Vibration Control Of Stay Cables Using The Eddy-Current Inertial Mass Damper

Stay cables,as important load-bearing components of cable-stayed bridges,are highly susceptible to dynamic excitations due to their high flexibility and low intrinsic damping.Therefore,it is necessary to take effictive measures for the serviceability and safety of the entire bridge.Transversely attaching a passive viscous damper(VD)to the stay cable has been widely implemented in practical applications,which solved the vibration problem of stay cables to a certain extent.However,it may be incapable of providing sufficient supplemental modal damping to a super-long cable,especially for the higer-order modes and multi-mode cable vibration mitigation.It is essential to further develop new passive control technologies.Relies on the project of the National Natural Science Foundation of China “The theory and technology of three-element passive mitigation of structural vibration and its performance improvement for vibration control of stay cables”(51878274),control performance of a stay cable with an eddy-current inertial mass damper(ECIMD),and two ECIMDs,either at the opposite ends or the same end of the cable,are investigated,respectively.Through theoretical analyses and model tests,parametric analyses are conducted to investigate the effects of inertial mass and damping coefficient on the supplemental modal damping ratio of the stay cable.The effect of ECIMD on vibration mitigation performance improvement of stay cables are revealed.The influence mechanisms of two ECIMDs on a stay cable are illustrated.The main conclusions of this study are summarized as follows:(1)The ECIMD,which is developed by integrating the two-node inertial mass element“inerter” based on ball screw and the axial rotating eddy-current damping element,can achieve the dual efficiency of inertial mass and eddy-current damping.The equivalent damping coefficients are reduced with the increase of excitation frequency,which is beneficial to multi-mode cable vibration mitigation.(2)The ECIMD can provide superior control performance to the stay cable over a VD.The supplemental modal damping ratio of the stay cable increases first and then decreases with the increase of the number of inertial flywheels and permanent magnent groups.Both the optimum equivalent damping coefficient and the inertial mass of the ECIMD decrease with the increase of mode order of the stay cable.Matching the ECIMD damper parameters reasonably can realize multi-mode cable vibration mitigation.(3)Compared to the ECIMD and two opposite VD,attaching two ECIMDs on the opposite end of a cable is favorable to increasing the maximum supplemental damping ratio of the cable,and its maximum supplemental modal damping ratio is asymptotically the sum of contributions from each ECIMD separately.(4)When parameters of the two ECIMD are matched reasonably,attaching two ECIMDs at the same end of the stay cable is able to obtain a larger maximum supplemental modal damping ratio than that of a single ECIMD at a bigger distance,which is even more than the sum of contributions from each ECIMD.(5)Generally,attaching two opposite ECIMDs on a cable has shown better control performance than two ECIMDs at the same end.However,installing a damper at cable-tower anchorage is difficult and inconvenient.As an alternative,attaching two ECIMDs with appropriate damper parameters at the same end of a cable seems to be more promising for practical application.