Multi-Mode Pushover Procedure to Estimate Higher Modes Effects on Seismic Inelastic Response of Steel Moment-Resisting Frames

The paper proposes a multi-mode pushover procedure taking into account the frequency content of response spectra, higher mode effects and interaction between modes in the inelastic range. The procedure consists of conducting a set of pushover analyses by applying different generalized force vectors. Each force vector is calculated through modal analysis and simulates the instantaneous force distribution acting on the structure when the interstorey drift at one story reaches its maximum value during dynamic response to the seismic excitation. Modal truncation and reduction in the number of generalized pushovers are proposed to reduce the computational effort by proving, however, accurate estimates of the interstorey drifts at all stories. The target interstorey drift is estimated through three different modal combination procedures. The effectiveness and accuracy of the proposed method is discussed in detail.