The Ohio Department of Transportation (ODOT) is turning to composites for a project to replace the Anthony Wayne Trail Bridge, a deteriorating bridge on a four-lane highway near Toledo, Ohio. Mannik & Smith Group, the design firm on the project, initially didn’t consider GFRP rebar for the structure, which spans one of Norfolk Southern Railway’s busiest rail lines. It specified epoxy-coated reinforcing steel rebar.
“It was about that time that we were introduced to Owens Corning and its GFRP reinforcing product,” recalls Richard Bertz, PE, CEO/president of Mannik & Smith. At first, the firm’s engineers were skeptical about GFRP’s ability to handle the bridge’s heavy traffic loads. But as they researched the product, they became convinced that it would not only work, but also offer many advantages.
Unlike steel rebar, GFRP rebar doesn’t rust, so the concrete deck structure doesn’t degrade as quickly, increasing the longevity of the structure. Plus, composite rebar is lighter, so it’s less expensive to deliver and faster to install.
ODOT agreed to consider using GFRP rebar for the Anthony Wayne Trail Bridge project as long as it was cost-effective. ODOT bid the project two ways – with steel and with GFRP rebar.
There were several factors that impacted the bids specifying composites. First, the GFRP design required more rebar than a conventionally-built structure. “The parameters that controlled the design were different than with conventional reinforcing steel,” Bertz explains. With steel reinforcements, the material’s bending or tensile strength controls the design; for GFRP reinforcements, either crack control or shear strength control governs the design parameters, he says.
In addition, contractors turned in higher bids for GFRP because they had no experience with the material and likely wanted to account for any possible unforeseen expenses. “They don’t know what they don’t know,” Bertz says.
When all the bids were submitted, those specifying composites were within one percent range of the project’s total $13 million cost. “From ODOT’s standpoint, that was a minimal increase for the opportunity to test this out and see how it works,” Bertz says. ODOT selected Miller Brothers Construction as the general contractor and opted to use GFRP rebar.
The bridge replacement project began last year, with completion scheduled for the fall of 2019. Owens Corning is producing the GFRP rebar. The company has worked on almost 90 GFRP-reinforced bridge projects in partnership with Hughes Brothers’ rebar division, which Owens Corning acquired in 2017. The rebar is pultruded from single-end roving fiberglass and vinyl ester resin. A finishing treatment applied to the rebar – cut in 40-, 60- and 80-foot lengths – helps it bond to the concrete.