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    Title: 二維矩柱橫風向氣彈效應之參數識別
    Other Titles: Identification of aero-elasticity for two-dimensional rectangular cross-sections
    Authors: 張峯榮;Chang, Feng-jung
    Contributors: 淡江大學土木工程學系碩士班
    吳重成;Wu, Jong-cheng
    Keywords: 高層建築;風洞試驗;參數識別;最佳化;Scrouton數;線性氣動力阻尼;非線性氣動力阻尼;氣動力勁度;high-rise building;Wind tunnel test;parameter identification;Optimization;Scrouton number;linear aerodynamic damping;non-linear aerodynamic damping;aerodynamic stiffness
    Date: 2009
    Issue Date: 2010-01-11 05:20:12 (UTC+8)
    Abstract: 由於人口增加以及土地取得不易,欲增加建築物使用空間,必然要增加建築物的高度,所以高層建築已經成為都市發展的趨勢。由於高度高導致結構的勁度較小,加上輕質建築材料之使用,對空氣動力的影響也較為敏感,其風力效應不可忽略。
    一般而言,風洞試驗為探討風力效應之最直接且信賴之方法。本文主要目標為利用風洞試驗量測二維結構在不同風速下所產生的橫風向振動反應,進行氣動力參數識別研究。首先根據文獻推導二維結構在橫風向形成鎖定時之理論解。理論解顯示氣動力參數之值除了受外型與約化風速影響外,亦和無因次密度(mr)及Scrouton數有關。然後利用理論解推衍出之方法--追蹤共振法進行氣動力參數識別。再者,為更改善識別之精確度,將追蹤共振法識別出的參數值當做最佳化之初始值代回理論解,在時域與實驗值比較,進行最佳化的曲線擬合,進而得到更精確的參數識別結果。
    本研究使用三組不同的斷面模型進行識別實驗,分別為方型斷面、矩形斷面(BD=1/2)及矩形斷面(BD=1/3)。每種斷面以不同密度分類,密度範圍為200~300kg/m3。為增加實驗結果可靠度,在每個風速下均進行試驗兩到三次,以上述之追蹤共振法與時域最佳化的曲線擬合法進行參數識別。識別結果顯示,當形成鎖定時,橫風向振幅隨約化風速增加而增大,而後方型斷面會趨於定值,矩形斷面(BD=1/2及BD=1/3)則在高風速後段有微降現象。在氣動力參數方面,方型斷面之線性氣動力阻尼Y1、非線性氣動力阻尼ε及氣動力勁度Y2均隨約化風速增加而減小;矩形斷面(BD=1/2及BD=1/3) 之線性氣動力阻尼Y1大致隨約化風速增加而減小,唯在高風速後段有微升現象,其非線性氣動力阻尼ε大致隨約化風速增加而呈現增加趨勢,唯在高風速後段有微降現象,氣動力勁度Y2則隨約化風速增加呈一致性遞減。
    Due to population growth in limited lands, the demanding usage of space has begot the construction of high-rise buildings in many modernized cities. As the lessened structural stiffness accompanied with the use of newly developed light materials, their susceptibility to wind excitation is obvious and the induced aerodynamic effect has become inevitably important.
    In general, wind tunnel tests are the most reliable approach to investigate the aerodynamic effect. The objective of this study is to identify the aerodynamic parameters of two-dimensional structures by measuring the across-wind responses in the wind tunnel tests. The analytical solution in the lock-in stage was firstly derived according an existent literature, and it shows that the aerodynamic parameters are not only functions of the section shape and reduced wind velocity but also functions of the non-dimensional density (mr) and Scrouton number. Secondly, the Trace-Resonance method was further derived from the analytical solution and will be used for the identification of the aerodynamic parameters. To improve the accuracy in the results, the optimization of the curve-fitting for experimental and analytical response in time domain by using the previously obtained parameters as the initial guess will be performed to finalize the results of identification.
    Three different section shapes were used in the wind tunnel tests for identification. They are square section, rectangular section (BD=1/2) and rectangular section (BD=1/3). Each section was further categorized by density which varies from 200 to 300kg/m3. Each test was performed twice or three times for increasing experimental reliability, and the identification procedures were processed accordingly. From the identified results, the following conclusions have been observed. In the lock-in stage, the across-wind amplitude increases with the reduced wind velocity, and then approaches to a constant for the square sections but slightly goes down for rectangular sections. For square sections, the aerodynamic parameters (including linear and nonlinear aerodynamic dampings Y1 and ε and aerodynamic stiffness Y2) decrease as the reduced wind velocity increases. For rectangular sections (BD=1/2 and BD=1/3), the linear aerodynamic damping Y1 decreases with the reduced velocity increased but a slight rise-up in the tail; the nonlinear aerodynamic damping ε increases with the reduced velocity but a slight decay in the tail; and the aerodynamic stiffness Y2 decreases with the reduced velocity increased.
    Appears in Collections:[土木工程學系暨研究所] 學位論文

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