Failure Analysis of the WTC
Tuesday, December 18th, 2001 Catastrophe PropertyNo shortage of commentary existed after the attacks on the World Trade Center, which resulted in the collapse of the two-towered structure. There was surprise among technologists and non-technologists alike as to the degree of structural failure brought on by the event. Never has such a large building collapsed with such a devastating loss of life. Who could have credibly advanced a scenario of a direct impact from a jumbo jet and the ensuing petroleum-fueled fire? A review of the design concept and construction of the building helps explain the failure’s origin and sequence. Figure 1 is a simplified drawing of one of the tower structures. A central core housed elevators and supported the weight of the floors. Around the outside of the building were closely spaced (39-inch centers) perimeter columns that were designed to resist lateral wind loads and support the outer edge of each floor.
