MINIMUM VARIANCE CONTROL OF BASE-ISOLATED FLOORS

This paper presents a formulation for earthquake-resistant design of hybrid isolation systems for base-isolated floors and sensitive equipment mounted on a main structural system. Hybrid isolation techniques constitute a viable alternative for protection of medical equipment, art objects, and sensitive devices subjected to support excitation. An integrated design procedure for the passive and active components of the isolation system is developed aiming at acceleration reduction under random excitation. The active component provides a resistant scheme to absolute motion by an absolute velocity feedback strategy that is a very convenient scheme for acceleration reduction in isolated structures. Constraints in the deformation capacity of the isolators, as well as constraints in the capacity of the actuators, are considered for the design of an optimal hybrid isolation system. Simple numerical examples are developed to illustrate the design procedure. The superiority of hybrid systems over passive systems in reducing acceleration response is demonstrated.