May/June
2001
Internet
Watch
Building
Bridges in a High-Performance World
by
John Hooks
What's
Next? Bridges Made of Gingerbread?
Not really.
But would you believe bridges made of plastic? Yes, plastic - or more
technically correct, fiber-reinforced polymer (FRP) composite materials-
the very same type of materials you are so familiar with in fiberglass
skis and tool handles, graphite golf shafts, etc. Of course, concrete
and steel (and timber to a lesser degree) will always be the primary
bridge-building materials.
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What
is becoming increasingly obvious is that improved (i.e., high-performance)
versions of these materials are critical to the Federal Highway Administration's
goals of eliminating deficient bridges and making bridges serve longer
at a lower total (life-cycle) cost. The challenge of developing and
adapting high-performance materials to bridges is coupled with an
exciting opportunity to adapt other higher performance materials,
such as FRP composites, to economical and effective applications on
bridges. FRP composites are high in strength, low in weight, resistant
to corrosion and fatigue, and can be installed quickly. They are also
very new to bridge applications and are still experimental at this
time.
In 1998,
the Innovative Bridge Research and Construction (IBRC) Program was
established by the Transportation Equity Act for the 21st Century
(TEA-21). This six-year program provides funding to help state and
local transportation agencies use innovative materials for bridge
repair, rehabilitation, replacement, and construction.
The program
has seven goals, which include:
- Developing
new cost-effective ways to use innovative materials in highway bridge
applications.
- Developing
construction techniques to increase safety and reduce construction
time and traffic congestion.
- Reducing
the maintenance and life-cycle costs of bridges, including the costs
of new construction and the replacement or rehabilitation of deficient
bridges.
Another
important goal is to help foster the widespread use of proven applications
of these innovative materials by developing engineering design criteria
for using innovative products and materials in highway bridges and
structures.
TEA-21
authorized $108 million for the program; $6 million of the funds are
dedicated to research and technology deployment activities. It is
anticipated that $17 million will be available for construction projects
in fiscal years 2002 and 2003; the program concludes in fiscal year
2003.
Since
the program began in fiscal year 1998, 157 projects have been funded.
Projects selected for funding in the most recent year include the
use of a carefully engineered high-performance concrete (HPC) mix
design to construct a more durable bridge deck in New Jersey and the
use of high-performance steel (HPS) in the plate girders of a new
bridge in California, where the increased strength provided by HPS
will allow the bridge designers to build longer spans and eliminate
some of the piers. HPS is tougher, easier to weld, and more resistant
to corrosion than conventional steel. In a third project, FRP composite
bars were used to provide corrosion-resistant reinforcement in a bridge
deck in Vermont. The composites are more corrosion-resistant and lightweight
than conventional materials. They also can be easier to handle and
install.
Of the
157 projects funded between fiscal years 1998 and 2001, 84 used FRP,
30 involved HPC, 24 incorporated alternate rebars such as corrosion-resistant
steel and solid stainless steel, 17 used HPS, and 20 incorporated
a range of other materials. (Note some of the projects used more than
one material.)
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Candidate
projects for funding in fiscal year 2002 were solicited on March 29,2001.
The solicitation announcement, which was sent to all state departments
of transportation (DOTs) and FHWA division offices, is posted on the
Internet at http://www.fhwa.dot.gov/bridge/ibrc/.
Bridges on all public roads are eligible for IBRC funding, but applications
must be submitted through a state DOT. While funds can be requested
for both preliminary engineering and construction work, priority consideration
is given to construction work. FHWA also encourages the use of IBRC
funds to cover the costs of instrumentation and monitoring and evaluation
of the performance of the innovative materials, both during and after
construction.
Those
looking for more information on IBRC can consult the program's Web
site (http://www.fhwa.dot.gov/bridge/ibrc/).
The site features extensive information on the IBRC program, including
program criteria, a calendar of pertinent technical meetings and conferences,
experts to contact, etc. The site also features a database with details
on all of the projects that have been funded, site visitors can ask
questions or seek information from experts on bridges and high-performance
materials and can participate in an online discussion group with other
bridge engineers. Visitors to the site can also sign up for a listserv
on new bridge materials applications.
A related
Web site, to be unveiled, will provide more detailed technical information
on the more than 80 FRP projects in the IBRC database. This database
will be found at http://www.fhwa.dot.gov/bridge/frp/frpdatar.cfm
after June 30, 2001.
John
Hooks is
a structural engineer in FHWA's Office of Bridge Technology.
Other
Articles in this Issue:
5-1-1: Traffic Help May Soon Be Three Digits Away
Using
the Dynamic Modulus Test to Assess the Mix Strength of HMA
The
ITS Public Safety Program: Creating a Public Safety Coalition
Handling
the Worst Crash Ever in Virginia
Moving
Ahead - The American Public Speaks on Roadways and Transportation
in Communities
Branding America's Byways
Travelers
Seek Byway Experiences
National
Work-Zone Awareness Week Commemorated Across the Nation
Work-Zone
Traffic Control: Survey of Contracting Techniques