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Damage Detection of Offshore Jacket Platforms Using Fitting Vibration Data

Bahador, Mohammad Mahdi | 2013

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 44193 (09)
  4. University: Sharif University of Technology
  5. Department: Civil Engineering
  6. Advisor(s): Ali Akbar, Golafshani
  7. Abstract:
  8. In the regard of structural health monitoring the identification of the structural modal parameters is essential. Since the different sources (wind, waves, Devices …) induce vibration on an offshore platform, it is impossible to determine the portion of each source in vibration. Thus the methods that analyze vibrations needless of input measurements are more efficient. These methods apply the ambient factors and obtain the modal properties from the structural response. This procedure has no unwanted effect on the serviceability of structure and by placement of sensors on the platform; one can monitor the structural health.
    In the present work a two dimensional jacket offshore platform is modeled by finite element software. First, the platform’s floor is assumed to be rigid and the effects of soil, pile and flexibility of connections are not taken into account. Then these effects are considered to obtain more accurate results. In both cases the data is collected from the platform by three different sensor placement cases and by the Enhanced Frequency Domain Decomposition, the modal properties are assessed and compared in presence of ambient noise. Afterwards, damage in form of reduction of modulus of elasticity with different ratios is imposed within a structural member. The resulting modal properties and their variation with a progressive damage case are compared with intact structure. Finally the efficiency of the Frequency Domain Decomposition method in identification of exact modal properties is examined by imposing an abrupt damage. The comparison of results show sufficient accuracy of the Frequency Domain Decomposition in modal identification and this method is recommended for long term structural health monitoring of actual platforms
  9. Keywords:
  10. Damage Identification ; Structural Health Monitoring ; Template Platforms ; Frequency Domain Decomposition ; Offshore Jacket Platform

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