斜拉索腐蚀损伤与安全性能评定方法研究

发布时间：2018-01-06 03:06

本文关键词：斜拉索腐蚀损伤与安全性能评定方法研究　出处：《重庆交通大学》2014年硕士论文　论文类型：学位论文

【摘要】：对于现代斜拉桥梁来说，拉索系统是其主要承重构件，旧有的斜拉桥结构在使用过程中由于不利作用，，受到应力和腐蚀等因素的影响，致使存在各种缺陷和损伤。大量事故表明，拉索的损伤通常会引起桥梁结构力学特性发生改变，进而影响到桥梁结构的安全性、耐久性以及使用寿命。故对损伤后的拉索进行安全性能评估尤为重要。本文依托973计划前期研究专项课题桥梁结构行为演化理论与安全监测方法研究。本文首先介绍了拉索的损伤检测评估及安全性能等方面的现状，指出缆索氋强钢丝破坏的主要形式是应力腐蚀及腐蚀疲劳破坏。对缆索高强钢丝的无应力、静态应力和交变应力三种受力方式进行酸性盐雾试验，研究受点蚀、应力腐蚀及腐蚀疲劳损伤后的拉索的损伤演化过程及安全性能。 ①根据三种损伤状态，对镀锌钢丝进行酸性盐雾腐蚀试验，把钢丝损伤的过程描述为5个阶段：钢丝完好→钢丝镀锌层锈蚀、钢丝基质均匀锈蚀→钢丝基质轻微点蚀→钢丝基质大量坑蚀→钢丝发生应力腐蚀和腐蚀疲劳，并制定Ⅴ级腐蚀对应的腐蚀图例。对各级钢丝图像进行灰度分析，提出一种基于表层图像分析锈蚀拉索技术状况的评定方法。根据盐雾腐蚀试验及拉伸试验数据，选取数据相关性较好的腐蚀失重、抗拉强度及断后伸长率为特征参量，给出各级钢丝的级评定标准。 ②建立了半球形的点蚀坑模型，计算了不同失重下的蚀坑深度，给出了点蚀坑腐蚀速率的计算公式。根据实验条件为参数，计算钢丝材料的断裂韧性KIC=117.6MPa m，通过断裂韧性求得应力腐蚀强度因子阈值KISCC=46.8。最后根据损伤力学理论提出应力腐蚀损伤演化模型。根据应力强度因子准则，计算了当应力比R=0时的腐蚀疲劳裂纹扩展阈值K th3.64。 ③引入了等效裂纹深度的概念，根据等效裂纹深度计算等效应力强度因子。将钢丝裂纹的三维模型巧妙的转化为平面应变问题，采用直线外推法，用有限元软件ANSYS模拟不同蚀坑深度下裂纹尖端的应力强度因子值。并与理论计算值相比较。提出基于断裂韧性的剩余强度的计算方法，最后根据破损安全理论，给出腐蚀疲劳损伤的破损安全设计，并给出单根钢丝进行安全破损的评估流程。 ④采用有限元模拟不同锈蚀程度下单根钢丝和整根拉索的锈蚀模型。结果表明：蚀坑深度越大，深坑底部应力集中系数越大。把整根拉索的锈蚀分为5级来模拟不同锈蚀程度对拉索应力的影响，最大等效应力出现在最外层钢丝之间的接触区域；随着腐蚀等级的提高，腐蚀拉索截面的应力整体提高。
[Abstract]:For the modern cable-stayed bridge, the cable system is the main load-bearing components, cable-stayed bridge structure of the old in use because of adverse effects, by the influence of stress corrosion and other factors, resulting in various defects and damage. Many accidents show that the cable damage often causes the bridge structure mechanical properties change, and affect the bridge safety, durability and service life. So the safety performance evaluation of cable injury is particularly important.
The research on evolution theory and safety monitoring method based on the 973 research program of special subject of bridge structure behavior. This paper introduces the present situation of the cable damage detection and evaluation of safety performance and other aspects, and points out that the main form of cable Meng strong steel wire breakage is stress corrosion and corrosion fatigue damage. The stress free cable of high-strength steel. Static stress and alternating stress three stress modes of acid salt spray test of pitting corrosion, stress corrosion and corrosion fatigue damage after the cable damage evolution process and safety performance.
According to the three kinds of damage state, acid salt spray corrosion test of galvanized steel wire, steel wire damage process is described as 5 stages: wire intact, galvanized layer of steel wire corrosion, steel wire, steel wire matrix matrix of uniform corrosion, mild pitting corrosion, large steel wire matrix occurred stress corrosion and corrosion fatigue, corrosion legend and make the V-grade corrosion. Corresponding gray image analysis for all levels of steel put forward a kind of evaluation method, surface image analysis technology based on cable corrosion condition. According to the salt spray corrosion test and tensile test data, select the better correlation of corrosion data loss, tensile strength and elongation parameters are given steel grade evaluation standard.
It has established a model of hemispherical pits, pit depth was calculated under different weight loss, gives the calculation formula of pitting corrosion rate. According to the experimental conditions for the parameter calculation of steel material fracture toughness of KIC=117.6MPa m, the fracture toughness obtained stress corrosion strength due to sub threshold KISCC=46.8. based on the theory of damage mechanics is put forward stress corrosion damage evolution model. According to the stress intensity factor criterion is calculated when the stress ratio of corrosion fatigue crack propagation threshold K th3.64. R=0
The concept of the equivalent crack depth, crack depth according to the equivalent calculation of equivalent stress intensity factor. The 3D model of wire crack transformation skillfully as a problem of plane strain, using linear extrapolation method, using finite element software ANSYS to simulate the stress intensity factor of the crack tip under different corrosion pit depth. And the calculated values are compared with the the theory. Put forward the calculation method of residual strength fracture toughness based, according to the failure safety theory, failure safety design gives corrosion fatigue damage, and gives a single wire breakage safety assessment process.
The corrosion model of single wire and the whole cable finite element simulation of different corrosion levels. The results showed that the greater the depth of corrosion pit, pit bottom stress concentration coefficient is big. The whole cable corrosion is divided into 5 levels to simulate the effects of different degrees of corrosion on the cable stress, contact area of maximum von Mises force appears in between the outermost layer of steel wire; with the increasing level of corrosion, stress corrosion of cable section of the overall improvement.

【学位授予单位】：重庆交通大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：U448.27;U443.38

【参考文献】