Base-isolated FCC building: Impact response in Northridge earthquake

The base-isolated Fire Command and Control (FCC) building in Los Angeles experienced strong motion during the 1994 Northridge earthquake. The California Strong Motion Instrumentation Program has instrumented the building and recorded the data during the Northridge earthquake; these data are available for performance evaluation. Impact was observed in the base-isolated FCC building during the Northridge earthquake. The objective of this study is to evaluate the seismic performance of the base-isolated FCC building during the 1994 Northridge earthquake and the effect of impact. New analytical modeling techniques are developed to analyze the base-isolated FCC building with impact and are verified using system identification. The response computed, using the developed analytical modeling techniques, is verified using recorded data. The response with and without impact is presented. The effects of impact on the structural response are evaluated. The seismic performance evaluations, comparing the response of the base-isolated building with the response if the building were fixed base, are presented. It is shown that the seismic performance of the FCC building in the Northridge earthquake was satisfactory, except for increased shear and drift due to impact. Impact should be avoided in base-isolated structures as it can cause damage.