【作者】 蒋梅玲；

【导师】 金贤玉；

【作者基本信息】 浙江大学 ， 结构工程， 2010， 硕士

【摘要】 混凝土是一种复杂的多相复合材料。由于各组成部分不同的物理特性、结合面、外荷载作用以及环境的多方面影响,其破坏机理异常复杂,导致对混凝土的断裂机理的研究非常困难。近年来,基于损伤力学和断裂力学的混凝土开裂研究越来越受到人们的重视和认可,并取得了不少成果。但是其研究仍然处于起步阶段,无论是理论、还是试验都很不成熟。于是本文就此开展了以下研究:(1)分析了损伤力学和断裂力学模型的优缺点,提出了一种基于宏观断裂力学并综合考虑细观损伤理论的混凝土断裂模型。该模型用细观损伤推导得到的混凝土本构模型来描述混凝土开裂前的应力应变关系,且能够考虑断裂扩展区对断裂的影响。它综合了目前各研究模型的优点,能得到解析解。(2)进行普通混凝土的断裂试验来验证该模型。选用三组初始缝高比分别为0.1、0.2、0.3的混凝土试件,考查它们在八个不同龄期的断裂性能,计算裂缝尖端开口位移和应力强度因子这两个参数,从初始缝高比和龄期这两个方面进行了分析。(3)对掺矿物外加剂的混凝土的断裂进行了试验研究。分别计算了单掺粉煤灰和掺矿粉的混凝土的断裂性能,分析了粉煤灰和矿粉的掺入对混凝土断裂性能的影响及其原因。(4)运用大型有限元分析软件ABAQUS的弥散开裂模型,对混凝土的三点弯曲梁开裂过程进行数值模拟分析。分析比较了不同龄期和不同初始缝高比时普通混凝土的开裂性能,并与试验结果进行了对比。更多还原

【Abstract】 Concrete is a kind of complex multi-phase composite material. Because of the different physical characteristics, cohesion surfaces of its various components, load conditions as well as the influence of environment, the failure mechanism of concrete is exceptionally complex, which makes the study of its fracture mechanism very difficult. In recent years, the researches on concrete cracking based on damage mechanics and fracture mechanics have draw more and more attentions and recognitions. However, the researches in this field are not mature enough although there are some achievements. Therefore, this paper carries out the relevant research as follows.Firstly, the advantages and disadvantages of damage constitutive models and fracture models of concrete are analyzed respectively. Then a improved consolidated concrete fracture model combining the damage model and fracture model is proposed in this paper.In this model, the meso-damage model is used to get the stress distribution of the fracture extension area and the impact of the fracture extension area on the fracture is considered. It combines the advantages of the two models above and can achieve the analytical solution.Secondly, the concrete fracture experiments are carried out to verify the new model above, using three concrete groups, whose initial seam height ratio of the concrete specimens are 0.1,0.2,0.3 respectively. The fracture behaviors of each group in eight different ages are reviewed. And the crack tip opening displacement and stress intensity factor are calculated using the theoretical model proposed in this paper.Then, the experiments on the fracture of concrete with mineral admixture are carried out. The fracture properties of the concrete mixed with fly ash and slag respectively are obtained and compared to the corresponding plain cement concrete. Then the influence of the fly ash and slag to the fracture properties of concrete are analyzed as well as their reasons.At last, the numerical simulation of the concrete cracking in the three-point bending beam is established with the finite element analysis software-ABAQUS. The finite element results and experimental results of the fracture properties of concrete with different ages and initial seam height ratios are compared.更多还原