Influence of the Deck Length on the Fragility Assessment of Italian R.C. Link Slab Bridges

This work focuses on the fragility assessment of reinforced concrete multi-span continuous bridges, which is a widespread structural typology in Italy, with the aim of investigating the peculiar vulnerabilities of the bridge class under investigation, the reinforced concrete link slab jointless bridges. The need for a deeper study on the topic derives from the wide diffusion of such typology on the Italian road network, which has been recently struck by earthquakes and needs intervention works for the safety of old bridges and viaducts. Starting from a real case study located in Centre Italy, a couple of reinforced concrete bridge case studies is chosen in order to consider the influence of different length for the deck and to provide a forecast for the structural behaviour of the selected bridge class. The associated numerical models are able to capture the failure mechanisms most likely to occur, and a dedicated modelling strategy is developed to capture the potential failure on the kinematic links on the superstructure. A probabilistic framework is developed considering both the site-dependent seismic hazard, which accounts for the parameters characterizing a medium seismicity level area as well as the record-to-record variability, and the demand parameters related to the examined vulnerabilities. Seismic analyses are carried out through the Multiple Stripe Analysis methodology to furnish the fragility curves for all the response parameters relevant for the structural system. Performance thresholds are chosen for each bridge component according to the current codes and literature. As a result, fragility curves provide useful insights about the main structural deficiencies of the system at hand in order to evaluate possible intervention strategies against social and economic losses.