SEISMIC RESPONSES OF SECONDARY SYSTEMS IN BASE-ISOLATED STRUCTURES

This paper presents the results of a series of numerical simulation studies on seismic responses of secondary systems in base-isolated structures including equipment-structure interactions. A three-storey building is used as the primary structure, while the equipment is modelled as a single-degree-of-freedom linear system. A number of base isolation systems such as the Laminated Rubber Bearing, the Pure Friction, the Resilient-Friction, and the Electricite de France system are considered. Several earthquake records including the NOOW component of El Centro 1940, the S16E components of Pacoima Dam 1971, and the N9OW component of Mexico City 1985 earthquakes are used as ground accelerations. Acceleration and deflection response spectra of the secondary system under different conditions are evaluated and the effects of equipment - structure interactions are studied. It is shown that the use of base isolation provides considerable protection for structural contents. However, peak responses of the secondary systems vary substantially depending on the base isolation system used. Among the base isolation systems considered, the Laminated Rubber Bearing system appears to be remarkably effective in reducing peak responses of secondary systems under a variety of conditions.