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Modeling of Dynamic Behavior of Fixed Offshore Platforms and their Performance Improvement by Endurance time Method

Dastan Diznab, Mohammad Ali | 2015

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  1. Type of Document: Ph.D. Dissertation
  2. Language: Farsi
  3. Document No: 47926 (08)
  4. University: Sharif University of Technology
  5. Department: Mechanical Engineering
  6. Advisor(s): Seif, Mohammad Saeed; Mehdigholi, Hamid; Tabeshpour, Mohammad Reza
  7. Abstract:
  8. In this thesis, multi-degree-of-freedom and finite element methods are utilized to simulate the dynamic behavior of fixed offshore structures under the wave and the earthquake excitations. In the field of seismic loading, seismic response of the platform is determined with the response spectrum analysis (RSA), time history analysis (THA) and endurance time (ET) methods. The accuracy and the computational cost of the ET method are compared with the RSA and THA methods. The results indicate that despite the RSA method, the ET method can estimate the nonlinear behavior of these types of structures. Moreover, in comparison with the THA method, the computational burden decreases to about 5% while the maximum responses are predicted with acceptable accuracy. In the field of extreme wave loading, modified endurance wave analysis (MEWA) and wave endurance time (WET) methods are introduced for assessment of offshore structures under various sea state conditions. MEWA is an applicable method with optimal time duration that considers the stochastic response of offshore structures. Steps of this method are described based on the linear random wave, the NewWave and the constrained NewWave methods. The application of this method is considered through the multi-degree-of-freedom (MDOF) model of a real jacket platform located in the Persian Gulf. WET is a novel dynamic approach that assess the structural response in lower computational burden and lower accuracy level in comparison with the MEWA method. Application of this method is also studied through the MDOF and finite element models of jacket platforms. The results indicate that both methods can be used as reliable and computationally attractive methods
  9. Keywords:
  10. Endurance Time Method ; Jacket Platform ; Performance Based Design ; Modified Endurance Wave Analysis ; Wave Endurance Time ; Template Platforms ; Dynamic Behavior

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