Was the september 2001 destruction of the World Trade Centres caused by fire or controlled demolition?

Answer 1

The fire. There was NO demolition charge. Those who claim there were don't know anything, and are just looking for more excuses to support some crazy conspiration theory.
A controlled demolition would have had the charges at the base of the building, not at the *exact* height the airplane hit (which was impossible to control accurately).

Answer 2

I think it's all to up in the air to really give you a clear concise answer. As always, there are conflicting statements on both sides. Looking at it from an engineer's standpoint, the fire was said to have reach 2000 deg. Fahrenheit. An engineer knows that steel weakens significantly at this temperature. Steel melts at approx. 3000 deg. F. Supposedly thermite was said to be found which is used to break down steel. Whether this is true or not, i have no idea. It's all just speculation. The yield strength of 1080 steel which is high grade carbon steel (i'm not sure what kind was used in the construction of the towers) is about 55,000 PSI. I'm not sure exactly what the yield strength of the steel is at 2000 degrees but it is probably less than half that. So depending up on what the safety factor of the steel I-beams were when it was designed, the temperature could have been enough to make it bend and once it bent, it would only get worse as it weakened more. You can see that on tower 2, the one that got hit second, the building collapsed a lot quicker because it was struck lower. This is because this much more weight on top of it. I would say the jet fuel, which there was probably hundreds or thousands of gallons of jet fuel since the planes only took off in like boston with a full tank, burned hot enough to collapse. Jet fuel is extremely flammable. I think looking at the facts, it was caused by a fire. I think a controlled demolition is too far out of the question and the media would be all over it. You never know and thats the thing, we all will probably never know the whole entire truth about what happened with 9/11 and thats how it is with pretty much anything.

Answer 3

Fire
The steel structure was designed to survive a fire one hour. Because of the jet fuel and impact it only lasted 45 minutes.

As the building started to collapse, air pressure blew out the lower floor windows which loooked like demolition explosions but it wasn't.

Answer 4

Answer to question is below in excerpt from website below under Source(s).

"It appears likely that the impact of the plane crash destroyed a significant number of perimeter columns on several floors of the building, severely weakening the entire system. Initially this was not enough to cause collapse.

However, as fire raged in the upper floors, the heat would have been gradually affecting the behaviour of the remaining material. As the planes had only recently taken off, the fire would have been initially fuelled by large volumes of jet fuel, which then ignited any combustible material in the building. While the fire would not have been hot enough to melt any of the steel, the strength of the steel drops markedly with prolonged exposure to fire, while the elastic modulus of the steel reduces (stiffness drops), increasing deflections.

Modern structures are designed to resist fire for a specific length of time. Safety features such as fire retarding materials and sprinkler systems help to contain fires, help extinguish flames, or prevent steel from being exposed to excessively high temperatures. This gives occupants time to escape and allow fire fighters to extinguish blazes, before the building is catastrophically damaged.

It is possible that the blaze, started by jet fuel and then engulfing the contents of the offices, in a highly confined area, generated fire conditions significantly more severe than those anticipated in a typical office fire. These conditions may have overcome the building's fire defences considerably faster than expected. It is likely that the water pipes that supplied the fire sprinklers were severed by the plane impact, and much of the fire protective material, designed to stop the steel from being heated and losing strength, was blown off by the blast at impact.

Eventually, the loss of strength and stiffness of the materials resulting from the fire, combined with the initial impact damage, would have caused a failure of the truss system supporting a floor, or the remaining perimeter columns, or even the internal core, or some combination. Failure of the flooring system would have subsequently allowed the perimeter columns to buckle outwards. Regardless of which of these possibilities actually occurred, it would have resulted in the complete collapse of at least one complete storey at the level of impact.

Once one storey collapsed all floors above would have begun to fall. The huge mass of falling structure would gain momentum, crushing the structurally intact floors below, resulting in catastrophic failure of the entire structure. While the columns at say level 50 were designed to carry the static load of 50 floors above, once one floor collapsed and the floors above started to fall, the dynamic load of 50 storeys above is very much greater, and the columns were almost instantly destroyed as each floor progressively "pancaked" to the ground."

Answer 5

damn conspiracy. no missile hit the pentagon. bush didnt order a demolition team to blow up the WTC. for you to sit there and say the united states played a part in 9/11, your are absolutely insane. That was the worst day in modern US history. Yes, i do beleive the US had prior knowledge of the attack. but if Bush would have attacked al-quada would you have supported him? Bush would get the same support he has gotten for Iraq. which is none

Answer 6

Fire, of course. There are still some morons around who claim otherwise (we see them in this forum), but they are too stupid to understand the facts. Anyone who has ever watched a blacksmith adjusting a horseshoe knows that steel loses strength at a temperature far lower than its melting point.

Answer 7

Unprotected or insulation stripped or damaged structural steel looses 50% (half) of its strength at approximately 1100 degrees F.

And that's a valid and verifiable FACT.

End of discussion.

Answer 8

Airplanes