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Structural Analysis of Impact Damage to World Trade Center Buildings 1, 2, and 7



Therese P. McAllister, Fahim Sadek, John L. Gross, Steven W. Kirkpatrick, Robert S. MacNeill, R. Bocchieri, Mehdi S. Zarghamee, Omer O. Erbay, Andrew T. Sarawit


The National Institute of Standards and Technology (NIST) conducted an extensive investigation of the collapse of World Trade Center towers (WTC 1 and WTC 2) and the WTC 7 building. This paper describes the reconstruction of impact damage to each of the WTC buildings, as well as analytical studies related to the WTC building collapses. In addition, data and evidence that were collected, tests of the floor truss systems in the WTC towers that were conducted, the overall structural analysis approach, and the development of the collapse hypotheses are discussed to provide a basis for the impact analyses and the fire and structural response analyses in a companion paper. Three companion papers address the primary structural systems of the WTC towers and WTC 7, the effects of fire on the three buildings, and how these events contributed to building collapse. The papers provide an overview of the complex and extensive investigations undertaken by NIST at a level of detail that has scientific merit but presents key aspects from the voluminous official reports at a level suitable for the technical literature.
Fire Technology


World Trade Center, Structural fire effects, Impact damage, Structural analysis, Failure analysis, Global collapse


McAllister, T. , Sadek, F. , Gross, J. , Kirkpatrick, S. , MacNeill, R. , Bocchieri, R. , Zarghamee, M. , Erbay, O. and Sarawit, A. (2012), Structural Analysis of Impact Damage to World Trade Center Buildings 1, 2, and 7, Fire Technology, [online], (Accessed July 22, 2024)


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Created August 12, 2012, Updated November 10, 2018