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Remember that the Trade towers were built differently to most buildings, they were essentially two boxes connected by the floors.
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As the floors collapsed the actual forces on the steel supports increased (doubling the effective length of the support between crossbraces)... the more floors lost => greater chance of falling.
The Empire State building and the Madrid one are build more traditionally... Steel boxes stacked on each other rather than two boxes with a suspended floor...
Basically the towers were designed well... the actual plane impact was expected however the impact blew off a lot of the fire proofing and the fuel just burned down the place, it was a more susceptible building than traditional cosntruction though had benefits in other areas.
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