Modeling of the seismic isolation system plays a key role in simulating the seismic response of base isolated nuclear power plants (NPP), including estimation of peak isolator displacement and potential to exceed the clearance to stop. Under beyond design basis shaking, seismic isolators such as lead rubber bearings (LRB) may undergo large displacements and exhibit complex behavior including cyclic heating causing strength degradation of the lead and strain hardening in the rubber at large strains. Displacement demands on the isolation system can be limited by a stop such as a moat wall to prevent bearing failure, with the impact to the moat having potential to increase the transfer of forces to the superstructure. Towards a more accurate seismic assessment of NPP subjected to beyond design basis shaking, a model of a seismically isolated NPP is developed with advanced modeling capabilities for LRB isolators and simulation of moat wall impact. The bearing models capture the cyclic behavior of LRB as observed in measured experimental data from full-scale bearings designed for NPP applications. The moat wall model considers a concrete retaining wall with backfill soil and contact elements developed based on experimental data and high-fidelity Finite Element Method (FEM) simulations. The simulation tools are used to evaluate the consequences of bearing modelling and impact to moat walls on the seismic performance of NPP and further develop effective mitigation measures for the seismic protection of NPP. As a result of the studies presented here, a simplified design methodology to estimate impact response parameters including moat wall deformation due to impact, impact velocities, and forces is proposed.

隔震系统的建模在模拟基础隔爆核电站（NPP）的地震响应中起着关键作用，包括估算峰值隔振器的位移和超过停止间隙的潜力。在超出设计基准的摇动下，地震隔离器（例如铅橡胶轴承（LRB））可能会发生大位移，并表现出复杂的行为，包括循环加热导致铅的强度降低以及橡胶在大应变下的应变硬化。可以通过诸如护城河壁之类的挡块来限制对隔离系统的位移要求，以防止轴承失效，并且对护城河的冲击有可能增加力向上部结构的传递。为了使NPP在超出设计基准的情况下振动，可以进行更准确的地震评估，开发了具有地震隔离NPP的模型，该模型具有用于LRB隔离器的高级建模功能以及护城河壁撞击的模拟。轴承模型捕获了LRB的循环行为，这是从为NPP应用设计的满量程轴承的实测实验数据中观察到的。护城河墙模型考虑了具有回填土和接触元素的混凝土挡土墙，该混凝土墙是根据实验数据和高保真有限元方法（FEM）模拟而开发的。仿真工具用于评估轴承建模和对护城河墙的冲击对核电厂抗震性能的影响，并进一步开发出有效的缓解措施，用于核电厂的抗震保护。根据此处介绍的研究，