Just how trustworthy are disintegrating columns that bulge and expose bent, rusting steel on elevated highways? "They are sitting ducks that, in an earthquake, could crumble," says Professor Shamim Sheikh of the University of Toronto's Department of Civil Engineering. His team has devised a strong, cost-effective method of structural reinforcement that is already proving its worth on highways and other concrete structures around the Greater Toronto Area.
Currently, contractors repair highway columns by adding more concrete and steel to the structure. Sheikh's alternative, which uses glass or carbon fibre instead of steel, provides up to five times the strength of steel, helping structures meet and exceed the requirements of the current building codes. "It will extend the life of highways and give people precious extra seconds to get to safety during an earthquake," he says. "We think cities everywhere, particularly in earthquake zones, will benefit from this technique."
The procedure itself, which uses epoxy and a large, flexible sheet of glass or carbon fibres as the reinforcing material, is not new, Sheikh notes. However, his team is the first in North America to devise specialized retrofitting schemes for concrete structures. Sheikh and his team wrapped the materials around the highway columns and they strengthened bridge culverts with fibres - specifically, on Highways 401, 404 and the QEW - all without requiring any traffic-snarling road closures. The technique is detailed in the July 2002 issue of Engineering Structures.
Materials provided by University Of Toronto. Note: Content may be edited for style and length.
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