| 摘要: | 現今隨著經濟的發展和科技的進步，人口膨脹迅速，有限的土地與空間不斷減少的現況下，建築物只有向上發展，因此現代都市中便林立了越來越多高層建築物。高層建築物的設計發展方向朝向高度高且質量輕，除了地震力要考量之外，建築物受風的敏感程度亦無可避免地增加。因此風力對於結構物的反應成為高層建築物設計中重要的一環。
在高樓林立的現代都會區中，高層建築物之間存在的相互干擾效應是相當複雜風力載重計算問題。國內外已有若干學者針對流場特性、幾何造型、相對位置、以及來風向之干擾效應造成的整體風力及局部風壓做出定量的描述。然而由於影響因素甚多，且若存在兩棟以上干擾建物時，干擾效應的形成將更為複雜且無法單純以線性疊加方式推測。
本研究進行為使造成干擾效應之來源因素單純化且易於探討，利用壓力量測法之風洞實驗，擬以兩棟相同高寬比為6的方柱建物，在α=0.24的鄉鎮地況下，一者作為可移動的干擾建物，一者作為為固定位置的主要建物。探討在干擾效應下，高層建築物最大風壓係數與最小風壓係數之分布，並以Gumbel和Weibull極值分布理論為基礎，探討極值分布型態受到干擾效應影響下之變化情形，並定義干擾因子對其對建築物外牆披覆物之影響。
本實驗結果得知最大風壓係數會出現在(x/B,y/B) = (3,3)位置，表示干擾建物在主要建物45°之位置可能有較大的影響。最小風壓係數會出現在干擾建物在主要建物上游處y/B = 0，因為干擾建物在後方會產生渦流使主要建物之迎風面能量增加。但本文實驗僅於x/B = -3~3、y/B = 0~3範圍之間，或許極值的發生可能在範圍以外。
In today''s developed society, the explosion in population accelerates the growth of high-rise buildings in urban terrains. However, limited by land resource, high-rise buildings tend to be constructed by means of lighter material and higher levels, which inevitably results in a sensitive feature to wind-excited response rather than earthquake. Therefore, to understand the dynamic behavior of a tall building under wind loadings is attracting more and more concerns. Interference effect between any two neighboring buildings is especially focused in an urban area. The complex phenomenon may be triggered by many factors, such as surrounding flow characteristics, geometric appearance of buildings, relative positions of neighboring buildings, wind attack angles, etc. Many publications regarding this phenomenon have been carried out in domestic or overseas journals and reports. Generally speaking from the literature, such complicated phenomenon cannot be simply linearly superposed one by one.
The present study was conducted to idealize the sources of interference effect and easy to investigate. By means of wind pressure measurement, a square prism model with aspect ratio 6 in a suburban turbulent boundary layer flow (α=0.24) was utilized as a principal building. Meanwhile another identical square prism model made by Balsa wood was utilized as interfering building and installed in several interfering positions. Instantaneous pressures over the principal building''s surface were recorded by at least 90 runs. Each run represents a 10-minute record in full scale. By normalized to velocity pressure at roof top, pressure coefficients were calculated and the maximum and minimum values were found. Based on extreme value theory, the Gumbel and Weibull distribution types were identified for different pressure tap positions due to different flow conditions. Then the design for cladding was briefly introduced.
Experiment results showed that the maximum wind pressure coefficient was occurred in (x/B,y/B) = (3,3) position, representing that significant interference effects in the oblique configuration. The minimum pressure coefficient was found when the interfering building is in the upstream (y/B = 0). However, in this research, only the range between x/B = -3 ~ 3 and y/B = 0 ~ 3 were examined, the discussion on extreme values may be limited and the greater effect could occur outside the experiment range. |
