Effect of degradation on the structural behaviour of an existing cantilever reinforced concrete bridge in Southern Italy

The performance of cantilever reinforced concrete bridges is fundamental topic in assessment and retrofit of Italian infrastructures, because the static scheme of the so-called “Gerber bridges” was very popular between 50’s and 70’s of XX Century. Many of them present severe damage due to the drainage of the deck waters inside the joint and to the consequent degradation of Gerber saddles. Furthermore, the state of corrosion of the reinforcements together with the actual degree of freedom of internal constraints, often partially blocked due to degradation and subsequent maintenance over time, modify the structural behaviour and the performance both in terms of service and ultimate limit states. This paper presents a case study of a reinforced concrete bridge with a three-span cantilever scheme, designed in southern Italy by Riccardo Morandi, in which this problem led to a difficult assessment of the actual performance of the bridge. The on-site static and dynamic investigations and the bridge modelling in its current condition, taking into account the effects of degradation in the Gerber saddles, made it possible to evaluate the state of the bridge after more than 60 years from construction