Research On Static Damage Behavior Of Concrete Based On Micromechanical Model

Concrete is a versatile multi-phase composite material.It is important to study its damage behavior under the action of external load.In the past,most of the concrete was treated as a homogeneous material,and various mechanical properties were studied through experiments.The method was costly and the cycle was long.In this paper,the concrete is regarded as the multiphase composite composed of aggregate,mortar matrix and the interface transition zone between them.The concrete mesoscopic numerical model is established,and the damage behavior of concrete is studied on the mesoscopic level.The work done is as follows:(1)Combining the Fuller grading curve with the Walraven formula,the method of determining the amount of aggregate particles in the 3D concrete specimen is applied to the 2D concrete specimen,and the different grades of aggregate are compiled by matlab software.The launch generation program lays the foundation for the meso-modeling of concrete;(2)Based on the understanding of the cohesion model,the traction-separation curve of the bilinear cohesion model is introduced to describe the interface between the aggregate and mortar matrix and the interface between the mortar matrix and the mortar matrix on the mesoscopic level.The relationship between the structure and the relevant literature,the parameters in the constitutive model are determined,and the program for generating the cohesive force unit is compiled by matlab software and integrated into the finite element analysis software;(3)According to the prepared aggregate delivery procedure,different mesoscopic concrete meso-models were generated,and the cohesive force unit was inserted into the aggregate-mortar matrix interface and the mortar matrix-mortar matrix interface to study the aggregate volume content.And the influence of the size of the test piece on the tensile strength,the results show that as the aggregate volume content and the size of the test piece increase,the interface transition zone in the test piece also increases,resulting in a gradual decrease in tensile strength,indicating the tensile strength of the concrete.It is mainly determined by the interface transition zone.It also proves that it is feasible to analyze the meso-concrete material by using the cohesion model proposed in this paper;(4)According to the concrete mesoscopic modeling method given in this paper,the cross-scale calculation model of numerical analysis of curved beams is established.The stress and crack evolution of the two types of three-point bending beams are studied.The results show that When the initial crack is 0.25 times of the beam height,the stress concentration factor is k=0.97.The failure process of the four-point bending beam is studied.The bending strength of the concrete beam is calculated according to the ultimate bearing capacity obtained by numerical simulation.Compared with the existing experimental results,the difference is 4.65%.This shows that the concrete mesoscopic analysis method established in this paper can better reflect the mechanical properties of concrete and the damage process on the mesoscopic level.