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Modeling of Local Joint Flexibility in Opensees Software by a New Element Added to the Library of Software

kia, Mehdi | 2010

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 40349 (09)
  4. University: Sharif University of Technology
  5. Department: Civil Engineering
  6. Advisor(s): golafshani, Ali akbar
  7. Abstract:
  8. Jacket type offshore platforms are classified as expensive and also strategic structures, and the cost of their maintanace is considerable. Therefore, any inspection and retrofit plans for life extension of the existing structures is economically and logically preferable rather than making decision for design and construction of new structures. The first stage of assessment plan is monitoring the performance of structure during critical loadings for which the structure is designed. One of the critical loads that should be considered in assessment of jacket structures is seismic loading. Due to dynamic nature of the applied loads in seismic assessment of jacket structures the accuracy of technical software for performing nonlinear dynamic analysis is an important consideration. One of the most powerful and prevalent technical software for this purpose is OpenSees. In this software, jacket structure will be modeled as a set of beam-column elements with tubular sections that rigidly connected to each other. Conducted investigation on rigid connection revealed that owing to flexibility of chord’s wall the validity of rigid connection assumption is questionable and this assumption can lead to considerable difference between analytical and prototype model results in some cases. In this study it is assumed that the interaction of braces in vicinity of joint connection is negligible and based on this assumption a uniaxial element which is named “Elastic Tubular Joint” is developed and added to OpenSees’ library in order to consider the local flexibility of tubular joint in analytical model of structure more accurately and also in a simple manner. Moreover, stiffness matrix of this element is developed based on shelling behavior of chord member. Finally, the accuracy of the new proposed element performance for linear behavior was verified by comparing its results with three levels of analyses (i.e., in connection level, structural level and with an experimental model)
  9. Keywords:
  10. Jacket Platform ; Local Flexibility ; OpenSees Software

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