On seismic isolation of soil-meta-foundation-structure systems

Meta-materials are engineered composites with physical properties that can introduce frequency band gap regions suitable for wave manipulation and filtering. This study investigates the seismic behavior of soil–structure systems with a meta-foundation designed using alternatively repeated layers of concrete and rubber. First, the frequency band gaps of the meta-foundation were derived using the Floquet-Bloch theory. The frequency band gaps for different meta-foundation configurations with infinite and finite numbers of unit cells were presented. Then, a two-dimensional (2D) plane-strain finite element simulation was proposed to study the isolation performance of meta-foundations on or embedded in soil half-space. Finally, two four-story steel structures with different dynamic characteristics were modeled under different input motions. The results show that direct embedment of meta-foundations in soil may break periodicity, requiring special treatments on the side boundaries of the foundation. Moreover, the numerical results show considerably enhanced structural performance for the meta-foundation system with a reduction up to 95.1% and 97.9% for the maximum horizontal acceleration and inter-story drift, respectively, compared to the non-isolated system. The results also indicate enhanced soil response under the meta-foundation and acceptable structural performance outside the band gap frequencies compared to the non-isolated system.