Since composite rebar is significantly lighter than steel rebar, it takes fewer trucks to transport the bars (or bridge components made with composite rebar) to the jobsite. That reduces CO2 emissions. Contractors can use smaller, less costly cranes to lift composite bridge components into place, and they’re easier and safer for construction workers to handle.
FRP Bridge Innovations
State DOTs looking to assess the performance of composite materials in bridges have a wide range of old and new projects from which they can choose.
Marshall Composite Technologies used its C-BAR® rebar in 1996 to reinforce the concrete deck of Buffalo Creek Bridge in West Virginia. It was the first time FRP rebar had been used for a vehicular bridge in the U.S., and the composite deck is still performing well.
GFRP rebar is typically made through a pultrusion process that cures the material as it is pulled out of the equipment in a straight line. Marshall Composite Technologies has developed an innovative technology that skips that pultrusion curing stage.
“It allows us to go at four to five times the speed of traditional pultrusion, because we’re not limited by having to cure inside a mold,” explains Tom Ohnstad, director of engineering. “After we have formed the rebar with the ribs, we can go straight into the final oven and cure it, or we can bend it and then put it in an oven and cure it.” Moving from a continuous process to a batch process has enabled the company to provide rebar in the custom curved or bent shapes that construction projects often require.
Creative Pultrusions, part of the Creative Composites Group, used pultruded composites to build the world’s largest FRP, clear-span, pedestrian bridge during the last two years. The 152-foot long, box truss structure, part of the company’s E.T. Techtonics line, connects two sections of a 22-mile trail built on an abandoned rail bed in Bermuda.
Creative Pultrusions designed and engineered the composite structure, manufactured samples of the bridge’s unique connections and components and then sent them to the University of Miami and West Virginia University for testing. Once the design was finalized, technicians at Creative Pultrusions pultruded the bridge in sections no longer than 39 feet, since they had to fit into shipping containers for the journey to Bermuda.
Prior to shipping, the company assembled and tested the bridge on its own site to ensure it met the strength and stiffness requirements. That initial build also ensured that the crane in Bermuda could handle lifting the bridge into place. The bridge owner participated in this trial construction, which was fortunate because no one from Creative Composites Group could travel to Bermuda to oversee construction during the pandemic. Final construction of the bridge in Bermuda, which took place during December 2020, went smoothly and quickly.