Seismic metamaterials as foundations for buildings subjected to incident plane and bending waves: Simulation and experiment

Periodic materials exhibit distinct band gap characteristics with attenuation zones that can block specific frequency waves from propagating through a structure, making them effective for reducing unwanted seismic waves in civil engineering applications. However, previous studies mainly focused on theoretical derivations and numerical simulations of seismic metamaterial foundations, with little emphasis on experimental validation, especially for metamaterial foundations with superstructures. Meanwhile, the vertical seismic isolation performance of the foundation, induced by the vertical polarization motion of seismic surface waves, has largely been overlooked. This paper presents a novel scaled model of a seismic metamaterial foundation for a four-story building, verifying its horizontal and vertical seismic isolation behavior under planar and bending wave propagation, respectively, via theoretical, numerical, and experimental analyses. Theoretical analysis offers a closed form for determining the attenuation zone range, while numerical simulations illustrate the characteristics and mechanisms of seismic isolation. The experimental results confirm the robustness of the analytical and numerical models and demonstrate that the vibration energy within the attenuation zone is effectively attenuated. Moreover, the presence of the superstructure did not adversely affect the attenuation zone, despite being an attachment to the metamaterial foundation. The metamaterial foundation is designed to cover a wide ultra-low attenuation zone, effectively encompassing the dominant seismic wave frequencies (i.e., below 10 Hz). The results highlight new applications of metamaterials in foundation engineering, demonstrating its potential for protecting civil infrastructure against both planar and bending waves induced by seismic activity.