基于径向不变假定的现浇大直径管桩纵向振动响应频域解

假定各物理量沿径向不变化，建立了低应变瞬态集中荷载作用下现浇大直径管桩振动响应的计算模型和波动方程。采用Laplace变换法，求得了波动方程的频域解析解，采用Fourier逆变换求得了时域响应。将文中解计算结果与三维频域解析解进行了对比分析，文中解的入射峰-反射峰时间差与三维频域解差别很小，说明对于PCC桩这种大直径薄壁管桩，采用径向不变假定对计算结果几乎没有影响。因此，在PCC桩低应变检测波形分析时，采用基于径向不变假定的二维解是完全合理的。将文中二维频域解的计算结果与二维时域解的结果进行了对比分析，结果表明，2种解在入射波、第一个桩底反射波、第二个桩底反射波峰值大小和到达时间非常吻合，这说明考虑环向位移与否对计算结果没有太大的影响，研究PCC桩低应变动力响应的问题时忽略水平方向的位移是完全可以的。

Frequency domain solution of vertical vibratory response of large diameter pipe pile based on radial invariability assumption

The computational model and wave equation of dynamic responses of large diameter pipe pile in low strain integrity testing are established based on radial invariability assumption. Combined the initial conditions and boundary conditions, the analytical solution of wave equation in frequency domain is obtained by Laplace transformation method. The dynamic responses in time domain are obtained by Fourier inverse transformation. The comparison of the analytical solution in this paper with results of three-dimensional(3D) frequency domain solution indicates that the time difference between incident and reflected waves has little distinction. The radial invariability assumption has little effect on two-dimensional (2D) frequency domain solution for a large diameter thin wall pipe pile; so it is reasonable to analyze waveform of low strain testing by 2D theory. The comparison of the 2D frequency domain solution in this paper with 2D time domain solution indicates that the results of two methods can match well each other. The circumferential displacement has little effect on numerical results; so the horizontal displacement need not be considered in waveform analysis of large diameter pipe pile.