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Modal Identification of Non-classically Damped Linear Systems Using Wavelet Transform

Kamali-Asl, Arash | 2014

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 47091 (09)
  4. University: Sharif University of Technology
  5. Department: Civil Engineering
  6. Advisor(s): Ahmadizadeh, Mahdi
  7. Abstract:
  8. Application of convolution-based transforms such as Fourier transform and wavelet transform are among the widely-used approaches in structural identification problems. These methods, however, are mostly based on a classical damping model for the structures. Hence, such methods cannot be used to accurately identify the modal properties of non-classically damped systems, such as structures equipped with energy dissipated devices, base isolated and multi-segment structures. In this study, complex-valued wavelet transform is used to identify the dynamic properties of structures with arbitrary damping models. This method is known to be able to identify the modal properties of highly damped structures and structures with closely spaced modes. The identified properties in this study include the natural frequencies, modal damping ratios and complex-valued mode shapes, which are then used to simulate the dynamic response of structures with previously-known dynamic properties, providing a means of comparing the obtained response with the exact values. The identified properties and simulated responses are then compared to those obtained assuming a classical damping model (using real-valued wavelet transform) to demonstrate the effectiveness of the proposed approach. These comparisons show that in addition to non-classically damped structures, the classical damping assumption is somewhat inadequate for many civil engineering structures, even those for which classical damping assumption is usually considered valid
  9. Keywords:
  10. Time-Frequency Analysis ; Wavelet Transform ; Modal Identification ; Complex-Valued Mode Shapes ; Output-Only Identification

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