DEVELOPMENT OF A MODERN BASE ISOLATION SYSTEM USING THE CONCEPT OF METAMATERIALS FUNCTIONAL FOR LOW- FREQUENCY SEISMIC WAVES

Abstract

Seismology has seen a penetration of metamaterials for a breakthrough in vibrational wave manipulation which was not possible with the standard technology. Metamaterials are artificially engineered materials, or artificially engineered arrangement of conventional materials, yielding unconventional properties that cannot be realized inherently through conventional materials. Popularly used base isolation techniques in seismic wave mitigation 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 the Bragg scattering can create a stop band region of frequencies that undergo vibrational filtration. This study proposes a two- dimensional periodic foundation system that covers a wide and an ultra-low frequency region in its bandgap, enveloping the principal frequencies of seismic waves (i.e., 0.30 Hz to 7.35 Hz calculated analytically). Conducting experimental testing on the scaled-down prototype of the proposed foundation affirmed the mathematical model and the computational testing conducted on ANSYS by showing an average of 50% attenuation in the frequency band gap (i.e., 2.54 Hz to 8.08 Hz for the scaled-down version). At the resonant frequency, the experimentation showed a 73% attenuation. This study is a pioneer for setting the baseline for periodic foundations with the capability of fully mitigating the entire spectrum of seismic vibrational effects on structures.