基于矢量匹配-劳斯法的群桩阻抗改进模型

采用薄层法算出群桩基础的频域阻抗，将群桩阻抗等效于一个单输入单输出系统，并表示为一个复数的频域传递函数。基于矢量匹配法（VF法），通过对传递函数拟合得到任意分层地基的群桩阻抗函数的集总参数形式。采用VF法对整体频域拟合，可以得到多项分式分式阻抗形式，进而扩展成为Wu-Lee模型。结果表明，VF法拟合得到的动力柔度函数可以精确地匹配分层地基动力柔度函数，由于多项分式的形式可以直接扩展成为Wu-Lee集总参数模型，且数值稳定。对于高频阻抗拟合需要采用高阶数，进行劳斯（Routh）降阶，得到较好的效果。

An improved model for dynamic impedance of pile groups based on vector fitting-Routh method

The dynamic impedance of pile groups in the frequency domain is computed by thin layer method. It is represented by the complex transfer function in the frequency domain as single input and single output system. The fitting of complex transfer function is proposed through the vector fitting method (VF method), so as to obtain the lumped-parameter model for pile groups in layered ground. The dynamic impedance of partial-fraction expansion type can be obtained by VF method; it fits over the whole frequency range, which is easily converted to the Wu-Lee model. It is shown that the lumped-parameter model by the VF method is accurately to match the dynamic impedance of pile groups in layered ground. Due to its partial-fraction expansion type，the expression can be conveniently transferred into the Wu-Lee model; and the fitting is numerically stable. The number of terms for the partial-fraction expansion is big when the dynamic impedance for the high frequency is needed to fit. The reduced order method called the Routh method is introduced to make the order reduced, and it is shown the result for the reduction is good.