Development of an Evaluation Method for Seismic Isolation Systems of Nuclear Power Facilities: Part 11 — Improvement of the Seismic Isolator Design Method

Abstract

This paper provides a part of series of “Development of an Evaluation Method for Seismic Isolation Systems of Nuclear Power Facilities”. This part shows improvements of seismic isolator design method applied to nuclear power facilities. The proposed improvement design methods consist of the following two items. One is an improvement of design method for axial stress in a laminated rubber bearing. Largely different natural frequency in vertical and horizontal direction of the seismic isolator may need a special consideration to combine the design seismic loads in different directions. Therefore isolator’s behavior under multiple direction earthquake is studied, and an improved design method is proposed in the axial stress in a laminated rubber bearing. The other is a reasonable design method for seismic isolator joints. A seismic isolator joint is considered to be one of the key factors for assuring seismic integrity of the seismic isolation system for nuclear power facilities. As a series of design method of seismic isolators, evaluation method of axial force of anchor bolts, among various parts of joints, under design level seismic load is studied and improved method is proposed to confirm the structural behavior for a better performance of the system.