Performance of a nonlinear tuned mass damper in structural vibration control of multi degree of freedom systems

Mitigating structural vibrations using passive dampers has proven to be an effective method for reducing the response of structures to dynamic loadings at a reasonable cost and with typically simple configurations. Various types of tuned mass dampers (TMDs) have been proposed to mitigate undesirable oscillations in structural systems. Despite their cost-effective performance, linear TMDs come with limitations such as reduced effectiveness in case of excitations with broad frequency bandwidth, and the large mass and stroke requirements. Nonlinear stiffness TMDs, on the other hand, have gained considerable attention as they potentially suffer less from the limitations imposed on linear dampers. In this study, a bi-directional magnetic damper, considered as a nonlinear TMD, is numerically compared to a typical linear TMD at different mass ratios. A three degrees of freedom (3-DOF) structure equipped with both dampers is subjected to various types of dynamic excitations. The dampers are optimized using a numerical search that minimizes the Root Mean Square (RMS) value of the structure’s displacement response. Results reveal that the proposed damping device outperforms the linear TMD in all loading scenarios, with its superiority being more pronounced under excitations with broad frequency content. It was also observed that the nonlinear damper can match or exceed the performance of the linear TMD at lower damper-to-structure mass ratios.