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Baseline Structural Performance and Aircraft Impact Damage Analysis of the World Trade Center Towers. Federal Building and Fire Safety Investigation of the World Trade Center Disaster (NIST NCSTAR 1-2) ***DRAFT for Public Comments***



Fahim Sadek


The baseline structural performance and aircraft impact damage analysis of the National Institute of Standards and Technology (NIST) Investigation of the World Trade Center (WTC) disaster had two primary tasks: (1) to develop reference structural models of the WTC towers and use these models to establish the baseline performance of each of the towers under gravity and wind loads, and (2) to estimate the damage to the towers due to aircraft impacts and establish the initial conditions for the fire dynamics modeling and the thermal-structural response and collapse initiation analysis. This report provides the technical approach. methodology, and results related to both tasks. For the first task, the baseline performance of the WTC towers under gravity and wind loads was established in order to assess the towers' ability to withstand those loads safely and to evaluate the reserve capacity of the towers to withstand unanticipated events. The baseline performance study provides a measure of the behavior of the towers under design loading conditions, specifically: (1) total and inter-story drift (the sway of the building under design wind loads). (2) floor deflections under gravity loads, (3) the stress demand-to-capacity ratio for primary structural components of the towers such as exterior walls, core columns, and floor framing, (4) performance of exterior walls under wind loading, including distribution of axial stresses and presence of tensile forces, (5) performance of connections between exterior columns, and (6) resistance of the towers to shear sliding and overturning at the foundation level.
National Construction Safety Team Act Reports (NIST NCSTAR) - 1-2
Report Number


World Trade Center, high rise buildings, building collapse, disasters, terrorists, terrorism, aircraft impact, damage, floors, wind effects, wind velocity, impact, gravity, fire dynamics, methodology, fire safety, fire investigations, wind tunnels
Created September 1, 2005, Updated February 19, 2017