As celebrations marking the 50th anniversary of the Forth Road Bridge reached their peak in September, a team from the Cambridge Centre for Smart Infrastructure and Construction (CSIC) prepares to meet future engineering challenges facing the Scottish landmark.
The 2.5km long-span suspension bridge, which connects Edinburgh to Fife, now carries far more traffic than it was originally designed for, with more than 24 million vehicles crossing this section of the Firth of Forth each year.
During inspection of the cables in 2004, extensive corrosion was discovered in the strands making up the main suspension cables. The Scottish Government decided to build a new road bridge, the Queensferry Crossing, due to open in 2016, which will run alongside the Forth Road Bridge and adjacent rail bridge, commonly referred to as the Forth Bridge.
Although the traffic load on the old FRB will reduce significantly when the new Queensferry Crossing cable-stayed bridge opens, there will still be a requirement for ongoing monitoring of the structure.
Professor Campbell Middleton and the CSIC bridges team believe the work the Centre is undertaking to develop and demonstrate wireless sensor network (WSN) technology may have a role to play in monitoring various key structural elements on this bridge. However, one of the problems delaying the adoption of WSN, particularly in difficult-to-reach areas, is the need to change batteries on a regular basis.
In a bid to solve this issue, CSIC’s Dr Yu Jia and Dr Ashwin Seshia have developed a novel vibration energy harvester which will make the need for batteries obsolete. This patented device has demonstrated the potential to generate substantially more power than devices based on more conventional approaches to vibration energy harvesting.
Vibration data, collected from the Forth Road Bridge during a field investigation, is now being used by Dr Jia to optimise the harvester for a trial deployment at the bridge early next year.
Professor Middleton said: “As vibration energy harvesting improves and the amount of energy available to power sensors increases, new radio technologies are emerging with lower power requirements. We may be approaching the point at which a vibration powered wireless sensor network, needing no battery change, becomes a reality. This would be a world first.”
The low cost, wireless, self-powered/battery free sensors will enable CSIC to measure the behaviour of key structural elements on this critical piece of infrastructure, giving the owner a far greater understanding of the actual capacity and level of safety of the bridge.
Professor Middleton continued: “The Forth Road Bridge offers a fantastic opportunity to test this innovative technology which will provide key information to the bridge owners and managers, leading to knowledge and reassurance of its on-going safety performance, which could see the Forth Road Bridge surviving a further 50 years or more.”