Analytical prediction on static collapse resistance of steel frames in multi-interior-column-removal scenarios

Previous studies on the collapse performance of steel frames mainly focused on a single column loss. Even though the multi-column loss has been increasingly studied recently, it is generally based on the numerical analysis and relevant analytical study is rare. Moreover, the behavior of the frame after the multi-column loss should be more sensitive to its boundary condition due to a greater affected zone, compared with the single-column loss. However, this boundary condition effect has not been given enough attention in existing studies. To fill in these research gaps, this paper investigates the collapse resistance of the steel frame in two-interior-column-removal scenarios. To quantify the boundary condition effects, four column-removal scenarios, namely, two general-interior columns (GG), one general-interior column and one edge-interior column (GE), two edge-interior columns (EE), and one edge-interior column and one corner-interior column (EC) are studied. It is found that in the scenarios of GG and GE, the resistance-displacement relationship of the frame shows a tri-linear characteristic. In the scenarios of EE and EC, however, a bi-linear characteristic is exhibited. Compared with the GG scenario, the ultimate bearing capacities of the frame in the GE, EE and EC scenarios decrease by about 12%–20%, 33%–43% and 39%–52%, respectively.