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Development of Inverse Vibration Technique for Damage Detection of Offshore Jacket-type Platforms

Haeri, Mohammad Hassan | 2017

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  1. Type of Document: Ph.D. Dissertation
  2. Language: Farsi
  3. Document No: 49942 (09)
  4. University: Sharif University of Technology
  5. Department: Civil Engineering
  6. Advisor(s): Golafshani, Ali akbar; Mohtasham Dolatshahi, Kiarash
  7. Abstract:
  8. In this dissertation a new approach is introduced for damage detection in offshore jacket platforms. The procedure uses the measured ambient vibration responses and the corresponding readable natural frequencies and mode shapes of the structural systems. Since offshore platforms are composed of heavy topsides supported by jacket structures, participation of the first mode is dominant in each direction in the response of the structure under field excitations. Moreover, ambient vibrations such as wave loads and boat impacts only excite the first modes of the structure. Therefore, it is difficult to find higher modes and the pertinent frequencies by use of accelerometers data. The introduced innovative method in this research uses the first few fundamental frequencies and mode shapes of the structure. The algorithm employs the inverse vibration technique to develop a simple two and three dimensional reference model for health monitoring of the structures. To show the efficiency of the proposed procedure, case studies are carried out on the models of two jacket-type platforms in the Persian Gulf region. Finally, uncertainty analysis is performed, due to the existence of noise and uncertainties in input data collected by accelerometers. Results indicate that the proposed method has the ability to detect the induced damages by a high level of accuracy considering probable sources of error
  9. Keywords:
  10. Irregular Wave ; Structural Health Monitoring ; Damage Detection ; Sensors ; Reference Theory ; Inverse Vibration Problem ; Dynamic Response ; Offshore Platforms

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