Seismic performance assessment and design procedure of base-isolated bridges with lead-rubber-bearing and negative stiffness springs (LRB-NS)

Abstract

This study proposed a straightforward and simplified design procedure for the base-isolated highway bridges with LRB and negative stiffness springs (LRB-NS) device. Compared with the traditional LRB-isolated system, the proposed LRB-NS device contains dual-functionality: (a) alleviate the nonlinearity and damage in piers during slight-to-moderate earthquakes; (b) control the excessive bearing deformation and prevent failure during catastrophic excitations. Therefore, this device effectively improves the post-earthquake function and seismic resilience of bridge systems, and facilitate the rescue operations, since bridge can allow the passage of urgent vehicles with minimal repair. With incremental dynamic analysis (IDA) accounting for the record-to-record variability, the LRB-NS device is shown with dual-functionality as designed and better seismic performance than LRB, subjected to all of far-field (FF), near-fault no-pulse (NFNP), and near-fault pulse-type (NFPT) motions. Additionally, the influence of three kernel parameters, i.e., target period ratio sy_LRB-NS, initial spring length l, and critical deformation ucr, is also investigated in detail, concerning both the structural properties and seismic responses. The results show that increasing sy_LRB-NS and l both benefits the dual-functionality of LRB-NS, but the efficiency reduces with the increase of these design values. While greater ucr significantly reduces column nonlinearity, the bearing deformation is increased as a result, and thus careful tradeoff should be made during practical design.