New Sensing Techniques for Improved Assessment of Rail Infrastructure

Abstract

As demand grows for rail transportation, so too does the stress on Canada’s rail infrastructure, and improved monitoring technologies are needed to prevent track failure and assist in the bridge rehabilitation process. Currently, most quantitative methods of stress detection disrupt service traffic and are impractical for widespread implementation. Thus, there exists a need for sensor systems that can facilitate more comprehensive condition assessments of rail infrastructure. This thesis investigates the potential for discrete and distributed strain sensors to fulfill this objective. The buckling or breaking of continuous welded rail due to constrained thermal movement leads to derailments and is currently largely undetectable. Thus, there is a requirement for novel sensing tools capable of identifying these issues. In response to this, a series of laboratory tests were performed to assess the ability of two fibre optic sensors (FOS) to measure axial strain in rails under various boundary and environmental conditions. The presence of temperature-induced error on measured strains led to the development of thermal correction factors for each technology and fibre combination tested. The application of these factors in subsequent laboratory and field tests demonstrated their necessity for successful long-term rail monitoring with FOS. The combination of discrete and distributed strain sensors have the potential to improve current monitoring techniques for railway bridges. To investigate this, two experimental campaigns were undertaken on a steel railway bridge in North Bay, Canada, with the added intention of investigating longitudinal force transfer and the effect of traction bracing, installed as part of the structure’s rehabilitation. Data from both pre- and post-rehabilitation tests suggested that most axial force in the rail is distributed over its length, rather than being transferred immediately into the superstructure and that the bridge experienced undesirable bi-axial bending. Furthermore, data from the post-rehabilitation tests suggested that the added traction bracing did not affect the behaviour of the bridge. Finally, a full-scale three-dimensional finite element model of the instrumented bridge span was developed to aid in the understanding of the bridge’s behaviour due to both gravity and longitudinal loads.