SYSTEMS OF ASEISMIC BASE ISOLATION: OPTIMIZATION ASPECTS.

A new trend for earthquake resistant structures, developed in the last few years, is the base isolation system. In this technique an attempt is made to uncouple a building from the damaging horizontal components of an earthquake by means of laminated rubber bearings and energy-absorption devices. The laminated rubber bearings provide an increased horizontal flexibility, thus preventing or reducing the transmission of horizontal accelerations into the structure. This advantage is accomplished at the expense of large 'rigid body' displacements of the structure with respect to the ground. In this paper the optimum design of four types of base isolation systems is presented. The optimum design is defined as the selection of the characteristics of the isolation system which render the force imparted to the structure a minimum, subject to suitable constraints on the displacements of the structure and on the control variables.