We may be approaching the point at which a vibration powered wireless sensor network, with no need to change batteries, becomes a reality.
— Campbell Middleton
A team from the Cambridge Centre for Smart Infrastructure and Construction (CSIC) has designed vibration energy harvesters which convert ambient vibrations into electricity, eliminating the need for batteries and making remote monitoring of the long-span suspension bridge’s health much easier. A trial deployment of the harvesters will take place early next year.
The 2.5 kilometre-long Forth Road Bridge, which connects Edinburgh and Fife, now carries far more traffic than it was originally designed for. About 25 million vehicles now cross the bridge each year, nearly ten times the number it carried when it opened in 1964.
The increased strain that the additional traffic load has had on the structure became apparent during a routine inspection of the bridge’s cables in 2004, when extensive corrosion was discovered in the strands making up the main suspension cables.
After the damage was identified, the decision was made to build a new road bridge alongside the Forth Road Bridge and Forth Rail Bridge. The Queensferry Crossing is due to open in 2016, and traffic on the Forth Road Bridge will then be limited to buses, taxis, cyclists and pedestrians. Although traffic load will be reduced significantly when the new bridge opens, there will still be a requirement for ongoing monitoring of the older structure.
Professor Campbell Middleton and a CSIC bridges team believe the work they are undertaking to develop and demonstrate wireless sensor network (WSN) technology may have a role to play in monitoring various key structural elements on the bridge. However, one of the problems holding back the adoption of WSN, particularly in difficult-to-reach areas like underneath a busy bridge, is the need to change batteries on a regular basis. The issue is not the cost of the batteries themselves, but rather the cost of the human power to replace the batteries.
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Image: Forth Road Bridge, 7 Oct 12
Credit: Castaway in Scotland via flickr
Reproduced courtesy of the University of Cambridge
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