Collapse resistance of steel frames with concrete slabs due to penultimate-side column loss

Steel frames with concrete floor systems have been widely used in buildings due to their high constructional efficiency and excellent seismic performance. Currently, limited analytical studies focused on the effect of boundary conditions on collapse mechanisms of steel frames with concrete slabs. This article presents a revised energy-based method to determine the collapse resistance of steel frames with concrete slabs due to a penultimate-side column loss. The detailed models of main structural members are taken into account, including reinforced concrete slabs, steel beams, and steel columns. The reasonability and reliability of the analytical method are verified against validated numerical analyses using various slab aspect ratios, slab thicknesses, rebar ratios, beam section heights, and column heights. It is found that the analytical method can be used to accurately predict the collapse resistance of steel frames due to a penultimate-side column loss with errors less than 10%. A comparison of collapse resistance of substructures subjected to penultimate-side and intermediate-side column loss shows that boundary conditions have limited effects on the plastic bearing capacity of substructures. However, the ultimate bearing capacity of substructures due to a penultimate-side column loss decreases by about 20% due to the insufficient development of tensile catenary action in steel beams.