田字形地震超材料甚低频宽带隙机理

在地球中传播的地震波主要有体波和表面波,而表面波中Rayleigh波对建筑物造成的破坏最为强烈。针对Rayleigh波的振动控制,提出一种田字形超材料结构。相比于传统的地震超材料,这种超材料屏障是由外部口字形框体内部嵌套十字形柱体组成,形成4个可填充区域,其外部框体采用部分埋入的方式,具有高强度、强稳定性、填充方式灵活的特点。应用有限元法计算了田字形超材料的能带结构和传输特性,并通过分析带隙边界处模态振型可知,带隙的打开是由于柱体的局域共振。结合带隙机理可知,柱体结构中土壤填充量不同可改变柱体的质量,形成不同的谐振频率,产生甚低频带隙。为进一步拓宽带隙,设计研究了正、负梯度的质量填充方式,均可得到3.3~13.1 Hz甚低频宽带隙,在谐振频率范围内两者的隔震方式分别为Rayleigh波彩虹捕获和Rayleigh波到体波的转化。最后,采用EI-Centro地震波对填充屏障进行了时程验证,加速度最大幅值衰减超过80%,为地震超材料在减震隔震方面应用提供了新的设计思路和方法。

Very Low Frequency Broadband Gap Mechanism of Tian-Shaped Seismic Metamaterials

The seismic waves propagating in the earth mainly include body wave and surface wave, and Rayleigh wave in surface wave has the strongest damage to buildings. For the vibration control of Rayleigh waves, a Tian-shaped metamaterial structure was proposed. Compared with the traditional seismic metamaterials, this metamaterial barrier is composed of a nested cross column inside an external oral frame, forming four filling areas. The external frame is partially embedded, with high strength, strong stability and flexible filling methods. The band structure and transmission characteristics of Tian-shaped metamaterial were calculated by finite element method. By analyzing the mode shapes at the band gap boundary, it is found that the band gap opening is due to the local resonance of the cylinder. Combined with the band gap mechanism, different amounts of filling in the cylinder structure can change the quality of the column structure, form different resonant frequencies, and produce a very low frequency band gap. Furthermore, the mass filling methods with positive and negative gradients were designed and studied to broaden the band gap, and 3.3~13.1 Hz very low frequency broadband gap can be obtained. In the resonant frequency range, the isolation methods of the two are Rayleigh wave rainbow capture and Rayleigh wave to body wave conversion. Finally, the EI-Centro seismic wave was used to verify the time history of the filled barrier. The maximum acceleration attenuation is more than 80%, which provides new design ideas and methods for seismic metamaterials in damping and isolation.