On the seismic performance of existing RC motorway viaducts subject to corrosion effects

The durability and the related structural safety of existing reinforced concrete (R.C.) motorway viaducts represent one of the most important research topics in civil engineering, also considering the several collapses that have affected this type of structure in recent years. Focusing attention on the Italian context, it is possible to notice that most of the motorway viaducts were built between the 1960s and 1970s and, consequently, the material degradation has led to a reduction in their load-bearing capacity both under static and dynamic loads, such as the seismic action. In this research work, the evaluation of the evolution of the seismic performance of two existing motorway viaducts as a function of age and considering the effects of corrosion due to carbonation has been analysed. Starting from the geometry reconstruction, Finite Element Models of the viaducts have been implemented considering three different corrosion scenarios: (i) slight, (ii) moderate, and (iii) high. Non-linear analyses have been performed in order to obtain the risk indices defined as the ratio between the value of peak ground acceleration that leads to collapse of the first monitored structural element and the design peak ground acceleration. The results show that as the age of the structure increases there is a significant increase in seismic vulnerability especially for high corrosion scenarios.