• Title/Summary/Keyword: 동하중 계수

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Evaluation of Dynamic Thrust Under Wind Shear in Wind Turbine Below Rated Wind Speed (정격풍속 이하에서 풍력터빈의 윈드쉬어 추력 동하중 개발)

  • Lim, Chae-Wook
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.40 no.4
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    • pp.407-414
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    • 2016
  • As wind turbines are getting larger in size with multi-MW capacity, the blades are getting longer, over 40 m, and hence the asymmetric loads produced during the rotation of the rotor blades are increasing. Some factors such as wind shear, tower shadow, and turbulence have an effect on the asymmetric loads on the blades. This paper focuses on a method of modeling the dynamic load acting on a blade because of thrust variation under wind shear. A method that uses thrust coefficient is presented. For this purpose, "wind shear coefficient of thrust variation" is defined and introduced. Further, we calculate the values of the "wind shear coefficient of thrust variation" for a 2 MW on-shore wind turbine, and analyze them for speeds below the rated wind speed. Then, we implement a dynamic model that represents the thrust variation under wind shear on a blade, using MATLAB/Simulink. It is shown that it is possible to express thrust variations on three blades under wind shear by using both thrust coefficient and "wind shear coefficient of thrust variation."

SEQUENTIAL ALGORITHMS FOR DYNAMIC STRUCTURAL IDENTIFICATION (구조물의 동특성 추정을 위한 순차적 기법)

  • Yun, C-B.;Lee, H-J.
    • Proceedings of the Computational Structural Engineering Institute Conference
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    • 1992.04a
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    • pp.13-18
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    • 1992
  • 구조물의 동적실험을 통하여 얻은 하중과 거동에 대한 시간기록을 분석하여, 구조계의 동 특성계수들을 추정하는 기법에 대하여 연구하였다. 실험과정 및 해석모형과정의 오차를 고려하기 위하여, 하중기록과 구조거동기록간의 관계를 추계론적 자동회기 및 이동평균모형(Stochastic Auto-Regressive and Moving-Average (ARMAX) Model)음 사용하여 모형화하였다. 미지의 ARMAX 계수행렬들은 순차적 예측오차기법을 사용하여 추정하였으며, 계수추정기법의 효율성을 증진시키기 위하여, Exponential Data Weighting, Global Data Weighting 및 Square Root Estimation 기법을 활용하였다. 다중거동측정계의 예제해석을 통하여 이의 효율성을 분석하였다.

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Dynamic Load Factor for Floor Vibration due to Lively Concerts (공연하중에 의한 바닥진동 설계용 동하중계수)

  • Hong, Kap Pyo;Yoon, Kwang Sup
    • Journal of Korean Society of Steel Construction
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    • v.14 no.6
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    • pp.721-728
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    • 2002
  • Modern structrues are being built using high-strength and light-weight construction materials resulting in decreased structural mass and damping properties. Rhythmic activities such as jumping, dancing and clapping during lively concerts can produce excessive vibration of steel structures. In this study, dynamic load factors that occur during lively concerts were presented through vibration test and real-time monitoring of an existing concert hall. The vibration test included modal analysis and jumping test according to the forcing frequencies and the number of participants. Dynamic load foactors were acquired directly from peak acceleration responses of each harmonics. Comparing NBCC 1995, the 3rd harmonic must be included in the design of concert halls. Dynamic load factors must be increased as a result of the vibration test.

Dynamic Interface Friction Behavior Between Soils and Construction Material(Steel) (조립토와 건설재료(steel)사이의 동마찰계수)

  • Kim, Dae-Sang
    • Proceedings of the Korean Geotechical Society Conference
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    • 2001.03a
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    • pp.461-468
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    • 2001
  • 지진등에 의해 유발된 동 하중에 의한 지반-구조물 계의 응답은 지반-구조물사이의 경계에서의 마찰특성과 미끄러짐에 의해 크게 영향을 받게 된다 본 논문에서는 진동대(Shaking table)를 이용하여 조립토와 건설재료(Steel)의 경계에서 지반으로부터 지중구조물에 전달되는 전단응력 의 전달정도를 파악하기 위한 실험을 실시하였다. 본 실험에서 설정한 미끌어짐속도 범위내에서는 미끄러짐속도 변화에 따른 조립토와 건설재료(Steel)사이의 동마찰계수의 변화가 작다는 사실이 관찰되었다. 그리고 조립토의 평균유효입경의 변화가 동마찰계수에 미치는 영향도 함께 조사되었다. 또한 이 동마찰계수를 같은 조립토에 대한 평면변형률시험을 통해 얻어진 최대내부마찰각으로부터 구한 마찰계수와 비교하여 정량화하였다.

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Dynamic Response Analysis of 2.5MW Wind Turbine Gearbox with Flexible Pins (유연핀을 적용한 2.5MW급 풍력발전기용 기어박스의 동응답 해석)

  • Cho, Jin-Rae;Jeong, Ki-Yong
    • Journal of the Computational Structural Engineering Institute of Korea
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    • v.29 no.1
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    • pp.37-44
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    • 2016
  • This study is concerned with the numerical investigation of dynamic characteristics of 2.5MW-class wind turbine gearbox in which the misalignment improvement of plenary gear shafts by the flexible pins and the dynamic impact response are analyzed by the finite element method. The tooth contact between gears is modelled using the line element having the equivalent tooth stiffness and the contact ratio to accurately and effectively reflect the load transmission in the internal complex gear system. The equivalent tooth stiffness is calculated by utilizing the tooth deformation analysis and the impulse torque is applied to the input shaft for the dynamics response characteristic analysis. Through the numerical experiments, the equivalent tooth stiffness model was validated and the misalignment improvement of planetary gear shafts was confirmed from the comparison with the cases of fixed shafts at one and both ends.

Identification of Linear Structural Systems (선형 구조계의 동특성 추정법)

  • 윤정방
    • Computational Structural Engineering
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    • v.2 no.4
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    • pp.111-116
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    • 1989
  • Methods for the estimation of the coefficient matrices in the equation of motion for a linear multi-degree-of-freedom structure are studied. For this purpose, the equation of motion is transformed into an auto-regressive and moving average with auxiliary input(ARMAX) model. The ARMAX parameters are evaluated using several methods of parameter estimation : such as the least squares, the instrumental variable, the maximum likelihood and the limited information maximum likelihood methods. Then the parameters of the equation of motion are recovered therefrom. Numerical example is given for a 3-story building model subjected to an earthquake exitation.

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Molecular Dynamics Study on Mechanical Behavior and Load Transfer of CNT/PET Nanocomposites : the Effects of Covalent Grafting (탄소나노튜브/폴리에스터 복합재의 역학적 거동과 하중전달에 관한 분자 동역학 전산모사 : 그래프팅 가공의 영향)

  • Jin, Juho;Yang, Seunghwa
    • Composites Research
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    • v.30 no.3
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    • pp.193-201
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    • 2017
  • Molecular dynamics simulation and the Mori-Tanaka micromechanics study are performed to investigate the effect of the covalent grafting between CNT and polyester on the mechanical behavior and load transfer of nanocomposites. The transversely isotropic stress-strain curves are determined through the tension and shear simulations according to the covalent grafting. Also, isotropic properties of randomly dispersed nanocomposites are obtained by orientation averaging the transversely isotropic stiffness matrix. By addressing the grafting, the transverse Young's modulus and shear moduli of the nanocomposites are improved, while the longitudinal Young's modulus decreases due to the degradation of the grafted CNT.

Dynamic Friction Behavior of Interfaces Between Granular Materials and Steel (조립토와 건설재료(steel)사이의 동마찰계수)

  • 김대상
    • Journal of the Korean Geotechnical Society
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    • v.17 no.3
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    • pp.33-39
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    • 2001
  • 지진 등에 의해 유발된 동 하중에 의한 지반-구조물 계의 응답은 지반-구조물사이의 경계에서의 마찰특성과 미끄러짐에 의해 크게 영향을 받게 된다. 본 논문에서는 진동대(Shaking table)를 이용하여 조립토와 건설재료(steel)와의 경계에서 지반으로부터 지중구조물에 전달되는 전단응력의 전달정도를 파악하기 위한 실험을 실시하였다. 본 실험에서 설정한 미끄러짐속도 범위 내에서는 미끄러짐속도 변화에 따른 조립토와 건설재료(steel) 사이의 동마찰계수의 변화가 작다는 사실이 관찰되었다. 그리고 조립토의 평균유효입경의 변화가 동마찰계수에 미치는 영향도 함께 조사되었으며, 이 동마찰계수를 같은 조립토에 대한 평면변형률시험을 통해 얻어진 최대내부마찰각으로부터 구한 마찰계수와 비교하여 정량화하였다.

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Study on the Static and Dynamic Stiffness Coefficients of Rubbers Connector by Using Finite Element Method (유한요소법을 이용한 고무 연결요소의 정-동강성 계수에 관한 연구)

  • 박노길;박성태
    • Computational Structural Engineering
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    • v.8 no.2
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    • pp.103-113
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    • 1995
  • Since the mechanical properties of the rubber connectors used in the vehicle structures are sensitive on the dynamic characteristics of the system, they must be exactly evaluated. In this paper, both finite deformation theory and Hookean model are considered to calculate the stiffness coefficients of rubber connectors. An expert system is developed by using finite element method. When the equivalent stiffness coefficients on the same kinds of isolators used in actual vehicles were emperically examined, the results were largely dispersed due to the lack of the quality control on the material properties. To compensate the errors caused by the mathematical modeling and the mechanical properties, a practical method which identifies the shear and bulk moduli of rubber with the experimented overall force-deformation curves is suggested and applied to the engine isolators of vehicle.

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Investigation of Impact Factor and Response Factor of Simply Supported Bridges due to Eccentric Moving Loads (이동하중의 편측재하에 따른 단순교의 충격계수 및 응답계수 변화 분석)

  • Hong, Sanghyun;Roh, Hwasung
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.22 no.6
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    • pp.105-113
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    • 2018
  • The proposed model to predict the bridge load carrying capacity uses the impact response spectrum. The spectrum is based on Euler-Bernoulli beam and the center of the bridge width for the moving load location. Therefore, it is necessary to investigate the eccentric moving load effects on the impact factor and response factor. For this, this study considers 10 m width and two-lane simply supported slab bridges and performs the moving load analysis to investigate the variations of peak impact factor and corresponding response factor. The numerical results show that the eccentric load increases both the static and dynamic displacements, but the impact factor is decreased since the incremental amount of static displacement is bigger than that of dynamic displacement. However, the difference of the impact factors between the center and eccentric loadings is small showing less than 0.5%p. In the response factor, the eccentric loading increases both the static and dynamic response factors, compared to the center loading. The difference of the response factor is only 0.18%p. It shows that the eccentric loading has very small effects on the response factor, thus the impact factor response spectrum which is generated based on the center moving load can be used to determine the response factor.