Dynamic Response of Railway Track Resting on Variable Foundation Using Finite Element Method

At high train speed, differential settlement of railway track arises due to the variation in stiffness and yield characteristics of foundation along its length. In the present study, the effect of nonhomogeneous elastic foundation on dynamic response of railway track due to a moving load is studied. The railway track is modeled as an infinitely long beam on nonhomogeneous elastic foundation subjected to a moving load. The foundation stiffness is varying harmonically, about a mean value, along the length of beam. The dynamic response is obtained using a finite element (FE) approach. Adequacy of the proposed FE model is ascertained by comparing the FE results with the results available in the literature. The comprehensive new results are obtained to quantify the effect of amplitude (ε) and wavelength (λ) of harmonic foundation on the dynamic response of beam. The peak displacement of beam increases with ε, λ and velocity. It is further shown that for harmonically varying foundation, higher-order harmonics are significantly present in the response making it irregular. Also, the critical velocity (V_cr) is considerably affected by ε and λ. The variation of peak displacement with velocity is found to be irregular and instead of a distinct peak at V_cr, a plateau is obtained, implying that for a range of velocities peak displacement is quite high. This is also demonstrated through modal mass contribution by a large number of modes. The FE model used in this study can be naturally extended to predict the differential track settlement by including yielding characteristics of foundation.