Nonstationary Stochastic Seismic Optimization of Base‐Isolated Nuclear Power Plant Equipped With Negative Stiffness Amplifying Damper Considering Dynamic Soil–Structure‐Interaction

ABSTRACT This paper proposes a nonstationary stochastic seismic optimization framework and investigates the performance enhancement of base‐isolated nuclear power plants (NPPs) equipped with negative stiffness amplifying dampers (NSADs), while explicitly accounting for dynamic soil–structure‐interaction (SSI). A practical configuration for the application of NSADs in base‐isolated NPP is presented, and the governing equations of motion incorporating NSAD and SSI effects are formulated. By integrating nonstationary seismic excitation with the dynamic representation of the isolated NPP, a time‐variant augmented system is established. A multi‐objective optimization framework is then developed to address the trade‐off between minimizing superstructure acceleration and base isolator drift. Numerical results for a 1000 MW pressurized water reactor demonstrate that the proposed NSAD system effectively reduces superstructure accelerations compared to the conventional base isolation (BI) design, owing to its negative stiffness feature. Meanwhile, base isolator drift is effectively controlled through the damping amplification mechanism of the NSAD, even with a significantly smaller damping demand. For the NPP model considered in this paper, SSI has pronounced influence on superstructure‐dominated mode particularly for containment structure of non‐isolated, base‐isolated, and NSAD‐enhanced NPPs, whereas its effect on the isolation‐dominated mode is negligible.