• Proceedings of the KSME Conference
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• 2001.11a
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• pp.465-470
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• 2001

In this study, the seismic analysis of rack structure with fluid-structure interaction is performed through use of the Finite Element Method(FEM) code ANSYS. Fluid-structure interaction can specify in terms of an hydrodynamic effect which is defined as the added mass per unit length divided by the area of the cross section. Using the Floor Response Spectrum(FRS) obtained through the time-history analysis, modal analysis and seismic analysis under Operating Basis Earthquake(OBE) and Safe Shutdown Earthquake(SSE) condition is carried out. The fluid-structure interaction effects on the rack structure are investigated.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.7 no.1
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• pp.108-115
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• 1995

An efficient model for the dynamic analysis of caisson breakwaters under impulsive wave loadings is presented. The caisson structure is. regarded as a rigid body, and the rubble mound foundation is idealized as virtual added masses, springs, and dampers using the elastic half-space theory. The frequency-dependent hydrodynamic added mass and damping coefficients are considered by using the time memory functions and added mass at infinite frequency. To simulate the permanent sliding phenomenon of the caisson, the horizontal spring is modeled as a nonlinear spring with plastic behaviors. Comparisons with experimental results show that the present model gives fairly good results. Sensitivity analysis is performed for the relevant parameters affecting the dynamic responses of a caisson breakwater. Numerical experiments are also carried out to investigate the applicability to the prediction of permanent sliding distance and critical weight of the caisson.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2010.04a
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• pp.192-195
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• 2010

본 논문에서는 해상 크레인과 중량물의 동적 거동을 시뮬레이션하기 위해, 유한 요소 정식화(finite element formulation)를 이용하여 해상 크레인의 붐(boom)을 탄성체로 모델링 하였다. 붐은 3차원 탄성 빔(beam) 요소로 가정하고, 각 요소의 변형에 의한 변위는 형상 함수(shape function)과 절점 좌표(nodal coordinate)를 이용하여 정의하였다. 변형 변위를 이용하여 탄성 붐의 강성 행렬(stiffnes matrix)을 유도하고, 탄성 변위를 포함하는 위치 벡터를 이용하여 질량 행렬을 유도한다. 해상 크레인과 중량물로 이루어진 운동 방정식에 탄성 붐을 포함하여 유연 다물체계(flexible multibody system) 운동 방정식을 구성한다. 외력으로는 선박 유체정역학적 힘, 유체동역학적 힘, wire rope의 장력, 중력 그리고 계류력(mooring force)이 고려되었다. 먼저 요소의 개수를 변경하며 탄성 붐의 동적 거동을 시뮬레이션 하여, 유한 요소 정식화를 이용한 모델링의 타당성을 검증하였다. 그리고 해상 크레인과 중량물의 동적 거동 시뮬레이션에 탄성 붐 모델을 적용하였다.

• Journal of KSNVE
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• v.7 no.4
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• pp.655-661
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• 1997

Base-isolation of a primary structure generally decrete the seismic response of its own and the secondary structure. It may cause an adverse effect on the seismic response of secondary system when the system is submerged and subject to a considerable hydrodynamic effect. In this paper, it is shown how, and how much, the base isolation of the primary structure can affect the secondary system response in extreme cases through dynamic analysis of a simplified coupled model for a submerged secondary system and a base-isolated primary structure. As an aseismatic design approach to reduce the response of the submerged system, optimization of the fluid gap, which controls the hydrodynamic mass effect, is performed. As an alternative approach in case where the control of fluid gap is unrealistic, application of base isolation to the submerged system is suggested. Effectiveness of various combinations of the primary base and secondary base isolations are compared.

• Journal of KSNVE
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• v.10 no.2
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• pp.280-290
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• 2000

The paper deals with vibration suppression and dynamic stability of a vertical cantilevered pipe conveying an internal flowing fluid and having an attached mass. Real pipe systems may have some valves or mechanical attached parts, which can be regarded as attached lumped masses. The effect of attached mass on the dynamic stability of a cantilevered pipe conveying fluid is investigated for different locations and magnitudes of the attached mass. The flow rate was controlled through motor pump output and measured by a flow meter. Experimental resutls in the vicinity of flutter fluid velocity were compared with theoretical predictions. It has been found that the experimental results are in substantial agreement with the theoretical predictions. Finally, in order to suppress the vibration of the pipe subjected to a disturbance, and control technique using an internal flowing fluid is introduced.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.12 no.7
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• pp.550-556
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• 2002

The vibrational system of this study is consisted of a cantilever pipe conveying fluid. the moving mass upon it and an attacked tip mass. The equation of motion is derived by using Lagrange equation. The influences of the velocity and the inertia force of the moving mass and the velocities of fluid flow in the pipe haute been studied on the dynamic behavior of a cantilever pipe by numerical method. As the velocity of the moving mass increases, the deflection of cantilever pipe conveying fluid is decreased. Increasing of the velocity of fluid flow make the amplitude of cantilever pipe conveying fluid decrease. The deflection of the cantilever pipe conveying fluid is increased by moving masses. After the moving mass passed upon the cantilever pipe, the amplitude of pipe is influenced due to the deflection of pipe tilth the effect of moving mass and gravity.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.11 no.6
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• pp.208-215
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• 2001

The paper presents both theoretical and experimental study fur dynamic instabilities of a vortical cantilevered pipe with two attached lumped masses conveying fluid. The two attached lumped masses can be considered as valves or some mechanical paras in real pipe systems. Eigenvalue behaviors depending on the flow velocity are investigated for the change of Positions and magnitudes of an attached lumped mass and a tip mass. In order to verify appropriate of numerical solutions, experiments were accomplished. Theoretical predictions have a good agreement with experimental ones.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.15 no.1
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• pp.59-68
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• 2002

The cylindrical Upper Guide Structure assembly of the reactor intervals wish the Core Support Barrel and the Inner Barrel Assembly is subjected to flow induced loads horizontally which include random pressure fluctuation due to turbulent flow and pump pulsation pressures. The purpose of this papers is to perform random vibration and harmonic response analyses fort flow induced loads. The dynamic response characteristics due to random turbulence and pump pulsation loads were evaluated using the lumped mass beam model. Especially the model considered the annulus effects due to water gaps existing between cylindrical structures such as the Upper Guide Structure Barrel, the Core Support Barrel, and the Inner Barrel Assembly. The effect of the Inner Barrel Assembly inside the Upper Guide Structure assembly was studied. The peak dynamic responses lot each loading condition due to the addition of IBA were affected by the natural frequencies of the structures. Therefore the peak dynamic responses of the structures should be conservatively obtained from evaluation of dynamic analysis for various loading conditions.

• Journal of the Korean Society for Precision Engineering
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• v.15 no.8
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• pp.126-134
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• 1998

본 연구에서는 회전운동을 제어하기 위한 새로운 작동기로서 전기장에 대하여 매우 빠른 응답특성을 갖고 있는 두 쌍의 실린더형 ER(electro-rheological) 클러치/브레이크 작동기를 제안하였다. 자체조성 된 ER유체의 빙햄특성 모델을 실험적으로 도출하였으며, 이와 연계한 작동기 모델을 구성하여 전기장에 따른 전달 및 제동 토크를 해석한 후 알맞은 크기의 클러치/브레이크 작동기를 제작하였다. 제작된 작동기의 동적특성(시상수 등)을 작동기 모델에 고려하기 위하여 계단입력 전기장에 따른 과도응답 실험을 클러치와 브레이크 모드에서 각각 수행하였다. 제안된 작동기의 응용성을 보이기 위하여 두쌍의 작동기로 구동되는 실험실 차원의 소형 와권식 세탁기 시스템을 구성한 후 동적지배방정식을 유도하다. 각 작동기와 연계된 PID제어기를 설계하여 세탁과 탈수시의 회전운동을 제어하였으며, 부하질량의 변화에 대한 작동기 시스템의 제어 효율성과 장시간 운전을 통한 제어 내구성 실험을 수행하였다.

• Transactions of the Korean Society of Mechanical Engineers
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• v.13 no.3
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• pp.362-372
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• 1989

It is important in design of vertical pumps to consider external excitation in addition to rotor vibration due to unbalance. In this study, a model of a vertical pump was developed for the analysis of its dynamic response. The vertical pump was modeled with lumped masses and springs which represent multi-cylindrical and rotor structure. A dynamic simulation program was developed and numerical calculation on the above mentioned problems were carried out.