Mesoscopic Numerical Simulation And Test Study On Concrete's Size Effect

In this paper, the size effect of concrete prisms' compressive strength and the samples' destruction process under uniaxial compression are studied experimentally. Test results show that the uniaxial compressive strength of concrete specimen decreases when its geometry size increases; reinforced concrete prisms have greater size effect parameters than concrete ones. The concrete's failure is due to its internal micro-cracks' cumulation.Then the concrete is taken as three-phase composites consisting of mortar matrix, aggregate and the bond between matrix and aggregate. Based on the random distribution of aggregate in concrete, the optimal gradation formula is adopted, and the throwing programs of aggregates for two-and three-dimensional concrete samples of various sizes are made. Some mesh generation methods urually used in finite element are studied, and multi-mesh technic is adopted to get the reasonable mesh sizes.Taking the aggregate, mortar matrix and the interface as isotropic materials, and the mechanical parameters of aggregate, mortar matrix and concrete are measured by experiments. With series of discrete value on interface parameter, the relationship of elasticity modulus of interface and concrete is obtained, and the interface elastic modulus is estimated appropriately.Based on the random aggregate distribution meso-finite element models, the uniaxial compression tests are carried out and their failure processes are simulated. The compressive strength is gained deduced from the limit carrying capacities and the geometric size of concrete samples.Mesoscopic numerical models of homogeneous and heterogeneous concrete are established in combination with elastic brittle constitutive and both elastic brittle and plastic constitutive for concrete mesoscopic elements. The numerical tests about the progressive failure process and the nonlinear mechanics behavior of concrete specimen under compression are carried out. Then the macro mechanical results of various numerical models and tests are compared and analyzed.The uniaxial compress tests of numerical concrete specimen with three different geometry sizes are carried out. The scaling laws of the specimen's uniaxial compression strength are gained and coinside well with physical tests.