An important aspect of progressive collapse evaluation of steel gravity frame structures is to consider the mobilization of composite action between the slab and the steel frame. After initial column failure and experiencing large deformation, catenary action develops in the floor slab and the overall response of the system changes the load transfer mechanism to the connections. As a consequence, shear connections experience extreme rotation and demands that are significantly different from those imposed by an equivalent bare frame system. This research investigates the structural integrity of steel gravity frames in conjunction with the concrete floor slab and the induced demands on the shear connections. A high-fidelity model including the floor slab components is developed to examine the performance and behaviour of the shear connections, in addition to the overall load carrying capacity of the system. Explicit quasi-static analysis is employed to overcome the convergence difficulties related to contact, geometric and material nonlinearities, large deformation, and fracture simulation. Challenges involved in developing numerical simulations of conventional composite floor framing systems when a column has been compromised are discussed. The component finite element model is validated against the results of physical tests in terms of failure mode. It is shown that the finite element analyses give reasonable accuracy and agree well with the experimental results. The research results show that while the presence of the concrete floor slab contributes to the capacity of connections, it also amplifies the demand on the connections and alters the load transfer mechanism as compared to a bare frame.
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