具有低频超宽衰减域的部分埋入式表面波屏障

针对低频Rayleigh表面波,设计了部分埋入式工字形截面周期波屏障。利用有限元方法计算了结构的频散曲线,分析了带隙的形成机理,讨论了屏障埋入土体深度和截面参数对带隙的影响,在此基础上设计了具有低频超宽衰减域的梯度及分段梯度波屏障并计算了其传输谱。结果表明:周期波屏障存在较宽带隙,板埋入深度和端部尺寸是影响带隙的关键参数,通过参数调节可实现不同频段Rayleigh波的调控。工字形变截面波屏障比等截面具有更优越的隔震性能且节省材料。梯度及分段梯度波屏障显著拓宽了衰减域的频率范围,对1.5~20 Hz范围内的Rayleigh表面波实现了全覆盖,用小尺寸控制了大波长。

Partially embedded barrier for broad band attenuation of surface waves in low frequencies

The I-shaped partially embedded periodic wave barrier is designed and studied for low-frequency Rayleigh surface waves. The dispersion curves are calculated by the finite element method;the mechanism of the bandgap generation is explored;and the effects of geometric parameters and the embedded depth on the bandgap are discussed. On this basis, gradient and piecewise gradient wave barriers with ultra wide attenuation domain in low frequenciy region are designed and the transmission spectra are calculated. The results show that the periodic wave barrier has wider bandgap, the embedded depth and the end of the plate dimensions are the key parameters which can be adjust to isolate Rayleigh surface waves at different frequency ranges. The barrier with I-shaped cross-section has better isolation performance and saves material than that with uniform cross-section. The gradient and piecewise gradient wave barrier broadens the frequency attenuation domain significantly, covering the frequency range of Rayleigh surface waves from 1.5 to 20 Hz. Waves with larger wavelengths have been controlled by the designed sub-wavelength barrier which effectively shields the structures from Rayleigh surface waves in low frequencies.