The Fragility of Link Slab Viaducts: Analysis of a Case Study in Central Italy

Recent seismic events occurred in Central Italy drew the attention towards the resilience of the Italian road network, which is characterised by a significant number of old reinforced concrete bridges and viaducts. In this context, the fragility assessment of existing bridges is crucial, since their collapse or loss in functionality after earthquakes may lead to significant economic and social consequences. As a part of a more general study oriented to characterize the fragility level of the Central Italy bridge stock, this work focuses on the real case study of the Chiaravalle viaduct, which may be representative of a widespread class of reinforced concrete bridges in Italy: the viaduct is a continuous multispan bridge consisting of precast simply supported V-shaped beams connected by a continuous slab. A numerical model is developed in order to capture the failure mechanisms most likely to occur for this bridge typology subjected to seismic actions. A probabilistic assessment of the seismic response of the bridge is carried out by performing multiple stripe analysis, considering a seismic scenario consistent with the Chiaravalle site. Fragility curves, built by accounting for the main demand parameters and the relative limit states, provide useful insights about structural deficiencies of the system at hand.