Supplemental elastic stiffness to reduce isolator displacements for seismic-isolated bridges in near-fault zones

Performance of seismic‐isolated bridges with and without elastic‐gap devices in near‐fault zones

“…Earlier studies [8] on the performance of SIBs in NF zones revealed that under the effect of large magnitude NF earthquakes using supplemental elastic devices such as elastomeric bearings reduces the displacement of the isolators to manageable ranges while keeping the substructure forces at reasonable levels. However, such devices are found to produce large substructure forces for SIBs subjected to small-to-moderate magnitude (SDL) NF ground motions while providing only a modest reduction in the isolator displacements.…”

“…This is anticipated to result in smaller forces transferred to the substructures compared with those of the same SIB equipped with supplemental elastic devices. However, under large magnitude NF earthquakes, the isolator displacements are expected to be quite large [8]. Thus, under the effect of such earthquakes, the gap of the EGDs is closed and the elastomeric bearings are engaged in resisting the movement of the SIB superstructure.…”

“…However, passive damping devices and restrainers are technologies, available to the engineer to use for limiting displacements to manageable levels based on considerations of performance, longevity and cost. Practical solutions such as supplemental elastic devices have been proposed in the past [8] to reduce the isolator displacements for SIBs in NF zones to reasonable levels. However, implementation of such devices is found to produce relatively larger substructure forces with only a limited reduction in isolator displacements for SIBs subjected to small-to-moderate magnitude or service design level (SDL) NF ground motions.…”

“…For small-to-moderate magnitude NF earthquakes where the isolator displacements are within practical ranges [8], the gap of the EGDs is designed to be larger than the displacement of the isolators. Accordingly, under the effect of such earthquakes, the gap of the EGDs is not closed and the elastomeric bearings are not engaged in resisting the movement of the SIB superstructure.…”

“…However, the analytical model presented below [21] is used in this study as it offers several advantages over the other models as described elsewhere [8]:…”