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The concentrated and hotter flame transfers heat to the steel only in the areas needed to preheat to the cutting temperature not a larger area like a conventional torch which uses 4-6 preheat flames we only use 1 in front of the cutting tip. Separate cutting and flame tips are used with our system.

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You get similar effects in homes, you don't need air tight. All you need is restricted airflow (which is a given in a building, whether you have a hole in the side or not) and a demand that outstrips the supply (like with a big damn fire). What you get is a reduced air pressure in comparison to the outside environment, which is what we call a vacuum.

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Thing is no building would ever fall like that. The towers certainly didn't actually fail this way.

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FACT: Once each tower began to collapse, the weight of all the floors above the collapsed zone bore down with pulverizing force on the highest intact floor. Unable to absorb the massive energy, that floor would fail, transmitting the forces to the floor below, allowing the collapse to progress downward through the building in a chain reaction.

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Structural collapse above would weaken the ENTIRE structure, not just the floor below. The failure points would be where most of the weight transfer was taking place, i.e. the foundations and lower floors. Once those give way there's nothing holding up the upper floors, so they fall under gravity.

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No, it's some quasi physics; you've got a couple of physics equations, implemented them poorly and in the wrong way and then made spurious conclusions.

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Although the situation never occurred in New York City, the towers were designed to withstand prolonged winds of 150 miles per hour, a thirteen-million-pound force, or the equivalent of being hit by a large ocean freighter

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Originally posted by RolandReynolds:
As I already showed, the Towers were designed to survive having plane sized holes put in them. It is not fair to say that the entire structure (say for instance, the bottom 50 floors) are compromised in any significant way by having a hole in floors 75-80. DeMartini himself uses a 'Mosquito netting' analogy, and he managed the building of the Towers.

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If they weren't compromised in any way, they are just as strong as they were. They may have to bear more weight if other supports are destroyed, but their strength remains constant until compromised. The great majority of columns in the South Tower were not destroyed.

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This is entirely possible. However, all I have unfortunately is your word in this post, with no way to verify. It is just one piece of evidence for the low temperature of the fire, though. The Loose Change documentary ( http://video.google.com/videoplay?docid=-5137581991288263801&q=loose+c
hange) contains an audio recording of a fire-chief transmitting over his radio that he had reached the 78th floor and was confident that the fire there could be contained.

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The fires in the Towers were not concentrated, high temperature (5000-6000 degrees F) flames like that of an oxyacetylene torch ( http://www.cut-like-plasma.com/info_faqs.htm). A quote from that page:

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There were no steel columns sticking up into the air, and subsequently falling over after the towers collapsed (see the Pop. Mech. reply). Everything also came down at near free fall speed. This is why the claim is made that the entire steel structure would have had to have been compromised. Had it not, large sections of steel columns (encased in concrete, which is given props for fire resistance - http://vincentdunn.com/wtc.html) would have remained.

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I don't think I have cause to dispute this. I will again point out though that if demand (for air by the fire) outstrips the supply, you will necessarily not have an efficiently burning fire.

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You're right, it didn't fall this way. But the 'experts' are saying that it did.

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If you could be specific about which equations you're talking about and the problems with their implementation, I could examine what you are talking about, and I could re-evaluate where I may have made spurious conclusions. As this is, you're just telling me I made a mistake without pointing out where (which would improve the efficiency of this conversation, I think).

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I think some people need to feel safe so badly (not just feel safe, I think, but explain why others don't feel the same way- i.e., because others just don't 'see' or 'get' what's happening around them) that they construct wild fantasies using whatever facts they can cobble together out of heresay and speculation.

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A vacuum is necessarily air-tight, and lacks oxygen, which is required for combustion, which is what would raise temperature, so I think your analogy may be flawed. I do not think the environment of the collapsing Towers was an air-tight environment at any stage.

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The core of each tower was a rectangular area 87 by 133 feet and consisted of steel box columns running from the bedrock to the tops of the tower. The columns tapered to the top, where they transitioned to lightweight H-beams, but the exact dimensions are unknown as the blueprints are under the jurisdiction of the Port Authority and are not public domain

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This reasonable explanation for WTC 1 and 2, which names as the key factor the near-instantaneous spread of fire over a large area, cannot be applied to WTC 7. WTC 7 was not struck by a plane and did not have jet fuel spread over a large area in its interior. Why did WTC 7 collapse in an identical manner to towers 1 and 2?

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Simply put, it didn't. WTC 7 was the worst building in the complex. It started on fire from falling debris. Then it was weakened by a shockwave from the other buildings falling. Then the fire came together to make the whole building (a rather small, low-budget, and poorly-built office building) collapse. If you watch video of that collapse, you will notice that parts of the builing began to fall before the whole thing went down- it doesn't look nearly as neat as the towers, and that's because it fell from secondary damage. WTC 7 is a case study for why office buildings are not as safe as we wish they were.

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Britain, Russia or Israel

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Originally posted by citizen:
Ever heard of Occams Razor?

One last thing:

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Britain, Russia or Israel

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Britian == British
Russia == Communists
Israel == Jews

My God! PirateJew was right all along! It's a conspiracy by Britain-Russia-Israel (British-Commie-Jews) all we need to do now is find the Nazis .

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More insane ramblings by the people who brought you beeeer milkshakes!
No beast so fierce but knows some touch of pity. But I know none, and therefore am no beast.

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Originally posted by GreenFaerie:
I consider myself an American Patriot. I love this country, and the people living here. But I am not fond of the government, and consider myself apolitical, because I think most politicians are crooked liars.

I don't believe most conspiracy theories. But I acknowledge that some have proven to be true.

All I want are answers to these questions...

1) If jet fuel burns at about 1800 degrees F, and steel melts at about 2700 degrees F, why did the Twin Towers collapse?

2) Why did 7 World Trade Center collapse as effficiently as the Twin Towers, as if by demolition, without even being hit by a jet?

3) If the black boxes of the jets didn't survive the explosion, why did the passport of one of the supposed terrorists survive?

4) Why are some of the supposed terrorists of the hijackings still alive and well?

5) Why hasn't Osama Bin Laden been cought?

6) In the video presented to the public where Osama admits his part in the attack, why is he wearing a ring and a watch, which is against Islamic rule?

Please answer these questions, so I can go back to being an American who believes his government is doing the right thing. So I can get back to my life of playing video games, ignoring the daily news, and eating McDonalds. Or not.

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Originally posted by dreamtrove:
Almost certainly, the towers were leveled by a controlled demolition...

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Originally posted by SergeantX:
Tell this much, what is the presumed point of what you suggest? Why go to the trouble of making sure the buildings are comletely destroyed? As though hitting them with jetliners isn't enough?

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...no way they couldn't build an impervious building.

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Originally posted by dreamtrove:
Reaverman, if you think it's aliens, fine.

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