骨料分布对混凝土力学行为影响的研究

发布时间：2018-02-25 06:31

本文关键词： 细观组元数值模拟钻孔加载法有限元分析骨料分布　出处：《沈阳建筑大学》2013年硕士论文　论文类型：学位论文

【摘要】：近年来，混凝土力学性能的研究从宏观层次发展到了细观层次。在细观层次上认为混凝土是由干砂浆、石粒和粘结层构成的非均质材料，其内部结构极为复杂。随着计算机技术和有限元数值模拟分析方法不断发展，学者们对混凝土细观结构的研究也越来越深入，建立了多种数值模型。混凝土细观组元对宏观性能的影响成为了混凝土技术领域研究的方向之一。本文主要的研究工作如下。（1）混凝土材料细观组元的力学性能是真实模拟混凝土力学行为的重要力学参数。当前对混凝土材料细观组元的力学性能的测量方法还不够完善，为了解决非规则小块石材的抗拉性能的测定，本论文提出了钻孔加载法。基于静力平衡理论分析危险截面上拉伸应力的分布规律，建立钻孔加载法的力学模型。在考虑特征破坏尺寸和圆孔大小对孔边应力集中的影响规律的基础上建立测量脆性材料拉伸强度的理论公式。实测了钻孔小块青石的破坏载荷，，将破坏载荷代入脆性材料拉伸强度理论公式得到石材的拉伸强度。同时测量了无孔长条试件拉伸强度，来验证钻孔加载法的可行性。（2）建立理想化的混凝土模型。对混凝土模型内典型的面、线上的应力和应变分布做了系统的分析，得到了一些有意义的结果。发现当两种材料共同承受载荷时，弹性模量大的材料分配的应力大，有点“能者多劳”的意思；受强骨料的影响，两种材料连接区域的应力也比较大，石块和水泥砂浆的粘结部位为混凝土的薄弱部位。在本文中将混凝土假设为砂浆和石块两相材料组成，也得出砂浆和石块的粘结部位为混凝土的薄弱环节，最容易破坏，所以砂浆和石块之间的初始裂缝是使此区域容易破坏的原因之一，而不是唯一的因素。（3）为了研究弹性模量对混凝土宏观力学性能的影响，设定了三种砂浆和石块弹性模量比，对模型的典型面、线进行应力分布分析，当砂浆和石块的弹性模量比r增大时，砂浆区域的承载能力变大，石块和砂浆承受的应力的差距逐渐减少，整个结构的应力分布也越来越均匀，结构中局部应力集中的现象也将越来越不明显，混凝土的承载能力也将会大幅增加。所以增加混凝土中砂浆的强度是提高混凝土承载能力的有效方法。（4）最后研究石块分布对混凝土宏观力学行为的影响。三种骨料分布，三个数值模型，不管是线、面还是体上三个模型的应力、位移分布均不同，可见混凝土材料的骨料分布情况对混凝土力学行为有一定的影响。混凝土细观结构的变化，对材料宏观力学行为产生了影响。
[Abstract]:In recent years, the study of mechanical properties of concrete has developed from macroscopic level to mesoscopic level. At the meso level, concrete is considered to be a heterogeneous material composed of dry mortar, stone particles and adhesive layer. With the development of computer technology and finite element numerical simulation analysis method, the research of concrete mesoscopic structure is becoming more and more in-depth. Various numerical models have been established. The influence of concrete meso-components on macroscopic properties has become one of the research directions in the field of concrete technology. The main research work in this paper is as follows. 1) the mechanical properties of meso-components of concrete materials are important mechanical parameters to simulate the mechanical behavior of concrete. The current measurement methods of mechanical properties of meso-components of concrete materials are not perfect enough. In order to determine the tensile properties of irregular stones, a borehole loading method is proposed in this paper. Based on the static equilibrium theory, the distribution of tensile stress on dangerous sections is analyzed. The mechanical model of the borehole loading method is established. The theoretical formula for measuring the tensile strength of brittle materials is established on the basis of considering the influence of the characteristic failure size and the circular hole size on the stress concentration at the hole edge. The failure load of the borehole small bluestone is measured. The tensile strength of stone is obtained by inserting the failure load into the theoretical formula of tensile strength of brittle material and the tensile strength of the specimen without holes is measured to verify the feasibility of the borehole loading method. The distribution of stress and strain on the typical surface and line in the concrete model is systematically analyzed, and some meaningful results are obtained. It is found that when the two kinds of materials are subjected to the load together, Materials with high elastic modulus have a large distribution of stress, meaning that "the more the fittest are"; the stress in the connecting region of the two materials is also relatively large under the influence of strong aggregates. The bond part of stone and cement mortar is the weak part of concrete. In this paper, the concrete is assumed to be composed of mortar and stone, and it is also found that the bond part of mortar and stone is the weak link of concrete, which is the easiest to destroy. So the initial crack between the mortar and the rock is one of the factors, not the only one, that makes the area vulnerable. In order to study the influence of elastic modulus on the macroscopic mechanical properties of concrete, three kinds of elastic modulus ratio of mortar and stone are set up. The stress distribution of typical surface and line of the model is analyzed. When the elastic modulus ratio r of mortar and stone increases, The bearing capacity of mortar area becomes larger, the difference between the stress of stone and mortar decreases gradually, the stress distribution of the whole structure becomes more and more uniform, and the phenomenon of local stress concentration in the structure becomes less and less obvious. Therefore, increasing the strength of mortar in concrete is an effective way to improve the bearing capacity of concrete. Finally, the influence of rock distribution on the macroscopic mechanical behavior of concrete is studied. The stress and displacement distributions of three numerical models, whether line, plane or body, are different. It can be seen that the aggregate distribution of concrete material has a certain influence on the mechanical behavior of concrete, and the change of concrete meso-structure has an effect on the macroscopic mechanical behavior of the material.
【学位授予单位】：沈阳建筑大学
【学位级别】：硕士
【学位授予年份】：2013
【分类号】：TU528.0

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