冻融循环作用下预应力混凝土梁疲劳特性研究

发布时间：2019-03-06 17:22

【摘要】：从20世纪50年代至今,预应力混凝土结构逐步成为当今建筑以及交通领域主流的结构类型,其中预应力混凝土桥梁作为交通运输中的重要纽带,其结构耐久性备受各国学者关注。桥梁结构在正常服役期间,长期暴露在大气当中,在不断受到交通循环荷载作用的同时不可避免会遭受外界不利环境诸如碳化侵蚀、氯离子侵蚀和冻融侵蚀等因素影响。其中冻融循环作用已被证实为影响桥梁结构耐久性的重要因素之一,正因为预应力混凝土桥梁结构在交通运输系统中发挥着核心枢纽的作用,所以研究冻融作用下预应力混凝土结构的耐久性劣化机理及其对结构疲劳特性的影响具有重要的理论价值和工程意义,同时也是正确评价服役桥梁健康状况和剩余寿命的前提。本文在预应力混凝土梁冻融循环侵蚀试验的基础上开展疲劳循环加载试验,并辅以数值模拟计算,研究并分析冻融循环作用下预应力混凝土梁的疲劳特性变化规律及其相关关系。本文主要研究内容如下:1、冻融循环作用下预应力混凝土梁动静力学性能试验研究根据相关混凝土耐久性试验规范,提出了一种针对大型混凝土构件进行冻融试验的方法,开展预应力混凝土梁和混凝土立方体试件冻融循环试验。通过经受不同次数(0、50、75、100次)冻融循环作用试件表观现象、抗压强度和动弹性模量等试验结果,分析研究冻融循环以及冻融次数对混凝土材料力学性能的影响;对经受不同冻融循环次数的预应力混凝土梁进行动静载试验,基于对试验梁动静载作用下结构的位移和应变等,研究冻融循环作用下预应力混凝土梁动静力学性能变化情况。2、不同冻融循环次数下预应力混凝土梁疲劳性能试验研究对经受不同冻融循环次数的预应力混凝土梁进行周期为50万次的疲劳试验,每做50万次疲劳加载试验,进行一次试验梁动静载试验,研究疲劳循环加载作用下结构耐久性、力学性能指标(挠度、应变、结构基频和动态位移)变化规律,建立冻融循环作用下预应力混凝土试验梁疲劳寿命预估公式。3、不同冻融循环次数下预应力混凝土梁受力特性数值模拟分析基于静力试验和结论,利用迈达斯公司Midas FEA软件建立试验梁数值模型,分析不同冻融循环作用下预应力混凝土梁的受力性能及变化规律,分别从冻融循环侵蚀后试验梁线性静力性能变化和非线性裂缝开展上,表征不同冻融循环次数下试验梁受力变化规律,并与试验结果做对比验证,提出一种研究冻融循环作用下预应力混凝土梁力学特性的数值分析方法。
[Abstract]:From the 1950s to the present, prestressed concrete structure has gradually become the mainstream structure type in the field of architecture and transportation, in which prestressed concrete bridge is an important link in transportation. The durability of the structure is concerned by scholars all over the world. During the normal service period, the bridge structure is exposed to the atmosphere for a long time. It is inevitable that the bridge structure will be affected by the external adverse environment such as carbonation, chloride ion erosion and freeze-thaw erosion at the same time it is constantly subjected to the traffic cyclic load at the same time. The freeze-thaw cycle has been proved to be one of the important factors affecting the durability of the bridge structure, because the prestressed concrete bridge structure plays a key role in the transportation system. Therefore, it is of great theoretical value and engineering significance to study the durability deterioration mechanism of prestressed concrete structure under freeze-thaw action and its influence on the fatigue characteristics of the structure, and it is also the premise of correctly evaluating the health status and residual life of the bridge in service. In this paper, fatigue cyclic loading tests are carried out on the basis of freeze-thaw cyclic erosion test of prestressed concrete beams, supplemented by numerical simulation calculation. The fatigue characteristics of prestressed concrete beams under freeze-thaw cycle are studied and analyzed. The main contents of this paper are as follows: 1. The dynamic and dynamic mechanical properties of prestressed concrete beams subjected to freeze-thaw cycle are studied. According to the relevant concrete durability test code, a method of freeze-thaw test for large-scale concrete members is put forward. The freeze-thaw cycle tests of prestressed concrete beams and concrete cube specimens were carried out. The effects of freezing-thawing cycles and freezing-thawing times on the mechanical properties of concrete were analyzed through the experimental results of the apparent phenomena, compressive strength and dynamic elastic modulus of specimens subjected to different freezing-thawing cycles (0,50,75100 times). The dynamic static loading test of prestressed concrete beams subjected to different freezing and thawing cycles is based on the displacement and strain of the structure under dynamic static loading of the tested beams. The changes of dynamic and dynamic mechanical properties of prestressed concrete beams under freeze-thaw cycle are studied. 2, Experimental study on fatigue behavior of Prestressed concrete Beams under different Frost-thaw cycles the fatigue tests of prestressed concrete beams subjected to different freezing-thawing cycles are carried out with a period of 500000 times and every 500000 fatigue loading tests are carried out on the prestressed concrete beams subjected to different freezing-thawing cycles. A static-static load test of a test beam was carried out to study the structural durability, mechanical properties (deflection, strain, fundamental frequency and dynamic displacement) of the structure under fatigue cyclic loading. The fatigue life prediction formula of prestressed concrete beam under freeze-thaw cycle is established. 3. Based on the static test and conclusion, the numerical simulation analysis of prestressed concrete beam under different freezing-thawing cycles is based on the static test and conclusion. The numerical model of test beam is established by using Midas FEA software of Midas Company, and the mechanical behavior and variation rule of prestressed concrete beam under different freeze-thaw cycles are analyzed. On the basis of the linear static performance change and nonlinear crack development of the test beam after freezing-thawing cycle erosion, the change rule of the test beam force under different freezing-thawing cycles is characterized, and compared with the experimental results, the experimental results are verified by comparing with the experimental results. A numerical analysis method for mechanical properties of prestressed concrete beams subjected to freeze-thaw cycles is presented.
【学位授予单位】：郑州大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：U441.4

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