Performance improvement and demand-oriented optimum design of the tuned negative stiffness inerter damper for base-isolated structures

Base isolation is an effective earthquake protection strategy for building structures. However, the base-isolation floor may undergo large displacements under earthquake excitations. To improve the control performance of base isolation, a tuned negative stiffness inerter damper (TNSID) is proposed for base-isolated structures (BIS). The TNSID is evolved from the tuned inerter damper (TID), while adding a negative stiffness element (NS) paralleled with the inerter in the TID. Hence, the TNSID is expected to take advantages of the dual beneficial effects of the inerter and NS for structural control. Based on the simplified analytical model of the BIS, the damping enhancement equation and energy balance equation of the BIS-TNSID system are derived. On this basis, the effects of the inerter and NS of the TNSID on displacement mitigation, damping enhancement, and energy reduction of the BIS are investigated. The benefit of the tuned effect of the TNSID is also illustrated. To balance the control performance and design cost, a demandoriented optimum design method of the TNSID for the BIS is developed and extended to the MDOF structures. In addition, the effectiveness of the TNSID is examined through a design case when the BIS is subjected to stationary random and earthquake excitations. The results demonstrate the advantage of the TNSID for BIS compared with the TID, negative stiffness inerter damper, and tuned negative stiffness viscous mass damper.