A novel design strategy of track-based asymmetric nonlinear energy sink for seismic response mitigation of structures

Mass dampers, whether linear or nonlinear, rely on resonance with the structure to achieve optimal control performance. However, linear mass dampers require frequency tuning, while nonlinear mass dampers are sensitive to input energy levels, rendering both inadequate for control problems that involve frequency and energy uncertainties. To address this issue, the track asymmetric nonlinear energy sink (TANES) has been developed as a robust mass damper against frequency and energy changes. In this study, a novel design strategy consisting of physical and parameter design was proposed for TANESs. First, TANESs with inverted tracks as the auxiliary mass were proposed, resulting in a significant reduction in the dimensions and weight of the device. The new physical design was then realized, and the mathematical descriptions of the TANES system were validated through experiments on a two-story frame structure. Subsequently, a parameter design method was proposed to match the frequency variation pattern of the TANES with the given structural and load conditions. Following the design procedure, three TANESs with markedly different track shapes were obtained and compared with existing mass dampers under different types of excitations. Results showed that the frequency responses of the TANES systems subjected to harmonic ground excitations shared great similarity with those of a well-tuned TMD system at small-to-moderate energy levels. As the energy level increased, nonlinear responses such as strongly modulated responses were observed in the TANES systems with decrease structural frequencies, which significantly reduced the resonant peak in the frequency responses. The frequency responses of the TANES systems were consistent with the design objective and could be used to quantitatively predict the robustness performance of the devices under impulsive and seismic excitations. With the reduced dimensions and weight resulting from the inverted-track configuration and the robustness performance in line with common structural and load conditions, the proposed design strategy of TANESs demonstrated great potential in the seismic response mitigation of engineering structures.