| Summary: | 碩士 === 國立成功大學 === 航空太空工程學系碩博士班 === 93 === Dynamical systems can be characterized by their modal parameters, which include natural frequencies, damping ratios and mode shapes. Identification of system characteristics is usually accomplished using both input and output data from the structural system. It can be shown that the non-stationary input signals modeled as an equivalent state-space model derived from measured input and output data is transformed from the time series model. The structural modal parameters can be estimated accurately using the equivalent state-space model form the time series models. In addition, the natural frequencies, damping ratios and mode shapes of structural system can be evaluated directly by the state system matrix. In many cases, however, only output measurements are possible for structures under ambient conditions. To used the Random Decrement Technique which auto- and cross-random decrement vibration signatures of the response of a linear structure are in the same mathematical form as free vibration of the structure. The objective of this thesis is to develop a modal parameter identification method by using time domain identification techniques with the response randomdec signatures treated as free vibration data. By means of being compared Time Series Method with Ibrahim Time Domain method, we confirm the applicability of the modal parameter identification method proposed through numerical simulation.
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