Simulation Of Concrete Failure Process With Considering Heterogeneous Material Property

In this thesis, concrete is taken as three-phase composites consisting of aggregate, mortar and bond between aggregate and mortar based on meso-mechanics. A concrete aggregate model is established, including ellipsoid and sphere aggregate bone. Tensile and compressive of concrete and the material failure caused by the defect of ITZ (interfacial transition zone) are studied. The mechanical properties of concrete under cyclic loading is studied and damage simulation of the crack closure behavior by the correcting damage plastic model under cyclic loading is improved.In this thesis, the following work is done.Simulation method of concrete failure were summarized from the perspective of macro-mechanics and micro-mechanics.Stress-strain curves of different concrete damaged plasticity model are given. Different gradations of concrete models are establish on the basis of a representative volume element.Three-dimensional models of ellipsoid and spherical aggregate are meshed, a uniaxial tensile failure simulation is studied. Tensile and compressive of concrete failure caused by the defect of ITZ zone is simulated. The defect of ITZ zone effect different tensile and compressive performance, including the impact on the ultimate load and tensile damage declining trends. A reinforced concrete beam contains three-dimensional aggregates and a homogeneous beam are established. The cross-displacement of homogeneous and heterogeneous model and experimental values were compared. The conclusion that heterogeneity of concrete deteriorates the tensile compressive ultimate and elastic modulus of concrete are reached, load curve of heterogeneous model is closer to the experimental values.The amendments of the plastic damage model improve simulations of crack behavior of CDP(concrete damage plastic model). The research shows that concrete has a great impact on the future crack expansion during the elastic phase, due to the discontinuity and initial damage of the ITZ zone. By simulating the actual reinforced concrete pillars, amended damage plasticity model simulates the curves pinching phenomenon of concrete when subjected to cyclic loading hysteresis. The behavior of concrete RVE element subjected to cyclic loading hysteresis is studied. Strength of ITZ layer not only affects the mechanical properties, elastic modulus and ultimate load of the RVE element, but also have a relatively large impact on the concrete failure surface. ITZ zone of small different strength has great impact on transformation of the concrete failure surface, indicating that ITZ layer has a critical impact on the all forms of destruction of concrete.