Tuned mass dampers (TMDs) have been widely used in recent years to mitigate structural vibration.However,the damping mechanisms employed in the TMDs are mostly based on viscous dampers,which have several well-known disadvantages,such as oil leakage and difficult adjustment of damping ratio for an operating TMD.Alternatively,eddy current damping (ECD) that does not require any contact with the main structure is a potential solution.This paper discusses the design,analysis,manufacture and testing of a large-scale horizontal TMD based on ECD.First,the theoretical model of ECD is formulated,then one large-scale horizontal TMD using ECD is constructed,and finally performance tests of the TMD are conducted.The test results show that the proposed TMD has a very low intrinsic damping ratio,while the damping ratio due to ECD is the dominant damping source,which can be as large as 15% in a proper configuration.In addition,the damping ratios estimated with the theoretical model are roughly consistent with those identified from the test results,and the source of this error is investigated.Moreover,it is demonstrated that the damping ratio in the proposed TMD can be easily adjusted by varying the air gap between permanent magnets and conductive plates.In view of practical applications,possible improvements and feasibility considerations for the proposed TMD are then discussed.It is confirmed that the proposed TMD with ECD is reliable and feasible for use in structural vibration control.