• 한국해양공학회지
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• 제34권6호
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• pp.394-405
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• 2020

To assess the station-keeping performance of floating structures in the Arctic region, the ice load should be considered along with other environmental loads induced by waves, wind, and currents. However, present methods for performance evaluation in the time domain are not effective in terms of time and cost. An ice load generation module is proposed based on the experimental data measured at the KRISO ice model basin. The developed module was applied to a time domain simulation. Using the results of a captive model test conducted in multiple directions, the statistical characteristics of ice loads were analyzed and processed so that an ice load corresponding to an arbitrary angle of the structure could be generated. The developed module is connected to commercial dynamic analysis software (OrcaFlex) as an external force input. Station-keeping simulation in the time domain was conducted for the same floating structure used in the model test. The mooring system was modeled and included to reflect the designed operation scenario. Simulation results show the effectiveness of the proposed ice generation module and its application to station-keeping performance evaluation. Considering the generated ice load, the designed structure can maintain a heading angle relative to ice up to 4°. Station-keeping performance is enhanced as the heading angle conforms to the drift direction. It is expected that the developed module will be used as a platform to verify station-keeping algorithms for Arctic floating structures with a dynamic positioning system.

• 대한전기학회논문지
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• 제34권12호
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• pp.491-497
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• 1985

An applicaton of the linear optimal control theory to the problem or load follow control in pressurized water reactors (PWR) is investigated. In order to perform the steady-state and load follow operation in PWR, a nonlinear model for the reactor and steam generator is derived and linearized at 50% rated power. Simulation tests are performed for 10% demanded load. Comparing the dynamic response of the newly developed optimal load follow controller with those of the integral error feedback controller proposed by Yang, the rise time of dynamic response of the former is about 15 seconds faster than those of the latter, thus the results indicate that the fast response of the optimal load follow controller is verified. The results of this work are directly applicable to the design of the load follow control systems for commercially operated PWRs.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2005년도 춘계학술대회
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• pp.353-356
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• 2005

We developed a dynamic model of PEM fuel cell system which can analyze its transient response to dynamic load current. System components such as compressor, air cooler, humidifier, and stack were modeled based on their dynamic equations and performance maps by using Matlab Simulink platform. Through this simulation model, dynamic characteristics of fuel cell system including oxygen excess rat io, stack voltage, and system efficiency were shown. In addition to that, we briefly analyzed the humidity effect on cathode pressure and system efficiency, expecting that this model can be further used to optimize fuel cell system parameters just like operating pressure and temperature, humidity and oxygen excess ratio.

• 한국정밀공학회지
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• 제15권3호
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• pp.150-156
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• 1998

In this paper, a 3-DOF(Degree Of Freedom) rigid body model is developed for dynamic analysis of a hydrostatic table. The dynamic coefficients, stiffness and damping constant of each pad are calculated from the mass flow continuity condition. The validity of this model is examined in theoretical and experimental method. The dynamic behavior when mass unbalances and local variations of stiffness and damping of pads present is analyzed for real applications of hydrostatic table. Since the theoretical and experimental results show goof agreement. it can be said that the 3-DOF rigid body model is useful for the dynamic model of the table. The analysis reveals that the pitching motion is the dominant mode of vibration, It also reveals that unbalanced loads can increase amplitude of tilting motion and reduce natural frequencies and damping capacity of the hydrostatic table.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2003년도 춘계학술대회논문집
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• pp.336-341
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• 2003

In this paper, resonance durability analysis technique is presented for the fatigue life assessment considering dynamic effect of a vehicle system. In the resonance durability analysis, the frequency response and the dynamic load on frequency domain are used. Multi-body dynamic analysis, finite element analysis, and fatigue life prediction method are applied for the virtual durability assessment. To obtain the frequency response and the dynamic load, the computer simulations running over typical pothole and Belgian road are carried out by utilizing vehicle dynamic model. The durability estimations on the rear suspension system of the passenger car are performed by using the presented technique and compared with the quasi-static durability analysis. The study shows that the fatigue life considering resonant frequency of vehicle system can be effectively estimated in early design stage.

• 소음진동
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• 제10권4호
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• pp.692-701
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• 2000

Escalators are widely used for mass transportation in public places. In recent years, strict requirements on the comfort and reliability for the public transportation have drawn a great attention to vibration in escalators. This paper presents a dynamic model for escalators to be used for the analysis and design of low vibration escalators. The dynamic model is developed so as to reflect the physical observation on peculiar characteristics in escalators such as the difference between up-moving and down-moving, and the abnormal vibration affected by the load applied. For validation of the dynamic model developed, experimental results are compared with numerical results from the model. The numerical study shows that the developed model may be useful for the analysis and design of escalator systems.

• 한국지반공학회지:지반
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• 제12권2호
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• pp.19-32
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• 1996

시간영역의 지진 가속도-시간 이력을 주파수 영역의 courier 진폭-주파수 이력으로 변화시키는 Trifunac의 경험적 모델을 기초로 하여 지진 관측소에서 측정된 임의 규모의 실제 지진기록들을 필요한 규모의 지진기록으로 유사화시키는 지진 확대 (scaling) 기법을 제안하였다. 또한, 지진 규모(M) 5.6의 지진기록을 이용하여 지진 규모(M) 8.0의 유사지진을 작성하여 동적 재하 시험 장치에 적용가능하도록 하였다. 지진 확대 (scaling) 기법은 MMI(modified mercalli intensity), 지진기록 부지의 조건,진앙거리,지진 가속도 성분의 방향, 해석의 신뢰도 등을 고려할 수 있으며, 다양한 지진 기록들에 적용가능하였다.유사지진은 수평방향의 성분들만을 고려하여 작성되었다. 압력토조내에 설치된 모형인장말뚝과 개단압출말뚝에 대한 유사지진 진동에 의한 동적 말뚝재하시험이 가능하였다. 정적 말뚝재하시험시 인장말뚝과 압축말뚝의 거동은 매우 상이하였는데, 인장말뚝은 2~3회의 급작스런 미끄러짐 변위를 수반하였다. 또한, 유사 지진 진동중 인장말뚝과 개단압축말뚝의 거동특성은 매우 상이하였으며, 지지력 감소특성도 크게 달랐다.

• 한국군사과학기술학회지
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• 제25권1호
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• pp.9-22
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• 2022

A fighter performing a reconnaissance mission is equipped with a pod that drives optical/infrared sensors for acquiring and identifying target information on the lower part of the fuselage. Due to the nature of the reconnaissance mission, the fighter performs high speed evasive maneuvers, and the resulting load should be considered importantly for the development of the pod. This paper concerns a numerical investigation into the inertial and aerodynamic loads of the airborne pod of high performance aircrafts. For the aerodynamic load analysis, the pylon and pod shapes are added to the fighter 3D model, and the commercial software was used for static and dynamic analysis. Considering the practical mission conditions, the common/extreme conditions were established respectively in the static and dynamic situations of pods and the driving torque could be tripled under dynamic conditions. In the analysis of inertia load, a 3-DOF model considering roll and turning maneuvers was derived by the Lagrangian method, and then the numerical integration method was applied to the analysis. As a results, it was conformed that the inertia load was generally induced at a low level compared to the aerodynamic load, but depending on the unbalance mass condition of the pod, the inertia load cannot be negligible.

• Structural Engineering and Mechanics
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• 제54권3호
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• pp.561-577
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• 2015

The main objective of this paper is to study the dynamic load allowance (DLA) calculation methods for bridges according to the dynamic response curve. A simply-supported concrete bridge with a smooth road surface was taken as an example. A half-vehicle model was employed to calculate the dynamic response of deflection and bending moment in the mid-span section under different vehicle speeds using the vehicle-bridge coupling method. Firstly, DLAs from the conventional methods and code provisions were analyzed and critically evaluated. Then, two improved computing approaches for DLA were proposed. In the first approach, the maximum dynamic response and its corresponding static response or its corresponding minimum response were selected to calculate DLA. The second approach utilized weighted average method to take account of multi-local DLAs. Finally, the DLAs from two approaches were compared with those from other methods. The results show that DLAs obtained from the proposed approaches are greater than those from the conventional methods, which indicate that the current conventional methods underestimate the dynamic response of the structure. The authors recommend that the weighted average method based on experiments be used to compute DLAs because it can reflect the vehicle's whole impact on the bridge.

• 한국안전학회지
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• 제31권4호
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• pp.97-103
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• 2016

This study investigates effects of partially earth anchored cable system on the structural safety for a long-span cable-stayed bridge under dynamic loads such as seismic and wind load. For a three span cable-stayed bridge with a main span length of 810 m, two models are analyzed and compared; one is a bridge model with a self anchored cable system, the other is a bridge model with a partially earth anchored cable system. By performing multi-mode spectrum analysis for a prescribed seismic load and multi-mode buffeting analysis for a fluctuating wind component, the structural response of two models are compared. From results, the partially earth anchored cable system reduce the maximum pylon moment by 66% since earth anchored cables affect the natural frequencies of girder vertical modes and pylon longitudinal modes. In addition, the girder axial forces are decreased, specially the decrement of the axial force is large in seismic load, while girder moment is slightly increased. Thus, the partially earth anchored cable system is effective system not only on reduction of girder axial forces but also improvement of structural safety of a cable-stayed bridge under dynamic loads such as seismic and wind loads.