Fighting the forces of nature
When water levels rise, and bridges are at increased risk of damage or failure,
scour countermeasures and plans of action are paramount
By Jennifer Schmidt
A
n old saying states that “a person
who overlooks water under bridge
will find bridge under water.”
It’s something that Rob Ettema, a civil
engineering professor at Colorado
State University in Fort Collins, has
a vested interest in and has teamed
For engineers and scientists studying
with Ayres Associates to study for
bridge safety and stability, these words the National Cooperative Highway
ring especially true. And they serve as Research Program. Ettema and Paul
an important reminder to routinely
Clopper, Ayres’ director of applied
be mindful of bridges’ vulnerability to technology, are principal investigators
scour.
of an ongoing research project
involving contraction scour, a type of
Scour – a naturally occurring process
erosion that occurs when the flow
where flowing water removes
of a waterway’s natural channel is
sediment from around bridge piers
narrowed and picks up speed traveling
and abutments – is recognized as
through the bridge opening. Their
the No. 1 cause of bridge failures in
objective is to develop contraction
the United States. Without adequate
scour equations that will be used as
design and countermeasures in place,
future guidelines for risk-based bridge
scour can destroy infrastructure and
design in various hydraulic conditions.
undermine bridge foundations.
Ettema said bridge scour is an often
overlooked – but critically important –
issue to research and evaluate.
“The way that the water can erode the
bed level and the sides of the channel
through the bridge waterway can lead
to the instability and then failure of
the bridge’s piers and abutments,”
Ettema said. “The flow field varies
over time and is often hard to forecast,
so we need to continually develop
better insight into what happens – and
better predictive methods for bridge
design.”
Combatting crisis
Scour vulnerabilities can yield
catastrophic results, including bridge
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