Study On The Static, Dynamic Mechanical Properties Of (Fully-graded) Concrete Based On Mesomechanics

The concrete is considered as a three-phase composite composed of matrix, aggregate and interface between them on meso-level in this dissertation. Its mesoscale structure is represented with random aggregate model by using Monte-Carlo method. Then, the bilinear damage evolution model is adopted to describe the meso-element's damage devolution. The macro-mechanical properties of wet-screened concrete and fully-graded concrete are simulated with non-liner FEM, The major research work is summarized as follows:1. According to the test data, the axial compression tests of two-graded, three-graded, four-graded concrete cubic specimens were simulated. Size effect on the compression strengths got from numerical simulation is fitted with the experiment results. Cracks are generated from the interface and extended in a direction parallel to the maximum compression stress.2. Based on the random aggregate model, the continuous grain size's aggregate model is established. Homogenization is verified in the axial tension tests of two-graded concrete and applied in the axial tension test of four-graded concrete.3. The bending-tension tests of two-graded, three-graded, four-graded concrete beam were simulated using displacement-controlled FEM. The corresponding total stress-strain curves were got. Furthermore, size effect and grade effect on the bending strengths are analysised.4. According to the Specifications of Seismic Design of Hydraulic Structures, the dynamic damage model of meso-element is developed. Based on this model, the microscopic failure mechanism of two-graded, four-graded concrete under impact loading is simulated. The dynamic stress-strain curve of specimens and their dynamic compression strengths were got.5. Based on the existed experimental data on the concrete and composited material's strain-rate effect, the dynamic damage constitive model considering strain-rate strengthening effect is developed. The failure mechanism of fully-graded concrete beam under impact loading, triangle wave load, dynamic load coupling with initial static loading were simulated. The results obtained from numerical simulation have a good fit with experimental data.6. 3D random aggregate model was proposed based on the homogeneation. Furthermore, combining the mesh generation of ANSYS, this paper brought forward a method of using secondary development in AutoCAD by VB programming to realize 3D visualization of aggregates and meso-elements.7. The bilinear damage evolution model is extended to 3D. The compression tests of one-graded cylinder concrete specimen, two-graded cylinder concrete specimen and cubic concrete specimen, three-graded cubic concrete specimen is simulated.