Feasibility study of a seismic isolation system for a composite steel-concrete bridge in Bologna

The seismic performance of transport infrastructure represents a fundamental design requirement in regions characterized by moderate to high seismic hazard, such as Northern Italy. In this context, the present thesis investigates the feasibility of implementing seismic base isolation in a composite bridge designed to serve the new tramway system of Bologna. The study evaluates the structural response of the bridge under seismic loading by comparing two configurations: a conventional rigid support system and a flexible system equipped with base isolators. The assessment is carried out through analytical calculations based on current seismic design provisions of Eurocode & NTC18 and through numerical modeling using SAP2000. Dead loads and seismic actions are evaluated in accordance with relevant design standards, and the dynamic properties, base shear, internal forces, and displacement demands are determined for both structural configurations. The results highlight the influence of base isolation on the fundamental period of the structure and on the redistribution of seismic forces. A significant reduction in base shear and pier forces is observed in the isolated configuration, accompanied by an increase in displacement demand at the isolation level. The comparison between analytical and numerical results confirms the consistency of the adopted modeling approach. The study concludes with an evaluation of the structural effectiveness and practical feasibility of adopting base isolation for the considered bridge, discussing its advantages and potential limitations within the framework of urban tramway infrastructure.