International bridges built to handle traffic for the long haul

Bridges Case Studies
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Brisbane’s Gateway Bridge in Australia was the largest road and bridge project in Queensland’s history, necessary to meet the region’s future highway demands. The bridge was delivered by Queensland Motorways with design and construction by the Leighton Abigroup Joint Venture. Specifications for the bridge called for a design life of 300 years. To ensure such longevity, the bridge designers specified stainless steel reinforcement bar in the pile caps located in the splash zones of the two main river pylons of the Brisbane River. Positioned in the most corrosive environment of the structure, a 150-mm-thick stainless steel reinforced cover was formed around the structural steel prior to casting of the concrete.

 

“Construction of this cover plays a key role in reaching the 300-year design-life specification,” noted Gerry van der Wal, Alliance and Construction Manager. “The main span pile caps were the only area requiring use of stainless reinforcement steel,” he added.

 

Leighton Abigroup Joint Venture initially approached Outokumpu, a producer of stainless steel, about the austenitic grade 316L for rebar. Outokumpu presented the benefits of its lean duplex, LDX 2101: corrosion resistance close to that of 316L, but with lower nickel content which can offer good price stability. “At the time, LDX 2101 was relatively new to the market,” explained Tom Holsing, product manager, Rebar & Wire Rod, for Outokumpu in the Americas. “Outokumpu worked with ArupMaterialsConsulting to publish the results of Outokumpu research showing predictive models in specifying selective use of LDX 2101 stainless rebar,” he indicated. The report, published in 2009, is available on Outokumpu’s website. “The results of the predictive modeling report led to the specifying of LDX 2101 on the Gateway Bridge,” Holsing recalled.

 

The Gateway bridge, completed in 2011, uses more than 200 tonnes of lean duplex LDX 2101 stainless rebar, hot rolled, ribbed, in 12- and 16-mm diameters. The rebar was supplied in coil form and was straightened and cut-to-length at Atlas Specialty Metals in Melbourne. Now more than 100,000 vehicles travel the Gateway Bridge each day.

 

“The predictive modeling report was also instrumental in getting LDX 2101 stainless rebar specified for the Athabasca II Bridge in Fort McMurray, Alberta (Canada),” reported Holsing, referring to the second phase of Alberta’s largest bridge-deck project (15,500 square meters). The bridge was completed in 2011 and is part of a 10-lane bridge system spanning the Athabasca River. The bridge was designed to withstand “super-loads” on their way to the Fort McMurray oil sands. In 2012, 503 super-loads (with gross vehicle weight of 180 metric tonnes or greater) travelled across the bridge.

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