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Damage and Failure Modes of Structural Steel Components. Federal Building and Fire Safety Investigation of the World Trade Center Disaster (NIST NCSTAR 1-3C) ***DRAFT for Public Comments***



Stephen W. Banovic, Timothy J. Foecke


This report describes damage characteristics, failure modes, and fire-related degradation of the recovered structural components from the World Trade Center (WTC) 1 and WTC 2. Assessment of the structural components was divided into pre- and post-collapse analysis. Pre-collapse analysis concentrated on impact damage sustained by the exterior panel sections, with assessment based solely upon photographic and video images. These images were also used to locate areas on the recovered and identified (i.e., known as-built location) panels with pre-collapse fire exposure. The second portion of the analysis focused on direct visual examination of the recovered steel elements. Of particular importance were the samples located near the airplane impacts (north face of WTC 1 and south face of WTC 2) and those where fire was known to exist prior to collapse of the buildings. Metallographic analysis of components with specific or unique damage patterns: was also conducted. The findings of this report were used for validation of the modeling efforts in the baseline structural performance and aircraft impact damage analysis, the reconstruction of the thermal environment, and the structural fire response and collapse analysis. WTC 7 steel was not evaluated in this study of the tower damage and failure modes.
National Construction Safety Team Act Reports (NIST NCSTAR) - 1-3
Report Number


World Trade Center, high rise buildings, building collapse, disasters, fire safety, fire investigations, terrorists, terrorism, steel structures, damage, failure analysis, failure models, steels, degradation, wall panels, columns, floors, structural elements
Created September 1, 2005, Updated February 19, 2017