When the Öresund link between Sweden and Denmark opened in 2000, its bridge, tunnel and artificial island were given an estimated technical lifespan of 100 years. Since then, more than 150 million cars and 1.5 million trains have crossed it. In the EXTEND project, initiated with the link's operating consortium, researchers Sebastian Thöns and Ivar Björnsson of the Division of Structural Engineering at Lund University's Faculty of Engineering set out to establish whether it could keep operating until 2200.
The team modelled how steel and concrete degrade and how different maintenance strategies affect durability, then anchored those models in reality using the more than 5,500 sensors installed across the structure, recording vibration, temperature, humidity and movement. For the tunnel, updating chemical ingress models with measured data supported a significant life extension; for the bridge's critical inclined cables, continuous monitoring can reveal when intervention is genuinely needed rather than merely scheduled. The framework draws on utility-based decision analysis adapted from economics over more than a decade.
The conclusion is that both bridge and tunnel could last 200 years if inspected and maintained according to the project's strategies. The stakes extend well beyond one crossing: demolishing and rebuilding major infrastructure consumes vast quantities of material, money and embodied carbon, so doubling the life of existing structures is a climate measure as much as an engineering one. The researchers hope the sensor-updated, decision-analytic approach will transfer to ageing bridges, tunnels and other assets worldwide.