This report presents a computational assessment of the performance of steel gravity framing systems with single-plate shear (shear tab) connections and composite floor slabs under column loss scenarios. The computational assessment uses a reduced modeling approach, while comparisons with detailed model results and available experimental data are presented to establish confidence in the reduced models. The reduced modeling approach enables large multi-bay systems to be analyzed much more efficiently than the detailed modeling approaches used in previous studies. Both quasi-static and sudden column loss scenarios are considered, and an energy-based approximate procedure for analysis of sudden column loss is adopted, after verification through comparisons with direct dynamic analyses, further enhancing the efficiency of the reduced modeling approach. Reduced models are used to investigate the influence of factors such as bay spacing, slab continuity, and the mode of connection failure on the collapse resistance of gravity frame systems. Simple equations for the rotational capacities of the connections are derived as a function of a few parameters including the span length and the connection depth. These equations yield good agreement with computed rotational capacities of connections both in bare steel assemblies (i.e., no slab) and in composite floor systems, where composite action leads to reduced rotational capacities. The reduced models are used to assess the adequacy of current structural integrity requirements, and based on the computational results, a new relationship is proposed between the uniform load intensity and the tie forces required for collapse prevention.
Citation: Technical Note (NIST TN) - 1749
NIST Pub Series: Technical Note (NIST TN)
Pub Type: NIST Pubs
Buildings, Connections, Floors, Finite element method, Nonlinear analysis, Progressive collapse, Steel structures