Effectiveness of commercial oil pressure seismic devices for bridges

In bridge design it is often necessary to restrain/control the longitudinal motions of the bridge decks in order to optimize the structural dynamic behavior under seismic loads. However, the actual widespread use of pre-cast concrete elements in the construction of bridge decks, makes it particularly difficult, in multiple-span bridges, to restrain the motion of the deck without connecting all the decks to the bridge piers. A viable solution that allows to restrain the decks without connecting them to the piers is the one with all the decks rigidly connected to each other by a continuous cast-in place slab and specific connecting devices, in order to obtain a rigid body deck which sits through rollers on the piers (intermediate restraints) and is then restrained only at the abutments by special mechanical devices (end restraints). This paper compares the effectiveness of different mechanical devices which can be used as end restraints to mitigate the seismic dynamic effects upon bridges. The results obtained show that the oil pressure devices limiting the forces transmitted to the deck by the abutments give the best performances in terms of both forces imposed on the structure and devices deformation.