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Final Report of the National Construction Safety Team on the Collapses of the World Trade Center Towers. Federal Building and Fire Safety Investigations of the World Trade Center Disaster (NIST NCSTAR 1) ***DRAFT for Public Comments***



Sivaraj Shyam-Sunder, Richard G. Gann, William L. Grosshandler, Hai S. Lew, Richard W. Bukowski, Fahim Sadek, Frank W. Gayle, Therese P. McAllister, Jason D. Averill, James R. Lawson, Harold E. Nelson, Stephen A. Cauffman


This is the final report on the National Institute of Standards and Technology (NIST) econstruction of the collapses of the World Trade Center (WTC) towers, the results of an investigation conducted under the National Construction Safety Team Act. This reports describes how the aircraft impacts and subsequent fires led to the collapses of the towers after terrorists flew jet fuel laden commercial airliners into the buildings; whether the fatalities were low or high, including an evaluation of the building evacuation and emergency response procedures; what procedures and practices were used in the design, construction, operation, and maintenance of the towers; and areas in current building and fire codes, standards, and practices that warrant revision. Extensive details are to be found in the 42 companion reports. The final report on the collapse of WTC 7 appears in a separate report. Also in this report is a description of how NIST reached its conclusions. This included the complementing of in-house expertise with private sector technical experts; the accumulation of copious documents, photographs, and videos of the disaster; the establishment of the baseline performance of the WTC towers; the computer simulation of the behavior of each tower on September 11, 2001; the combination of the knowledge gained into a probable collapse sequence for each tower; the conduct of nearly 1,200 first-person interviews of building occupants and emergency responders; analysis of the evacuation and emergency response operations in the two high-rise buildings; and the compilation of principal findings. The report concludes with a list of 30 recommendations for action in the areas of increased structural integrity, enhanced fire resistance of structures, new methods for fire resistance design of structures, enhanced active fire protection, improved building evacuation, improved emergency response, improved procedures and practices, and continuing education and training.
National Construction Safety Team Act Reports (NIST NCSTAR) - 1
Report Number


World Trade Center, aircraft impact, building evacuation, emergency response, fire safety, human behavior, structural collapse, tall buildings, wind engineering
Created September 1, 2005, Updated December 19, 2018