A novel nonlinear seismic base isolation concept

We present a unique response reduction strategy for complex structures subjected to ground motion. The primary focus of our efforts has been the development of a new type of passive nonlinear seismic isolation system for protection of flexible structures. The proposed design is based on the concept of nonlinear localization whereby induced vibrational energy is passively confined to a preassigned secondary system and away from the primary structure to be isolated. We show that such a robust nonlinear localization phenomenon can be effected by (a) tuning the isolation system so that a 1:1 internal resonance exists between the secondary substructure and a mode of the primary structure; and (b) inducing a strongly localized nonlinear normal mode that is predominantly confined to the secondary substructure. The performance of the system under both historic and generated earthquake inputs is demonstrated by simulation.