• 한국공간구조학회논문집
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• 제19권2호
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• pp.83-90
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• 2019

Most of the variable shading devices are installed outdoors, so they are greatly affected by structural safety due to external climate change, wind, rain, and snow. Especially, due to strong wind such as typhoons, safety problems may occur due to the dropout of the device. Therefore, it is necessary to secure the structural safety against the wind. Therefore, it is necessary to analyze the structural behavior of the windshield to evaluate the structural safety of the variable sunshade device. In this study, we analyze the wind pressure applied to the shading material according to the change of the length of the variable shading device, and apply it to the calculation of the wind load for the structural design of the variable shading device. The CFD (Computational Fluid Dynamic) analysis of the structure of the sample was used to analyze wind pressure magnitude and distribution. In order to estimate the wind pressure, the maximum wind loads of the static and negative pressures acting on the structure were analyzed from numerical simulation results.

• 한국철도학회논문집
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• 제15권6호
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• pp.537-542
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• 2012

철도차량은 자연 강풍 뿐만 아니라 두 열차의 교행으로 인한 교행 풍압도 동시에 받는 경우가 종종 발생하며, 이러한 풍압에 의하여 철도차량의 주행 안정성이 저해될 뿐만아니라 전복의 원인이 되기도 한다. 또한, 해외에서는 강력한 돌풍에 의하여 철도차량이 전복되는 실제 사고 사례가 종종 보고되기도 한다. 따라서, 대부분의 국가에서는 풍속에 대한 차량 운전 규제를 통하여 안전성을 확보하고 있다. 본 연구에서는 다물체 모델에 기초한 철도차량의 전복안전성 이론식을 개발하였으며, 이를 강체모델의 결과와 비교하였다. 후자에서는 대차 및 차체를 별도의 자유도를 가진 것으로 간주하였다. 다물체 모델은 윤중 감소율을 평가하는데 사용 되어온 상용 프로그램을 이용한 기존의 방법을 대체하여 해석할 수 있음을 알 수 있다.

• 생물환경조절학회지
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• 제23권4호
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• pp.269-280
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• 2014

To cope with increasing of vegetables and flowers consumptions, horticulture facilities have been modernized. Korea government recently announced construction plan of new greenhouse complex at reclaimed land. However wind characteristics of reclaimed land is totally different from those of inland, wind pressure on greenhouse built in reclaimed land should be carefully evaluated to secure structural safety on the greenhouse. In this study, as a first step, wind pressure coefficient and local wind pressure coefficient on even-span greenhouse were measured using wind tunnel test. ESDU was adopted to realize wind characteristics of reclaimed land such as wind and turbulence profiles. From the wind tunnel test, when wind direction was 0 degree, it was concluded that KBC2009 standard underestimated scale of wind pressure coefficients at roof area of greenhouse whereas NEN-EN2002 standard underestimated those at every surface of greenhouse. When wind direction was 90 degree, both standards did not well reflect the characteristics of wind pressure distribution. From the analysis of local wind pressure coefficients according to wind direction conditions, design of covering, glazing bar of greenhouse where large effects of the local wind pressure were estimated should be well established. Wind pressure coefficients and local wind pressure coefficients according to parts of the greenhouse were finally suggested and these results could be practically used for suggesting new design standards of greenhouse.

• Wind and Structures
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• 제31권3호
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• pp.185-196
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• 2020

A method to reduce the wind pressure at the leading edge of a noise barrier was investigated by gradually lowering the height of a member added to the end of the noise barrier. The shape of the lowered height of the added member was defined by its length and slope, and the optimal variable was determined in wind tunnel testing via the boundary-layer wind profile. The goal of the optimal shape was to reduce the wind pressure at the leading edge of the noise barrier to the level suggested in the Eurocode and to maintain the base-bending moment of the added member at the same level as the noise-barrier section. Using parametric wind tunnel investigation, an added member with a slope of 1:2 that protruded 1.2 times the height of the noise barrier was proposed. This added member is expected to simplify, or at least minimize, the types of column members required to equidistantly support both added members and noise barriers, which should thereby improve the safety and construction convenience of noise-barrier structures.

• 한국철도학회논문집
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• 제10권3호
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• pp.271-277
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• 2007

The Korean Tilting Train eXpress (TTX) development program is in progress for the purpose of running speed or passenger's comfort improvement at the curved track. However, the speed up and light weight of train make poor the dynamic safety of the TTX in strong cross wind. In this paper, 3-dimensional numerical analysis on the flow field around the TTX under strong cross wind is performed for each operating condition, such as the train speed, cross wind speed, tilting/nontilting condition, and so on. Due to the strong cross wind, the pressure distribution around the train becomes asymmetric, especially at the leading car. Asymmetrical pressure distribution causes the side force and strong unstability. The side force on the train is proportional to the train speed and cross wind speed. Based on the numerical results, the overturning coefficients are predicted for investigation of the train stability, and all of them are less than the critical value, 0.9. The results in this study would be a good data for providing importance to judgement of cross wind safety of TTX.

• Wind and Structures
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• 제31권6호
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• pp.483-493
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• 2020

Large cylindrical floating-roof tanks, constructed as oil containers, are usually distributed regularly in open area and easily exposed to severe wind loads. However, wind pressures around these grouped squat tanks appear to have not been clearly given in design codes or thoroughly studied in existing researches. This paper conducts a detailed investigation on wind loads on the external wall of a four-tank group in square arrangement. To achieve that, wind tunnel tests are carried out on both empty and full tank groups, considering various wind angles and spacing. Results show that 3 regions in elevation can be identified on the tank shell according to the circumferential wind pressure distribution. The upper 2 regions cover a relatively small portion of the shell where excessive negative pressures are spotted, setting an alarm to the design of the top angle and stiffening rings. By comparing results on grouped tanks to those on an isolated tank, grouping effects concerning wind angle, tank position in group and spacing are discussed. Deviations on pressure distributions that will compromise structural safety are outlined, including the increase of negative pressures, the shift of maximum pressure locations as well as the change of positive pressure range. And, several potentially unfavourable wind pressure distributions are selected for further analyses.

• Nuclear Engineering and Technology
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• 제51권2호
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• pp.607-617
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• 2019

Global warming and climate change are increasing the intensity of typhoons and hurricanes and thus increasing the risk effects of typhoon and hurricane hazards on nuclear power plants (NPPs). To reflect these changes, a new NPP should be designed to endure design-basis hurricane wind speeds corresponding to an exceedance frequency of $10^{-7}/yr$. However, the short typhoon and hurricane observation records and uncertainties included in the inputs for an estimation cause significant uncertainty in the estimated wind speeds for return periods of longer than 100,000 years. A logic-tree framework is introduced to handle the epistemic uncertainty when estimating wind speeds. Three key parameters of a typhoon wind field model, i.e., the central pressure difference, pressure profile parameter, and radius to maximum wind, are used for constructing logic tree branches. The wind speeds of the simulated typhoons and the probable maximum wind speeds are estimated using Monte Carlo simulations, and wind hazard curves are derived as a function of the annual exceedance probability or return period. A logic tree decreases the epistemic uncertainty included in the wind intensity models and provides reasonably acceptable wind speeds.

• 한국항공운항학회지
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• 제31권3호
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• pp.93-102
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• 2023

Jeju International Airport is characterized by the occurrence of low-level windshear due to its location, surrounding terrain, and its weather characteristics. Especially the low-level windshear accompanied by tailwinds on both sides of the runway i.e., bidirectional tailwind, is a hazardous weather phenomenon with unique characteristics that are difficult to find at any other airports. This study focuses on bidirectional tailwind occurrence at Jeju International Airport in 2020-2021. As a result, characteristic pressure patterns of the types that cause bidirectional tailwind was identified as it was possible to categorize strong wind types such as 1) strong southwest wind, 2) strong east wind, and 3) strong northwest wind, which do not cause bidirectional tailwind, and wind direction variation types such as 4) bidirectional tailwind, and 5) south wind followed by southwest wind, which cause bidirectional tailwind. The results of this study are expected to contribute to improving aviation safety by enabling aviation operators to predict and take appropriate safety measures based on their understanding of the causes and characteristics of bidirectional tailwind.

• Journal of Mechanical Science and Technology
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• 제18권9호
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• pp.1614-1622
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• 2004

When a High Speed Train (HST) passes through a station with no stop, effects of wind pressure transients caused by this passing train have to be considered for the safety of passengers on the platform and for the possible structural safety problems as well. In Gwangmyeong and Daejeon stations of the Korean high speed railroad, tunnels inside stations for the passing train are proposed to reduce the noise and wind pressure transients to the passengers on the platform. In the present study, transient 3-D full Navier-Stokes solutions with moving mesh to implement train movement are obtained and compared with the results obtained by the towing tank experiment. Investigations on flow phenomena for various train speeds and design modifications are also performed.

• 한국농공학회논문집
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• 제59권4호
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• pp.109-117
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• 2017

Coastal reclamation has created large flat lands, part of which is an attractive site to construct greenhouse complexes for the horticulture industry. Wind environments over these coastal lands are entirely different from those of the inland area, and demand increased structural safety. The objective of this study is to evaluate the structural safety of two single-span greenhouses, peach type and even-span type, under the wind characteristics of coastal reclaimed lands. The wind pressure coefficients acting on the walls and roofs of two greenhouses were measured by wind tunnel experiments, and those acting on the roofs were approximately two times larger than those suggested by the existing design guidelines. Consequently, structural analysis conducted by SAP2000 showed that greenhouse structures designed by the existing guidelines might lead to structural failure under coastal wind conditions because their maximum allowable wind speeds were lower than the design wind speed. Especially, the peach type greenhouse constructed in a reclaimed land could be damaged by approximately 48 % of the design wind speed and needed improvement of structural designs. This study suggested increasing the spacing of rafters with thicker pipes for the peach type greenhouse to enhance economic feasibility of the building under strong wind conditions of reclaimed lands.