Effects of Supplemental Damping and Stiffness in Lead Rubber Bearing Systems on the Seismic Performance of Steel Structures

In this study, the seismic performance of steel structures equipped with lead rubber bearing (LRB) isolation systems was investigated, focusing on the effects of supplemental damping and isolation periods under design‐basis earthquake (DBE) and maximum‐considered earthquake (MCE) hazard levels. Using the endurance time method (ETM), four structural configurations were analyzed: a three‐story low‐rise building and a twelve‐story high‐rise building, each with regular and irregular geometries. Structural irregularities, introduced through variations in mass and stiffness, significantly influence the efficiency of seismic isolation. The study evaluates supplemental damping ratios of 0%, 5%, 10%, and 15%, along with isolation periods of 2.5, 3.5, and 4.5 s. The results indicate that higher damping levels substantially improve seismic performance. Under the MCE hazard levels, a 15% damping ratio reduces the peak interstory drift by up to 92.2% and the absolute floor acceleration by 90.6% in low‐rise irregular buildings. At the DBE hazard level, reductions reached 76.5% and 73.8%, respectively. Extending the isolation period further enhances performance, particularly in low‐rise structures. For irregular high‐rise buildings, supplemental damping proved more effective than increasing the isolation period, achieving up to a 68% reduction in peak drift and 65% in acceleration under MCE hazard levels. The findings confirm that seismic isolation performs best in regular structures where uniform mass and stiffness distributions facilitate consistent energy dissipation. These results emphasize the need to optimize supplemental damping and isolation periods in LRB systems to enhance seismic resilience while maintaining economic feasibility and highlight the importance of tailored seismic isolation strategies for irregular structures.