Bridge System Preservation and Maintenance: Scanning for Innovation
The goal of learning more about bridge system preservation
and maintenance processes and technologies used abroad brought an international
technology scanning tour panel to Europe, Scandinavia, and Africa from March 28
to April 13, 2003. Sponsored by the American Association of State Highway and
Transportation Officials (AASHTO) and the Federal Highway Administration
(FHWA), the tour featured 10 participants representing AASHTO, FHWA, State and
local transportation agencies, and academia. Participants met with highway
agency representatives and bridge management and inspection technology
practitioners and researchers from South Africa, Switzerland, Germany, France,
Denmark, Sweden, Finland, Norway, England, and Wales. The tour also included
site visits to observe preservation techniques and new construction practices
intended to provide longer and more reliable bridge performance.
|
| The Oresund Bridge and Tunnel connects Copenhagen, Denmark, and Malmö, Sweden. |
While all of the countries visited had a smaller number of
bridges than those found in the United States, the composition (types of
materials, structural systems, and typical number and length of spans) and
average age of their bridge populations were similar. Also, nearly every country
was experiencing the same types of structure problems as are found in the
United States, including problems with construction quality control, premature
deterioration caused by corrosion, insufficient staffing and funding resources
to maintain aging bridge populations, and increasing truck volumes and loads.
Among the innovations and best practices observed was bridge
inspection frequency. The current practice in the United States is to inspect
every highway bridge at least once every 2 years (although this inspection
frequency can be increased to 4 years in some cases). In contrast, most of the
countries visited during the scanning tour base their bridge inspection
frequency interval on a risk-based approach that accounts for specific factors
such as type of structure, condition, and age. For example, Germany has defined
four levels of inspec-tion: superficial, general, major, and special.
Superficial inspections, which are primarily a visual assessment, are performed
by maintenance personnel every quarter. General inspections are performed every
3 years, while major inspections are conducted every 6 years. Special
inspections are performed as needed to assess known deficiencies or damage. In
France, the frequency and level of inspection vary with the condition of the
structures, but typically range from 3 to 9 years. The 3-year inspections are
more superficial, while indepth inspections are performed every 9 years.
"The more risk-based approach to bridge inspection frequency
we observed abroad was one of the most striking aspects of the trip to me,"
says team member Tom Everett of FHWA's Office of Bridge Technology. "The
countries we visited also tie required inspector qualifications to the
complexity of the bridge being inspected, rather than taking a one size fits
all approach." Team member Ron Young of the Alcona County Road Commission in
Michigan also found learning about the differences in bridge inspection
frequency and inspector qualifications to be one of the most valuable aspects
of the trip. "There are a wide variety of bridge types and complexities, which
were reflected in the different levels of inspection frequency and inspector
qualifications," says Young. "The trip was an excellent source of ideas. I have
since shared some of my experiences with other local highway agencies."
The scanning team has recommended conducting a study to
determine the relative risk of extending the inspection frequency for typical
bridge types in the United States and to then develop a rational method for
determining the required frequency, associated rigor, and required level of
inspector expertise for bridge inspections for different classifications of
bridges.
The team also observed that both Finland and Switzerland are
developing corridor-based bridge management systems. Finland is developing a
network-level management system known as "Hibris," which will be capable of
analyzing and evaluating bridge and pavement needs in an integrated
environment. Performance and planning indicators, including a repair index and
a rehabilitation index, are being designed for the system. Switzerland,
meanwhile, has designed a system that will provide management tools for
maintaining highway assets, including pavements, structures, and
electromechanical systems. In contrast, most bridge management systems in the
United States currently operate independent of other highway asset management
systems. Recognizing the value in a corridor-based management approach, the
scanning team has recommended that a study be initiated to evaluate and promote
corridor-based management principles for bridge preservation and project
decisions.
Another practice of particular interest to the scanning team
was the use of bridge deck protective strategies, as bridge deck deterioration
is one of the most costly aspects of maintaining this country's bridge
inventory. Many European countries rely heavily on the use of waterproofing
systems and membranes to provide protection for concrete bridge decks in order
to retard and prevent deterioration. Typically, the membrane is then protected
with a concrete or asphalt wearing surface. However, the primary practice in
the United States has been to use other deck protection strategies, such as
epoxy coated reinforcing steel and thicker concrete cover requirements, rather
than waterproofing and membrane systems. The team has therefore recommended
that a study be done to review U.S. and European practices and to compare the
effectiveness of waterproofing and membrane systems to other deck protection
approaches currently in use in the United States.
The team noted that several countries are making advances in
concrete permeability evaluation technology. Switzerland, for example, has
developed a vacuum-based method that pulls air through pores in the concrete
member. As other countries, including the United States, are also conducting
research and development studies on permeability testing, the scan team
recommends that a more focused study be conducted to collect and assess
information from a number of countries.
For more information on the scanning tour, contact George
Romack at FHWA, 202-366-4606 (email:
george.romack@fhwa.dot.gov), or Ken Hurst at the Kansas Department of
Transportation, 785-296-3761 (email: kenh@ksdot.org). A scan report is expected
to be released later this year.
..................................................
