PSI - Issue 78

Gabriele Fiorentino et al. / Procedia Structural Integrity 78 (2026) 245–252

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Fig. 5. Displacement response spectra of the selected natural ground motions. Green dotted vertical lines represent the first longitudinal modes for Piers 4-6 and 5. 5. Conclusions This study presents preliminary results for the OpenSees numerical model of two tall piers of an existing isostatic multi-span Reinforced Concrete bridge located in a highly seismic area in Italy. Modal analysis allowed for the determination of natural vibration periods of approximately 1.09 and 2.12 s. Modelling the influence of SSI with a simplified impedance model seems to have limited influence on natural vibration periods. The seismic input is defined in terms of spectrum-compatible ground motions, using both natural and simulated accelerograms, highlighting the need to carefully define sets of suitable ground motions in highly seismic conditions, where earthquake scenarios with M > 7 can hinder the possibility of finding natural ground motions. The adopted strategy for ground motion selection, combining spectrum-compatible natural records and synthetic signals from the SIGMA simulator, offers a comprehensive suite of inputs tailored to the scenario earthquake. While the current model is fully elastic and serves as a benchmark, it will be progressively enhanced with nonlinear material models for both structure and soil to assess damage and ductility demands. A more comprehensive model of the entire bridge, including a 3D representation of the surrounding soil domain, is planned and will be crucial for fully understanding the global dynamic response and informing future retrofitting and monitoring strategies for similar tall This work was supported by the Royal Society (RS) and the Consiglio Nazionale delle Ricerche (CNR) through the Joint Bilateral Agreement CNR/RS, Project SIM, Biennial Programme 2025-2026 (CUP: B63C25000450001), IEC\R2\242059 - International Exchanges 2024 Cost Share. References Capurso, G., Martire, F., 2020. Designed for machines. Italian bridges and viaducts (1965–1990). Rivista Tema (Technologies Engineering Materials Architecture) 6(2), 42–51. https://doi.org/10.30682/tema0602d Chen, X., Li, J., Zhang, C., 2019. System fragility assessment of tall-pier bridges subjected to near-fault ground motions. Journal of Bridge Engineering 25(3), 04019143. DISS Working Group, 2025. Database of Individual Seismogenic Sources (DISS), Version 3.3.1: a compilation of potential sources for earthquakes larger than M 5.5 in Italy and surrounding areas. Istituto Nazionale di Geofisica e Vulcanologia (INGV). https://doi.org/10.13127/diss3.3.1 Fiorentino, G., Sabetta, F., De Risi, R., 2025. SIGMA: a new tool for the simulation of spectrum-compatible earthquake ground motions. Natural Hazards, 121, 15163–15188. https://doi.org/10.1007/s11069-025-07387-w pier viaducts in Italy. Acknowledgements