On site assessment of Azzone Visconti bridge in Lecco: Limits and reliability of current techniques

•Structural assessment of historical bridges requires the knowledge of many experts.•Structural assessment is helped by the reconstruction of historical events.•The assessment of a historical bridge requires a very strong coordination.•A limited budget can be instrumental to refine the assessment approach strategy. Ponte Azzone Visconti is a strategic middle age bridge built at north of Milan astride river Adda, along the road towards the centre of Europe passing from the Valtellina, the lordship of Milan and the Serenissima Republic. An on-site assessment of the bridge was carried out starting from the requirement expressed by the municipality of Lecco, consisting in the evaluation of the actual bearing capacity of the infrastructure with reference to the bridge classes defined in the national standards. The investigation used several approaches to quantify the bridge structural safety with reference to the vertical loads due to traffic and accidental seismic events and to highlight any critical issue. The paper is aimed at suggesting the most convenient analysis and maintenance choices, in order to conjugate the very significant historical value of the bridge to a sustainable evolution of its function.