Barron River (Kuranda) Bridge: Stage 1 Investigations and Repairs

Abstract

Far North Districts majestic Barron River Bridge, located at the top of the Kuranda range, Kennedy Highway near the popular tourist area of Kuranda, about 25 minutes out of Cairns has been getting lots of attention. In late October 2020, TMR inspectors noted fatigue cracks in some steel elements on the bridge. The cracks are likely caused by many years of heavy vehicles using the bridge, which carries heavier loads than the original designers anticipated. The issue is not unusual in steel bridges of this age but requires a collaborative approach to be managed. As a precaution TMR reduced the bridge to one lane, under traffic control, to manage the load on the bridge while inspections were carried out. By directing traffic down the centre of the bridge, loads were lower and the weight spread more evenly, which also reduces the risk of cracks growing. And then began a media frenzy in October 2020 and a robust stakeholder communication exercise. Construction on the bridge began in the early 1960's. The bridge is a 257-metre-long, high-level bridge. Comprises of 6 spans with a reinforced concrete deck carried on steel plate girders. The old timber bridge adjacent is preserved under water. The river level rose as a result of the hydro scheme built downstream in the Barron Gorge. Work on site is affected by the Savannah way which passes under the Southern Abutment. A group of displaced people had also established a camp under the southern abutment and Pedestrian movements were consistent around the site. RoadTek were asked to manage the installation of instrumentation and movement strain gauges. Upon installation a calibrated 42.5m semi was passed over the bridge with traffic control at varying speeds to check the instrumentation. Safety and Environmental compliance of the site was complicated by the lead paint removal. Hundreds of individual welds on the bridge mainly from the Under-Bridge Inspection Unit have been strengthened. It was a time-consuming exercise, as the paint needed to be removed from the weld before it could be assessed. The non-destructive testing and the actual welding of 150 splice plates, including heat packs and detailed weld records were completed as planned in October 2021 Aurap were commissioned to analyse the instrumentation strength results and provide a final report detailing the effectiveness of the welding operations. Rehabilitation of the bridge will ensure operational success.