Defects detection of pier and abutments foundations: an overview of a recent experience in Basilicata (Southern Italy)

Piers and abutments are bridge supports temporarily or permanently immersed into the water, that may suffer erosion and scour phenomena. As known, the latter involves different processes at different spatial scales not easy to investigate in a combined approach, such as: contraction scour, local scour, gradation of the soil bed, river channel dynamic, climate change and hydrological forces. To this, it should be added that piers/abutments are highly exposed to environmental actions, such as earthquake, landslides and floods that may seriously compromise their stability and, consequently, lead the bridge or an its portion to an out-of-service, or else to a failure. Therefore, it is important to properly identify and assess defects extent and severity on piers and abutments, in order to evaluate their conservation status, and to formulate a judgment for ranking priorities within a multi-level and multi-criteria framework, such as the recent guidelines issued by the Italian Ministry of Infrastructures and Transport. To this regard, in this work an overview of some significant defects related to piers and abutments, with particular emphasis to the ones due to the interaction with the water flow, are illustrated and commented. They are collected in an on-going campaign of inspections performed in the Basilicata region (South of Italy), concerning bridges falling within State Roads networks. Comments are made from a structural and hydraulic point view, in order to highlight the inspected defects importance within the Classes of Attention, according to Italian Guidelines for bridges.