Studies On Meso-Level Damage And Macroscopical Strength Of Concrete By Random Particle Model

The concrete si a kind of building material which is widely used in engineering. Studies for the mechanical properties of concrete are very important to increase the strength of concrete material, improve design level and reduce the construction cost. Some tests of concrete used to be done by researchers using some different equipments and test methods. In recent years, the tradition test methods and design approaches have been confronted with the challenges of the appearance of high speed and large capacity computers and the development of finite element method. Scientific researchers carried on a lot of numerical experiments by different test models and different calculating methods. Numerical experiments are easy to overcome the limitation in laboratory tests and explain the various phenomena happened in the experiments, and they can provide some very useful numerical analysis data to improve experiments. The research work is one of the important development trends in the areas of meso-level mechanics research currently, the study in the meso-level mechanics has already built a bridge between the meso-level structure and the macroscopic mechanics properties. In this paper, the random particle model and double lines damage model are used, and uniaxial mechanical properties of concrete and the damage mechanism are integrated on meso-level. The influences of size effect and parameter of materials are researched. The inner structure of concrete specimens is analyzed in meso-level and it is taken as composite structure of aggregates, matrix and the interfacial transition zone(the zone between aggregate and matrix). Using Walraven function and Monte-Carlo method ,the positions and number of aggregates are identified in plane, hence the random aggregate structures are generated. Then they are separated into the finite elements mesh. After the different material properties are assigned to respective elements according to the locations of elements in individual phases, a two-dimensional numerical model for the composite structure of concrete is formed. The numerical experiment can be carried out using a finite element method program. The program has the ability to carry on the automatic distribution to the strength parameter of materials by projection method. The classification loading principle is first time used by counting the number of damaged elements, residual strength elements and the latest broken elements using double lines damage model in the research. The program also can fill the different elements with deferent color in deferent step, and show these damaged elements and broken elements on screen. The results of the numerical test and laboratory test are compared. The following works have been finished in this paper. (1) The general characteristic of the concrete and the necessity on meso-level study of the concrete were reviewed. (2) The meso-level damage, broken theory and the regularities of deformation and destruction for concrete were studied.