BUFFALO, N.Y. — Rust is a civil engineer’s
Motorists in the United States make more than 200 million trips
across bridges rated structurally deficient or in need of
significant maintenance and yearly inspection. Of the more than
17,000 bridges in New York, 12.5 percent are structurally deficient
and 27 percent are considered functionally obsolete.
One major culprit: corrosion of reinforcing steel.
Now, however, University at Buffalo researchers believe they can
detect corrosion before the damage becomes severe by sending a jolt
of electricity between opposite ends of steel cables. A reduction
in the strength of the charge would alert them that the cable is
suffering from corrosion and the bridge is in danger of
The new technique could do away with time-consuming and
expensive visual tests, which often rely on drilling through
concrete to inspect the cables or spotting cracks in the concrete
caused by increased stress on the weakened wires.
“The No. 1 priority of all civil engineers is the safety
of the public,” says Tresor Mavinga, a UB senior civil
engineering and mathematics major involved in the research.
“Corrosion can affect any structure, not just bridges, and we
don’t want that to happen. We need to be as accurate as
possible to save money, time and lives.”
Led by Salvatore Salamone, PhD, assistant professor of civil
engineering, Mavinga and Alireza Farhidzadeh, a civil engineering
graduate student, embedded piezoelectric transducers —
devices that convert a signal from one form of energy to another
— onto each end of a wire.
They then fired one volt of electricity through the metal using
ultrasonic guided waves, which can travel a long distance with
little loss in energy, while monitoring the charge received at each
end. The experiment was then repeated with the same wire after it
was rusted with a saltwater mixture. When cables are corroded, most
of the energy from the electrical charge will be lost during the
transfer between transducers.
Since the sensors and transducers are permanently attached to
the cable, engineers can test the wires remotely off-site.
According to the Federal Highway Administration, corrosion
problems have increased significantly over the last three decades
and are likely to continue. The increase is in part due to the
rising use of road de-icing salts, which are extremely corrosive to
the protective films on metals.
Improved testing is a needed step toward the improvement of
U.S. bridges were graded a C-plus by the American Society of
Civil Engineers in its 2013 Report Card for America’s
The report adds that one out of nine of the nation’s
bridges is structurally deficient and that more than 30 percent of
bridges have exceeded their 50-year design life; the average age of
the nation’s bridges is currently 42 years.