Safety assessment performed with reference to a relevant case of historical reinforced concrete arch bridge is here discussed. The case study corresponds to the Italian bridge located at Brivio, on the Adda River, completed in 1916. Experimental testing has been performed on the bridge, providing all the required information for the identification of the dynamic behaviour. The seismic vulnerability has been evaluated with both response spectrum modal analyses and non linear static (push-over) analyses. The structural analyses have allowed to interpret the dynamic structural behaviour of the bridge