較不規則斷面系列之高層建築對設計風載重之風洞實驗研究

A Wind Tunnel Experiment Investigation on Irregular Cross-Section of High-Rise Building’Design Wind Load

林俊煒(Chun-Wei Lin)

指導教授 ： 鄭啟明

淡江大學/工學院/土木工程學系碩士班/碩士(2006年)

https://doi.org/10.6846/TKU.2006.00016

摘要

隨著工商業蓬勃發展，在土地與空間的有限下，高層建築已成為為主要的趨勢。除受到地震力的影響外，風力亦為高層建築主要的側向風載重。而為求造型之美觀與變化，使得外觀造型亦朝向多元化設計，故高層建築在斷面形式及幾何造型的影響將為設計風載重的主要課題。
本文主要探討在相同體積，相同容積率，相同建蔽率的使用條件下，較不規則斷面形式之高層建築其外型隨著斷面變化對風力反應之影響，此將斷面型式分為四個主題系列，分別為(1) 門形斷面系列 (2) 角隅突出形斷面系列 (3) 三角放射形斷面系列 (4)扇形斷面系列。並以此四個主題造型系列與一高寬比7，長寬高尺寸分別為40公尺、40公尺與280公尺之基準建築物來作比較，經由實驗量得之無因次化風力係數和無因次化風力頻譜轉換至實場建築物的受力情形，計算結構物之設計風載重。
風洞實驗採用力平衡儀量測法，配合壓力轉換器與皮托管及熱膜探針，對20組模型進行實驗並以實驗結果推算其設計風載重。由本文實驗結果可知，地況不同對於門形斷面系列與三角放射形斷面系列之橫風向設計風載重的影響較大。整體而言，順風向設計風載重以門型斷面系列最低，橫風向設計風載重則以扇形斷面系列為最低。其中門形斷面系列開口處越小將降低設計風載重，設計時開口處應盡量避免過大，使整體斷面形狀能接近矩形為佳；角隅突出形斷面系列其角隅突出物越大則橫風向設計風載重有大幅降低的趨勢，角隅突出物較大的斷面無論在順風向與橫風向設計風載重皆有不錯的表現，行此類型斷面設計時，應使角隅突出部份尺寸接近於中央主結構部份；三角放射形斷面系列其形狀擴散越少則能降低順風向設計風載重，設計此類型之斷面時，應盡量使斷面形狀內縮；扇形斷面系列其實驗中所得之結果顯示此斷面的風力反應並未與弧度大小成規則性比例，雖於順風向設計風載重上略嫌高於基準建築物，但與其他系列相較而言，其橫風向設計風載重之大幅降低實為其重要價值。

關鍵字

高層建築 ； 風洞實驗 ； 力平衡儀 ； 斷面形式 ； 不規則斷面 ； 設計風載重

並列摘要

In a modern city where land is expensive, high-rise buildings play important roles in the city development. Besides the earthquake force, wind force becomes an important lateral design load for high-rise buildings. To satisfy architectures’ aesthetic requirement, buildings tend to have variety of geometry shapes and appearances. Therefore, the effects of cross-section and geometric shape on the design wind load become an important design issue for high-rise buildings.
In this thesis, the wind forces acting on four different series of irregular cross-section shapes in both urban and open terrain flow fields were investigated. The cross-sectional shapes include: (1) the Portal shape, (2) the Corner Protrusion shape, (3) the Radiate Triangle shape, (4) the Arch shape. The cross-section area and height of four categories of testing models are identical to a square prism with aspect ratio of 7, and a proto-type dimension of . 20 tall building models were tested in the wind tunnel, High Frequency Force Balance was used to obtain the wind force coefficients and power spectra by experiment, and consequently, the design wind loads were calculated.
The results indicated that, different terrain would show more influences on the acrosswind design wind load of the Portal shape and the Radiate Triangle shape modes than the others. In general, the Portal shape has the lowest alongwind design wind load, and the Arch shape has the lowest the acrosswind design wind load. A small central opening area could effectively reduce the design wind load of the Portal shape building. Increasing the area of the four corners of Corner Protrusion shape would significantly lower the acrosswind design wind load. The best wind resistant cross-section of the Corner Protrusion shape is to keep the area of the protrusion corner similar to the central area. Decreasing the leg length of the Radiate Triangle shape would lower the alongwind design wind load. The wind tunnel results of Arch shape model show that this type of building would have higher alongwind design wind load and significantly lower acrosswind loading comparing to the typical square shape buildings.

並列關鍵字

high-rise building ； wind tunnel experiment ； force balance ； cross-section shape ； irregular Cross-Section ； design wind load

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