• Earthquakes and Structures
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• 제16권1호
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• pp.1-9
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• 2019

To provide a simplified method for the base isolation design of LNG tanks, such as $16{\times}104m^3$ LNG tanks, we conducted a derivation and calculation example analysis of the dynamic response of the base isolation of LNG storage tanks, using dynamic response analysis theory with consideration of pile-soil interaction. The ADINA finite element software package was used to conduct the numerical simulation analysis, and compare it with the theoretical solution. The ground-shaking table experiment of LNG tank base isolation was carried out simultaneously. The results show that the pile-soil interaction is not obvious under the condition of base isolation. Comparing base isolation to no isolation, the seismic response clearly decreases, but there is less of an effect on the shaking wave height after adopting pile top isolation support. This indicates that the basic isolation measures cannot control the wave height. A comparison of the shaking table experiment with the finite element solution and the theoretical solution shows that the finite element solution and theoretical solution are feasible. The three experiments are mutually verified.

• 한국구조물진단유지관리공학회 논문집
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• 제28권1호
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• pp.70-81
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• 2024

본 연구에서는 진동원으로서 교통하중(고속열차)에 대해 수직 방진기능과 수평 면진기능을 조합한 3차원 하이브리드 면진시스템(Tridimensional Hybrid Isolation System, THIS)을 제안하였고, 고속열차 진동에 대한 THIS의 수직 진동 사용성 개선 효과를 해석적으로 평가하였다. 해석을 위하여 실제 16층의 공동주택을 상용구조해석프로그램의 고유치해석과 침실 바닥판에 대한 펄스 응답 분석을 통해 주요 진동모드를 식별하였고, 이 주요 진동 모드를 가지고 바닥판의 수평과 수직, 회전 자유도를 가지는 16개 층의 골조 모델을 제작하였다. 해석방법은 실제 고속철도가 통행할 때 철로와 인접한 구조물에서 계측한 가속도를 진동원으로 적용하고 THIS의 강성과 감쇠비를 변수로 상태-공간방정식을 이용하여 동적해석을 수행하였다. 그 결과, 기존 구조물의 수직 고유주기 대비 THIS의 수직 주기가 커질수록 층별 바닥판 응답이 저감되기 시작하는 임계 주기비가 다르고, 주기가 5배 이상(0.006 이하의 강성비)일 때 모든 바닥판의 가속도 수준이 비면진 대비 약 70% 이하로 감소하였다. 또한, THIS의 감쇠비에 대한 응답 제어에 미치는 영향이 매우 적은 것으로 나타났다. 마지막으로 THIS에 대한 수직 진동 사용성 개선 효과를 확인하기 위하여 비면진 구조물과 0.006의 강성비와 0.03의 감쇠비를 가지는 THIS가 적용된 구조물에 대하여 1층과 16층 바닥판 가속도를 AIJ, SCI, AISC 진동 사용성 기준에 따라 평가하였고, 기존에 주거지 사용성 기준을 만족하지 못한 데 반해, THIS 적용 후 주거지 사용성 기준을 모두 만족하는 것을 확인하였다.

• Smart Structures and Systems
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• 제18권2호
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• pp.293-315
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• 2016

Seismic isolation is often used in protecting mission-critical structures including hospitals, data centers, telecommunication buildings, etc. Such structures typically house vibration-sensitive equipment which has to provide continued service but may fail in case sustained accelerations during earthquakes exceed threshold limit values. Thus, peak floor acceleration is one of the two main parameters that control the design of such structures while the other one is peak base displacement since the overall safety of the structure depends on the safety of the isolation system. And in case peak base displacement exceeds the design base displacement during an earthquake, rupture and/or buckling of isolators as well as bumping against stops around the seismic gap may occur. Therefore, obtaining accurate peak floor accelerations and peak base displacement is vital. However, although nominal design values for isolation system and superstructure parameters are calculated in order to meet target peak design base displacement and peak floor accelerations, their actual values may potentially deviate from these nominal design values. In this study, the sensitivity of the seismic performance of structures equipped with linear and nonlinear seismic isolation systems to the aforementioned potential deviations is assessed in the context of a benchmark shear building under different earthquake records with near-fault and far-fault characteristics. The results put forth the degree of sensitivity of peak top floor acceleration and peak base displacement to superstructure parameters including mass, stiffness, and damping and isolation system parameters including stiffness, damping, yield strength, yield displacement, and post-yield to pre-yield stiffness ratio.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2012년도 추계학술대회 논문집
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• pp.89-92
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• 2012

Marine diesel generator(D/G) set which is supported with resilient mounts for vibration isolation has been experienced the resonance problem by the main engine or propeller excitations and rigid body modes. Then the avoidance of resonance is difficult because the several excitations and 6 rigid body modes have to be considered simultaneously. In this paper, stiffness adjustable mounts was developed and proposed to control the natural frequencies of installed D/G set. Operating concept of the mount is that the total stiffness of mount can be changed according to the engagement of secondary rubber element in addition to primary one. The performance of mount was verified with the test rig and actual experiment in D/G set.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1993년도 가을 학술발표회 논문집
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• pp.207-212
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• 1993

When constructing highly precise production plants, for example, super LSI plants or semiconductor plants, it is important to take the necessary control countermeasures into consideration to obtain the working microvibration environment, which is directly related to product precision. Working environment of a clean room means vibration-free and there are only ultra-miro vibration which human cannot sense. In order to provide an place having a vibration-free working environment with only ultra-micro vibration it is necessary to posses a great number of vibration isolation technlogies, wide-ranging and abundant survey and teat data, and a high level of knowledge enabling comprehensive judgments to be made. In this study, experimental modal analysis is used to analyze the dynamic characteristics of double floor for vibration-proofing near apparatus which generate vibration. It is concluded that the double floor system with rubber pad inserted between floor panel and pedestal is good for vibration proof.

• International Journal of Aeronautical and Space Sciences
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• 제6권2호
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• pp.1-16
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• 2005

Adaptive control methods are studied for the Satellite to isolate vibration in spite of the nonlinear system dynamics and parameter uncertainties of disturbance. First, a centralized control scheme is developed based on the particle swarm optimization(PSO) algorithm and feedback theory to automatically tune controller gains. A simulation study of a 3 degree-of-freedom device was conducted to evaluate the performance of the proposed control scheme. Next, since a centralized control scheme is hard to construct model dynamics and not goad at performance when controller and systems environment are easily changed, a decentralized control scheme is presented to avoid these defects of the centralized control scheme from the point of view of production and maintenance. It is based on the adaptive control methodologies to find PID controller parameters. Experiment studies were conducted to apply the adaptive control scheme and evaluate the performance of the proposed control scheme with those of the conventional control schemes.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1994년도 Proceedings of the Korea Automatic Control Conference, 9th (KACC) ; Taejeon, Korea; 17-20 Oct. 1994
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• pp.123-128
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• 1994

This paper analyzes the dynamical modeling of high-rise building and the design of control systems for suppressing undesired vibrational motion at the top of the building originated by natural disturbances such as earthquakes, wind, etc. The control system is designed according to H$_{2}$ and H$_{\infty}$ robust control theories. The performance of the building with H$_{\infty}$ controller is analyzed in the time and frequency domains and the vibration isolation and robustness properties of H$_{\infty}$ and H$_{2}$ control systems are examined and compared. The design procedure, structure and properties of H$_{\infty}$ controllers are analyzed.zed.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2003년도 춘계학술대회논문집
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• pp.1128-1133
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• 2003

A gas driven heat pump (GHP) core design comprises internal combustion engine, compressors incorporated to a cooling/heating system, rubber mountings and belt transmissions. Main excitation farces are generated by an engine, compressors themselves and belt fluctuation. It leads to high vibration level of the mount that can cause damage of GHP elements. Therefore an appropriate design of the mounting system is crucial in terms of reliability and vibration reduction. In this paper oscillation of the engine mount is explored both experimentally and analytically. Experimental analysis of natural frequencies and operational frequency response of the GHP engine mounting system enables to create simplified model for numerical and analytical investigations. It is worked out criteria f3r vibration abatement of the isolated structure. Influence of bracket stiffness between engine and compressors, suspension locations and damper performance is investigated. Ways to reduce excitation forces and improve dynamic performance of the engine-compressor mounting system are considered from these analyses. Implementation of the proposed approach permits to choose appropriate rubber mountings and their location as well as joining elements design A phase matching technique can be employed to control forces from main exciters. It enables to changing vibration response of the structure by control of natural modes contribution. Proposed changes lead to significant vibration reduction and can be easily utilized in engineering practice.

• 동력기계공학회지
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• 제21권4호
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• pp.18-25
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• 2017

This paper deals with vibration control of a small mount with MR(Magneto-Rheological) fluid as a functional fluid mount for precision equipment of automobiles. Damping and stiffness coefficients of the mount with MR fluid are changed by variations of the applied magnetic field strength. We present the robust control scheme, based on a conventional sliding mode control theory, for the design of a stable controller that is capable of vibration control due to various disturbances such as impact and periodic excitations, and is insensitive to dynamic properties of the mount. We got stable controller by using Lyapunov stability theory. The controller is then realized by using a semi-active control condition in simulations. Chattering problem of the sliding mode control is eliminated by saturation function instead of signum function. The sliding mode control with Lyapunov stability theory is superior to passive and Sky-Hook control in performance.

• 한국소음진동공학회논문집
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• 제21권5호
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• pp.475-483
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• 2011

A hybrid electromagnetic actuator with an air mount is designed so as to achieve the desired isolation reduce the vibration efficiency on the floor vibration. The performance specification of the hybrid electromagnetic actuator is determined based on the vibration criterion for vibration-sensitive equipment. In the design stage of the electromagnetic actuator, the simple reluctance method is adapted to analyze magnetic circuits. The result is verified by finite element analysis using ANSYS Emag. Finally, in order to confirm the design performance, a dynamic characteristic test is carried out for the prototype of a hybrid electromagnetic actuator.