Identification of modal parameters of structures via time series models
博士 === 國立交通大學 === 土木工程系所 === 97 === Time series models are often employed to establish input-output relationships of linear and nonlinear structure systems from their dynamic responses and input forces, and find many applications in various fields. The main purposes of the dissertation are to propos...
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| Format: | Others |
| Language: | zh-TW |
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2008
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| Online Access: | http://ndltd.ncl.edu.tw/handle/82164383019079699761 |
| Summary: | 博士 === 國立交通大學 === 土木工程系所 === 97 === Time series models are often employed to establish input-output relationships of linear and nonlinear structure systems from their dynamic responses and input forces, and find many applications in various fields. The main purposes of the dissertation are to propose various novel techniques to establish different time series models and to determine structural modal parameters from the established time series models.
The continuous wavelet transform is first applied to establish the ARX model (autoregressive with exogenous input model). The shift property and filtering ability of the continuous wavelet transform enhance the efficiency of the proposed approach in accurately identifying the modal parameters of a structure from its earthquake responses or free vibration responses. The effects of noise and various wavelet functions on determining the modal parameters of structures are also explored in processing the numerically simulated acceleration responses of a six-story shear building subjected to base excitation. The proposed approach is also employed to obtain the modal parameters of a three-story non-symmetric steel frame from its measured acceleration responses in a shaking table test.
The moving least-squares technique with polynomial basis functions or wavelet functions is adopted to establish the TVARX model (time-varying autoregressive with exogenous input model). It is proved that the instantaneous modal parameters of a linear time variant structure can be directly estimated from the coefficient functions of the TVARX model if the TVARX model is established using the displacement responses of the structure. Numerical studies are carried out to investigate the effects of parameters in the proposed approach on accurately determining instantaneous modal parameters. Numerical analyses also demonstrate that the proposed approach is superior to conventional basis expansion techniques in accurately estimating instantaneous modal parameters of a structure. The proposed approach is further applied to process measured data for a frame specimen subjected to a series of base excitations in shaking table tests. The specimen was damaged during testing. The identified instantaneous modal parameters are consistent with observed physical phenomena.
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