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Response of Base-Isolated Buildings During the 1994 Northridge Earthquake

by Satish Nagarajaiah and Sun Xiahong

Nagarajaiah, Satish, and Sun Xiahong (1995). Response of Base-Isolated Buildings During the 1994 Northridge Earthquake. SMIP95 Seminar on Seismological and Engineering Implications of Recent Strong-Motion Data, p. 41 - 56.

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Abstract

The objectives of this study are (1) to evaluate the seismic performance of base isolated USC hospital building and Fire Command Control building, in Los Angeles, during the 1994 Northridge earthquake, and (2) to evaluate the analysis techniques and design criteria used in base isolated structures. USC hospital base isolated building is a 8 story steel braced frame; the seismic isolation system consists of 68 lead-rubber isolators and 81 elastomeric isolators. Fire Command Control (FCC) base isolated building is a two story steel braced frame with 32 high damping rubber isolators. Both the USC hospital building and Fire Command Control building experienced strong motion during the Northridge earthquake. The approach adopted in this study is (1) system identification, (2) nonlinear analytical modeling, (3) interpretation of structural behavior during the Northridge earthquake, and (4) evaluation of the effectiveness of seismic isolation. It is shown that (1) USC hospital performed well, deamplified the accelerations, and reduced the overall response, (2) FCC building performed to expectations; however, accidental pounding reduced the effectiveness of seismic isolation, and (3) the analysis techniques used in base isolated structures are accurate and can reliably predict the response.