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Parametric Evaluation of the Y- Shaped Bracing Frame and Introducing a New Method for Design

Sedaghati, Parshan | 2012

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 43471 (09)
  4. University: Sharif University of Technology
  5. Department: Civil Engineering
  6. Advisor(s): Mofid, Masoud
  7. Abstract:
  8. This paper investigates the behavior of the Y-shaped bracing system. Because of the special type of eccentricity in this system, the behavior of the frame is strongly dependent on the geometrical changes of the braces. So that even in the elastic region, it shows the geometrically nonlinear behavior. The amount of eccentricity is very effective on the nonlinear behavior of the frame. Also the ratio of cross sections of the bracing members has a very important impact on the expected performance of the frame. The results show that this system tolerates large displacements, and can act like a base isolation system. Firstly, using a two-dimensional accurate modeling related to the geometrical changes and nonlinear behavior of material in OpenSees, the special nonlinear behavior of the system including first and second stages of yielding, and also the buckling behavior of the bracing members are obtained. Anextensiveparametricstudy wasthenperformedon the system, and in addition to determine the important and influential parameters, the optimal ratios of them are obtained for the best performance of the frame. Then by considering the results of the parametric study, for a few types of frames, the required graphs for determining the multilinear curve of the system is presented. These graphs are included dimensionless parameters of force and stiffness that can be used for the other frames with the same properties. At the end, an algorithm for designing the system according to its ductility under desire earthquake is presented; and the accuracy of the proposed design method is demonstrated in a few examples.


  9. Keywords:
  10. Y-Bracing ; Seismic Isolation ; Buckling ; Design ; Bracing ; Geometrically Nonlinear Analysis

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