New Methods for Building to Last

by Balfour Beatty

December 13, 2023

When building a first-of-its-kind bridge, longevity is always top of mind. On the Harkers Island Bridge Reconstruction project in Harkers Island, North Carolina, which is now open to traffic, our project team collaborated with the North Carolina Department of Transportation (NCDOT) to construct a bridge that was built to last.

As a contractor of choice for resilient and durable infrastructure, Balfour Beatty embraced the opportunity to incorporate innovative materials and methods that ensure the Harkers Island community will be able to use and enjoy the new bridge for generations to come.

Bridges of this scale are traditionally constructed with steel-reinforcing materials, but these materials are vulnerable to deterioration in the corrosive coastal environment. Steel-reinforced bridges are typically designed for a service life of approximately 75 years. On the Harkers Island project, however, the NCDOT innovatively leveraged non-corroding reinforcement materials such as carbon fiber reinforced polymer (CFRP) and glass fiber reinforced polymer (GFRP) to successfully extend the bridge’s expected lifespan to more than 100 years.

Of the more than 13,000 bridges the NCDOT manages, Harkers Island is the first to include these innovative, non-corroding materials. As our team expertly navigated the handling and installation of these materials, they have established best practices and procedures that they and the NCDOT will use into the future.

Partnering for Progress

NCDOT selected CFRP primarily for its corrosion resistance and durability. Additional benefits of the material include its light weight and high elastic modulus, making it easier to maneuver while maintaining significant strength. CFRP is comparable to the traditional steel on large bridge projects but requires less ongoing maintenance and provides a longer life span.

At Harkers Island, trusted trade partner Coastal Precast used CFRP strand in the piles and girders that were pre-cast off-site.

“Our success in using the CFRP strand would not have been possible without our expert trade partners,” says Will Janning, project engineer. “Coastal Precast had experience incorporating CFRP strand into a bridge in another state. We collaborated throughout preconstruction to ensure that the precast bridge elements precisely fit the specifications of our plan.”

The CFRP prestressed piles and girders behaved much in the same manner as traditional steel prestressed materials, so our team saw little difference while driving the piles and placing the girders.

Strength and Strategy

In lieu of traditional steel rebar, the team used GFRP rebar, which presented its own benefits and challenges. Like CFRP, GFRP is non-corrosive and has a tensile strength greater than steel. GFRP is also electrically and thermally non-conductive, chemical resistant and waterproof, making it an ideal material for the coastal North Carolina environment.

GFRP is also significantly more ergonomic than steel. GFRP rebar pieces are pre-bent and shaped, eliminating the need for teammates to bend them by hand during installation. At about a quarter of the weight of steel, GFRP also poses much less risk for musculoskeletal injuries. Protecting  people from these types of injuries has been one of our top priorities on the project, and our team even identified an opportunity to test exciting new exoskeleton technology over the course of the project.

The physical handling of the rebar required innovative Zero Harm planning, as the GFRP rebar produced skin, eye and lung irritants. In addition to the standard personal protective equipment (PPE), the team implemented additional PPE to combat irritation like respiratory protection, thicker gloves and face shields as well as verifying that any team members handling the rebar wore long sleeves and had no skin exposed.

In support of the project’s longevity and durability goals, the team also carefully evaluated the materials used to secure rebar in place. Traditionally, our team has used metal ties and bar supports, but these materials would have effectively defeated the purpose of using GFRP. Instead, the design required specialty non-corrosive ties and bar supports.

Evolving to Thrive

As the construction industry continues to innovate and evolve, clients are increasingly tapping into the expertise of contractors to advance and improve their projects. Our Harkers Island team is a shining example of Balfour Beatty’s readiness to adopt new materials and the new methods that accompany them.