腐蚀预应力筋的力学性能研究

发布时间：2018-04-17 13:59

本文选题：预应力筋 + 腐蚀　；参考：《长沙理工大学》2015年硕士论文

【摘要】：目前,关于预应力混凝土构件中的预应力筋腐蚀问题日益突出,但相关研究尚处于起步阶段。因此,本文对腐蚀预应力筋的力学性能退化规律展开了研究。通过人工气候下的腐蚀试验获取腐蚀预应力筋试件,然后由静力拉伸试验研究腐蚀预应力筋的力学性能,并构建其本构关系模型。拉伸后,对每根钢丝蚀坑尺寸的观察与记录来研究腐蚀预应力筋蚀坑的概率分布规律;再通过电镜扫描(SEM)试验从微观结构观察腐蚀预应力筋的破坏形态,具体工作如下:(1)通过对腐蚀预应力筋断口宏观及微观的观察发现:所有预应力筋均有着相似的破坏形态,未腐蚀和腐蚀较轻的钢丝破坏形态为延性断裂,断口表现出颈缩现象;随着腐蚀率增加,腐蚀钢丝的破坏形态从延性断裂逐渐向脆性断裂转变,断口无明显颈缩现象。(2)拉伸试验的结果表明:在腐蚀率较低的情况下,预应力筋的极限应变随腐蚀率近似地线性降低,极限强度轻微下降;腐蚀对预应力筋弹性模量与屈服强度影响较小;当腐蚀率增大到临界值后,预应力筋的破坏方式表现为脆性失效;预应力筋轻度腐蚀时,其本构模型可用弹性-硬化双线性模型表征,当腐蚀率超过临界值时,其本构关系转变为单线性模型。(3)对腐蚀钢丝蚀坑的尺寸进行统计分析发现:蚀坑的几何形状主要分为棱锥型、椭球型及类圆锥型3大类。通过数据推导和假设验证,发现腐蚀预应力筋蚀坑的尺寸参数最大深度的概率分布为极值Ⅰ型分布;深宽比呈对数正态分布;最大宽度无明显的概率分布规律,其值主要集中在中等宽度区间[2mm,4mm]上。(4)蚀坑尺寸参数的统计分析表明:蚀坑的最大深度随着腐蚀率的增加而增大,但其增大速率渐缓;深宽比亦随着腐蚀率的增加而增大,蚀坑处的应力集中现象也随之加剧;最大宽度与腐蚀率之间无明显相对应的线性关系。
[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.
【学位授予单位】：长沙理工大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TU378

【参考文献】