本文關(guān)鍵詞：基于小樣本及區(qū)間數(shù)據(jù)的腐蝕PC梁抗力概率分析　出處：《長沙理工大學(xué)》2015年碩士論文　論文類型：學(xué)位論文

  更多相關(guān)文章： 預(yù)應(yīng)力混凝土橋梁 小樣本 區(qū)間數(shù)據(jù) 不確定性 抗彎承載力

【摘要】：在我國現(xiàn)有預(yù)應(yīng)力混凝土橋梁中,被各種不利因素腐蝕的PC橋梁逐年在增加,尤其是基于氯鹽環(huán)境下。考慮這種環(huán)境因素下,由于預(yù)應(yīng)力鋼絞線的腐蝕從而導(dǎo)致梁的抗力衰減,嚴(yán)重影響了橋梁在服役時的安全性。并在此基礎(chǔ)上,根據(jù)似然函數(shù)和最大熵理論,建立了由兩類數(shù)據(jù)(小樣本和區(qū)間數(shù)據(jù))來源引起的不確定性PC橋梁抗力退化分析方法。文章主要是從以下幾個方面展開研究:(1)介紹了在氯鹽環(huán)境下由于鋼絞線的腐蝕導(dǎo)致PC橋梁抗力退化的研究現(xiàn)狀,并分析目前國內(nèi)外在服役期間既有PC橋梁結(jié)構(gòu)面臨的問題和不確定性的研究現(xiàn)狀,還對鋼絞線的腐蝕影響因素進(jìn)行了分析討論。(2)在服役PC橋梁中,由于主觀因素和客觀因素等條件的影響,會產(chǎn)生各類無法預(yù)知的不確定性。文章介紹了PC橋梁在服役過程中不確定性的來源,如何將這些不確定性進(jìn)行分離和不確定性量化做了相關(guān)研究。本文利用似然函數(shù)和最大熵理論來處理由兩類數(shù)據(jù)來源引起的不確定性,這比不考慮不確定時(這種情況下是用最大似然估計法來計算的)更為可靠。(3)由于鋼絞線在化學(xué)成分和組織結(jié)構(gòu)的不同,使得鋼絞線在不利環(huán)境下的腐蝕與普通鋼筋的腐蝕有所不同。本文主要工作如下:首先,對普通鋼筋和鋼絞線在不利環(huán)境下的腐蝕形態(tài)特點(diǎn)進(jìn)行了比較分析;對于鋼絞線銹蝕主要后蝕坑的形狀進(jìn)行了討論,并且分析和總結(jié)了蝕坑的深度、長度和寬度的分布特征,最后利用似然函數(shù)的方法來討論基于小樣本數(shù)據(jù)不確定性條件下蝕坑的最大深度和最大寬度的PDF(概率密度函數(shù))。(4)在不利環(huán)境下,結(jié)合國內(nèi)外學(xué)者已經(jīng)推導(dǎo)的腐蝕后鋼絞線的承載力模型,并且在計算PC梁的承載力模型時引入變形協(xié)調(diào)系數(shù)能夠得到經(jīng)氯離子腐蝕以后PC梁的抗彎承載力模型。然后以一座受彎實(shí)橋為例,分析了在兩類數(shù)據(jù)不確定性條件下對抗力的影響。結(jié)果表明:以似然函數(shù)和最大熵理論來構(gòu)造變量的概率密度函數(shù),能夠減少主觀不確定性,由此得到的結(jié)果更加接近真實(shí)情況。
[Abstract]:In the existing prestressed concrete bridges in China, the number of PC bridges corroded by various adverse factors is increasing year by year, especially under the chloride environment. The corrosion of prestressed steel strands leads to the attenuation of the beam resistance, which seriously affects the safety of the bridge in service. On this basis, according to the likelihood function and maximum entropy theory. A method for analyzing the resistance degradation of PC bridges with uncertainty caused by two kinds of data (small sample and interval data) is established. The research status of PC bridge resistance degradation due to the corrosion of steel strands in chloride environment is introduced. The problems and uncertainties of existing PC bridges in service at home and abroad are analyzed, and the factors affecting the corrosion of steel strands are analyzed and discussed. Due to the influence of subjective factors and objective factors, various kinds of unpredictable uncertainties can be produced. This paper introduces the sources of uncertainty in the service of PC bridges. How to separate and quantify these uncertainties is studied. In this paper, the likelihood function and maximum entropy theory are used to deal with the uncertainty caused by two kinds of data sources. This is more reliable than when uncertainty is not taken into account (in this case the maximum likelihood estimation method is used) because of the different chemical composition and structure of the steel strands. The main work of this paper is as follows: firstly, the corrosion characteristics of common steel bar and steel strand in adverse environment are compared and analyzed; The shape of the main corrosion pits is discussed, and the distribution characteristics of the depth, length and width of the corrosion pits are analyzed and summarized. Finally, using the method of likelihood function, the PDF (probability density function) (PDF) of the maximum depth and width of the etch pits under the uncertainty of small sample data is discussed in the unfavorable environment. Combined with the domestic and foreign scholars have deduced the corrosion of steel strand bearing capacity model. When calculating the bearing capacity model of PC beam, the bending bearing capacity model of PC beam after chloride ion corrosion can be obtained by introducing the deformation coordination coefficient. Then, a real flexural bridge is taken as an example. The effect of antagonistic force on two kinds of data uncertainty is analyzed. The results show that the probability density function of variables can be reduced by using likelihood function and maximum entropy theory. The result is closer to reality.
【學(xué)位授予單位】：長沙理工大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2015
【分類號】：U441;U448.35

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本文編號：1403095