Unlocking Bandgap Potential: Exploring the Vibration Reduction Mechanism of Dual-Resonant Metaconcrete

The vibration reduction performance of metaconcrete is primarily attributed to the bandgap characteristics of its cells. The width and number of bandgaps determine the operational frequency range and the effectiveness of vibration reduction in metaconcrete. To address this, a dual-resonant metaconcrete is proposed in this paper. Specifically, a metal shell and a flexible soft coating are added to the exterior of the original soft coating of the resonant aggregate, transforming the resonant aggregate from a single-degree-of-freedom system into a two-degree-of-freedom system. This design further broadens the operational frequency range of metaconcrete and enhances its vibration reduction performance. In this study, an analytical model of a metaconcrete cell containing dual-resonant aggregates was established. Subsequently, the finite-element method was used to analyze the band structure, vibration modes, and energy distribution characteristics, with a focus on the bandgap characteristics of dual-resonant metaconcrete cell. To further refine the analysis, bandgap influencing factors were selected using the equivalent model method, and the influence of design parameters on the bandgap was investigated. Building upon this, an analytical model of a dual-resonant metaconcrete, composed of 12 longitudinally arranged cells, was developed. Finally, the frequency response function, time-domain characteristics, and energy flow properties of the dual-resonant metaconcrete were analyzed. The results showed that the proposed dual-resonant metaconcrete cell can generate two bandgaps, with the starting and cutoff frequencies of these bandgaps determined by the vibration modes of Resonator I, Resonator II, and the matrix. Furthermore, the elastic modulus, Poisson’s ratio, and thickness of the soft coating were identified as the key factors influencing the bandgap characteristics. The vibration reduction performance of the dual-resonant metaconcrete was demonstrated within both bandgaps. When the excitation frequency was within the bandgap, the vibration directions of the resonators and the matrix were opposite, and the superposition of these reverse vibrations resulted in a reduction of vibration at the output end. Energy was continuously converted between the kinetic energy of the resonator and the elastic strain energy of the soft coating. Under these conditions, the dual-resonant metaconcrete was shown to behave similarly to a filter, exhibiting significant filtering characteristics and energy localization. As a result, the propagation of elastic waves was shielded, achieving effective attenuation.