長方型斷面高層建築順風向氣彈互制識別之參數研究

Parametric study of along wind aeroelasticity for high-rise buildings with rectangular shapes

張英傑(Ying-Chieh Chang)

指導教授 ： 吳重成

淡江大學/工學院/土木工程學系碩士班/碩士(2007年)

https://doi.org/10.6846/TKU.2007.00865

摘要

本論文探討使用強制振動方式對一系列不同比例高層建築之順風向氣彈行為進行系統識別，求得頻率相關之氣動力阻尼與氣動力勁度並比較之。本研究藉由白噪音之強制振動提出一套識別法，理論部分延續林勝偉的論文內容，首先在頻率域假設適當參數確立自激力矩與結構傾角位移之線性關係型式，在時域轉換成狀態空間方程式後，代入平滑流場下之強制振動結構運動方程式，並整合成氣彈互制之狀態空間方程式。比較不同風速下氣彈互制頻率反應函數之實驗與理論值，結合基因演算法與傳統梯度法最佳化進行曲線擬合，決定待求參數值並進而識別出結構的氣動力阻尼與氣動力勁度。

為了將理論推展應用並進行參數研究，本文使用9座模型進行識別試驗，共有3種高度，5種斷面深寬比，實驗組合為15組，因此結果總計有15組不同之氣動力導數比較。值得一提的是，有別於林勝偉的論文，本文進行曲線擬合時同時對七個風速下之轉換函數進行擬合，解決了由個別風速擬合所產生的不同氣動力導數問題；另外，本文亦提出以梯度法配合基因演算法求解，以達到更佳的擬合結果。根據15組識別結果顯示，順風向氣動力阻尼幾皆為負值，且較高之建築具較大氣動力阻尼；氣動力勁度之正負不定，但對氣彈效應貢獻不大。

關鍵字

氣彈

並列摘要

This thesis investigates the aero-elastic behavior of a series of high-rise buildings with different shapes by using a novel identification scheme that employs the forced actuating technique. The aero-elasticity of the buildings are defined by the frequency-dependent aerodynamic damping and stiffness, and they were identified through wind tunnel experiments and parametric comparisons were finally made. By following the formulation in the thesis of Mr. Lin, the relation between the motion-induced moment and the rotation angle was firstly assumed to be linear. The frequency domain representation by the parameters to be determined can then be converted into a state space equation in time domain. The incorporation of such a relation with the equation of motion under wind flow and forced actuation further leads to an aero-elastic state space equation with an input from the forced actuation. The frequency response function thus induced from this aero-elastic state space equation can be used to compare with the experimental data by curve-fitting each other in order to determine the unknown parameters and consequently the aerodynamic damping and stiffness. In performing the curve-fitting, the genetic algorithm and traditional gradient method were used in corporation to fine tune the final results.
The parametric study of building aero-elasticity was conducted by using nine building models in the wind tunnel tests, which results in totally fifteen sets of results. It is worth noticing that, unlike the way employed in the thesis of Mr. Lin, this research used the experimental data under all wind speeds simultaneously in curve-fitting, thus avoided the result inconsistency from every single data set. In addition, the traditional gradient method was also proposed in this research to improve the accuracy of curve-fitted results. According to the fifteen sets of identified results, it is observed that the aerodynamic dampings in the along-wind motion are all negative, and the value increases with the building height. However, the aerodynamic stiffness could be negative or positive, and their contribution to the building aero-elasticity is not significant.

並列關鍵字

aeroelasticity

參考文獻

【1】.林勝偉，”應用白噪音強制振動於高層建築之氣彈互制識別”，吳重成博士指導，私立淡江大學土木工程研究所碩士論文，民國94年6月。

【2】.N,Isyumov and M. Poole,”Wind Induced Torque on Square and Rectangular Building Shapes”,J. of Wind Engineering and Industrial Aerodynamics,(1983),p183-196.

【3】.Zhang,W.J.Xu,Y.L., and Kwok, K.C.S.,”Torsional Vibration and Stability of Wind-excited Tall Buildings with Eccentricity”,J. of Wind Engineering and Industrial Aerodynamics, 50 (1993),p299-308.

【5】.Waldeck,J.L.,1992,”The Measured and Predicted Response of a 300m Concrete Chimney ,”J. Wind Eng. Ing. Aero.,41-44,P229-240.

【9】. Wu, J. C. , 2000, “Modeling of an Actively Braced Full-Scale Building Considering Control-Stucture Interaction”, Earthquake Engineering and Srtuctural Dynamics, Vol.29, No.9, Sep. , pp.1325-1342.