Low-frequency bandgap characteristics and vibration attenuation performance of metamaterial-tailored concrete-filled steel tube columns

Abstract

Low-frequency vibrations, such as earthquakes and wind loads, may negatively affect the proper operation of buildings and bridges and even lead to structural failure. Even though, in the past two decades, metamaterial-based structures have been utilized in structure vibration suppression, they are mainly used in the mitigation of high-frequency vibrations, and it has been an open challenge to suppress low-frequency vibrations below 100Hz and ensure adequate bearing capacity in engineering structures. In this work, we present metamaterial composite column structures with built-in local resonators to achieve the low-frequency vibration mitigation effect. Compared to ordinary concrete-filled steel tube (CFST) columns, the metamaterial columns (meta-columns) can utilize the rubber shear modulus to create a low-frequency flexural bandgap in 30–50 Hz. Dynamic stiffness is introduced in the Timoshenko beam and Bloch's theorem, the metamaterial analytical model is established, and the bandgap generation mechanism and vibration reduction effect are analyzed in conjunction with numerical simulations. Then, the bandgap effect and vibration attenuation law of the meta-columns are investigated by shaker tests at different acceleration amplitudes. Guided by theory and simulations, we have successfully fabricated several meta-composite columns with low-frequency bandgaps, which attenuate up to half of the vibrational energy near the bandgap center. The bandgap ranges derived from the theoretical and numerical models show a high degree of consistency with the experimental results, with deviations generally within 10 %, all indicating that a bandgap exists near the resonator self-oscillation frequency. Additionally, the bandgap is significantly affected by the number of unit cells and resonators, especially the meta-column with fewer resonators fails to form a bandgap where the top response is smaller than the bottom response. As the number of resonators and metamaterial units increases, the meta-columns exhibit wider bandgap and stronger vibration reduction performance.