Multi-criteria optimization and seismic performance assessment of carbon FRP-based elastomeric isolator

Elastomeric base isolators minimize the structural damage in moderate seismic events and prevent structural collapse in extreme conditions like earthquakes. They considerably decrease the earthquake force transmitted to the structure by providing a flexible damping mechanism between the substructure and the superstructure, thanks to their very low horizontal-to-vertical stiffness ratio. This paper presents a multi-criteria optimization process for fiber-reinforced elastomeric isolators (FREIs) used in bridges. FREI is made of high damping rubber and carbon fiber reinforced polymer (FRP) composite plates. Here, a numerical material model is proposed for high damping rubber using finite element (FE) simulation to capture its highly nonlinear behavior. After validating this material model with experimental results, the effect of different parameters on the efficiency of the elastomeric bearing will be investigated through a sensitivity analysis performed by proposing regression models. The performance of FREI is optimized by assigning different weights to its operational specifications which are the effective horizontal and vertical stiffnesses and the equivalent viscous damping. Results show that the effective horizontal stiffness and viscous damping are highly dependent on the shear modulus of the elastomer layers. Also, the number of rubber layers and thickness of FRP composite plates have large effects on the vertical stiffness. Finally, an isolated three-span continuous steel girder reinforced concrete pier supported bridge is fitted with the optimized FREI in order to analytically study the performance of the rubber bearing on the seismic behavior of the bridge structure through dynamic time history analyses.