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NSF PR 95-69 - October 10, 1995
Media contact: |
George Chartier |
(703) 306-1070 |
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People Who Drive on Glass Bridges...
Very soon, bridges will be made of glass. And plastic.
And carbon.
Scientists and engineers around the world are working
on a new generation of construction materials for
bridges that will resist corrosion and last longer
with less need for repair. Canada, China, Japan and
Scotland are among nations that have built or are
about to build bridges using polymer composites. In
the near future, the suspension cables, support girders
and main deck of many bridges will be made of millions
of braided, woven and fused strands of composite materials
cooked up in laboratories by engineers. There's an
international race to develop these materials because
bridges everywhere are crumbling from the effects
of weather, pollution and age, says John Scalzi, a
structural engineer who directs the National Science
Foundation (NSF)'s Large Structural and Building Systems
Program. Scalzi says the United States, which has
lagged dangerously behind, urgently needs to catch
up with advances in construction materials achieved
in other countries for at least two reasons: First,
he says, the civil infrastructure in the U.S. is in
bad shape. The Federal Highway Commission reports
that 42 percent of bridges need repair and are obsolete;
the cumulative repair bill by the year 2010 is estimated
to reach $50 billion. New, low-maintenance materials
are needed immediately to repair a long list of existing
bridges in every state of the union. Second, on the
global scale, the nations with the most advanced design
and manufacturing programs will dominate the world
export market for the new polymer materials. On Scalzi's
desk lies a stack of 18-inch rods in various colors
and shapes. They are samples of new building materials
under development in university laboratories through
projects underwritten by NSF grants. If the rods were
made of standard metal alloys, they would weigh twice
as much. Multiplied by miles of rods and cables that
go into a two-to-four-lane bridge, the weight reduction
means a significant contribution to the long life
of a structure. Also, metal rods imbedded in concrete
for reinforcement age and corrode over time from exposure
to the acidic concrete and moisture collecting in
the cracks, whereas plastic and glass fiber rods are
expected to last 10 to 100 times longer without maintenance.
The current research in polymer composite materials
grew out of earlier aerospace efforts to find radar-evading
"stealth" materials, says Scalzi, "which is a perfect
example of military research spinning off into unforeseen
civilian uses." He says continued research into new
uses for these polymers will not only lead to better
bridges, roads and buildings, but along the way provide
new, diversified commercial ventures for the struggling
aerospace firms that first developed these materials.
Nearly 40 laboratories across the U.S. are developing
and testing these new materials through programs underwritten
by NSF. They include:
- California State University at Long Beach: developed
synthetic cables to be installed on a suspension
bridge, and composite materials for a deck on
another bridge. Contact: Joseph Plecnick, professor
of civil engineering (310) 9854406.
- Catholic University (Washington, D.C.): preparing
to monitor and evaluate a new grid system it developed
for a full scale bridge deck to be constructed
in Washington, D.C., in 1996, using new fiber-reinforced
plastic materials. Contact: Lawrence Bank, professor
of civil engineering (202) 319-4381.
- Lawrence Technological Institute (Southfield,
Mich.): studying the use of glass and carbon fibers
for an experimental bridge design. Contact: Nabil
F. Grace, professor of civil engineering (810)
204-2556.
- Pennsylvania State University: testing the durability
and structural effects of novel polymer sheets
used to reinforce damaged concrete beams. Contact:
Antonio Nanni, associate professor of architectural
engineering (814) 863- 2084.
- University of Arizona: developing techniques
to strengthen masonry walls and concrete columns
with carbon laminates. Contact: Hamid Saadatmanesh
(602) 621-2148.
- University of California at San Diego: developing
techniques to strengthen highway bridge columns
by using carbon laminates to resist earthquake
forces. Contact: Frieder Seible, professor of
structural engineering (619) 534- 4640.
- West Virginia University: Construction Facilities
Center studies the durability of new composite
materials (such as fiberglass reinforced plastic
bars) and concrete under freeze- thaw environmental
conditions. Contact: Hota V.S. GangaRao, professor
of civil engineering (304) 293-7608.
Finally, here's an example of how this emerging technology
is now in use:
- E.T. Techtonics of Philadelphia, Penn., constructs
and installs pedestrian and equestrian bridges
using polymer technology especially desirable
in remote and ecologically sensitive areas such
as national parks. The technology was tested with
an NSF small business grant. Contact: G. Eric
Johansen, company president (800) 854-0957.
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