Traditional tuned mass damper（TMD）is generally designed for a single mode of structures.However

when it is applied to structures with closely spaced natural frequencies

supplemental mass of TMD will be too huge.To decrease extra mass of TMD

a new bi-directional TMD with shared mass and eddy current damping is developed in view of wind-induced coupled vibration of long-span cable-stayed bridges with closely spaced natural frequencies.The cantilever beam acts as the stiffness components of horizontal TMD

while pressure spring is adopted as the stiffness members of vertical TMD.Horizontal TMD is set at the top of vertical TMD as a whole

thus all the mass of the horizontal TMD is used as the mass of vertical TMD.As such

shared mass is realized.Since conductive plate is fixed and permanent magnet array is mounted on the TMD

when the mass of TMD moves in vertical or horizontal direction in line with main structures

corresponding vertical or horizontal eddy current damping will be generated.Therefore

shared damping components are achieved.The results show that:（1）Eddy-current damping can make horizontal and vertical TMD share the same damping components very well

moreover

the value of eddy current damping is easily adjusted;（2）the proposed bi-directional TMD is suitable and feasible for wind-induced vibration control of long span cable-stayed bridges.