本文選題：預應力筋 + 腐蝕　； 參考：《長沙理工大學》2015年碩士論文

【摘要】：目前,關于預應力混凝土構件中的預應力筋腐蝕問題日益突出,但相關研究尚處于起步階段。因此,本文對腐蝕預應力筋的力學性能退化規(guī)律展開了研究。通過人工氣候下的腐蝕試驗獲取腐蝕預應力筋試件,然后由靜力拉伸試驗研究腐蝕預應力筋的力學性能,并構建其本構關系模型。拉伸后,對每根鋼絲蝕坑尺寸的觀察與記錄來研究腐蝕預應力筋蝕坑的概率分布規(guī)律;再通過電鏡掃描(SEM)試驗從微觀結構觀察腐蝕預應力筋的破壞形態(tài),具體工作如下:(1)通過對腐蝕預應力筋斷口宏觀及微觀的觀察發(fā)現(xiàn):所有預應力筋均有著相似的破壞形態(tài),未腐蝕和腐蝕較輕的鋼絲破壞形態(tài)為延性斷裂,斷口表現(xiàn)出頸縮現(xiàn)象;隨著腐蝕率增加,腐蝕鋼絲的破壞形態(tài)從延性斷裂逐漸向脆性斷裂轉(zhuǎn)變,斷口無明顯頸縮現(xiàn)象。(2)拉伸試驗的結果表明:在腐蝕率較低的情況下,預應力筋的極限應變隨腐蝕率近似地線性降低,極限強度輕微下降;腐蝕對預應力筋彈性模量與屈服強度影響較小;當腐蝕率增大到臨界值后,預應力筋的破壞方式表現(xiàn)為脆性失效;預應力筋輕度腐蝕時,其本構模型可用彈性-硬化雙線性模型表征,當腐蝕率超過臨界值時,其本構關系轉(zhuǎn)變?yōu)閱尉�性模型。(3)對腐蝕鋼絲蝕坑的尺寸進行統(tǒng)計分析發(fā)現(xiàn):蝕坑的幾何形狀主要分為棱錐型、橢球型及類圓錐型3大類。通過數(shù)據(jù)推導和假設驗證,發(fā)現(xiàn)腐蝕預應力筋蝕坑的尺寸參數(shù)最大深度的概率分布為極值Ⅰ型分布;深寬比呈對數(shù)正態(tài)分布;最大寬度無明顯的概率分布規(guī)律,其值主要集中在中等寬度區(qū)間[2mm,4mm]上。(4)蝕坑尺寸參數(shù)的統(tǒng)計分析表明:蝕坑的最大深度隨著腐蝕率的增加而增大,但其增大速率漸緩;深寬比亦隨著腐蝕率的增加而增大,蝕坑處的應力集中現(xiàn)象也隨之加劇;最大寬度與腐蝕率之間無明顯相對應的線性關系。
[Abstract]:At present, the corrosion of prestressed tendons in prestressed concrete members is becoming more and more serious, but the related research is still in its infancy.Therefore, the degradation of mechanical properties of corroded prestressed tendons is studied in this paper.The specimens of corroded prestressed tendons were obtained by the corrosion test under artificial climate. Then the mechanical properties of corroded prestressed tendons were studied by static tensile test and their constitutive relation models were established.After drawing, the probability distribution of corroded prestressing tendons was studied by observing and recording the size of each steel wire corrosion pit, and the failure pattern of corroded prestressing tendons was observed from the microstructure by scanning electron microscope (SEM) test.The concrete work is as follows: (1) through the macroscopic and microscopic observation on the fracture of corroded prestressed tendons, it is found that all prestressed tendons have similar failure patterns, and the failure patterns of non-corroded and less corroded steel wires are ductile fracture, and the fracture surface shows necking phenomenon;With the increase of corrosion rate, the failure pattern of corroded steel wire gradually changed from ductile fracture to brittle fracture, and no obvious necking phenomenon was observed on the fracture surface. The results of tensile test showed that: under the condition of low corrosion rate, the corrosion rate of corroded steel wire changed gradually from ductile fracture to brittle fracture.The ultimate strain of prestressed tendons decreases linearly with the corrosion rate, and the ultimate strength decreases slightly; the corrosion has little effect on the elastic modulus and yield strength of prestressed tendons; when the corrosion rate increases to the critical value, when the corrosion rate increases to the critical value,The failure mode of prestressing tendons is brittle failure, and the constitutive model of prestressed tendons can be represented by elastic-hardening bilinear model when the corrosion rate exceeds the critical value.Its constitutive relation is transformed into a single linear model. (3) the size of the corroded steel wire pit is statistically analyzed. It is found that the geometric shape of the etched pit is mainly divided into three categories: pyramid type, ellipsoid type and cone-like type.Through the data derivation and hypothesis verification, it is found that the probability distribution of the maximum depth of the dimension parameters of the corroded prestressing tendons is extreme type I distribution, the aspect ratio is logarithmic normal distribution, and the maximum width has no obvious probability distribution rule.The statistical analysis of the size parameters of the pit is mainly concentrated in the middle width range [2mm / 4mm]. The results show that the maximum depth of the pit increases with the increase of corrosion rate, but the increasing rate of the pit increases slowly, and the aspect ratio increases with the increase of corrosion rate.The stress concentration in the pit is also increased, and there is no obvious linear relationship between the maximum width and the corrosion rate.
【學位授予單位】：長沙理工大學
【學位級別】：碩士
【學位授予年份】：2015
【分類號】：TU378

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