In this paper, the efficiency of providing supplemental elastic stiffness to seismic-isolated bridges (SIBs) for reducing the isolator displacements while keeping the substructure forces in reasonable ranges is investigated. Conventional supplemental elastic devices (SEDs) such as elastomeric bearings placed in parallel with seismic isolators between the superstructure and substructures are used for this purpose. A parametric study, involving more than 400 nonlinear time history (NLTH) analyses of realistic and simplified structural models of typical SIBs are conducted using simulated and actual NF ground motions to investigate the applicability of the proposed solution. It is found that providing SEDs is beneficial in reducing the isolator forces to manageable ranges for SIBs subjected to NF ground motions with moderate to large magnitudes regardless of the distance from the fault. It is also found that the stiffness of the SED may be chosen in relation to the velocity pulse period (or magnitude) of the NF ground motion to minimize the isolator displacements by avoiding resonant response. Further analyses conducted using a realistic structural model of an existing bridge and five NF earthquakes with moderate to large magnitudes confirmed that SEDs may be used to reduce the displacement of the isolators while keeping the substructure base shear forces in reasonable ranges for SIBs located in NF zones. (c) 2006 Elsevier Ltd. All rights reserved.