【作者】 金立兵；

【导师】 金伟良；

【作者基本信息】 浙江大学 ， 结构工程， 2008， 博士

【摘要】 混凝土结构耐久性问题是当今工程界所普遍关注的问题,它不仅关系到混凝土结构维护与再建成本的控制,而且与节能减排、环境保护和社会的可持续发展息息相关。本文对多重环境时间相似理论(Multi-Environmental Time Similaritytheory,METS)及其在沿海混凝土结构耐久性中的应用进行了研究。多重环境时间相似理论通过引入与研究对象具有相似环境条件且具有一定服役年限的第三方参照物,可以解决室内试验环境与现场实际环境之间的相似性问题,为通过室内试验对现场实际结构进行耐久性寿命预测和评估奠定了理论基础。文中详细分析了METS方法在沿海混凝土结构耐久性中的应用,为混凝土结构耐久性环境层次的研究迈出了关键的一步。具体研究内容如下:1.以经典的相似理论为基础,通过引入与研究对象服役环境相同或相似的参照物作为联系现场试验与室内加速模拟试验的桥梁,提出了多重环境时间相似理论。METS理论根据室内加速模拟试验和现场检测试验的结果,建立室内加速模拟环境与现场实际环境之间的时间相似关系,从而利用室内加速试验实现对现场实际结构进行有效、准确的预测与评估。通过对沿海混凝土结构耐久性的主要影响因素的分析,对METS方法在沿海混凝土结构耐久性寿命预测与评估的实现过程进行了研究。2.进行了混凝土结构耐久性试验METS方法的试验设计研究。对METS方法中第三方参照物的现场检测试验、研究对象的现场暴露试验、二者对应混凝土试件的室内人工气候模拟加速试验方法进行了研究。为METS方法在实际工程中的应用奠定基础。3.通过现场实测与室内加速试验均发现不同环境分区氯离子在混凝土侵蚀程度不同,并呈现潮差区最严重,浪溅区次之,大气区在不同深度的氯离子含量和侵蚀深度均比干湿交替区域低很多,说明室内人工加速模拟的试验环境与现场实际环境具有一定的相似性。4.研究了混凝土的氯离子扩散系数随表面氯离子浓度随时间的变化规律。根据室内加速试验结果,建立了不同环境分区(水下区、干湿交替区、大气区)混凝土时间衰减系数n与混凝土材料组成之间的关系式,该关系式表达形式简单,使用方便,与试验结果吻合较好。根据本文建立的时间衰减系数关系式,对室内加速和现场实际环境氯离子扩散系数的相似性进行了研究,得出不同环境分区氯离子扩散系数的相似率。利用Boltzmann变量,拟合得到在对流区深度处的氯离子浓度,并以此作为氯离子扩散的起点,建立了室内加速环境与现场实际环境中表面氯离子浓度随时间的累积关系,得出不同环境分区表面氯离子浓度基于室内环境与现场环境的相似率。5.基于METS方法,利用氯离子扩散系数和表面氯离子浓度的相似率和室内加速试验的结果,以距混凝土表面深度60mm处的水溶性氯离子含量0.05%(相对混凝土质量的百分比)为参照对象,考虑氯离子扩散系数和表面氯离子浓度的时变效应,通过数值模拟的方法得到了室内加速环境在不同环境分区相对现场实际环境的时间相似率。6.基于混凝土结构耐久性试验的METS方法,对杭州湾跨海大桥实际工程混凝土结构耐久性进行了寿命预测。根据METS方法,利用现场检测试验、室内加速试验、现场暴露试验的检测结果建立了不同环境之间氯离子扩散的相似关系,用数值模拟方法分析了氯离子对杭州湾跨海大桥混凝土结构主要构件的侵蚀过程并进行了寿命预测,预测过程中考虑了氯离子扩散系数与表面氯离子浓度的时变性,更加接近混凝土的实际退化机理,预测结果合理、可信、有说服力。更多还原

【Abstract】 The durability of reinforced concrete (RC) structures has attracted extraordinary concern in the field of civil engineering. Besides the cost of rebuilding and maintenance, it is also closely related to energy-saving, emission reduction, environmental protection and sustainable development of the society. A multi-environmental time similarity (METS) theory and its application in coastal concrete structural durability are presented in this paper. METS can be used for durability assessment and life prediction by introducing a third reference site with a certain service life and the same or similar aggressive environment to the study object to bridge the field inspections and the indoor accelerated tests. The correlation between the field inspection data and the results of indoor tests in accelerated environments is established based on METS. Furthermore, the results of indoor tests are used to predict service life of RC structures effectively. The application of METS in coastal concrete structural durability is analyzed in detail, and it makes a meaningful step towards the durability research of concrete structures in environment-level.The details are as follows:1. Based on the classical similarity theorys, a reference site with almost the same or similar aggressive environment is introduced to bridge the field inspections and the indoor accelerated tests, and the METS theory is presented. Once the correlation between the field inspection data and the results of indoor tests in accelerated environments is established, the life assessment of existing RC structures will be performed effectively. By analyzing the major influence factors of coastal concrete structural durability, the implementation process of life prediction and durability assessment for the coastal concrete structures is analyzed.2. The experimental design of METS is also included. Three tests, including field inspection test on the third reference site, the field exposure test, and the indoor test by artificial climate simulation on the concrete specimens from the third site and the investigated object are designed to lay the foundation for the application of METS.3. According to both the field inspection data and the indoor accelerated test results, it can be found that the chloride penetration varies with environmental zones. Tidal zone ranks the most serious one, followed by splash zone, and the chloride content in different depths from the concrete surface of the atmospheric zone is much lower than that of the wetting-drying cycling zone. It indicates that the indoor accelerated and the site actual environments have a certain similarity.4. The time-dependent rules of chloride diffusion coefficient and surface chloride concentration are studied. According to the indoor accelerated experimental results, the formula between the age exponent and concrete composition is established in different environmental zones, such as submerged, wetting-drying cycling and atmospheric zone. This expression is simple, easy to apply, and agreeable well with the test results. Then, the similarity of chloride diffusion coefficients between the indoor and outdoor actual environments is studied to obtain the similarity rates of diffusion coefficient in different environmental zones. By introducing Bltzmann variable, the chloride concentration at the maximum convective depth is obtained as the surface chloride concentration of pure diffusion zone by regression analysis. The accumulation rate relation of surface chloride concentration in indoor and on-site environments with time is established, and the similarity rates of surface chloride concentration in different environmental zones are established.5. Based on METS, the time similarity rates of chloride penetration between the indoor accelerated environment and field condition of different environmental zones are achieved by numerical simulation according to the indoor test results and the similarity relations of both diffusion coefficient and surface chloride concentration. chloride ingress time can be obtained where the chloride content at the depth of 60mm from the concrete surface reaches to 0.05% (by weight of concrete). The time-dependent diffusion coefficient and surface chloride concentration is taken into account in numerical analysis.6. Based on METS, the life prediction of concrete structures of Hangzhou Bay Bridge (HZBB) is carried out. The chloride ingress process of main components and life prediction are accomplished by numerical simulation based on the similarity relations of chloride diffusion results from analyzing the results of on-site inspection, indoor accelerated test and field exposure test. In order to match the actual deterioration process of concrete, and obtain reasonable, creditable and convictive prediction results, the time dependence of diffusion coefficient and surface chloride concentration is taken into account.This research was supported by the project of National Natural Science Fund "Fundamental Research on Durability Design and Assessment of Concrete Structures in Chloride Erosive Environment" (50538070), "863 program of National Hi-Tech Research Development "Durability Test Method and Assessment Technology of Important Coastal bridges" (2006AA04Z422), National Major Project Program "Concrete structural durability research on Hangzhou Bay Bridge". Their support is gratefully acknowledged.更多还原