Component, Connection, and Subsystem Structural Analysis. Federal Building and Fire Safety Investigation of the World Trade Center Disaster.
Component, Connection, and Subsystem Structural
Analysis. Federal Building and Fire Safety
Investigation of the World Trade Center Disaster.
Zarghamee, M. S.; Bolourchi, S.; Eggers, D. W.; Erbay,
O. O.; Kan, F. W.; Kitane, Y.; Barrett, P. R.; Gross, J.
L.; McAllister, T. P.; Liepins, A. A.; Mudlock, M.;
Naguib, W. I.; Ojdrovic, R. P.; Sarawit, A. T.
NIST NCSTAR 1-6C; 252 p. September 2005.
World Trade Center; high rise buildings; building
collapse; disasters; fire safety; fire investigations;
terrorists; terrorism; structural analysis; floors;
walls; deflection; plastics; structural response;
Simpson Gumpertz & Heger, Inc. (SGH) developed finite
element models of the components, connections and
subsystems of the World Trade Center (WTC) towers to
study their structural performance in the fire
environment that followed the aircraft impact to the
towers. The results of this study were used to develop
global models that captured with numerical efficiency
the important failure modes and sequential failures of
components and subsystems and to determine the probable
sequence of structural responses that let to the global
collapse initiation. The study was conducted as part of
the investigation on the WTC disaster by the National
Institute of Standards and Technology (NIST). The
structural response to the fire environment/ was
established by hand calculations and finite element
analyses (FEA) for: connections including interior and
exterior truss seats, knuckles, column splices, and
spandrel splices; components including a section of the
floor system, including concrete slab and a single truss
and a single column, and subsystems including full
floors and a section exterior wall. The key structural
responses, failure modes, and failure loads were
identified. The finite element models, developed in
ANSYS, captured the nonlinear responses of the
connections, components, and subsystems, including
temperature-dependent material properties such as
thermal expansion, plasticity and creep of metals, large
deflection and the resulting instability, and failure
modes of members and connections, modeled by break
elements developed for this purpose. The models were
subjected to gravity and thermal loads. Construction
sequence was included in component models. NIST provided
temperature-dependent nonlinear material properties,
aircraft impact damage to structural members, and
temperature time histories of structural elements for
subsystems, which were used as input in this study.