Meso-level Numerical Analysis Of The Damage Evolution Of Concrete Specimen

Concrete is a widely used building material in civil engineering, which has been gradually used in the nuclear reactor containment vessel, offshore platform and high arch dam. In these complicated structures, the appropriate design and analysis depend on the constitutive relations and failure criteria under multiaxial stress states. So far, material mechanics experiments and mesoscopic numerical simulation are the two important paths. As the loading equipment and testing technique are quite complex for mechanics experiments, the tradition test methods are confronted with a lot of challenges. With the quick development of high performance computer and numerical computation methods, mesoscopic numerical simulation, which is relatively cheap, may be a complement or substitute for the former. In this paper, the damage and fracture process of concrete under uniaxial load is investigated at the meso level, and numerical simulation tests are carried out on the basis of secondary development of the large FEM software ANSYS.During simulating the process of damage, random aggregate model and random mechanics parameter model are used. Firstly, by using the polygon-polygon overlap test and region filling algorithm of computer graphics, an advanced method is presented to generate aggregates with random shapes and sizes according to the given aggregate gradation curve and aggregate area fraction. And human interference is added in generating two-dimensional random aggregate model. Secondly, an automatic finite element mesh is adopted, while the material property of each element is determined from the position of the mesh in the random aggregate model. Finally, the material mechanics parameters, which subject to random distribution, are assigned to elements. Now, the numerical model is formed. For the mesoscopic element, tensile damage and compression-shear damage can occur, and bilinear damage model is adopted.For C20 and C35 concrete, which are common in engineering, numerical experiments are conducted under uniaxial load. From the stress-strain curves and the pictures of crack propagation, the damage and fracture evolution process is analysed. First of all, microcracks usually originate from the weakness of concrete, especially, the interface elements located in the angular points of aggregate between the aggregate and matrix. Moreover, microcracks develop at the scale of the matrix, involving debonding or even breaking of the closest aggregates. Eventually, the visible cracks are formed, leading to the eventual failure of...