Multi-hazard assessment of a masonry railway bridge in landslide areas

Earthquakes and landslides pose a high risk to road infrastructure due to unfavorable geological conditions in conjunction with extreme climate events. In particular masonry arch bridges are very often affected by natural events such as floods, landslides, and earthquakes, causing the partial or total collapse of the bridge. To determine the vulnerability to the multiple hazards related to a specific area, a multidisciplinary approach that allows to analyze the different issues is needed. Non-destructive survey strategy based on the study of geo-morphological area, in situ tests and accurate numerical modelling are required to perform a multi-hazard vulnerability assessment of a masonry bridge in a landslide area. In this paper, a multi-disciplinary multi-sensor methodology is proposed based on photogrammetric and thermographic surveys, for the definition of an accurate georeferenced three-dimensional geometrical models of the bridge for a reliable definition of a numerical model to be adopted for the structural assessment of the bridge consistent to a multi-hazard scenario. Namely, a discrete macro-element models (DMEM) based on the software HiStrA Bridge has been applied to determine the soil-structure interaction associated to landslides events. The masonry arch railway bridge chosen for this study is located in a complex geological and geomorphological context. In fact, earth landslides affecting the bridge and poor physical-mechanical characteristics create the conditions for a complex case study. The objective of this study is to assess the vulnerability of masonry bridges subject to the combined effects of landslides, and hydraulic hazard due to bridge occlusion by the modeling of these effects.