Analysis of the effects of foundation settlements on seismic fragility curves of unreinforced masonry buildings

This thesis investigates the seismic fragility of masonry structures considering the negative effects of subsidence. Unreinforced masonry buildings are widely present in historical and modern urban areas, yet they are highly vulnerable to seismic events. This work aims to analyze how differential settlements influence the structural response, damage distribution, and fragility curves under earthquake loading conditions. The research is conducted through numerical modeling using nonlinear static analysis, pushover analysis, and the N2 method to evaluate the seismic performance of a representative masonry building. Two scenarios are considered: the original state and a 5mm imposed settlement at the foundation level case. The comparison between these two cases allows for an assessment of the impact of settlements on seismic fragility. Results indicate that foundation settlements significantly decrease the structural performance, leading to increased displacement demands and reduced base shear capacity. The fragility curves derived from the analysis show a higher probability of exceedance for each damage state in the settlement affected scenario. This highlights the necessity of incorporating settlement effects into seismic vulnerability assessments. Furthermore, in the study a constant dispersion value literature based is considered, as proposed by Lagomarsino and Cattari. The results of this research have important implications for seismic risk assessment. Engineers and urban planners should account for soil-structure interaction effects to improve the resilience of existing masonry buildings. A comprehensive approach in seismic vulnerability assessment, integrating geotechnical and structural considerations addressing foundation settlement effects in fragility models will contribute to more reliable seismic risk evaluations and the development of effective mitigation strategies for masonry structures in regions affected by a high seismicity.