The objective of this report was to analyze the aircraft impacts into each of the World Trade Center (WTC) towers to provide the following: (1) estimates of probable damage to structural systems due to aircraft impact, including exterior walls, floor systems, and interior core columns; (2) estimates of the aircraft fuel dispersal during the impact; (3) estimates of debris damage to the interior tower contents, including partitions and workstations. Thus, this analysis established the initial conditions for the fire dynamics modeling and the thermal-structural response and collapse initiation analysis. The impact analyses were conducted at various levels of complexity including: (1) the component level, (2) the subassembly level, and (3) the global level to estimate the probable damage to the towers due to aircraft impact. Simplified analyses were also used to support the development of the global finite element models. Analysis of uncertainties using the component and subassembly analyses were conducted to assess the effects of variability associated with various input parameters and identify the most influential parameters that affect the damage estimates using orthogonal factorial design. Based on the results of the sensitivity analyses, the most influential parameters identified were varied in the global models to provide a range of damage estimates for WTC 1 and WTC 2. As part of the tower and aircraft models, constitutive relationships describing the actual behavior of the structures under the dynamic impact conditions of the aircraft were developed based on test results of the tower steels and from the open literature for other materials. Various grades of steels used in the exterior walls and core columns of the towers, weldment metal, bolts, reinforced concrete, aircraft materials, and nonstructural contents were considered. The constitutive relationships included high strain-rate effects and failure criteria for the various materials.
Citation: National Construction Safety Team Act Reports (NIST NCSTAR) - 1-2
NIST Pub Series: National Construction Safety Team Act Reports (NIST NCSTAR)
Pub Type: NIST PubsReport Number:
World Trade Center, high rise buildings, building collapse, disasters, fire safety, fire investigations, terrorists, terrorism, aircraft impact, impact, failure, aircraft fuels, dispersons, structural dynamics, uncertainty, damage, structural damage