WHAT INITIATED COLLAPSES IN NEW YORK ON SEPTEMBER 11, 2001?

A new, more sophisticated analysis of the WTC collapse called the hybrid theory is advanced below that uses both fracture waves and progressive failure. According to the hybrid theory the collapses of World Trade Center towers ran in two phases: (i) in the first phase dynamic fracture waves disintegrated a considerable part of the towers producing the dust cloud and explosion sound well-documented and well-evidenced, and (ii) in the second phase the progressive failure front disintegrated the lower part of the towers that remained intact in the first phase. To illustrate many possible modes of progressive failure the slowest mode, the fastest mode, and three intermediate modes were first studied and then the hybrid mode was introduced. The hybrid theory allows one to get rid of evident defects of earlier theories and explain all basic facts and observations of the matter not understood before, in particular, why the time of all collapses was free fall time independent of the position of critical floor the collapses started from. It was shown that the floors disintegrated in the very beginning of the collapses were located considerably lower than the floors hit by terrorists and subjected to fire. From here, it follows that fracture waves were produced by explosives and not arisen from thermal stresses of fire as suggested earlier. The second author did all numerical work and is not responsible for the rest of the paper written by the first author.

• Cherepanov G.P.
• Esparragoza I.E.

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