Duplex bridge in Bilbao, Spain

A bridge using duplex stainless steel as the main structural element is being constructed in Bilbao, Spain. The Abandoibarra footbridge will stretch for 143m across the Nervion River to connect the Guggenheim museum to the University of Deustro. It is designed to be both aesthetically pleasing and functionally sound. Construction will require about 500 tonnes of S32304 duplex stainless steel, manufactured by AvestaPolarit. S32304 contains 23% chromium and 4% nickel, with a microstructure containing roughly equal amounts of ferrite and austenite. The builders chose S32304 for the main structural elements of the bridge because of its unique combination of proof strength and corrosion resistance, says Bruno Garcia, managing director of AvestaPolarit’s Spanish office. This grade of stainless steel will give the 8-metre-wide bridge a life expectancy of more than 50 years by providing protection from corrosive seawater from the nearby Bay of Biscay and from exposure to other elements. Some bridges are covered with thin sheets of stainless steel cladding, but it is believed that Abandoibarra is the first bridge to use heavy steel plate for mechanical strength. AvestaPolarit hot-rolls the plates in Sweden then bends them into a U shape. The company delivers the plates to Vitoria, Spain, where they are welded together then transported to the site in Bilbao for assembly. The U-shaped structures are designed to support the topside of the bridge.