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A New Practical Approach for Nonlinear Static Analysis of Jacket Type Offshore Platforms With Special Attention To Pile-Soil-Structure Interaction

Tavallaie, Alireza | 2011

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 41223 (09)
  4. University: Sharif University of Technology
  5. Department: Civil Engineering
  6. Advisor(s): Golafshani, Ali Akbar
  7. Abstract:
  8. One of the most important elements of performance-based seismic engineering elements is precision in determination of seismic displacement demand evaluation. Although seismic demands which are estimated by utilizing non-linear dynamic analysis are most effective, but with regards to inherent complexities of these methods and demands for time-consuming calculations , non-¬linear static methods seems to be an appropriate representative and is recently considered by engineers. In countries with oil resources including Iran, offshore jacket platforms are among outstanding structures being considered. Inasmuch as high design and execution expenses of these structures and also important role of these structures on the development of country, appropriate utilization and optimization of these structures in their design life period and after that seems to be of significant importance. In this dissertation, assessment of non-linear static methods for offshore jackets and comparison of their results with responses of non-linear dynamic analysis are studied. Before studying this type of structure, brace-framed and moment-framed structures are considered. Modal pushover and adaptive modal combination are considered specifically in this project. Engineering demand parameters which are considered in this project include displacements and story drifts. Responses which are extracted from moment-framed structures are fully acceptable and correspond to the non-linear dynamic analysis results. In brace-framed structures, displacements in upper stories are more and in lower stories are less than estimated non-linear dynamic analysis, but regarding to story drifts, the results do not match thoroughly. In evaluation of offshore jackets, CMS spectrum is utilized, which is suitable for southern Pars area, rather than aforementioned methods. Furthermore, seismic conditions and soil properties of the area are considered here. The outcome of CMS spectrum is appropriate and completely corresponds to dynamic analysis. By using spectrum in analysis of these structures, it would be possible to avoid sophisticated and time-consuming analysis, which is performed by means of records, and approach acceptable and precise responses of the structure
  9. Keywords:
  10. Nonlinear Static Analysis ; Offshore Platforms ; Convection ; Modal Pushover ; Drift ; Conditional Mean Spectrum ; Adaptive Modal Combination

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