本文選題：空冷橋架 + 隨機振動��； 參考：《西安建筑科技大學(xué)》2015年碩士論文

【摘要】：空冷系統(tǒng)具有明顯的環(huán)境效益,廣泛用于我國富煤缺水的北方地區(qū)。空冷結(jié)構(gòu)的安全性直接影響到火電廠正常運行,以往研究主要集中在整體結(jié)構(gòu)遭受風荷載、地震作用等方面,關(guān)于風機運轉(zhuǎn)致振問題研究尚顯不足。空冷橋架和風機系統(tǒng)屬于耦合體系,風機運轉(zhuǎn)必然引起橋架結(jié)構(gòu)振動,尤其在空冷結(jié)構(gòu)長期工作狀態(tài)下風機運轉(zhuǎn)產(chǎn)生的擾力將使橋架結(jié)構(gòu)出現(xiàn)疲勞破壞。本文以現(xiàn)場實測空冷結(jié)構(gòu)橋架振動結(jié)果為基礎(chǔ),建立橋架上風機擾力荷載模型。在擾力荷載作用下進行空冷結(jié)構(gòu)隨機振動響應(yīng)分析,最后定量評價橋架結(jié)構(gòu)在服役期內(nèi)風機擾力影響下的可靠性。(1)本文首先闡述了空冷結(jié)構(gòu)在我國發(fā)展的必然趨勢,系統(tǒng)總結(jié)了空冷結(jié)構(gòu)目前的研究現(xiàn)狀,分別從頻域和時域角度介紹荷載識別方法。圍繞空冷結(jié)構(gòu)風機橋架現(xiàn)場實測振動呈現(xiàn)隨機特性,論述有關(guān)隨機過程的基本概念,窄帶隨機過程的統(tǒng)計特性以及結(jié)構(gòu)隨機振動的計算分析方法。(2)針對不同轉(zhuǎn)速下現(xiàn)場實測的直接空冷系統(tǒng)風機橋架振動速度響應(yīng),分別在時域和頻域?qū)φ駝禹憫?yīng)進行分析,傳統(tǒng)簡諧擾力荷載作用下的振動響應(yīng)不能反映實測結(jié)果中幅度和相位緩慢變化的窄帶隨機特性。本文以實測振動響應(yīng)為基礎(chǔ),建立基于載波理論的風機隨機擾力模型,并以振動響應(yīng)的功率譜為目標,識別擾力模型參數(shù),結(jié)果表明建立的擾力模型能夠很好地反映橋架振動的隨機性。(3)根據(jù)結(jié)構(gòu)動力學(xué)理論的振型疊加法,動力反應(yīng)數(shù)值分析方法中的中心差分原理,推導(dǎo)已知橋架結(jié)構(gòu)振動響應(yīng),反分析求解橋架上風機擾力的計算方法。基于實測各工況橋架結(jié)構(gòu)振動輸出響應(yīng),結(jié)合有限元模態(tài)分析結(jié)果,采用反演方法識別風機擾力,并在頻域和時域內(nèi)對比驗證反分析結(jié)果的可靠性。結(jié)果表明識別的等效擾力荷載模型能夠反映實際不同工作條件下風機運行對支撐橋架的影響。(4)建立實際空冷結(jié)構(gòu)有限元模型,以諧波疊加法生成目標功率譜下的風機擾力時程樣本,計算擾力荷載作用下空冷結(jié)構(gòu)隨機振動響應(yīng),并對計算結(jié)果進行分析。提取多組風機擾力荷載作用下橋架隨機振動的應(yīng)力結(jié)果,采用雨流計數(shù)程序?qū)ζ鋺?yīng)力幅進行統(tǒng)計,計算橋架危險點在不同服役期內(nèi)的疲勞累積損傷,給出相應(yīng)服役期內(nèi)結(jié)構(gòu)不發(fā)生疲勞失效的可靠度。
[Abstract]:Air-cooling system has obvious environmental benefits and is widely used in the north of China, which is rich in coal and short of water.The safety of air-cooled structures has a direct impact on the normal operation of thermal power plants. Previous studies focused on wind load and seismic action on the whole structure.The air-cooled bridge frame and fan system belong to the coupling system, the fan operation will inevitably cause the bridge structure vibration, especially under the air-cooled structure long-term operation disturbance force will cause fatigue damage to the bridge frame structure.Based on the measured results of vibration of air-cooled structure bridge, the model of disturbance load of fan on bridge frame is established in this paper.The random vibration response analysis of air-cooled structure under disturbance load is carried out. Finally, the reliability of bridge frame structure under the influence of blower disturbance force during service period is quantitatively evaluated.) in this paper, the inevitable development trend of air-cooled structure in China is first expounded.The present research status of air-cooled structures is summarized systematically, and load identification methods are introduced from frequency domain and time domain respectively.Based on the random characteristics of field measured vibration of air-cooled structure fan bridge frame, the basic concepts of stochastic process are discussed.Statistical characteristics of narrow Band Stochastic process and calculation and Analysis method of structural Random Vibration. (2) aiming at the vibration velocity response of fan bridge of direct air-cooled system measured at different rotational speeds, the vibration response is analyzed in time domain and frequency domain, respectively.The vibration response under the traditional harmonic disturbance force can not reflect the narrow band random characteristic of the amplitude and phase in the measured results.Based on the measured vibration response, a random disturbance model of fan based on carrier theory is established in this paper. The parameters of the disturbance model are identified by taking the power spectrum of the vibration response as the target.The results show that the disturbance force model can well reflect the randomness of bridge vibration. According to the vibration superposition method of structural dynamics theory and the central difference principle in the numerical analysis method of dynamic response, the known vibration response of bridge frame structure is deduced.The calculation method for calculating the disturbance force of the blower on the bridge frame by inverse analysis.Based on the measured vibration output response of the bridge structure under different operating conditions, combined with the modal analysis results of finite element method, the inverse method is used to identify the disturbance force of the fan, and the reliability of the back-analysis results is verified by comparing the results in frequency domain with that in time domain.The results show that the identified equivalent disturbance load model can reflect the influence of fan operation on the supporting bridge under different actual working conditions.The harmonic superposition method is used to generate the time history samples of the disturbance force of the fan under the target power spectrum. The random vibration response of air-cooled structure under the disturbing force load is calculated, and the calculated results are analyzed.The stress results of random vibration of the bridge frame under the disturbance force load of many sets of fans were extracted. The stress amplitude of the bridge was counted by the rain flow counting program, and the fatigue cumulative damage of the dangerous point of the bridge in different service periods was calculated.The reliability of structure without fatigue failure during the corresponding service period is given.
【學(xué)位授予單位】：西安建筑科技大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2015
【分類號】：TU311.3

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