Identification of Linear Structures from Earthquake Records

Abstract

Records of the response to strong ground shaking provide the best source of information on the behavior of large structures during potentially damaging excitations. Since the dynamic properties of many structures are markedly different during response to strong ground motion than in small amplitude ambient and forced vibration tests, it is important to extract as much information as possible from the strong motion data. Limitations in analyses using trial-and-error adjustment of the parameters of a synthesized model, and similar limitations in the use of typical transfer function approaches in the frequency domain, have recently led to the development of systematic techniques of structural identification.[1] Two such techniques for determining linear models of structures from their recorded earthquake excitation and response are described herein, together with the results of their application to the earthquake response of some multi-story buildings. [2,3] One approach is based upon achieving a best match of the time histories of the calculated and recorded responses, while the other is a frequency domain method which matches the Fourier transforms of the calculated and recorded acceleration responses. It is possible either to determine a single linear model appropriate for the entire response, or, by considering segments of the records, to trace the changes of the effective linear parameters with a series of models which approximate the non-linear and time-varying behavior of the buildings.

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