Theoretical and numerical studies of semi

To clarify the feasibility of a novel, semi-active friction damper, its damping characteristics were investigated theoretically and numerically. The proposed damper suppresses vibrations by changing the direction of the frictional force, in contrast to the conventional passive and semi-active friction dampers that only focus on the magnitude of the frictional force. The theoretical analysis indicates that the proposed damper can behave as a conventional friction damper or a viscous damper depending on the use conditions; further, its effective damping ratio can be controlled by the velocity of a friction plate moving in a direction orthogonal to the direction of the vibration. The numerical simulations clarified that damping characteristics can be controlled by the ratio of the amplitude of the excitation force to the frictional force. Finally, the design criteria of the proposed damper were derived