Performance Enhancement of the Combined Outrigger and Negative Stiffness Damped Substructure System: Experimental Investigation and Demand‐Oriented Optimization

ABSTRACT This paper proposes a demand‐oriented optimization procedure (DOOP) to explore the optimal design of the combined outrigger and negative stiffness damped substructure system (CO‐NSDSS) under nonstationary seismic excitation. A mechanical model of the negative stiffness device was developed, and the experimental tests were conducted. The simplified analytical model of the CO‐NSDSS was established. The nonstationary seismic excitation was represented as Clough–Penzien with a time modulation function. The state‐space equation of motion and nonstationary seismic excitation was integrated to form the augmented damper–structure–excitation. Subsequently, the Pareto optimal fronts (POF) were used to address competing demand‐oriented objectives, defined as a combination of harmful inter‐story drift and acceleration, through the solutions of the Lyapunov equations. The optimum parameters of the CO‐NSDSS were investigated for various seismic records regarding dynamic response and energy dissipation. The results illustrate the validity of the DOOP and highlight the benefits of the CO‐NSDSS compared to the combined outrigger and substructure system (COSS) and combined outrigger and viscous damped substructure system (CO‐VDSS).