An old suburban railway bridge between Stockholm’s Old Town and the trendy district of Södermalm is being repaired by using stainless steel structures. The 174-meters-long Söderströmsbron consists of four railway bridges and is one of the busiest bridges in town. It is a vital part of the city’s subway and suburban railway infrastructure, with some 330,000 passengers daily.
The five-track carbon steel bridge, built in 1957, will be repaired for safer travel and higher traffic volumes in the future. Old bridge beams underneath the rails will be changed to that of a stainless steel structure within a timeframe of two years, 2017–2018.
“It’s a one-meter-tall pre-fabricated beam structure consisting of two beams for each track, connected by a truss structure. We deliver altogether 600 tonness of high strength Forta duplex stainless steel to the project, explains Mladen Perkovic, Head of Outokumpu Plate Service Center Nordic in Degerfors, Sweden.
Outokumpu delivers ready-made beam trusses to the renovation project. The heavy plates to be welded to finished beams come from Outokumpu’s rolling mill in Degerfors. Outokumpu’s partner Stål & Rörmontage AB fabricates the final bridge components, which are then lifted to their places by a crane on a pontoon.
The new girders in high strength duplex stainless steel Forta LDX 2404 minimize the need for maintenance. “Stainless steel beams will pay off within 30 years when anticipating the repainting of the carbon steel beams. All maintenance can be done on the spot so no road closures or traffic diversions are needed. This is very positive from the environmental perspective and a clear added value to the customer,” Perkovic points out.
Using stainless means that corrosion problems, typical to heavily used bridges such as this one on Lake Mälaren, are avoided altogether. “The life cycle of a stainless steel bridge is considerably longer than that of a traditional carbon steel construction. Stainless means a low carbon footprint and cost-effectiveness, and it looks good, too. I believe we’ll see a lot of stainless steel bridges in the future. This is just the beginning,” foresees Perkovic.