Review of Literature Regarding Progressive Collapse of WTC Twin Towers – A Call for Re-evaluation (Updated Version 2)

Since the tragic events of September 11^th, 2001, the official view endorsed by the National Institute of Standards and Technology is that the Twin Towers of the WTC complex suffered a “progressive collapse,” wherein the upper sections crushed the lower floors as they pancaked all the way to the ground. This general scenario has become the de facto explanation for the collapse of the Towers, supported by the majority of the engineering community. However, a review of relevant literature on the collapses casts significant doubt on this scenario, showing that a progressive collapse model would have resulted in a longer time to collapse, or perhaps a collapse that would not have progressed at all. As such, re-evaluation of the collapses and development of other, more plausible models is needed.