Author(s)

S.E. Thomasen & C.L. Searls

Abstract

: The San Francisco City Hall suffered damage in the 1989 Loma Prieta earthquake and it was decided to repair and seismically upgrade the structure. The goal of the strengthening was to achieve accepted life-safety standards for both the structural and the non-structural elements and, at the same time, protect historically important elements from future earthquake damage. From the options available to seismically strengthen the City Hall, base isolation was selected. The selection of base isolation greatly reduced the seismic interaction between the base structure and the dome, and reduced the demand for structural strengthening of the dome. As part of this project it was necessary to insure that the dome was in sound condition and that future deterioration would not diminish its capacity to resist earthquakes

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