既有钢筋混凝土桥梁概率可靠度评估理论探索与工程应用

发布时间：2018-11-14 10:17

【摘要】：目前,既有桥梁评估的常用方法有传统经验法、检算系数法、系统综合法、可靠度分析法四种。可靠度分析方法是利用统计推断理论,分析影响结构可靠性的诸多不确定因素,运用可靠度理论评定可靠性水平,其中的概率可靠度方法具有概念清晰、目标明确的特点。概率可靠度理论在我国桥梁设计规范中已是实用阶段,但对于既有桥梁的评估我国目前采用的标度方法,几乎是纯经验的,这种方法简单且操作性强,但评估理论不够先进、评估体系不够健全、评估方法还有待完善。既有桥梁的概率可靠度评估是通过实测和分析,从而计算得到桥梁的结构抗力和荷载效应各自的统计参数,由于可靠指标比失效概率更为直观,且根据目前的研究成果,大多是规定结构的目标可靠指标或者最低可靠指标,根据所得抗力和效应的统计参数,计算可靠指标,并与最低可靠指标对比,从而判断既有桥梁可靠度是否符合要求。本文主要研究内容如下：(1)对结构可靠度理论进行了比较详细的论述,引出可靠指标,讨论了既有结构与拟建结构可靠度的区别和联系。(2)对引起既有钢筋混凝土桥梁性能退化与衰变的两大因素：混凝土碳化和钢筋锈蚀进行了详细分析,总结作用机理和时变规律,为既有钢筋混凝土桥梁的概率可靠度评估奠定了基础。(3)借鉴桥梁设计规范的有关公式,利用蒙特卡罗方法进行桥梁结构抗力分析,考虑荷载随时间的变化,采用合理的荷载概率模型,运用中心点法、JC法、映射变换法、实用分析法计算可靠指标,从原理出发,给出计算迭代步骤并对比分析方法的优劣。(4)以既有钢筋混凝土桥梁为工程实例,采用本文的分析方法,对桥梁跨中正截面抗弯承载能力进行可靠度分析,首先是荷载效应,其次是结构抗力,最后利用效应与抗力的统计参数计算得到其可靠指标,将结果与最低可靠指标对比,得出该桥梁跨中正截面抗弯承载能力可靠度符合要求。同时证明了概率可靠度方法具有较好的工程适应性,是一种更为客观合理的方法。
[Abstract]:At present, there are four common methods for bridge evaluation: traditional empirical method, checking and calculating coefficient method, system synthesis method and reliability analysis method. The reliability analysis method is to use statistical inference theory to analyze many uncertain factors that affect the reliability of structures, and to use reliability theory to evaluate the reliability level. The probability reliability method has the characteristics of clear concept and definite goal. The probabilistic reliability theory is a practical stage in the design code of bridges in our country. However, the scale method used at present for the evaluation of existing bridges in China is almost purely empirical. This method is simple and operable, but the evaluation theory is not advanced enough. The evaluation system is not perfect, and the evaluation method needs to be improved. The probabilistic reliability evaluation of the existing bridges is based on the measurement and analysis to calculate the statistical parameters of the structural resistance and load effect of the bridges. Because the reliability index is more intuitive than the failure probability, and according to the current research results, Most of them are the target reliability index or the lowest reliability index of the specified structure. According to the statistical parameters of the acquired resistance and effect, the reliability index is calculated and compared with the lowest reliability index, so as to judge whether the reliability of the existing bridge meets the requirements. The main contents of this paper are as follows: (1) the theory of structural reliability is discussed in detail, and the reliability index is derived. The difference and relation between the existing structure and the proposed structure reliability are discussed. (2) two major factors that cause the performance degradation and decay of the existing reinforced concrete bridge: concrete carbonization and reinforcement corrosion are analyzed in detail. Summing up the mechanism of action and time-varying law, it lays a foundation for the probabilistic reliability evaluation of existing reinforced concrete bridges. (3) based on the relevant formulas of bridge design code, Monte Carlo method is used to analyze the resistance of bridge structures. Considering the change of load with time, using reasonable load probability model, using center point method, JC method, mapping transformation method, practical analysis method to calculate the reliable index, starting from the principle, The iterative steps are given and the advantages and disadvantages of the analysis method are compared. (4) taking the existing reinforced concrete bridge as an engineering example, the reliability of the flexural bearing capacity of the normal section of the bridge span is analyzed by using the analytical method in this paper. The first is load effect, the second is structural resistance. Finally, the reliability index is obtained by calculating the statistical parameters of effect and resistance. By comparing the results with the lowest reliability index, it is concluded that the reliability of the flexural capacity of the bridge in the middle section of the bridge meets the requirements. It is proved that the probabilistic reliability method has better engineering adaptability and is a more objective and reasonable method.
【学位授予单位】：云南大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：U441;U448.34

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