Seismic fragility analysis of isolated bridges considering landslide induced differential settlements

The structural safety of bridges and viaducts can be affected by the combination of different hazardous sources. This paper presents a study on the seismic fragility of continuous-deck bridges isolated through elastomeric bearings subjected to ground settlements induced by slow-moving landslides. In the investigated bridge typology, the relative differential displacement of bridge substructure components can involve significant strains of the bearing devices reducing their seismic deformation capacity and determining the increase of bridge fragility. Based on observations on a real case-study bridge, a parametric analysis is carried out to investigate the sensitivity of bridge fragility considering several realistic landslide-induced differential settlement scenarios and variable characteristics of the elastomeric bearings. Seismic fragility curves considering specific settlement scenarios are computed and compared to the undeformed condition to estimate the influence on fragility curves. Results show that a significant increase in fragility is registered for settlement scenarios inducing localized settlements of substructure components and for high-damping nonlinear seismic response.