Research on important bridge for ore traffic provides new knowledge

Earlier this summer, the Autio Bridge, which crosses the Torne River in Pajala municipality, became a valuable research site for researchers at Luleå University of Technology. The bridge, which has been subjected to heavy ore traffic from the Kaunisvaara mine for several years, gave the researchers a unique chance to collect data on how prestressed concrete bridges age - a construction type found throughout the country.

- We have tested how the prestressed structure has been affected by many years of heavy traffic and what this means for load-bearing capacity and service life. The bridge also had to meet new load requirements from mining transportation. It is unusual to be able to measure a bridge without intervention and then confirm the results by opening the structure, says Gabriel Sas, Professor of Civil Engineering at Luleå University of Technology.

The researchers at Luleå University of Technology have followed the Autio Bridge since 2020 and carried out extensive measurements just before the demolition in the summer of 2025. The Autio Bridge had then reached the end of its technical life and would be replaced to meet today's design requirements.

The Autio Bridge had extensive cracking and traffic was restricted due to the increased loads from mining in the area. The replacement of the Autio Bridge is part of the strengthening measures being carried out by the Finnish Transport Agency along road 395 between Svappavaara and the Kaunisvaara mine. Kaunis Iron uses road 395 to transport iron ore concentrate from the mine to the transshipment station in Svappavaara, for further transportation of the iron ore to Narvik.

An opportunity to see what's happening inside the bridge

With advanced measurement technology, the researchers at Luleå University of Technology recorded how the bridge reacted to heavy traffic. Since it was going to be demolished anyway, the researchers could inspect the inside after the demolition and compare the results. The work now continues with laboratory analysis of extracted concrete cores and additional measurements to confirm and deepen the results.

- The biggest challenge with this type of bridge is that it is difficult to see what is happening inside the bridge. Regular inspections often miss hidden damage. By combining the measurements with actual visibility, we can improve future assessments and maintenance strategies, especially in areas with heavy traffic. The data we collect is crucial for older bridges to remain safe and sustainable, says Angelica Maria Agredo Chavez, PhD student in Civil Engineering at Luleå University of Technology.

Tests provide valuable insights

- The collaboration with Luleå University of Technology has worked very well. For us who are responsible for demolition and new construction, this type of testing provides valuable knowledge about how existing structures work after many years of heavy traffic. It helps us to plan and implement similar projects more efficiently, says Oscar Seppelin, site manager at GRK, the main contractor for the project.

The old bridge has now been replaced by a collaborative solution: concrete supports in the river and on land, steel beams that are pushed into position, and a cast concrete roadway. A temporary bridge is open to traffic, demolition is underway and work on the foundations for the new bridge is ongoing. The new bridge is planned to open to traffic at the end of September 2026.