PSI - Issue 62

Andrea Nettis et al. / Procedia Structural Integrity 62 (2024) 693–700 Author name / Structural Integrity Procedia 00 (2019) 000 – 000

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Fig. 1. Description of the case-study bridge.

Based on the abovementioned case study, three bridge realisations are generated by varying the typology of elastomeric bearings ranging among low-damping natural rubber bearings (LDRB), high-damping rubber bearings (HDRB) and lead rubber bearings (LRB). LDRB have a low critical damping ratio (2% – 3%) with respect to the other elastomeric bearing types and exhibit a linear behaviour under incremental shear strains. Conversely, the use of HDRB involves high dissipation capacity in the seismic response since HDRB are generally associated with a higher equivalent viscous damping higher than 10%. Such bearing type involves the need for advanced nonlinear modelling in seismic response analysis. LRB are composed of layers of rubber with bonded steel shims and a central lead plug fixed between two steel plates. The dissipation capacity of LRB is related to the nonlinear response of the lead core which can induce equivalent viscous damping values approximately equal to 20%. The generated realisations are designed considering the design seismic action prescribed by the Italian code for the bridge location. Four landslide-induced settlement scenarios, named S1, S2, S3 and S4 are assumed (Fig. 2). Preliminary displacements in the bridge transverse direction are imposed at the base of the substructure components to observe their influence on fragility. The settlement scenarios are defined by varying the intensity of the displacement on substructure components. The maximum displacement observed onsite is assigned to one of the bridge substructure components. Fig. 2 presents the settlement scenarios, quantifying the displacement imposed on each substructure component. The landslide-induced strain on the elastomeric bearings is also indicated as an example.

Fig. 2. Landslide-induced settlement scenarios. indicates the displacement at the base of the substructure components, while expresses the initial strain for the elastomeric bearings for the case-study bridge equipped with LDRB.