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Corrosion Management of Aging Steel Bridges



Author(s)

Narendra Tripathi

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DOI:10.17265/1934-7359/2024.11.005

Roads and Maritime Services, Transport for NSW, Haymarket NSW 1240, Australia

A significant portion of the sum spent by asset managers in maintaining steel bridge assets is dedicated to corrosion management of aging steel bridges, particularly very old ones. Managing corrosion of such bridges poses unique challenges owing to the inherent complexities associated with design, material, fabrication and construction. Steel bridges have come a long way from being constructed of cast iron and wrought iron in the early days to modern day low carbon high strength steel bridges. During inception of steel bridges in Australia, wrought iron was used extensively in deck structure whereas piers were generally constructed of cast iron. Some of these piers have been found to be suffering from graphitisation. Even though CP (cathodic protection) has been proven to enhance the life of steel and reinforced concrete structures by preventing any further corrosion, there is little evidence to validate its success in preventing graphitisation of cast iron piers. Early steel bridges in NSW (New South Wales) were constructed with a complex geometry involving riveted cellular box girders, later simplified to riveted trusses. For any rehabilitation work to begin, the challenges start at the investigation stage. Due to cellular box type construction, thorough inspection and examination of inside of the boxes is generally not feasible even with the use of the available state-of-the-art investigation techniques. Some of the steel bridges in service in NSW are more than 120 years old. Any rehabilitation effort for such bridges faces challenges in terms of design methods to be used, availability of compatible material, selection of an appropriate method of joining e.g. welding or bolting, selection of a compatible protective coating, accessibility for the work to be carried out, etc. This paper describes common forms of corrosion observed on bridges. It demonstrates the difficulties in maintaining old bridges using two case studies.

Corrosion, management, aging, steel bridges, cellular box, cast iron.

Journal of Civil Engineering and Architecture 18 (2024) 545-551 doi: 10.17265/1934-7359/2024.11.005