Replacing ageing steel bridges, industrial structures and support frameworks is often expensive, disruptive and material-intensive. Researchers at Empa are exploring how Wire Arc Additive Manufacturing (WAAM) can provide a more sustainable solution. Instead of replacing damaged steel components, the technology repairs and reinforces them.

WAAM uses an electric arc to deposit welding wire layer by layer onto damaged areas. This process creates customised three-dimensional metal reinforcements. Unlike conventional welding, WAAM allows engineers to produce reinforcement shapes that improve how forces move through a structure. As a result, repairs require less material while extending the service life of existing steel components.

Optimised Geometry Extends Service Life

The researchers found that the shape of the reinforcement is more important than the amount of added material. According to Empa researcher Hossein Heydarinouri, well-designed reinforcement geometries can slow down or even stop the growth of fatigue cracks.

During tests at Empa, the team reinforced cracked steel plates with different WAAM geometries before exposing them to repeated loading. Every repaired sample performed better than an unrepaired reference plate. Two-layer stepped reinforcements delivered the best results. In collaboration with ETH Zurich, the researchers showed that these optimised designs can increase the fatigue life of damaged steel plates by up to four times.

The study also revealed that geometry must be carefully designed. Poorly shaped reinforcements can create new stress concentrations where the printed metal meets the original steel. This can reduce the long-term performance of the repair.

Supporting More Circular Steel Construction

Fatigue cracks are among the most common forms of damage in steel structures. WAAM allows engineers to add material only where it is needed. This reduces material use, energy consumption and repair costs. At the same time, it extends the lifespan of existing infrastructure. The approach supports circular construction by preserving valuable structures and avoiding unnecessary replacement.

Today, WAAM mainly relies on large industrial robotic systems, which limits on-site repairs. However, researchers expect portable robotic systems to make the technology more practical for maintenance projects in the future.

Looking Beyond Repairs

The research team is also investigating how metal 3D printing can create entirely new structural solutions. By combining optimised geometries with shape memory alloys (SMAs), engineers can develop metal components that absorb energy during extreme loads and recover their original shape afterwards. Such components could improve the earthquake resistance of bridges and buildings or reduce vibrations in technical installations.

The researchers also see opportunities in mechanical engineering. Metal 3D printing makes it possible to manufacture lightweight, highly stressed components with complex geometries. Combined with numerical simulations and advanced materials, WAAM could lead to more efficient and resource-conscious steel structures.

Source & photos: Empa