By Jackie Craven, About.com Guide
Seven hours after the World Trade Center twin towers fell, the 47-story WTC building 7 collapsed
Photo © Pool / Getty ImagesAfter years of investigations, the National Institute of Standards and Technology (NIST) found that the intense heat on the floor beams and girders weakened a critical support column in WTC Building 7.
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September 11, 2001:
Destruction, Reconstruction, and Monuments
World Trade Center ArchitectureWhy the Twin Towers FellHistory of the World Trade Center
Before the AttackAfter the AttackSeptember 11 Digital Archive
9-11 CommissionNIST World Trade Center Investigation FEMA World Trade Center Building Performance Study
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