Three-component composite columns periodically buried in elastic half space as metasurfaces for broadband surface-wave attenuation

Abstract

Elastic metamaterials/metasurfaces have enabled many applications for vibration reduction in civil engineering in the past decade. This paper investigates the feasibility of harnessing novel three-component composite columns for surface-wave attenuation. The composite columns are periodically buried near the surface of an elastic half space to form a metasurface. Eigenvalue studies are conducted based on both the $\omega \left(k\right)$ and $k\left(\omega \right)$ methods, and broadband surface-wave bandgaps (SWBGs) are found in real and complex band structures. For the metasurface composed of concrete-rubber-steel composite columns, a broadband SWBG covering 36.5–96.9 Hz can be achieved with a small periodic constant of 0.3 m. The formation of the broadband SWBG is attributed to the local resonance mechanism, whose lower bound frequency is determined by the resonance of the core and upper bound frequency is mainly determined by the torsional resonance of the soft coating layer. Using complex band structures and frequency-domain simulations, the lack of correlation between the minimum imaginary parts of wave numbers and vibration reduction performance is well explained. In addition, it is found that the evanescent surface eigenmodes in the SWBG can be excited and observed in numerical simulations, indicating the complex band structure analysis is effective for understanding how surface waves decay in SWBGs. A comprehensive parametric study is performed to investigate the influence of geometric parameters, material parameters, and damping in material on the attenuation performance of the metasurface. The feasibility of applying the metasurface to mitigate train-induced ambient vibration is investigated via time-domain numerical simulations.