The effects of moisture-induced degradation on the structural performance of historical buildings: a case study

A significant fraction of Italian building scenario consists of historic masonry buildings with high cultural value. In recent years, structural health assessment and monitoring of such buildings has become fundamental, not only for heritage conservation matters, but also for safety. In fact, several historical buildings are used for strategic assets (e.g. administration offices, police stations, education services). Therefore, assessing the seismic vulnerability of these structures, along with the effects of material degradation over time, is crucial to ensure their preservation. Literature studies and recent tragic events evidenced the urgency of retrofitting highly degraded historical structures, to prevent major consequences on society. To this regard, the accurate assessment of the structural performance degradation due to material ageing is an aspect of paramount importance. In the case of masonry structures, moisture content reduces the compressive strength and Young’s modulus of stone materials. This study analyses the effects of moisture-induced degradation on a case study strategic masonry building, realized using Lecce Stone walls typical of southern Apulian regions. In-situ investigation alongside literature results were used to define mechanical properties of bricks at different saturation levels, aiming to develop degradation-dependent constitutive laws. Subsequently, a finite element model of the case study building was developed, aiming to investigate the evolution of structural performance over time depending on the moisture-induced material degradation. Modelling uncertainties were considered to define a worst-case and a best-case degradation scenario. Linear time-history analyses using spectrum-compatible ground motions were performed to evaluate the impact of moisture on the dynamic properties and floor response spectra.