Thermal stress and damage risk in the stones of Al-Ziggurat in Al-Nimrud city, Iraq

The aim of this paper is to assess the risk of climate-induced damage to stone through the calculation of thermal stresses. The stone studied is white limestone, the building stone of the walls of Al-Ziggurat in Al-Nimrud city, Iraq. In order to assess the effect of climate on stone behavior, we measured the stone surface temperature and the extreme values of air temperature (i. e. actual stone dataset). As these parameters were measured for short period, they were completed with weather data recorded from Mosul station for three years (i. e. weather dataset). The actual stone data were used to estimate the statistical difference between stone surface temperature and air temperature. The weather data were treated with respect to actual stone data in order to estimate the thermal stress for a statistically relevant duration. The mechanical properties required for stress calculation are the elastic modulus, the Poisson's ratio and the thermal expansion coefficient. A simple mechanical model was applied to estimate the stress generated by restrained thermal strain. Results show that the risk of damage to the stone exposed to climate fluctuations can be significant. The damage risk is higher to the stone in the south wall orientation than in the north one. The combined use of both datasets proved to be usefull, since the damage risk is significantly higher with the resulting estimation compared to the exclusive use of actual stone data. (c) 2018 Published by Elsevier Masson SAS.