Session: SE-02-01 Seismic Isolation

Paper Number: 152624

152624 - 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 inadvertent conditions and limitations in the shaking test. In this study, the dynamic analyses have been performed to achieve the following objectives; one is to comprehend the dynamic behaviors of the floating structures in the shaking test by replicating the same situation as the shaking test, and the other is to evaluate the actual seismic isolation performance by eliminating factors disturbing the seismic isolation effects in the shaking test.

The FSIS shaking test facilities was modeled using the commercial FEM program ABAQUS. In this study, the following two models were prepared; one is Type-A model which doesn’t have air cavity rooms in the floating structure, and the other is Type-B which have air cavity rooms at the bottom side of the floating structure. Type-A analysis model consists of the pool vessel, the floating structure, and water. Type-B analysis model has the air at the bottom of floating structures, in addition to the same material as Type-A. The pool vessel reinforced by steel beams was modelled by shell elements to represent the similar dynamic behavior as the actual test specimen. Water and air were modelled using acoustic elements. The harmonic analyses were conducted using mode-based steady-state dynamic analysis method, and the analysis results were compared with the shaking test results as transfer functions.

In the simulation, 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.

Presenting Author: Yuki Sato JGC Corporation

Presenting Author Biography: Yuki Sato is a senior project engineer for nuclear business as well as a structural analysis engineer in JGC Corporation. He has a master degree in mechanical engineering from the University of Tokyo. After the graduation, he embarked upon a career in a seismic, structural and mechanical regions for nuclear power plants. He worked for Hitachi-GE Nuclear Energy, Ltd. as a seismic engineer. He has been involved in some seismic research projects, Japanese domestic plant restart projects, and UK ABWR GDA/Wylfa Projects. After transferring to JGC Corporation, he has conducted structural analyses for some plant engineering projects. Currently, he has been leading technology developments for Nuclear SMR plants in terms of seismic/structural engineering. Concurrently, he has been doing seismic analysis researches as a Ph.D student in the University of Tokyo.

Authors:

Yuki Sato JGC Corporation
Akihito Otani IHI Corporation
Satoru Kai IHI Corporation
Xing L. Yan Japan Atomic Energy Agency
Shunji Kataoka JGC Corporation
Issei Ota JGC Corporation
Yasutomi Morimoto JGC Corporation