Prediction of Observed Response of Base-Isolated Structure

The recorded response of a base-isolated structure excited by the 1994 Northridge earthquake is utilized to validate existing computational methodologies. The isolated structure is located at 1955 1/2 Purdue Avenue in Los Angeles, Calif., and is a three-story braced-steel-frame residential building supported on helical steel springs and viscoelastic-fluid dampers. The procedure developed during the construction of the building by one of the writers to model the isolation system using generalized-derivative constitutive models is utilized to predict the response of the structure. The predicted response is in good agreement with recorded data at the first and third floors of the base-isolated building. Subsequently, it is shown that the peak values of the response can be satisfactorily predicted using an approximate procedure based on modal analysis. The importance of the isolation system is discussed.