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Smart Structures and Systems
  Volume 23, Number 6, June 2019 , pages 537-551

Design formulas for vibration control of sagged cables using passive MR dampers
Yuanfeng Duan, Yi-Qing Ni, Hongmei Zhang, Billie F. Jr. Spencer, \\Jan-Ming Ko and Shenghao Dong

    In this paper, a method for analyzing the damping performance of stay cables incorporating magnetorheological (MR) dampers in the passive control mode is developed taking into account the cable sag and inclination, the damper coefficient, stiffness and mass, and the stiffness of damper support. Both numerical and asymptotic solutions are obtained from complex modal analysis. With the asymptotic solution, analytical formulas that evaluate the equivalent damping ratio of the sagged cable-damper system in consideration of all the above parameters are derived. The main thrust of the present study is to develop an general design formula and a universal curve for the optimal design of MR dampers for adjustable passive control of sagged cables. Two sag-affecting coefficients are derived to reflect the effects of cable sag on the maximum attainable damping ratio and the optimal damper coefficient. For the cable configurations commonly used in cable-stayed bridges, the sag-affecting coefficients are directly expressed in terms of the sag-extensibility parameter to facilitate the control design. A case study on adjustable passive vibration control of the longest cable (536 m) on Stonecutters Bridge is carried out to demonstrate the influence of the sag for the damper design, and to figure out the necessity of adjustability of damper coefficients for achieving maximum damping ratio for different vibration modes.
Key Words
     sagged cable; vibration mitigation; MR damper; passive control; open-loop control
Yuanfeng Duan, Hongmei Zhang and Shenghao Dong: Department of Civil Engineering, College of Civil Engineering and Architecture, Zhejiang University, Hangzhou 310058, P. R. China
Yi-Qing Ni and Jan-Ming Ko: Department of Civil and Environmental Engineering, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong
Billie F. Jr. Spencer: Department of Civil and Environmental Engineering, The University of Illinois at Urbana-Champaign, Urbana-Champaign, Illinois, USA


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