• 생물환경조절학회지
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• 제4권1호
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• pp.1-8
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• 1995

One of the most destructive forces around greenhouses is wind. Wind loads can be obtained by multiplying velocity pressure by dimensionless wind force coefficient. Generally, wind force coefficients can be determined by wind tunnel experiments. The wind force coefficient distribution on a single - span arched greenhouse was estimated using experimental data and compared with reported values from various countries. The results obtained are as follows : 1. The coefficients obtained from this study agree with the values proposed by G. L. Nelson except about 0.5 of difference in the middle region of roof section. This discrepancy is mainly attributed to the dissimilarity of experimental conditions (or wind tunnel test such as Reynolds number, type of terrain, surface roughness of model, location of the lapping and measuring methods. 2. Considering that the wind force coefficients are varied along the height of a wall at wind direction perpendicular to wall, structural analysis using subdivided wind force coefficient distribution is more resonable for wall. 3. It is recommendable that wind force coefficient distribution on a roof should take more subdivision than the existing four equal divisions for more accurate structural design. 4. Structural design using wind forces close to real values is more advantageous in safety and expense.

• 한국농공학회지
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• 제38권2호
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• pp.145-151
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• 1996

Wind force coefficients of multi-span arched greenhouses with respect to wind direction of $0^{\circ}$ and $30^{\circ}$ were estimated to give more reasonable coefficient. The conventional and subdivided division types of wind force coefficient distribution diagrams were constructed by using the wind tunnel experimental data. Bending moments on the greenhouses were determined through structural analysis using obtained wind force coefficients, and were analyzed. Because actual wind pressure values on a face of greenhouse varied with locations, the more divisions of wind force coefficient distribution were subdivided, the better distribution type was coincided with actual state. In order to calculate the more accurate section force occurred on the arched greenhouse by the wind loads, it was recommendable that the wind force coefficient distribution should take more subdivision type. The maximum bending moment at the multi-span greenhouse frame at wind direction of $30^{\circ}$ was greater than that at O。, therefore the wind force coefficient at inclined wind direction to the wall was needed to be considered for the multi-span greenhouse structural design.

• 한국농공학회지
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• 제35권4호
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• pp.76-85
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• 1993

The purpose of this study was to analyze the wind force distribution on the two single-span arched plastic house depending upon the house spacing and wind direction, which may provide the fundamental criteria for the structural design. In order to specify the wind force distribution, the variation of the wind force coefficients, the mean wind force coefficients and the drag force coefficients were estimated from the wind tunnel test data. The results obtained are as follows : 1. At the wind direction of 90$^{\circ}$, there was a typical span interval at which the maximum negative pressure was occured at the edge of the inside walls. 2. In the consideration of wind loads, the wind force coefficients estimated from independent single-span arched plastic house should not be directly applied to the structural design on the double houses separated. 3. The average maximum negative wind force on the inside walls was occured at the wind direction of 90$^{\circ}$, and the variations depending on the span intervals was not significant. 4. The average maximum drag force was occured at the wind direction of 300, and the magnitude of drag force was more significant at the first house. As the distance between two houses was increased, the drag force was slightly increased for every wind direction.

• 신재생에너지
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• 제9권1호
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• pp.60-68
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• 2013

In recent years, green house effect related natural disasters occur throughout the world. Carbon dioxide, mainly comes from the fossil fuel burning, is suspected to be the cause of green house effect. To reduce the emission of carbon dioxide, we need to find alternative energy resources such as photovoltaic energy. In this paper, the basic characteristics of wind force coefficient on a PV panel installed on the floating type PV energy generation system are investigated though the two-dimensional wind tunnel tests. Test variables included the angle of PV panel, direction of wind, number of rows of PV panel and attached or not attached frame. Based on the results obtained through the wind tunnel tests, it was found that the wind force coefficient can be used as a preliminary data in the design of the structure.

• Wind and Structures
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• 제36권4호
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• pp.249-261
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• 2023

Aerodynamic force coefficients are generally prescribed by an ensemble average of ten and/or twenty 10-minute samples. However, this makes it difficult to identify the exact probability distribution and exceedance probability of the prescribed values. In this study, 12,600 10-minute samples on three tall buildings were measured, and the probability distributions were first identified and the aerodynamic force coefficients corresponding to the specific non-exceedance probabilities (cumulative probabilities) of wind load were then evaluated. It was found that the probability distributions of the mean and fluctuating aerodynamic force coefficients followed a normal distribution. The ratios of aerodynamic force coefficients corresponding to the specific non-exceedance probabilities (C_f,Non) to the ensemble average of 12,600 samples (C_f,Ens), which was defined as an adjusting factor (C_f,Non/C_f,Ens), were less than 2%. The effect of coefficient of variation of wind speed on the adjusting factor is larger than that of the annual non-exceedance probability of wind load. The non-exceedance probabilities of the aerodynamic force coefficient is between P_C,nonex = 50% and 60% regardless of force components and aspect ratios. The adjusting factors from the Gumbel distribution were larger than those from the normal distribution.

• Wind and Structures
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• 제14권1호
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• pp.1-14
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• 2011

Open frame structures, such as those commonly found in industrial process facilities, are often densely occupied with process related equipment. This paper presents a method for estimating wind loads for high-solidity open frame structures that differs from current approaches, which accumulate wind load contributions from various individual structure components. The method considers the structure as a porous block of arbitrary plan dimension that is subject to wind from any direction. The proposed method compares favorably with wind tunnel test results for similar structures. The possibility of defining an upper bound force coefficient is also discussed.

• 한국강구조학회 논문집
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• 제23권1호
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• pp.73-81
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• 2011

골조로 구성된 철탑의 풍력계수는 구성부재의 단면형상, 충실율 등에 의해 변하며 풍향각에 의해서도 여러 가지 특성이 나타난다. 본 연구에서는 이러한 철탑골조에 대하여 충실율과 풍향각을 변화시키면서 풍동실험을 수행하여 철탑골조에 작용하는 풍력특성을 평가한다. 실험은 먼저 철탑을 구성하고 있는 부재의 특성을 파악하기 위한 기본형상 부재에 대한 실험을 수행하였다. 그리고 철탑 사각골조는 2D와 3D 형태로 기본형에 철탑부재를 추가하는 방법과, 부재크기를 증가시키는 방법으로 충실율을 변화시킨 모형을 제작하였으며, 2D 형상은 풍향각을 0도에서 90도까지, 3D 형상은 풍향각을 0도에서 45도까지 변화시키면서 풍동실험을 수행하였다. 본 연구의 결과인 철탑 사각골조의 풍력계수 특성은 향후 철탑 풍하중 설계의 기초자료로 사용될 것이다.

• 대한조선학회논문집
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• 제48권2호
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• pp.165-170
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• 2011

In this paper, wind force coefficient by wind tunnel experiment is obtained to compute the accurate wind force of the gantry crane model to be used for mobile harbor ship. The first crane model was tested under 20, 30, 40, 52m/s, partially 58m/s and the wind force coefficient is about 2.0 which is very close to the suggested theoretical value. The other is the more reliable crane model and tested under 20, 30, 40m/s also giving the similar realistic wind force coefficient. Also structural analysis of crane model was performed giving the reliable stress level. Since the rolling effect is important for mobile harbor ship, the safety of the crane on the ship needs to be guaranteed. For this, using the computed reaction forces, a tie-down design is suggested which connects the crane and ship to resist the turnover motion of the crane.

• Wind and Structures
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• 제30권3호
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• pp.245-260
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• 2020

Wind load and responses are the major factors which govern the design norms of tall buildings. Corner modification is one of the most commonly used minor shape modification measure which significantly reduces the wind load and responses. This study presents a comparison of wind load and pressure distribution on different corner modified (chamfered and rounded) Y plan shaped buildings. The numerical study is done by ANSYS CFX. Two turbulence models, k-epsilon and Shear Stress Transport (SST), are used in the simulation of the building and the data are compared with the previous experimental results in a similar flow condition. The variation of the flow patterns, distribution of pressure over the surfaces, force and moment coefficients are evaluated and the results are represented graphically to understand the extent of nonconformities due to corner modifications. Rounded corner shape is proving out to be more efficient in comparing to chamfered corner for wind load reduction. The maximum reduction in the maximum force and moment coefficient is about 21.1% and 19.2% for 50% rounded corner cut.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2004년도 추계학술대회
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• pp.1413-1417
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• 2004

The environmental elements which naturally occur can result in structural damages and operating faults of vessels under the navigation and mooring. These primary factors are considered as wind, waves and tide. In order to investigate wind shielding effects with respect to wind load conditions between two ships which face the wind directly or slantingly to the wind direction, this numerical simulation was preferred in terms of the variation of wind loads according to different distances, wind velocities and wind directions between two ships. The results were proved to be quite reasonable, comparing with experimental data from Danish Maritime Institute, and the report, "Environmental Conditions And Environmental Loads" published by Det Norske Veritas.