【作者】 李勇；

【导师】 金贤玉； 郑建军；

【作者基本信息】 浙江大学 ， 结构工程， 2004， 硕士

【摘要】 随着混凝土结构的发展，兴建的重大结构工程日渐增多。这些结构的安全和正常运行，已经不仅是一个单纯的技术、经济问题，而是对人民生命财产和社会安定有重大影响的社会问题。而且，这些结构往往是形体高大而复杂，承受的荷载大且变化多，还可能经受各种严酷的环境作用和偶然性事故。因而，这些结构的力学分析和设计要求有足够的精确度和可靠性，而理论上和方法上又有较大的技术难度。 另一方面看，混凝土因其材料组成和构造的原因而具有非匀质、非线性和各向异性等性质，还因混凝土内部微裂缝的存在和发展，力学性能随时间和环境条件而变异，使得混凝土的强度和变形状态十分复杂，影响因素多，变化幅度大，性能指标的离散度也大。 过去，一般的钢筋混凝土结构尺寸较小，形状简单，受力明确，都可采用足尺的或按比例缩小的模型，在实验室内进行荷载试验，测定其结构反应，将试验结果直接用于设计，或者经过统计分析后，用得到的经验公式知道设计。但是，对于前述形体和受力都很复杂的重大结构物，这些经验性方法显然无法胜任。断裂力学用于混凝土研究，大大推动了混凝土断裂力学和强度理论的发展，但是不论是线弹性断裂力学还是弹塑性断裂力学，应用于混凝土材料都有其各自的局限性。 本文回顾了经典的混凝土强度准则，分析讨论了各种强度理论的优缺点，提出了进一步研究的必要性；分析讨论了断裂力学发展的几个重要阶段，以及断裂力学在混凝土中的应用；在比较分析Bazant尺寸效应律的两套不同公式的基础上，指出了用能量的方法考虑尺寸效应的优势；在考虑边界效应基础上，建立了新的局部断裂能分布模型，并由此推导出反映尺寸效应的断裂能分布公式。更多还原

【Abstract】 With the development of concrete structure, more and more important buildings were constructed. The secure and normal operation is not a mere problem of technique or economic but one having great impact on welfare of the people and stability of the .society. However, these structures were usually high and complicated, endured big and variational load, and encountered abominable environment and accident. The mechanic analysis and design of the structures required enough precision and reliability, but it is very difficult theoretically and practically.In addition, concrete is uneven, unlinear and anisotropic because of its complicated composition. The existence and development of pre-crack , the variety of the mechanic performance and environment result in the complicated strength and strain. So that, the performance parameters are discrete, variational and influenced by many factors.In the past, reinforced concrete structures were usually small and simple so that we could make the experiments with the real size or small-scale model to get the mechanic performance of the structures. And the test results could be directly applied to the structure design and analysis. But this method could not be applied to the huge and complicated structures. The application of fracture mechanics to concrete research greatly promoted the development of concrete fracture mechanics and strength theory. However, not only linear elasticity but also elasticity-plasticity fracture mechanics had each limitation when they were applied to concrete research.This paper reviewed classic concrete strength criterions, discussed the merit and defect of every above-mentioned criterion and brought the necessity of extended research. In succession, this paper discussed the important phases of fracture mechanics, as well as the application of fracture mechanics to concrete. Based on thecompare and analysis of two kind of Bazant size effect, the predominance of energy method was pointed out. In the end, on the basis of considering the boundary effect, a new local fracture energy distribution model and the corresponding formulation were established.更多还原