【摘要】：大跨度橋梁具有多階固有振動模態(tài)，在不同的來流風(fēng)速下，各階模態(tài)可能依次發(fā)生渦激共振。因此，研究柔性結(jié)構(gòu)各階模態(tài)渦振的起振風(fēng)速和最大振幅具有重要意義。雖然針對某階振動模態(tài)下的矩形及H形斷面渦振性能已有很多研究，但最大渦振振幅隨模態(tài)頻率、質(zhì)量阻尼參數(shù)、氣動阻尼等的變化規(guī)律還不明確。Scruton數(shù)即質(zhì)量阻尼參數(shù)是影響渦激振動的重要因素，Sc數(shù)會影響渦激振動鎖定區(qū)間和渦振振幅，但Sc數(shù)中的質(zhì)量參數(shù)和阻尼參數(shù)對渦激振動影響不同，缺乏質(zhì)量參數(shù)和阻尼參數(shù)與渦振鎖定區(qū)間、渦振振幅之間的關(guān)系。另外，在實際風(fēng)作用下，沿橋軸線方向上的渦激力并不是完全相關(guān)的，特別是對于大跨橋梁，渦激力的空間相關(guān)性更加明顯，渦激力展向相關(guān)性的研究對渦振振幅預(yù)測有重要意義。 基于以上幾個問題，本文主要進行了如下幾個方面的研究： (1)介紹了橋梁風(fēng)致振動的主要類型，特別是對渦激振動研究現(xiàn)狀做了概括，并對渦激振動的相關(guān)理論做了簡要的闡述。 (2)對寬高比B/D=6的大小比例矩形斷面及B/D=5的H形斷面進行節(jié)段模型渦激振動試驗。相同質(zhì)量及阻尼比的同一模型在不同彈性懸掛頻率下的試驗結(jié)果表明，矩形與H形斷面的豎向渦振振幅不隨懸掛頻率改變。 (3)分別研究了質(zhì)量、阻尼參數(shù)對兩類斷面渦激共振的影響。結(jié)果表明，在相同質(zhì)量下，兩類斷面的渦振振幅隨結(jié)構(gòu)阻尼比s的增加而顯著減小；而在相同結(jié)構(gòu)阻尼比s下，兩類斷面的最大豎向渦振振幅對質(zhì)量參數(shù)的變化都不敏感。應(yīng)用斷面顫振導(dǎo)數(shù)分析了不同質(zhì)量下的氣動阻尼變化，在增加質(zhì)量的同時實際上降低了氣動模態(tài)阻尼比a，因而可能引起最大渦振振幅對質(zhì)量變化不敏感。 (4)矩形斷面風(fēng)洞試驗觀測到的兩個豎向渦振區(qū)間，其最大振幅比約2.2。分別計算了兩個渦振區(qū)間內(nèi)與最大振幅對應(yīng)的氣動阻尼，結(jié)果表明在考慮氣動阻尼影響下應(yīng)用簡諧渦激力模型對最大振幅比進行分析，發(fā)現(xiàn)最大振幅比不與St2成反比是因為兩個區(qū)間最大振幅處氣動阻尼的差異。 (5)以矩形和H形斷面風(fēng)洞試驗結(jié)果為基礎(chǔ)，運用FLUENT對矩形和H形斷面進行數(shù)值模擬，數(shù)值模擬結(jié)果和風(fēng)洞試驗結(jié)果吻合較好。 (6)通過圓柱體風(fēng)洞試驗，對渦激力展向相關(guān)性進行了分析，結(jié)果表明不同截面處90°位置的展向相關(guān)性比180°位置處的展向相關(guān)性大，，渦激力的展向相關(guān)性與振幅、雷諾數(shù)有關(guān)。
[Abstract]:There are many natural vibration modes in long-span bridges, and vortex-induced resonance may occur at different wind speeds. Therefore, it is of great significance to study the initial wind speed and maximum amplitude of vortex vibration of flexible structures. Although much research has been done on the vortex vibration performance of rectangular and H-shaped sections in a certain vibration mode, the maximum amplitude of vortex vibration depends on the modal frequency and mass damping parameters. The variation of aerodynamic damping is not clear. Scruton number, that is, mass damping parameter, is an important factor affecting vortex-induced vibration, and Sc number will affect the locking range and amplitude of vortex-induced vibration. However, the mass and damping parameters in Sc number have different effects on the vortex-induced vibration, and the relationship between the mass parameter and damping parameter and the locking interval and amplitude of vortex-induced vibration is absent. In addition, under the action of actual wind, the vortex-induced forces along the axis of the bridge are not completely related, especially for long-span bridges, the spatial correlation of vortex-induced forces is more obvious. The study of the spanned correlation of vortex-induced forces is of great significance in predicting the amplitude of vortex-induced vibration. Based on the above problems, this paper mainly studies the following aspects: (1) the main types of wind-induced vibration of bridges are introduced, especially the research status of vortex-induced vibration is summarized. The theory of vortex-induced vibration is briefly described. (2) the vortex-induced vibration tests of the rectangular section with the ratio of width to height (B/D=6) and the H-section of the B/D=5 are carried out. The experimental results of the same model with the same mass and damping ratio at different elastic suspension frequencies show that the amplitude of vertical vortex vibration of rectangular and H-shaped sections does not change with the suspension frequency. (3) the effects of mass and damping parameters on the vortex-induced resonance of two kinds of cross-sections are studied. The results show that under the same mass, the amplitude of vortex vibration of the two sections decreases significantly with the increase of the damping ratio of the structure, while the maximum vertical vibration amplitude of the two sections is not sensitive to the variation of the mass parameters at the same damping ratio of the structure. The variation of aerodynamic damping under different mass is analyzed by using cross-section flutter derivative, and the aerodynamic mode damping ratio a is actually reduced while increasing mass, which may cause the maximum amplitude of vortex vibration to be insensitive to mass change. (4) the maximum amplitude ratio of the two vertical vortex vibration regions observed by wind tunnel test with rectangular section is about 2.2. The aerodynamic damping corresponding to the maximum amplitude in two vortex-vibration regions is calculated respectively. The results show that the harmonic vortex-induced force model is used to analyze the maximum amplitude ratio under the influence of aerodynamic damping. It is found that the maximum amplitude ratio is not inversely proportional to St2 because of the difference of aerodynamic damping at the maximum amplitude of the two regions. (5) based on the experimental results of rectangular and H-section wind tunnels, the numerical simulation of rectangular and H-shaped sections is carried out by using FLUENT. The results of numerical simulation are in good agreement with those of wind tunnel tests. (6) through the cylindrical wind tunnel test, the spanwise correlation of vortex-induced forces is analyzed. The results show that the spanwise correlation at 90 擄at different cross-sections is greater than that at 180 擄, and the spanned correlation and amplitude of vortex-induced forces are higher than those at 180 擄. Reynolds number.
【學(xué)位授予單位】：湖南大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2014
【分類號】：U441.3

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