| It is presently a concern and a challenge to model numerically shear band localization. Many numerical methods have been developed to take into account the strain and displacement discontinuities across a shear band. In these methods, only smeared shear is modeled and only small deformation is treated. The anisotropy and the inhomogeneity of shear band materials induced by the propagation of localization require the introduction of discrete shear band elements.; In this research, a contact band element approach is proposed to model the propagation of shear bands with finite thickness for large shear deformation. The contact band elements are continuously updated based on their current configurations to prevent large distortions of conventional elements, and alleviate band kinking. In order to model material anisotropy of shear band materials, and to prevent element from overlapping each other, a cross-isotropic elastic model with special Mohr-Coulomb yielding criterion is proposed, in which deformation properties along and across a shear band can be different. In this model, yielding and failure always occurs along a preferred shearing orientation.; One of the highlights of this research is the application of the contact band element approach to interfaces and joints subjected to large shear deformations. Special strain expressions are derived with regard to characteristics of shear strain concentration along an interface. Simulation of a pull-out test has shown that very large pullout displacement can be modeled after the ultimate load has been reached and smooth distributions of mobilized shear stress and axial force along the reinforcement can be obtained.; A framework to incorporate shear band elements automatically and continuously in a finite element scheme is developed. The propagating shear band is modeled with discrete shear band elements which will split up the original finite element mesh. In the original mesh, no shear band element is specified. The use of the proposed empirical bifurcation criterion, location criterion ensure that band propagation is as realistic as possible. Preliminary results from the numerical simulation of biaxial tests and passive earth pressure problems have shown that the discrete band element models closely the actual pattern of shear bands in geomaterials. |
