PSI - Issue 64

Pat Rajeev et al. / Procedia Structural Integrity 64 (2024) 523–530 Author name / Structural Integrity Procedia 00 (2019) 000 – 000

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section of the steel rod leading to reduced load carrying capacity. The progression of corrosion over the service life can lead to a reduction in the load-carrying capacity, eventually falling below the design load. This deterioration may ultimately result in the failure of cable stays. Cable stay failures can lead to utility pole failures bringing the overhead cables and other attachments to the ground. Utility pole failures of this nature can potentially trigger bushfires, particularly during bushfire-prone weather conditions characterized by prolonged elevated temperatures, strong winds, and reduced ground moisture (Bandara et el., 2023). For example, a significant number of the Australian Black Saturday bushfires in 2009 were suspected to have originated from the failure of electricity assets. The resulting fires in Kilmore East tragically led to the loss of 119 lives (Victorian Bushfires Royal Commission, 2010). Thus, the failure of cable stays and utility poles have severe safety concerns and economic implications. Routine inspections are carried out to monitor the condition of these assets. Network managers specify the frequency of inspection cycles depending on their specifications. Typically, utility poles and cable stays are inspected every 3-5 years and the inspection frequency is higher for assets located in bushfire prone regions. In the course of these visual inspections, an excavation is performed ~300-400 mm below the ground level of the cable stay, allowing for a visual examination of the corrosion severity. However, there are a number of unknowns during these inspections which question the reliability of the results. No information is available regarding corrosion at the bottommost region of the steel anchor rod. Furthermore, it is important to note that uniform corrosion cannot be presumed along the entire length of the steel rod, as pitting corrosion may manifest at random locations. Moreover, it is challenging to ascertain whether the connection of the steel anchor rod to the bed log or other anchoring mechanisms is secure. Therefore, the objective of this study is to enhance understanding of the aforementioned aspects by uprooting a series of in-service cable stays and conducting below ground visual inspection and corrosion analyses. Analyzing the corrosion levels across the entire embedded section of the cable stay allows to determine whether inspecting ~300-400 mm below the ground depth of the cable stay is adequate to assess the extent of corrosion in the entire below-ground area. Further the protective steel coating thicknesses are measured to observe whether there is a loss in coating thickness over the service life of cable stays.

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Fig. 2. Anchoring mechanisms of the steel rod of the cable stay (a) Bed log anchor (b) Screw anchor

2. Steel corrosion Physical causes of metal deterioration are called as erosion or wear, which is entirely different to corrosion. Corrosion is the deterioration caused by chemical and electrochemical reactions of metals with its environment (Revie, 2008). Corrosion damage manifests in various forms, including rusting, cracking, or a reduction in strength. Consequently, it's important to note that corrosion damage may not always be visibly apparent, and the extent of damage cannot be accurately estimated solely based on weight loss (Marcus, 2011). However, corrosion types can be categorized into groups based on their outward appearance or the modified physical properties they induce (Revie, 2008). These are: • Uniform corrosion