HYBRID ISOLATION SYSTEMS FOR EQUIPMENT PROTECTION

This paper presents a formulation for earthquake resistant design of o ptimum hybrid isolation systems for sensitive equipment protection. Th e hybrid system under consideration consists of laminated rubber beari ngs, viscodampers and a set of actuators which, grounded on the main s tructural system, deliver forces on the basement of the isolated subst ructure mounted on the main structural system. An integrated design pr ocedure for the passive and active components of the isolation system is developed aiming at acceleration reduction under random excitation. Linear models are used for the isolated structure, the main structura l system and the isolation system. Fractional derivative Maxwell eleme nts are used to model the mechanical behaviour of the viscodampers. Th e active component of the isolation system applies forces proportional to the absolute velocity of the isolated piece of equipment. Constrai nts in the deformation capacity of the isolators as well as constraint s in the capacity of the actuators are considered for the design of an optimal hybrid isolation system. Simple numerical examples are develo ped herein to illustrate the design procedure. The superiority of hybr id systems over passive systems in reducing acceleration response is d emonstrated.