Monitoring bridges, roads and pipelines with fibre optics

A new fibre optic sensor prototype will help to monitor the structural health of billions of dollars’ worth of infrastructure, reducing repair bills and minimising potentially catastrophic failures.

Road, bridge and pipeline infrastructure is vulnerable to flooding, soil erosion, and even ground shifts due to earthquakes. Some water and gas pipelines in Australia are over a century old and failures are all too common. Jakarta’s water supply system requires major upgrading and suffers a high percentage of water losses due to leakage.

An Australia-Indonesia Centre research team led by Professor Jayantha Kodikara of Monash University, with the support of Dr Hera Widyastuti of Institut Teknologi Sepuluh Nopember, has developed a method of using fibre optic sensors to more efficiently monitor various potential failures.

“One of the challenges with infrastructure is that it is large and long” explains a member of the research team Dr Leslie Wong from Monash University. “Optic fibre sensors offer distributed sensing capability which makes them able to monitor kilometres of pipes or tunnels.”

Dr Wong summarised how the technology works: “We send a light pulse into a string of fibres [which has its] own imperfections, because it’s made of glass, so some light is reflected back. The intensity of that reflected light can be translated into information on strain and temperature. If a section is getting strained the pattern of the light reflected back will be different.”

Cracks appears in a reinforced concrete bridge. (Credit: AIC)

The prototype has already been tested extensively in the laboratory and in the field and has drawn the attention of potential industry partners.

There are more than 33,000 road bridges in Australia, about 10,000 of which are managed by state road authorities. A 2002 estimate revealed the high cost of maintaining this crucial infrastructure as it ages. Annual maintenance cost are upwards of AUD$100 million, and the replacement value of all of these bridges is estimated at over AUD$16 billion.

Currently, infrastructure monitoring includes routine maintenance and visual inspections. Robust sensors that can withstand moving water and water pressure and the long-term effects of corrosion increase the accuracy, ease and cost efficiency of this process.

Fibre optic sensors are glass fibres and are not vulnerable to corrosion, like traditional strain gauges.

This sophisticated sensor technology will allow civic maintenance organisations to more accurately assess the lifespan of materials and analyse their integrity after natural disasters. The sensors can even be built into critical road sections and pipelines for constant monitoring to catch issues as they arise, instead of waiting for visible damage to appear or more destructive failures to occur.

Accurate, timely monitoring of this infrastructure promises not only cost savings, but also improved public safety by reducing incidents.