SEISMIC ISOLATION DESIGN OF THE SAINT JOHN'S HEALTH CENTER REPLACEMENT PROJECT

摘要

The Saint John's Health Center Replacement Project, located in Santa Monica, California, consists of four separate structures containing a total of approximately 470,000 sf of floor space for hospital and support services. Two of these structures are base isolated. Additionally, the two separate superstructures are supported on a common diaphragm level. Hence, the base isolation system supports a common diaphragm "table-top", which in turn supports two separate superstructures. The main purpose of utilizing this approach was to minimize the relative displacements between the two building superstructures. Both of the building structures are framed with structural steel, utilizing concentric braced frames as the lateral force resisting system. The site is located within 1 km from the Santa Monica fault, and the design ground motion is very severe. A base isolation system has been designed for the facility that will provide essentially elastic building response to the design strong ground motion. The base isolation system consists primarily of lead-rubber bearings, which provide both the lateral stiffness and the damping that characterize the base isolated response of the building. The existing Saint John's Health Center campus was badly damaged in the 1994 Northridge Earthquake, and was shut down for approximately 9 months following the earthquake while the facility underwent repairs. The use of a base isolation system for the replacement Health Center was motivated in part by the desire of the facility to maximize the probability of maintaining the post-earthquake continuity of operations. Design criteria, structural analysis and design methodologies, and construction details are presented and discussed.