Bounding Surface Model For Concrete Under Triaxial Loading

Great progress has been made on research of constitutive model for concrete, but the complicated nonlinear and nonelastic nature for concrete is difficult to simulate.In order to describe material nature of concrete, various forms of new plasticity constitutive model appear. Especially the bounding surface model is being paid great attention to, because of its superiority on reliable simulation.A model that combines plasticity and damage mechanics is developed to assess both multiaxial and cyclic behavior of concrete. The model adopts a bounding surface concept and combines plastic deformation with the deformation due to damage. Plastic strain components are calculated by using the plastic modulus that is a function of the distance form the current stress point to the bounding surface along the deviatoric stressdirection s_ij. Similarly, damage growth rate is obtained by the hardening modulus,which is a function of the distance just defined. The hardening behavior of concrete is assumed herein to be controlled by both damage and plasticity, while the strain-softening regime is controlled by damage processes only. The simultaneous use of the plasticity surface and the damage surface, leads to a constitutive model that accounts for the essential features of concrete such as shear compaction-dilatancy, stiffness degradation, and softening behavior.