When concrete is ascribed to combined mechanical loads and high temperature distributions, it exhibits strains which are conventionally [
] split to a set of additive components: - Stress-free components, referred to thermo-hygral strains, which include thermal expansion and hygral shrinkage due to both drying and dehydration. - Stress induced thermal strains which mainly consist in a temperature depend elastic strain, a micro-cracking strain and an additional component, commonly referred to as transient creep [1,2,3].
This additional component is generally related to the fact that physical transformations, such as drying and dehydration, are occurring under sustained stress fields, which lead to a rearrangement of the evolutionary microstructure and give rise to this macroscopically measured strain.
In this contribution, a full coupled thermo-hydro-mechanical model is proposed for the modeling of the transient creep in the range of 105°C-400°C, which is referred here to as
. In this model, a dehydration variable is introduced to describe chemical transformations due to the temperature increase. It also allows to govern the occurrence of the dehydration creep when the stress level does not exceeds 40% of the ultimate strength. In addition, the proposed model considers that the dehydration creep occurs with a kinetics controlled by the relaxation time of the dehydration process. Further, the model allows to describe an irrecoverable transient creep upon cooling or during a second heating to the same maximum dehydration level.
This model have be implemented in a the finite element code CAST3M. The algorithm for the update, at the constitutive level, of the mechanical behavior is presented. A particular attention is the given to the treatment of the transient creep component. Numerical simulations are performed to assess the capability of the model to predict transient load induced thermal behavior of concrete.