Structural Response of WTC 7 Floor Systems to Fire

The WTC 7 investigation by the National Institute of Standards and Technology (NIST) identified several factors that alone, or in combination, led to fire-induced failures of the floors, and subsequently, total collapse of the 47-story WTC 7 building. At the present time, a sensitivity study is being conducted to determine the relative contribution of the identified factors, which includes the presence or absence of shear studs on girders, connection types, asymmetric framing, and bay span lengths. The technical basis for the identified structural factors is presented in this paper.