• Wind and Structures
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• v.3 no.2
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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.

• Wind and Structures
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• v.15 no.2
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• pp.163-176
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• 2012

Damaging winds, associated with a variety of weather phenomena, are frequently experienced in New Zealand. Observations and modelling of two recent extreme wind events; the Taranaki tornado outbreak of July 2007, and the Greymouth down-slope easterly wind storm of July 2008 are described in detail here. Post-event engineering damage surveys, rare for New Zealand, were done for these storms and the results are summarized here. Finally, the issue of sampling extreme wind events is raised and the need to include detailed numerical modelling analysis to understand wind gust climatologies at observing sites and extending these to wider regions is discussed.

• Wind and Structures
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• v.1 no.4
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• pp.287-302
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• 1998

This paper formulates a probabilistic model which is able to represent the maximum instantaneous wind velocity. Unlike the classical methods, where the randomness is circumscribed within the mean maximum component, this model relies also on the randomness of the maximum value of the turbulent fluctuation. The application of the FOSM method furnishes the first and second statistical moments in closed form. The comparison between the results herein obtained and those supplied by classical methods points out the central role of the turbulence intensity. Its importance is exalted when extending the analysis from the wind velocity to the wind pressure.

• Wind and Structures
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• v.21 no.4
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• pp.425-442
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• 2015

This paper discusses the processing of the wind loads measured in wind tunnel tests by means of multi-channel pressure scanners, in order to compute the response of 3D structures to atmospheric turbulence in the time domain. Data compression and the resulting computational savings are still a challenge in industrial contexts due to the multiple trial configurations during the construction stages. The advantage and robustness of the bi-orthogonal decomposition (BOD) is demonstrated through an example, a sail glass of the Fondation Louis Vuitton, independently from any tentative physical interpretation of the spatio-temporal decomposition terms. We show however that the energy criterion for the BOD has to be more rigorous than commonly admitted. We find a level of 99.95 % to be necessary in order to recover the extreme values of the loads. Moreover, frequency limitations of wind tunnel experiments are sometimes encountered in passing from the scaled model to the full scale structure. These can be alleviated using a spectral extension of the temporal function terms of the BOD.

• 한국방재학회:학술대회논문집
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• 2011.02a
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• pp.168-168
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• 2011

최근 한반도는 과거 최대 강우량의 기록을 갱신하는 집중호우가 지속적으로 발생하고 있으며, 2000년대 들어 기상재해에 대한 피해 규모가 수조원에 달한다. 자연재해를 예방하여 피해를 최소화하기 위해서는 미래에 발생 가능성이 있는 재해를 사전에 예측하고, 재난발생 가능성을 감소시키며, 발생한 재난의 피해를 최소화시키기 위한 활동이 필요하다. 따라서 본 연구에서는 2003년도에 발생한 태풍 'Maemi'의 영향으로 부산과 경남지역에 발생 가능한 최대 풍피해의 정도를 예측해보고자 하였다. 이를 위해서 태풍의 중심기압과 태풍의 이동경로와 대상지역의 거리를 이용하여 3-second gust를 산정하였고, 이를 이용하여 시 군 구 단위의 주택에 대한 최대 풍피해 분포 특성을 파악하였다. 태풍 Meami에 의한 부산 경남지방의 3-second gust를 산정한 결과 풍속이 25m/s 이상의 폭풍영역에 해당되는 지역은 김해시, 강서구, 남해군, 고성군, 창원시, 사상구, 북구, 함안군, 통영시, 하동군, 거제시, 사천시이고, 강풍영역에는 대부분의 지역이 포함되었다. 그 중에서 3-second gust가 가장 높았던 지역은 북구와 사상구였고, 다음으로 강서구 창원시 사천시, 함안군 이였으며, 마산시, 김해시, 거제시 그리고 양산시가 다음으로 높게 나타났다. 고성군은 3-second gust가 가장 낮게 나타났다. 부산과 경남지방의 집 한 채 피해액은 북구와 강서구, 사상구가 가장 높게나왔고, 다음으로 사천시와 창원시 순으로 높게 나타났다. 거창군은 부산 경남지방 중에서 가장 낮은 피해액이 나타났다. 이러한 결과에는 그 지역에서 발생 가능한 3-second gust의 영향이 크게 작용한 것으로 판단된다. 본 연구에서는 태풍의 특성 자료를 제외한 자료의 경우 국내 자료의 한계로 인해 국외 자료를 이용하거나, 가정을 통해 계산을 진행하였다. 그러나 향후 보다 정확한 최대 풍피해를 평가하기 위해서는 기초자료의 마련이 반드시 이루어져야한다.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.50 no.3
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• pp.173-180
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• 2022

The operation and transportation environment for an unmanned aerial vehicle will be completely different from those for the conventional air and ground transportation. The requirement for a traffic management system for its safe operation has been emerging. Accordingly, investigation is being conducted to analyze the danger that unmanned aerial vehicle may encounter during the flight and to provide the countermeasure by the simulation. When the drones operate in an urban environment, they may be affected by the wind around the building. Thus it is essential to predict the influence of the gust and analyze the resulting risk. In this paper, a method for evaluating the safety for a flight mission under the gust is suggested. By using the precise 6-degree-of-freedom flight simulation that is capable of simulating the gust condition, possible deviation from the pre-planned flight path in terms of the attitude orientation will be predicted. A method of quantifying the probability of the flight mission failure will also be presented.

• Proceedings of the KSME Conference
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• 2008.11b
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• pp.2754-2758
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• 2008

Numerical investigation has been carried out for laminar flow ($Re{\leq}150$) past a square cylinder in cross freestream with an angle of attack. This study would be the first step towards understanding flow-induced forces on cylindrical structures under a strong gust of wind from the viewpoint of wind hazards. Collecting all the numerical results obtained, we propose contour diagrams of drag/lift coefficients and Strouhal number (St) on an Re-Angle plane.

• Wind and Structures
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• v.7 no.3
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• pp.203-214
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• 2004

This paper describes a method for developing a multi-degree-of freedom aero-elasto-plastic model of a base-isolated mid-rise building. The horizontal stiffness of isolators is modeled by several tension springs and the vertical support is performed by air pressure from a compressor. A lead damper and a steel damper are modeled by a U-shaped lead line and an aluminum line. With this model, the frequency ratio of torsional vibration to sway vibration, and plastic displacements of isolation materials can be changed easily when needed. The results of isolation material tests and free vibration tests show that this model provides the object performance. The peak displacement factors are about 4.5 regardless of wind speed in wind tunnel tests, but their gust response factor decreases with increment of wind speed.

• Proceedings of the KSR Conference
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• 2007.11a
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• pp.1152-1157
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• 2007

Anemometers to examine the characteristics of the natural wind in the vicinity of the railway track has been installed in two spots, one at the Cheon-Asan station of the Seoul-Busan high-speed line, and the other at the Daechon station of the Changhang conventional railway line in 2006 to examine the characteristics of the natural wind around the railway track to estimate the actual wind speed acting on the train and to develop the wind gust model consisting with the Korean climate condition. The measured data shows that the instant wind velocity frequently exceeds the velocity of train speed restriction, 20m/s, and the actual wind velocities measured in the vicinity of the track are larger than the that measured by the Korean Meteorological Administration(KMA) because the anemometers are installed on the highly-elevated bridges.

• Structural Engineering and Mechanics
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• v.30 no.5
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• pp.513-534
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• 2008

This paper examines local vibrations in the stay cables of a cable-stayed bridge subjected to wind gusts. The wind loads, including the self-excited load and the buffeting load, are converted into time-domain values using the rational function approximation and the multidimensional autoregressive process, respectively. The global motion of the girder, which is generated by the wind gusts, is analyzed using the modal analysis method. The local vibration of stay cables is calculated using a model in which an inclined cable is subjected to time-varying displacement at one support under global vibration. This model can consider both forced vibration and parametric vibration. The response characteristics of the local vibrations in the stay cables under wind gusts are described using an existing cable-stayed bridge. The results of the numerical analysis show a significant difference between the combined parametric and forced vibrations and the forced vibration.