Elasto-plastic constitutive modeling of plain concrete and an optimization procedure for parameter evaluation

An elasto-plastic constitutive model is developed to characterize the stress-strain behavior of plain concrete. The model utilizes a single yield surface to describe both yielding and failure behavior. An innovative approach is adopted to model volumetric behavior in compressive and dilative regimes. The transition between compression and dilation is identified by the point on the yield surface where the gradient tensor is deviatoric. The proposed approach provides a better control in predicting volumetric behavior of concrete. In addition, the model describes effectively other factors such as hardening, stress path dependency, and variation of shear strength with orientation of stress paths on the octahedral plane. Another unique feature of this model is its ability to account for the variation of the shape of the yield surface on the octahedral plane with confining pressure. An optimization procedure is developed to evaluate the material constants associated with the model. Stress-strain and volumetric responses for a number of tests are predicted and compared with experimental data. Overall, a good agreement between predictions and observations is obtained.