Mitigation of the Seismic Response of Structures with Vertical Stiffness and Strength Irregularity Using Supplemental Dampers

Abstract

As part of the Canadian Seismic Research Network’s (CSRN) newly developed performance spectra-based design methodology for buildings with supplemental damping, this chapter proposes an index for quantifying the degree of vertical stiffness/strength irregularity based on elastic modal properties. Using this index, a damper distribution technique is developed to correct irregularities while adding damping to control the seismic response to meet a given set of performance targets. Nonlinear time-history analyses of simplified 4-, 9- and 15-storey irregular shear buildings with hysteretic and linear viscous and viscoelastic dampers are used to verify and to establish the limits of application of the proposed distribution technique. It is found that the procedure offers simplicity and sufficient accuracy for design purposes if the structure meets the criteria identified in this study. Retrofit examples using the proposed methodology are also presented for a 9-storey irregular steel moment frame in Canada.