Investigation of lateral track panel stiffness through four-point bending tests

Abstract

Lateral track stability in ballasted tracks is mainly given through lateral ballast resistance and track panel stiffness. Nowadays this becomes even more important due to widely spread application of continuously welded rails. The lateral ballast resistance is hardly to control, changes over time and is influenced by many environmental factors. On the other hand, a high lateral track panel stiffness was found to be beneficial for curve breathing and buckling. Despite this importance, the empirical knowledge is poor and a general overview is missing in literature. To overcome this issue, four-point bending tests were performed on all the rail tie combinations currently in use in Switzerland. Four-point bending tests were chosen due to their ability to estimate bending and shear deformation separately. The stiffness was calculated from the measured force and displacement data based on the Timoshenko beam theory. The differences in stiffness are discussed based on the mechanical behavior of the track panel. Based on the results high and low stiffness superstructure types can be distinguished. It was found that the lateral track stiffness in case of coupled concrete (ZSX) ties can be increased up to a bending stiffness of 84600 kNm2 and a shear stiffness of 10435 kN compared to a bending stiffness of 2440 kNm2 and a shear stiffness of 3773 kN as present for conventional concrete ties. The limitations in terms of stiffness of every superstructure type as well as possible improvements are given.