Meso-damage And Fracture Studies Of Concrete Based On Equivalent Method

Concrete is a typical heterogeneous composite material,which is widely used in the field of civil engineering,and the material properties are closely related to the durability and safety of concrete structures.The mechanical properties of the materials in the concrete are very different,and the variation of the basic properties of concrete will be further studied because of the existence of micro cracks,pores and other defects.As an important method to study the mechanism of concrete deterioration,numerical analysis can simulate and predict the mechanical properties of concrete with the experimental data and theoretical research,and it have become oneof the hot spotsin the study of concrete properties.Concrete can be seen as the compound material in the mesoscopic level,which is composedof coarse/fine aggregate,cement paste,various initial defects,and so on.The numerical model of concrete based on meso structure can directly reflect the influence of each phase composition of concreteon its performance and the whole damage and fracture process under the continuous fluctuating load,as well ascan avoid the influence of objective factors such as environmental factors and human errors on the test results.In this paper,the meso concrete random aggregate model based on damage mechanics is applied to the numerical analysis,the damage and failure process of concrete specimens under uniaxial load were simulated.Then the concept of equivalent method is introduced to the establishment of the numerical model,the rationality of the equivalent method in the meso-damage model of concrete is verified by the comparison of the simulation results before and after the equivalent.The specific work is as follows:1.The basic concepts of equivalent method and concrete damage and fracture mechanics are expounded,and the specific application of equivalent method in micro-mechanical analysis of concrete is studied.2.In the numerical software,Monte Carlo method is used to realize the random distribution of the round aggregate particles in the designated area and the aggregate grading range by programming language.Then,the generated aggregate coordinate data is processed,and the interface unit is added to generate the geometric model of the two-dimensional concrete specimen.3.In this paper,the damage model is introduced into the numerical simulation of uniaxial tension and uniaxial compression of concrete specimens after the two development of finite element software.By setting the state variables to determine whether the unit is removed or not,and then simulate the expansion of internal cracks in concrete,then get the corresponding stress-strain curve.4.The equivalent method is applied to numerical models,namely the mortar matrix and interfacialtransition zone is equivalent to a material,by comparing the test with the original three-phase material model results to verify the reliability of the method,and create the damage variable output module in the subroutine to directly reflect the damage and fracture process of the equivalent post model.5.The influence of interface thickness,aggregate gradation and porosity on the performance of concrete is discussedIn this paper,the equivalent method is used to simplify the modeling process,and the damage variable output module is developed.At the same time,the calculation efficiency of the model can be improved and the damage and fracture process of concrete under uniaxial load can be expressed more truly and intuitively.This research provides technical support for the microscopic analysis of the basic properties of concrete,laying a theoretical foundation for structural analysis and optimization design of concrete structures.