混凝土断裂参数厚度尺寸效应及窄条断裂区模型改进研究

发布时间：2018-04-27 07:45

本文选题：混凝土 + 厚度尺寸效应　；参考：《浙江大学》2017年硕士论文

【摘要】：混凝土断裂力学是在普通断裂力学的基础上发展起来的、富有实用意义的力学学科。混凝土断裂力学参数的尺寸效应和断裂过程区的表征,是能否建立有效断裂准则从而实现工程应用的关键所在,是两个重要的理论问题。鉴于混凝土断裂参数厚度尺寸效应研究的不足,作为国际材料与结构试验室联合会(RILEM)TC265-TDK委员会为制定双K断裂参数国际通用规范而开展的国际联合试验的一部分,本文进行了 5组29根变厚度三点弯曲梁的断裂试验,测算了各试件的双K断裂韧度、断裂能GF等主要断裂参数,讨论了标准计算方法的合理性,并用归一化和趋势线方法定量表征了各参数的厚度尺寸效应。结果发现,混凝土双K断裂韧度、断裂能GF以及反映断裂过程区长度的临界有效裂缝长度ac、反映材料脆性的特征长度lch等均未表现出明显的厚度尺寸效应,以最小尺寸试件为标准,每增加1倍最小厚度,各参数的变化幅度均不超过5%。本文还从断裂韧度计算公式、Weibull尺寸效应统计理论和三维考察等方面分析了上述结果。出于简单解析和一般应用的考虑,本文结合混凝土断裂力学、特别是双K断裂模型的研究成果,在较早期的窄条断裂区模型的基础上,提出了表征微裂缝区的新模型。该近似模型,基本概念清晰、计算解析简单,关于黏聚韧度KIcσ和微裂缝区长度lF的理论预测也获得了前述断裂试验的验证,因而可以作为工程实际应用的备选。
[Abstract]:The fracture mechanics of concrete is developed on the basis of ordinary fracture mechanics and has practical significance. The size effect of fracture mechanics parameters of concrete and the characterization of fracture process zone are the key to establish effective fracture criterion and realize engineering application, which are two important theoretical problems. In view of the inadequacies in the study of thickness and size effect of fracture parameters of concrete, as part of the international joint tests carried out by the International Federation of Materials and structure Laboratories, RILEMN TC265-TDK Committee for the formulation of the International General Specification for double K fracture parameters, In this paper, the fracture tests of 29 three-point bending beams with variable thickness have been carried out. The main fracture parameters, such as double K fracture toughness and fracture energy GF, have been calculated, and the rationality of the standard calculation method has been discussed. The thickness and size effect of each parameter is quantitatively characterized by the method of normalization and trend line. The results show that the double K fracture toughness, fracture energy GF, critical effective crack length acand the characteristic length of material brittleness lch do not show significant thickness size effect. With the minimum size specimen as the standard, the variation range of each parameter is not more than 5 for every increase of the minimum thickness. The above results are also analyzed from the statistical theory of Weibull size effect and three dimensional investigation. For the sake of simple analysis and general application, based on the research results of concrete fracture mechanics, especially the double K fracture model, and on the basis of the earlier narrow strip fracture zone model, a new model for characterizing the microfracture zone is proposed in this paper. The basic concept of the approximate model is clear and the calculation is simple. The theoretical prediction of the cohesion toughness KIc 蟽 and the length of the micro-fracture zone L _ F has also been verified by the fracture test mentioned above, so it can be used as an alternative for practical engineering application.
【学位授予单位】：浙江大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TU528

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