A large number of existing bridges in Italy were built in the second half of the 20th century, mainly between 1955 and 1975. Since a large part of the Italian territory was not seismically classified until 2003, most of these structures were designed without considering the effects of earthquake excitations, especially in regions with low hazard. Therefore, several in-service bridges can be presently affected by devices (e.g. load bearings or shear keys) whose resistance and displacement capacity may not be adequate to current standards provisions.In this study, the seismic behaviour of a case-study post-tensioned concrete bridge located in Trieste and built in 1985 is numerically analysed. The structure is 440 m long and composed by nine spans (inner spans of 55 m, and end spans of 27.5 m). Globally, the bridge deck is a curved continuous box girder on multiple supports, built with precast segments using the balance cantilever construction method. The deck is then divided into two parts, connected by a hinged joint in the middle of the central span, obtained with three shear keys and originally designed to allow thermal expansion only.  Most importantly, the mid-span hinge, the end joints and the bearing devices were designed without considering the effects of seismic action. Presently, their displacement capacity could be consequently inadequate to avoid pounding between structural parts, or even loss of support. In order to investigate the actual performance of these devices and joints, the case-study bridge is analysed in this paper by means of non-linear dynamic time history simulations. Displacements over time are obtained for a set of configurations of technical interest, and compared to the capacity of the bridge devices. Parametric results are then critically discussed.