Displacement-based design of supplemental dampers for seismic retrofit of a framed structure

The procedure of direct displacement-based design (DBD), presented in the SEOAC Blue Book, was modified to evaluate the seismic performance of existing structures. Then an optimum number of velocity-dependent supplemental dampers, such as viscous and viscoelastic dampers, required to reduce the seismic response of existing structures to a given performance limit state was evaluated. The proposed method was applied to seismic performance evaluation and performance-based seismic retrofit of ten- and 20-story steel frames, and the final design was verified by time history analyses using artificial earthquake records generated based on the design spectrum. According to the analysis results, the performance points evaluated by the proposed method match well with those computed by time-history analyses, and the maximum displacements of the model structures retrofitted by the supplemental dampers corresponded well to the given target values.