World’s first robotically welded automated bridge: The Ya Bridge, Norway

The choice of SSAB Weathering ML steel by Statens vegvesen, the Norwegian Public Roads Administration, stems from the steel’s exceptional impact toughness, particularly in colder temperatures. This advantage is attributed to its lower carbon content, which also ensures excellent weldability – making it an ideal candidate for laser welding. Weathering steel was also selected for its capacity to substantially reduce maintenance expenses over the bridge’s entire service life by eliminating the need for painting. The specific location of the project played a pivotal role in this decision. Due to the low humidity levels and the bridge's placement over the Ya River, weathering steel became the preferred option for advanced corrosion protection. These conditions ensured that the steel's attributes align perfectly with its task, while eliminating the risk of paint pollution in the river.

In a world first for an automobile bridge, the Ya Bridge was fully fabricated using automated laser welding robots, which delivered strong, precise connections. The robotic welding was further aided by digital twins and 3D modeling. This approach enabled a faster, more cost-effective, and eco-friendly method of bridge construction compared to traditional methods. The new welding technique used in the bridge construction creates joints with improved fatigue properties in comparison with conventional welded seams, and may in the future allow for thinner steel sections.

The easy maintenance of weathering steel played a crucial role in the customer's decision-making process. Its natural properties simplify bridge upkeep, resulting in a longer-lasting and more efficient structure. SSAB Weathering steels extend a bridge's lifespan with minimal maintenance needs. If painted, maintenance repainting intervals for weathering steel can be twice as long as for other types of steel, effectively cutting maintenance costs in half.

SSAB Weathering steel is recognized for providing a cost-effective, corrosion-resistant solution for demanding projects, like bridges. The next-generation thermomechanically rolled weathering steel not only saves costs due to corrosion resistance and the elimination of painting, but also reduces fabrication time thanks to its excellent weldability and superior impact toughness. The unpainted surface of weathering steel develops a patinated layer over time due to weather variations, forming a protective barrier that retards corrosion. Rust accumulates in the outermost layer of the steel, transforming it into a protective layer that shields against further corrosion. This not only reduces the bridge's maintenance costs but also eliminates the emissions that come from painting. 

The chosen steel, SSAB Weathering in grade of 355 (S355J5W+M), coupled with SSAB's thermomechanically rolled weathering steel, makes the bridge's construction more efficient and environmentally friendly. This innovative steel enables seamless welding without preheating – accelerating the manufacturing process and conserving valuable energy resources. Its exceptional impact resistance – even under temperatures as low as minus 50 degrees Celsius – coupled with its extended fatigue endurance, positions it as the ideal material for meeting the demands of rigorous bridge structures.

The use of thermomechanically rolled steel not only made welding and assembly on-site smoother but also seamlessly aligned with the use of robotic laser welding technology. This combination eliminated the necessity for preheating the steel components during assembly, which in turn made the construction process more streamlined and added to the project's overall environmental efficiency. It's important to note that this steel successfully underwent a series of rigorous tests, confirming its reliability and strength in real-world scenarios.

The manufacturing of the Ya Bridge by Prodtex has been characterized by high quality and lower energy consumption compared to traditional methods. Although weight reduction was not the central goal of this project, the potential of the steel was well understood. Pre-fabricated plates supplied by SSAB revolutionized the manufacturing process, enabling faster production, minimizing waste, and reducing logistical costs. This innovative approach not only improved construction efficiency but also mitigated environmental impacts. And the laser welding requires less energy and produces fewer CO₂ emissions compared to traditional welding methods. Prodtex AS's novel technique emerges as an environmentally friendly alternative, applicable not only to bridges but to various other steel structures. The Ya Bridge embodies the future of bridge construction, seamlessly merging innovation, sustainability, and efficiency.