Seismic metamaterials with cross-like and square steel sections for low-frequency wide band gaps

This study investigates the propagation of Lamb waves in seismic metamaterials (SMs) assembled using periodically arranged cross-like and square steel sections in a soil medium to assess the feasibility of their use for seismic wave attenuation. Four types of SMs with different steel sections were considered. The finite element method was used to carry out numerical simulations to investigate the band gap characteristics, vibration modes, and the effects of various parameters of the SMs. The results show that SMs with three complete band gaps (CBGs) below 20 Hz are of particular interest for low-frequency vibration control. The SMs composed of square steel sections exhibit a more favorable performance as compared to the SMs composed of cross-like steel sections in terms of the formation of wider CBGs. The volume fraction of steel is beneficial for enlarging the CBGs by planarizing the upper and lower edges of a single CBG. Moreover, geometric and material parameters play important roles in the band gap distributions. A vibration simulation analysis was carried out to simulate the seismic wave propagation through the SMs to the buildings, and the results indicate that Bragg scattering is the formation mechanism for the first CBG of the four SMs. This study provides a new way to build SMs by designing the volume fraction and steel section shapes to provide ultra-low and broad-band frequency vibration isolation capabilities that will allow the shielding of seismic waves in specific frequency ranges.