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Carrying
the load
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| Scott Schiff (holding paper),
professor of civil engineering, leads
a team developing test methods
that will help South Carolina prioritize
bridge repair and replacements. |
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A team of Clemson engineers is
looking at new ways to monitor
bridge strength. The goal is to
develop a load test that will give
the state a scientific foundation
for rating bridges rather than the
inspection method used now.
“Visual inspection doesn’t always
tell the whole story,” said
Clemson civil engineering professor
Scott Schiff. He and his students
are using two types of
sensors wired to a computer to
help predict strength for an entire
bridge. Stress sensors are placed
on the bottom of beams that hold
the roadbed to measure how much
horizontal stress is created as the
beams bow under the weight of a
car or truck. The up-and-down
motion is measured with displacement
sensors, which contain
spring-loaded rods that contact the
beams. Once the sensors are in
place, the team directs a truck
across the bridge at different
speeds in different lanes. Since the
weight of the truck is known, its
effects on the sensors can be used
to figure out how the bridge will
react to real-life loads.
The state currently relies on a
bridge’s design specifications and
inspectors’ reports of visible
cracks and other signs of stress to
determine how much traffic or
weight should be allowed across.
“By creating a system for checking
individual bridges’ actual
responses to traffic loads, the
state could better prioritize repairs
and replacements,” Schiff said.
“ The sensor measurement also
could determine if a bridge is
adequate for a ‘superload,’ such as
a massive piece of manufacturing
equipment,” he said.
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