With over 50,000 metres of carbon fibre laminates and fabrics installed, the strengthening works commissioned by VicRoads for the Westgate Bridge in Melbourne continues to be the largest carbon fibre composite strengthened bridge anywhere in the world.
The aim of the strengthening project was to ensure the long term sustainability of the bridge to cater for current and future demands of traffic. The Westgate Bridge is one of Australia's longest and busiest bridges. Originally built to take 40,000 vehicles a day, it now carries 160,000 freight and commuter vehicles and forms a key transport link from the central business district to Melbourne's west district.
Traditionally bridges have been strengthened by reinforcing them with steel plates or jacketing sections with additional concrete that act in the same way as a splint or a cast on a broken limb. More recently, engineers have been investigating alternative bracing materials like carbon-fibre reinforced polymer (CFRP), a strong, lightweight fabric of interlocking carbon threads with up to 10 times the strength of steel, twice the stiffness, yet only one-seventh the weight.
Robin Kalfat, structural engineer for Structural Systems Limited and a PhD candidate at Swinburne University of Technology was a member of the project team responsible for developing and testing the innovative solution for the Westgate project.
“In total, nearly 40km of carbon fibre laminates of various grades and dimensions were applied to the structure along with 11,000 sq. m of carbon fibre fabric,” Kalfat said in his presentation to the 2013 TTNA Conference.
The project spawned research and development of innovative and highly efficient efficient carbon fibre reinforced plastic anchorage systems added to the carbon-fibre laminates. The simple and cheap, 25 centimetre-wide strip of carbon-fibre fabric runs across the ends of each carbon-fibre beam (like a line of super-strong sticky tape) and was found to increase the efficiency of the fibres by up to 260 per cent while reducing maintenance.
With a significant proportion of today’s civil infrastructure old and deteriorating, the ability of many structures to sustain much of the modern applied loads is becoming a challenge. The Westgate Bridge project suggests the future bodes well for advanced fibre solutions in infrastructure.