Due to the considerable advantages regarding the design, construction time, durability and costs, composite steel-concrete bridges are commonly used in high-speed lines of the European railway network. Generally, the nature of bridge-like civil structures does not allow to build a prototype. Therefore, in case of analyses aiming to remove uncertainties on dynamic effects and interaction phenomena, derivation of fatigue loadings, structural modelling, fatigue life and damage assessment of steel-concrete composite high-speed railway bridges, an appropriate numerical model representing the dynamical state of the construction is needed. This paper covers the derivation of a numerical model of the Sesia Viaduct located on the new Italian high-speed line between Torino and Milano. More specifically, issues related to complex material data, asymmetries in the construction, asymmetries in the supporting condition, and model reduction will be addressed and resolved. Finally, the numerical model has been updated with the use of experimental data acquired by means of Operational Modal Analysis under ambient and train excitation conditions.
