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Steel and Composite Structures
  Volume 21, Number 4, July20 2016 , pages 863-882
DOI: https://doi.org/10.12989/scs.2016.21.4.863
 


Cable-pulley brace to improve story drift distribution of MRFs with large openings
Seyed Mehdi Zahrai and Seyed Amin Mousavi

 
Abstract
    This study aims to introduce a new bracing system by which even super-wide frames with large openings can be braced. The proposed system, hereafter called Cable-Pulley Brace (CPB), is a tension-only bracing system with a rectilinear configuration. In CPB, a wire rope passes through a rectilinear path around the opening(s) and connects the lower corner of the frame to its opposite upper one. CPB is a secondary load resisting system with a nonlinear-elastic hysteretic behavior due to its initial pre-tension load. As a result, the required energy dissipation would be provided by the MRF itself, and the main intention of using CPB is to contribute to the initial and post-yield stiffness of the whole system. Using a stiffness calibration technique, optimum placement of the CPBs is discussed to yield a uniform displacement demand along the height of the structure. A displacement-based design procedure is proposed by which the MRF with CPB can be designed to achieve a uniform distribution of inter-story drifts with predefined values. Obtained results indicated that CPB leads to significant reductions in maximum and residual deformations of the MRF at the expense of minor increase in the maximum base shear and developed axial force demands in the columns. In the case of a typical 5-story residential building, compared to SMRF system, CPB system reduces maximum amounts of inter-story and residual drifts by 35% and 70%, respectively. Moreover, openings of the frame are not interrupted by the CPB. This is the most appealing feature of the proposed bracing system from architectural point of view.
 
Key Words
    wire rope; tension-only brace; cable brace; self-centering; residual drift; optimal stiffness distribution
 
Address
School of Civil Engineering, College of Engineering, the University of Tehran, Tehran, Iran.
 

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