【作者】 李志远；

【导师】 金伟良；

【作者基本信息】 浙江大学 ， 结构工程， 2016， 博士

【摘要】 耐久性是混凝土结构的基本性能,是结构可靠性的重要组成部分。如何确定和评价混凝土结构的寿命则是混凝土结构耐久性的重要问题。目前,混凝土结构的寿命评估主要是依据理论模型和耐久性试验来获得的,而由混凝土耐久性理论模型和试验所获得的信息尚不能完全反映真实环境下混凝土结构的所有信息。建立耐久性理论模型和试验与真实结构的相似关系是保障寿命评价的关键。本文拟在混凝土结构耐久性的多重环境时间相似理论(Multi-environmental time similarity theory, METS)基础上,运用信息理论和相对信息概念,对混凝土结构耐久性寿命评估理论模型和试验的信息不完备性和结果的真实性进行了深入系统的研究,提出了基于相对信息多重环境时间相似理论(Multi-environmental time similarity theory based on relative information, RI-METS),不仅完善了混凝土结构耐久性评估理论体系,而且丰富和发展了工程结构可靠性的不确定性分析方法。具体研究内容如下：(1)为了将耐久性理论模型和试验的信息用于自然环境下混凝土结构中,在METS的基础上,建立基于相对信息多重环境时间相似理论。为扩展METS理论的应用范围,解决METS理论不能处理多信息源、多观察路径的问题,提出METS路径的概念,并将METS路径分为METS(1;1)型、METS(i;1)型、METS(1;j)型和METS(i;j)型4种类型。为了解决METS理论信息相对性的问题,采用相对信息熵来表征信息的相对性。语法信息熵和语义信息熵是观察者观察系统获得的相对信息熵的2个维度,分别采用Shannon信息熵和模糊熵来计算。采用闵氏观察角的双曲正切函数来表征观察者效应。采用各METS路径闵氏观察角来对各METS路径进行信息融合。为了使观察者可以从各条METS路径中选择最优路径做决策,采用效用度函数来评价METS路径的信息有效性。(2)在没有实测数据或加速耐久性试验数据的情况下,结构工程师可依据已有的规范进行耐久性设计和寿命评估。为了全面的获取已有规范的信息,总结中国、欧洲和美国的相关规范,从指定设计法、避免劣化法、基于性能和可靠度的设计方法3方面构建和描述设计规范系统。为了统一不同规范所划分的环境,建立了中欧美规范关于自然环境对照表,将自然环境细分为5大类21种。(3)为了在一般大气环境下建立耐久性理论模型和试验与真实结构的相似关系,建立一般大气环境下的RI-METS理论,给出一般大气环境下各变量的相似率、相似准数公式以及相对信息熵计算公式。选择混凝土碳化深度达到保护层厚度作为一般大气环境下的耐久性极限状态。考虑一般大气环境功能函数ZⅠ语义的模糊性,基于部分碳化区长度建立功能函数ZⅠ的隶属函数。给出RI-METS理论在一般大气环境下混凝土结构耐久性中的应用算例。(4)为了在冻融环境下建立耐久性理论模型和试验与真实结构的相似关系,建立冻融环境下的RI-METS理论,给出冻融环境下各变量的相似率、相似准数公式以及相对信息熵计算公式。给出了冻融环境下的METS路径及相对信息熵计算公式。选择冻融疲劳损伤达到临界冻融疲劳损伤作为冻融环境下的耐久性极限状态。考虑冻融环境功能函数ZⅡ语义的模糊性,给出功能函数ZⅡ的隶属函数。给出RI-METS理论在冻融环境下混凝土结构耐久性中的应用算例。(5)为了在海洋氯化物环境下建立耐久性理论模型和试验与真实结构的相似关系,建立了海洋氯化物环境下的RI-METS理论,给出了海洋氯化物环境下各变量的相似率、相似准数公式以及相对信息熵计算公式。选择钢筋表面氯离子浓度达到临界氯离子浓度作为海洋氯化物环境下的耐久性极限状态。考虑海洋氯化物环境功能函数ZⅢ语义的模糊性,并给出功能函数ZⅢ的隶属函数。给出RI-METS理论在海洋氯化物环境下混凝土结构耐久性中的应用算例。更多还原

【Abstract】 Durability is the basic performance of concrete structures and an important part of structural reliability. How to determin and evaluate the service life of concrete structures is the important problem of concrete structures’durability. At present, the service-life assessment of concrete structures was made according to theoretical models and durability tests. But neither theoretical models nor durability tests could totally represent concrete structures in natural environment. The similar relationships between theoretical models, durability tests and true structures are the key to ensure reliable service-life evaluation. This thesis attemped to use information theory and information relativity in Multi-environmental time similarity theory (METS) to systematically research on the information incompleteness of both theoretical models and durability tests and authenticity of results, and finnally established the Multi-environmental time similarity theory based on relative information (RI-METS). Not only did RI-METS pefect the theoretical system of concrete structural durability’s assessment, but also enriched and developed the uncertainty analysis method of the reliability of engineering structures. The specific contents are as follows:(1) In order to use the information of theoretical models and durability tests in the concrete structures in nature environment, on the basis of METS theory, RI-METS theory was established. For extending the application range of METS theory, and solve the problem that METS theory couldn’t handle a variety of information sources and observation paths, the concept of METS path was proposed, which could be divided into 4 categories:METS(1;1) path, METS(i;1) path, METS(1;y) path and METS(i;y) path. In order to handle the information relativity of METS theory, relative information entropy was used to characterize the information relativity. Syntax information entropy and semantic information entropy were two dimensions of relative information entropy obtained by the observer, which could be characterized by Shannon information entropy and fuzzy entropy respectively. The hypobolic tangent of Minkowski observation angle was used to characterize the observer’s effect. All the Minkowski observation angles of METS paths were used for information integration. In order to make the observer could chose the best METS path and make decision, the utility degree function was used to evaluate the effectiveness of METS path.(2) The structure engineer could make durability design and service-life assessment according to exsisting codes in the absence of data or accelerated durability tests’data. In order to obtain comprehensive information of exsisting codes, Chinese, European and American (CEA) codes were summarized, and design code system was established and described from three aspects:the prescriptive design method, the avoiding deterioration method and the performance-reliability-based method. In order to unify the natural environments divided by each different code, a comparison table of 5 kinds 21 natural environment categories from CEA codes was established.(3) In order to build similar relationships between theoretical models, durability tests and true structures in general atmospheric environment, the RI-METS theory used in general atmospheric environment was established, and formulas for parameters’ similar ratio, similar criteria and relative information entropy were proposed. The state that concrete carbonation depth equals to the concrete cover was selected as the durability limit state in general atmospheric environment. The semantic fuzziness of performance function ZI was considered, and its membership function was proposed on the depth of partial carbonation zone. The application of RI-METS theory on concrete structural durability in general atmospheric environment was given.(4) In order to build similar relationships between theoretical models, durability tests and true structures in freezing-thawing environment, the RI-METS theory used in freezing-thawing environment was established, and formulas for parameters’similar ratio, similar criteria and relative information entropy were proposed. The state that freezing-thawing fatigue damage reaches to the critical freezing-thawing fatigue damage was selected as the durability limit state in freezing-thawing environment. The semantic fuzziness of performance function ZⅡ was considered, and its membership function was proposed. The application of RI-METS theory on concrete structural durability in freezing-thawing environment was given.(5) In order to build similar relationships between theoretical models, durability tests and true structures in marine environment, the RI-METS theory used in marine environment was established, and formulas for parameters’similar ratio, similar criteria and relative information entropy were proposed. The state that the chloride ion content reaches the critical chloride ion content was selected as the durability limit state in marine environment. The semantic fuzziness of performance function ZⅢ was considered, and its membership function was proposed. The application of RI-METS theory on concrete structural durability in marine environment was given.更多还原