Build it, but make sure you fix it
University of Georgia
Morry Gash/AP
Current national strategies for bridge maintenance favor replacement over maintenance.
A fairly simple depreciation formula is used, resulting in overly conservative assessments of a bridge's long-term health.
In a study published in the American Society of Civil Engineers' Journal of Performance of Constructed Facilities, researchers from UGA's College of Engineering propose a new model for the first time.
This new approach considers the
interaction of 60 to 80 bridge components in predicting long-term bridge
performance and focuses on maintenance instead of replacement.
"Rather than considering a bridge as a monolithic structure, the bridge coactive model assesses a bridge as a system in which changes in the condition of each coactive element not only directly affects the overall bridge performance but indirectly influences the performance of the other dependent elements," said Brian Oyegbile, one of the study's authors.
Oyegbile
earned his Ph.D. in engineering from UGA in 2020 and now works with the
California Department of Transportation.
As an example, Oyegbile says replacing a damaged bridge expansion joint is inexpensive and has marginal impact on the overall performance of the bridge in the short term. However, salt from de-icing or contaminated water can seep through a damaged expansion joint over time, accelerating the deterioration of more critical elements below, such as a column.
Likewise, a bridge deck may
deteriorate more quickly when debris accumulates in an expansion joint and
restricts the normal expansion and contraction of the deck.
According to the UGA researchers, proactively replacing elements at the right time -- even one as small as an expansion joint -- can have a big impact on long-term bridge health. They say their model can provide stronger data and more accurate depreciation predictions for state transportation agencies as they schedule bridge maintenance, repair and replacement.
Nationally, bridges last an average
of 75 years. With timely and efficient application of available resources, the
researchers say these bridges can serve for more than 100 years.
"In
my eyes, the co-activeness is apparent in the bridge inspection data and we can
scientifically leverage data analytics in bridge service-life predictions,
saving money for the country's infrastructure maintenance and
construction," said Oyegbile.
Regular
upkeep would save money
Stephan
Durham, a professor in the College of Engineering and one of the study's
co-authors, says your home's heating and cooling system serves as a good
analogy.
"Like
clockwork, I replace my air filters every two months whether the system has
been in heavy use or not because it keeps the system operating
efficiently," he said. "It's the same thing with a bridge. If you're
replacing an expansion joint on a regular basis, whether it's completely worn
out or not, your bridge is going to perform better than if you let it degrade
to the point a component absolutely must be replaced."
The
researchers analyzed data in the Federal Highway Administration's National
Bridge Inventory for Alabama, Florida and Georgia to build and test their
model. Georgia alone has more than 15,000 bridges. The NBI database includes
inspection reports on individual bridge elements, proving a wealth of
information for the researchers.
"Prior
to our work, we hadn't seen a mathematical model that considers the interaction
between bridge elements," said Mi Geum Chorzepa, an associate professor
and the study's principal investigator. "We need a more realistic way to
assess bridge conditions and prioritize preventive maintenance, particularly in
such a challenging budget environment."
The
researchers estimate a $10 billion investment in timely and appropriate
preventive maintenance on the nation's bridges over three years would generate
$20 billion in recurring savings by 2024. Those savings could be devoted
elsewhere, such as new infrastructure construction, and help drive economic
growth, according to the team.
The
Georgia Department of Transportation, which funded the study, recently approved
a grant for the researchers to expand their work. In the second phase of the
project, the team will work with GDOT's Offices of Transportation Data,
Research, and Bridge Maintenance to develop a bridge life-cycle assessment tool
for use by GDOT and county governments across the state.
The
research team also includes S. Sonny Kim, an associate professor in the College
of Engineering.