Experimental and Numerical Study on Hysteretic Behavior of Laminated Rubber Bearing Under Quasi-Static Loading and Its Performance on Secondary System

Characterization of the laminated rubber bearing is done experimentally. Linear and nonlinear parameters are identified from the numerical method. The hysteretic behavior of the laminated rubber bearing is determined by cyclic shear and vertical stiffness test. Result shows that the shear test with increased axial loads resulted in a marginal reduction up to 7% in shear stiffness of the laminated rubber bearing. The bearing is modeled with equivalent linearization and nonlinear methods on secondary structure with the properties obtained from the test. The analysis results show that the response of base-isolated secondary structure is significantly affected by hysteretic properties of the bearing. Though actual prediction of the response can be obtained considering the area under the hysteretic loop, equivalent linearization can be done for narrowly damped laminated rubber bearings for conservative results. Numerical study carried out on five-story moment-resisting steel frame. The isolated single degree of freedom (SDOF) secondary system is kept on different floors of the primary system to analyze the acceleration, displacement, and shear forces. In a result, laminated bearing well intercepted the earthquake excitations having predominant frequencies less than 2 Hz from its base. For earthquake excitations, the response has been reduced up to 51%. But the sinusoidal excitation with frequency 3 Hz was unable to perform satisfactorily and amplified the acceleration response instead of reduction. Based on the numerical and experimental study, it can be concluded that the laminated rubber bearings are effective for lower frequency excitations.