• Wind and Structures
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• 제9권3호
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• pp.179-191
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• 2006

Parent wind data are often acknowledged to fit a Weibull probability distribution, implying that wind epoch maxima should fall into the domain of attraction of the Gumbel (Type I) extreme value distribution. However, observations of wind epoch maxima are not fitted well by this distribution and a Generalised Extreme Value (GEV) analysis leading to a Type III fit empirically appears to be better. Thus there is an apparent paradox. The reasons why advocates of the GEV approach seem to prefer it are briefly summarised. This paper gives a detailed analysis of the errors involved when the GEV is fitted to epoch maxima of Weibull origin. It is shown that the results in terms of the shape parameter are an artefact of these errors. The errors are unavoidable with the present sample sizes. If proper significance tests are applied, then the null hypothesis of a Type I fit, as predicted by theory, will almost always be retained. The GEV leads to an unacceptable ambiguity in defining design loads. For these reasons, it is concluded that the GEV approach does not seem to be a sensible option.

• Wind and Structures
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• 제19권2호
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• pp.169-184
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• 2014

This paper presents a method of estimation of extreme wind. Assuming the extreme wind follows the Gumbel distribution, it is modeled through fitting an exponential function to the numbers of storms over different thresholds. The comparison between the estimated results with the Improved Method of Independent Storms (IMIS) shows that the proposed method gives reliable estimation of extreme wind. The proposed method also shows its advantage on the insensitiveness of estimated results to the precision of the data. The volume of extreme storms used in the estimation leads to more than 5% differences in the estimated wind speed with 50-year return period. The annual rate of independent storms is not a significant factor to the estimation.

• 전산구조공학
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• 제2권2호
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• pp.62-72
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• 1989

본 연구는 확률에 기초한 한국의 기본 설계풍속 추정을 위한 합리적인 방법을 제시하고 위험도에 기초한 전국의 설계풍속지도를 제안한다. 본 논문에서는 장기기록 지역의 계절풍 연 최대 풍속자료와 단기기록 지역의 계절풍 월 최대 풍속자료의 극치 Type I 분포 모형에 대한 적합성을 검토하였고, 극치 태풍 풍속 분포 추정에서는 Monte-Carlo 시뮬레이션을 이용하여 간접적인 해석방법이 적용되었다. 태풍과 계절풍에 대한 기본 설계풍속은 두개 분포의 적(product)으로 된 혼합모형에서 구한다. 본 연구 결과로부터 제안된 모형과 방법은 현재 한국에서 가용한 단기기록 풍속자료를 이용한 위험도에 기초한 기본설계풍속과 기본 설계풍속지도의 개발에 실용적인 도구로 활용 가능하다고 본다.

• 한국강구조학회 논문집
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• 제22권6호
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• pp.573-580
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• 2010

본 연구는 바람에 민감한 영향을 받는 건축물 또는 구조물에 있어서 풍향풍속을 고려하여 평가하는 방법을 제안하며 지역별 년 최대풍속에 따른 풍향풍속 특성에 대한 기초적인 결과를 정리한 것이다. 본 풍향풍속성 평가방법에서는 년최대풍속의 기상청 데이터를 기초로 하여 극치분포를 통해 적합성을 확인하였으며 풍향성을 고려하기 위하여 풍향풍속별 풍향패턴을 4그룹으로 구분하여 풍향풍속성 평가방법을 시도하여 제안하였다. 연구결과는 서울, 통영, 인천지역의 년최대풍속 기상데이터를 사용하여 전풍향풍속이 Gumbel분포에 의한 적합성을 확인하였으며, 이 전풍향풍속의 Gumbel model은 패턴별 4그룹 풍향풍속 Gumbel mode을 지배하는 독립된 확률특성을 가지므로 풍향패턴 4그룹 풍향풍속성의 평가를 통하여 적용율을 제안하였다. 연구결과는 년최대풍속에 의한 Gumbel분포의 적합성에 따른 서울, 통영, 인천 지역의 풍향패턴 4그룹 풍향풍속성을 고려한 새로운 적용율을 제안하였다.

• Wind and Structures
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• 제31권5호
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• pp.473-482
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• 2020

The first-order method for estimating the extreme wind pressure on building envelopes with consideration of the directionality of wind speed and wind pressure is improved to enhance its computational efficiency. In this improved method, the result is obtained directly from the empirical distribution of a random selection of annual maximum wind pressure samples generated by a Monte Carlo method, rather than from the previously utilized extreme wind pressure probability distribution. A discussion of the relationship between the first- and full-order methods indicates that when extreme wind pressures in a non-typhoon climate with a high return period are estimated with consideration of directionality, using the relatively simple first-order method instead of the computationally intensive full-order method is reasonable. The validation of this reasonableness is equivalent to validating two assumptions to improve its computational efficiency: 1) The result obtained by the full-order method is conservative when the extreme wind pressure events among different sectors are independent. 2) The result obtained by the first-order method for a high return period is not significantly affected when the extreme wind speeds among the different sectors are assumed to be independent. These two assumptions are validated by examples in different regions and theoretical derivation.

• 대한토목학회논문집
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• 제28권4A호
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• pp.431-438
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• 2008

본 연구에서는 열대성 저기압에 의하여 지배를 받는 우리나라 서남해안의 풍속을 추정하기 위한 개선된 태풍 몬테카를로 시뮬레이션 방법을 제시하였다. 이를 위하여 적절한 태풍의 물리적 모델을 제시하고 실측치와 비교하여 검증하였다. 아울러 태풍을 구성하는 파라메터의 확률분포 모델을 제시하고 우리나라 인근을 통과한 태풍자료를 사용하여 적합성을 검사하였다. 본 연구의 방법으로 서남해안 주요 지점의 재현기간별 풍속을 추정하여 제시하였는데, 위도가 낮아질수록 풍속이 높아지며, 도로교설계기준의 기본풍속은 과다한 것으로 나타났다.

• Wind and Structures
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• 제8권4호
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• pp.269-281
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• 2005

The paper describes the work of the IAWE Working Group WGF - Extreme Wind Prediction and Zoning, one of the international codification working groups set up in 2000. The topics covered are: the international database of extreme winds, quality assurance and data quality, averaging times, return periods, probability distributions and fitting methods, mixed wind climates, directionality effects, the influence of orography, rare events and simulation methods, long-term climate change, and zoning and mapping. Recommendations are given to promote the future alignment of international codes and standards for wind loading.

• Wind and Structures
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• 제26권3호
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• pp.129-146
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• 2018

Extreme wind speed analysis has been carried out conventionally by assuming the extreme series data is stationary. However, time-varying trends of the extreme wind speed series could be detected at many surface meteorological stations in China. Two main reasons, exposure change and climate change, were provided to explain the temporal trends of daily maximum wind speed and annual maximum wind speed series data, recorded at Hangzhou (China) meteorological station. After making a correction on wind speed series for time varying exposure, it is necessary to perform non-stationary statistical modeling on the corrected extreme wind speed data series in addition to the classical extreme value analysis. The generalized extreme value (GEV) distribution with time-dependent location and scale parameters was selected as a non-stationary model to describe the corrected extreme wind speed series. The obtained non-stationary extreme value models were then used to estimate the non-stationary extreme wind speed quantiles with various mean recurrence intervals (MRIs) considering changing climate, and compared to the corresponding stationary ones with various MRIs for the Hangzhou area in China. The results indicate that the non-stationary property or dependence of extreme wind speed data should be carefully evaluated and reflected in the determination of design wind speeds.

• Wind and Structures
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• 제15권2호
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• pp.177-188
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• 2012

The meteorological events that cause most strong winds in Brazil are extra-tropical cyclones, downbursts and tornadoes. However, one hurricane formed off the coastline of southern Brazil in 2005, a tropical storm formed in 2010 and there are predictions that others may form again. Events such as those described in the paper and which have occurred before 1987, generate data for the wind map presented in the Brazilian wind loading code NBR-6123. This wind map presents the reference wind speeds based on 3-second gust wind speed at 10 m height in open terrain, with 50-year return period, varying from 30 m/s (north half of country) to 50 m/s (extreme south). There is not a separation of the type of climatological event which generated each registered velocity. Therefore, a thunderstorm (TS), an extra-tropical pressure system (EPS) or even a tropical cyclone (TC) are treated the same and its resulting velocities absorbed without differentiation. Since the flow fields generated by each type of meteorological event may be distinct, the indiscriminate combination of the highest wind velocities with aerodynamic coefficients from boundary layer wind tunnels may lead to erroneous loading in buildings.

• Structural Engineering and Mechanics
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• 제45권1호
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• pp.1-18
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• 2013

The typhoon wind characteristics designing for buildings or bridges located in complex terrain and typhoon prone region normally cannot be achieved by the very often few field measurement data, or by physical simulation in wind tunnel. This study proposes a numerical simulation procedure for predicting directional typhoon design wind speeds and profiles for sites over complex terrain by integrating typhoon wind field model, Monte Carlo simulation technique, CFD simulation and artificial neural networks (ANN). The site of Stonecutters Bridge in Hong Kong is chosen as a case study to examine the feasibility of the proposed numerical simulation procedure. Directional typhoon wind fields on the upstream of complex terrain are first generated by using typhoon wind field model together with Monte Carlo simulation method. Then, ANN for predicting directional typhoon wind field at the site are trained using representative directional typhoon wind fields for upstream and these at the site obtained from CFD simulation. Finally, based on the trained ANN model, thousands of directional typhoon wind fields for the site can be generated, and the directional design wind speeds by using extreme wind speed analysis and the directional averaged mean wind profiles can be produced for the site. The case study demonstrated that the proposed procedure is feasible and applicable, and that the effects of complex terrain on design typhoon wind speeds and wind profiles are significant.