Damage Constitutive Model For Concrete And Finite Element Mesh-size Dependence

Concrete as a quasi-brittle material,can analyze its nonlinear mechanical behavior based on damage theory.This paper proposes a concrete damage eonstitutive model,which can reasonably define the damage evolution equation and accurately describe the mechanical behavior of concrete under biaxial strength.The problem caused by mesh-size dependence.Under the framework of thermodynamics,the damage loading surface under strain space is constructed to describe the damage of concrete under biaxial strength.The evolution equation of tensile damage is established by exponential evolution law,the classical experimental results of concrete are analyzed to establish the compression damage evolution equation.The crack band theory regularizes the damage threshold and solves the problem of mesh-size dependence.The four classical damage models of Mazars,Pegon,Oliver and de Vree are reviewed and perform numerical calculations.The applicability and limitations of classical damage models are verified compared with the Kupfer's experimental results.At the same time,the proposed model is used to numerically calculation.Compared with the experimental results and the classical damage model,the rationality and effectiveness of the proposed model under uniaxial and biaxial loading are verified.When using the finite element method to analyze the nonlinear mechanical behavior of concrete,it is especially important to establish a model for simulating concrete cracks.This paper introduces two main concrete crack models,discrete crack model and smeared crack model,and uses post-peak stress-strain relationship to specify tensile stiffening.To verify the rationality of the smeared crack model.When damage constitutive model is numerical analysis,there will be a problem of mesh-size dependence.This paper analyzes several typical methods for solving mesh dependence by using regularization.The model is demonstrated by the numerical calculation of the four-point bending non-proportional loading concrete test,and the calculation results of the proposed model and the traditional model under different dense finite element meshes are compared.It is verified that the proposed model can largely eliminate the mesh-size dependence,has engineering significance and practical application.Figure 71 table 4 references 85.