In the UK, there are around 74,000 bridges on the local road network and 30,000 on the rail network (includes tunnels and viaducts). Many of the bridges on the rail network date back to the Victorian era and require regular maintenance. Likewise, many of the bridges on the local road network also require regular maintenance. In a study by the RAC Foundation in 2018, 4.6% of the bridges on the UK road network were deemed sub-standard. The cost of repairing the sub-standard bridges is estimated at £934 million.
Traditionally bridges, come with a high life cycle cost, requiring repair every few decades. Typically S355 steel is used in highway bridges, while S275 is used in railway bridges. Pedestrian bridges often use painted carbon steel. The coating on such bridges often requires maintenance on average every 30 years. Many specifiers and stakeholders are looking at ways to save on lifetime cost and thus maintenance by using different materials in bridges. Advances in recent years have demonstrated that Stainless Steel as a material in bridges can offer the most cost-effective long term solution.
Image courtesy of Outokumpu
Outokumpu – A Mill Producing Duplex Stainless Steel Grades
Outokumpu are experts in production of Duplex Stainless Steel. The high strength of duplex steels mean that a lightweight bridge can be designed. Their product offering covers 9 product ranges that include Austenitic, Ferritic, Duplex and Martensitic Stainless Steel grades. Stainless Steel is 100% recyclable, corrosion-resistant, maintenance-free, durable and hygienic and therefore an ideal material for demanding applications such as bridges, chemical tankers, oil & gas energy industry applications and flanges & valves.
Image courtesy of Outokumpu
Optimising Material Procurement in Bridges through Duplex Stainless Steel
Duplex Stainless Steel was first used in the UK as a main structural material in a bridge in 2001. Since then engineers are beginning to recognise the benefits that are offered through the use of Duplex Stainless Steel in bridges. Duplex Stainless Steel provides a solution that minimises disruption, maintenance and lifecycle cost. As local governments and transport authorities become increasingly aware of lifecycle costs of bridges, many are looking to reduce the lifecycle cost. One way to reduce the cost is by specifying Duplex Stainless Steel in bridges. Here are some of the benefits:
1. High Strength and Corrosion Resistance
Many types of Duplex Stainless Steel, including Forta LDX 2101 provide high strength and corrosion resistance. Which, in turn, allows engineers to build a lightweight bridge that is long-lasting and requires minimal maintenance. Different grades of Duplex Stainless Steel have different levels of corrosion resistance, and the grade selected can be tailored to the environmental conditions.
2. Low Lifecycle Cost
A bridge built using Forta LDX 2101 can have a lifespan of over 120 years with little requirement for maintenance. In comparison, the initial investment of Stainless Steel is higher than that of Carbon Steel. In the long run, however, Stainless Steel is more cost-effective as a Carbon Steel bridge would need to be repainted, while a wooden bridge can require replacement in 30 years.
Stainless Steel (specific grades) offer an ideal solution for rebar in bridge piers that comes into contact with saltwater as Stainless Steel resists corrosion. When chlorides find their way through the concrete, the rebar minimizes concrete spalling that would take place with corroded Carbon Steel. Stainless Steel rebar would also require less concrete cover to protect it from seawater.
Stainless Steel bridges also offer sustainability benefits. As Stainless Steel does not require shot-blasting, repainting and repair, the material doesn’t pollute the environment. Stainless Steel is a green product, 100% recyclable and has a minimal impact on environment in comparison to other materials. Environmental Product Declarations with necessary data to perform a material environmental impact and life cycle analysis are available to here.
Lifetime Cost of Carbon Steel vs Stainless Steel Bridges
How is the Lifecycle Cost of a Bridge Calculated?
This is the total cost associated with a bridge from the initial feasibility study through engineering, construction and regular maintenance and repair, all the way to end-of-life decommissioning and recycling.
In the short term, Carbon Steel offers a cheaper alternative to Stainless Steel as a material in bridges. However, over the lifetime of a bridge, Stainless Steel offers a more cost-effective solution.
- A Stainless Steel bridge can have a lifespan of over 120 years with little need for maintenance.
- Maintenance is required on painted Carbon Steel every 10-30 years, depending on the environment
- Furthermore, Carbon Steel bridges require repainting every few years which with appropriate grade selection is not necessary on a Stainless Steel bridge
If you have an upcoming bridge project, contact our technical advisory team here.