Seismic reliability of Italian code-conforming bridges

Seismic reliability assessment of selected bridge structures code-conforming with respect to the current Italian practice is carried out. Two viaducts, tall and shallow, and two highway overpasses, with traditional seat-type or integral abutments, are considered. Each structure is ideally placed at three reference sites, that is, Milan, Naples and L'Aquila, characterised by low, moderate and high seismic hazard, respectively. At each site, a soil profile representative of typical local conditions is defined for foundation design, site response analysis and soil-structure interaction modelling. Probabilistic seismic hazard is used in conjunction with multiple-stripe non-linear dynamic analysis, featuring conditional-spectrum compatible ground motions, to establish the failure rate with respect to two purposely defined and functionality-related performance levels. It is confirmed the decreasing seismic reliability with increasing design seismic action, already observed for other structural types, and it is shown that integral abutment overpasses tend to be more reliable than traditional ones, even seismically isolated ones. The results are of larger interest given the closeness of the Italian code to the Eurocode.