Hydrothermal stress and damage risk in the stones of the castle of Chambord-France

The aim of this paper is to assess the risk of climate-induced damage to stone through the calculation of hydrothermal stresses. The stone studied is tuffeau, the main building stone of the Castle of Chambord. The climate is assessed though measurement of the stone temperature and relative humidity using sensors inserted into the stones of the castle. The mechanical properties required for stress calculation are the elastic modulus, the Poisson's ratio and the hydrothermal strain. A numerical model based on restrained strain was used to estimate the hydrothermal stresses, which were analysed through the calculation of their daily variation, or alternatively by comparison with core behaviour. The parameters studied include the depth in the stone, the orientation of the walls, the alternative calculation methodology, and an optional correction of stone data due to sensor accuracy. Results show that the risk of damage to the stone exposed to climate fluctuations can be significant: joint cracking due to tension near the stone surface, and surface buckling due to compression for stones already subjected to spalling, leading to crack propagation. The risk decreases with depth, and is maximal on the south wall. Sensor accuracy for high relative humidity proved to be a significant issue.