• 한국해양공학회지
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• 제27권1호
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• pp.93-101
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• 2013

The incident bore impact loads acting on a tall structure is simulated using the refined Moving Particle Simulation (MPS) method. The particle method is more feasible and effective than conventional grid-based methods for the violent free-surface problems. In the present study, the simulation results for the temporal change of the hydrodynamic force on the structure and longitudinal velocity component around the structure are compared with the experiments (Radd and Bidoae, 2005). And the mitigation effects by installation of various obstacles in front of the main structure are investigated and discussed form the simulation results.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2000년도 춘계학술대회논문집B
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• pp.599-604
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• 2000

In order to study unsteady aerodynamic loads on high speed trains passing by each other at the speed of 350km/h, three-dimensional flow fields around trains during the crossing event are numerically simulated using the three-dimensional Euler equations. The Roe's FDS with MUSCL interpolation is employed to simulate wave phenomena properly. An efficient moving grid system based on domain decomposition techniques is developed to analyze the unsteady flow field induced by the restricted motion of a train on a rail. The numerical simulations of the trains passing by on the double-track are carried out to study the effect of the train nose-shape, the train length and the existence of tunnel when the crossing event occur. Unsteady aerodynamic loads side force and drag force-acting on the train during the crossing are numerically predicted and anlayzed. It is found that the strength of the side force mainly depends on the nose-shape, and that of drag force on tunnel existence. And it is observed that the push-pull like impulsive force successively acts on each car and acts in different directions between the neighborhood cars. The maximum change of the impulsive force reaches about 3 tons. These aerodynamic force data are absolutely necessary for the evaluation of the stability of the high speed multi-car train. The results also indicate the effectiveness of the present numerical method for the simulation of unsteady flow field induced by the bodies in the relative motion.

• 대한기계학회논문집A
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• 제37권2호
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• pp.257-263
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• 2013

본 논문에서는 파력에너지를 전기에너지로 변환시키는 파력발전기를 다물체 동역학을 이용하여 모델링 하였으며, 계류시스템이 부유식 파력발전기에 미치는 영향에 대해서 분석하였다. 계류시스템이 파력발전기에 미치는 영향을 줄이기 위한 연구가 많이 이루어지고 있다. 구속방정식과 힘 요소를 이용하여 다물체 시스템을 모델링 하였으며, 3 차원 파랑하중을 적용하여 부유체에 작용하는 파력을 모델링 하였다. 파력발전기의 거동과 발전량을 분석하기 의해 상용 다물체 동역학 해석프로그램인 MSC/ADAMS 를 이용하였다. 계류시스템이 있을 때와 없을 때의 결과를 비교하였고, 특히 극한 파랑하중이 작용했을 때의 시뮬레이션을 통해 파력발전기의 안정성을 평가하였다.

• 한국해양공학회지
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• 제25권2호
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• pp.7-14
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• 2011

Numerical simulations were performed for the evaluation of wave and current loads on a fixed cylindrical substructure model for an ocean wind turbine using the ANSYS-CFX package. The numerical wave tank was actualized by specifying the velocity at the inlet and applying momentum loss as a wave damper at the end of the wave tank. The Volume-Of-Fluid (VOF) scheme was adopted to capture the air-water interface. An accuracy validation of the numerical wave tank with a truncated vertical circular cylinder was accomplished by comparing the CFD results with Morison's formula, experimental results, and potential flow solutions using the higher-order boundary element method (HOBEM). A parametric study was carried out by alternately varying the length and amplitude of the wave. As a meaningful engineering application, in the present study, three kinds of conditions were considered, i.e., cases with current, waves, and a combination of current and progressive waves, passing through a cylindrical substructure model. It was found that the CFD results showed reasonable agreement with the results of the HOBEM and Morison's formula when only progressive waves were considered. However, when a current was included, CFD gave a smaller load than Morison's formula.

• 한국지진공학회:학술대회논문집
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• 한국지진공학회 2003년도 춘계 학술발표회논문집
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• pp.174-181
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• 2003

The groundborne vibration from moving train loads in tunnels could cause damages on structures and make people uneasy. With an aim at developing basis for effective screening measures, this paper attempts to study the characteristics of propagation and attenuation of groundborne vibration from moving train loads in tunnels considering the effect of joints. The wave propagation problem is modeled by a commercial code FLAC and the results are compared to those from using a finite-element-based code DIANA. It is shown that the groundborne vibration is affected significantly by the location and direction of joints.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2008년도 정기 학술대회
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• pp.561-566
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• 2008

Recently, because of development of the high speed train technology, the vibration loads by train is significantly increased ever than before. This buried gas pipelines are exposed to both repeated impact loads, and, moreover, they have been influencing by vibration loads than pipeline which is not located under vehicle loads. The vibration characteristic of pipeline is examined by dynamic analysis, and variable is only train speed. Since an effect of magnitude of vibration loads is more critical than cover depth, as increasing the train speed, the vibration speed of buried pipelines is also increased. The slope of vibration velocity is changed by attenuation of wave, at train speed, 300 km/h. From the analysis results, the vibration velocity of pipelines is satisfied with the vibration velocity criteria which are established by Korea Gas Corporation. The results present operation condition of pipelines under rail loads has fully sound integrity based on KOGAS specification.

• 한국지반환경공학회 논문집
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• 제14권7호
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• pp.57-66
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• 2013

해안구조물의 기능은 파랑과 조류, 침식 등의 자연현상에 복잡하게 거동한다. 이러한 해안구조물의 재료는 파랑과 직접적으로 접하고 있으며 구조물의 안정성에도 직접적으로 영향을 주기 때문에 매우 중요하다. 이러한 이유로 해안구조물은 파랑하중을 받는 동안의 거동과 구조물의 설계기준이 지속적으로 요구되어왔다. 특히 파랑하중과 구조물의 상호작용을 고려한 설계기준 및 연구는 아직도 미흡한 실정이다. 이에 본 연구에서는 파랑하중으로 인한 해안구조물과 재료의 거동특성을 살펴보았으며, 파랑고에 의해 직접적인 영향을 받게 되는 것을 확인하였다.

• 한국해양공학회지
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• 제35권5호
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• pp.347-359
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• 2021

This study aims to evaluate the dynamic responses of the jacket-type offshore wind turbine using FAST software (Fatigue, Aerodynamics, Structures, and Turbulence). A systematic series of simulation cases of a 5 MW jacket-type offshore wind turbine, including wind-only, wave-only, wind & wave load cases are conducted. The dynamic responses of the wind turbine structure are obtained, including the structure displacement, rotor speed, thrust force, nacelle acceleration, bending moment at the tower bottom, and shear force on the jacket leg. The calculated time-domain results are transformed to frequency domain results using FFT and the environmental load with more impact on each dynamic response is identified. It is confirmed that the dynamic displacements of the wind turbine are dominant in the wave frequency under the incident wave alone condition, and the rotor thrust, nacelle acceleration, and bending moment at the bottom of the tower exhibit high responses in the natural frequency band of the wind turbine. In the wind only condition, all responses except the vertical displacement of the wind turbine are dominant at three times the rotor rotation frequency (considering the number of blades) generated by the wind. In a combined external force with wind and waves, it was observed that the horizontal displacement is dominant by the wind load. Additionally, the bending moment on the tower base is highly affected by the wind. The shear force of the jacket leg is basically influenced by the wave loads, but it can be affected by both the wind and wave loads especially under the turbulent wind and irregular wave conditions.

• Coupled systems mechanics
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• 제2권1호
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• pp.111-126
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• 2013

The structural design requirements of an offshore platform subjected to wave induced forces and moments in the jacket can play a major role in the design of the offshore structures. For an economic and reliable design; good estimation of wave loadings are essential. A nonlinear response analysis of a fixed offshore platform under structural and wave loading is presented, the structure is discretized using the finite element method, wave plus current kinematics (velocity and acceleration fields) are generated using 5th order Stokes wave theory, the wave force acting on the member is calculated using Morison's equation. Hydrodynamic loading on horizontal and vertical tubular members and the dynamic response of fixed offshore structure together with the distribution of displacement, axial force and bending moment along the leg are investigated for regular and extreme conditions, where the structure should keep production capability in conditions of the 1-yr return period wave and must be able to survive the 100-yr return period storm conditions. The result of the study shows that the nonlinear response investigation is quite crucial for safe design and operation of offshore platform.

• 대한조선학회논문집
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• 제30권4호
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• pp.112-126
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• 1993

본 논문에서는 선급규칙중 파랑하중 부분의 개정과 관련하여 선체종강도의 국제선급연합 통일규칙(IACS UR)을 검증하기 위하여 단기파랑하에서 비선형 파랑하중 해석을 수행하였고, 선체구조의 직접강도해석시에 사용하여야 할 지침으로 IACS WAVE DATA에 대한 검증을 수행하였다. 컨테이너선등과 같은 대형개구를 가진 선박의 응력을 구하기 위하여 수평전단력, 수평굽힘모멘트 및 비틂모멘트 산식을 일관성 있게 구하여 새로이 제시하였다. 또한 선체 외관에 작용하는 유체동압력을 선박의 길이 및 깊이방향에 대한 분포 산식으로 제시하였고 이를 타 선급 규칙과 비교, 검토하였다. 이상의 제시된 산식들은 각 선종, 크기 별로 17척 선박의 실선계산을 통하여 결정되었다. 이 산식들은 앞으로 선체구조부재 Scantling 산식이 결정되면 실선에 대한 적용계산을 통하여 검증될 것이다.