Replication Analysis of Shaking Table Test for Floating Seismic Isolation System

Abstract This study presents the replication analysis of the shaking test for floating seismic isolation system (FSIS) conducted using the world largest shaking table “E-Defense” in Japan. The FSIS technology can provide prominent seismic isolation effects not only for the horizontal direction but also for the vertical direction. One of the unique features in FSIS is the air cavity rooms equipped with the bottom side of the floating structure. These air cavity rooms play a role of suspensions reducing resonant frequency of the floating structures in the vertical motions so that the seismic isolation effect can be obtained for the vertical direction. Although the seismic isolation effects were substantiated by the shaking tests, there were some limitations in the shaking test. In this study, the dynamic analyses have been performed to comprehend the dynamic behaviors of the floating structures in the shaking test by replicating the same situation as the shaking test, and to evaluate the actual seismic isolation performance by eliminating factors disturbing the seismic isolation effects in the shaking test. Through the replication analyses, main dynamic modes of the FSIS test facilities could be represented. Also, the simulation results revealed that the bulging effect of the pool vessel augments the response of the floating structure so that the seismic isolation effects were reduced. This effect was underpinned by conducting the sensitivity analyses on the condition that the pool vessel was changed to be stiffer. This fact will contribute to the development of the seismic analysis methodology applicable to the actual design of FSIS paired nuclear power plants.