CONSIDERATION OF AGING OF SHOTCRETE IN THE CONTEXT OF A 3-D VISCOPLASTIC MATERIAL MODEL

The structure of the classical theory of viscoplasticity and its algor ithmic formulation in the context of an operator split scheme is exten ded to account for the effect of aging. Within this framework, a 3-D m ultisurface constitutive model for shotcrete is proposed. A rotating-c rack model based on the Rankine criterion is adopted in conjunction wi th a Drucker-Prager yield criterion for describing the mechanical beha viour of young concrete in the compressive regime. The model is suitab le for the representation of the time-dependent behaviour of shotcrete including creep and the time dependence of strength and stiffness. A computationally effective return mapping scheme is achieved by formula ting the material model in terms of the principal directions and trans forming the obtained relations to global axes. Linearization of the re turn mapping algorithm yields the algorithmic tangent moduli.