Feasibility studies in applying cork to pile-type two-layered seismic metamaterials

Abstract

Seismic metamaterials, a novel seismic engineering technology composed of multiple layers of materials, can form barriers by being periodically arranged to protect properties in a region from earthquake disasters. Parametric analysis of pile-type two-layered seismic metamaterials reveals that the outer layer material with low Poisson's ratio, low Young's modulus, and low density can achieve low and wide frequency band gap, aligning with the design objectives of seismic metamaterials. Since cork, a readily available material, meets the above characteristics, this study aims to investigate its feasibility in being applied to pile-type two-layered seismic metamaterials. Furthermore, the effect of hollows within pile-type seismic metamaterials on lowering the bound frequency of the band gaps is explored. Through laboratory-scale tests at one-fifth scale and numerical simulation, it is demonstrated that cork pile-type seismic metamaterials without hollows can generate a low and wide frequency band gap and effectively attenuate waves at frequencies ranging from 5.6 Hz to 10 Hz. In addition, employing hollows in the cork outer layer can further decrease the lower bound frequency of the band gap by 25 % and result in an effective attenuation range of 4.6 Hz–9.8 Hz while slightly reducing the width of the band gap.