Influence of Characteristics of Lead Rubber Bearing Isolator on the Seismic Response of a Base-Isolated Building

Abstract

This paper investigates the characteristics of lead rubber bearing (LRB) isolators on the seismic performance of base-isolated buildings, focusing on how variations in LRB characteristics, such as initial stiffness (K1) and yield strength (Fy), relative to the structure weight (W), affect seismic response. The nonlinear time history analysis is conducted on a 5-story building with LRB isolators. The isolator stiffness is varied to represent different states, namely soft, flexible, and hard, in terms of relative stiffness. The performance of these buildings is assessed under near-field earthquakes, measuring story displacements, interstory drift ratios (IDRs), story accelerations, plastic hinge rotations, isolator displacements, isolator hysteresis loops, and energy dissipation. The ratio Fy/W=0.1 exhibits significant reductions in performance metrics compared to a fixed-base building. It achieves a maximum reduction of 46% in base shear, 65% in interstory drift ratio, 66% in story displacement, 58% in top-story acceleration, and 79% in nonlinear plastic rotation. Additionally, it demonstrates the most substantial decrease of 80% in isolator displacement and 57% in energy dissipation compared to other cases from 586.52 mm to 115 mm and 1,295 kN·m to 555 kN·m respectively by varying Fy/W from 0.1 to 0.6. Higher values of Fy/W and K1 increase the building response while reducing isolator displacement and energy dissipation. A softer isolator significantly improves performance across all parameters.