摘 要
本研究使用風洞實驗研究半圓柱形溫室模型的風力負載，實驗入流流況為紊流邊界層流與均勻流，在不同風向攻角下，利用高頻率的壓力掃描計量測獨棟與連棟半圓柱溫室表面風壓的分佈及瞬間變化，再用甘保機率分佈計算極值風壓，並探討室外紊流強度與陣風風壓係數的關係，以計算建築物的最大風載。研究結果發現：風向角22.5o的最大負壓大於風向角0o時的最大負壓，且時間平均風壓係數符合建築物耐風設計規範(2015)所建議的風壓係數，且平滑表面溫室的最大負壓力大於粗糙表面溫室的最大負壓力。由實驗數據可計算得一個陣風壓力因子g，再利用準穩態假設及耐風設計規範(2015)建議之或實驗量測之時間平均係數可推算出預測極值風壓，此法可預測發生於溫室表面之極值風壓。另外，採用移動平均法後推算求得之極值風壓與陣風壓力因子g皆近似不使用移動平均法，但都大於建築物耐風設計規範所建議的陣風因子G = 1.77。本研究之成果亦顯示當雷諾數大於1.5 x 105，單棟半圓頂溫室的風力係數不再隨雷諾數而變，且單棟溫室的風力係數大於多棟溫室的風力係數。

Abstract
Taiwan is located in the west Pacific typhoon-prone area, and the strong wind during typhoons could bring severe damages to the farm houses and greenhouses. This research uses wind tunnel experiments to study the pressure distribution on semi-circular greenhouses. The instantaneous pressures on the surface of the greenhouse are measured by a multi-channel pressure scanner under different wind directions and arrangements. The experimental results reveal that the time-averaged pressure coefficient of oblique wind (wind direction 22.5o) is larger than that of wind direction normal to the ridge line (wind direction 0o). In addition, although the time-averaged pressure coefficients are within the values suggested by the Wind Code of Taiwan, but the peak pressure is several times larger than the time-average pressure. The gust response factor of the Wind Code is not sufficient to protect the semi-circular greenhouses against the peak pressure on the greenhouse roof. Based on the measured data and the quasi-steady theory, a peak pressure factor, g, was used to predict the peak pressure coefficient Cpeak. The experimental results validate the capability of the peak pressure factor to predict Cpeak. However, the peak pressure factor is dependent on the method to calculate the peak pressure. The peak pressure factor g = 3.81, regardless using moving average or not. But the peak pressure factors Gp is dependent on the turbulence intensity Iu. The results of this study not only provide the needed information for the structural design of the arch-roof greenhouse but also to facilitate a better understanding of the separation phenomenon and peak pressure around circular-bodies.

References
ASCE (2010) Minimum Design Loads for Buildings and Other Structures, Section 6: Wind Loads, ASCE Standard, No.7-10.
Cebeci, T., Mosinskis, C.J., Smith, A.M.O. Calculation of separation points in incompressible turbulent flows. J. Aircraft. Vol. 9, No. 9, 618.
Chu, C.R. 2006. Introduction to Wind Engineering, Techbook Pub. Co., (In Chinese)
Chu C.R, Chiu YH, Chen YJ, Wang YW, Chou CP. Turbulence effects on the discharge coefficient and mean flow rate of wind-driven cross ventilation. Building and Environment 2009; 44: 2064-2072.
Chu, C.R. and Chiang, P.-H. (2014) Turbulence effects on the wake flow and power production of a horizontal-axis wind turbine. J. of Wind Engineering and Industrial Aerodynamics. Vol.124, 82-89.
Cook, N.J. and Mayne, J.R., 1980. A refined working approach to the assessment of wind loads for equivalent static design. J. of Wind Engineering and Industrial Aerodynamics, Vol. 6, 125-137.
Farivar, D.J., 1981. Turbulent uniform flow around cylinders of finite length. AIAA Journal, 19(3), 275-281.
Holmes, J.D. 2001. Wind Loading on Structures, Spon Press, London, p.356.
Lieblein, J., 1974. Efficient methods of extreme value methodology. National Bureau of Standards, Report 74-602, pp.31.
Lin, Y.J., Miau, J.J., Tu, J.K., Tsai, H.W., 2011. Nonstationary, three-dimensional aspects of flow around circular cylinder at critical Reynolds numbers. AIAA Journal, 49(9), 1857-1870.
Mathews, E.H., Meyer, J.P. 1988. Computation of wind loads on a semicircular greenhouse. J. of Wind Engineering and Industrial Aerodynamics, 29, 225–233.
McComb, W.D. 1990. The Physics of Fluid Turbulence, Oxford University Press, U.K. 47-49.
Miau, J.J., Tsai, H.W., Lin, Y.J., Tu, J.K., Fang, C.H., 2011. Experiment on smooth, circular cylinders in cross-flow in the critical Reynolds number regime. Experiments in Fluids.51, 949-967.
Moriyama, H., Sase, S., Uematsu, Y., Yamaguchi, T. 2010. Wind tunnel study of the interaction of two or three side-by-side pipe-framed greenhouses on wind pressure coefficients, Transaction of the American Society of Agricultural and Biological Engineers, Vol. 53(2), 585-592.
Qiu, Y., Sun, Y., Wu, Y., Tamura, Y. 2014. Modeling the mean wind loads on cylindrical roofs with consideration of the Reynolds number effect in uniform flow with low turbulence. J. of Wind Engineering and Industrial Aerodynamics, 129, 11–21.
Simiu, E., Scanlan, R.H. 1996. Wind Effects on Structures: Fundamentals and Applications to Design, 3rd Edition, John Wiley Inc., p.688.
Uematsu, Y., Nakahara, K., Moriyama, H., Sase, S. 2008. Study of wind loads on pipe-framed greenhouses-external wind pressure coefficients on enclosed structures, J. of the Society of Agricultural Structures, Japan; Vol.39, No.2, 121-132.
Uematsu, Y., and Nakahara K., 2009. Effects of sidewall openings on the wind loads on pipe-framed greenhouses. The Seventh Asia-Pacific Conference on Wind Engineering, Taipei, Taiwan, November 8-12.
Wacker, J., Plate, E. J. 1993. Local peak pressure coefficients for cuboidal buildings and corresponding pressure gust factors. J. of Wind Engineering and Industrial Aerodynamics, 50, 183-192.
Yeung, W.W.H., 2007. Similarity study on mean pressure distributions of cylindrical and　spherical bodies. J. of Wind Engineering and Industrial Aerodynamics, 95 (4), 253–266.