Research on multi-oscillator locally resonant seismic metamaterials and the uniform and gradient design for broadband Rayleigh wave attenuation

The dimensions of seismic metamaterials pose limitations that make attenuating ultra-low frequency seismic surface waves (with a starting frequency near 0 Hz) in confined spaces through structural design a significant challenge. This paper introduces a locally resonant seismic metamaterial (SM) characterized by an ultra-low frequency wide bandgap, created by placing a nylon barrier embedded with steel oscillators between two steel plates. The bandgap is calculated using dispersion analysis and phononic crystals method, delineating the attenuation range of the seismic metamaterial. Parameter analysis results show that greater oscillator mass, thinner nylon barrier thickness, and higher external barrier height favor broader bandgap width and reduced bandgap frequency. By introducing the concept of multiple oscillators and “uniform and gradient,” the isolation performance of the SM is significantly enhanced, while the impact of the Fano-like phenomenon on attenuation is simultaneously reduced. This indicates that multi-oscillator and “uniform and gradient” are ideal solutions for opening ultra-low frequency bandgaps. Finally, the dynamic response of the SM is clarified through time-domain analysis, further validating the effectiveness of the research. We hope that this study can promote the engineering application of common building materials in the shielding of deep subwave length frequency seismic waves.