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Evaluation of Post-Tensioned Connection's Effectiveness in Behavioral Characteristics and Residual Drift of Steel Structures

Rashtak, Mahdi | 2018

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 50938 (09)
  4. University: Sharif University of Technology
  5. Department: Civil Engineering
  6. Advisor(s): Rahimzadeh Rofooei, Fayaz
  7. Abstract:
  8. This study evaluated post-tensioned system’s behavior in the steel structure. The post-tensioned system includes post-tensioned frame and gravity system (gravity frame and floor diaphragm) and considers the interaction of post-tensioned frame with gravity frame. Post-tensioned frame is the moment frame that has post-tensioned connections instead of ordinary connections. Bolted top and seat angles are used in the connection, along with post-tensioned high strength strands that run parallel to the beam. The strands compress the beam flanges against the column flange to develop a resisting moment and the friction between the beam and column and the two angles resist shear. Studies showed that the post-tensioned connection has self-centering performance. During an earthquake, post-tensioned connection decompresses and a gap develops between the tensioned flange of beam and column. In this condition, angels yield and play dissipating energy role. When the moment becomes zero, the gap closes and the connection returns to the first condition with no permanent deformation. The purpose of this study is the evaluation of post-tensioned frame’s behavior under near-field ground motions. The analytical model of post-tensioned connection was developed and verified against test results. Post-tensioned frames in different stories were designed, according to design recommendation procedure. For investigation benefits of this frame, special steel moment frames with same stories were designed according to the steel frame design codes. Developed analytical models of the frames were analyzed under nonlinear static and dynamic loadings. The results show that post-tensioned frame has good ductility and energy dissipation and self-centering ability. In this connection, beams have large axial load cause of post-tensioning. Under loading, the moment in post-tensioned beams is less than that in MRF’s beams. During an earthquake, connections decompress and behavior of post-tensioned frame will be softer. As a result, input energy and base shear will be less than that in moment frames. Models were developed and analyzed in OpenSees program
  9. Keywords:
  10. Steel Moment Resistant Frame ; Post Tensioning ; Behavioral Specification ; Self-Centering ; Permanent Displacement

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