Pine-like elastic metamaterials for urban seismic Rayleigh wave attenuation

Abstract

AbstractPreventing urban regions from seismic wave destruction is of paramount significance because it is closely related to urban lifeline and prosperity of cities. Almost all conventional seismic resistance approaches rely on the stiffness and strength of buildings, which require excessive structural components with additional self-weights. In this study, we propose a pine-like seismic metamaterial for efficient attenuation of surface Rayleigh waves. The pine arrays in suburban regions demonstrate an ability to convert Rayleigh waves to shear bulk waves or attenuate waves on the surface via local resonation. This property originates from a gradient design of pine arrays, where a scale ratio is defined to tune the geometric properties of each pine unit. Specifically, a gradient pine array with a scale ratio smaller than one can interact with the Rayleigh waves and convert them to shear waves that propagate deep to underground. The transmission ratio of the entire system indicates a broadband wave attenuation at subwavelength scale. It reveals that the pine is able to couple with a certain elastic Rayleigh wave whose wavelength is much larger than the lattice constant, which is rarely achieved in any conventional civil engineering structures such as open trench barriers and filled trench barriers. Additionally, a numerical model of an urban region and suburban pine array is established and analyzed. Infrastructures and structures in a city that suffer direct Rayleigh wave interference run into a high risk of structural destruction as compared to urban structures protected with suburban metamaterial pine arrays. Finally, two real earthquake wave signals are used to validate the efficiency of the pine arrays in dissipating earthquake energy. The approach in this paper can be extended to deal with more complex naturally available structures for examining the elastic wave attenuation abilities of these novel structures.