Development of a new base isolation system using the concept of metamaterials

Metamaterials are making a breakthrough in seismic wave manipulation with their ability to yield wave filtration properties that cannot be realized inherently through conventional construction materials. The popularly used seismic vibrational control techniques, such as base isolation, fall short at low-frequency regions of the spectrum and fail to encompass both flexible and rigid structures. Using the concept of metamaterials, the phenomena of local resonance and Bragg scattering can create a stop band region of frequencies that undergo vibrational wave filtration. This study proposes a two-dimensional periodic foundation system with steel-silicone embedded assemblies to serve as local resonators. The proposed foundation can cover a wide and ultra-low frequency region in its band gap, enveloping the principal frequencies of seismic waves (i.e., 0.2 Hz to 10 Hz). This twodimensional periodic foundation can also exhibit a Bragg region without local resonators but is made more efficient with the help of steel-silicone resonators (SSR). Upon experimental testing, the scaled-down prototype of the proposed foundation with three locally resonant panels embedded with SSR showed an average of 50 % attenuation of displacement within the frequency band gap (i.e., 2.54 Hz to 8.08 Hz). Moreover, the experimentation showed a 73 % attenuation at the resonant frequency of SSR. Experimental testing affirmed the frequency band gap obtained through mathematical formulation. Furthermore, the theoretical results demonstrate that the full-scale proposed periodic foundation would be able to achieve a band gap that covers frequencies from as low as 0.3 Hz to 7.35 Hz. This study is the first attempt to set the baseline for periodic foundations capable of fully mitigating the entire spectrum of seismic vibrational effects on structures.