Modelling the improved behaviour of a switch installed on ballast-asphalt track

Switches and crossings are a critical part of railway infrastructure and have a complex superstructure, creating variable support and bending stiffness along the track length. These variable structural and loading effects lead to faster rates of track geometry deterioration compared with plain line. Multibody vehicle-track interaction and finite element models combined with empirical predictions have been used to assess the likely benefits and improvements of using an asphalt layer combined with reduced ballast depth under S&C, in terms of long-term ballast differential settlement as well as in terms of reducing stress levels within the ballast and the subgrade layers. The assessment is primarily comparative against a baseline scenario site without asphalt layer. The introduction of asphalt track configurations reduced the variation in trackbed stiffness and increased stiffness throughout the switch panel. Using stressescalculated from finite element modelling, the ballast settlement was calculated using a semi-empirical equation to account for higher load cycles. The introduction of the asphalt layer reduced both maximum and differential settlements, originating from the ballast layer, in the switch panel with respect to the baseline scenario. Furthermore, the maximum stresses transmitted to the subgrade are generally reduced for both asphalt thicknesses with respect to the baseline

Analysis and prediction of high-speed train wheel wear based on SIMPACK and backpropagation neural networks

As train running speeds increase, the wheel-rail interactions of high-speed trains are becoming more complicated, and predicting and monitoring wheel wear are becoming increasingly important for the safe operation of high-speed trains. Therefore, identifying the critical factors that affect the wear of wheel-rail interactions and developing novel methods to predict wheel wear are of great importance. In this work, SIMPACK is used to establish a dynamic model of a high-speed train and to investigate the normal and lateral contact forces of the wheel-rail interfaces and the wear of the wheels for a train passing through a specially designed route that consists of straight-line, smooth-curved, and circular tracks. The wheel wear is predicted by means of the Archard wear model based on the SIMPACK analysis, and the wear is validated by a backpropagation neural network (BPNN) classification based on daily measured data provided by the Beijing Railway Administration. The results from the SIMPACK dynamic simulation and the BPNN classification show that the position of a wheel in a bogie has a significant effect on the wheel wear, but the position of a carriage in a train does not have a significant effect on the wheel wear. The findings from this study are very useful for the maintenance and safe operation of high-speed trains

Eur J Epidemiol

Few studies are available on atrial fibrillation (AF) burden at a whole country scale. The objective was to estimate the rate of AF patients newly treated with oral anticoagulants (OAC) in France each year between 2010 and 2016 and to describe age and gender differences. We used the French national health data system. For each year between 2010 and 2016, we identified patients aged over 20 initiating OAC. OAC indicated for the treatment of AF was determined by hospitalization diagnoses, specific procedures and registered long-term disease status, or a multiple imputation process for patients with no recorded information as to why they initiated OAC. Among the 421,453 individuals initiating OAC treatment in 2016, the estimated number of newly treated AF patients was 210,131, women accounting for 46%, patients under 65 years old 17%, and 21.4% of patients living in most deprived area. Age-standardized rates reached 400/100,000 inhabitants. Approximately 19% of patients were recently hospitalized for heart failure and 7% for stroke. Age-standardized rates increased by 35% over the study period in both genders, with a marked increase in patients under 55 (+ 41%) and those over 85 years old (+ 60%). Annual rates of AF patients newly treated with OAC increased by 35% between 2010 and 2016. Important differences in rates were observed according to age, gender and the deprivation level of the living area