Large-Scale Hybird Semi-Active / Passive Base Isolation

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The objective of this research project is to provide experimental validation of a hybrid semi-active / passive base isolation system combining low-damping rubber isolators and semi-active control elements which exhibit variable stiffness and damping properties. This research involves control theory development, device development, small-scale verification tests, and large scale tests. The large-scale vibration control experiments will be carried out in collaboration with the Japanese National research Institute for Earth Science and Disaster Prevention (NIED). These experiments will be designed to validate the control system, which is simple to implement, robust to uncertainties in the structural model, requires very little external power, and has guaranteed closed loop stability.Members with adjustable stiffness and damping can be used to modify the dynamics of a base isolated structure. Optimal control methods, and control rules based on Lyapunov's direct method, will be investigated. The objective of the control will be to reduce deformation of the base isolation system without increasing absolute accelerations of the isolated mass. The results of this research will provide designers with the knowledge required to combine variable property materials (such as ER materials) with passive base isolation and simple feedback control to limit isolator deflections.This is a project under NSF 98-36, "US-Japan Cooperative Research in Urban Disaster Mitigation".