本文選題：預(yù)應(yīng)力混凝土結(jié)構(gòu)　切入點(diǎn)：鋼絞線　出處：《中國礦業(yè)大學(xué)》2014年碩士論文　論文類型：學(xué)位論文

【摘要】：預(yù)應(yīng)力混凝土結(jié)構(gòu)廣泛應(yīng)用于國家和城市生命線等重要工程之中，其中許多結(jié)構(gòu)在其服役壽命期間會同時受到環(huán)境腐蝕作用和力學(xué)疲勞作用的共同影響，從而會使結(jié)構(gòu)發(fā)生腐蝕疲勞耦合損傷乃至破壞，最終釀成極其嚴(yán)重的后果。為此，本文針對其中氯鹽環(huán)境預(yù)應(yīng)力混凝土結(jié)構(gòu)中鋼絞線的腐蝕疲勞損傷演化進(jìn)程這一具體問題展開研究，以期為系統(tǒng)解決PC結(jié)構(gòu)的腐蝕疲勞問題提供階段性成果。 基于力筋腐蝕疲勞損傷的聲發(fā)射監(jiān)測需要，首先通過試驗(yàn)研究了混凝土握裹鋼絞線中聲波傳播的衰減規(guī)律以及若干混凝土狀況對其衰減的影響情況，結(jié)果表明，聲發(fā)射信號強(qiáng)度會隨傳播距離的增大而迅速減�。茨芰俊⒎�、持續(xù)時間和振鈴計(jì)數(shù)等聲波參數(shù)的衰減率隨著傳播距離的增大而迅速增大）；保護(hù)層厚度和水灰比越大，聲波衰減越多；孔隙水飽和度越大，聲波衰減越少；同時，，在試驗(yàn)結(jié)果的基礎(chǔ)上，結(jié)合理論分析建立了上述各因素影響下的聲波衰減預(yù)計(jì)模型。 通過疲勞耦合下鋼絞線腐蝕電位的測量，并以氯離子對PC結(jié)構(gòu)侵蝕機(jī)理為基礎(chǔ)，建立了考慮疲勞應(yīng)力幅影響的氯鹽環(huán)境鋼絞線腐蝕速率模型，并進(jìn)行了模型參數(shù)的討論。研究表明，隨疲勞應(yīng)力幅的增大，鋼絞線的腐蝕速率也增大，影響趨勢呈指數(shù)函數(shù)關(guān)系。 疲勞耦合下鋼絞線坑蝕特征試驗(yàn)研究表明：疲勞作用對預(yù)應(yīng)力鋼絞線的坑蝕特征有影響，具體表現(xiàn)為蝕坑的長度、寬度和深度均隨疲勞應(yīng)力幅的增大而增大；同時提出疲勞作用下蝕坑體積損傷分布特征和蝕坑力學(xué)損傷指數(shù)的分布特征，研究表明上述兩種損傷均隨疲勞應(yīng)力幅的增大而增大。 通過聲發(fā)射監(jiān)測儀器對腐蝕耦合下預(yù)應(yīng)力鋼絞線的疲勞損傷進(jìn)程進(jìn)行了研究，結(jié)果表明，能量、撞擊數(shù)和振鈴計(jì)數(shù)等聲發(fā)射參數(shù)能夠較好的表征鋼絞線的損傷進(jìn)程；通過分析上述參數(shù)，發(fā)現(xiàn)腐蝕程度與疲勞應(yīng)力幅大小對鋼絞線的疲勞損傷存在顯著影響：當(dāng)疲勞幅度一定時，摻鹽率越大，疲勞累積損傷越多；當(dāng)摻鹽率一定時，疲勞應(yīng)力幅越大，疲勞累積損傷越多。 腐蝕疲勞損傷鋼絞線的靜力拉伸試驗(yàn)表明，鋼絞線的最大承載力和極限平均應(yīng)變均隨著應(yīng)力幅的增大和摻鹽量的增大而降低。鋼絞線鋼絲可能出現(xiàn)劈裂式、杯椎式及銑刀式等三種基本斷口形式以及他們的組合形式。
[Abstract]:Prestressed concrete structures are widely used in important projects such as national and urban lifelines. Many of them are affected by both environmental corrosion and mechanical fatigue during their service life. This will lead to corrosion fatigue coupling damage and even destruction of the structure, and eventually lead to extremely serious consequences. In this paper, the evolution process of corrosion fatigue damage of steel strands in prestressed concrete structures in chloride environment is studied in order to provide a periodic achievement for the systematic solution of corrosion fatigue problems of PC structures. Based on the need of acoustic emission (AE) monitoring for corrosion fatigue damage of steel bars, the attenuation law of sound wave propagation in steel strands and the influence of some concrete conditions on its attenuation are studied through experiments. The results show that, The attenuation rate of acoustic wave parameters such as energy, amplitude, duration and ringing count increases rapidly with the increase of the propagation distance, and the thickness of the protective layer and the ratio of water to cement increase with the increase of the propagation distance. The more the acoustic wave attenuation, the less the acoustic wave attenuation is, the more the pore water saturation is, the less the acoustic wave attenuation is. At the same time, based on the experimental results, the prediction model of acoustic wave attenuation under the influence of the above factors is established by combining the theoretical analysis. By measuring the corrosion potential of steel strands under fatigue coupling and on the basis of the corrosion mechanism of chloride ions on PC structure, a corrosion rate model of steel strands in chloride environment considering the effect of fatigue stress amplitude is established. The model parameters are discussed. The results show that the corrosion rate of steel strands increases with the increase of fatigue stress amplitude, and the influence trend is exponential function. The experimental study on the pit corrosion characteristics of steel strands under fatigue coupling shows that fatigue action has an effect on the pit corrosion characteristics of prestressed steel strands, and the length, width and depth of the corrosion pits increase with the increase of fatigue stress amplitude. At the same time, the distribution characteristics of volume damage and mechanical damage index of pit under fatigue action are proposed. The results show that the above two kinds of damage increase with the increase of fatigue stress amplitude. The fatigue damage process of prestressed steel strand under corrosion coupling is studied by acoustic emission monitoring instrument. The results show that the acoustic emission parameters such as energy, impact number and ringing count can better characterize the damage process of steel strand. By analyzing the above parameters, it is found that the corrosion degree and fatigue stress amplitude have significant influence on fatigue damage of steel strand: when the fatigue amplitude is constant, the fatigue cumulative damage increases with the increase of salt addition ratio, and when the salt content is constant, The greater the fatigue stress amplitude, the more fatigue cumulative damage. The static tensile test of corrosion-fatigue damaged steel strand shows that the maximum bearing capacity and ultimate average strain of steel strand decrease with the increase of stress amplitude and salt content. Cup type and milling cutter are three basic fracture forms and their combination.
【學(xué)位授予單位】：中國礦業(yè)大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2014
【分類號】：TU378

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