Keywords: track modulus, track system dynamics, finite element analysis, railway track stiffness, prestressed concrete sleepers, flexural rigidity.

Today there is a general trend to increase load capacity and train speeds in railway transportation all over the world. This paper tries to investigate the effect of variation in train speeds and increase in load capacity on the dynamics of existing Indian railway lines so as to pave the way for safer and smoother transportation. In the present work, dynamic analysis of the model of a typical Indian Railway track system has been done, with special emphasis on "track modulus". The analysis of the track system has been done using the commercially available finite element package ANSYS. A comprehensive static analysis of the track system has been done for validation of the finite element track model. Computation of dynamic track stiffness and track modulus from harmonic loading of the track at different frequencies has also been attempted to predict the track displacement and acceleration response. These studies have been extended to determine the influence of wheel flats on the track modulus. Such work has not been reported in literature. In this work two types of track systems as per broad gauge specification of Indian Railways have been analyzed. The track specifications are laid down by Research Design and Standards Organisation (RDSO). The 52PSC and 60PSC track systems consist of an 'I' rail cross-section with masses of 52 and 60 kg respectively per metre length of the rail. The rails in these tracks are supported by prestressed concrete sleepers. The track (rail and sleeper) super structure is covered with ballast, which in turn rests on the subgrade (soil). The track moduli have been computed using MATLAB. Corresponding to a constant (gross) axle (static) load of 25 tonnes, a load of 6.25 tonnes is applied at four nodes on the top surface of the rails, for the computation of the track modulus. As a first step in the dynamic study, eigenpairs were extracted from two types of prestressed concrete sleeper track models and analysed. Subsequently, the two prestressed concrete sleeper track systems were excited (with the dynamic loads being given at the same excitation locations as for the static analysis) over the range of frequencies 0 to 300 Hz to predict the displacement and acceleration at the loading points. A constant (gross) axle load of 40 tonnes has been applied at the rails for the dynamic analysis.

From the parametric analysis it is seen that there is noticeable difference in the displacements between 52PSC and 60PSC track models. The harmonic analysis reveals that the average track (dynamic) modulus is around 100 MPa for the PSC track system. From the transient analysis, it has been proposed that if the vehicle with wheel flats is running on tracks having track modulus values much greater than 100 MPa, then the resulting ballast settlement is more than allowable, necessitating repair or replacement of the worn out wheel.

purchase the full-text of this paper (price £20)

go to the previous paper
go to the next paper
return to the table of contents
return to the book description
purchase this book (price £145 +P&P)