積層ゴム破断時における免震構造システムの地震応答: E-ディフェンス振動台実験による免震構造物の終局時挙動の解明　その1

摘要

For next generation Fast Breeder Reactor (FBR), application of seismic isolation technology to the reactor building is planned to reduce seismic loading to both internal equipment and structures. To grasp seismic behavior of the base-isolated plant to extremely strong quake beyond design ground motion, large-scale shaking table tests are conducted using world largest shaking table "E-Defense" of the National Research Institute for Earth Science and Disaster Prevention. Two sets of one-third scale specimens are tested where the superstructure of 6000 kN weight is supported by six lead rubber bearings (LRBs) of diameter 505 mm. Two or one LRBs are ruptured by the excitation of 4.0 to 4.8 times as large as the presumed design earthquake motion, when the shear strains of the LRBs reached over 550% or more. These ultimate shear strains and the stress-strain curves in the shake test are in good agreement with those of static loading tests using another LRBs made at same time. After these extremely strong excitations, the test specimens behave stably against the seismic inputs of design level even after some of the isolators are ruptured.%FBR免震プラントを対象として，残余のリスク評価のための実証データを得ることを目的として，直径505mm,支持荷重100トンの鉛プラグ入り積層ゴム6体を用いた免震システム試験体2体の振動台実験を実施した。主な実験内容は，設計地震動を入力倍率225％で与えて積層ゴムをハードニング応答させる試験や，設計地震動の狭帯域フィルター波を入力倍率400~480％で与えて積層ゴムを破断させる試験，積層ゴムを破断させた状態で設計地震動に対する地震応答を把握する試験である。