Summary
Researchers at Empa are developing a process called Wire Arc Additive Manufacturing (WAAM) to specifically repair fatigue cracks in steel components. Welding wire is printed layer by layer onto damaged areas using an electric arc, creating three-dimensional metal reinforcements with optimized geometry. In experiments, custom-tailored reinforcements extended the lifespan of cracked steel plates by up to four times. The process enables localized repairs instead of costly full replacement of permanently installed components in bridges and load-bearing structures.
People
- Hossein Heydarinouri (Empa, Structural Engineer)
- Maryam Mohri (Empa Materials Scientist)
Topics
- Steel construction and infrastructure
- Additive manufacturing
- Materials science
- Fatigue cracks and damage management
Clarus Lead
Aging infrastructure is becoming a challenge: fatigue cracks endanger bridges and load-bearing structures daily, yet replacing permanently installed components is often economically unrealistic. Empa research offers a practical solution through geometrically optimized metal reinforcements that deliberately redirect stresses and stop crack propagation – without full replacement. While laboratory results are convincing, scaling to construction sites remains the central implementation obstacle: mobile robotic systems for on-site repairs are not yet production-ready.
Detailed Summary
The WAAM process operates on a principle opposite to classical welding work. Rather than merely connecting components, the robotic arm creates a three-dimensional material buildup – similar to plastic 3D printing, but with metal. The decisive advantage lies in geometry: two-layer, graduated reinforcement structures distribute stresses so effectively that cracks do not continue to grow. In extensive load tests in the Empa construction hall, all reinforced samples showed significantly higher fatigue lifespan than untreated comparison plates – some extended by up to four times.
However, the research also highlights limitations: poorly chosen geometries can create new stress concentrations at transitions between base material and printed metal. This makes precise structural design absolutely necessary. Empa researcher Heydarinouri emphasizes: "Shape is much more important" – not the amount of material.
Practical application currently fails due to mobility constraints. Industrial robotic systems are stationary and difficult to transport; damaged components would need to be brought to workshops – often impossible in reality. Initial approaches for portable systems exist, but require further development. WAAM is currently realistically deployable only for easily accessible components or during planned maintenance work.
The research team is simultaneously developing follow-up applications: combining intelligent geometries with shape memory alloys could enable metallic damping elements for earthquakes or vibrations. In mechanical engineering, geometrically optimized lightweight components promise weight savings while maintaining load-bearing capacity.
Key Statements
- WAAM enables targeted steel construction repairs through layer-by-layer metal buildup with optimized geometry
- Laboratory results show up to fourfold lifespan extension of cracked steel plates
- Practical scaling requires mobile robotic systems for on-site deployment – technologically not yet production-ready
- Future applications: adaptive damping elements and lightweight components in mechanical engineering
Critical Questions
Evidence: How representative are laboratory results for real bridge loads? Were environmental factors (corrosion, temperature fluctuations, dynamic loads) incorporated into the experiments?
Scalability: What technical and economic barriers currently prevent the development of mobile WAAM systems? Are there cost projections for portable solutions?
Causality: Is the fourfold lifespan extension primarily attributable to geometry or to the material properties of the printed layers? Were control experiments conducted with other reinforcement methods?
Risks: What long-term effects can occur at transitions between base material and printed metal? How is quality control ensured on-site?
Economic Viability: At what damage size does WAAM become more cost-effective than full replacement? Are lifecycle analyses available?
Transfer Risks: How do requirements differ between laboratory geometries and real, often more complex components in situ?
Source Directory
Primary Source: Crans-Montana Fire Disaster – https://www.news.admin.ch/de/newnsb/ve9reG5apGj_wq-S7UZTx
Supplementary Sources:
- Empa Press Release WAAM – https://www.empa.ch/web/s604/waam-bruecken
- Empa Department of Structural Engineering – https://www.empa.ch/web/s303
Verification Status: ✓ 25.06.2026
This text was created with the support of an AI model. Editorial Responsibility: clarus.news | Fact-Check: 25.06.2026