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| THE COLLAPSE |
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| "Terrorist attacks can shake the foundations of our biggest buildings, but they cannot touch the foundation of America." |
| - President Bush |
| Just over an hour after the South Tower was hit by the jet, every ones worst nightmare came true. After an hour of intense fires and pandemonium around the two towers, the South Tower collapsed. Hundreds of fire firefighters, police officers, and rescue personal were killed when the tower collapsed on them as they tried to rescue the victims still trapped inside the towers. Only 12 minutes after the South Tower collapsed, the North Tower collapsed as well, destroying everything and every one in its path. The two towers that once stood as great monuments were now large heaps of concrete and twisted steel. Hours later, fire caused another building, 7 World Trade Center, to collapse. It had been burning since shortly after the planes stuck the Twin Towers. Other nearby buildings also caught fire and collapsed in the following hours after the attacks. |
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| For more pictures on the collapse, click HERE to visit the picture gallery. You can also access the picture gallery on the index bar under the section titled "Sept 11, 02" |
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| Click on picture for full size version |
| The structural integrity of the World Trade Center depends on the closely spaced columns around the perimeter. Lightweight steel trusses span between the central elevator core and the perimeter columns on each floor. These trusses support the concrete slab of each floor and tie the perimeter columns to the core, preventing the columns from buckling outwards. The impact of the plane 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 the collapse of the two Towers. However, as the fire raged in the upper floors, the heat began to gradually affect the behaviour of the remaining material. As the planes had only recently taken off before impact, the fire would have been fuelled by large volumes of jet fuel, creating enormously high temperatures. The strength of the steel would have dropped as it was exposed to the high temperature fire. |
| A perimeter of closely spaced columns, with an internal lift core. The floors were supported by a series of light trusses on rubber pads, which spanned between the outer columns and the lift core. |
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| Why The Towers Fell |
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| Once one story collapsed all the floors above began to fall. The huge mass of the falling structure gained momentum, crushing the structurally intact floors below, resulting in catastrophic failure of the entire structure. The only evidence so far is photographs and television footage. Whether failure occurred in the perimeter columns or in the core is unknown. The extent to which the internal parts were damaged during the collision may be evident in the rubble if any forensic investigation is conducted. Since the mass of the combined towers is close to 1,000,000 tons, finding evidence will be an enormous task. |
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| Eventually, the loss of strength and stiffness of the steel, combined with the initial impact damage, caused a failure of the truss system supporting a floor, the remaining perimeter columns, and the internal core. The failure of the flooring system allowed the perimeter columns to buckle outwards. This failure resulted in the complete collapse of at least one complete story at the level of impact. |
| A giant dust cloud generated by the collapse of the towers. |
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| The underground levels at the World Trade Center. |
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| Click on picture for full size version |
| Click on picture for full size version |
| Click on picture for full size version |
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| This site is owned and operated by Tyler Bjarnason. This site is for entertainment and informational purposes only. Even though this site may contain links to World Trade Center and other related organizations, it is in no part related with any World Trade Center, Red Cross, or other kinds of related charity or organization. All graphics, borders, titles property of Tyler Bjarnason. Please e-mail me before using any material off of this site. If you have any questions please e-mail me A.S.A.P. © Tyler Bjarnason 2002 All pictures on this site with copy right laws are used with permission. Copy right pictures ©2001 Sara K. Schwittek. All rights reserved |
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