News
05.12.2010
Beamed Up
Lightweight hybrid spans are bridge to the future
A bridge constructed over a creek from hybrid composite beams.
Courtesy HCB

At a recent awards ceremony, structural engineer John Hillman joked that the first Google result for the acronym HCB is “Holy cow, Batman.” But that may not be the case for long. Hillman’s invention, the hybrid composite beam (HCB), aims to change the way short structural spans are built, offering new possibilities for civil and marine infrastructure.


The underside of an HCB Bridge. (Click to zoom)
 

The 2,000-pound HCBs span up to 70 feet, and are light enough to be installed with a large backhoe, yet strong enough to support a loaded freight train. The beams work like prestressed concrete or steel beams, but are made of a self-consolidating concrete arch and steel strands surrounded by a fiberglass reinforced polymer shell, which makes the beam waterproof and protects it from corrosion.

After 14 years of research and development, Hillman, whose day job is with Chicago-based Teng & Associates, has installed his first permanent spans in Long Creek, IL, and on Route 23 in Cedar Grove, NJ. Innovative Bridge Research and Development (IBRD) program grants from the Federal Highway Administration funded both projects. Now the beams are about to be used in the longest structure thus far, the 540-foot-long, eight-span Knickerbocker Bridge in Boothbay, ME, a $5.5 million project to be completed in 2012.

“The state of Maine has been very supportive,” Hillman said. Initiatives by Governor John Baldacci have increased funding to the University of Maine’s Advanced Structures and Composites Center, where Hillman worked with researchers to test HCB prototypes. The only license for U.S. manufacture is held by Maine-based Harbor Technologies.

Hillman said gaining this type of regional acceptance is key to helping the technology take root. “We wanted to get a foothold in the U.S. and work through any manufacturing bugs,” he said. The HCB technology already has a manufacturing licensee for Canada and the European Union, with patents pending around the world. The Knickerbocker Bridge and future projects are expected to have an upfront cost on par with traditional structures, but lower installation costs. An anticipated 100-year lifetime would increase long-term savings.

Workers installing an HCB.

Though the lightweight beams could change the way countless structures are built, HCB designs don’t differ significantly from standard structures. “We always understood that our new technology has to be compatible with existing technology,” said Hillman. This potential, coupled with the beams’ easy installation, could make them practical for use in developing countries, as well as a viable solution to the estimated 160,000 aging bridges in the U.S. 

Among other new uses for HCBs, Hillman is now advancing them as green roof technology. For a major Chicago project, he hopes to replace the building’s roof using HCBs for the same cost as a traditional replacement, but with 20 times the load-carrying capacity and built-in waterproofing.

“Our industry is slow to adapt to change,” he said. “It’s common knowledge that it takes about 18 years to adopt a new technology. I’ve been at it about 14 years, so it’s almost time to succeed.”

Jennifer K. Gorsche