Effect of LRB Constitutive Models on the Seismic Response of an LRB-Isolated Highway Bridge

Seismic isolation devices are widely used to improve the seismic performance of bridges by mitigating the expected damage. Lead rubber bearing (LRB) is a commonly utilized seismic isolation system, and numerous analytical models of LRB have been proposed in the literature. However, each model has its unique benefits and drawbacks. This research aims to evaluate the seismic behavior of a bridge isolated with LRBs using various LRB modeling methods. A three-span curved steel girder bridge with LRB isolation, which underwent a shake table test at the University of Nevada, Reno, is selected as the reference bridge. A numerical model of the reference bridge is first created and validated using OpenSees. Then, four LRB modeling methods, namely ElastomericX, LeadRubberX, KikuchiAikenLRB, and a novel LRB modeling method, are applied to model the isolation bearings. The new LRB model is developed as a part of this study which has been validated against available experimental results. The evaluation of the seismic behavior of the isolated bridges considers the force–deformation relation of the isolators, bearing shear strain, energy dissipation capacity, and pier shear force. 22 far-field ground motions compatible with the bridge site location have been used to compare the performance of the proposed LRB model with existing LRB models. The comparative analysis reveals that the modeling techniques have a significant impact on the seismic assessment of LRB-isolated bridges. Also, the new LRB analytical model can accurately predict the nonlinear behavior of LRB and subsequently make the seismic assessment of LRB-isolated bridges more accurate.