Analysis of Aircraft Impacts into the World Trade Center Towers Chapters 1, 2, 3, 4, 5, 6, 7 and 8. Federal Building and Fire Safety Investigation of the World Trade Center Disaster.
Analysis of Aircraft Impacts into the World Trade Center
Towers Chapters 1, 2, 3, 4, 5, 6, 7 and 8. Federal
Building and Fire Safety Investigation of the World
Trade Center Disaster.
(36044 K)
Kirkpatrick, S. W.; Bocchieri, R. T.; Sadek, F.;
MacNeill, R. A.; Holmes, S.; Peterson, B. D.; Cilke, R.
W.; Navarro, C.
NIST NCSTAR 1-2B; 290 p. September 2005.
Keywords:
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
Abstract:
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.
The tower models used in the global impact analyses were
developed based on the original WTC drawings and the
structural databases of the towers developed within the
framework of the baseline structural performance
analysis. The tower models included the primary
structural components of the towers in the impact zone,
including exterior walls, floor systems, core columns,
and connections. A refined finite element mesh was used
for the areas in the path of the aircraft and a coarser
mesh was used elsewhere. The models also included the
nonstructural building contents, such as partitions and
workstations, in the path of the aircraft debris. The
Boeing 767 aircraft model was developed based on
information gathered from documentary aircraft
structural information, and data from measurements on a
Boeing 767 aircraft. The model included the aircraft
engines, wings, fuselage, empennage, and landing gear,
as well as nonstructural components of the aircraft. A
detailed analysis was carried out to estimate the fuel
distribution in the aircraft wings at the time of
impact.
