盐雾与疲劳耦合下预应力箱梁氯离子扩散特性研究

发布时间：2018-05-23 17:28

本文选题：疲劳荷载 + 盐雾区　；参考：《哈尔滨工业大学》2015年硕士论文

【摘要】：预应力跨海铁路桥的箱梁位于盐雾区,工作环境极其恶劣,常年遭受疲劳荷载与盐雾侵蚀的双重耦合作用。在这种双重耦合作用下,预应力钢筋的锈蚀速度、混凝土的开裂程度与箱梁的力学性能劣化程度均会大幅增加,这会直接对铁路桥的安全构成极大的威胁。本文针对盐雾区的预应力铁路桥箱梁进行疲劳荷载与氯离子侵蚀耦合作用下的氯离子分布性研究,研究结果有助于提高预应力铁路桥箱梁的耐久性、完善其耐久性设计理论体系。首先,以ANSYS自带的热-结构耦合模块计算耦合作用下的氯离子分布情况。由于该模块具有局限性,计算所得的氯离子分布结果并不准确,因此以体积应变与孔隙率作为中间变量,给出从静荷载到体积应变、从体积应变到孔隙率,再从孔隙率到氯离子传递系数的耦合计算过程。对于疲劳荷载,则通过ANSYS中的疲劳分析模块计算损伤度D,并以基于应变的疲劳损伤理论作为依据,计算疲劳荷载作用下的残余应变与总应变,然后给出从疲劳荷载到体积应变再到氯离子传递系数的计算过程。最后将利用上述方法计算得到的结果与已有试验结果进行对比。其次,建立预应力混凝土箱梁的精细化有限元模型。对预应力箱梁模型分别施加规范规定的静活载与统计得到的疲劳荷载,计算盐雾区静活载、疲劳荷载与氯离子侵蚀耦合时箱梁内部的氯离子分布规律。同时,对比静活载耦合与疲劳荷载耦合下的氯离子分布结果,研究不同荷载形式对耦合结果的影响。最后,在分别考虑盐雾——静活载耦合与盐雾——疲劳荷载耦合的同时,对箱梁内部的预应力水平做出改变,研究不同预应力水平对箱梁内部氯离子渗透性的影响,并对比不同预应力水平下静活载耦合与疲劳荷载耦合的计算结果。另外,对箱梁模型施加不同应力水平的疲劳荷载,研究盐雾-疲劳荷载耦合情况下不同应力水平对计算结果的影响。最后,基于ANSYS提出盐雾与疲劳的多次耦合分析法,将单次耦合与多次耦合的计算结果进行对比并分析。
[Abstract]:The box girder of the prestressed cross-sea railway bridge is located in the salt fog area, and the working environment is extremely bad, and it is subjected to the coupling action of fatigue load and salt spray erosion all the year round. Under this kind of double coupling action, the corrosion speed of prestressed steel bar, the cracking degree of concrete and the deterioration degree of mechanical properties of box girder will increase greatly, which will pose a great threat to the safety of railway bridge directly. In this paper, the distribution of chloride ions in the box girder of prestressed railway bridge in salt fog region under the coupling of fatigue load and chloride ion erosion is studied. The results are helpful to improve the durability of the box girder of prestressed railway bridge. Perfect its durability design theory system. Firstly, the distribution of chloride ions under coupling action is calculated by using the thermo-structural coupling module of ANSYS. Because of the limitation of the module, the calculated results of chloride ion distribution are not accurate. Therefore, the volume strain and porosity are used as the intermediate variables, from static load to volume strain, from volume strain to porosity. Then the coupling calculation process from porosity to chloride ion transfer coefficient is presented. For the fatigue load, the damage degree D is calculated by the fatigue analysis module in ANSYS, and the residual strain and the total strain under the fatigue load are calculated according to the strain based fatigue damage theory. Then the calculation process from fatigue load to volume strain to chloride ion transfer coefficient is given. Finally, the calculated results obtained by the above method are compared with the experimental results. Secondly, the fine finite element model of prestressed concrete box girder is established. The prestressed box girder model is subjected to the static live load and the statistical fatigue load, respectively, and the distribution of chloride ions in the box girder is calculated when the fatigue load is coupled with the chloride ion erosion in the salt fog region. At the same time, the results of chloride ion distribution under the coupling of static and live load and fatigue load are compared, and the influence of different load forms on the coupling results is studied. Finally, considering the coupling of salt fog and static live load and salt fog fatigue load, the prestress level of box girder is changed, and the influence of different prestress levels on the chlorine ion permeability of box girder is studied. The calculation results of static and live load coupling and fatigue load coupling under different prestress levels are compared. In addition, fatigue loads with different stress levels are applied to the box girder model, and the influence of different stress levels on the calculation results is studied under the coupling of salt fog and fatigue load. Finally, based on ANSYS, the multiple coupling analysis method of salt fog and fatigue is proposed, and the results of single coupling and multiple coupling are compared and analyzed.
【学位授予单位】：哈尔滨工业大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：U441;U448.35

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