Nonlinear rolling isolation system

Most of the isolation systems are linear system. The isolator has fixed vibration period. When structures with these linear isolators locate near the fault, it may cause resonance and large displacement response. So, nonlinear isolation can avoid this situation. In this study, an eccentric rolling isolator is used, and a parameter alpha (alpha), which is the ratio of the eccentricity of the mass block to the radius of the rolling device, is investigated. If the parameter alpha is not equal to zero, the dynamic response is nonlinear rolling behavior. The equation of motion of the isolation system is derived. The frequency of the isolator increases with the parameter alpha under the same initial displacement. The influence of the parameter to the effect of isolation is scrutinized. Finally, the feasibility of the proposed isolation device is verified numerically. Under El Centro earthquake, which the peak ground acceleration is about 300 gal, the absolute acceleration is reduced to about 50 gal after isolation with alpha equal 0.1. From these numerical results, the frequency of this nonlinear rolling system is varying with the amplitude of vibration. So, this isolation system can not only avoid resonance but also decrease the response of structure well.