A Dynamic Vehicle-Track Interaction Model for Predicting the Track Degradation Process

Due to the repeated passage of trains, differential settlements are observed in the vertical direction of the railway tracks. These settlements depend on the platform quality, on the train speed, on the dynamic load, and on the track structural behavior. In recent years, several authors have defined laws and models for the prediction of settlement. The majority of those settlement models only consider the vertical degradation of the track, disregarding this phenomena in the lateral direction, since the vertical track geometry deteriorates faster than the horizontal one. In these models also the dynamic nature of the vehicle load is not considered accordingly. This paper presents a vehicle-track dynamic-interaction model for predicting the evolution of the vertical track profile and assessing the track response along the degradation process. The model is one-dimensional (1D) and it estimates the track degradation from a settlement law that uses deformation under instantaneous wheel passage as input. Although track degradation is a three-dimensional (3D) process, a 1D model is considered because the vertical component of the track settlement is the largest one. In order to predict the evolution of the track settlement due to the passage of the dynamic loads on the track, an iterative procedure is proposed. One cycle of this methodology is composed by three phases: numerical calculation of the train-track dynamic-interaction loads along the track, calculation of the track settlement, and definition of the track profile after settlement. Then, a new cycle begins. The proposed methodology is applied to a real track profile, measured in a Portuguese railway line, in order to understand the influence of the dynamic nature of the load on the track, the influence of the settlement rate and the influence of the type of vehicle on the evolution of the vertical track profile. The dynamic response of the track over time due to the evolution of the real vertical profile is evaluated through a vehicle-track dynamic-interaction approach. The attained results reveal the importance not only of the track irregularities, but also of the vehicle speed and characteristics on the evolution of the track profile. The numerical simulations presented in this paper evidence the potential of the proposed methodology, which can be used as a tool to forecast track settlement and to estimate the dynamic response of the track along the degradation process. (C) 2014 American Society of Civil Engineers.