How did the World Trade Center collapse?

I am curious what you know about how the modus of elasticity of steel changes when it is heated.

Fires Versus Steel Buildings

The official explanation that fires caused the collapse of Building 7 is incredible in light of the fact that fires have never caused a steel-framed building to totally collapse, before or after September 11th, 2001.

Steel-framed high-rises (buildings of fifteen stories or more) have been common for more than 100 years. There have been hundreds of incidents involving severe fires in such buildings, and none have led to complete collapse, or even partial collapse of support columns.

Recent examples of high-rise fires include the 1991 One Meridian Plaza fire in Philadelphia, which raged for 18 hours and gutted 8 floors of the 38-floor building; 1 and the 1988 First Interstate Bank Building fire in Los Angeles, which burned out of control for 3-1/2 hours and gutted 4 floors of the 64 floor tower. Both of these fires were far more severe than any fires seen in Building 7, but those buildings did not collapse. The Los Angeles fire was described as producing "no damage to the main structural members". 2

Research indicates that even if a steel-framed building were subjected to an impossible superfire, hundreds of degrees hotter and far more extensive then any fire ever observed in a real building, it would still not collapse. Appendix A of The World Trade Center Building Performance Study contains the following:

In the mid-1990s British Steel and the Building Research Establishment performed a series of six experiments at Cardington to investigate the behavior of steel-framed buildings. These experiments were conducted in a simulated, eight-story building. Secondary steel beams were not protected. Despite the temperature of the steel beams reaching 800-900 C (1,500-1,700 F) in three of the tests (well above the traditionally assumed critical temperature of 600 C (1,100 F), no collapse was observed in any of the six experiments).

In building fires outside of such laboratory experiments, steel beams and columns probably never exceed 500º C. In extensive fire tests of steel frame carparks conducted by Corus Construction in several countries, measured temperatures of the steel columns and beams, including in uninsulated structures, never exceeded 360ºC. 3

http://www.wtc7.net/buildingfires.html

I read it. Took all of 5 minutes. Very interesting and he answers the question in a very succinct manner. It's the same thing all the experts have been saying for the past 9 years.
But I suggest you continue to ignore the facts and continue to believe the idiot conspiracy theories. This world is a more interesting place with people who proudly acknowledge their own ignorance.

And what size plane hit that building?

THE WTC WAS DESIGNED TO SURVIVE
THE IMPACT OF A BOEING 767

Fact. The twin towers were designed to withstand a collision with a Boeing 707.

The maximum takeoff weight for a Boeing 707-320B is 336,000 pounds.
The maximum takeoff weight for a Boeing 767-200ER is 395,000 pounds.

The wingspan of a Boeing 707 is 146 feet.
The wingspan of a Boeing 767 is 156 feet.

The length of a Boeing 707 is 153 feet.
The length of a Boeing 767 is 159 feet.

The Boeing 707 could carry 23,000 gallons of fuel.
The Boeing 767 could carry 23,980 gallons of fuel.

The cruise speed of a Boeing 707 is 607 mph = 890 ft/s,
The cruise speed of a Boeing 767 is 530 mph = 777 ft/s.

So, the Boeing 707 and 767 are very similar aircraft, with the main differences being that the 767 is slightly heavier and the 707 is faster.

In designing the towers to withstand the impact of a Boeing 707, the designers would have assumed that the aircraft was operated normally. So they would have assumed that the aircraft was traveling at its cruise speed and not at the break neck speed of some kamikaze. With this in mind, we can calculate the energy that the plane would impart to the towers in any accidental collision.

The kinetic energy released by the impact of a Boeing 707 at cruise speed is
= 0.5 x 336,000 x (890)^2/32.174
= 4.136 billion ft lbs force (5,607,720 Kilojoules).

The kinetic energy released by the impact of a Boeing 767 at cruise speed is
= 0.5 x 395,000 x (777)^2/32.174
= 3.706 billion ft lbs force (5,024,650 Kilojoules).

From this, we see that under normal flying conditions, a Boeing 707 would smash into the WTC with about 10 percent more energy than would the slightly heavier Boeing 767. That is, under normal flying conditions, a Boeing 707 would do more damage than a Boeing 767.

In conclusion we can say that if the towers were designed to survive the impact of a Boeing 707, then they were necessarily designed to survive the impact of a Boeing 767.

So what can be said about the actual impacts?

The speed of impact of AA Flight 11 was 470 mph = 689 ft/s.
The speed of impact of UA Flight 175 was 590 mph = 865 ft/s.

The kinetic energy released by the impact of AA Flight 11 was
= 0.5 x 395,000 x (689)^2/32.174
= 2.914 billion ft lbs force (3,950,950 Kilojoules).

This is well within limits that the towers were built to survive. So why did the North tower fall?

The kinetic energy released by the impact of UA Flight 175 was
= 0.5 x 395,000 x (865)^2/32.174
= 4.593 billion ft lbs force (6,227,270 Kilojoules).

This is within 10 percent of the energy released by the impact of a Boeing 707 at cruise speed. So, it is also a surprise that the 767 impact caused the South tower to fall.

Overall, it comes as a great surprise that the impact of a Boeing 767 bought down either tower. Indeed, many experts are on record as saying that the towers would survive the impact of the larger and faster Boeing 747. In this regard, see professor Astaneh-Asl's simulation of the crash of the much, much larger and heavier Boeing 747 with the World Trade Center. Professor Astaneh-Asl teaches at the University of California, Berkeley.

Although the jet fuel fires have been ruled out as the cause of the collapses, it should still be pointed out that the fuel capacities of the Boeing 707 and the Boeing 767 are essentially the same. And in any case, it has been estimated that both UA Flight 175 and AA Flight 11 were carrying about 10,000 gallons of fuel when they impacted. This is well below the 23,000 gallon capacity of a Boeing 707 or 767. Thus the amount of fuel that exploded and burnt on September 11 was envisaged by those who designed the towers. Consequently, the towers were designed to survive such fires. It should also be mentioned that other high-rise buildings have suffered significantly more serious fires than those of the twin towers on September 11, and did not collapse.

http://www.serendipity.li/wot/wtc_demolition_init.htm

I read it. Took all of 5 minutes.

correction: history of the masses not "history of the messes"

Ok Amigo, tell me what really happened.
This should be entertaining...

How's about you explain it then.

Steel-framed high-rises (buildings of fifteen stories or more) have been common for more than 100 years. There have been hundreds of incidents involving severe fires in such buildings, and none have led to complete collapse, or even partial collapse of support columns.

In the mid-1990s British Steel and the Building Research Establishment performed a series of six experiments at Cardington to investigate the behavior of steel-framed buildings.

The other interesting thing about the tests performed in the mid 1990s is the fire burned for less than 20 minutes in each test.

Meanwhile the fire burned for hours in WTC 7.

That is like arguing that I can't cook turkey in an oven at 300 degrees for 4 hours because you did a test for 5 minutes and it didn't cook.

The WTC7 did NOT collapse from a controlled explosion. The amount of explosives required would have created a rather loud sound that is not evident in any recordings. Unless you want to argue that someone developed "silent" explosives it couldn't have been explosive charges that brought it down. (Silent explosives would most likely be useless. Explosives work by expanding rapidly which would move air creating sound.)

WTC7 was damaged by the towers collapsing next to it and then had a fire that burned for hours including a rather large amount of diesel fuel which most likely weakened the center support beam causing it to collapse. There really is no other possible explanation based on the known facts.