Overhead structures play a vital role in the operation of any electrified rail networks. They support overhead electrical wires that provide the necessary power to the operation of trains. In Victoria Australia, there are approximately 13,000 overhead structures. Overhead structures are simple steel structures that lack redundancies and failure in a single location may cause complete collapse. These steel structures are exposed to the environment and gradual deterioration of steel due to corrosion jeopardize their strength and serviceability. Structural assessment is labour-intensive, while maintenance is costly and often requires interruptions to train service. Therefore, the prediction of the infrastructures’ structural performance plays an important role in the when and where to maintain and repair the structures. As the major objective, this research attempted to develop a method to time-dependently evaluate overhead structures and the assessment was applied to each critical structural part. The outcomes can be used for prioritization of different levels of structural assessments such as visual inspection, measurement, testing or instrumentation. To achieve these objectives, condition assessment of nearly 100-year-old overhead structures was initially conducted to find out the structurally critical parts and matched with numerical structural analysis. Extensive experimental work, which consisted of tensile test, remaining thickness measurement, scanning electron microscope and energy-dispersive X-ray spectroscopy, was implemented to study the deteriorated material scientifically. Finite element analysis was also applied to rivet connection to simulate its strength subject to corrosion-induced deterioration. Subsequent to this, various time-dependent deterioration models subject to corrosion-damage were developed to predict the capacities of steel structural connection and structural members. They were based on the yield line theory, corrosion rate model and corrosion decay model. With the utilization of the newly proposed deterioration models and industrial design guideline, structural reliability analyses were presented for portal overhead structure and single mast overhead structure. The result was expressed by time-dependent reliability index and probability of failure. It was found that the bending of structural members, bridge-mast connections and mast base connections are the most critical parts. The shearing of structural members owns the least concern over time. The significance of this study is the development of time-dependent deterioration models of steel structural connection and structural members. Innovatively, it is combined with the proposed deterioration models and structural reliability theory to scientifically predict and assess railway overhead structures.
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