基于分形理论的混凝土动力拉伸过程定量研究  

Fractal theory-based quantitative study on dynamic tensile process of concrete

作　　者：黄少雄 HUANG Shaoxiong(Renxin Management Office of Renbo Expressway Management Center, Shaoguan 512600, Guangdong, China)

机构地区：[1]广东省仁博高速管理中心仁新管理处,广东韶关512600

出　　处：《水利水电技术》2020年第8期201-208,共8页Water Resources and Hydropower Engineering

基　　金：国家自然科学基金项目(51679199,51979225)。

摘　　要：为了从细观层面上定量研究混凝土动荷载作用下的破坏过程,以正弦波动力荷载作用下的混凝土CT试验为基础,编制了基于差分盒维数理论的分形维数计算程序,分别研究了混凝土试样三个断面大统计区域和感兴趣区域上的分形维数随加载过程的变化过程,通过分析混凝土试样在加载过程中分维数的变化规律,探讨了分维数变化与损伤裂纹演化过程的关系。结果表明:正弦波动力拉伸荷载作用时混凝土试样中一般有多条裂纹同时萌生,但当主裂纹形成后,次生裂纹会闭合,主裂纹会抑制次裂纹的发展,且裂纹大致与拉荷载方向垂直,破坏形式属于脆性断裂,损伤裂纹表面平整,裂纹沿材料强度较弱的区域发展;混凝土试样各断面分形特征明显,分形维数能较好地描述混凝土损伤裂纹的演化规律,可作为研究混凝土裂纹演化的定量参数;感兴趣区域分维数的变化更明显,更有利于描述混凝土受力破坏时内部的应力集中、应变局部化和损伤裂纹的演化规律。In order to quantitatively study the failure process of concrete under dynamic load on mesoscopic level,a differential box counting theory-based fractal dimension calculation program is compiled on the basis of the concrete CT test under the effect of sine-wave dynamic load,and then the changing processes of the fractal dimensions in the large statistic area and interested area of three sections of the concrete specimen along with the loading process are respectively studied.The changing law of the fractal dimension of the concrete specimen is analyzed,while the relationship between the change of the fractal dimension and the evolution process of the damaging crack is discussed as well.The study results show that several cracks are generally there to be simultaneously initiated in the concrete specimen under the effect of the sine-wave dynamic tensile load,but the secondary cracks are to be closed when the principal crack is formed.The principal crack can restrict the propagation of the secondary crack,while the crack is generally perpendicular to the direction of the tensile load with the failure mode of brittle fracture and a smooth surface of damaging crack;moreover,the crack develops along the area with weaker material strength.The fractal characteristics of all the sections of the concrete specimen are obvious,and then the fractal dimension can better describe the evolution law of the damaging crack of concrete,which can be taken as the quantitative parameter for studying the concrete crack evolution.The change of the fractal dimensions in the interested area are more obvious,thus are more favorable to the description of the internal stress concentration,the strain localization and the evolution law of the damaging crack.

关 键 词：混凝土 CT试验 差分盒维数 损伤演化规律 

分 类 号：TV501[水利工程—水利水电工程]