考虑竖向荷载影响的大直径管桩水平振动响应解析解

建立了黏弹性地基中受轴力作用的现浇大直径管桩水平振动响应计算模型,通过引入势函数对土体振动方程进行解耦,结合桩土耦合条件求得了桩顶复阻抗解析表达式。将该解退化到不考虑竖向荷载的水平振动响应解与已有理论解对比,验证了该解的合理性。通过算例分析,研究了竖向荷载、激振频率和桩长对管桩桩顶水平复阻抗、桩身位移和内力的影响,研究结果表明:复阻抗实部和虚部在桩土系统固有频率处均发生共振;竖向荷载使管桩位移和内力发生重分布,竖向荷载为零时,位移、弯矩和剪力最大值均出现于管桩中上部,随着竖向荷载增大,其最大值均出现于桩底;桩身水平位移随频率变化而变化,管桩中下部转角、弯矩和剪力受频率影响较大;桩身中下部位移和内力受桩长影响大于桩身其他部分;无桩芯土时桩顶水平位移和转角比桩芯土存在时大。

Analytical solution of lateral dynamic response of a large diameter pipe pile considering influence of axial load

The horizontal vibration model for a large diameter pipe pile subjected to axial load in viscoelastic soil is established. The potential functions are adopted to decouple the governing equations of the soil. Analytical solution of the impedance of the pipe pile is obtained based on the assumption of perfect contact between the pile and the soil. This analytical solution can be perfectly simplified to the horizontal vibration solution of pipe pile without axial load, which demonstrates the validity of the solution deduced in this study. Numerical examples are presented to analyze the influences of axial load, excitation frequencies, and pile lengths on the complex impedances, displacements and internal forces. The results show that the complex impedance resonates at the inherent frequency of the pile-soil system. The vertical loads cause the redistribution of the displacements and internal forces of the pipe pile. The maximum displacement, bending moment and shear stress are located at the upper part of the pile shaft when the vertical load is 0, however, they move to the pile bottom gradually with the increase of the vertical load. The horizontal displacement of the pipe pile varies with the frequency. The changes of rotation angle, bending moment and shear force are obvious at the lower part of the pile shaft. The influences of pile length on displacement and internal force at the middle and bottom parts of the pile are more significant than those in the other parts. The displacements located at the upper part of the pile shaft without inner soil are larger than those with inner soil.