Ask The Expert: Andy Backhouse

This week, we speak to Andy Backhouse, Technical Manager at Outokumpu. Andy has over 25 years of experience working in the Stainless Steel industry with particular expertise in the application of Stainless Steel in Bridges. If you are involved in the technical specification of bridges, read on for insights on sustainability, life cycle cost optimisation and much more:

What are the overall benefits of Stainless Steel in bridges over Carbon Steel?

Stainless Steel has several benefits over Carbon Steel. As well as long term aesthetic appearance, the superior corrosion resistance means little or no maintenance over a long lifespan.

What applications are Stainless Steel bridges most suitable for?

Duplex Stainless Steel has been used in a number of aesthetically pleasing bridges such as The Helix in Singapore but there is a growing use in functional bridges. The modular pedestrian bridge over the E4 road, Sweden is one example where long life and minimal maintenance were as important as a simple & functional appearance. Bridges in coastal locations or where de-icing salt is used can benefit immensely from the high corrosion resistance. Applications where maintenance is difficult or costly, such as bridges associated with railways, can benefit from the long life and low maintenance requirement.

With a focus on sustainability increasing, are there any sustainability benefits associated with Stainless Steel over Carbon Steel?

Very much so. Outokumpu produced Stainless Steel typically has an >85% recycled content. With the correct grade choice, it can be expected to last over 120 years and is 100% recyclable at the end of its life. The high strength of Duplex Stainless means that the weight of steel can be reduced, reducing the amount of embodied carbon. Outokumpu Stainless Steel produced in Europe is focused on using low carbon sources of energy, meaning the carbon footprint is less than a third of the Stainless Steel industry average figure. The data for this can be found in our Environmental Declaration of Performance certificates.

Does Stainless Steel fare better aesthetically compared with other types of steels?

Yes, it does! The Folke Bernadotte Bridge won the Stockholm Building of the Year 2020, but the important thing is that it will continue to look award-winning. The Millennium Bridge, York and Celtic Gateway Bridge, Holyhead are just two examples of bridges that look like new 15 – 20 years after being built. Although not a bridge, the Stainless cladding of the Chrysler Building, New York looks stunning in the sunlight and has had little maintenance in 90 years.

 

Folke Bernardotte bridge – Images courtesy of Outokumpu

How can design be optimised of bridges to save time and money?

Studies have shown that using the relevant Eurocodes and utilising the additional strength of Duplex over S275 and S355 Carbon Steel, a significant weight reduction can be achieved. In one study by Arup, the steel weight saved in an example steel-concrete composite road bridge was 39%. Many bridges today are designed with lives up to  120 years meaning that the long lifespan with significantly reduced maintenance cost can give dramatic life cycle cost savings – especially when maintenance is difficult or when bridge closures are difficult to coordinate. Duplex was chosen for the four Söderstöm rail bridges in Stockholm and the life cycle cost savings over painted Carbon Steel were shown to be €60m.

 

Source: Arup and Outokumpu

 

If you have an upcoming bridge project, contact our technical advisory team here.

 

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