PSI - Issue 17

João Morais et al. / Procedia Structural Integrity 17 (2019) 448–455

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João Morais et al. / Structural Integrity Procedia 00 (2019) 000 – 000

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1. Introduction

Railroad infrastructures suffer degradation on its initial geometry during their lifetime usage, largely due to successive passages of vehicles, but also due to other phenomena like atmospheric conditions. In practice, rails relative position is no longer the most appropriate and thus creates, for example, geometry defects that negatively affect the overall system performance. Railroad maintenance is one of the aspects of railway infrastructure management activity that most influence the technical and economic performance of this transport system, either because it involves huge funds, or because it has significant impacts on system availability. Adequate maintenance management should include decision-making based on the knowledge regarding system degradation and failures, usually obtained by visual inspection and auscultation of the railway. Traditional approaches of assessing railroad conditions, such as those based on the standard EN 13848 (2019), are quite effective in identifying sites that negatively affect the functional and structural performance of the railway, but they do not provide useful information regarding the causes that led to this performance degradation. Consequently, maintenance actions tend to be more corrective in nature than preventive or predictive, which negatively influences the efficiency of infrastructure management. In an attempt to improve railway assessment methods, some authors have proposed that the analysis of geometric condition should not just be based on comparisons between the geometric parameters values usually measured and their maximum values. It should include the dynamic response of the system, in particular the railway-vehicle interactions and vehicle velocity (Paixão et al., 2015). Over the past few decades, there has been a surge of interest on the scientific and technical communities regarding the measurement of railway vertical deflection and its vertical stiffness. Vertical stiffness influences the carrying capacity of railway and its response regarding the passage of vehicles, thus representing an important parameter to evaluate geometric quality degradation of the railway and their respective maintenance costs (Le Pen et al., 2016; Quibel et al., 2010; INNOTRACK, 2008). Considering the limitations of the current methods, a research project named COURSE was implemented by LNEC in partnership with Mota Engil, Engenharia e Construção. S.A.. This project aimed at designing, developing and demonstrating the applicability of an innovative and integrated approach to assess railway performance. It also contributed to identify the causes of railway degradation, taking into account aspects related to the structural response of the dynamic interaction between railway and vehicle. The developed approach should enable continuous evaluation of railway functional and structural parameters, with the use of an instrumented railway vehicle. This should allow for the proposed system to operate without disturbing railway infrastructure operations, thus providing a more efficient solution. Under this project, a system prototype was developed and embedded into a self-propelled vehicle, with the following functionalities: • Evaluation of vertical deformation and vertical stiffness variations of the railway throughout its length; • Detection of disturbances in the dynamic contact interfaces between the vehicle and rails; • Post-processing of the obtained data, providing on-board and on-demand relevant information regarding railway defects and overall condition. This paper includes an overall system description of the prototype implemented based on the proposed approach and the first experimental tests performed with the prototype, regarding system assessment and calibration. These tests were performed on a railway track, adjacent to a maintenance yard. The track was instrumented with additional on-site equipmen t to serve as reference for the prototype’s assessment. The data obtained from the preliminary tests suggest that the proposed approach is adequate in this context.

2. Overall prototype system description

The proposed railway vertical stiffness evaluation method is based on measurements of railway vertical deformation, due to the weight of the instrumented vehicle, relative to the chassis of the vehicle. By measuring the distance between the middle section of the vehicle and the railheads areas directly below, assuming those railheads areas are sufficiently apart from the wheels and thus not deformed by the presence of the vehicle, it is possible to