Seismic reliability of representative Italian code-conforming highway bridges

This report provides a comprehensive description of the design methodology, numerical modelling and results relative to the research project Reluis-DPC 2019\21. Probabilistic seismic assessment of selected representative modern bridge structures from the current Italian practice is carried out. Two viaducts and two highway overpasses are considered. Each structure is ideally placed at three reference sites characterized by an increasing seismic hazard. At each site, a soil profile representative of typical local conditions is employed, and the considered structures are designed in accordance with Italian technical provisions currently in force. Probabilistic seismic hazard is used in conjunction with inelastic response history analysis employing conditional-spectrum compatible recorded motions, within a multiple-stripe analysis framework, to establish the mean annual frequency of exceedance for two purposely defined and functionality-related performance levels. Refined inelastic spatial models including soil-foundation-structure interaction are implemented in OpenSees for this purpose. The results quantify and provide insights on some expected facts, like the decreasing reliability with increasing hazard, already observed for other structural types, and the better performance of some structural solutions with respect to others, with integral abutment overpasses performing better than traditional ones and even of seismically isolated ones. A general view to the results obtained is provided, together with a discussion of the critical issues in the expected seismic performance for bridges. This study was carried out within the activities of the ReLUIS-DPC and DPC 2019–2021 research programs, funded by the Presidenza del Consiglio dei Ministri—Dipartimento della Protezione Civile (DPC). The opinions and conclusions presented by the authors do not necessarily reflect those of the funding agency.