Insights on maximising the longevity
of the marine infrastructure.
As a part of the design plan for Webb Dock, Colin Trewern, a Senior Maritime Engineer at Jacobs, and our very own Dean Ferguson dived into making a case for durability amidst marine structures and surfaced with the David Whitby Best Review Paper award at the Australasian Corrosion Association, Corrosion and Prevention Conference 2016, hosted in New Zealand. One morning by the waterfront, we engaged these gentlemen in a conversation, learning about their findings and discussing the industry at large. We bring to you insights from their paper in an excerpt.
“Is it possible to build a structure that ‘never’ corrodes?”, we ask.
“It is possible, yes. Although there is inevitably a cost involved”, Dean Ferguson explains. He elaborates, stating this can be achieved through correct materials selection, for example, some reinforced concrete structures are designed to last over 300 years, using high grades of stainless steel reinforcement and specialist cementitious materials. Furthermore, cathodic protection systems and coatings can be applied during or after construction to maximise the durability of a structure. With the help of durability and materials specialists that analyse the structure's environment, select appropriate materials and identify construction-related durability risks, such longevity is not hard to achieve.
The real devastating impact of deterioration is felt when maintenance cost increases well before the time it was budgeted for. Colin Trewern explains that when this deterioration compromises the overall integrity of a structure, extensive remediation or premature replacement is required. If left untreated these structures represent not only potential safety risks but threaten billions of dollars in losses to national economies.
This argument brings us to the gist of their paper, which reflects on modern engineering practices seeking infrastructural solutions that are low maintenance, durable and last for an extended span of time. At the very core of this decision lies a designer’s choice of materials that meet both structural and long term durability needs.
“When considering the design of a structural asset, the ease of future remediation or replacement of individual elements is an important factor in identifying the preferred approach to durability”, Colin suggests.
Dean describes ‘Sheet Pile Walls’ to be one such example for which replacement during a structure’s life is often either impractical or improbable. He states, “Sheet pile walls are often subject to aggressive environments. Exposed to a combination of submerged, tidal, atmospheric and buried environments, they can also be subject to impact and abrasion during the service life.” The initial choice of material, therefore, can be key to achieving the desired durability.
We determine that the key challenge for designers is to think outside the box about ways to enhance sustainability and durability. While doing so, they are often met with the conflict of choosing a traditional construction material over a new technology. While a traditional material may have limitations, it is usually widely studied due to its long usage history. Colin and Dean make a case for identifying and reviewing a number of alternative non-metallic sheet pile materials and products which are available in the market.
Colin adds, “While the durability and structural design risks associated with traditional metallic sheet piles are well known and a standardised design approach exists, these unfamiliar materials come with their own risks and limitations, particularly when considering their structural design capacity.”
“The use of polymeric materials for retaining walls in a marine environment eliminates the occurrence of traditional deterioration mechanisms associated with reinforcement and mild steel, including the aggressive ALWC. However, it introduces a different set of deterioration mechanisms to be considered by designers. The durability of available products can be difficult to assess, with manufacturers utilising propriety admixtures and formulations. Available long term durability information is often only for generic materials class”, argues Dean.
The Australasian Corrosion Association (ACA) brings together some of the industry’s finest academics and professionals in all aspects of research and implementation regarding corrosion, providing access to the extensive knowledge base that promotes and develops best practices in planning, impact and management of infrastructure.
As a result of their research and knowledge development, Infracorr and Jacobs have published this paper through the ACA in the hopes that their study will guide future designers in implementing a non-standard approach to maximise the durability of their marine assets. The paper can be a powerful resource for anyone who would like to access information about design challenges including potential durability risks to be considered with specific material types, as well as the impact of different material properties (both long and short term) of structural design.
DEAN FERGUSON is the Engineering Manager at Infracorr Consulting. Dean has experience undertaking durability design for major marine infrastructure projects and has also been involved with undertaking structure condition assessment and remedial design of existing structures in the marine, water/wastewater and buildings sectors. An active member of Australasian Corrosion Association, Dean is the Vice President of the Victorian Branch of the ACA and is a past Chairman of the national Young Corrosion Group Steering Committee.
COLIN TREWERN is a Senior Maritime Engineer in Jacobs’ Melbourne office. He has 35 years’ experience specialising in the planning, design, documentation and project management of public infrastructure projects, particularly relating to maritime works. His experience includes feasibility studies, condition assessments, design, project management and construction supervision of maritime related works. This has involved the design and documentation of reinforced concrete, steel and timber maritime structures, and the preparation of technical and construction specifications.
If you'd like a copy of the paper, contact
Dean Ferguson at dean.ferguson@infracorr.com