by A. Foucault, EDF R&D / AMA
A new model, specially designed for the long-term creep of concrete R7.01.35, is available in the 11.1 testing version. This model BETON_BURGER_FP is built with respect to a rheological chain of Burger (chain of Kelvin-Voigt in series with a Maxwell fluid), separating the deviatoric and spherical parts of the strain tensor. The Maxwell fluid has non-linear properties, functions of the delayed irreversible deformations.
Compared to the BETON_UMLV_FP model already available, this new model permit to no longer impose a constant deviatoric strain rate over time, which led to overestimate significantly the deformation of civil engineering structures for a lifetime exceeding 20 years. In addition, the complete decoupling of deviatoric and spherical parts led to a poor control of the appearing Poisson coefficient due to creep.