Seismic isolation analysis of a roller isolation system
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Seismic isolation has been widely accepted in earthquake-prone regions of the world to protect structures from strong ground motions. Many different isolation devices have been studied and applied in practice. In this study, a new type of seismic isolation device, a roller isolation bearing, is introduced. The roller isolation bearing realizes the isolation effect by rolling and through several geometric configurations. Different configurations can result in a variety of dynamic characteristics, which can be linear or nonlinear. Three types of roller isolation bearings are modeled and analyzed. To control the bearing displacement, three bearings are studied in combination with viscous dampers and friction dampers. The dynamic characteristics and seismic performance of the roller isolation systems combined with damping devices are investigated by applying harmonic excitations and a large number of typical earthquake records. The results show that the roller isolation system combined with friction dampers can effectively reduce the force transmission between the structure and the ground. Further comparison between the roller isolation systems and some typical bilinear models verifies that the proposed systems have a strong ability to control structural base shear and bearing displacement. The comparison is implemented by following the evaluation procedure for simplified design used in the design of seismic isolation systems. The properties of the peak responses of the roller isolation system combined with friction dampers are studied, and the response spectra are introduced based on the design parameters of the roller isolation system. A highly efficient computational procedure is developed to analyze the seismic response of a MDOF structure isolated by the roller isolation system combined with friction dampers. The case study shows that the roller isolation system can significantly reduce the story shear and drift, limiting the relatively large displacement at the bearing level. The roller isolation bearing is tested using a 60 ft long bridge model and two shake tables. The test results show that the roller isolation bearing effectively reduces the force transmitted to the bridge deck. The experimental data show good agreement with the numerical results.