The role of stiffness variation in switches and crossings: Comparison of vehicle–track interaction models with field measurements

Abstract

The performance of switches and crossings compared with plain line is complicated by the presence of movable parts, changing rail geometry and non-uniformities in the composite and/or trackbed stiffness. These features lead to complex vehicle–track interactions and higher maintenance costs. The trackbed stiffness is the least well-controlled engineering property. A greater variability in trackbed stiffness leads to higher differential trackbed settlement and associated poorer track quality. At switches and crossings, changes in trackbed stiffness are exacerbated by changing rail properties which also contribute to changes in the overall composite track stiffness. This work focuses on the role of variations in stiffness on the performance of switches and crossings. Field measurements of bearer displacement were carried out using geophones at a switch and crossing equipped with under sleeper pads. The vehicle–switch and crossing interaction was modelled using a multi-body system and finite element method. The trackbed stiffness along the whole of the switch and crossing was inferred using the measurements of track deflections in an iterative back-calculation taking account of changing rail properties. It is shown that not including the variation in trackbed/composite stiffness leads to significant under/overestimates of the wheel–rail contact forces. Under sleeper pads are shown to reduce absolute maximum loads, but may increase the variation in deflection.

Evaluation of Numerical Simulation Approaches for Simulating Train–Track Interactions and Predicting Rail Damage in Railway Switches and Crossings (S&Cs)

“…A common form of validation is the comparison of qualitative results of dynamic outputs such as normal and lateral contact forces and Von Mises stress against corresponding outputs from validated models in the literature. Direct validation includes comparing simulation contact forces and rail accelerations with field measurements [42,59,64,130], the comparison of measured and simulated transition regions [59] and the comparison of degradation (wear/plastic deformation) depth against field measurements [19,65] as well as sleeper displacements [81]. Calibration-based model validation includes fine-tuning of material properties against load tests as well as the calibration of substructure dynamics using rail receptance [29,42,128].…”

Finite element analysis of a crossing panel under dynamic moving load – effect of support conditions and implications on foot fatigue

“…This section describes different aspects of finite element modelling of the crossing panel. The contact load history is taken from Grossoni et al 36 model which captures the dynamic interaction between the travelling unsprung wheelset mass and the flexible track. This contact force is then applied directly to the FE model, thus gaining simplicity and time of execution.…”

“…The properties of the bearers are based on the reinforced concrete reported in. 41 Note that the wheel load corresponds to the payload of a typical passenger coach wheel as reported in 36 and does not represent the highest load applied on such crossing.…”

“…The crossing angle is 1 in 13 and the model is made using detailed drawings of a CEN56 weldable manganese cast centre block (CCB) crossing commonly used in the UK and previously studied by the authors. 14,36 The input loading history is taken from the work performed by Grossoni et al 36 For the stress analysis, the focus is on the foot of the crossing where the material behaviour is expected to be elastic, and where several failures have been reported. 37 The model is compared and validated against site measurements in the UK 38 in 2016 and 2019, measured on the down line of a double railway track crossover equipped with under sleeper pads (USPs).…”

Efficient time–frequency approach for prediction of subway train-induced tunnel and ground vibrations

“…However, this model is based on periodic transformation of a reference cell, and it is still difficult to simulate the vibration caused by singular defects (e.g., joints, switches, crossings). 12 All the models mentioned above are derived from the frequency domain. However, if the time domain approach is adopted, the simulation of the train–track interaction will become significantly more flexible.…”