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Assessment of Existing Offshore Platforms for In-Place Conditions

Bassamzadeh, Nastaran Sadat | 2009

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 39404 (09)
  4. University: Sharif University of Technology
  5. Department: Civil Engineering
  6. Advisor(s): Golafshani, Ali Akbar
  7. Abstract:
  8. Assessment of existing jacket type offshore platforms in Persian Gulf for life extension is of great importance in the field of offshore platforms in recent years. The main question to answer is whether an existing platform is safe enough to be used beyond the design life. Evaluation of existing jacket type offshore platforms under extreme environmental (wave) loading in Persian Gulf is a part of this major assessment. Two general approaches exist in this context, deterministic and probabilistic assessment. In this thesis, a new probabilistic method (reliability analysis) to assess offshore structures under environmental loading (extreme wave) is introduced. This method is a probability-based format used for performance based design and assessment of structures, which was first introduced for probabilistic seismic demand analysis (PSDA) of buildings. It is based on a technical framework that provides a closed-form analytical expression for the annual probability of exceeding a structural performance level, which is usually defined as specified structural parameters (e.g., strength) reaching a structural limit state (e.g., onset of yield, collapse). The expression for annual probability of exceedance is derived by taking into account the uncertainties in three main elements consisting environmental hazard, structural response (as a function of wave loading) and capacity. Static non-linear system strength analysis (push-over) is the common method to calculate the capacity of the system. In the present study, a more realistic approach used to calculate the system capacity called “Incremental Wave Analysis” (IWA) will be discussed. In the next step, the uncertainty propagation and reliability analyses are evaluated using a relatively new approach by Monte Carlo simulation. Finally, an existing jacket in Persian Gulf is assessed by using this new approach and relevant analysis methods are presented accordingly
  9. Keywords:
  10. Offshore Platforms ; Reliability Analysis ; Monte Carlo Simulation ; Persian Gulf ; Numerical Integration ; Incremental Wave Analysis

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