Cutting-Edge Composite Technology
AIT’s GBeam concept, patented by the University of Maine, came to be after seven years of work at the university’s Advanced Structures and Composites Center. Executive Director Habib Dagher said that the lab set out to research and define the next generation of girder bridges, with a focus on extending a bridge’s life cycle.
“We wanted to have a composite girder that reduces cost, life-cycle impact and carbon footprint,” Dagher said.
The aim and the final outcome was a girder solution that would be easier to fabricate, ship, install and maintain over a long period of time.
Bill Davids, head of the civil engineering department at University of Maine, said one especially important aspect of the GBeam technology is how straightforward and approachable it is for contractors.
“Whenever you introduce a new technology like this, contractors don't always jump on it because there's a fear that it’s going to be difficult to build. One of the beauties of this is it's built exactly the same way as you would build a steel girder or a concrete girder bridge,” he said.
One of the key benefits of the girders is their inclined webs, which allow for stacking and easier shipping. Dagher said three to four bridges worth of girders could fit on one flatbed truck. This can reduce transportation costs in addition to being better for the environment. A bolt system connects the girder to the deck, allowing for ease of removal and replacement and no need for a painstaking jackhammering process.
The composite material also makes the girders especially corrosion-resistant, which was a great fit for the Grist Mill Bridge due to the high level of salt the structure is exposed to as it stands over the brackish Souadabscook Stream.
The light weight of the girders is also a considerable benefit. Emmons said the lightweight quality allowed for more ease in moving the beams around on the job. Because the composite material was so light compared to steel or concrete, workers were able to safely and securely mount and suspend water utility pipes under the bridge from a pair of girders and fly them as one unit from a crane. This was much safer for the workers and also more efficient, he said.
“A lot of our time-saving activities once we got to the superstructure were absolutely governed by the weight of the girders themselves and the ability to do more things at once,” Emmons said.
Frankhauser adds that the longevity and low-maintenance requirement of this solution translates to cost savings for taxpayers along with increased safety with less need for disruptive road closures. “Anytime we can have something that lasts longer and requires less work through its life, that certainly is going to benefit the public,” Frankhauser said.
