IDENTIFICATION OF TIME-DEPENDENT DYNAMIC CHARACTERISTICS OF STRUCTURES RESPONDING TO STRONG GROUND MOTION

Major changes In the dynamic properties of structures are expected to occur and have been observed from the earthquake records obtained from several instrumented buildings. An appropriate signal processing technique for analyzing both the earthquake records and the building response data should be capable of identifying the time variations in the amplitudes and in the frequency content. The methodology discussed in this paper utilizes the impulse invariant transformation to obtain the discrete time equivalent of a single-degree- of-freedom oscillating system which is used as a second order component in parallel form realizations of earthquake and structural system. The overall system's input-output difference equation is then defined and its time-varying coefficients are identified.