Progressive Collapse of Towers: The Resistance Effect

In the recent paper (Cherepanov, 2006), objections were raised against the widely accepted version of the WTC collapse and an alternative calculation was presented. The present work uses the model advanced in the mentioned paper and incorporates the effect of non-zero resistance that slows down the progressive collapse. The analysis shows that the collapses of twin towers started from a floor located significantly lower than the floors hit by terrorists.