Reference structural investigation on a 19th-century arch iron bridge loyal to design-stage conditions

This work gathers the outcomes of a comprehensive case study concerning a reference structural investigation on the bridge at Paderno d’Adda, a monumental arch iron viaduct completed in 1889, situated in Lombardy (northern Italy), still keeping today a crucial position within the local railway and road transportation networks. The bridge is part of precious architectural heritage, together with a few rather similar bridges in Europe, which may be in the predicate to become part of the UNESCO list. A comprehensive structural analysis loyal to design-stage conditions was developed. After the constitution of a detailed linear elastic numerical model of the structure, various static analyses were first performed; comparisons with available recorded data at the try-out stage proved the model’s consistency. Then, further insight into the linear range, concerning the modal dynamic behaviour, was investigated, with a reasonable matching with available experimental modal characteristics. Finally, a complete non-linear inelastic analysis was developed, up to detect plastic-collapse features, to assess the safety margin at increasing live loads. This case study shall contribute in setting up a reference scene about the present bridge structural capacity, within the current debate on the destinies of the structure and the screening of possible intervention scenarios.