高層建築受干擾效應下氣動力阻尼影響

Investigation on aerodynamic damping of high-rise building under interference effect .

林珮萱(Pei-Hsuan Lin)

指導教授 ： 羅元隆

淡江大學/工學院/土木工程學系碩士班/碩士(2018年)

https://doi.org/10.6846/TKU.2018.00513

摘要

現今建築物耐風設計規範對於鄰近建築物的干擾效應缺少規範建議，且一般來說都市地形周遭環境甚為複雜，因此多半必須採用風洞試驗作為設計風力的依據。本研究探討兩棟方柱形建築物之間風力對於彼此所造成之干擾效應影響，比較氣動力阻尼在干擾效應影響下及沒有干擾效應下的差異性。此外，高層建築物受風力作用的位移計算，橫風向氣動力行為複雜，尤其在低史庫頓數(低質量、低阻尼)的高層建築結構時，會因風力造成過大的位移反應，導致氣動力不穩定之現象，對結構物產生極大危害。因此本研究特別針對低史庫頓數的結構系統進行討論。
風洞實驗由指導教授羅元隆老師於2017年8月於東京工藝大學風工程研究中心完成。採用試驗段斷面為18×1.8×2.2m的大氣邊界層風洞進行氣彈力振動試驗。以B地況(∝=0.2)作為逼近流場，模型高長度縮尺為1/400，改變12個約化風速(6.5,7.5,8.3,9.0,9.7,10.5,11.0,11.5,12.2,13.1,13.8和14.6)作為探討不同約化風速下橫風向振動行為的氣動力特性評估。模型斷面分別以矩形模型寬度(B)和深度(D)均為0.07m，高度(H)為0.56m，高寬比8；梯形模型頂部寬度為0.04m，底部寬度為0.1m，高度與矩形高度相同，高寬比(高度與平均寬度)也是8，體積與矩形模型相同，以此基本性質做為比較基準。加入剛性棒狀物體作為干擾建物斷面。干擾位置共20個位置。
本研究以實驗結果作為探討，針對高層建築物受干擾效應下的氣動力阻尼行為改變，不同實驗設置包含不同干擾位置之變化；不同主要建築物所造成的結構反應；不同約化風速與不同干擾建築物(固定干擾與振動干擾)之影響等四項可能因素。利用兩種計算氣動力阻尼之方式：隨機衰減法、小波理論。本研究中首先進行兩種方法論的計算結果比較，確定相符後，採用其中一種進行氣動力阻尼值的探討，並期望在氣彈力實驗中找出其無法預估的結構氣動力之現象，當結構物因為風力而產生振動時兩棟建築物之間交互影響作用，針對其氣動力阻尼值與擾動位移反應相關的分布進行比較，顯示出氣動力阻尼的改變將導致擾動位移變化。

關鍵字

干擾效應 ； 氣動力阻尼 ； 氣彈力行為 ； 隨機衰減法 ； 高層建築物 ； 小波理論

並列摘要

There is no standard recommendation for the interference effect of buildings wind-resistance design specifications on neighboring buildings, and generally, the surrounding environment of urban terrain is very complicated. Therefore, wind tunnel tests must be used as the basis for wind design. This study investigates the effect of wind forces on the mutual interference caused by two square pillar buildings, and compares the effects of aerodynamic damping under the influence of disturbance effects and without interference effects. In addition, the calculation of the displacement of high-rise buildings due to wind forces, the transverse wind aerodynamic behavior is complex, especially when the low-scruton number (low-quality and low-damping) high-rise building structure, due to wind caused by excessive displacement response, resulting in aerodynamic. The phenomenon of unstable force has great harm to the structure. Therefore, this study specifically discusses the structural system of the low Scruton number.
The wind tunnel experiment about the aero-elastic vibration test is conducted in the 18.0 × 1.8 × 2.2 m boundary layer wind tunnel which is conducted by the guidance professor Professor Lo Yuanlong at Wind Engineering Research Center at Tokyo Polytechnic University in August 2017. A 1/400 scale turbulent flow over a sub-urban terrain with a power law index exponent for mean velocity profile of 0.2 is simulated with properly equipped spires, saw barriers, and roughness blocks. Changing 12 reduced wind speeds (6.5, 7.5, 8.3, 9.0, 9.7, 10.5, 11.0, 11.5, 12.2, 13.1, 13.8, and 14.6). As a study of the aerodynamic characteristics of across-wind vibratory behavior under different reduced wind speeds, the square prism model is 0.07 m in both width (B) and depth (D) and 0.56 m in height (H), which make the aspect ratio (H/B) 8. The tapered model is 0.04 m in width on the roof-top and 0.10 m in width on the bottom. The height is the same as the square one and the aspect ratio (height to the averaged width) is also 8. Both the two principal building models are manufactured in the same volume in order to have a basic comparison level. Addiction the interfering model which is made rigid-pivoted aero-elastic and tuned to vibrate in the same fundamental frequency as the principal building models. There are 20 interference locations.
In this study, experimental results are used to investigate the aerodynamic damping behavior of high-rise buildings under disturbance effects. Different experimental settings include changes in different interference positions; structural responses caused by different major buildings; different reduced wind speeds and different interferences Four possible factors such as the impact of buildings (rigid interference and vibration). Two methods for calculating aerodynamic damping are used: random decay method, wavelet theory. In this study, firstly, the comparison of the calculation results of the two methodologies was performed. After the determination, the aerodynamic damping value was discussed using one of them. It was expected that the aerodynamic forces could not be estimated in the aeroelastic experiment. The interaction between the two buildings when vibration occurs due to wind force is compared with the distribution of the aerodynamic damping value and the disturbance displacement response. It is shown that changes in the aerodynamic damping will lead to changes in the disturbance displacement.

並列關鍵字

Interference effect ； Aerodynamic damping ； Aero-elastic vibration ； Random decrement technique ； High-rise Building ； wavelet-based demodulation method

參考文獻

[1] American National Standard A58.1-1982 Minimum American National Standard Institute, Inc., New York.

[2] Architectural Institute of Japan (AIJ),2004.

[3] Bailey, P.A., Kwok, K.C.S., 1985. Interference excitation of twin tall buildings. J. Wind Eng. Ind. Aerodyn. 21, 323-338.

[4] Blessmann, J., Riera, J. D., 1985, “Wind excitation of neighboring tall buildings”, Journal of Wind Engineering and Industrial Aerodynamics, 18, 91-103.

[5] Cowdery,1986, “Two topics of interesting experimental industrial aerodynamic”, symposium on wind effects on buildings and structures, National physical laboratory, Teddington.