1. Introduction

In the context of studies of the long-term behavior of concrete structures, a preponderant part of the deformations measured on structures concern the delayed deformations that appear in concrete during its life. They include early age withdrawals, desiccation withdrawal, clean creep, and desiccation creep.

The model presented here is dedicated to the modeling of delayed deformation associated with natural creep. Clean creep is, in addition to desiccation creep, the proportion of creep in concrete that would be observed during a test without exchanging water with the outside. Experimentally, concrete with its own creep shows viscous aging behavior. The observed creep deformation is proportional to the loading stress and depends on temperature and humidity. As in elasticity, longitudinal deformation is accompanied by a transverse deformation of opposite sign.

The model chosen is inspired by the one proposed by L. Granger [bib1]. It is a visco-elastic model that takes into account the effect of aging and humidity. The effect of temperature is not modelled.

First, a brief review of linear visco-elastic models is made and then the model itself and its numerical integration are presented in c*ode_aster*.

In c*ode_aster*, two versions are available: BETON_GRANGER_V the complete model, and BETON_GRANGER, which does not take aging into account.