Aseismic Capacity Assessment for High-rise Steel Frames Considering Inelastic Stability Effects With Sidesway

During a severe earthquake, plastic hinges can occur at the ends of beams or columns of a high-rise steel frame. Because of this, the critical load of a steel column of the frame cannot be evaluated directly from the conventional alignment charts. In this study, the inelastic stability characteristic equations for five types of substructures that cover a total of twenty-two stability modes for steel columns are derived, from which the critical load P_crand effective length factor K of a column of the frame in the inelastic stage are solved. The results show that the inelastic effective length factors K computed for the steel columns are larger than those for the elastic case for some modes, meaning that the inelastic critical load is less than the elastic critical load for the same steel column. Thus, the seismic lateral resistant capacity of a steel frame is overestimated if the columns of the frame are designed solely based on the elastic stability analysis.