Isolated Layer Displacement Spectrum Of Parallel Isolation Structure Based On Severest Ground Motions

Parallel isolation is a kind of isolation technology with the rubber bearings and sliding isolation bearings working together. On rational parameter, it takes full advantages of the two traditional base-isolation systems. This paper researches the isolated layer displacement response spectrum which is helpful for parallel isolation structure design.Three simplified models are compared, the results indicate that the 2-mass model has higher analysis precision than single-mass model. Then the seismic response characteristics of parallel isolation structure are studied, and the applicability of the severest ground motions for parallel isolation structure is verified.Main parameters for isolated layer displacement are extracted from the differential equations of the 2-mass model. They are equivalent damping ratioξeq, the ratio of yielding stiffness and weightÏ„, and yielding shear coefficientη. Mass ratio of superstructure and isolated layer has little influence for isolated layer displacement. Main parameters are analyzed based on the severest ground motions, and the analysis instates that the isolated layer displacement decreases withξ_eq andηincrease, so does it forÏ„in middle- period and long-period structure, while in short-period structure,Ï„has little influence for isolated layer displacement. Then the optimal parameters are given.Parallel isolation structure is divided into short-period structure, middle- period structure and long-period structure and its isolated layer displacement spectrums on the severest ground motions are gained when damping ratio equals to 0.05. Considered variation damping ratio, the adjusting formulas of isolated layer displacement spectrums are put forth for otherξ_eq which is in 0.05⁰.20, and its feasibility is verified by error analysis. So, the isolated layer displacement can be estimated easily with looking up table and adjusting formulas.