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Rehabilitating Bridges Carbon fiber-reinforced polymer shows promise for
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Breaking tradition isn't such a bad thing when the new practice is equivalent to the difference in pasting on wallpaper vs. repairing a wall. Such is the difference between a new material and method for repairing bridges and time-consuming, labor-intensive traditional methods.
photo by Joann Vitelli
Georgia Tech civil engineering professor Dr. Abdul-Hamid Zureick,
center, works with fiber-reinforced polymeric material suppliers
preparing material to apply to and strengthen a bridge near Atlanta.
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The new material is a high-performance, carbon
fiber-reinforced polymer, which was applied last fall to an overpass
bridge in metro Atlanta in just a matter of hours. It is one of the
first such applications of its kind in the nation. The reinforcement is
expected to strengthen and extend the life of the bridge.
The rehabilitation of the bridge is part of a Georgia Institute
of Technology research project funded by the Georgia Department of
Transportation (GDOT) in cooperation with the Federal Highway
Administration (FHWA).
The Lee Road bridge over Interstate 20 in Douglas County, Ga.,
suffers from cracks in its concrete deck. A research team led by
Dr.
Abdul-Hamid Zureick, a professor in the School of Civil and
Environmental Engineering, hopes that strips of fiber-reinforced
polymeric (FRP) material will extend the bridge's life at least five to
10 years. They are monitoring the bridge closely to gather durability
data.
"We are taking an integrated field/laboratory approach," Zureick
says. "We lack sufficient guidelines for engineers, contractors and the
GDOT regarding the use of these new materials. We need information about
safe construction procedures, GDOT design guidelines and bidding
documents. They are the keys for the success of this technology."
Indeed, a future goal of Zureick's research is to generate
national guidelines, which could be used in FRP structure repair
projects worldwide, he says. Such documentation could be in place within
two to three years.
The need for repair guidelines stems from the widespread problem
of substandard bridges — those that are structurally deficient and/or
functionally obsolete. The FHWA 1996 Better Roads Bridge Inventory
indicates that about 31 percent of the nation's bridges are substandard.
Several factors contribute to the problem. They include: aging
bridges; shorter durability because of airborne pollutants and de-icing
salts; increasing daily traffic; and insufficient repair funds.
"Traditional repair and replacement of bridge components,
including bridge decks, pile caps and pre-stressed concrete beams, is
very expensive," Zureick says. "But with high-performance,
fiber-reinforced polymeric composites technology, repairs can be made
very fast, and that cuts costs in the long term."
In fact, the Lee Road bridge repair took workers less than a day
to complete what could have taken several weeks to do traditionally,
Zureick says.
With time and money at stake for highway departments nationwide,
Zureick's research team is simultaneously conducting laboratory and
field tests on FRP materials. So far, laboratory tests have determined
that FRP materials can make bridges 30 to 40 percent stronger than the
original design. They are gathering long- term data and plan to estimate
the benefits over a bridge's lifespan once all data are analyzed.
Additional FRP material laboratory tests conducted in an
environmental chamber are addressing every potential aspect of bridge
component behavior during the structure's lifespan, expected to be 75
years under current design criteria.
Researchers are exposing components to extreme conditions,
including humidity, temperature, salt and ultraviolet light. They will
incorporate the durability data they collect into predictive models that
will estimate FRP bridge component lifespan, Zureick says.
For the full text news release,
see
www.gtri.gatech.edu/res-news/BRIDGE.html.
For more information, you may contact Dr. Abdul-Hamid Zureick,
School of Civil and Environmental
Engineering, Georgia Institute of Technology,
Atlanta, GA, 30332-0355. (Telephone: 404/894-2294)
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