Introduction to Railway Track Design

In railway tracks the stresses and deformations induced by their own weight are negligible if compared to those deriving from thermal and vehicle loads. The latter can be distinguished into: quasi-static loads (weight force, centrifugal force and wind-induced force); dynamic loads, imputable to the effect of geometrical irregularities of the track and the rolling surface (wear, joints, points and crossings, etc.) or to defects on the surface of wheel rims. The ballasted tracks are designed by imposing that the deflection in the subgrade is always in an elastic or plastic field. The subsidences occurred during the track service life must remain below given threshold values in order not to jeopardise functionality and safety of the railway line. The criteria for calculating ballasted tracks are synthetically examined in this chapter and are based on the procedure described by Esveld [1]; for more detail, the interested reader may refer to [2, 3, 4].