Multi-environmental Time Similarity Theory Based On Relative Information And Its Application In Concrete Durability

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.