U.S. Department of Transportation
Federal Highway Administration
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Federal Highway Administration Research and Technology
Coordinating, Developing, and Delivering Highway Transportation Innovations
This magazine is an archived publication and may contain dated technical, contact, and link information.
|Publication Number: Date: May/June 2001|
Issue No: Vol. 65 No. 3
Date: May/June 2001
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.
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:
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.)
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.