• Journal of KSNVE
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• v.7 no.5
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• pp.837-845
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• 1997

The dynamic interactions between the reactor vessel and the control element drive mechanisms (CEDMs) of a pressurized water reactor are studied with the simplified mathematical model. The CEDMs are modeled as multiple substructures having different masses and the reactor vessel as a single degree of freedom system. The explicit equation for the frequency responses of the multiple substructure system are presented for the case of harmonic base excitations. The optimum dynamic characteristics of the CEDMs are presented to reduce the dynamic responses of the reactor vessel. The mathematical model and its response equations are verified by finite element analysis for the detailed model of the reactor vessel and the CEDMs for the harmonic base excitations. It is finally shown that the optimal dynamic characteristics of the CEDM presented can be applicable for the aseismic design.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1991.04a
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• pp.41-45
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• 1991

구조 진동에 의해 발생하는 Relative Sound Power를 계산하는 문제가 최근 에 중요시되고 있다. 이 논문에서는 조화적인 집중하중에 대한 무한 탄성보 에서 방출하는 Relative Sound Power를 연구한다. Sound Power는 수치적으 로 적분되고 몇가지 인자들의 함수로써 적분인자를 표시하였다. Keitie와 Peng[2]는 진동하는 보로부터의 방출하는 Relative Sound Power에 대한 하 중 길이의 효과, 그리고 water 하중을 받는 보에서 방출하는 Acoustic radiation에 대한 Source 운동과 기초 강성의 효과를 연구하였다. 보의 진동 응답에서 light fluid loading과 heavy fluid loading에 의한 양쪽의 반응을 고 려한다. 보에는 기초 강성과 Damping 그리고 장력이 작용한다. water 하중 과 air 하중을 받는 보에서 Damping의 변화에 대한 보로부터 방출하는 relative sound power의 크기를 결정하였다. 일반적으로 인장력보다 압축력 이 작용할 때 relative sound power level이 크다는 것을 알고 있다. 실제로 인장력이나 압축력이 보에 작용할 때 relative sound power에 얼마나 영향을 미치는가를 계산하였다. 그리고 진동계로부터 방출하는 sound fluid loading 과 기초 강성에 기인한 복잡한 효과를 해석하였다. 이 논문의 목적은 강성계 수와 wavenumber 비, 그리고 fluid loading에 대한 sound power의 응답에 대하여 설명하고자 한다.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.23 no.2
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• pp.199-208
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• 2010

A friction damper installed at a building shows nonlinear behavior since its stick and slip states are occurred repeatedly depending on the amplitude of external loadings to dissipate input energy. Friction damping is existed for the building with a friction damper. In additionally viscous one is inherently included. Therefore, the building installed in such combined damping is quite involved to find the analytical solution. In this study, first, displacement and acceleration characteristics are identified based on the exact solution for a single-degree-freedom building with a friction damper having both friction and viscous damping. Second, in free vibration, the equivalent viscous damping ratio is obtained by the energy dissipation. Third, numerical analysis is carried out to find response configuration with various friction force ratios. Fourth, corresponding equivalent viscous damping ratio is derived with the finding that the response reaches into steady-state for both friction and viscous damped structure. It is deduced using balance of input external energy and output dissipation energy for steady-state response. Finally, the equivalent viscous damping ratios of free or harmonic vibration are verified through nonlinear analysis.

• Journal of the Korean Society for Precision Engineering
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• v.11 no.6
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• pp.75-85
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• 1994

주기함수의 외력을 갖는 버선형 시스템의 다양한 응답 특성을 구하기 위해 새로운 조화함수법(HBM)을 적용하였다. 새로운 조화함수법의 해는 비선형항을 선형항으로부터 따로 분리시킨 다음 같은 주파수 성분을 갖는 비선형 방정식들을 Newton-Raphosn법으로 풀어서 구하였다. 다양한 천이(Bifurcation) 특성을 해석적으로 판별하기 위하여 HBM의 해를 이용하여 구한 섭동 방정식의 Floquet 지수의 고유해를 사용하였다. 새로이 개발한 HBM과 천이 판별법을 1차원 비선형항을 갖는 구조물인 ALP(Articulated Loading Platform) 모델과 다차원인 비선 형 회전체 모델에 적용시켜 HBM의 해의 정확성과 이들 시스템의 천이 특성의 하나인 Chaos 존재를 확인 하였다.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.9 no.2
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• pp.20-25
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• 2010

A camera module is supported by a gimbal structure in collection equipment of image information. During flight, the gimbal system undergoes serious accelerations with wide frequencies. To get the correct images, the camera module must be stably vibrated under these conditions. If natural frequency unfortunately exists in a exciting frequency range, resonance occurs there. Hence, harmonic responses analysis is needed to know correct vibration characteristic of the gimbal system. Finite element analysis was performed to get an acceleration of the gimbal system by mode superposition after extracting mode shapes and natural frequencies. Considering damping ratio of 2%, the reponses of gimbal structure were calculated from excitations with a design frequency band. As results, a maximum acceleration transmissibility, which is the ratio of response to excitation, was obtained and it can be used to design the gimbal structure effectively.

• Journal of KSNVE
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• v.11 no.1
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• pp.89-95
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• 2001

This paper describes the natural frequencies obtained through FEA (Finite Element Analysis) and Numerical Analysis which uses the boundary conditions to each equation of motion and the consecutive conditions at each supporting point. And then. we studied on the optimal position determination of middle supporting points to maximize the natural frequency of a beam at 24 Models. We present the data of optimal condition for designing a beam.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2012.10a
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• pp.512-513
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• 2012

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2013.10a
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• pp.840-841
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• 2013

• Journal of the Korean Geotechnical Society
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• v.31 no.9
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• pp.53-68
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• 2015

Longitudinal strain is an important component of seismic design for buried pipelines. A design procedure which determines the wavelength from site natural period and shear wave velocity of the soil layer and closed-form solutions of pipelines under a harmonic motion is typically used in design. However, the applicability of the procedure has not yet been thoroughly investigated. In this paper, displacement-time histories extracted from 1D site response analyses are used in 3D shell-spring model to accurately predict the response of pipelines. The results are closely compared to those from the design procedure. The area of interest is East Siberia. Performing a site response analysis to determine site specific displacement time history is highlighted. The site natural period may be used to predict the predominant period of the acceleration time history, but cannot be used to estimate the predominant period of the displacement time history. If an accurate estimate of the predominant period of the displacement time history is provided, it is demonstrated that the design equation can be successfully used to predict the response of pipelines.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.15 no.2
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• pp.197-207
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• 2002

Energy dissipation capacity and earthquake responses of steel structures installed with unbonded braces(UB) were investigated. Parametric studies were performed for a single-degree-of-freedom structure under harmonic loads, and optimum yield strength of unbonded braces were derived. Nonlinear dynamic time history analyses were carried out to investigate the seismic response of multi-story model structures with UB having various size and strength. Various techniques were applied to determine proper story-wise distribution of UB in multi-story structures. The analysis results show that the maximum displacements of structures generally decrease as the stiffness of UB increases. However for some natural frequencies and seismic loads the maximum displacement and accumulated damage increases as the stiffness of UB increases.