TWO VERSIONS OF WTC COLLAPSE

There are two basic versions of the collapses of the World Trade Center towers in New York on September 11, 2001. According to the official version of National Institute of Standards that studied the collapses on an assignment of the President and government of the United States, all collapses represented the progressive collapse by floor-by-floor failure started from a critical floor, which was assumed to be the floor hit by terrorists and subjected to fire. According to the other version widely-spread in the United States, MASAD agents mined a floor below those under fire, and detonated explosives in a while after the crushes. In the present paper, the official version of U.S. government is assumed valid, and the critical floor where the collapses started from is calculated based on: (i) the governing equations of progressive collapse formulated by Cherepanov in Int. J. Fracture (2006),141:287-289 and(ii) the well-documented fact of free fall time of all collapses. It is proven that all collapses started from a floor located significantly lower than those hit by terrorists and subjected to fire.

• Cherepanov GenadyP.
• Ivan E.

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