Broadband inverted T-shaped seismic metamaterial

Seismic metamaterials: Generating low-frequency bandgaps induced by inertial amplification

“…Theoretically, the depth of the half-space should be infinitely deep. In order to facilitate simulation calculations and obtain relatively accurate convergence results, the depth of the soil substrate is selected as H = 500a [42,47]. A part of the spring is replaced by a thin rubber layer with thickness of t1 to achieve bandgaps at lower frequencies.…”

“…In addition, for better integration of SMs in the foundation of a building for seismic isolation purposes, Yan et al [35] proposed a 2D periodic foundation constituted of ductile cast iron, supper soft rubber and reinforced concrete, while Casablanca et al [36] designed a periodic mass-in-mass foundation placed underneath buildings. To obtain wider bandgaps, the pillars with different kinds of structures [28,[37][38][39][40][41][42], and the "rainbow trapping effects" [8,29,34,[43][44][45][46][47] were utilized. However, the ultra-low-frequency (< 2 Hz) bandgaps are hard to obtain by using small-size structures.…”

Inertially amplified seismic metamaterial with an ultra-low-frequency bandgap

“…[1][2][3][4][5][6][7] The SMs composed of an array of artificial structures on or in a soil substrate usually possess the bandgap characteristics, whose working wavelengths is much longer than the size of the artificial structure. [4][5][6][7][8][9][10] A number of experiments [1,3,11] and simulations [5,[12][13][14] have demonstrated that the SMs can significantly attenuate seismic waves at the frequencies of the bandgaps. In 1999, a phononic crystal in a marble was designed to experimentally demonstrate the existence of elastic bandgaps and the possible applications of SMs.…”

“…Also, researchers proposed SMs composed of an array of pillars on a soil substrate to achieve low-frequencies bandgap, when they got inspiration that the seismic waves can be attenuated by the forests. [5,9,22] To obtain wide bandgaps, different kinds of shape of the pillars [6,11,23,24] were proposed and the "rainbow trapping effects" [9,14,[25][26][27] were used. However, at present, the bandgap for seismic surface waves below 5 Hz is still challenging to obtain just by using smallmass structures.…”

“…It is noted the unit cell of the TM has more mass than the IAM, but the frequency of the 10 first bandgap of the TM for flexural waves is much higher than the IAM. The band structure of the TM, which is easy to calculate just by using Solid Module of the COMSOL, [3,4,11,41] is not illustrated in this letter. At points B and D, almost all the displacement appears around the hinge joint between two arms, which means that there is a strong resonance only on the two arms.…”