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Structural Assessment and Rehabilitation of Jacket Platform Structures with Regard to Remaining Life

Rahimzadeh Khoshroo, Mohammad | 2013

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 44137 (09)
  4. University: Sharif University of Technology
  5. Department: Civil Engineering
  6. Advisor(s): Golafshani, Ali Akbar; Tabeshpoor, Mohammad Reza
  7. Abstract:
  8. In this thesis, a novel approach for assessment and rehabilitation of offshore platform structures will be introduced, which is based on the fatigue analysis. Although fatigue is not a limiting criteria for platforms having natural periods bigger than two seconds, some of this platforms may be susceptible to fatigue due to their specific design. In addition, fatigue analysis can be an effective solution in cases like assessing the efficiency of structural control instruments under platform’s operational loads, and in its life. The main merit of this approach is that it can model the exact behavior of various damper devices and show their influence on the fatigue life. In fact, control devices exhibit different efficiencies under different operational loads due to different sea conditions. So, in order to assess the life-time efficiency of a damping system for a specific offshore platform, and under the site-specific conditions, fatigue damage index can be a fitting criterion. Moreover, since implementation of control devices can cause minor fatigue damages in the platform’s details, fatigue analysis can be even more substantial in the design of such devices. In order to improve the dynamic behavior of platform, in this thesis, a novel rotational damper is implemented. Thus, the damper makes use of the torsional behavior of viscoelastic materials. Moreover, due to the nonlinear behavior of the damper and the necessity to appraise the effect of damper parameters on it performance, the time history approach is used in parallel with numerical integration technique for the fatigue assessment in time domain, and the damper’s efficiency in fatigue life extension of the platform is examined in conjunction with the platform’s vibration control. Finally, in order to assess the effectiveness of the damping system, a real platform located in the Persian-Gulf is selected, which has been analyzed and the results are proposed in the text
  9. Keywords:
  10. Offshore Structures ; Fatigue Analysis ; Offshore Platforms ; Vibration Control ; Hybrid Damper ; Template Platforms

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