By Timothy E. Eastman, Ph.D. (Geophysics), and Jonathan H. Cole, P.E.
Journal of 9/11 Studies Volume 37,
April 2013


The importance of understanding the mechanisms of collapse for the three World Trade
Center buildings on September 11, 2001 cannot be over-estimated, for these unusual
collapses and their disputed causes raise questions regarding all future steel-frame building
design. A literature review was conducted to identify the evolving trend in research results
in this area, which have become increasingly diverse over time. Recommendations for
further research are presented.


Over the past decade there have emerged two primary hypotheses regarding the mechanism of destruction for World Trade Center (WTC) buildings 1, 2 and 7, namely, the official fire-induced Progressive Collapse (PC) versus the alternate Controlled Demolition (CD). The question of which of these two hypotheses is correct is singularly important because its current lack of resolution leaves unmet the following critical needs (assuming PC):

(1) Thousands of other structures may also be subject to such catastrophic destruction by
office fires, and inspections and upgrades based on determination of what caused the
WTC buildings to collapse may be needed to ensure public safety;

(2) Significant structural design analysis tools and computer models need upgrades
to account for the potential of such catastrophic destruction;

(3) major revisions to building codes for high-rise steel-frame buildings are critically needed
(Bement, 2002).

Our goals here are to fully document the available peer-reviewed literature on this important
question, and to promote more open and in-depth research by a broader community of scholars.

Although much relevant evidence from portions of the events of 9/11 remains unavailable to
researchers as well as the general public, substantial evidence is available concerning the
destruction of WTC 1, 2 and 7 that is relevant to resolving the key question of PC versus CD.
Nevertheless, the diversity and complexity of the 9/11 events make it very difficult for most
citizens, and even many researchers, to obtain the quality information needed to address and
resolve the above questions. In particular, information provided officially is notoriously
incomplete; e.g., the official 9/11 Commission Report (2004) makes no mention of destruction of the third high-rise steel-frame building, WTC 7. Further, relevant official reports produced by the National Institute of Standards and Technology (NIST) for the Twin Towers are incomplete in that Journal of 9/11 Studies Volume 37, April 2013 they stopped their efforts at “collapse initiation” and could not explain total destruction. Finally, the same NIST reports have been surrounded by controversy that remains mostly unreported in mainstream media sources (see peer-reviewed papers referenced herein).

This controversy has been fueled in part because official investigations and reports on this topic have been very tightly controlled and not peer-reviewed.i Basic documentation of such work has not been made available to independent researchers in spite of repeated Freedom-of-Information-Act (FOIA) requests; e.g., most of the detailed documentation, coding, methodology and assumptions employed by NIST in their finite element analysis model of WTC 7. Related to these technical impediments to independent research, in addition to essentially no funding for such research, the “conspiracy theorist” or “truther” label has often been used to discourage or truncate debate on many critical questions, leaving the official theory as the default. For the most part, and somewhat understandably, the science and engineering professional communities have stayed on the sidelines, perhaps in part to protect their reputations and in part to avoid putting their federal research grants at risk. This condition of obstructed research continues in spite of the fact that a “conspiracy” by definition is “an agreement between two or more persons to commit a crime.”

Thus, by definition, both the official PC hypothesis and the alternative CD hypothesis addressed here are necessarily associated with a conspiracy theory of one form or another. Setting such labels aside, the fundamental question remains, “which hypothesis is best supported by the evidence?” Unfortunately, this basic question and its resolution have been systematically subverted for the past decade.

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