This paper aims to investigate the effect of variable foundation stiffness on the dynamic response of an infinite railway track under the action of a harmonic moving load. In this study, harmonic variation in the foundation stiffness along the track length is considered. Here, the dynamic response of the finite element (FE) model is obtained with the help of Newmark Beta method using programming in MATLAB. It is ascertained that in the central region of the long FE model, the response is repetitive, thereby ensuring that boundary conditions do not influence the response in the central region. In this problem, two frequencies, i.e. frequency of moving load and the spatial frequency of variable foundation stiffness, are involved. Their combined influence on the dynamic characteristics such as resonant frequency, critical velocity, displacement time history, displacement below load, and bifurcation curve are investigated. It is shown that the dynamic response is qualitatively and quantitatively affected by the wavelength (λ) and amplitude (ε) of the variation of foundation stiffness. It is also shown that the important dynamic properties, i.e., the critical velocity and the resonant frequency reduce with the increase in wavelength of stiffness variation. This reduction is significant for the large amplitude of harmonic stiffness variation.

本文旨在研究变基础刚度对无限长铁路轨道在谐波移动载荷作用下的动力响应的影响。在这项研究中，考虑了地基刚度沿轨道长度的谐波变化。在这里，有限元 (FE) 模型的动态响应是在 Newmark Beta 方法的帮助下使用 MATLAB 编程获得的。确定在长有限元模型的中心区域，响应是重复的，从而确保边界条件不影响中心区域的响应。在这个问题中，涉及两个频率，即移动荷载的频率和变基础刚度的空间频率。它们对动态特性的综合影响，如共振频率、临界速度、研究了位移时程、载荷下位移和分岔曲线。结果表明，动力响应受到地基刚度变化的波长（λ）和振幅（ε）的定性和定量影响。还表明，重要的动态特性，即临界速度和共振频率，随着刚度变化波长的增加而降低。这种降低对于大幅度的谐波刚度变化来说意义重大。临界速度和共振频率随着刚度变化波长的增加而降低。这种降低对于大幅度的谐波刚度变化来说意义重大。临界速度和共振频率随着刚度变化波长的增加而降低。这种降低对于大幅度的谐波刚度变化来说意义重大。