• Wind and Structures
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• 제17권3호
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• pp.317-343
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• 2013

When evaluating flutter instability, it is often assumed that incident wind is normal to the longitudinal axis of a bridge and the flutter critical wind speed estimated from this direction is most unfavorable. However, the results obtained in this study via oblique sectional model tests of four typical types of bridge decks show that the lowest flutter critical wind speeds often occur in the yaw wind cases. The four types of bridge decks tested include a flat single-box deck, a flat ${\Pi}$-shaped thin-wall deck, a flat twin side-girder deck, and a truss-stiffened deck with and without a narrow central gap. The yaw wind effect could reduce the critical wind speed by about 6%, 2%, 8%, 7%, respectively, for the above four types of decks within a wind inclination angle range between $-3^{\circ}$ and $3^{\circ}$, and the yaw wind angles corresponding to the minimal critical wind speeds are between $4^{\circ}$ and $15^{\circ}$. It was also found that the flutter critical wind speed varies in an undulate manner with the increase of yaw angle, and the variation pattern is largely dependent on both deck shape and wind inclination angle. Therefore, the cosine rule based on the mean wind decomposition is generally inapplicable to the estimation of flutter critical wind speed of long-span bridges under skew winds. The unfavorable effect of yaw wind on the flutter instability of long-span bridges should be taken into consideration seriously in the future practice, especially for supper-long span bridges in strong wind regions.

• 대한토목학회논문집
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• 제28권2A호
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• pp.197-205
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• 2008

본 연구에서는 광양-묘도 지역의 평균풍속을 추정하기 위하여, 일별 최대 풍속과 해당 방향에 대한 결합분포확률의 통계학적 해석에 극한값 확률분포 모델이 사용되었다. 이를 위하여, 교량 가설지점 인근의 기상관측소에 대한 일별 최대풍속 및 해당풍향의 데이터로부터 각각의 관측소에 대한 일별 최대기록의 빈도를 조사하였으며, 16방위 및 전방위에 대한 년 최대풍속의 표본을 추출하였다. 이러한 풍속기록은 Gumbel 및 Weibull 분포모델에 적용하였으며, 모멘트방법 및 최소제곱법 등을 통해 모수를 추정하였다. 또한, PPCC 검사를 통해 분포모델 및 모수의 적합 여부를 검사하였다. 적합 여부가 판단된 모수로부터, 해당 관측소별로 데이터의 표본 크기 및 교량 가설지점으로부터의 거리에 대한 요소를 고려하여 16방위 및 전방위에 대한 년 최대풍속을 추정하였다.

• Spatial Information Research
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• 제19권1호
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• pp.13-19
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• 2011

도시화가 진행됨에 띠라 고층아파트와 고층빌딩 등 지형지물의 변화가 많이 일어나고 있다. 지형지물의 변화는 강풍 발생의 원인으로 작용하며, 풍속은 풍상측 지형지물의 영향으로 같은 속도의 바람이 붙어올지라도 그 값이 증가 또는 감소한다. 설계기준에서는 이러한 변화를 풍속고도분포계수로 정의하고, 지표면조도에 따라 그 값을 산정하여 반영하도록 하고 있지만 현실에서는 설계자의 주관적 판단에 따라 지표면조도를 결정하야 풍속고도분포계수를 산정하고 있으며, 건설지점의 지표면조도를 구분하기 위한 연구와 자료 또한 부족한 실정이다. 본 논문에서든 최근 고층주거건물이 많이 건설된 지역을 대상으로 건축물의 수직높이에 따분 지표면조도를 GIS프로그램을 이용하여 정량적으로 구분함으로써 풍속 고도분포계수를 보다 합리적으로 산정하고자 한다. 풍하중을 고려한 구조물 설계 시 본 연구에서 제안한 풍속고도분포계수 산정방법을 이용함으로써 설계의 합리성과 구조물의 안전성을 더 높일 수 있을 것이다.

• Wind and Structures
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• 제3권2호
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• pp.133-142
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• 2000

Engineered structures such as buildings and bridges in certain regions of the world need to be designed to withstand tropical cyclone winds, otherwise known as typhoons or hurricanes. In order to carry out this design, it is necessary to be able to estimate the maximum wind speeds likely to be encountered by the structure over its expected lifetime, say 100 years. Estimation of the maximum wind involves not only the overall strength of the tropical cyclone, but the variation of wind speed with radius from the centre, circumferential position, and with height above the ground surface. In addition, not only the mean wind speed, but also the gust factor must usually be estimated as well. This paper investigates a number of recent mathematical models of tropical cyclone structure and comments on their suitability for these purposes in a variety of scenarios.

• 한국태양에너지학회 논문집
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• 제32권2호
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• pp.95-104
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• 2012

This study purposed to predict wind energy for small size wind power generators at 50m above the ground in each area using mean wind speed data for 10 minutes collected from 2001 to 2011 by meteorological data in large cities having over 60% of 15 story (50m) or higher apartments including Seoul, Daejeon, Gwangju and Daegu representing the inland region, and Busan, Incheon and Ulsan representing the coastal region. In the results of analysis, we confirmed close agree ment between observatory weather data and probability density distribution obtained using Weibull's parameters, and this suggests that Weibull's parameter is applicable to the estimation of wind energy. Hourly output energy using the mean wind speed for 10 minutes and output energy obtained from Weibull's parameter showed an error less than 5%, and thus it was found that wind energy can be evaluated using Weibull's modulus.

• Wind and Structures
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• 제30권1호
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• pp.85-97
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• 2020

The accurate estimation of the buffeting response of a bridge pylon is related to the quality of the bridge construction. To evaluate the influence of wind field characteristics on the buffeting response of a pylon in a trumpet-shaped mountain pass, this paper deduced a multimodal coupled buffeting frequency domain calculation method for a variable-section bridge tower under the twisted wind profile condition based on quasi-steady theory. Through the long-term measurement of the wind field of the trumpet-shaped mountain pass, the wind characteristics were studied systematically. The effects of the wind characteristics, wind yaw angles, mean wind speeds, and wind profiles on the buffeting response were discussed. The results show that the mean wind characteristics are affected by the terrain and that the wind profile is severely twisted. The optimal fit distribution of the monthly and annual maximum wind speeds is the log-logistic distribution, and the generalized extreme value I distribution may underestimate the return wind speed. The design wind characteristics will overestimate the buffeting response of the pylon. The buffeting response of the pylon is obviously affected by the wind yaw angle and mean wind speed. To accurately estimate the buffeting response of the pylon in an actual construction, it is necessary to consider the twisted effect of the wind profile.

• 신재생에너지
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• 제10권1호
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• pp.41-49
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• 2014

For a proper valuation of wind power project, it is necessary to consider volatilities of key parameters such as annual energy production, electricity sales price, and long term interest rate. Real option methodology allows to calculate option values of these parameters. Volatilities to be considered in wind project valuation are 1) annual energy production (AEP) estimation due to meteorological variation and estimation errors in wind speed distribution, 2) changes in system marginal price (SMP), and 3) interest rate fluctuation of project financing which provides refinancing option to be exercised during a loan tenor for commercial scale projects. Real option valuation turns out to be more than half of the sales value based on a case study for a FIT scheme wind project that was sold to a financial investor.

• 전력전자학회논문지
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• 제15권4호
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• pp.309-318
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• 2010

본 논문은 풍력 터빈에서 발생되는 플리커를 추정하기 위하여 SVR(Support Vector Regression)을 이용한 시뮬레이션 모델을 제시한다. SVR 훈련을 위한 입력은 전압 변동이고 출력은 플리커로 설정한다. 오프라인 훈련을 통해 출력전압과 플리커의 관계가 도출된다. 제안된 기법은 플리커를 추정하는데 필요한 데이터 양을 줄이고 또 연산시간을 감소시킨다. 제안된 알고리즘은 시뮬레이션과 실험을 통해 그 타당성이 검증된다.

• Journal of the korean society of oceanography
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• 제38권3호
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• pp.135-142
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• 2003

Gas flux across the air-sea interface is often determined by the product of gas transfer velocity k) and the difference of concentrations in water and air. k is primarily controlled by wind stress on the air-sea interface, thus all parameterizations ofk involve wind speed, a rough indicator of wind stress, as one of the independent variables. We attempted to explore the spatial and temporal variations of k in the East (Japan) Sea using a database from Naet al. (1992). Three different parameterizations were employed: those of Liss and Merlivat (1986), Wanninkhof(1992), and Wanninkhofand McGillis (1999). The strong non-linear dependence of k on wind speed in all parameterizations leads us to examine the effect of time resolution, in which the binned wind speeds are averaged, on the estimation ofk. Two time resolutions of 12 hours (short-term) and one month (long-term) were chosen. The mean wind speeds were fed into the given parameterizations, resulting in six different transfer velocities of $CO_2$ ranging from 12 to 32 cm/h. In addition to the threefold difference depending on the choice of parameterization, the long-term average of wind speed results in a value ofk up to 20% higher than the short-term (12 hours) average of wind speed due to the non-Rayleigh wind distribution in the East (Japan) Sea. While it is not known which parameterization is more reliable, this study proposes that the time-averaged wind speed should not be used in areas where non-Ralyleigh wind distribution prevails such as the East (Japan) Sea. The net annual $CO_2$ flux was estimated using the value of k described above and the monthly ${\Delta}fCO_2$ of Oh et al. (1999); this ranges from 0.034 to 0.11 Gt-C/yr.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2009년도 제40회 하계학술대회
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• pp.1098_1099
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• 2009

In this paper, we present the estimation of wind turbine power generation using Cascade Architectures of Fuzzy Neural Networks(CAFNN). The proposed model uses the wind speed average, the standard deviation and the past output power as input data. The CAFNN identification process uses a 10-min average wind speed with its standard deviation. The method for rule-based fuzzy modeling uses Gaussian membership function. It has three fuzzy variables with three modifiable parameters. The CAFNN's configuration has three Logic Processors(LP) that are constructed cascade architecture and an effective optimization method uses two-level genetic algorithm. First, The CAFNN is trained with one-day average input variables. Once the CAFNN has been trained, test data are used without any update. The main advantage of using CAFNN is having simple structure of system with many input variables. Therefore, The proposed CAFNN technique is useful to predict the wind turbine(WT) power effectively and hence that information will be helpful to decide the control strategy for the WT system operation and application.