Meso-scale Simulation Analysis Of Uniaxial Mechanical Behavior Of Concrete

Concrete is currently the largest building material and is widely used in various industrial and civil buildings,such as super high-rise buildings,sea-crossing bridges and nuclear power plants.Due to the random distribution of the phase composition of the material on the microscopic scale,the concrete material has non-uniformity,and the macroscopic level exhibits nonlinear mechanical behavior.Based on the view of multi-scale analysis,the macroscopic mechanical properties of concrete can be explained and verified from the structural features on the mesoscale.In order to better carry out structural analysis and design evaluation of concrete structures,this paper systematically studies the meso-mechanical properties of concrete,and uses the simulation method of meso-finite element method to explore the distribution of material composition of concrete phase in meso-structure.The relationship between the macroscopic mechanical responses reveals the mechanism of failure and ultimately establishes the corresponding relationship between the meso-structure and macroscopic properties of concrete.Firstly,based on the Monte Carlo method,this paper generates the structure of random aggregate of concrete,transforms the randomness of meso-structure into mathematical random variables,and makes it conform to the uniform distribution,and establishes a reasonable and simplified concrete meso-structure.Based on the ideal Fuller grading curve and the Walraven formula,the particle number of each particle size aggregate is obtained.The characteristic parameters of random aggregate are automatically generated by MATLAB programming language,and the finite element model is established by using ABAQUS.The numerical solution is carried out,and the numerical results are compared with the experimental results to show the validity of the numerical simulation.Secondly,based on the mesoscopic finite element model of concrete,the macroscopic mechanical response of 2-D model under uniaxial static tensile and compressive loads is simulated.Through the parameter analysis,the multi-phase characteristics of concrete,such as coarse aggregate,are studied.Shape,random distribution,volume fraction,interface mechanical properties and pores,the influence of macroscopic stress-strain relationship and failure mode,the failure mechanism of concrete is studied,and the relationship between macroscopic mechanical behavior and meso-structure of concrete is obtained in a certain sense.The 3-D modeling and analysis of the concrete showed that the compressive strength of the model is higher than that of the model because of the constraint effect outside the plane,and the tensile strength due to localized characteristics of tensile failure are close to the 2-D model.Finally,this paper simulates the macroscopic mechanical response of the 2-D model under dynamic compressive loading.The numerical results show that the concrete exhibits a significant strain rate effect,and the compressive strength increases with the increase of the strain rate,and the failure mode also changes.Through the parameter analysis,the multi-phase characteristics of concrete,such as the sensitivity of mortar phase and interface phase,the shape and content of coarse aggregate,and the mechanical properties of interface,are studied for the dynamic mechanical response of concrete under different strain rates.The results show that the inhomogeneity of meso-structure has a significant influence on the dynamic mechanical behavior of concrete,and the sensitivity of mortar phase ratio plays a leading role in the improvement of specimen strength.The dynamic compressive strength increases with the increase of coarse aggregate content and interfacial mechanical properties.The 3-D model of the concrete results in DIF that is always higher than the 2-D numerical result because of the out-of-plane constraint mechanism.