Feng Xiao (Associate Professor, Nanjing University of Science and Technology) and Zhili Quan (Bridge Engineer, South Carolina Department of Transportation) summarizing their expert report on the WTC Building 7 collapse (2020): “This is a study of the collapse of World Trade Center Building 7 (WTC 7) — a 47-story building that suffered a total collapse at 5:20 PM on September 11, 2001, following the horrible events of that morning. The objective of the study was threefold: (1) Examine the structural response of WTC 7 to fire loads that may have occurred on September 11, 2001; (2) Rule out scenarios that could not have caused the observed collapse; and (3) Identify types of failures and their locations that may have caused the total collapse to occur as observed. The UAF research team utilized three approaches for examining the structural response of WTC 7 to the conditions that may have occurred on September 11, 2001. First, we simulated the local structural response to fire loading that may have occurred below Floor 13, where most of the fires in WTC 7 are reported to have occurred. Second, we supplemented our own simulation by examining the collapse initiation hypothesis developed by the National Institute of Standards and Technology (NIST). Third, we simulated a number of scenarios within the overall structural system in order to determine what types of local failures and their locations may have caused the total collapse to occur as observed. The principal conclusion of our study is that fire did not cause the collapse of WTC 7 on 9/11, contrary to the conclusions of NIST and private engineering firms that studied the collapse. The secondary conclusion of our study is that the collapse of WTC 7 was a global failure involving the near-simultaneous failure of every column in the building” (Feng Xiao and Zhili Quan, “A structural reevaluation of the collapse of World Trade Center 7”, Institute of Northern Engineering, University of Alaska Fairbanks, March 2020: http://ine.uaf.edu/wtc7 ).
Dr. Leroy Hulsey, Dr. Zhili Quan, and Professor Feng Xiao (Institute of Northern Engineering, University of Alaska Fairbanks) in their detailed Final Report into “A structural reevaluation of the collapse of World Trade Center 7”(2020): “EXECUTIVE SUMMARY. This report presents the findings and conclusions of a four-year study of the collapse of World Trade Center Building 7 (WTC 7)—a 47-story building that suffered a total collapseat 5:20 PM on September 11, 2001, following the horrible events of that morning. Figure E.1 shows the layout of WTC7 in relation to the World Trade Center complex prior to September 11, 2001.Figure E.2 showsthe structural layout of Floor 13.Figure E.3 shows the finite element model of WTC 7. This study was conducted by a three-person team of researchers at the University of Alaska Fairbanks (UAF) Department of Civil and Environmental Engineering with funding provided by Architects & Engineers for 9/11 Truth, Inc., a 501(c)(3) nonprofit organization whose purpose is to conduct research and educate the public about the World Trade Center building collapses on 9/11.According to the National Institute of Standards and Technology(NIST)—an agency of the U.S. Department of Commerce that investigated the three building failures on 9/11—the collapse of WTC 7 was the first known instance of the total collapse of a tall building primarily due to fires. However, many independent researchers have studied the collapse of WTC 7and assembled a body of evidence that raises questions about the validity of NIST’s conclusions. The objective of this study, therefore, was threefold: (1) Examine the structural response of WTC 7 to fire loads that may have occurred on September 11,2001; (2)Rule out scenarios that could not have caused the observed collapse; and (3)Identify types of failures and their locations that may have caused the total collapse to occur as observed… It is our conclusion based upon these findings that the collapse of WTC 7 was a global failure involving the near-simultaneous failure of all columns in the building and not a progressive collapse involving the sequential failure of columns throughout the building” (Dr. J. Leroy Hulsey, Dr. Zhili Quan, and Professor Feng Xiao (Institute of Northern Engineering, University of Alaska Fairbanks) , Final Report. “A structural reevaluation of the collapse of World Trade Center 7”, March 2020: https://files.wtc7report.org/file/public-download/A-Structural-Reevaluation-of-the-Collapse-of-World-Trade-Center-7-March2020.pdf ).