By European Plastics News staff
A polyurethane application has won a 2011 Canadian Institute of Steel Construction (CISC) award for innovative use of steel in the province of Alberta, Canada. The award went to the Dialog consultancy and Empire Iron Works for the PU sandwich technique used to renovate a 100-year old, five-span, riveted steel through-truss bridge.
The 236-m long, 8-m wide Dawson Bridge in Edmonton carries 17 000 vehicles a day across the North Saskatchewan River and is believed to be the first major bridge to have been renovated using sandwich plate system (SPS) technology.
The SPS system comprises two thin steel plates with a thicker Elastocore polyurethane core plate. The lightweight sandwich is 45mm thick.
SPS technology was developed by polyurethane producer BASF Elastogran, together with Irish Engineering group Intelligent Engineering. It is only recently that SPS has been applied to bridge construction, having been initially developed for marine and road barrier applications. More recent uses include flooring for tower blocks and stadium construction.
Kris Lima, a structural engineer with the Dialog consultancy, said: "Only a handful of bridges have been built using this technology." He added that the SPS sheet limits the "dead load" on the bridge, reducing the amount of work needed to strengthen trusses. It also eliminates on-site welding, due to a new splice plate countersunk bolt connection method.
It took six weeks to replace the deck with SPS sheets, cutting the total renovation time to 12 months from the 18 months typically needed for reinforced concrete renovation. With concrete the bridge would have been 70 percent heavier and would have required additional steel strength members.
SPS panels have also been chosen for the floor of the terrace of the 2012 Olympics Aquatics Centre in London, designed as a lightweight and easily demountable structure.