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Compiled by Gary Galluzzo
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Iowa City IA 52242
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Release: Sept. 18, 2001

UI civil and environmental engineering professor Wilfrid Nixon responds to the question: How will the destruction of the World Trade Center likely affect future skyscraper engineering design for strength and fire safety?

The two towers of the World Trade Center actually withstood the attack from a structural point of view very well, notwithstanding their eventual collapse. It is of note that in the North Tower (the one struck first) the elevators from the 78th floor continued to operate until the building collapsed. The buildings collapsed because of the intense fire caused by the burning jet fuel, which gave rise to temperatures estimated at 2000 Fahrenheit. This caused the steel core of the building to weaken (and perhaps melt) leading to a buckling failure and the characteristic "pancake" collapse seen in both towers. It is unlikely that there will be major code changes for strength, but it is possible that there may be some strengthening of the fire standards. If such does occur, the goal will not be to avoid a building collapse (this would be prohibitively expensive) but to allow more time for building evacuation.

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