Abstract: The application of 2.5D finite element method in the research on railway subgrade dynamic response is becoming more and more widespread. In order to solve the inefficient problem for calculating the dynamic response of subgrade under the random irregularity, a framework for fast calculation of dynamic response of subgrade based on reduced 2D Hermite interpolation is established. The interpolation principle is determined based on the characteristics of the dynamic response of subgrade in the frequency-wavenumber domain. Moreover, the influence of the distribution and number of interpolation points on the interpolation accuracy is discussed. The results indicates that the reduced 2D Hermite interpolation can greatly improve the computational efficiency in the calculation of subgrade dynamic response under the random irregularity. Compared with non-uniform distribution principle of interpolation points, uniform distribution principle can take into account both amplitude and phase interpolation accuracies and therefore is more suitable for 2.5D finite element method. Additionally, the computational efficiency of the present method is only related to the number of interpolation points, and is not affected by the number of random irregularity harmonics. It has obvious advantages in simulating the dynamic response of railway subgrade with random irregularity of track.

Key words: 2.5D finite element method, railway subgrade, response function, computational efficiency, 2D interpolation