Speeding Composite Bridge Adoption

Will the construction of a corrosion-free demonstration bridge in Maine, made from composite materials, pave the way for wider acceptance of composite bridge superstructures? That’s the goal of the U.S. Department of Transportation’s new eXceptional Bridges through Innovative Design and Groundbreaking Engineering (X-BRIDGE) initiative.

X-BRIDGE is part of the DOT’s Advanced Research Projects Agency – Infrastructure (ARPA-I). The program focuses on creating transformative materials, designs and construction techniques to deliver bridges at half the cost, in half the time and with twice the lifespan.

There’s a dire need for better bridge technology. Around 222,000 (36%) of U.S. bridges need major repair or complete replacement, according to the American Road Transportation Builders Association. The U.S. Federal Highway Administration says that clearing that backlog would require a $125 billion investment.

We have the opportunity to use advanced composites technologies to address some of these challenges,” says Kelley Severns, X-BRIDGE project director.

X-BRIDGE’s initial three-year, $16 million project will include the design of a composite bridge system, development and prototyping of new technologies, construction of a 75-foot-long bridge, development of composite bridge specifications and standards, and analysis of the bridge’s upfront and long-term costs. The University of Maine is partnering with X-BRIDGE on this work through its Advanced Structures & Composites Center (ASCC).

“We’re going to be looking at optimal manufacturing techniques and material properties and geometric design. This will result in a system-engineered, corrosion-free, cost-efficient FRP composite superstructure,” says Severns. “We believe this concept could really change the future of bridge design, as well as manufacturing and construction in the composites industry.”  

The project team plans to incorporate several innovative technologies in the bridge design. Using basalt fiber to reinforce the deck could eliminate corrosion and reduce the amount of FRP rebar and concrete required to create a strong structure. The introduction of stay-in-place FRP arch forms beneath the deck could reduce costs.

As part of the project, private companies will partner with University of Maine on different approaches to manufacturing composite girders so the team can evaluate the strengths and weaknesses of each. “As research progresses, we could come up with a completely different shape girder that could be easier to manufacture and still have the needed properties,” says Severns.

In addition, the X-BRIDGE team will investigate the feasibility of automating the manufacture of U-shaped tub girders and using pultrusion to produce bridge beams. It may even use artificial intelligence to optimize bridge design and materials.

As the project progresses, one of X-BRIDGE’s most important tasks will be to promote adoption of composite bridge technology by State DOTs. Current barriers include its higher initial cost, DOTs and civil engineers’ unfamiliarity with composite technology and inadequate guidelines and specifications for this application of composites. (The University of Maine is currently working with the American Association of State Highway and Transportation Officials (AASHTO) Committee on Bridges and Structures to develop guidelines for the design, inspection and repair of composite girders.)

Through its work, the X-BRIDGE team will demonstrate how composite structures can save bridge owners money over the long term and will emphasize other advantages of composite bridges. “Composites are lighter, so they are easier to transport and lift. You can stack more on a truck, and you can use smaller cranes in construction,” says Severns.

Once the initial project is complete, the X-BRIDGE team hopes to continue to improve composite bridge technologies and to build more advanced prototype bridges in other states.

“We plan to work with state DOTs, the Federal Highway Administration, industry and universities to train engineers on these types of bridges. There is an implementation and commercialization plan to move this forward so that it becomes more and more mainstream,” says Severns. “The real success of X-BRIDGE is going to be measured by community acceptance and by the implementation of these corrosion-free, full composite superstructures.”