• Nuclear Engineering and Technology
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• 제48권5호
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• pp.1237-1251
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• 2016

Although the horizontal component of an earthquake response can be significantly reduced through the use of conventional seismic isolators, the vertical component of excitation is still transmitted directly into the structure. Records from instrumented structures, and some recent tests and analyses have actually seen increases in vertical responses in base isolated structures under the combined effects of horizontal and vertical ground motions. This issue becomes a great concern to facilities such as a Nuclear Power Plants (NPP), with specialized equipment and machinery that is not only expensive, but critical to safe operation. As such, there is considerable interest worldwide in vertical and three-dimensional (3D) isolation systems. This paper examines several vertical and 3D isolation systems that have been proposed and their potential application to modern nuclear facilities. In particular, a series of case study analyses of a modern NPP model are performed to examine the benefits and challenges associated with 3D isolation compared with horizontal isolation. It was found that compared with the general horizontal isolators, isolators that have vertical frequencies of no more than 3 Hz can effectively reduce the vertical in-structure responses for the studied NPP model. Among the studied cases, the case that has a vertical isolation frequency of 3 Hz is the one that can keep the horizontal period of the isolators as the first period while having the most flexible vertical isolator properties. When the vertical frequency of isolators reduces to 1 Hz, the rocking effect is obvious and rocking restraining devices are necessary.

• 전산구조공학
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• 제3권1호
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• pp.71-81
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• 1990

Base isolation system은 구조물의 기초하부에 설치되며 지진에 의한 구조물의 피해를 감소시켜 준다. 지금까지 많은 공학들에 의해 여러가지 base isolation system이 개발되었으나 실용화된 것은 1970년대에 laminated rubber bearing(LR type)이 개발되고서부터 였다. 최근에는 laminated rubber bearing밑에 미끄럼판을 둔 새로운 base isolation system(SR type)이 개발되었다. 본 연구에서는 isolation system과 구조물의 여러가지 성질에 따른 isolation효과에 대한 연구를 수행하였다. 이 연구의 결과, isolaion system은 지진하중이 작용할 때 건물에 발생하는 피해를 상당히 감소시킴을 알 수 있으며, isolaion system의 주기가 길어짐에 따라 isolation효과는 증가함을 알 수 있다. 그리고 건물의 높이가 증가함에 따라 isolation효과는 줄어든다는 것을 알 수 있다. SR type isolation system이 있는 건물에 지진하중이 작용할 때, 건물내부에서 발생하는 가속도와 층간변위, 그리고 전체변위는 LR type의 경우보다 작으므로 보다 효율적이라는 것을 알 수 있다.

• 한국공간구조학회논문집
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• 제8권2호
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• pp.73-84
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• 2008

지진에 의한 구조물의 응답을 저감시키기 위하여 내진, 면진, 제진 등 다양한 장치가 사용되고 있으며 그 중에서 면진장치는 구조물로 전달되는 지진에너지를 최소화하기 위한 시스템으로 그 주된 목적은 구조물의 주기를 길게 만들어 지진파의 탁월주기를 벗어나게 하는 것이다. 본 연구에서는 대공간구조물의 기본적인 동적특성을 가지고 있으며 동시에 가장 간단한 구조이기도 한 아치에 납-고무면진장치와 마찰진자면진장치를 적용하여 지진거동을 분석하였다. 대공간구조물의 지진거동은 일반적인 골조구조물의 지진거동과 달리 수평지진에 의하여 수직방향으로 큰 지진응답이 나타나고 있다. 면진장치를 대공간 구조물에 적용할 경우에 수평지진하중에 의하여 수평방향 지진응답이 저감되는 것은 물론 면진장치의 수직강성으로 인하여 수직응답도 현저하게 저감되는 것을 알 수 있었다.

• Structural Engineering and Mechanics
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• 제51권4호
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• pp.643-650
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• 2014

A chaotic vibration isolation system is designed according to the chaotic vibration theory in this paper. The strong nonlinearity is generated by the system. Line spectra in the radiated noise maybe easily detected caused by marine vessels. It is Important to reduce the line spectra by improving the acoustic stealth of marine vessels. A multi-degree-freedom (MDF) nonlinear vibration isolation system (NVIS) system is setup by the experiment and finite element method. The model is established with finite element method. The results show that the behavior of the device gradually varies from period bifurcation into chaotic state and the line spectrum is changed from single spectral structure into broadband spectral structure. It is concluded that chaotic vibration isolation is preferable contrasted on line spectra isolation.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2008년도 추계 학술발표회 제20권2호
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• pp.105-108
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• 2008

교량의 내진설계에 적용되는 지진격리받침은 초창기 외국제품 수입에서 시작하여 현재는 국내업체의 자체 생산도 가능한 단계에 이르렀다고 할 수 있지만 지진격리받침의 극한적 조건에서의 특성에 대한 고찰은 거의 이루어지지 않고 있다. 본 연구에서는 다양한 지진격리받침 중에서도 많은 적용 사례가 있는 적층고무형태를 대상으로 하여 지진격리받침이 전단수평력을 받아 파괴에 이르는 전단파괴, 지진격리받침의 장기적 특성변화를 유발하는 노화, 크리프가 지진격리받침의 특성에 미치는 영향에 대하여 평가하였다. 실험을 통한 실제적인 고찰이 이루어질 수 있도록 적층고무형 지진격리받침을 실제로 제작하였고 설계수직하중을 재하한 상태에서 전단파괴에 이르도록 전단변위를 가하였다. 그리고 고무재료의 노화에 의한 특성과 영향을 분석하고자 노화촉진을 위한 고온 환경에 지진격리받침을 일정시간 노출시킨 뒤 노출 이전에 측정한 특성에 비해 얼마나 변화하였는지 비교 분석하였다. 아울러 고정된 수직하중을 받는 상태에서 고무재료의 크리프 발생으로 지진격리받침의 높이가 영구적으로 변화 할 수 있는데 받침의 수명을 고려하여 60년 후의 크리프량을 추정하였다.

• Earthquakes and Structures
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• 제4권6호
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• pp.649-670
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• 2013

It is known that a base-isolated building exhibits a large response to a long-duration, long-period wave and an inter-connected system without base-isolation shows a large response to a pulse-type wave. To compensate for each deficiency, a new hybrid passive control system is investigated in which a base-isolated building is connected to another building (free wall) with oil dampers. It is demonstrated that the present hybrid passive control system is effective both for pulse-type ground motions and long-duration and long-period ground motions and has high redundancy and robustness for a broad range of disturbances.

• Structural Engineering and Mechanics
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• 제88권3호
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• pp.263-271
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• 2023

Base isolation is a widely used technique for the seismic control of structures as it reduces the structural seismic demand. However, displacement of the isolation layer is not economically feasible in congested urban areas. To resolve the issue, an innovative system is proposed here to isolate both horizontally at the base and vertically in the upper portion of the structure. A simplified linear three degree-of-freedom (3DOF) model of the system that considers the mass and stiffness ratios of the substructure has been introduced and analyzed in MATLAB by spectrum analysis. The 3DOF model results revealed that, when the period of the soft substructure reaches 2.5 times that of the stiff substructure, the isolation and the lower substructure responses decrease by 65% and 51%, respectively. Time-history analysis of a MDOF system at three frequency ratios under a wide range of ground motions indicated that, at the expense of accepting a certain large drift by the soft substructure in the upper portion of the structure, base isolation displacement can be decreased by 10%.

• 한국지진공학회:학술대회논문집
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• 한국지진공학회 1998년도 추계 학술발표회 논문집 Proceedings of EESK Conference-Spring 1998
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• pp.258-265
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• 1998

Seismic isolation has developed to the point where it may be considered as a viable design alternate for a wide range of building structures. However, it needs to consider various aspects to adopt a suitable isolation system for buildings practically. This report presents the basis for the preliminary design procedure which has been developed for the seismic isolation system using the lead rubber bearings. The design procedures have been developed to ensure that the bearings will safely support the maximum gravity load throughout the life of the structure while they provide a period shift and hysteretic damping during the design earthquake.

• Earthquakes and Structures
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• 제12권3호
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• pp.285-296
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• 2017

Base isolation is a quite practical control strategy for enhancing the response of structural systems induced by strong ground motions. Due to the dynamic effects of base isolation systems, reduction in the interstory drifts of the superstructure is often achieved at the expense of high base displacement level, which may lead to instability of the structure or non-practical designs for the base isolators. To reduce the base displacement, several hybrid structural control strategies have been studied over the past decades. This study investigates a particular strategy that employs Tuned Mass Dampers (TMDs) for improving the performance of base-isolated structures and unlike previous studies, specifically focuses on the effectiveness of this hybrid control strategy in structures that are equipped with nonlinear base isolation systems. To consider the nonlinearities of base isolation systems, a Bouc-Wen model is selected and nonlinear dynamic OpenSees models are used to perform several time-history simulations in time and frequency domains. Through these numerical simulations, the effects of several parameters such as the fundamental period of the structure, dynamic properties of the TMD and isolation systems and properties of the input ground motion on the behaviour of TMD-structure-base isolation systems are examined. The results of this study provide a better insight into the performance of linear shear-story structures with nonlinear base isolators and show that there are many scenarios in which TMDs can still improve the performance of these systems.

• Child Health Nursing Research
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• 제22권3호
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• pp.172-181
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• 2016

Purpose: This study was conducted to examine the effect of education on infection control for multidrug resistant organism (MDRO). Methods: One group pre-post time series design was used. Infection control education for MDRO infection was provided to nurses working in the Neonatal Intensive Care Unit (NICU). Knowledge and recognition were evaluated before and after education. Hand hygiene compliance, MDRO isolation rate and central line-associated bloodstream infection (CLABSI) rate were used as outcome variables. Data from 45 nurses was used for analysis. Results: General knowledge about MDRO increased (p=.011). Responses to questions about image of MDRO and MDRO management tended to change in a positive direction (p=.046). Hand hygiene compliance was 100% at pre-test, 79.5% during education period and 98.4% at post-education period. MDRO isolation rate was 6.83 per 1,000 patient days at pre-test, 10.24 during education period and 6.68 at post-education period. CLABSI rate was 3.76 per 1,000 central line days at pre-test, 6.84 during education period and 4.71 at post-education period. Conclusion: Findings indicate that the education program is effective in improving knowledge about MDRO in NICU nurses. However, more reliable indicators should be used to determine long-term effects.