• Journal of the Korea institute for structural maintenance and inspection
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• v.21 no.6
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• pp.59-66
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• 2017

In the case of fluid storage structure, hydrostatic pressure acts on the structure due to fluid surge during an earthquake. At this time, hydrodynamic pressure of the fluid charge not only by the strength of the earthquake but also by the sloshing height of the fluid. Factors affecting the change of load include the size, width and height of the fluid storage structure and height of fluid, time-history shape, etc. This paper wanted to identify the relationship between the earthquake shape and fluid free surface shape. The sloshing height measured the height of the fluid by applying earthquake to a tank whose width 500mm and comparison of the experiment and analysis. In addition, the shape of the fluid free surface was measured while varying the shape of earthquake and effective of the shape of earthquake of the fluid was analyzed.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.25 no.4
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• pp.323-330
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• 2012

This study deals with the experiments of liquid dampers with multi cells whose vertical tubes are divided into several square columns for easily changing natural frequencies. Shaking table test is performed to verify control effectiveness of the dampers which are installed on a building structure. To design liquid dampers, a 64-story building structure is reduced to a SDOF structure with 1/20 of similitude laws based on acceleration. The structure model is made up to adjust its mass and stiffness easily, with separate mass and drive parts. Mass parts indicate real structure's weights and drive parts indicate real structure's stiffness with springs and LM guides. Manufactured liquid damper has 18 cells and its natural frequency ranges are 0.65Hz to 0.81Hz. Shaking table test is carried out with one way excitation to compare with only accelerations of a large-scale structure and a structure installed with liquid dampers. Control performance of the liquid damper is expressed by the transfer function from shaking table accelerations to the large-scale structure ones. Testing results show that the liquid damper reduced a large-scale structure's response by tuned natural frequencies.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1991.04a
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• pp.127-132
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• 1991

충격에 민감한 용기나 기계들은 운반이나 보관중에 받을 수 있는 진동충격 을 완화시키기 위해 충격 마운트를 이용하게 되며, 충격마운트는 용기나 기 계들이 허용하는 최대가속도와 이들이 취급되는 환경에 의해 적절히 선정되 어야 한다. 그러므로 내충격 설계는 최대 허용 가속도나 취급환경에 대한 사 양과 이 사양에 의한 충격 마운트의 선정, 그리고 선정된 내충격 시스템의 충격시험에 의한 오일 탬퍼의 결합용이 사용되기도 하지만 구조가 복잡하고 가격이 비싸서 대용량이 경우에만 국한되어 사용되고 있으며, 가장 경제적인 것은 방진고무를 사용한 것이다. 내충격 시스템은 일반적으로 큰 변형량을 요구하고 있으며, 방진고무의 경우 큰 변형에서는 hardening 스프링의 비선 형성을 가지고, 형상계수와 고무배합율에 따라 정적 스프링상수와 동적 스프 링상수가 큰 차이를 보이는 등, 설계상의 여러 제한이 있다. 그러나 방진고 무는 형상변화가 자유로우며 제작이 용이하기 때문에 이러한 장점을 이용하 면 저렴하고 다양한 용도의 충격마운트 제작에 효과적으로 사용될 수 있다. 본 논문에서는 원통형 콘테이너의 내충격 설계를 위해 충격사양에 의한 충 격마운트의 설계, 설계된 내충격 시스템의 충격시험에 의한 검증을 순차적으 로 실시하여, 방진고무를 이용한 충격마운트 설계기술을 제시함으로써, 이후 방진고무제품의 설계를 위한 자료 및 과정의 제정에 도움을 주고자 한다.

• Journal of the Earthquake Engineering Society of Korea
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• v.8 no.2
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• pp.45-53
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• 2004

In this paper, the stiffness and damping matrix are experimentally constructed using the structural modal information on frequencies, damping ratio and modal vectors, which are obtained by shaking table tests. Free vibration, harmonic and white noise vibration tests are performed. The acceleration of the shaking table was used as the input signal, and the corresponding accelerations of each floor were measured as output signals. The characteristics and limitations of modal information from each test are compared. The results of this study would be a basic resource of the analytical and experimental studies on the system identification of structures.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.15 no.1 s.94
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• pp.20-28
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• 2005

This paper addresses uncertainty issues encountered recently in measuring head vibration using the conventional 6-axis or 9-axis bite-bar model. Those conventional bite-bar models are shown to present insufficient information to evaluate a generalized motion of head vibration. In order to overcome such limit, a new theoretical measurement model that consists of four 3-axis linear accelerometers is suggested. It is shown to enable the measurement of three angular acceleration components and six second-order angular velocity-dependent terms. Those nine angular motion-related ones, in addition to the three linear acceleration terms at the origin, are found to make it possible to evaluate the generalized head vibration for a given position. To examine the feasibility of the proposed method, a newly designed 12-axis bite-bar was developed. Detailed experimental results obtained from the developed 12-axis bite-bar are demonstrated in this paper. They illustrate that the popular 6-axis bite-bar model yield about $4.0\%$ relative measurement uncertainty for the pitch component of head vibration, $14\%$ and $10\%$ relative measurement uncertainty for the roll and yaw components of head vibration, respectively. Furthermore, this paper proposes other uncertainty factors to be considered in the future.

• Journal of the Korean Geotechnical Society
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• v.27 no.12
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• pp.107-116
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• 2011

Rigid soil containers (or rigid boxes) are often used for 1g shaking table tests. The rigid boxes, however, do not accurately simulate the amplification of ground acceleration and phase difference of seismic motion in the model ground due to the confinement of shear deformation and the reflection of seismic wave at the box walls. Laminar soil containers (or laminar shear boxes) can simulate the free field motion at convincingly superior accuracy than the rigid ones. In this study, the soft ground is modeled for both types of boxes and is subjected to seismic loading using a 1g shaking table. The comparison of the results using the two types of soil containers illustrates that, in case of the rigid box, the ground acceleration shows non uniform distribution and the phase synchronization of input motion. Whereas, the dynamic behavior of the laminar shear box shows good agreement with the free field behaviors such as the amplification of ground acceleration and the occurrence of phase difference.

• Journal of the Korea institute for structural maintenance and inspection
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• v.20 no.4
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• pp.27-34
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• 2016

A new algorithm for determining optimal accelerometer locations is proposed by using a frequency-domain Hankel matrix which is much simpler to construct than a time-domain Hankel matrix. The algorithm was examined through simulation studies by comparing the outcomes with those from other available methods. To compare and analyze the results from different methods, a dynamic analysis was carried out under seismic excitation and acceleration data were obtained at the selected optimal sensor locations. Vibrational amplitudes at the selected sensor locations were determined and those of all the other degrees of freedom were determined by using a spline function. MAC index of each method was calculated and compared to look at which method could determine more effective locations of accelerometers. The proposed frequency-domain Hankel matrix could determine reasonable selection of accelerometer locations compared with the others.

• Journal of the Society of Naval Architects of Korea
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• v.37 no.1
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• pp.67-81
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• 2000

An accurate and efficient numerical method for two-dimensional nonlinear radiation problem has been developed. The wave motion due to a moving body is described by the assumption of ideal fluid flow, and the governing Laplace equation can be effectively solved by the higher-order boundary element method with the help of the GMRES (Generalized Minimal RESidual) algorithm. The intersection or corner problem is resolved by utilizing the so-called discontinuous elements. The implicit trapezoidal rule is used in updating solutions at new time steps by considering stability and accuracy. Traveling waves caused by the oscillating body are absorbed downstream by the damping zone technique. It is demonstrated that the present method for time marching and radiation condition works efficiently for nonlinear radiation problem. To avoid the numerical instability enhanced by the local gathering of grid points, the regriding technique is employed so that all the grids on the free surface may be distributed with an equal distance. This makes it possible to reduce time interval and improve numerical stability. Special attention is paid to the local flow around the body during time integration. The nonlinear radiation force is calculated by the "acceleration potential technique". Present results show good agreement with other numerical computations and experiments.

• Journal of the Korean Society of Industry Convergence
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• v.6 no.3
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• pp.261-266
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• 2003

이 논문에서는 반능동 진동 흡수기를 통합 시트/섀시 현가 장치에 확대, 적용하여 그 성능을 조사하였다. 통함 현가시스템의 성능분석을 위해 집중 인체질량과 함께 실험적으로 입증된 한 비선형 시트 쿠션 모델을 도입하였다. 또한 3 자유도 시트/섀시 현가시스템의 효과적인 진동제어를 위해 리아푸노브 바이스테이트 제어법칙을 사용하였다. 시뮬레이션결과 반능동 통합 현가장치는 시트 쿠션 모델과 관계없이 운전자의 승차감과 관련 있는 시트의 절대가속도 크기와 시트쿠션의 시트 트랙에 대한 상대변위를 상당히 감소시킬 수 있음을 알 수 있었다. 그러나, 주로 사용되어온 선형 쿠션 모델을 사용한 경우보다 비선형쿠션 모델을 사용한 경우의 제진성능이 약간 저조함을 알 수 있었다. 따라서, 자동차 시트 설계시 성능분석을 위해서는 실제의(비선형의) 시트 쿠션 특성을 적용해야 함을 알 수 있다.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1990.10a
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• pp.143-147
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• 1990

자동차는 주행시에 노면가진으로 인하여 진동을 받게 되는 데 이러한 진동 은 운전자의 승차감을 저하시킬 뿐만 아니라 화물과 차량 부품을 파손시키 는 원인이 되기도 한다. 노면가진력은 주로 현가장치를 통하여 차량에 전달 되어 차량의 진동을 유발하게 되므로 승차감을 향상시키려면 노면가진을 효 과적으로 차단할 수 있도록 현가장치를 설계하여야 한다. 이를 위하여 본 논 문에서는 차량을 현가장치의 형식에 따라 3가지 종류로 구분한 다음 각각을 12자유도로 모델링하여 노면이 불규칙(random)한 도로를 주행할 때의 승용 차의 진동을 해석하고, 현가스프링의 강성과 쇼크 압소바의 감쇠 값이 자체 수직 가속도 유효치(rms value)와 현가장치 유효행정(rms stroke length)에 미치는 영향을 분석하였다. 차량의 운동방정식은 현가장치의 비선형 특성을 고려하였기 때문에 미소 각 운동의 가정에도 불구하고 비선형 방정식이 된 다. 운동 방정식의 해는 4차 Runge-Kutta 적분법을 사용하여 수치해석으로 구하였다.