Monitoring and damage detection of a 70-year-old suspension bridge – Ölfusá bridge in Selfoss, case study

Ölfusá Bridge in South Iceland is located in the town of Selfoss on the ring road Route 1 in Iceland, approximately 50 km from Reykjavik. It is a suspension bridge across the Ölfusá glacial river and while being a very important link in the road transport network in Iceland, it also serves as a vital link for the community of Selfoss for both vehicles and pedestrians. Inspections of the main cables of the suspension bridge have indicated an inadequate level of safety due to corrosion, as well as significantly heavier traffic loads and increased self-weight due to rehabilitation of the bridge deck. A system identification of the bridge was conducted in 2012 and a permanent monitoring system was installed in 2014 with the aim of identifying changes in the structural performance of the bridge. The measurements have provided valuable information which are used in the operation of the bridge. The measured modal properties have been used to calibrate the FE models of the bridge, which are used for structural analysis and the structural reliability assessment of the bridge. The continuous monitoring of the cable forces gives the possibility of identifying changes in the structural response of the bridge in addition to the regular visual inspections.