Dynamic identification and collapse assessment of Rubbianello Bridge

This paper investigates the causes of failure of Rubbianello Bridge, a multi-span masonry arch bridge located in Central Italy, which suffered the collapse of two of the seven spans due to foundation scour during a very severe flood in December 2013 and the collapse of two more spans during another major flood event in 2016. An accurate nonlinear 3D model of the bridge is developed. The elastic properties of the model are calibrated based on both material tests and an experimental campaign carried out for the dynamic identification (in terms of vibration frequencies and modal shapes) via operational modal analysis of the remaining part of the bridge. A numerical simulation of the scour hole progression is performed in order to identify the collapse mechanism of the bridge under the first major flood and estimate the level of scour that caused the bridge failure.