Keywords: coupled problems, isotropic damage, anisotropic damage, bridge deck, shrinkage, concrete.

Concrete exhibits very complicated mechanical behaviour and many material models were developed to describe it but most of them can capture only one or several attributes of this behaviour. This leads to combination of these models. This paper is concerned with damage models for concrete which are suitable for coupled problems. The coupled problems are extremely demanding and therefore the use of very advanced damage models is limited. Usually, the simple scalar isotropic damage models are used.

The proposed anisotropic damage model represents one possible way of damage modelling quite suitable for coupled problems. The basis of this model was described in [1] and the original proposed thermodynamic potential was slightly modified in the volumetric part. The damaged elastic stiffness tensor was also derived which is important for efficient computations in the coupled problems. A parametric study that was performed for better understanding of material parameters in the anisotropic damage model is also presented.

The model was used in the thermo-hydro-mechanical coupled problem of concrete lift layer on the bridge deck. The layer is thin and it is often damaged due to shrinkage and climate conditions. The problem was also solved with the scalar isotropic damage model and some comparisons were made.

Results from the analyses performed showed that the shrinkage and climate conditions play key role in the process of the damage evolution. The effects of climate conditions (sun radiation) can be suppressed by proper care. That means the concrete layer has to be shielded and covered using polyethylene sheets and the cast concrete layer has to be watered at least for three days. Although the proper care is guaranteed and reinforcement grid is assumed, the lift layer has a tendency to separate from the background and the so called boundary effect arises. This implies that the boundaries have to be anchored. The top of the lift layer is also affected by autogeneous and drying shrinkage and it can be suppressed using microreinforcement.

1

E. Papa, A. Taliercio, "Anisotropic Damage Model for the Multiaxial Static and Fatigue Behaviour of Plain Concrete", Engineering Fracture Mechanics, Vol. 55, No. 2, 1996. doi:10.1016/0013-7944(96)00004-5

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