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Investigating the Application of y-Braced Frames in Seismic Performance of Steel Structures

Majid Zamani, Sohail | 2012

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  1. Type of Document: Ph.D. Dissertation
  2. Language: Farsi
  3. Document No: 43075 (09)
  4. University: Sharif University of Technology
  5. Department: Civil Engineering
  6. Advisor(s): Vafai, Abolhassan
  7. Abstract:
  8. Finding suitable locations for installing conventional concentric bracings such as X and V, without interfering with building architecture and its openings, is a routine challenge in building design. One of the less known forms of concentric bracings which can be used to solve this issue, is the y-shaped bracing composed of three braces. In the current thesis, results of analytical studies, computer modeling and experimental tests are presented to extend the knowledge of structural behavior of y-bracings. As the first step, effective buckling lengths of braces with rigid connections were found from equilibrium equations incorporating the effect of axial force on rotational stiffness of braces. Lateral load resistance of two experimental specimens was predicted using these effective length factors and found to be in good agreement with test results. Next, the lateral load bearing capacity of a range of y-braced frames with varying geometrical proportions and location of convergence point was investigated. Based on these studies it is proposed to locate the point of convergence on the bay diagonal. A series of finite element analyses of single bay y-braced frames is achieved to assess the main structural features such as lateral stiffness, strength, energy dissipation and hysteretic damping. Based on the preferred behavior of concentric bracings with load bearing compressive braces, suitable places for positioning the convergence point are proposed. To investigate the real behavior of symmetrical y-braced frames, a series of eight full scale models were fabricated and tested under increasing cyclic loading. The main structural features such as lateral stiffness, strength, energy dissipation and hysteretic damping of specimens are discussed and compared. To facilitate analytical studies, finite element models with frame elements are constructed and calibrated to reproduce the cyclic load bearing of experimental specimens. Finally, the seismic performances of the experimental specimens are investigated using capacity spectrum method based on real pushover curves and hysteretic damping values
  9. Keywords:
  10. Bracing ; Buckling ; Capacity Spectrum ; Concentric Bracing ; Y-Bracing

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