Three-dimensional periodic materials as seismic base isolator for nuclear infrastructure

Witarto Witarto,Y L Mo,S J Wang,Jiaji Wang,Yu Tang,C Y Yang,K C Chang

doi:10.1063/1.5088609

Abstract

Recent advance of periodic materials from the field of solid-state physics into that of earthquake engineering has resulted in a novel seismic isolation technique. In this study, we developed a new configuration of structural foundation using a three-dimensional (3D) periodic material for seismic isolation of critical infrastructure, particularly nuclear infrastructure. To this aim, we first performed analytical and finite element studies to compare two different types of 3D unit cells, i.e., Bragg Scattering and Locally resonant unit cells, to investigate their characteristics and applicability as a seismic isolator. We then designed a large scale test specimen based on the Bragg-scattering type unit cell using common construction materials: reinforced concrete blocks and polyurethane sheets. The designed test specimen was constructed and tested using a shake table subjected to different types of excitations in the horizontal and vertical directions as well as the torsional mode. The dynamic response of a small modular reactor (SMR) building model protected by the 3D periodic foundation demonstrates that 90% response reduction was achieved within the frequency band gaps. The response attenuation was achieved in all three tested directions. Moreover, the periodic foundation-isolated SMR building exhibited a stable response with negligible rocking on the structural system.

Highlights

The seismic base isolation system has been studied extensively in the last fifty years by a number of national and international academic and research institutions and has been practically used to protect many engineering structures around the world.1,2 The system has recently been proposed and applied as a strategy to protect nuclear infrastructure from seismic hazards.3–5 The basic idea of the seismic base isolation systems is quite simple
The dynamic response of a small modular reactor (SMR) building model protected by the 3D periodic foundation demonstrates that 90% response reduction was achieved within the frequency band gaps
Since the attenuation zones are the essential property in a periodic foundation, it is necessary to investigate whether the designed 3D periodic foundation possesses the property

Summary

Introduction

The seismic base isolation system has been studied extensively in the last fifty years by a number of national and international academic and research institutions and has been practically used to protect many engineering structures around the world. The system has recently been proposed and applied as a strategy to protect nuclear infrastructure from seismic hazards. The basic idea of the seismic base isolation systems is quite simple. Devices such as the rolling seal type air spring and hydraulic isolation systems were developed to provide isolation in the vertical direction Both systems are proposed to be combined with laminated rubber bearings for horizontal isolation. Other systems such as thick rubber layer bearings were invented to provide seismic isolation in both the horizontal and vertical directions. The thick rubber layers provide flexibility in both the horizontal and vertical directions simultaneously Another similar system, known as the GERB system, consists of large helical springs that are flexible both horizontally and vertically. Known as the GERB system, consists of large helical springs that are flexible both horizontally and vertically Researchers found that these proposed vertical isolation systems are prone to rocking when subjected to horizontal earthquakes.. These houses, were severely shaken by the 1994 Northridge Earthquake due to the rocking motion introduced by the system.

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