Railway crossings are essential components of the railway track system that allow trains to switch from one track to another. Due to the complex wheel-rail interaction in the crossing panel, crossings are vulnerable elements of railway infrastructure and usually have short service lives. The crossing damage not only results in substantial maintenance efforts but also leads to traffic disruptions and can even affect traffic safety. In the Netherlands, the annual maintenance cost on railway crossings is more than 50 million euros. Due to the lack of monitoring systems, the real-time information on crossing condition is limited. As a result, the present maintenance actions on railway crossings are mainly reactive that take place only after the occurrence of visible damage. Usually, such actions (repairs) are carried out too late and result in unplanned disruptions that negatively affect track availability. In the Netherlands, around 100 crossings are urgently replaced every year, accompanied by traffic interruptions. Also, there is a considerable number of crossings with the service life of only 2-3 years. The maintenance methods used by the contractors on such crossings are somewhat limited and usually ended up with ballast tamping. In this case, the root causes of the fast crossing degradation are usually not resolved, and the crossings are still operated in degraded conditions after the maintenance. In order to improve the efficiency of the current maintenance of railway crossings aiming for better crossing performance, the goal of this study is to develop a monitoring system for railway crossings using which the crossing condition can be assessed, and the sources of the degradation can be detected. Using such a system timely and proper maintenance on railway crossings can be provided. The main steps in achieving this goal were as follows: Based on the measured dynamic responses of railway crossings due to passing trains, several condition indicators were proposed; To provide the fundamental basis for the proposed indicators a numerical model for the analysis of vehicle-crossing interaction was developed; The effectiveness of the proposed indicators was demonstrated using the data from long-term monitoring of 1:9 and 1:15 crossings. The railway crossing conditions can be reflected in the changes in the dynamic responses due to passing trains. In this study, the responses were obtained from the crossing instrumentation and wayside monitoring system. The responses reflect the wheel-rail interaction, which consists of the wheel impact accelerations, impact locations and the rail displacements due to the impacts, etc. Based on the correlation analysis of the responses, the indicators related to the wheel impact, fatigue area and ballast support were proposed. The indicators form a basis for the structural health monitoring (SHM) system for the railway crossings. To verify the effectiveness of the proposed indicators, and to explain the experimental findings, a numerical vehicle-crossing model is developed using the multi-body system (MBS) method. The model is validated using the measurement results and further verified using the finite element (FE) model. The proposed indicators and the MBS model were applied to the condition stage identification and damage source detection of the crossings. The main outcomes are presented below. In the condition monitoring of normally degraded crossings, the proposed indicators were capable to catch the main degradation stages of the railway crossing ranging from newly installed to damaged and repaired ones. With the assistance of these indicators, the maintenance actions can be timely applied before the occurrence of severe damage. The proposed indicators can also be used for assessing the effectiveness of the performed maintenance (repair welding and grinding, ballast tamping, etc.). It was demonstrated that ballast tamping has no positive effect on the performance of the monitored 1:9 crossing. The proposed indicators can also help to detect the root causes of the crossing damage. In some cases, the degradation is caused by adjacent structures, and therefore the maintenance should be performed not on the crossing itself but of the track nearby. In this study, the fast degradation of the monitored 1:9 crossing was found to be caused by the lateral track deformation in front of the crossing. The numerical results confirmed the phenomenon that the train hunting motion activated by the track deviation. It was the source of the extremely high impacts recorded by the monitoring system that ultimately resulted in the fast crossing degradation. By knowing the damage sources, proper maintenance can be performed rather than the currently used ineffective ballast tamping. Additionally, it was found that crossing degradation can also result from external disturbances. It was proven that highly increased rail temperature due to the long duration of sunshine would amplify the existed geometry deviation in turnout. Considering the high sensitivity of wheel-rail interaction in the crossing, higher standards for crossing maintenance and construction are required for better crossing performance. This study contributes to the development of the condition monitoring system for railway crossings. The application of the condition indicators is a big step forward for the current maintenance philosophies from damage repair to predictive maintenance, and from “failure reactive” to “failure proactive”. The outcomes in this study will contribute to the better performance of railway crossings.
|Qualification||Doctor of Philosophy|
|Award date||2 Dec 2020|
|Publication status||Published - 2 Dec 2020|
- railway crossing
- condition monitoring
- degradation detection
- maintenance guidance