The small Basque city of Zumaia is located at the junction of two rivers that flow into the Bay of Biscay. The rivers slice through the city, so one crucial part of the development program is a footbridge to improve accessibility. The program’s project director and design agency Pedelta Structural Engineers looked for a type of bridge that would withstand Zumaia’s maritime climate but would be very lightweight at the same time. To achieve this the bridge is constructed using both duplex stainless steel and fiberglass. The duplex grade family meets the corrosion resistance requirements in all climatic conditions, so no coatings are required and maintenance is reduced throughout the life of the bridge. To find the right duplex grade, Pedelta turned to Outokumpu relying on a solid precedent: Outokumpu had helped Pedelta select the duplex grade for the world’s first all-stainless road bridge in the Spanish Mediterranean island of Menorca. The maritime environment of Zumaia prompted Outokumpu to advise Pedelta to use duplex 2205, a molybdenum-containing grade that withstands the harsh environment created by airborne sea salt. The bridge construction itself was undertaken by Spain-based steel fabricator Ascamon, which had previous experience in bridge building in stainless steel through the Menorca bridge project. Ascamon turned to Outokumpu, trusting them with delivery of the entire stainless steel package. Outokumpu’s plate service center PSC Nordic in Sweden cut and formed duplex plates from the adjacent Outokumpu hot rolled plate plant according to design drawings and prepared the edges for welding. The prefabricated sections were delivered directly to the site without intermediaries.
