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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level while being highly corroded at the anchorage (bed log) area. • For the stays which were anchored using bed logs, a clear relationship was observed between the condition of the bed log and the degree of corrosion in the stay. For the significantly corroded stays at the bottom end of the specimens, even the bed logs seemed to be degraded in most cases. Degradation of the bed log suggests the availability of moisture and air as well as microbial activity at that below ground depth and these factors could result in accelerated corrosion rates of the stays. • Maximum percentage in reduction of the cross-sectional area were found to be at the bottom of the specimens except for pole equipment #21 which showed around 51% area reduction close to the ground level of the specimen. Except for the abovementioned specimen, all the other stays showed a percentage reduction in cross sectional area below 16%. It was ascertained that the particular stay rod #21 had an unusual situation where the stay wire was wrapped around the stay rod with an Aluminium sleeve. It is possible that the corrosion cell created by dissimilar materials is responsible for this unusual corrosion. • From the observations of the corrosion patterns of the bed log anchored stays, it is evident that the corrosion could be initiated at the region of the bed log. Specially, CCA treated timber is known to be very aggressive on both zinc and steel when the moisture content exceeds 20%. Following suggestions and recommendations can be made based on the aforementioned observations • Based on the results of the inspected specimens, it can be suggested that, inspecting ~300mm depth below the ground level for buried stays may not provide a representative assessment of the extent of the corrosion and the remaining cross-sectional area (which is related to the remaining strength) of the ground stays. • In general, it is suggested that the bed logs hold the moisture which facilitates the corrosion in the stay. Moreover, the soil type and the change in the depth of the water table have significant effects for the corrosion rates. Sandy soils where the water gets drained easily will have slow corrosion rates in contrast to clay and other water retaining soil types which will have accelerated corrosion rates. Acknowledgements Authors would like to acknowledge the valuable contributions of the industry partners, who provided essential design information, drawings, and approved the field inspections and cable stay uprooting processes. References Bandara, S., Rajeev, P., & Gad, E. (2023). Power Distribution System Faults and Wildfires: Mechanisms and Prevention. Forests , 14 (6), 1146. Bandara, S., Rajeev, P., & Gad, E. (2023). A review on condition assessment technologies for power distribution network infrastructure. Structure and Infrastructure Engineering , 1-18. Darestani, Y. M., Shafieezadeh, A., & DesRoches, R. (2016). An equivalent boundary model for effects of adjacent spans on wind reliability of wood utility poles in overhead distribution lines. Engineering Structures , 128 , 441-452. Francis L and Norton J., “Australian timber pole resources for energy networks: a review.,” Queensland: Department of Primary Industries & Fisheries, 2006. Marcus, P. (Ed.). (2011). Corrosion mechanisms in theory and practice . CRC press. Melchers, R. E. (2018). Progress in developing realistic corrosion models. Structure and Infrastructure Engineering , 14 (7), 843-853. Presuel-Moreno, F., Jakab, M. A., Tailleart, N., Goldman, M., & Scully, J. R. (2008). Corrosion-resistant metallic coatings. Materials today , 11 (10), 14-23. Revie, R. W. (2008). Corrosion and corrosion control: an introduction to corrosion science and engineering . John Wiley & Sons Romanoff, M (1957). Underground Corrosion, Gaithersburg, MD. doi: 10.6028/NBS.CIRC.579. Southwell, C. R., Bultman, J. D., & Alexander, A. L. (1976). Corrosion of metals in tropical environments. Final report of 16-year exposures. Materials Performance (MP) , 15 (7). Victorian Bushfire Royal Commission (2010). Final Report Summary–2009 Victorian Bushfires Royal Commission. Victoria, Australia:Parliament of Victoria Zamanzadeh, M., Kempkes, C. D., Aichinger, D., & Riley, D. (2007). Laboratory and field corrosion investigation of galvanized utility poles. In Electrical Transmission Line and Substation Structures: Structural Reliability in a Changing World (pp. 235-249).