Robustness Analysis of Asymmetric NES Via Nonlinear Normal Modes

Abstract Nonlinear Energy Sink (NES) absorbers excel in comparison to traditional Tuned Mass Dampers (TMD) due to their superior efficiency over a wider range of frequencies. However, despite the advantages of NES over TMDs, their susceptibility to variations in system energy poses a challenge, particularly in applications where the primary structure is subjected to random excitations. A modified NES, referred to as Asymmetric NES (ANES), has previously demonstrated a substantial enhancement in NES robustness, opening up new possibilities for this particular case. This study investigates the factors contributing to the superior robustness of ANES in comparison to the performance of traditional cubic NES. Through an analysis utilizing Nonlinear Normal Modes (NNM) and Frequency Energy Plots (FEP), this research illustrates that the improved effectiveness of Asymmetric NESs results from a more intricate interaction of the ANES nonlinear normal modes with the kinetic energy FEP of the primary structure. In this work, the NNMs of tuned ANES and NES absorbers with similar mass are generated and plotted alongside the kinetic energy FEP of a three-story shear building subjected to various earthquake ground accelerograms. The findings reveal that the NNM of the ANES absorber intersects more effectively with the system’s energy FEP, explaining the superior robustness of the ANES against variations in the input spectrum power.