Subwavelength seismic metamaterial with an ultra-low frequency bandgap

Abstract

A subwavelength seismic metamaterial (SMs) consisting of a three-component SM plate (SMP) and a half space is proposed to attenuate ultra-low frequency seismic surface waves. The design concept and models are verified firstly by lab-scale experiments on the SM consisting of a two-component SMP and a half space. Then we calculate the band structures of the one-dimensional and two-dimensional subwavelength SMs, and evaluate their ability to attenuate Rayleigh waves. A wide ultra-low frequency band gap can be found. And the Rayleigh waves are deflected by the subwavelength SM and converted into bulk waves in the frequency range of this band gap. When the number of the unit cells of the subwavelength SM is sufficient, the transmission distance and deflection angle of the Rayleigh waves are constant at the same frequency. This discovery is expected to open up the possibility of pragmatic 2 seismic protection for large nuclear power plants, ancient buildings and metropolitan areas.

Broadband inverted T-shaped seismic metamaterial

“…The polarization direction of the source is the xz direction. 26,39,40 Accordingly, the data is collected at point B from the right side of the ITSM. Similarly, in order to obtain an accurate transmission spectrum at a sufficiently low-frequency range, the height of the substrate is set as H = 300a.…”

“…For the SM, a 1D periodic model is a general choice for exploring mechanism of the BGs. 20,26,32 However, in practical applications, the design of the 2D periodic SM is more important and necessary. 18,37,41 In addition, due to some uncontrollable factors in actual situations, such as the difficulty of achieving perfect continuity between different materials, large-scale field experiments are still needed to verify the SMs with ultra-wide and low-frequency bandgaps for surface waves.…”

“…[21][22][23][24] Therefore, most of these SMs are also called subwavelength SMs. [25][26][27] The subwavelength SMs can be roughly divided into two categories. The first kind of subwavelength SMs can also be called the underground barrier of locally resonant metamaterial.…”

Topological surface wave metamaterials for robust vibration attenuation and energy harvesting

“…Mechanical metamaterials [3] whose configurations can be artificially fabricated and modulated have been proven to manipulate the propagation of mechanical waves with new effects such as wave isolation [4][5][6][7][8][9], topological insulator [10][11][12][13][14][15][16][17][18][19], Fano resonance [20][21][22][23], chirality [24], focusing and imaging [25], among others. Especially, surface wave metamaterials [1,[26][27][28][29][30][31][32][33][34][35][36] are designed mainly for transmission suppression of low-frequency surface wave in certain frequency ranges based on the conception of hybridized bandgaps. Nonetheless, energy harvesting and signal detection of the subwavelength ground surface wave can be additional functions for surface wave metamaterials, remaining a meaningful and challenging issue that has hitherto received few attentions.…”

Coupling the first and second attenuation zones in seismic metasurface

“…The bottom surface of the unit cell is set as fixed boundary condition. The considered material parameters of steel and soil are same as the literature 33,34 .…”