RC tied-arch bridges: Typological analysis for the definition of retrofit interventions

The Italian bridge asset is characterized by aged structures, most of which made of reinforced concrete, needing retrofit interventions to improve both their seismic performance and load-bearing capacity towards the increased traffic volume. In order to provide a series of guidelines for retrofit, a research project, carried out by the ReLUIS consortium supported by the Italian Department of Civil Protection, aims to identifying typological deficiencies and vulnerability of the main type of bridges widespread on the Italian territory, defining typological interventions. This paper presents the outcomes of the ongoing research focusing on RC tied-arch bridges, frequently built in the period between the two world wars. A typological study was carried out to define the main design deficiencies and construction details, and how degradation acts on this type of bridge, besides the main structural vulnerability to both gravitational and seismic loads. Numerical and parametrical analyses were carried out on a representative prototype tied-arch bridge with RC hangers, dating back to 1930s. The structural behavior was assessed by means of numerical analysis on FEM models, allowing the evaluation of the static and seismic capacity, the definition of the most vulnerable elements, and thus, the identification of the most suitable type of retrofit interventions.