Thermo-mechanical behaviour of energy geostructures subjected to bending thermal actions

The energy geostructures are an innovative multifunctional technology that couples their structural support with the heating/cooling role of heat exchangers. The heating/cooling operations of such technology lead to thermo-hydro-mechanical interaction between the structure and the surrounding elements such as the soil and the groundwater. The temperature change in the geostructure can be uniform or non-uniform, leading respectively to thermally induce axial strain and curvature. The first aspect has been well studied, especially for energy piles, while the latter is still underresearched and involves generally for plane energy geostructures, such as walls or slabs. Nowadays, any simplified method exists for the study of such structures. To address this challenge, this works presents two methods for analysing the behaviour of plane energy geostructures subjected to bending thermal action. The first method uses the subgrade reaction theory, particularly the Winkler’s model, in order to estimate the soil-structure interaction of such elements. Comparisons with finite element models outline that this method generally slightly underestimates the deformation, but captures well the internal forces. An extension of this method to more complex structures, such as cut and cover structures, showed its conveniency to estimate the behaviour of connected elements. The second method is based on design charts that have been developed in order to capture the behaviour of the structure. Those charts give graphically the maximum response for a beam which is subjected to various loads, including thermal load. This work also showed that the behaviour of plane energy geostructures subjected to thermal bending is strongly related to the boundary conditions, such as the end conditions and the supporting soil. A structure characterised by a low degree of freedom leads to small deformation, but high internal forces, and vice versa.