The role of masonry typology in the settlement-induced analytical fragility of stone masonry buildings

The structural vulnerability assessment of existing masonry buildings is of increasing importance in urban areas, particularly in the Mediterranean region where such structures represent a significant portion of the building stock. This work addresses the vulnerability of residential stone masonry buildings subjected to ground settlements, a less explored topic compared to seismic vulnerability. Previous studies have largely relied on empirical methods for the assessment of damage due to differential settlements, focusing on criteria such as differential settlement ratio and angular distortion. The present study contributes to addressing the limited literature on this topic by applying nonlinear analytical approaches to assess the fragility of stone masonry buildings under these conditions. The methodology involves the application of monotonically increasing differential settlements at the base of the structural elements, followed by a detailed estimation. Five conventional damage states, derived from the force-deformation constitutive relationships of the nonlinear hinges (moment-rotation for flexural hinges and force-displacement for shear hinges), are used for this purpose. The European Macroseismic Scale EMS-98 provides the framework for the definition of these damage thresholds. The results show that the masonry typology significantly influences the structural response: stiffer masonry types reach elastic damage states earlier, while irregular masonry exhibits higher vulnerability in ultimate damage states. Three-story buildings are more vulnerable than single-story buildings, requiring lower differential settlement and angular distortion values to reach the same damage states.