One of important basics of seismic design in bridges is the conncetion of the superstructure to the substructure which because of the convinent use of elastomeric bearings in Iran and other parts of the world, this study focus on this type of conncetion.
Elastomeric bearing which may be included natural ruber (isoperan) or artificial ruber (neoperan) in it used as a mean to reduce the earthquake force and better distribution of lateral forces in supports. This kind of support could be used as base isolation mean which the flexibility of this support reduce the lateral stiffness of the bridge and in the case of seismic excitations it increase the superstructure displacemet, however, it made the internal forces less. Elastomeric bearing maintain the superstructure displacement due to the service loads at an allowable limit and also provide a controlled displacement of it due to the seismic excitation. Furthermore with use of stop blocks the longtitudinal movements of this supports could be stopped. Both of these options have either positive or negative points.
In this study two bridges modeled which concluded 4 thirty meter spans and 6 thirty meters spans, these models shows in bridges with different height of piers these two option could be used subcutaneously to reach an optimum seismic design for them.