Simpson Gumpertz & Heger Inc. (SGH) developed global models of the World Trade Center (WTC) towers using finite elements to gain an understanding of the roles of the aircraft impact damage and the subsequent fires in the WTC towers with respect to structural stability and sequential failures of components and subsystems and to determine the probable sequence of structural responses that led to initiation of global collapse. The study was conducted as part of the investigation on the WTC disaster by the National Institute of Standards and Technology (NIST). The developed finite-element global models of the WTC towers simulated the structural performance of the part of the buildings in and above the aircraft impact zone. These models captured the nonlinear responses of the towers subjected to the aircraft impact damage and the subsequent fire effects. The nonlinearities included in the global models were 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. NIST provided temperature-dependent nonlinear material properties, estimates of aircraft impact damage to structural members, and temperature time histories of structural elements, which were used as input in this study.
Citation: NIST NCSTAR - 1-6
Pub Type: NIST Pubs
World Trade Center, high rise buildings, building collapse, disasters, fire safety, fire investigations, terrorists, terrorism, structural analysis, damage, walls, plastics, stability, deflection, structural responce, impact