【作者】 李浩；

【导师】 涂熙； 肖正直；

【作者基本信息】 重庆大学 ， 工程（建筑与土木工程）（专业学位）， 2020， 硕士

【摘要】 钢-混凝土组合梁通过抗剪连接件将钢梁与混凝土板组合而共同工作,兼具钢结构和混凝土结构的优点。对于处于海洋或者恶劣环境下的组合结构,环境中氯离子侵蚀作用引起栓钉锈蚀,导致栓钉力学性能下降,严重影响组合结构的整体性能。由于在役组合结构中栓钉锈蚀监测较困难,准确模拟混凝土中氯离子扩散引起的栓钉锈蚀过程显得尤为重要。本文将混凝土中氯离子扩散与栓钉锈蚀耦合分析,研究组合结构服役期内的栓钉锈蚀过程和力学性能退化规律。本文主要研究内容如下:(1)建立氯离子扩散和钢材锈蚀的耦合分析方法。基于Butler–Volmer方程和混凝土中钢材锈蚀电化学反应,编程实现单个时间步长内混凝土中钢材锈蚀迭代计算,并通过积分实现长期锈蚀计算。引入了氯离子扩散模块,考虑混凝土中氯离子浓度升高引起的钢筋脱钝,建立了氯离子扩散和钢材锈蚀耦合计算程序。给出边区和角区钢筋的耦合分析计算实例,验证了该程序计算结果的合理性。(2)采用氯离子扩散和钢材锈蚀的耦合计算栓钉的长期锈蚀过程。设定了两种氯离子暴露面,当混凝土板顶面为暴露面时,锈蚀位置随时间逐渐往下发展,栓钉横截面保持圆形,顶杆长度方向锈蚀形态为“两头粗中间细。当混凝土板底面为暴露面时,锈蚀位置随时间逐渐往上方发展,栓钉横截面接近椭圆形,顶杆长度方向锈蚀形态为“上端粗下端细。栓钉锈蚀呈规律如下:越靠近边界混凝土的位置越早产生锈蚀,锈蚀深度也越大,锈蚀位置朝氯离子扩散方向基本一致。(3)由于锈蚀栓钉的不规则形态不便于有限元建模计算,对锈蚀栓钉的形态进行简化处理,建模分析两种氯离子暴露面下的栓钉在不同锈蚀时间的力学性能,分别得到两种栓钉随时间变化的力学性能退化曲线。结论如下:栓钉极限抗剪承载力也随着暴露时间增加逐渐下降,暴露100年两种栓钉的极限抗剪承载力均降至原来的半左右,相同条件下底面为暴露面的的栓钉承载力下降风险更大。更多还原

【Abstract】 Steel-concrete composite beams work by combining steel beams and concrete slabs through shear connectors,and have the advantages of both steel and concrete structures.For a combined structure in an ocean or harsh environment,the corrosion of chloride ions in the environment causes corrosion of the stud,resulting in a drop in the mechanical properties of the stud,which seriously affects the overall performance of the combined structure.Since it is difficult to monitor the corrosion of studs in composite structures in service,it is particularly important to accurately simulate the stud corrosion process caused by the diffusion of chloride ions in concrete.In this paper,the coupling analysis of chloride ion diffusion and stud corrosion in concrete is carried out to study the stud corrosion process and the degradation law of mechanical properties of composite structures during their service life.The main research contents of this article are as follows:(1)Establish a coupling analysis method for chloride ion diffusion and steel corrosion.Based on the Butler–Volmer equation and the electrochemical reaction of steel corrosion in concrete,iteratively calculates the iterative calculation of steel corrosion in concrete in a single time step,and implements long-term corrosion calculation through integration.A chloride ion diffusion module was introduced to take into account the desensitization of steel bars caused by the increase of chloride ion concentration in concrete,and a coupling calculation program for chloride ion diffusion and steel corrosion was established.An example of coupled analysis and calculation of reinforcement in the side and corner areas is given to verify the rationality of the calculation results of the program.(2)The long-term corrosion process of studs is calculated by the coupling of chloride ion diffusion and steel corrosion.There are two kinds of chloride ion exposed surfaces.When the top surface of the concrete slab is the exposed surface,the corrosion position gradually develops downward over time,the cross section of the stud remains round,and the form of corrosion in the length direction of the top rod is "two ends thick and thin.When the bottom surface of the concrete slab is the exposed surface,the location of corrosion gradually develops upwards with time.The cross section of the stud is close to an ellipse,and the form of corrosion in the length direction of the top rod is "the upper end is thicker and the lower end is thinner." The rule of bolt corrosion is as follows: the closer to the boundary concrete,the earlier the corrosion occurs,and the greater the depth of corrosion,the location of the corrosion is basically the same as the direction of chloride ion diffusion.(3)Since the irregular shape of the corroded studs is not convenient for finite element modeling and calculation,the shape of the corroded studs is simplified,and the mechanical properties of the studs under the two chloride ion exposed surfaces at different corrosion times are modeled and analyzed,respectively.The mechanical degradation curve of two kinds of studs with time.The conclusions are as follows: the ultimate shear bearing capacity of studs also gradually decreases with the increase of exposure time.The ultimate shear bearing capacity of two types of studs after 100 years of exposure has decreased to about half of the original.Under the same conditions,the studs with the bottom surface as the exposed surface The risk of reduced bearing capacity is greater.更多还原