Sunday, April 5, 2009
Why did World Trade Center fall?The impact of the plane crash destroyed some of the load-bearing columns and inflicted other structural damage in both towers. The resulting explosions ignited 10,000 US gallons (38,000 l) of jet fuel. The light construction and hollow nature of the buildings allowed the fuel to penetrate far inside the towers igniting large fires simultaneously. The fires were hot enough to weaken the steel columns and cause floors to sag, pulling perimeter columns inward and reducing their ability to support the mass of the building above.
source: Wikipedia
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