Insights into the behaviour of energy piles under different head constraints and thermal loads

The implementation of energy foundations complies with the directives of governments about in-creasing the use of renewable energy sources in the building sector. However, the current design of energy foundations relies more on common practice, based on ideal simplified working condi-tions, than on specific standards. The uncertainties about the role of various key factors on the me-chanical response of the foundation still hinder the confidence in the practice. In this context, the numerical study presented in the contribution highlights the effects of different energy pile head constraints and thermal load histories, in the transient and steady state conditions. The importance of considering the pile head stiffening given by a building slab and the actual thermal load rate is pointed out by discussing the thermally induced axial forces, vertical displacements and shaft stresses. The assessment of the effects of these working conditions can improve the prediction ac-curacy, thus contributing to gain confidence at the design stage.