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Smart Structures and Systems
  Volume 24, Number 1, July 2019 , pages 83-94

Impact of cable sag on the efficiency of an inertial mass damper in controlling stay cable vibrations
Zhi-hao Wang, Hui Gao, Yan-wei Xu, Zheng-qing Chen and Hao Wang

    Passive negative stiffness dampers (NSDs) that possess superior energy dissipation abilities, have been proved to be more efficient than commonly adopted passive viscous dampers in controlling stay cable vibrations. Recently, inertial mass dampers (IMDs) have attracted extensive attentions since their properties are similar to NSDs. It has been theoretically predicted that superior supplemental damping can be generated for a taut cable with an IMD. This paper aims to theoretically investigate the impact of the cable sag on the efficiency of an IMD in controlling stay cable vibrations, and experimentally validate superior vibration mitigation performance of the IMD. Both the numerical and asymptotic solutions were obtained for an inclined sag cable with an IMD installed close to the cable end. Based on the asymptotic solution, the cable attainable maximum modal damping ratio and the corresponding optimal damping coefficient of the IMD were derived for a given inertial mass. An electromagnetic IMD (EIMD) with adjustable inertial mass was developed to investigate the effects of inertial mass and cable sag on the vibration mitigation performance of two model cables with different sags through series of first modal free vibration tests. The results show that the sag generally reduces the attainable first modal damping ratio of the cable with a passive viscous damper, while tends to increase the cable maximum attainable modal damping ratio provided by the IMD. The cable sag also decreases the optimum damping coefficient of the IMD when the inertial mass is less than its optimal value. The theoretically predicted first modal damping ratio of the cable with an IMD, taking into account the sag generally, agrees well with that identified from experimental results, while it will be significantly overestimated with a taut-cable model, especially for the cable with large sag.
Key Words
    inertial mass damper; stay cable; vibration control; cable sag; modal damping ratio
Zhi-hao Wang, Hui Gao and Yan-wei Xu: International Joint Research Lab for Eco-building Materials and Engineering of Henan Province, North China University of Water Resources and Electric Power, Zhengzhou 450045, China
Zheng-qing Chen: Key Laboratory for Wind and Bridge Engineering of Hunan Province, Hunan University,
Changsha 410082, China
Hao Wang: Key Laboratory of Concrete and Pre-stressed Concrete Structure of Ministry of Education,
Southeast University, Nanjing 210096, China


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