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Structural Health Monitoring of Offshore Jacket Platforms by Inverse Vibration Problem

Lotfi, Alireza | 2015

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 46940 (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 thesis selection criteria are present for types, numbers and locations of sensors for structural health monitoring of offshore jacket platform in the Persian Gulf. The selection criteria are chosen by studying structural health monitoring of various structures in civil and aerospace industries. Knowing the types of sensors that can be used, a new approach of inverse vibration problem is introduced for structural health monitoring of offshore jacket platforms. In the previous studies, significant numbers of frequencies and mode shapes are usually used to detect damages by updating components of stiffness matrix. Considering the fact that offshore platforms are composed of a heavy topside that is supported by a truss structure, the participation of the first mode is much greater than the others. Moreover, ambient excitations such as wave loads only excite the first mode and barely the second mode of the structure. Consequently, it is difficult to read higher modes and frequencies of the structure by ambient excitations making use of accelerometers. In this study, by using the lower natural modes a new approach is proposed for health monitoring of 2-D and 3-D offshore structures. To show the efficacy of the proposed procedure an example is presented for a real platform in the Persian Gulf, namely SPD2, and the presented formulations are applied and verified for 2-D and 3-D models. To account for the error of the obtained data by accelerometers, a probability sensitivity analysis is conducted. Results indicate that the proposed method has the ability to detect the induced damages by a great level of accuracy considering probable errors
  9. Keywords:
  10. Structural Health Monitoring ; Sensitivity Analysis ; Offshore Jacket Platform ; Sensors ; Inverse Vibration Problem

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