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Developing the Dynamic Increasing Amplitude and Period (DIAP) Method and Investigation of its Efficiency in Ultimate Capacity Assessment of Jacket Offshore Platforms

Imani, Hassan | 2022

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  1. Type of Document: Ph.D. Dissertation
  2. Language: Farsi
  3. Document No: 55695 (08)
  4. University: Sharif University of Technology
  5. Department: Mechanical Engineering
  6. Advisor(s): Abbaspour Tehranifard, Majid; Tabeshpour, Mohammad Reza; Karimirad, Majid
  7. Abstract:
  8. Dynamic increasing amplitude and period (DIAP) [1] is a time-domain analysis methodology developed based on endurance time (ET) analysis method [2], which can be used to evaluate the response of marine structures when encounters a continuous loading, such as storm conditions. In this method, instead of using separate records with different intensities, a single loading record with an increasing intensity over time is used for structural analysis. The ability to enter spectral concepts, considering the effects of waves with different frequencies and amplitudes, taking into account the effects of randomness of waves and the possibility of short duration analysis are some of the specific features of this method. In this research, a generic time-history-based computational scheme, called dynamic increasing wind and wave (DIWWA), up on DIAP method is developed, validated and used to assess the structural performance of an OWT under combined wind and wave loadings. The proposed method is a dynamic analysis technique that provides the ability to simulate the dependence between intensity and frequency content of combined loading during the passage of a storm through a single continuous time-history analysis. To establish this, while describing the method of generating the increasing loading records corresponding to the metocean conditions of the design site, the behavior of a jacket supported offshore wind turbine is investigated using a coupled and decoupled approach of the proposed method. Following this step, the time-history and statistical results from the developed method and the common practice individually performed time-history analysis are compared and the performance and applicability of the proposed method is investigated. The results showed that the maximum discrepancy in the combined loading scenario is very low at the hub height, say around 1% to 3%, that increases to 7% at the transition piece (deck) elevation. Therefore, it can be concluded that DIWWA method provides the basis for a continuous and combined loading scenarios to very good and reliable extent; and by further development it can be used for real storm-like evolutionary conditions, which is currently not available in the common practice software.
  9. Keywords:
  10. Offshore Platforms ; Offshore Wind Turbine ; Jacket-type Offshore Platforms ; Dynamic Increasing Amplitude and Period (DIAP) ; Bottom Effects ; Dynamic Increasing Wind and Wave Analysis (DIWWA) ; Individually Performed Time History Analysis (ITHA)

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