With railway interoperability, new trains are allowed to move on the French railway network. These trains may present different designs from standard trains. This work aims to complete the current approach for vehicle admission on the railway network, which is defined in technical baselines. Historically, computation rules for traffic conditions are based on simplified analytical works, which are considerably qualitative. They have evolved through feedback and experimental campaigns to comply with the track structure evolution. An efficient methodology based on numerical simulation is needed to evaluate railway vehicle admission to answer this issue. A perspective to update these computation rules is to evaluate the structural fatigue in the rail. That is to say, fatigue is caused by bending and shear stresses. The complexity of the railway system has led to an investigation at first of the vertical response of the railway track and quantifying its contribution to the rail’s stress response. In that sense, this paper investigates the vertical track response to a moving railway vehicle at low frequencies. For this purpose, a lightweight numerical model for the track, a multi-body model for the vehicle, and a random vertical track irregularity are proposed. More explicitly, the track model consists of a two-layer discrete support model in which the rail is considered as a beam and sleepers are point masses. The rail pads and ballast layer are modelled as spring/damper couples. Numerical results show a negligible effect of track inertia forces due to high track stiffness and damping. Nevertheless, this assumption is valid for normal rail stresses but not for ballast loading, especially in the case of sleeper voids or unsupported sleepers. Hence, the prediction of the mechanical stress state in the rail for fatigue issues is achieved through a static track model where the equivalent loading is obtained from a dynamic study of a simplified vehicle model. A statistical analysis shows that the variability of the vertical track irregularity does not influence the output variabilities like the maximum in time and space of the normal and shear stress.

a lightweight numerical model of railway track to predict mechanical stress state in the rail maryam el moueddeb 1,2 , françois louf 1 , pierre-alain boucard 1 , franck dadié 2 , gilles saussine 2 , danilo sorrentino 2 1 lmt (ens paris-saclay/cnrs/université paris-saclay), france 2 sncf réseau, france abstract a new approach is conducted within sncf réseau to redefine and improve the current procedure behind rolling stocks admission. a perspective to update computation rules for traffic conditions is to consider track fatigue issues. in this sense, the study aims to provide a better knowledge of stress state induced by moving vehicles in rails through a lightweight numerical model of the track. specifically, the track model consists of a two-layer discrete support model in which the rail is considered as a beam and sleepers are punctual masses. the rail-pads and ballast layer are modelled as spring/damper couples. considering the track's vertical response, the study intends to quantify the impact of the vehicle's dynamic overload on the track response and verify the possibility of these overloads to excite track vibration modes. a first study considering constant moving loads already shows negligible effect of track inertia forces due to high track stiffness and damping. this justifies the prediction of mechanical stress state in the rail for fatigue issues through a static model of the track and a simplified dynamic model for the vehicle.