A civil engineering research team at the University of Missouri-Rolla (UMR, Rolla, Missouri / USA; www.umr.edu) is assessing the use of composite fibre-reinforced polymer (FRP) technology to extend the life of bridges. The team is treating five decaying bridges in rural Missouri with a corrosion-resistant “bandage”, in which strips of the composite materials combining the strength of aramid, carbon and glass fibres with the stability of the polymer resins are wrapped around pillars or “wallpapered” on lengths of concrete to strengthen the original structure.

To back claims for the use of the technology, Antonio Nanni of UMR said that in 2000 when it installed a fully composite bridge on the UMR campus, the university had “demonstrated that a bridge can be built with off-the-shelf FRP tubes readily available from the pultrusion (or composite materials) industry.” According to the researchers, the composites also can be fashioned into reinforcement bars and inserted into concrete structures or soil before being covered with a sheet of polymer to strengthen the bridge bed.

“This technology is ideal for strengthening and repair, and almost unmatchable for seismic upgrade,” Nanni said. But he believes the “greatest opportunity” in the replacement of conventional materials for new construction. Four different FRP technologies, as well as steel-reinforced polymer, are being employed at UMR to test the structures over a number of years and assess whether composites can provide a long-term solution. This could be a tremendous boost to the composites industry, as 28% of the bridges in Missouri are reported to be in poor condition, mainly due to the use of de-icing salt, and hundreds of thousands of bridges in the US are said to be nearing the end of their design lives.