Session: SE-05-02 Structural Dynamics-2

Paper Number: 152929

152929 - Fluid-Structure-Soil Interaction Analysis Applicable to Seismic Design for Floating Seismic Isolation System 

Abstract: 

In this study, the practical seismic analysis method applicable to Floating Seismic Isolation System (FSIS) is proposed using Fluid-Structure-Soil Interaction (FSSI) analysis approach. In the previous study of the replication analysis for the FSIS shaking test, it was revealed that the instantaneous deformation of the pool vessel due to the excitation augments the seismic response of the floating structure. When assuming nuclear power plants (NPPs) are installed onto the floating structure of FSIS in the inland, part of the pool structure of FSIS is to be embedded in the soil. In this case, the soil structure interaction (SSI) can be a significant factor affecting the floating structure by the pressure propagation from the pool walls via pool water. Additionally, the execution of SSI analysis for NPPs with base seismic isolations is required in both US regulatory guide, NUREG/CR-7253 as well as the industrial code, ASCE/SEI 4-16. Since the FSIS adopts water as a mean of seismic isolation, it is also necessary to make the fluid dynamic effect coupled with the SSI effect. Therefore, this study proposes modelling method of FSIS model as well as FSSI analysis methodology for FSIS paired NPPs using the commercial software, ACS SASSI. Firstly, the FSIS modelling and analyses in ACS SASSI were verified using a simplified sample model. In the ACS SASSI model, the fluid elements were assumed as inviscid and compressive flow by applying stress-strain relationship in the same way as solid mechanics. At the boundaries between fluid and structures, each node in the same positions from both fluid and structure part was connected via spring elements with each other. The analysis result by the ACS SASSI model was confirmed to agree well with that obtained by another commercial software, ABAQUS. The verified modelling techniques of FSSI in ACS SASSI, were then used to produce a FSSI model of the main facilities of the NPP supported on a floating structures. The FSIS paired NPPs were assumed to be embedded in the soil. Through the trial FSSI analyses, the significant seismic isolation effect of nuclear structures with the floating structure has been confirmed even under the deformation of the pool structure with the surrounding soil during earthquakes. The reduction of the seismic responses can moderate seismic loads affecting structures, systems and components, as well as contribute to the optimal plant design in earthquake-prone countries.

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