| The computational analysis of the hygrothermal and mechanical behavior of orthotropic wood or concrete structures is carried out by means of the finite element method (FEM). In order, to evaluate the thermal and hygral performance of these structures and to assess the associated mechanical effects (stresses, creep, cracking, etc.), the knowledge of heat and moisture transfer process taking place within the constitutive material is required.; The three-dimensional hygrothermal model is based on the concept of “water potential” to characterize the moisture transfer in both wood and concrete. Heat transfer by conduction and heat generation by chemical reaction in concrete and phase changes are considered. The theoretical approach used to obtain the governing differential equations for heat and moisture transfer is based on the procedure of averaging the continuum equations applied to heat and mass transfer and drying processes. The FEM is then used to discretize the weak Galerkin variational form of the partial differential equations describing heat and mass transfer. The FEM is well adapted to deal with the variable material properties in the domain considered. Hence, the respective effects of sapwood and heartwood are accounted for by changing the local material properties (specific gravity, permeability, and initial moisture content). A rotational matrix between the local and global coordinate systems is used to take into account the curvature and orientation of the growth ring and the slope of grain. For concrete, the heat generation and water consumption due to hydration is also considered. It is interesting to note that both wood and concrete can be analyzed using the same base model.; Several examples of validation/simulation were presented in order to illustrate the overall performance of the model. For instance, it was used to simulate the three-dimensional drying of wood taking into account the anisotropy of its internal structure. The numerical results were found to be in good agreement with the experimental ones. The hygrothermal behavior of concrete, taking into account of the effects of heat generation and water consumption due to the hydration chemical reaction, was also simulated, and though they could not strictly be compared to experimental results, the numerical data appear to be physically consistent. |
