Dynamic interaction between a railway freight vehicle and a switch and crossing (S&C) is studied by simulations of vehicle dynamics. In particular, the influence of a stochastic spread (scatter) in traffic parameters on damage in the S&C is assessed. The considered parameters are wheel profile and wheel–rail friction coefficient. To form a database for sampling, 120 wheel profiles from freight wagons in regular traffic have been measured and categorised with respect to wear. Among the investigated parameters, it is shown that equivalent conicity is the wheel profile parameter correlating best to damage in the S&C panels. The influence of hollow worn wheels on damage is also investigated, and it is found that such wheel profiles display a different running behaviour at the crossing transition. Convergence properties for samples of runs generated by Latin hypercube sampling (LHS) are compared with the corresponding properties obtained by pure random sampling. It is concluded that the LHS-generated samples exhibit similar or smaller variance in damage compared with the randomly generated samples.

A methodology for the simulation of track settlement in railway turnouts (switches and crossings, S&C) is presented. The methodology predicts accumulated settlement for a given set of traffic loads using an iterative and cross-disciplinary procedure. The different modules of the procedure include (I) simulation of dynamic vehicle–track interaction in a turnout applying a validated software for multibody vehicle dynamics considering space-dependent track properties, (II) calculation of load distribution and sleeper–ballast contact pressure using a detailed finite element model of a turnout that includes all of the rails (stock rails, switch rails, closure rails, crossing nose, wing rails and check rails), rail pads, baseplates and sleepers on ballast, (III) prediction of track settlement for a given number of load cycles and (IV) calculation of accumulated track settlement at each sleeper and the resulting vertical track irregularity along the turnout which is used as input in the next step of the iteration. The iteration scheme is demonstrated by calculating the track settlement at the crossing when the studied turnout is exposed to freight traffic in the facing move of the through route.

Inspired by a manufacturing process of switch rails for railway turnouts, a method for the optimisation of switch rail profile geometry is presented. The switch rail profile geometry is parameterised with four design variables to define a B-spline curve for the milling tool profile, and two design variables to prescribe the deviation from the nominal vertical path of the milling tool. The optimisation problem is formulated as a multi-objective minimisation problem with objective functions based on the contact pressure and the energy dissipation in the wheel–rail contact. The front of Pareto optimal solutions is determined by applying a genetic type optimisation algorithm. The switch rail profile designs are evaluated by simulations of dynamic train–turnout interaction. It is concluded that the obtained set of Pareto optimal solutions corresponds to a rather small variation in design variables where increased profile height and increased profile shoulder protuberance are preferred for both objectives. The improvement in the objectives comes at the cost of an earlier wheel transition to the switch rail and thus increased vertical loading at a thinner rail cross-section. The performance of the optimised geometry is evaluated using a set of 120 measured wheel profiles, and it is shown that the optimised geometry reduces damage also for this large load collective. It is concluded that accurate limits on switch rail loading need to be established to determine the feasible design space for switch rail geometry optimisation.

A numerical method for robust geometry optimisation of railway crossings is presented. The robustness is achieved by optimising the crossing geometry for a representative set of wheel profiles. As a basis for the optimisation, a crossing geometry is created where rail cross-sectional profiles and longitudinal height profiles of both wing rails and crossing nose are parameterised. Based on the approximation that the two problems are decoupled, separate optimisations are performed for the cross-sectional rail profiles and the longitudinal height profiles. The rail cross sections are optimised to minimise the maximum Hertzian wheel–rail contact pressure. The longitudinal height profiles are optimised to minimise the accumulated damage in the wing rail to crossing nose transition zone. The accumulated damage is approximated using an objective criterion that accounts for the angle of the wheel trajectory reversal during the transition from the wing rail to the crossing nose as well as the distribution of transition points for the utilised wheel profile set. It is found that small nonlinear height deviations from a linear longitudinal wing rail profile in the transition zone can reduce the objective compared to the nominal design. It is further demonstrated that the variation in wheel profile shapes, lateral wheel displacements and the feasible transition zone length of the crossing will determine the longitudinal height profiles of the wing rail and crossing nose if all wheel profiles are to make their transition within the transition zone.