Large scale mechanical metamaterials as seismic shields

Abstract

Earthquakes represent one of the most catastrophic natural events affecting mankind. At present, a universally accepted risk mitigation strategy for seismic events remains to be proposed. Most approaches are based on vibration isolation of structures rather than on the remote shielding of incoming waves. In this work, we propose a novel approach to the problem and discuss the feasibility of a passive isolation strategy for seismic waves based on large-scale mechanical metamaterials, including for the first time numerical analysis of both surface and guided waves, soil dissipation effects, and adopting a full 3D simulations. The study focuses on realistic structures that can be effective in frequency ranges of interest for seismic waves, and optimal design criteria are provided, exploring different metamaterial configurations, combining phononic crystals and locally resonant structures and different ranges of mechanical properties. Dispersion analysis and full-scale 3D transient wave transmission simulations are carried out on finite size systems to assess the seismic wave amplitude attenuation in realistic conditions. Results reveal that both surface and bulk seismic waves can be considerably attenuated, making this strategy viable for the protection of civil structures against seismic risk. The proposed remote shielding approach could open up new perspectives in the field of seismology and in related areas of low-frequency vibration damping or blast protection.

Elastic Wave Control Beyond Band-Gaps: Shaping the Flow of Waves in Plates and Half-Spaces with Subwavelength Resonant Rods

“…Devices based on exploiting band-gap phenomena, as seismic shields using ideas from Bragg-scattering (Brûlé et al, 2014;Miniaci et al, 2016) or zero-frequency stop-bands (Achaoui et al, 2017), are gaining in popularity. At this large scale, an important analogy may exist between the metamaterial discussed here and clusters of high-rise buildings in urban areas.…”

“…If we limit our discussion to elastic metamaterials, potential applications could be implemented at any lengthscale. On the large scale, seismic metamaterials have become very popular (Brûlé et al, 2014;Finocchio et al, 2014;Dertimanis et al, 2016;Miniaci et al, 2016;Achaoui et al, 2017). At smaller scale, in mechanical engineering, applications based on wave redirection and protection are currently being explored (Colombi, 2016;Colombi et al, 2017) to reduce vibrations in high precision manufacturing and in laboratories for high precision measurements (e.g., interferometry) or in the field of ultrasonic sensing to amplify signal to noise ratio.…”

Coupling local resonance with Bragg band gaps in single-phase mechanical metamaterials

“…The possibility they provide to manipulate and attenuate elastic waves at various frequencies can be exploited for various applications, ranging from seismic shielding [1,2] or noise abatement [3] to subwavelength imaging [4] and thermal management [5]. These fundamental properties arise from metamaterial geometry and/or composition and are due to the existence of band gaps (BGs)-frequency ranges, in which wave propagation is inhibited.…”

Wave propagation in cellular locally resonant metamaterials

“…in the range of some kHz, without requiring very large dimensions as it happens for phononic crystals (Wu et al, 2007;Croënne et al, 2011;Hussein et al, 2014;Miniaci et al, 2015;Ma and Sheng, 2016;D'Alessandro et al, 2016). This property can be exploited in different contexts ranging from seismic insulation (Miniaci et al, 2016) to impact absorbers in small cars (Comi and Driemeier, 2017). Usually LRAMs are composed of a matrix with a periodic arrangement of small resonators wrapped in a soft coating.…”