基于细观力学方法的混凝土多尺度损伤力学行为研究

发布时间：2018-01-14 20:12

本文关键词：基于细观力学方法的混凝土多尺度损伤力学行为研究　出处：《大连理工大学》2015年硕士论文　论文类型：学位论文

【摘要】：目前混凝土结构是世界上应用最广泛的建筑结构之一,其中混凝土是重要的建筑材料,混凝土结构的破坏实际上是混凝土材料损伤积累的结果。混凝土是由水、水泥、粗细骨料、孔隙及裂纹等组成的复合材料,混凝土在使用时随着外界荷载的增大或者环境温度的变化,其内部大量存在的微裂纹和微孔洞逐渐延伸、扩展直至贯通,使得混凝土材料损伤不断积累,承载力逐渐降低直至完全丧失,进而结构主体丧失承载力,引起混凝土结构的破坏,严重威胁到人身安全和财产安全。基于混凝土的力学性质,本文主要研究混凝土材料细观到宏观损伤力学行为。在细观层次上混凝土视为是由粗骨料、水泥砂浆及两者之间的界面过渡区组成的三相非匀质复合材料,首先对混凝土静态力学性能进行研究,采用Mori-Tanaka细观力学理论分析方法,建立三相介质力学特性与混凝土等效弹性模量之间的数值关系,分析细观各因素对混凝土等效力学特性的影响。在砂浆和界面过渡区中引入大量随机分布的微孔隙,研究微缺陷对混凝土等效弹性模量的影响,定义混凝土的初始损伤,着眼于细观尺度上微裂纹萌生、延伸及贯通等整个损伤过程的物理形态演化,建立孔隙率与混凝土损伤变量的数值关系。在混凝土等效弹性模量的时变特性的研究下,进一步探讨三相介质和混凝土等效损伤模型的建立。混凝土承载的应力应变并非三相介质承载的应力应变简单加和,对Mori-Tanaka理论公式推导,建立三相介质应力应变场间,及和混凝土应力应变场的数值关系,并对本文提出的方法与Voigt并联模型进行算例对比分析,以三相介质的简单损伤本构模型建立混凝土复杂的损伤本构模型,研究混凝土多尺度损伤力学行为。
[Abstract]:At present, concrete structure is one of the most widely used building structures in the world, in which concrete is an important building material, the damage of concrete structure is actually the result of concrete material damage accumulation. Cement, coarse aggregate, pore and crack composite materials, concrete in use with the increase of external load or environmental temperature changes, a large number of internal microcracks and micropores gradually extend. The damage of concrete material is accumulated and the bearing capacity is gradually reduced until it is completely lost, and then the main body of the structure loses its bearing capacity, which causes the destruction of concrete structure. Based on the mechanical properties of concrete, this paper mainly studies the macroscopic damage mechanical behavior of concrete materials. In the meso level, concrete is regarded as coarse aggregate. In this paper, the static mechanical properties of cement mortar and its interfacial transition zone are studied, and the Mori-Tanaka method is used to analyze the static mechanical properties of concrete. The numerical relationship between the mechanical properties of three-phase medium and the equivalent elastic modulus of concrete is established. The influence of various factors on the equivalent mechanical properties of concrete is analyzed. A large number of randomly distributed micropores are introduced into the mortar and interfacial transition zone to study the effect of microdefects on the equivalent elastic modulus of concrete. The initial damage of concrete is defined, focusing on the physical morphology evolution of the whole damage process, such as the initiation, extension and penetration of microcracks on a meso-scale. The numerical relationship between porosity and concrete damage variables is established, and the time-varying characteristics of the equivalent elastic modulus of concrete are studied. This paper further discusses the establishment of equivalent damage model of three-phase medium and concrete. The stress-strain of concrete is not the simple sum of stress and strain of three-phase medium. The theoretical formula of Mori-Tanaka is deduced. The numerical relationship between the stress and strain fields of three-phase medium and concrete is established, and the method proposed in this paper is compared with the Voigt parallel model. Based on the simple damage constitutive model of three-phase medium, the complex damage constitutive model of concrete is established, and the multi-scale damage mechanics behavior of concrete is studied.
【学位授予单位】：大连理工大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TU528

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