STAINLESS STEEL BRIDGE - POOLEY BRIDGE CASE STUDY
Pooley Bridge is the UK’s first stainless steel road bridge over the River Eamont in Cumbria. This landmark structure measures 128ft long and reconnects the Ullswater valley with a permanent bridge. It was built to replace a stone structure built in the 18th century, destroyed in 2015 due to storm Desmond. The project required around 100tonnes of stainless steel plate for its construction.
The Pooley Bridge project had its complications since it was to replace an existing old stone bridge that was swept away in a storm.
Additionally, the new bridge needed to minimise the risk of future flooding, include traditional stonework, minimise the impact of construction on the river and allow people to see the landscape clearly.
Images courtesy of Outokumpu
Knight Architects proposed an aesthetic design using stainless steel and reinforced concrete. Duplex stainless steel was chosen as it is 25% stronger than S355 carbon steel, making it possible to create a slender design, allowing for an aesthetic structure that permits free flow of the river and avoids backing up during storms. The higher strength of this type of stainless steel and its inherent corrosion resistance also makes the bridge more tolerant of the impact of debris on occasions when the river level is high and fast flowing.
Additionally, the lighter weight of a stainless steel structure enabled straightforward construction and allowed for the entire bridge to be placed with a single lift without the need for a temporary support structure on the river. This helped minimise the effect of construction on the river and helped reduce the impact.
Stainless steel has several benefits over carbon steel that can prove extremely beneficial during the construction of bridges and adds to their longevity. Here are some of the main benefits of stainless steel in bridge construction:
Aesthetic Design and Longevity
Duplex stainless steel is 25% stronger than commonly used S355 carbon steel and is known for its long-term aesthetic appearance and superior corrosion resistance. The higher strength allows for a slender design, and the superior corrosion resistance ensures little to no maintenance over the long lifespan of the bridge.
Low Lifecycle Cost
Stainless steel can last for over 120 years with little maintenance. This brings down the lifecycle cost of the bridge compared to carbon steel that requires painting every few years. While the initial cost for stainless steel can be higher than carbon steel, it is more cost-effective in the long run.
Lighter Weight, Saving Time and Money
Due to the additional strength of duplex stainless steel over S275 and S355 carbon steel, significant weight reduction is achieved. This can help reduce the fabrication time and money spent on the project. It can also help to reduce the impact of construction on the river as the structure can be lifted and placed easily. A lighter weight minimizes the amount of material used and so reduces the carbon footprint.
Stainless steel is extremely sustainable and can be easily recycled. It has a long lifecycle, after which it is 100% recyclable. Additionally, Duplex stainless steel is produced by Outokumpu using low carbon sources of energy, reducing the carbon footprint to less than a third of the global average. Environmental data can be found in Outokumpu’s Environmental Declaration of Performance CERTIFICATES.
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The case study was compiled by OUTOKUMPU.