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. They opted for a novel design with a composite structure that achieved both these aims. The bridge is constructed using both duplex stainless steel and fiberglass.Thanks to its high mechanical strength, the use of duplex allows reduced thickness and hence weight compared to traditional materials. The duplex grade family also meets the corrosion resistance requirements in all climatic conditions, so no coatings are required and maintenance is reduced throughout the life of the bridge.
Compared to conventional bridge types, Pedelta achieved significant weight savings with the innovative combination of high-strength stainless steel and lightweight fiber-reinforced plastics. They were able to design the bridge for a service life of 120 years. The Zumaia bridge is the first of its kind in the world.
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 Outokumpu 2205, a molybdenum-containing grade that withstands the harsh environment created by airborne sea salt.
Prefabricated for quick assembly
The bridge construction itself was undertaken by Spanish 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 can provide all stainless bridge components as custom-designed parts, prefabricated for quick assembly at the site. This allowed ASCAMON to concentrate on their core task.
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. The benefit to ASCAMON was cost-efficiency and superior ease in project management.