A Study Of The Meso-mechanical Model For Concrete Based On Random Aggregate

In this paper,concrete is regarded as a three-phase heterogeneous composite material consisting of cement mortar,aggregate and transition interface layer between them.Based on the self-programming program of MATLAB,two-dimensional and three-dimensional random aggregate generation and placement algorithms are developed.The finite element analysis software is used to study the mechanical properties of concrete.Through a large number of numerical simulation experiments,the influence of random distribution of aggregate,particle size,strength and other factors on the elastic modulus of concrete and the damage and damage characteristics of concrete meso-structure are analyzed.The main work of this paper is as follows:1.Using the programming language of matlab,this paper optimizes the technical difficulties in the process of random aggregate modeling in the current research,uses the search algorithm to judge the interference between ellipse,polygon and ellipsoid aggregate,improves the criteria for judging the intrusion between convex polyhedrons,optimizes the algorithm of random aggregate generation,improves the rate of concrete random aggregate delivery,and based on matlab.The software realizes the visualization of random model generation process.2.In view of the complexity of the mesh of the three-dimensional model,HyperMesh is used to optimize the mesh generation of the three-dimensional random aggregate model,and the mesh element model with better quality is obtained,which provides a high-quality model for numerical calculation.3.According to “Specification for mix design of ordinary Concrete” JGJ55-2011,different sizes of C30 concrete blocks and cement paste cube blocks were prepared,and a series of axial compression failure tests were carried out to obtain the ultimate compressive bearing capacity,and material parameters such as elastic modulus were calculated to provide experimental comparative data for numerical calculation model.4.The effective elastic modulus calculation method is used to predict the elastic modulus of concrete numerically,and the elastic modulus parameters of the interface layer are estimated.Compared with the experimental results,the validity of the meso-finite element model is verified.On this basis,the effects of the elastic modulus,aggregate volume ratio,maximum aggregate size,aggregate gradation,aggregate shape,interface thickness and porosity of concrete components on the elastic modulus of concrete are studied.5.Based on the constitutive relation of elastic damage,a damage evolution model of concrete with double broken lines is established to describe the degradation of stiffness damage of concrete materials in meso-scale.The damage degree of concrete specimens during progressive loading is reflected by the reduction of elastic modulus.The whole process of crack initiation,propagation,penetration and final failure of concrete materials is studied and analyzed.The research results can provide reference for the optimization of mechanical properties of concrete.