Sensitivity of seismic fragility of base-isolated bridges to lead rubber bearing modeling technique

Seismic isolation has been demonstrated to be one of the most effective methods developed to protect bridges during earthquakes. One of the significant challenges in examining their effectiveness is how to model them numerically. Lead rubber bearings (LRB) have emerged as a popular solution for damage protection of bridges during major seismic events. Since the seismic response of a base-isolated bridge considerably relies on the adopted analytical modeling method for the bearing element, it is crucial to identify a suitable modeling strategy for LRBs. The goal of this research is to investigate the seismic response sensitivity of isolated bridges using various LRB modeling techniques. Considering two identical reinforced concrete bridges with curved and straight configurations, this study examines the effect of LRB modeling techniques on the nonlinear dynamic response and failure probability of bridges. Three different suites of ground motions such as far-field, near-field with pulse, and near-field with no pulse are considered in this study. Three different LRB techniques available in OpenSees including KikuchiAikenLRB, ElastomericX, and LeadRubberX are used to model the isolation bearings. Bridge-specific fragility curves are generated employing incremental dynamic analysis considering different LRB modeling techniques subjected to each ground motion suite. Analyses results show that the failure probability is significantly sensitive to the LRB modeling scheme as well as the ground motion type. The fragility analysis reveals that the KikuchiAikenLRB model leads to a lower probability of damage followed by ElastomericX, whereas the LeadRubberX demonstrates more conservative results.