Three-dimensional viscoelastic model with nonconstant coefficients

This paper presents a fully 3D viscoelastic model to predict the creep and relaxation behavior of anisotropic materials. This model is based on a phenomenological approach using internal variables and is applicable to nonconstant coefficients. The analytical solution of the set of thermodynamic equations is presented using the reduced time approach in conjunction with modal space. The particular case of isotropic material is presented. Ln addition, from the general 3D model, the analytical solution in 1D is derived and a connection with the classical rheological model is made. Finally, the model is calibrated and assessed with creep test data for concrete in tension and a parameter sensitivity analysis is performed.