Carbon fibres strengthen busy bridges

Monash University researchers are investigating a new method of repairing stressed and damaged bridges, using carbon fibre instead of steel plates.

The carbon fibre strips were successfully used last year to reinforce Melbourne's Westgate Bridge as part of a VicRoads project to strengthen the bridge's outer lanes and increase its traffic capacity.

This year, the Monash engineering experts designed similar carbon fibre reinforcement for the bridge spanning the intersection of the Monash Freeway and Warrigal Road in the Melbourne suburb of Chadstone. Monash is monitoring the results of the repairs using fibre optic monitors.

Dr Riadh Al-Mahaidi, 039905 4952 a senior lecturer in the Department of Civil Engineering, said the method involved layering woven carbon fibre fabric strips onto a concrete structure and then reinforcing it using epoxy as an adhesive and strengthening agent.

“This method of repair increases the strength of a structure such as a bridge by 30 to 80%,” Al-Mahaidi said. “It is much better than the conventional strengthening method of bolting on steel plates because it is lightweight, durable and much easier to apply.”

The worldwide increase in the use of this repair method has prompted the Monash research.

Al-Mahaidi and his research team are evaluating and improving the carbon fibre reinforcement method by testing the various types of fibres and epoxies in the university's Clayton campus laboratories.

“We test the materials using a wide variety of stressors including temperature, humidity, vibration and weight loading,” he said.

“Ageing infrastructure has prompted us to think about the need to retrofit reinforcements for bridges that are taking traffic loads today that were not envisaged when they were built,” Dr Al-Mahaidi said.

Meanwhile the Queensland government has said road freight would benefit from a $350m bridge replacement program for regional Queensland. The five-year program will replace more than 100 old bridges, many of which have low load limit. “The new bridges will have higher mass limits and will carry heavier and more efficient freight vehicles on our roads,” transport minister Paul Lucas said. The bridges would contribute to the needs for the doubling of the state's freight task that was expected in the next 10 to15 years, he said. One the first bridges repaired under the program will be the Gilbert River bridge. “It is an important transport link on the Burke Development road which provides access to the port of Karumba in the Gulf of Carpentarie,” he said.

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Carbon fibres strengthen busy bridges

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