Siena, Italy is home to the world’s first major footbridge built from Outokumpu’s LDX 2101® duplex stainless steel.
Thinking the future
The project is the result of successful interplay between an enlightened design engineer, farsighted community leaders and Outokumpu. The lead designer for the bridge, Mr Pierangelo Pistoletti, speaks about two passions that he harbors: one is for bridges, and the other is for stainless steel. He is fascinated about bridges because of their challenging structural complexity and about stainless steel because of the superior solutions that the material presents to the structural challenges.
Stainless all the way
“Mild steel poses a risk for critical structures, because without regular coating the structures can be attacked by serious corrosion, leading to material fatigue and even to a risk of collapse. Regular coating to fight corrosion is also costly,” Mr Pistoletti explains. When the City of Siena in Tuscany commissioned him to design a footbridge over a busy motorway in the suburb of Ruffolo, he and his engineering firm SETECO went to work on an all-stainless steel, cable-stayed bridge. The process took a new turn when Outokumpu’s Italian marketing arm introduced SETECO to a new material: LDX 2101 duplex stainless steel developed by Outokumpu and produced by no other stainless steel maker.
Lean duplex brings savings
Outokumpu LDX 2101 is a lean duplex grade that provides the excellent properties of duplex stainless steels with a nickel content of just 1.5%. The grade is ideal for load-bearing structures where moderate corrosion resistance is adequate such as in Siena, an inland city with low pollution levels. Mr Pistoletti was persuaded by the merits of the material and specified LDX 2101 for the towers and roadway of the bridge. Siena city representatives were no less impressed, attracted to the long, maintenance-free life and unfading good looks that the material promised. The high strength of LDX 2101 enabled Mr Pistoletti to design a light-weight structure compared to traditional bridge designs.