Centrifuge-based experimental validation of seismic resonant metamaterials for structural protection

This study presents the first rigorous experimental validation of seismic resonant metamaterials for structural protection against vertically propagating horizontal seismic shear waves. Its primary goal is to assess the effectiveness of metabarriers (arrays of soil-embedded, unit-cell resonant metamaterials) in attenuating structural vibrations induced by real earthquake ground motions. Two dynamic centrifuge model tests were conducted at 50 g at the ETH Zurich Geotechnical Centrifuge Centre. The first experiment simulates the seismic response of an unprotected single-degree-of-freedom structure. In the second, unit-cell resonant metamaterials are embedded in the soil on both sides of the structure. Both models are subjected to identical seismic excitations, enabling direct comparison. The 3D-printed unit cells are equipped with tuned internal masses to achieve a horizontal vibration frequency of 150 Hz, close to the structure’s fixed-base frequency of 160 Hz. A laminar container is used to ensure realistic boundary conditions, filled with dense Hostun sand. Instrumentation includes accelerometers in the soil, on the container, and on the structure, as well as high-speed cameras for digital image correlation (DIC). Frequency-domain analysis shows that resonant metamaterials significantly reduce structural and near-field accelerations at resonance, with DIC revealing the underlying protective mechanism, caused by the out-of-phase vibration of the unit-cell masses relative to the soil.