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Effects of Foundation Uplift on Seismic Performance of 2D Frames Placed on Flexible Foundation

Salehi Najafabadi, Mohammad | 2013

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 45209 (09)
  4. University: Sharif University of Technology
  5. Department: Civil Engineering
  6. Advisor(s): Ghannad, Mohammad Ali
  7. Abstract:
  8. In conventional method of modeling and design of structures it is assumed that structures are fixedly supported, however, this assumption is generally far from reality; because, not only the majority of buildings’ bases are not stiff enough to suppose them rigid, but also if their foundations are shallow there exist no piles underneath them, they may separate from their bases – the event which is called foundation uplift. Although according to past studies permission of foundation uplift as well as incorporation of base flexibility may markedly affect any structure’s dynamic response, is spite of about half a century which has elapsed since the beginning of these studies, it seems that still no comprehensive research has been conducted so as to inquire into this phenomenon’s effects on seismic responses of frames. Given the foregoing, this study’s major goal is examination of foundation uplift’s influences on 2D frames’ seismic response. In addition, herein, a number of influential parameters in effectiveness of foundation uplift are identified and examined. Also, at the end of this study, capability of Nonlinear Static Analysis method in prediction of uplift-permitted frames’ maximum internal deformations is investigated. The examined frames include both moment frames and braced ones. While modeling and analyzing soil-structure systems, which are performed in OpenSees, nonlinearity of both structural material and geometry are taken into account. To model soil-foundation system Beam on Winkler Foundation method is employed. According to the results of this study, in general, foundation uplift could considerably reduce internal deformation demands and change distribution of story ductility demands. Moreover, it is indicated that existing Nonlinear Static Analysis method is unable to estimate the maximum response parameters in the frames allowed to uplift
  9. Keywords:
  10. Soil-Structure Interaction ; Nonlinear Analysis ; Seismic Performance ; Foundation Uplift ; Two Dimensional Frame ; Nonlinear Static Analysis

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