CDM-XFEM METHOD FOR CRACK CALCULATION CONSIDERED PLASTIC DISSIPATION OF CONCRETE

The concrete structure is easy to appear cracks under external loading during service, which leads to the reduction of structural stiffness and the decline of bearing capacity. Using accurate calculation method to predict the cracks development of concrete is the basic premise for crack control, and also the important measure to ensure the safety of structure. Continuous damage method (CDM) can describe the propagation process of micro cracks, but cannot represent discrete crack surface and contained disadvantages of grid induced deviation and false stress transfer, mechanics-extended finite element method (XFEM) can describe the propagation process of macro cracks, but cannot reflect the dynamic propagation of micro cracks, the cracks distribution calculated by the two methods are all quite different from the actual situation. The existing CDM-XFEM method can effectively simulate the whole process of concrete micro and macro cracks development, but the concrete plastic strain is ignored when the macro cracks appeared, so the energy conversion between CDM and XFEM is lack of balance. In this paper, the plastic dissipation of energy conversion is considered, the exponential function is selected as the traction separation mode of cohesive crack, based on the principle of energy and stress equivalence, the energy conversion equation between CDM and XFEM is reconstructed, the generalized inverse least square method is used to solve the energy conversion coefficient and determine the critical displacement during energy conversion, the updating algorithm of crack level set and overall calculation procedure are given out. Taking the shear tensile cracking experiment of concrete with double incisions as an example, various calculation methods of concrete crack are compared with the experiment. The results show that the crack distribution and tension-displacement curve calculated by CDM-XFEM method considered concrete plastic dissipation is most close to the experiment, which indicates that CDM-XFEM calculation method considered concrete plastic dissipation can better calculate concrete cracks.