© 2018 Architectural Institute of Japan. All rights reserved. This paper presents an optimal damper design strategy for highly indeterminate 3D structures utilizing computational optimization and response spectrum analysis, which has been extended to incorporate non-proportional damping. This enables a more efficient design process than trial-and-error approaches with non-linear response history analysis. He efficiency of the proposed design strategy is verified, analyzed and discussed in a series of studies using an existing lattice tower structure, popular buckling-restrained braced frames and a concentric braced frame skin structure.