On Thermo-Hydro-Mechanical (THM) Fatigue Damage of Historical Stone Buildings

Abstract

The efficient conservation, restoration and protection of stone historical buildings could not be dissociated from the researches of mechanism of stone decays. While various mechanisms of stone degradations are considered and studied in previous studies, in this paper is focused on the cumulative damage modeling of wall stones due to the fatigue induced from quotidian fluctuations of thermal and hydric conditions. The thermoporomechanics theory of partially saturated media is used to describe the behavior of stone wall and its interaction with climatic conditions. Further, the effective stress concept firstly introduced by Terzaghi is extended for partially saturated media providing a quite powerful tool for design and analysis [. The behavior of a typical stone wall from Chambord castle (Center region of France) is then simulated, taking into account the heterogeneity of the stone-mortar contacts. The climatic conditions are introduced in the model as boundary conditions. The records of temperature and humidity from meteorological stations close to castle are used to establish time-variation of condition with a time resolution of 6 hours. From performed numerical analyses, it is shown that variation of temperature and relative humidity leads to the variation and fluctuation of effective stress in the stone, more intensively on the outdoor. The contact of stone with mortar is a natural stress concentration center, but even there the stress is much lower than tensile strength of the white tuffeau stone. The fatigue of the stone due to the stress fluctuation induced by the variations of meteorological conditions seems to be a major factor of stone degradation. A model is used to assess the cumulative damage of the stone wall as a function of the time.