Seismic Isolation Technology Research Articles

Isolation systems influence in the seismic loading propagation analysis applied to an innovative near term reactor

Integrity of a Nuclear Power Plant (NPP) must be ensured during the plant life in any design condition and, particularly, in the event of a severe earthquake. To investigate the seismic resistance capability of as-built structures systems and components, in the event of a Safe Shutdown Earthquake (SSE), and analyse its related effects on a near term deployment reactor and its internals, a deterministic methodological approach, based on the evaluation of the propagation of seismic waves along the structure, was applied considering, also, the use of innovative anti-seismic techniques. In this paper the attention is focused on the use and influence of seismic isolation technologies (e.g. isolators based on passive energy dissipation) that seem able to ensure the full integrity and operability of NPP structures, to enhance the seismic safety (improving the design of new NPPs and if possible, to retrofit existing facilities) and to attain a standardization plant design. To the purpose of this study a numerical assessment of dynamic response/behaviour of the structures was accomplished by means of the finite element approach and setting up, as accurately as possible, a representative three-dimensional model of mentioned NPP structures. The obtained results in terms of response spectra (carried out from both cases of isolated and not isolated seismic analyses) are herein presented and compared in order to highlight the isolation technique effectiveness.

Experimental verification of a piezoelectric smart isolation system

To improve the performance of conventional seismic isolation technology, a semi-active isolation system, named a ‘Piezoelectric Smart Isolation System (PSIS)’, which is composed of a sliding isolation platform and a piezoelectric friction damper (PFD), is introduced and investigated experimentally in this study. Because the friction force of the PFD in the PSIS can be regulated by an embedded piezoelectric actuator through a DC voltage, the PFD is able to provide a controllable damping force for the isolation system. As a result, the seismic response of the PSIS can be effectively controlled and mitigated. In order to verify its feasibility, a prototype PSIS was fabricated and tested dynamically via a shaking table test. The accuracy of the test data has been confirmed by the good consistency between the experimental and theoretical results. The experimental results have demonstrated that, when compared to the uncontrolled counterpart, the PSIS is able to substantially suppress both the displacement and acceleration responses in an earthquake with either near-fault or far-field characteristics. The study has also shown that, although the semi-active PSIS system can only provide a variable passive control force, it is able to achieve the same level of control performance as an actively controlled isolation system, which shares the same optimal feedback gain as that of the PSIS. Copyright © 2010 John Wiley & Sons, Ltd.

Assessment of the Seismic Risk in the City of Yerevan and its Mitigation by Application of Innovative Seismic Isolation Technologies

It is obvious that the problem of precise assessment and/or analysis of seismic hazard (SHA) is quite a serious issue, and seismic risk reduction considerably depends on it. It is well known that there are two approaches in seismic hazard analysis, namely, deterministic (DSHA) and probabilistic (PSHA). The latter utilizes statistical estimates of earthquake parameters. However, they may not exist in a specific region, and using PSHA it is difficult to take into account local aspects, such as specific regional geology and site effects, with sufficient precision. For this reason, DSHA is preferable in many cases. After the destructive 1988 Spitak earthquake, the SHA of the territory of Armenia has been revised and increased. The distribution pattern for seismic risk in Armenia is given. Maximum seismic risk is concentrated in the region of the capital, the city of Yerevan, where 40% of the republic’s population resides. We describe the method used for conducting seismic resistance assessment of the existing reinforced concrete (R/C) buildings. Using this assessment, as well as GIS technology, the coefficients characterizing the seismic risk of destruction were calculated for almost all buildings of Yerevan City. The results of the assessment are presented. It is concluded that, presently, there is a particularly pressing need for strengthening existing buildings. We then describe non-conventional approaches to upgrading the earthquake resistance of existing multistory R/C frame buildings by means of Additional Isolated Upper Floor (AIUF) and of existing stone and frame buildings by means of base isolation. In addition, innovative seismic isolation technologies were developed and implemented in Armenia for construction of new multistory multifunctional buildings. The advantages of these technologies are listed in the paper. It is worth noting that the aforementioned technologies were successfully applied for retrofitting an existing 100-year-old bank building in Irkutsk (Russia), for retrofit design of an existing 177-year-old municipality building in Iasi (Romania) and for construction of a new clinic building in Stepanakert (Nagorno Karabakh). Short descriptions of these projects are presented. Since 1994 the total number of base and roof isolated buildings constructed, retrofitted or under construction in Armenia, has reached 32. Statistics of seismically isolated buildings are given in the paper. The number of base isolated buildings per capita in Armenia is one of the highest in the world. In Armenia, for the first time in history, retrofitting of existing buildings by base isolation was carried out without interruption in the use of the buildings. The description of different base isolated buildings erected in Armenia, as well as the description of the method of retrofitting of existing buildings which is patented in Armenia (M. G. Melkumyan, patent of the Republic of Armenia No. 579), are also given in the paper.

A new seismic isolation system and its feasibility study

This paper introduces a new seismic isolation system called a periodic foundation (PF), where inclusions are periodically arranged. The PF is different from traditional base isolation in that it causes a fundamental frequency shift in the structure, thus reducing its response and generating a frequency gap. If the frequency contents of a seismic wave fall into the gap, it can not propagate in the foundation. Thus, it will exert no influence on the structure above. A systematic study of the band of frequency gap for a 2D PF is conducted. The influence of physical and geometrical parameters such as density and elastic modulus as well as filling fraction of the PF and its materials on the band of frequency gap are investigated, and a design with a frequency gap as low as 2.49–3.72 Hz is achieved. This band of frequency gap corresponds well to the design spectra in earthquake engineering. Numerical simulations of a six-story frame structure with different foundations demonstrate that a proposed PF can greatly reduce the seismic response of an isolated structure. This investigation shows that PFs have great potential in future applications of seismic isolation technology.

Seismic Isolation Technologies Established in an Earthquake Country

Seismic Isolation Technologies Established in an Earthquake Country

Lifecycle cost–benefit analysis of isolated buildings

Seismic isolation is effective in reducing seismic demand to buildings and mitigating seismic damage costs. To corroborate this fact quantitatively by taking all possible seismic events that occur during the service period of a building into account, this study investigates probabilistic characteristics of the peak ductility demand of inelastic superstructures with linear/bilinear base isolators subject to hundreds of strong ground motion records, and then assesses the cost-effectiveness of seismic isolation technology from the lifecycle cost–benefit perspective. Based on results from nonlinear dynamic analyses of two-degree-of-freedom systems with the Bouc–Wen hysteretic model, a prediction model for the peak ductility demand of isolated structures is developed and used in lifecycle cost analysis to assess the cost-effectiveness of seismic isolation systems. The analysis results show that seismic isolation reduces vibration in superstructures significantly and can be cost-effective in mitigating seismic risk.

Development of Elevated Temperature Structual Design Standard and Three-Dimensional Seismic Isolation Technology for Advanced Nuclear Power Plant

Development of Elevated Temperature Structual Design Standard and Three-Dimensional Seismic Isolation Technology for Advanced Nuclear Power Plant

ゴムと建築・建設材料 建築免震用積層ゴム支承

Destructive earthquakes may happen anytime anywhere at. Many lives and property were lost, and public traffic and life-lines suffered from damages in the past seismic events. Seismic isolation technology has gained popularity in the recent decade as one of the measures fo+r seismic protection of structures, and elastomeric isolators are the essential devices which construct seismic isolation systems. In this paper, principle of seismic isolation, actual records obtained in seismic-isolated structures, characteristics and requirements of isolators, basic issues of rubber materials and aging properties, and recent activity regarding development of ISO standards are introduced.

433 発電用新型炉へ適用する3次元免震システムの研究 : 開発計画の検討:その5

Mitigation of the earthquake loads by seismic isolation technology is very promising for enhanced safety and economy of the next generation nuclear power plant. A research for 3D seismic isolation technologies has been conducted under the sponsorship of the Ministry of Economy, Trade and Industry. Two types of 3D seismic isolation systems were developed. One is the 3D entire building base isolation system. The other is the vertical isolation system for main components in the horizontally entire building base isolation. For the former technology, the "rolling seal type air spring + hydraulic rocking suppression system" is selected after several studies. For the latter, the coned disk spring system is adopted. The reduced models of the two systems were tested on the shake tables. The test results show that the two systems satisfy the requirements of isolation and are applicable to the plant.

102 発電用新型炉へ適用する3次元免震システムの研究 : 開発計画の検討:その4(免震構造1,OS-12:耐震・免震・制振(1))

Mitigation of earthquake loads by seismic isolation technology is very promising for enhanced safety and economy of the next generation nuclear reactors. A research project has been undertaken for the development of 3D seismic isolation technology, under the sponsorship of the Ministry of Economy, Trade and Industry. There are two types of 3D seismic isolation system concept. One is the 3D entire building base isolation technology and another is the vertical isolation device for main component with horizontally entire building base isolation technology. For the former technology, three types of system concept were nominated. These are "Hydraulic 3D base isolation system", "Independent cable reinforced rolling-seal air spring" and "Rolling seal type air spring". This paper reports the performance requirements for 3D isolation system and the criteria for the system selection.

SEISMIC ISOLATION OF HIGHWAY BRIDGES

This paper introduces the seismic isolation technology for highway bridges in Japan. Systematic application of seismic isolation was initiated in early 1990s. In particular it was accelerated after the 1995 Kobe earthquake. Guidelines and design specifications for seismic isolation are introduced. Typical implementation of seismic isolation to highway bridges are also presented.

Seismic Behavior of a Newly Developed Base Isolation System for Houses

abstractThe good performance of seismically isolated structures during the 1995 Kobe earthquake persuaded structural engineers, isolator manufacturers and housing construction companies to undertake a cooperative research project to investigate the possibility of introducing the seismic isolation technology in Japan's private housing sector. As a part of this project, in this study, the seismic performance of a recently developed Friction Pendulum System (FPS) for houses is presented. In order to verify its behavior under recorded earthquake ground motions, 3-dimensional shaking table tests were conducted. A three-dimensional nonlinear model was used to simulate the experimentally recorded acceleration and displacement response. Experimental results showed that the FPS significantly reduced the acceleration response at both moderate and strong levels of input ground motion. The analytical model used in this study satisfactorily predicted the experimentally recorded acceleration and displacement response time histories.

Seismic base isolation technologies for Korea advanced liquid metal reactor

This paper describes the status and prospects of the seismic base isolation technologies for Korea Advanced Liquid Metal Reactor (KALIMER). The research and development program on the seismic base isolation for KALIMER began in 1993 by KAERI under the national long-term R&D program. The objective of this program is to enhance the seismic safety, to accomplish the economic design, and to standardize the plant design through the establishment of technologies on seismic base isolation for liquid metal reactors. In this paper, tests and analyses performed in the program are presented.

２１世紀に向けた課題と提言 人間の生活を守る技術 地震対策技術（免震技術）の課題と提言

２１世紀に向けた課題と提言 人間の生活を守る技術 地震対策技術（免震技術）の課題と提言

Isolation System for Equipment using Friction Pendulum Bearings. 1st Report. Shaking Table Tests and Response Analysis on Isolated Equipment.

During the last few years, as we enter a new era of a high-level information-oriented society, the number of buildings having multiple functions has been increasing. Seismic isolation technology can protect not only the structural elements of a building but also its primary function from destructive earthquake motion. It is with such background that many types of earthquake isolation floors or systems have already been developed and have spread throughout in Japan. Almost all isolation floors/systems developed with especially for critical equipment such as computer systems so far consist of coil springs to provide equipment a designed natural frequency and energy-absorbing devices such as friction dampers and oil dampers. However, these types of earthquake isolation floors or systems may become expensive although they perform satisfactorily. The friction pendulum bearings developed in this program can solve this problem. This device consists of an articulated friction slider which moves on a spherical concave surface and provides the supported equipment with a designed frequency obtained by a radius of curvature and gravity. The articulated friction slider dissipates energy as a friction damper. In this paper we conducted shaking table tests and theoretical analysis in order to investigate the performance of isolation and the restoring force characteristics of the earthquake isolation system using the friction pendulum bearings.