Calibration and Validation of a Visco-Elasto-Plastic Constitutive Model for Bituminous Conglomerates

The paper presents and discusses the calibration and validation of a three-dimensional constitutive visco-elasto-plastic model developed for the analysis of the mechanical behaviour of bituminous mixes. The methodology, an inverse problem technique, uses a one-dimensional analytic formulation of the constitutive model and four different algorithms of non-linear constrained optimisation: the Conjugate Gradient, Montecarlo, Davidon-Fletcher-Powell and Simplex. On the basis of the creep recovery data obtained from an experiment in support of the model calibration, it was verified that the values of the constitutive parameters can be reliably identified, even starting from different initial guesses. A subsequent comparison between the experimental creep curves and numerical ones of the 3-D model demonstrated minimal shifts, confirming the robustness of the identification procedure for the parameters.