SEISMIC ISOLATION OF THE FIRST FEDERAL BUILDING IN SAN FRANCISCO

Seismic retrofitting of existing historic buildings poses many challenges to the structural engineer in integrating structural strengthening schemes within architectural constraints. Seismic isolation in the United States is gaining wide acceptance as an attractive and alternate means to seismically upgrade historic structures without interfering with architecturally significant features. One of the important historic landmark structures currently undergoing such an upgrade is the Ninth Circuit U.S. Court of Appeals building located in San Francisco, which suffered damage during the 1989 Loma Prieta earthquake and was declared an unsafe building for further occupancy. This paper summarizes the comprehensive approach adopted for implementation of the seismic isolation technique for the seismic retrofit of this monumental structure. This historically significant structure is the first Federal Building to be retrofitted using seismic isolation.