Abstract—The seismic response of bridges seismically isolated by lead-rubber bearings (LRB) to earthquake excitations of different magnitudes is presented in this thesis. The force-deformation behavior of LRB is considered as bilinear. The specific purpose of the study is to assess the effect of seismic isolation on the peak response of bridges subjected to different base accelerations ranging from 0.05g to 0.5g in the horizontal direction transversal to the bridge axis. Thus a certain level of efficiency can be shown in respect of the particular bearing modification. Furthermore, the effect of superstructure stiffness (i.e. pier stiffness, pier layout) on the isolator efficiency is investigated in depth. The seismic response in the finite element model of the continuous span isolated bridges is obtained by solving the governing equations of motion in the incremental form using an iterative stepby-step method. To study the effectiveness of LRB, the seismic response of isola...